Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

85 files changed, 21465 insertions, 0 deletions

diff --git a/src/rocksdb/util/aligned_buffer.h b/src/rocksdb/util/aligned_buffer.h
new file mode 100644
index 000000000..c7b0728c9
--- /dev/null
+++ b/src/rocksdb/util/aligned_buffer.h
@@ -0,0 +1,248 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include <algorithm>
+#include "port/port.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// This file contains utilities to handle the alignment of pages and buffers.
+
+// Truncate to a multiple of page_size, which is also a page boundary. This
+// helps to figuring out the right alignment.
+// Example:
+//   TruncateToPageBoundary(5000, 4096)  => 4096
+//   TruncateToPageBoundary(10000, 4096) => 8192
+inline size_t TruncateToPageBoundary(size_t page_size, size_t s) {
+  s -= (s & (page_size - 1));
+  assert((s % page_size) == 0);
+  return s;
+}
+
+// Round up x to a multiple of y.
+// Example:
+//   Roundup(13, 5)   => 15
+//   Roundup(201, 16) => 208
+inline size_t Roundup(size_t x, size_t y) {
+  return ((x + y - 1) / y) * y;
+}
+
+// Round down x to a multiple of y.
+// Example:
+//   Rounddown(13, 5)   => 10
+//   Rounddown(201, 16) => 192
+inline size_t Rounddown(size_t x, size_t y) { return (x / y) * y; }
+
+// AlignedBuffer manages a buffer by taking alignment into consideration, and
+// aligns the buffer start and end positions. It is mainly used for direct I/O,
+// though it can be used other purposes as well.
+// It also supports expanding the managed buffer, and copying whole or part of
+// the data from old buffer into the new expanded buffer. Such a copy especially
+// helps in cases avoiding an IO to re-fetch the data from disk.
+//
+// Example:
+//   AlignedBuffer buf;
+//   buf.Alignment(alignment);
+//   buf.AllocateNewBuffer(user_requested_buf_size);
+//   ...
+//   buf.AllocateNewBuffer(2*user_requested_buf_size, /*copy_data*/ true,
+//                         copy_offset, copy_len);
+class AlignedBuffer {
+  size_t alignment_;
+  std::unique_ptr<char[]> buf_;
+  size_t capacity_;
+  size_t cursize_;
+  char* bufstart_;
+
+public:
+  AlignedBuffer()
+    : alignment_(),
+      capacity_(0),
+      cursize_(0),
+      bufstart_(nullptr) {
+  }
+
+  AlignedBuffer(AlignedBuffer&& o) ROCKSDB_NOEXCEPT {
+    *this = std::move(o);
+  }
+
+  AlignedBuffer& operator=(AlignedBuffer&& o) ROCKSDB_NOEXCEPT {
+    alignment_ = std::move(o.alignment_);
+    buf_ = std::move(o.buf_);
+    capacity_ = std::move(o.capacity_);
+    cursize_ = std::move(o.cursize_);
+    bufstart_ = std::move(o.bufstart_);
+    return *this;
+  }
+
+  AlignedBuffer(const AlignedBuffer&) = delete;
+
+  AlignedBuffer& operator=(const AlignedBuffer&) = delete;
+
+  static bool isAligned(const void* ptr, size_t alignment) {
+    return reinterpret_cast<uintptr_t>(ptr) % alignment == 0;
+  }
+
+  static bool isAligned(size_t n, size_t alignment) {
+    return n % alignment == 0;
+  }
+
+  size_t Alignment() const {
+    return alignment_;
+  }
+
+  size_t Capacity() const {
+    return capacity_;
+  }
+
+  size_t CurrentSize() const {
+    return cursize_;
+  }
+
+  const char* BufferStart() const {
+    return bufstart_;
+  }
+
+  char* BufferStart() { return bufstart_; }
+
+  void Clear() {
+    cursize_ = 0;
+  }
+
+  void Alignment(size_t alignment) {
+    assert(alignment > 0);
+    assert((alignment & (alignment - 1)) == 0);
+    alignment_ = alignment;
+  }
+
+  // Allocates a new buffer and sets the start position to the first aligned
+  // byte.
+  //
+  // requested_capacity: requested new buffer capacity. This capacity will be
+  //     rounded up based on alignment.
+  // copy_data: Copy data from old buffer to new buffer. If copy_offset and
+  //     copy_len are not passed in and the new requested capacity is bigger
+  //     than the existing buffer's capacity, the data in the exising buffer is
+  //     fully copied over to the new buffer.
+  // copy_offset: Copy data from this offset in old buffer.
+  // copy_len: Number of bytes to copy.
+  //
+  // The function does nothing if the new requested_capacity is smaller than
+  // the current buffer capacity and copy_data is true i.e. the old buffer is
+  // retained as is.
+  void AllocateNewBuffer(size_t requested_capacity, bool copy_data = false,
+                         uint64_t copy_offset = 0, size_t copy_len = 0) {
+    assert(alignment_ > 0);
+    assert((alignment_ & (alignment_ - 1)) == 0);
+
+    copy_len = copy_len > 0 ? copy_len : cursize_;
+    if (copy_data && requested_capacity < copy_len) {
+      // If we are downsizing to a capacity that is smaller than the current
+      // data in the buffer -- Ignore the request.
+      return;
+    }
+
+    size_t new_capacity = Roundup(requested_capacity, alignment_);
+    char* new_buf = new char[new_capacity + alignment_];
+    char* new_bufstart = reinterpret_cast<char*>(
+        (reinterpret_cast<uintptr_t>(new_buf) + (alignment_ - 1)) &
+        ~static_cast<uintptr_t>(alignment_ - 1));
+
+    if (copy_data) {
+      assert(bufstart_ + copy_offset + copy_len <= bufstart_ + cursize_);
+      memcpy(new_bufstart, bufstart_ + copy_offset, copy_len);
+      cursize_ = copy_len;
+    } else {
+      cursize_ = 0;
+    }
+
+    bufstart_ = new_bufstart;
+    capacity_ = new_capacity;
+    buf_.reset(new_buf);
+  }
+
+  // Append to the buffer.
+  //
+  // src         : source to copy the data from.
+  // append_size : number of bytes to copy from src.
+  // Returns the number of bytes appended.
+  //
+  // If append_size is more than the remaining buffer size only the
+  // remaining-size worth of bytes are copied.
+  size_t Append(const char* src, size_t append_size) {
+    size_t buffer_remaining = capacity_ - cursize_;
+    size_t to_copy = std::min(append_size, buffer_remaining);
+
+    if (to_copy > 0) {
+      memcpy(bufstart_ + cursize_, src, to_copy);
+      cursize_ += to_copy;
+    }
+    return to_copy;
+  }
+
+  // Read from the buffer.
+  //
+  // dest      : destination buffer to copy the data to.
+  // offset    : the buffer offset to start reading from.
+  // read_size : the number of bytes to copy from the buffer to dest.
+  // Returns the number of bytes read/copied to dest.
+  size_t Read(char* dest, size_t offset, size_t read_size) const {
+    assert(offset < cursize_);
+
+    size_t to_read = 0;
+    if(offset < cursize_) {
+      to_read = std::min(cursize_ - offset, read_size);
+    }
+    if (to_read > 0) {
+      memcpy(dest, bufstart_ + offset, to_read);
+    }
+    return to_read;
+  }
+
+  // Pad to the end of alignment with "padding"
+  void PadToAlignmentWith(int padding) {
+    size_t total_size = Roundup(cursize_, alignment_);
+    size_t pad_size = total_size - cursize_;
+
+    if (pad_size > 0) {
+      assert((pad_size + cursize_) <= capacity_);
+      memset(bufstart_ + cursize_, padding, pad_size);
+      cursize_ += pad_size;
+    }
+  }
+
+  void PadWith(size_t pad_size, int padding) {
+    assert((pad_size + cursize_) <= capacity_);
+    memset(bufstart_ + cursize_, padding, pad_size);
+    cursize_ += pad_size;
+  }
+
+  // After a partial flush move the tail to the beginning of the buffer.
+  void RefitTail(size_t tail_offset, size_t tail_size) {
+    if (tail_size > 0) {
+      memmove(bufstart_, bufstart_ + tail_offset, tail_size);
+    }
+    cursize_ = tail_size;
+  }
+
+  // Returns a place to start appending.
+  // WARNING: Note that it is possible to write past the end of the buffer if
+  // the buffer is modified without using the write APIs or encapsulation
+  // offered by AlignedBuffer. It is up to the user to guard against such
+  // errors.
+  char* Destination() {
+    return bufstart_ + cursize_;
+  }
+
+  void Size(size_t cursize) {
+    cursize_ = cursize;
+  }
+};
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/autovector.h b/src/rocksdb/util/autovector.h
new file mode 100644
index 000000000..1e6c4716b
--- /dev/null
+++ b/src/rocksdb/util/autovector.h
@@ -0,0 +1,361 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+#pragma once
+
+#include <algorithm>
+#include <cassert>
+#include <initializer_list>
+#include <iterator>
+#include <stdexcept>
+#include <vector>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+#ifdef ROCKSDB_LITE
+template <class T, size_t kSize = 8>
+class autovector : public std::vector<T> {
+  using std::vector<T>::vector;
+};
+#else
+// A vector that leverages pre-allocated stack-based array to achieve better
+// performance for array with small amount of items.
+//
+// The interface resembles that of vector, but with less features since we aim
+// to solve the problem that we have in hand, rather than implementing a
+// full-fledged generic container.
+//
+// Currently we don't support:
+//  * reserve()/shrink_to_fit()
+//     If used correctly, in most cases, people should not touch the
+//     underlying vector at all.
+//  * random insert()/erase(), please only use push_back()/pop_back().
+//  * No move/swap operations. Each autovector instance has a
+//     stack-allocated array and if we want support move/swap operations, we
+//     need to copy the arrays other than just swapping the pointers. In this
+//     case we'll just explicitly forbid these operations since they may
+//     lead users to make false assumption by thinking they are inexpensive
+//     operations.
+//
+// Naming style of public methods almost follows that of the STL's.
+template <class T, size_t kSize = 8>
+class autovector {
+ public:
+  // General STL-style container member types.
+  typedef T value_type;
+  typedef typename std::vector<T>::difference_type difference_type;
+  typedef typename std::vector<T>::size_type size_type;
+  typedef value_type& reference;
+  typedef const value_type& const_reference;
+  typedef value_type* pointer;
+  typedef const value_type* const_pointer;
+
+  // This class is the base for regular/const iterator
+  template <class TAutoVector, class TValueType>
+  class iterator_impl {
+   public:
+    // -- iterator traits
+    typedef iterator_impl<TAutoVector, TValueType> self_type;
+    typedef TValueType value_type;
+    typedef TValueType& reference;
+    typedef TValueType* pointer;
+    typedef typename TAutoVector::difference_type difference_type;
+    typedef std::random_access_iterator_tag iterator_category;
+
+    iterator_impl(TAutoVector* vect, size_t index)
+        : vect_(vect), index_(index) {};
+    iterator_impl(const iterator_impl&) = default;
+    ~iterator_impl() {}
+    iterator_impl& operator=(const iterator_impl&) = default;
+
+    // -- Advancement
+    // ++iterator
+    self_type& operator++() {
+      ++index_;
+      return *this;
+    }
+
+    // iterator++
+    self_type operator++(int) {
+      auto old = *this;
+      ++index_;
+      return old;
+    }
+
+    // --iterator
+    self_type& operator--() {
+      --index_;
+      return *this;
+    }
+
+    // iterator--
+    self_type operator--(int) {
+      auto old = *this;
+      --index_;
+      return old;
+    }
+
+    self_type operator-(difference_type len) const {
+      return self_type(vect_, index_ - len);
+    }
+
+    difference_type operator-(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ - other.index_;
+    }
+
+    self_type operator+(difference_type len) const {
+      return self_type(vect_, index_ + len);
+    }
+
+    self_type& operator+=(difference_type len) {
+      index_ += len;
+      return *this;
+    }
+
+    self_type& operator-=(difference_type len) {
+      index_ -= len;
+      return *this;
+    }
+
+    // -- Reference
+    reference operator*() const {
+      assert(vect_->size() >= index_);
+      return (*vect_)[index_];
+    }
+
+    pointer operator->() const {
+      assert(vect_->size() >= index_);
+      return &(*vect_)[index_];
+    }
+
+    reference operator[](difference_type len) const {
+      return *(*this + len);
+    }
+
+    // -- Logical Operators
+    bool operator==(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ == other.index_;
+    }
+
+    bool operator!=(const self_type& other) const { return !(*this == other); }
+
+    bool operator>(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ > other.index_;
+    }
+
+    bool operator<(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ < other.index_;
+    }
+
+    bool operator>=(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ >= other.index_;
+    }
+
+    bool operator<=(const self_type& other) const {
+      assert(vect_ == other.vect_);
+      return index_ <= other.index_;
+    }
+
+   private:
+    TAutoVector* vect_ = nullptr;
+    size_t index_ = 0;
+  };
+
+  typedef iterator_impl<autovector, value_type> iterator;
+  typedef iterator_impl<const autovector, const value_type> const_iterator;
+  typedef std::reverse_iterator<iterator> reverse_iterator;
+  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+
+  autovector() : values_(reinterpret_cast<pointer>(buf_)) {}
+
+  autovector(std::initializer_list<T> init_list)
+      : values_(reinterpret_cast<pointer>(buf_)) {
+    for (const T& item : init_list) {
+      push_back(item);
+    }
+  }
+
+  ~autovector() { clear(); }
+
+  // -- Immutable operations
+  // Indicate if all data resides in in-stack data structure.
+  bool only_in_stack() const {
+    // If no element was inserted at all, the vector's capacity will be `0`.
+    return vect_.capacity() == 0;
+  }
+
+  size_type size() const { return num_stack_items_ + vect_.size(); }
+
+  // resize does not guarantee anything about the contents of the newly
+  // available elements
+  void resize(size_type n) {
+    if (n > kSize) {
+      vect_.resize(n - kSize);
+      while (num_stack_items_ < kSize) {
+        new ((void*)(&values_[num_stack_items_++])) value_type();
+      }
+      num_stack_items_ = kSize;
+    } else {
+      vect_.clear();
+      while (num_stack_items_ < n) {
+        new ((void*)(&values_[num_stack_items_++])) value_type();
+      }
+      while (num_stack_items_ > n) {
+        values_[--num_stack_items_].~value_type();
+      }
+    }
+  }
+
+  bool empty() const { return size() == 0; }
+
+  const_reference operator[](size_type n) const {
+    assert(n < size());
+    if (n < kSize) {
+      return values_[n];
+    }
+    return vect_[n - kSize];
+  }
+
+  reference operator[](size_type n) {
+    assert(n < size());
+    if (n < kSize) {
+      return values_[n];
+    }
+    return vect_[n - kSize];
+  }
+
+  const_reference at(size_type n) const {
+    assert(n < size());
+    return (*this)[n];
+  }
+
+  reference at(size_type n) {
+    assert(n < size());
+    return (*this)[n];
+  }
+
+  reference front() {
+    assert(!empty());
+    return *begin();
+  }
+
+  const_reference front() const {
+    assert(!empty());
+    return *begin();
+  }
+
+  reference back() {
+    assert(!empty());
+    return *(end() - 1);
+  }
+
+  const_reference back() const {
+    assert(!empty());
+    return *(end() - 1);
+  }
+
+  // -- Mutable Operations
+  void push_back(T&& item) {
+    if (num_stack_items_ < kSize) {
+      new ((void*)(&values_[num_stack_items_])) value_type();
+      values_[num_stack_items_++] = std::move(item);
+    } else {
+      vect_.push_back(item);
+    }
+  }
+
+  void push_back(const T& item) {
+    if (num_stack_items_ < kSize) {
+      new ((void*)(&values_[num_stack_items_])) value_type();
+      values_[num_stack_items_++] = item;
+    } else {
+      vect_.push_back(item);
+    }
+  }
+
+  template <class... Args>
+  void emplace_back(Args&&... args) {
+    if (num_stack_items_ < kSize) {
+      new ((void*)(&values_[num_stack_items_++]))
+          value_type(std::forward<Args>(args)...);
+    } else {
+      vect_.emplace_back(std::forward<Args>(args)...);
+    }
+  }
+
+  void pop_back() {
+    assert(!empty());
+    if (!vect_.empty()) {
+      vect_.pop_back();
+    } else {
+      values_[--num_stack_items_].~value_type();
+    }
+  }
+
+  void clear() {
+    while (num_stack_items_ > 0) {
+      values_[--num_stack_items_].~value_type();
+    }
+    vect_.clear();
+  }
+
+  // -- Copy and Assignment
+  autovector& assign(const autovector& other);
+
+  autovector(const autovector& other) { assign(other); }
+
+  autovector& operator=(const autovector& other) { return assign(other); }
+
+  // -- Iterator Operations
+  iterator begin() { return iterator(this, 0); }
+
+  const_iterator begin() const { return const_iterator(this, 0); }
+
+  iterator end() { return iterator(this, this->size()); }
+
+  const_iterator end() const { return const_iterator(this, this->size()); }
+
+  reverse_iterator rbegin() { return reverse_iterator(end()); }
+
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+
+  reverse_iterator rend() { return reverse_iterator(begin()); }
+
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
+ private:
+  size_type num_stack_items_ = 0;  // current number of items
+  alignas(alignof(
+      value_type)) char buf_[kSize *
+                             sizeof(value_type)];  // the first `kSize` items
+  pointer values_;
+  // used only if there are more than `kSize` items.
+  std::vector<T> vect_;
+};
+
+template <class T, size_t kSize>
+autovector<T, kSize>& autovector<T, kSize>::assign(const autovector& other) {
+  values_ = reinterpret_cast<pointer>(buf_);
+  // copy the internal vector
+  vect_.assign(other.vect_.begin(), other.vect_.end());
+
+  // copy array
+  num_stack_items_ = other.num_stack_items_;
+  std::copy(other.values_, other.values_ + num_stack_items_, values_);
+
+  return *this;
+}
+#endif  // ROCKSDB_LITE
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/autovector_test.cc b/src/rocksdb/util/autovector_test.cc
new file mode 100644
index 000000000..adddd1b02
--- /dev/null
+++ b/src/rocksdb/util/autovector_test.cc
@@ -0,0 +1,330 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <atomic>
+#include <iostream>
+#include <string>
+#include <utility>
+
+#include "rocksdb/env.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/autovector.h"
+#include "util/string_util.h"
+
+using std::cout;
+using std::endl;
+
+namespace ROCKSDB_NAMESPACE {
+
+class AutoVectorTest : public testing::Test {};
+const unsigned long kSize = 8;
+
+namespace {
+template <class T>
+void AssertAutoVectorOnlyInStack(autovector<T, kSize>* vec, bool result) {
+#ifndef ROCKSDB_LITE
+  ASSERT_EQ(vec->only_in_stack(), result);
+#else
+  (void) vec;
+  (void) result;
+#endif  // !ROCKSDB_LITE
+}
+}  // namespace
+
+TEST_F(AutoVectorTest, PushBackAndPopBack) {
+  autovector<size_t, kSize> vec;
+  ASSERT_TRUE(vec.empty());
+  ASSERT_EQ(0ul, vec.size());
+
+  for (size_t i = 0; i < 1000 * kSize; ++i) {
+    vec.push_back(i);
+    ASSERT_TRUE(!vec.empty());
+    if (i < kSize) {
+      AssertAutoVectorOnlyInStack(&vec, true);
+    } else {
+      AssertAutoVectorOnlyInStack(&vec, false);
+    }
+    ASSERT_EQ(i + 1, vec.size());
+    ASSERT_EQ(i, vec[i]);
+    ASSERT_EQ(i, vec.at(i));
+  }
+
+  size_t size = vec.size();
+  while (size != 0) {
+    vec.pop_back();
+    // will always be in heap
+    AssertAutoVectorOnlyInStack(&vec, false);
+    ASSERT_EQ(--size, vec.size());
+  }
+
+  ASSERT_TRUE(vec.empty());
+}
+
+TEST_F(AutoVectorTest, EmplaceBack) {
+  typedef std::pair<size_t, std::string> ValType;
+  autovector<ValType, kSize> vec;
+
+  for (size_t i = 0; i < 1000 * kSize; ++i) {
+    vec.emplace_back(i, ToString(i + 123));
+    ASSERT_TRUE(!vec.empty());
+    if (i < kSize) {
+      AssertAutoVectorOnlyInStack(&vec, true);
+    } else {
+      AssertAutoVectorOnlyInStack(&vec, false);
+    }
+
+    ASSERT_EQ(i + 1, vec.size());
+    ASSERT_EQ(i, vec[i].first);
+    ASSERT_EQ(ToString(i + 123), vec[i].second);
+  }
+
+  vec.clear();
+  ASSERT_TRUE(vec.empty());
+  AssertAutoVectorOnlyInStack(&vec, false);
+}
+
+TEST_F(AutoVectorTest, Resize) {
+  autovector<size_t, kSize> vec;
+
+  vec.resize(kSize);
+  AssertAutoVectorOnlyInStack(&vec, true);
+  for (size_t i = 0; i < kSize; ++i) {
+    vec[i] = i;
+  }
+
+  vec.resize(kSize * 2);
+  AssertAutoVectorOnlyInStack(&vec, false);
+  for (size_t i = 0; i < kSize; ++i) {
+    ASSERT_EQ(vec[i], i);
+  }
+  for (size_t i = 0; i < kSize; ++i) {
+    vec[i + kSize] = i;
+  }
+
+  vec.resize(1);
+  ASSERT_EQ(1U, vec.size());
+}
+
+namespace {
+void AssertEqual(
+    const autovector<size_t, kSize>& a, const autovector<size_t, kSize>& b) {
+  ASSERT_EQ(a.size(), b.size());
+  ASSERT_EQ(a.empty(), b.empty());
+#ifndef ROCKSDB_LITE
+  ASSERT_EQ(a.only_in_stack(), b.only_in_stack());
+#endif  // !ROCKSDB_LITE
+  for (size_t i = 0; i < a.size(); ++i) {
+    ASSERT_EQ(a[i], b[i]);
+  }
+}
+}  // namespace
+
+TEST_F(AutoVectorTest, CopyAndAssignment) {
+  // Test both heap-allocated and stack-allocated cases.
+  for (auto size : { kSize / 2, kSize * 1000 }) {
+    autovector<size_t, kSize> vec;
+    for (size_t i = 0; i < size; ++i) {
+      vec.push_back(i);
+    }
+
+    {
+      autovector<size_t, kSize> other;
+      other = vec;
+      AssertEqual(other, vec);
+    }
+
+    {
+      autovector<size_t, kSize> other(vec);
+      AssertEqual(other, vec);
+    }
+  }
+}
+
+TEST_F(AutoVectorTest, Iterators) {
+  autovector<std::string, kSize> vec;
+  for (size_t i = 0; i < kSize * 1000; ++i) {
+    vec.push_back(ToString(i));
+  }
+
+  // basic operator test
+  ASSERT_EQ(vec.front(), *vec.begin());
+  ASSERT_EQ(vec.back(), *(vec.end() - 1));
+  ASSERT_TRUE(vec.begin() < vec.end());
+
+  // non-const iterator
+  size_t index = 0;
+  for (const auto& item : vec) {
+    ASSERT_EQ(vec[index++], item);
+  }
+
+  index = vec.size() - 1;
+  for (auto pos = vec.rbegin(); pos != vec.rend(); ++pos) {
+    ASSERT_EQ(vec[index--], *pos);
+  }
+
+  // const iterator
+  const auto& cvec = vec;
+  index = 0;
+  for (const auto& item : cvec) {
+    ASSERT_EQ(cvec[index++], item);
+  }
+
+  index = vec.size() - 1;
+  for (auto pos = cvec.rbegin(); pos != cvec.rend(); ++pos) {
+    ASSERT_EQ(cvec[index--], *pos);
+  }
+
+  // forward and backward
+  auto pos = vec.begin();
+  while (pos != vec.end()) {
+    auto old_val = *pos;
+    auto old = pos++;
+    // HACK: make sure -> works
+    ASSERT_TRUE(!old->empty());
+    ASSERT_EQ(old_val, *old);
+    ASSERT_TRUE(pos == vec.end() || old_val != *pos);
+  }
+
+  pos = vec.begin();
+  for (size_t i = 0; i < vec.size(); i += 2) {
+    // Cannot use ASSERT_EQ since that macro depends on iostream serialization
+    ASSERT_TRUE(pos + 2 - 2 == pos);
+    pos += 2;
+    ASSERT_TRUE(pos >= vec.begin());
+    ASSERT_TRUE(pos <= vec.end());
+
+    size_t diff = static_cast<size_t>(pos - vec.begin());
+    ASSERT_EQ(i + 2, diff);
+  }
+}
+
+namespace {
+std::vector<std::string> GetTestKeys(size_t size) {
+  std::vector<std::string> keys;
+  keys.resize(size);
+
+  int index = 0;
+  for (auto& key : keys) {
+    key = "item-" + ROCKSDB_NAMESPACE::ToString(index++);
+  }
+  return keys;
+}
+}  // namespace
+
+template <class TVector>
+void BenchmarkVectorCreationAndInsertion(
+    std::string name, size_t ops, size_t item_size,
+    const std::vector<typename TVector::value_type>& items) {
+  auto env = Env::Default();
+
+  int index = 0;
+  auto start_time = env->NowNanos();
+  auto ops_remaining = ops;
+  while(ops_remaining--) {
+    TVector v;
+    for (size_t i = 0; i < item_size; ++i) {
+      v.push_back(items[index++]);
+    }
+  }
+  auto elapsed = env->NowNanos() - start_time;
+  cout << "created " << ops << " " << name << " instances:\n\t"
+       << "each was inserted with " << item_size << " elements\n\t"
+       << "total time elapsed: " << elapsed << " (ns)" << endl;
+}
+
+template <class TVector>
+size_t BenchmarkSequenceAccess(std::string name, size_t ops, size_t elem_size) {
+  TVector v;
+  for (const auto& item : GetTestKeys(elem_size)) {
+    v.push_back(item);
+  }
+  auto env = Env::Default();
+
+  auto ops_remaining = ops;
+  auto start_time = env->NowNanos();
+  size_t total = 0;
+  while (ops_remaining--) {
+    auto end = v.end();
+    for (auto pos = v.begin(); pos != end; ++pos) {
+      total += pos->size();
+    }
+  }
+  auto elapsed = env->NowNanos() - start_time;
+  cout << "performed " << ops << " sequence access against " << name << "\n\t"
+       << "size: " << elem_size << "\n\t"
+       << "total time elapsed: " << elapsed << " (ns)" << endl;
+  // HACK avoid compiler's optimization to ignore total
+  return total;
+}
+
+// This test case only reports the performance between std::vector<std::string>
+// and autovector<std::string>. We chose string for comparison because in most
+// of our use cases we used std::vector<std::string>.
+TEST_F(AutoVectorTest, PerfBench) {
+  // We run same operations for kOps times in order to get a more fair result.
+  size_t kOps = 100000;
+
+  // Creation and insertion test
+  // Test the case when there is:
+  //  * no element inserted: internal array of std::vector may not really get
+  //    initialize.
+  //  * one element inserted: internal array of std::vector must have
+  //    initialized.
+  //  * kSize elements inserted. This shows the most time we'll spend if we
+  //    keep everything in stack.
+  //  * 2 * kSize elements inserted. The internal vector of
+  //    autovector must have been initialized.
+  cout << "=====================================================" << endl;
+  cout << "Creation and Insertion Test (value type: std::string)" << endl;
+  cout << "=====================================================" << endl;
+
+  // pre-generated unique keys
+  auto string_keys = GetTestKeys(kOps * 2 * kSize);
+  for (auto insertions : { 0ul, 1ul, kSize / 2, kSize, 2 * kSize }) {
+    BenchmarkVectorCreationAndInsertion<std::vector<std::string>>(
+        "std::vector<std::string>", kOps, insertions, string_keys);
+    BenchmarkVectorCreationAndInsertion<autovector<std::string, kSize>>(
+        "autovector<std::string>", kOps, insertions, string_keys);
+    cout << "-----------------------------------" << endl;
+  }
+
+  cout << "=====================================================" << endl;
+  cout << "Creation and Insertion Test (value type: uint64_t)" << endl;
+  cout << "=====================================================" << endl;
+
+  // pre-generated unique keys
+  std::vector<uint64_t> int_keys(kOps * 2 * kSize);
+  for (size_t i = 0; i < kOps * 2 * kSize; ++i) {
+    int_keys[i] = i;
+  }
+  for (auto insertions : { 0ul, 1ul, kSize / 2, kSize, 2 * kSize }) {
+    BenchmarkVectorCreationAndInsertion<std::vector<uint64_t>>(
+        "std::vector<uint64_t>", kOps, insertions, int_keys);
+    BenchmarkVectorCreationAndInsertion<autovector<uint64_t, kSize>>(
+      "autovector<uint64_t>", kOps, insertions, int_keys
+    );
+    cout << "-----------------------------------" << endl;
+  }
+
+  // Sequence Access Test
+  cout << "=====================================================" << endl;
+  cout << "Sequence Access Test" << endl;
+  cout << "=====================================================" << endl;
+  for (auto elem_size : { kSize / 2, kSize, 2 * kSize }) {
+    BenchmarkSequenceAccess<std::vector<std::string>>("std::vector", kOps,
+                                                      elem_size);
+    BenchmarkSequenceAccess<autovector<std::string, kSize>>("autovector", kOps,
+                                                            elem_size);
+    cout << "-----------------------------------" << endl;
+  }
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/bloom_impl.h b/src/rocksdb/util/bloom_impl.h
new file mode 100644
index 000000000..54c048485
--- /dev/null
+++ b/src/rocksdb/util/bloom_impl.h
@@ -0,0 +1,483 @@
+//  Copyright (c) 2019-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Implementation details of various Bloom filter implementations used in
+// RocksDB. (DynamicBloom is in a separate file for now because it
+// supports concurrent write.)
+
+#pragma once
+#include <stddef.h>
+#include <stdint.h>
+#include <cmath>
+
+#include "rocksdb/slice.h"
+#include "util/hash.h"
+
+#ifdef HAVE_AVX2
+#include <immintrin.h>
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+class BloomMath {
+ public:
+  // False positive rate of a standard Bloom filter, for given ratio of
+  // filter memory bits to added keys, and number of probes per operation.
+  // (The false positive rate is effectively independent of scale, assuming
+  // the implementation scales OK.)
+  static double StandardFpRate(double bits_per_key, int num_probes) {
+    // Standard very-good-estimate formula. See
+    // https://en.wikipedia.org/wiki/Bloom_filter#Probability_of_false_positives
+    return std::pow(1.0 - std::exp(-num_probes / bits_per_key), num_probes);
+  }
+
+  // False positive rate of a "blocked"/"shareded"/"cache-local" Bloom filter,
+  // for given ratio of filter memory bits to added keys, number of probes per
+  // operation (all within the given block or cache line size), and block or
+  // cache line size.
+  static double CacheLocalFpRate(double bits_per_key, int num_probes,
+                                 int cache_line_bits) {
+    double keys_per_cache_line = cache_line_bits / bits_per_key;
+    // A reasonable estimate is the average of the FP rates for one standard
+    // deviation above and below the mean bucket occupancy. See
+    // https://github.com/facebook/rocksdb/wiki/RocksDB-Bloom-Filter#the-math
+    double keys_stddev = std::sqrt(keys_per_cache_line);
+    double crowded_fp = StandardFpRate(
+        cache_line_bits / (keys_per_cache_line + keys_stddev), num_probes);
+    double uncrowded_fp = StandardFpRate(
+        cache_line_bits / (keys_per_cache_line - keys_stddev), num_probes);
+    return (crowded_fp + uncrowded_fp) / 2;
+  }
+
+  // False positive rate of querying a new item against `num_keys` items, all
+  // hashed to `fingerprint_bits` bits. (This assumes the fingerprint hashes
+  // themselves are stored losslessly. See Section 4 of
+  // http://www.ccs.neu.edu/home/pete/pub/bloom-filters-verification.pdf)
+  static double FingerprintFpRate(size_t num_keys, int fingerprint_bits) {
+    double inv_fingerprint_space = std::pow(0.5, fingerprint_bits);
+    // Base estimate assumes each key maps to a unique fingerprint.
+    // Could be > 1 in extreme cases.
+    double base_estimate = num_keys * inv_fingerprint_space;
+    // To account for potential overlap, we choose between two formulas
+    if (base_estimate > 0.0001) {
+      // A very good formula assuming we don't construct a floating point
+      // number extremely close to 1. Always produces a probability < 1.
+      return 1.0 - std::exp(-base_estimate);
+    } else {
+      // A very good formula when base_estimate is far below 1. (Subtract
+      // away the integral-approximated sum that some key has same hash as
+      // one coming before it in a list.)
+      return base_estimate - (base_estimate * base_estimate * 0.5);
+    }
+  }
+
+  // Returns the probably of either of two independent(-ish) events
+  // happening, given their probabilities. (This is useful for combining
+  // results from StandardFpRate or CacheLocalFpRate with FingerprintFpRate
+  // for a hash-efficient Bloom filter's FP rate. See Section 4 of
+  // http://www.ccs.neu.edu/home/pete/pub/bloom-filters-verification.pdf)
+  static double IndependentProbabilitySum(double rate1, double rate2) {
+    // Use formula that avoids floating point extremely close to 1 if
+    // rates are extremely small.
+    return rate1 + rate2 - (rate1 * rate2);
+  }
+};
+
+// A fast, flexible, and accurate cache-local Bloom implementation with
+// SIMD-optimized query performance (currently using AVX2 on Intel). Write
+// performance and non-SIMD read are very good, benefiting from fastrange32
+// used in place of % and single-cycle multiplication on recent processors.
+//
+// Most other SIMD Bloom implementations sacrifice flexibility and/or
+// accuracy by requiring num_probes to be a power of two and restricting
+// where each probe can occur in a cache line. This implementation sacrifices
+// SIMD-optimization for add (might still be possible, especially with AVX512)
+// in favor of allowing any num_probes, not crossing cache line boundary,
+// and accuracy close to theoretical best accuracy for a cache-local Bloom.
+// E.g. theoretical best for 10 bits/key, num_probes=6, and 512-bit bucket
+// (Intel cache line size) is 0.9535% FP rate. This implementation yields
+// about 0.957%. (Compare to LegacyLocalityBloomImpl<false> at 1.138%, or
+// about 0.951% for 1024-bit buckets, cache line size for some ARM CPUs.)
+//
+// This implementation can use a 32-bit hash (let h2 be h1 * 0x9e3779b9) or
+// a 64-bit hash (split into two uint32s). With many millions of keys, the
+// false positive rate associated with using a 32-bit hash can dominate the
+// false positive rate of the underlying filter. At 10 bits/key setting, the
+// inflection point is about 40 million keys, so 32-bit hash is a bad idea
+// with 10s of millions of keys or more.
+//
+// Despite accepting a 64-bit hash, this implementation uses 32-bit fastrange
+// to pick a cache line, which can be faster than 64-bit in some cases.
+// This only hurts accuracy as you get into 10s of GB for a single filter,
+// and accuracy abruptly breaks down at 256GB (2^32 cache lines). Switch to
+// 64-bit fastrange if you need filters so big. ;)
+//
+// Using only a 32-bit input hash within each cache line has negligible
+// impact for any reasonable cache line / bucket size, for arbitrary filter
+// size, and potentially saves intermediate data size in some cases vs.
+// tracking full 64 bits. (Even in an implementation using 64-bit arithmetic
+// to generate indices, I might do the same, as a single multiplication
+// suffices to generate a sufficiently mixed 64 bits from 32 bits.)
+//
+// This implementation is currently tied to Intel cache line size, 64 bytes ==
+// 512 bits. If there's sufficient demand for other cache line sizes, this is
+// a pretty good implementation to extend, but slight performance enhancements
+// are possible with an alternate implementation (probably not very compatible
+// with SIMD):
+// (1) Use rotation in addition to multiplication for remixing
+// (like murmur hash). (Using multiplication alone *slightly* hurts accuracy
+// because lower bits never depend on original upper bits.)
+// (2) Extract more than one bit index from each re-mix. (Only if rotation
+// or similar is part of remix, because otherwise you're making the
+// multiplication-only problem worse.)
+// (3) Re-mix full 64 bit hash, to get maximum number of bit indices per
+// re-mix.
+//
+class FastLocalBloomImpl {
+ public:
+  // NOTE: this has only been validated to enough accuracy for producing
+  // reasonable warnings / user feedback, not for making functional decisions.
+  static double EstimatedFpRate(size_t keys, size_t bytes, int num_probes,
+                                int hash_bits) {
+    return BloomMath::IndependentProbabilitySum(
+        BloomMath::CacheLocalFpRate(8.0 * bytes / keys, num_probes,
+                                    /*cache line bits*/ 512),
+        BloomMath::FingerprintFpRate(keys, hash_bits));
+  }
+
+  static inline int ChooseNumProbes(int millibits_per_key) {
+    // Since this implementation can (with AVX2) make up to 8 probes
+    // for the same cost, we pick the most accurate num_probes, based
+    // on actual tests of the implementation. Note that for higher
+    // bits/key, the best choice for cache-local Bloom can be notably
+    // smaller than standard bloom, e.g. 9 instead of 11 @ 16 b/k.
+    if (millibits_per_key <= 2080) {
+      return 1;
+    } else if (millibits_per_key <= 3580) {
+      return 2;
+    } else if (millibits_per_key <= 5100) {
+      return 3;
+    } else if (millibits_per_key <= 6640) {
+      return 4;
+    } else if (millibits_per_key <= 8300) {
+      return 5;
+    } else if (millibits_per_key <= 10070) {
+      return 6;
+    } else if (millibits_per_key <= 11720) {
+      return 7;
+    } else if (millibits_per_key <= 14001) {
+      // Would be something like <= 13800 but sacrificing *slightly* for
+      // more settings using <= 8 probes.
+      return 8;
+    } else if (millibits_per_key <= 16050) {
+      return 9;
+    } else if (millibits_per_key <= 18300) {
+      return 10;
+    } else if (millibits_per_key <= 22001) {
+      return 11;
+    } else if (millibits_per_key <= 25501) {
+      return 12;
+    } else if (millibits_per_key > 50000) {
+      // Top out at 24 probes (three sets of 8)
+      return 24;
+    } else {
+      // Roughly optimal choices for remaining range
+      // e.g.
+      // 28000 -> 12, 28001 -> 13
+      // 50000 -> 23, 50001 -> 24
+      return (millibits_per_key - 1) / 2000 - 1;
+    }
+  }
+
+  static inline void AddHash(uint32_t h1, uint32_t h2, uint32_t len_bytes,
+                             int num_probes, char *data) {
+    uint32_t bytes_to_cache_line = fastrange32(len_bytes >> 6, h1) << 6;
+    AddHashPrepared(h2, num_probes, data + bytes_to_cache_line);
+  }
+
+  static inline void AddHashPrepared(uint32_t h2, int num_probes,
+                                     char *data_at_cache_line) {
+    uint32_t h = h2;
+    for (int i = 0; i < num_probes; ++i, h *= uint32_t{0x9e3779b9}) {
+      // 9-bit address within 512 bit cache line
+      int bitpos = h >> (32 - 9);
+      data_at_cache_line[bitpos >> 3] |= (uint8_t{1} << (bitpos & 7));
+    }
+  }
+
+  static inline void PrepareHash(uint32_t h1, uint32_t len_bytes,
+                                 const char *data,
+                                 uint32_t /*out*/ *byte_offset) {
+    uint32_t bytes_to_cache_line = fastrange32(len_bytes >> 6, h1) << 6;
+    PREFETCH(data + bytes_to_cache_line, 0 /* rw */, 1 /* locality */);
+    PREFETCH(data + bytes_to_cache_line + 63, 0 /* rw */, 1 /* locality */);
+    *byte_offset = bytes_to_cache_line;
+  }
+
+  static inline bool HashMayMatch(uint32_t h1, uint32_t h2, uint32_t len_bytes,
+                                  int num_probes, const char *data) {
+    uint32_t bytes_to_cache_line = fastrange32(len_bytes >> 6, h1) << 6;
+    return HashMayMatchPrepared(h2, num_probes, data + bytes_to_cache_line);
+  }
+
+  static inline bool HashMayMatchPrepared(uint32_t h2, int num_probes,
+                                          const char *data_at_cache_line) {
+    uint32_t h = h2;
+#ifdef HAVE_AVX2
+    int rem_probes = num_probes;
+
+    // NOTE: For better performance for num_probes in {1, 2, 9, 10, 17, 18,
+    // etc.} one can insert specialized code for rem_probes <= 2, bypassing
+    // the SIMD code in those cases. There is a detectable but minor overhead
+    // applied to other values of num_probes (when not statically determined),
+    // but smoother performance curve vs. num_probes. But for now, when
+    // in doubt, don't add unnecessary code.
+
+    // Powers of 32-bit golden ratio, mod 2**32.
+    const __m256i multipliers =
+        _mm256_setr_epi32(0x00000001, 0x9e3779b9, 0xe35e67b1, 0x734297e9,
+                          0x35fbe861, 0xdeb7c719, 0x448b211, 0x3459b749);
+
+    for (;;) {
+      // Eight copies of hash
+      __m256i hash_vector = _mm256_set1_epi32(h);
+
+      // Same effect as repeated multiplication by 0x9e3779b9 thanks to
+      // associativity of multiplication.
+      hash_vector = _mm256_mullo_epi32(hash_vector, multipliers);
+
+      // Now the top 9 bits of each of the eight 32-bit values in
+      // hash_vector are bit addresses for probes within the cache line.
+      // While the platform-independent code uses byte addressing (6 bits
+      // to pick a byte + 3 bits to pick a bit within a byte), here we work
+      // with 32-bit words (4 bits to pick a word + 5 bits to pick a bit
+      // within a word) because that works well with AVX2 and is equivalent
+      // under little-endian.
+
+      // Shift each right by 28 bits to get 4-bit word addresses.
+      const __m256i word_addresses = _mm256_srli_epi32(hash_vector, 28);
+
+      // Gather 32-bit values spread over 512 bits by 4-bit address. In
+      // essence, we are dereferencing eight pointers within the cache
+      // line.
+      //
+      // Option 1: AVX2 gather (seems to be a little slow - understandable)
+      // const __m256i value_vector =
+      //     _mm256_i32gather_epi32(static_cast<const int
+      //     *>(data_at_cache_line),
+      //                            word_addresses,
+      //                            /*bytes / i32*/ 4);
+      // END Option 1
+      // Potentially unaligned as we're not *always* cache-aligned -> loadu
+      const __m256i *mm_data =
+          reinterpret_cast<const __m256i *>(data_at_cache_line);
+      __m256i lower = _mm256_loadu_si256(mm_data);
+      __m256i upper = _mm256_loadu_si256(mm_data + 1);
+      // Option 2: AVX512VL permute hack
+      // Only negligibly faster than Option 3, so not yet worth supporting
+      // const __m256i value_vector =
+      //    _mm256_permutex2var_epi32(lower, word_addresses, upper);
+      // END Option 2
+      // Option 3: AVX2 permute+blend hack
+      // Use lowest three bits to order probing values, as if all from same
+      // 256 bit piece.
+      lower = _mm256_permutevar8x32_epi32(lower, word_addresses);
+      upper = _mm256_permutevar8x32_epi32(upper, word_addresses);
+      // Just top 1 bit of address, to select between lower and upper.
+      const __m256i upper_lower_selector = _mm256_srai_epi32(hash_vector, 31);
+      // Finally: the next 8 probed 32-bit values, in probing sequence order.
+      const __m256i value_vector =
+          _mm256_blendv_epi8(lower, upper, upper_lower_selector);
+      // END Option 3
+
+      // We might not need to probe all 8, so build a mask for selecting only
+      // what we need. (The k_selector(s) could be pre-computed but that
+      // doesn't seem to make a noticeable performance difference.)
+      const __m256i zero_to_seven = _mm256_setr_epi32(0, 1, 2, 3, 4, 5, 6, 7);
+      // Subtract rem_probes from each of those constants
+      __m256i k_selector =
+          _mm256_sub_epi32(zero_to_seven, _mm256_set1_epi32(rem_probes));
+      // Negative after subtract -> use/select
+      // Keep only high bit (logical shift right each by 31).
+      k_selector = _mm256_srli_epi32(k_selector, 31);
+
+      // Strip off the 4 bit word address (shift left)
+      __m256i bit_addresses = _mm256_slli_epi32(hash_vector, 4);
+      // And keep only 5-bit (32 - 27) bit-within-32-bit-word addresses.
+      bit_addresses = _mm256_srli_epi32(bit_addresses, 27);
+      // Build a bit mask
+      const __m256i bit_mask = _mm256_sllv_epi32(k_selector, bit_addresses);
+
+      // Like ((~value_vector) & bit_mask) == 0)
+      bool match = _mm256_testc_si256(value_vector, bit_mask) != 0;
+
+      // This check first so that it's easy for branch predictor to optimize
+      // num_probes <= 8 case, making it free of unpredictable branches.
+      if (rem_probes <= 8) {
+        return match;
+      } else if (!match) {
+        return false;
+      }
+      // otherwise
+      // Need another iteration. 0xab25f4c1 == golden ratio to the 8th power
+      h *= 0xab25f4c1;
+      rem_probes -= 8;
+    }
+#else
+    for (int i = 0; i < num_probes; ++i, h *= uint32_t{0x9e3779b9}) {
+      // 9-bit address within 512 bit cache line
+      int bitpos = h >> (32 - 9);
+      if ((data_at_cache_line[bitpos >> 3] & (char(1) << (bitpos & 7))) == 0) {
+        return false;
+      }
+    }
+    return true;
+#endif
+  }
+};
+
+// A legacy Bloom filter implementation with no locality of probes (slow).
+// It uses double hashing to generate a sequence of hash values.
+// Asymptotic analysis is in [Kirsch,Mitzenmacher 2006], but known to have
+// subtle accuracy flaws for practical sizes [Dillinger,Manolios 2004].
+//
+// DO NOT REUSE
+//
+class LegacyNoLocalityBloomImpl {
+ public:
+  static inline int ChooseNumProbes(int bits_per_key) {
+    // We intentionally round down to reduce probing cost a little bit
+    int num_probes = static_cast<int>(bits_per_key * 0.69);  // 0.69 =~ ln(2)
+    if (num_probes < 1) num_probes = 1;
+    if (num_probes > 30) num_probes = 30;
+    return num_probes;
+  }
+
+  static inline void AddHash(uint32_t h, uint32_t total_bits, int num_probes,
+                             char *data) {
+    const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+    for (int i = 0; i < num_probes; i++) {
+      const uint32_t bitpos = h % total_bits;
+      data[bitpos / 8] |= (1 << (bitpos % 8));
+      h += delta;
+    }
+  }
+
+  static inline bool HashMayMatch(uint32_t h, uint32_t total_bits,
+                                  int num_probes, const char *data) {
+    const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+    for (int i = 0; i < num_probes; i++) {
+      const uint32_t bitpos = h % total_bits;
+      if ((data[bitpos / 8] & (1 << (bitpos % 8))) == 0) {
+        return false;
+      }
+      h += delta;
+    }
+    return true;
+  }
+};
+
+// A legacy Bloom filter implementation with probes local to a single
+// cache line (fast). Because SST files might be transported between
+// platforms, the cache line size is a parameter rather than hard coded.
+// (But if specified as a constant parameter, an optimizing compiler
+// should take advantage of that.)
+//
+// When ExtraRotates is false, this implementation is notably deficient in
+// accuracy. Specifically, it uses double hashing with a 1/512 chance of the
+// increment being zero (when cache line size is 512 bits). Thus, there's a
+// 1/512 chance of probing only one index, which we'd expect to incur about
+// a 1/2 * 1/512 or absolute 0.1% FP rate penalty. More detail at
+// https://github.com/facebook/rocksdb/issues/4120
+//
+// DO NOT REUSE
+//
+template <bool ExtraRotates>
+class LegacyLocalityBloomImpl {
+ private:
+  static inline uint32_t GetLine(uint32_t h, uint32_t num_lines) {
+    uint32_t offset_h = ExtraRotates ? (h >> 11) | (h << 21) : h;
+    return offset_h % num_lines;
+  }
+
+ public:
+  // NOTE: this has only been validated to enough accuracy for producing
+  // reasonable warnings / user feedback, not for making functional decisions.
+  static double EstimatedFpRate(size_t keys, size_t bytes, int num_probes) {
+    double bits_per_key = 8.0 * bytes / keys;
+    double filter_rate = BloomMath::CacheLocalFpRate(bits_per_key, num_probes,
+                                                     /*cache line bits*/ 512);
+    if (!ExtraRotates) {
+      // Good estimate of impact of flaw in index computation.
+      // Adds roughly 0.002 around 50 bits/key and 0.001 around 100 bits/key.
+      // The + 22 shifts it nicely to fit for lower bits/key.
+      filter_rate += 0.1 / (bits_per_key * 0.75 + 22);
+    } else {
+      // Not yet validated
+      assert(false);
+    }
+    // Always uses 32-bit hash
+    double fingerprint_rate = BloomMath::FingerprintFpRate(keys, 32);
+    return BloomMath::IndependentProbabilitySum(filter_rate, fingerprint_rate);
+  }
+
+  static inline void AddHash(uint32_t h, uint32_t num_lines, int num_probes,
+                             char *data, int log2_cache_line_bytes) {
+    const int log2_cache_line_bits = log2_cache_line_bytes + 3;
+
+    char *data_at_offset =
+        data + (GetLine(h, num_lines) << log2_cache_line_bytes);
+    const uint32_t delta = (h >> 17) | (h << 15);
+    for (int i = 0; i < num_probes; ++i) {
+      // Mask to bit-within-cache-line address
+      const uint32_t bitpos = h & ((1 << log2_cache_line_bits) - 1);
+      data_at_offset[bitpos / 8] |= (1 << (bitpos % 8));
+      if (ExtraRotates) {
+        h = (h >> log2_cache_line_bits) | (h << (32 - log2_cache_line_bits));
+      }
+      h += delta;
+    }
+  }
+
+  static inline void PrepareHashMayMatch(uint32_t h, uint32_t num_lines,
+                                         const char *data,
+                                         uint32_t /*out*/ *byte_offset,
+                                         int log2_cache_line_bytes) {
+    uint32_t b = GetLine(h, num_lines) << log2_cache_line_bytes;
+    PREFETCH(data + b, 0 /* rw */, 1 /* locality */);
+    PREFETCH(data + b + ((1 << log2_cache_line_bytes) - 1), 0 /* rw */,
+             1 /* locality */);
+    *byte_offset = b;
+  }
+
+  static inline bool HashMayMatch(uint32_t h, uint32_t num_lines,
+                                  int num_probes, const char *data,
+                                  int log2_cache_line_bytes) {
+    uint32_t b = GetLine(h, num_lines) << log2_cache_line_bytes;
+    return HashMayMatchPrepared(h, num_probes, data + b, log2_cache_line_bytes);
+  }
+
+  static inline bool HashMayMatchPrepared(uint32_t h, int num_probes,
+                                          const char *data_at_offset,
+                                          int log2_cache_line_bytes) {
+    const int log2_cache_line_bits = log2_cache_line_bytes + 3;
+
+    const uint32_t delta = (h >> 17) | (h << 15);
+    for (int i = 0; i < num_probes; ++i) {
+      // Mask to bit-within-cache-line address
+      const uint32_t bitpos = h & ((1 << log2_cache_line_bits) - 1);
+      if (((data_at_offset[bitpos / 8]) & (1 << (bitpos % 8))) == 0) {
+        return false;
+      }
+      if (ExtraRotates) {
+        h = (h >> log2_cache_line_bits) | (h << (32 - log2_cache_line_bits));
+      }
+      h += delta;
+    }
+    return true;
+  }
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/bloom_test.cc b/src/rocksdb/util/bloom_test.cc
new file mode 100644
index 000000000..c88d7ee32
--- /dev/null
+++ b/src/rocksdb/util/bloom_test.cc
@@ -0,0 +1,912 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef GFLAGS
+#include <cstdio>
+int main() {
+  fprintf(stderr, "Please install gflags to run this test... Skipping...\n");
+  return 0;
+}
+#else
+
+#include <array>
+#include <cmath>
+#include <vector>
+
+#include "logging/logging.h"
+#include "memory/arena.h"
+#include "rocksdb/filter_policy.h"
+#include "table/block_based/filter_policy_internal.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/gflags_compat.h"
+#include "util/hash.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+
+DEFINE_int32(bits_per_key, 10, "");
+
+namespace ROCKSDB_NAMESPACE {
+
+static const int kVerbose = 1;
+
+static Slice Key(int i, char* buffer) {
+  std::string s;
+  PutFixed32(&s, static_cast<uint32_t>(i));
+  memcpy(buffer, s.c_str(), sizeof(i));
+  return Slice(buffer, sizeof(i));
+}
+
+static int NextLength(int length) {
+  if (length < 10) {
+    length += 1;
+  } else if (length < 100) {
+    length += 10;
+  } else if (length < 1000) {
+    length += 100;
+  } else {
+    length += 1000;
+  }
+  return length;
+}
+
+class BlockBasedBloomTest : public testing::Test {
+ private:
+  std::unique_ptr<const FilterPolicy> policy_;
+  std::string filter_;
+  std::vector<std::string> keys_;
+
+ public:
+  BlockBasedBloomTest() { ResetPolicy(); }
+
+  void Reset() {
+    keys_.clear();
+    filter_.clear();
+  }
+
+  void ResetPolicy(double bits_per_key) {
+    policy_.reset(new BloomFilterPolicy(bits_per_key,
+                                        BloomFilterPolicy::kDeprecatedBlock));
+    Reset();
+  }
+
+  void ResetPolicy() { ResetPolicy(FLAGS_bits_per_key); }
+
+  void Add(const Slice& s) {
+    keys_.push_back(s.ToString());
+  }
+
+  void Build() {
+    std::vector<Slice> key_slices;
+    for (size_t i = 0; i < keys_.size(); i++) {
+      key_slices.push_back(Slice(keys_[i]));
+    }
+    filter_.clear();
+    policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
+                          &filter_);
+    keys_.clear();
+    if (kVerbose >= 2) DumpFilter();
+  }
+
+  size_t FilterSize() const {
+    return filter_.size();
+  }
+
+  Slice FilterData() const { return Slice(filter_); }
+
+  void DumpFilter() {
+    fprintf(stderr, "F(");
+    for (size_t i = 0; i+1 < filter_.size(); i++) {
+      const unsigned int c = static_cast<unsigned int>(filter_[i]);
+      for (int j = 0; j < 8; j++) {
+        fprintf(stderr, "%c", (c & (1 <<j)) ? '1' : '.');
+      }
+    }
+    fprintf(stderr, ")\n");
+  }
+
+  bool Matches(const Slice& s) {
+    if (!keys_.empty()) {
+      Build();
+    }
+    return policy_->KeyMayMatch(s, filter_);
+  }
+
+  double FalsePositiveRate() {
+    char buffer[sizeof(int)];
+    int result = 0;
+    for (int i = 0; i < 10000; i++) {
+      if (Matches(Key(i + 1000000000, buffer))) {
+        result++;
+      }
+    }
+    return result / 10000.0;
+  }
+};
+
+TEST_F(BlockBasedBloomTest, EmptyFilter) {
+  ASSERT_TRUE(! Matches("hello"));
+  ASSERT_TRUE(! Matches("world"));
+}
+
+TEST_F(BlockBasedBloomTest, Small) {
+  Add("hello");
+  Add("world");
+  ASSERT_TRUE(Matches("hello"));
+  ASSERT_TRUE(Matches("world"));
+  ASSERT_TRUE(! Matches("x"));
+  ASSERT_TRUE(! Matches("foo"));
+}
+
+TEST_F(BlockBasedBloomTest, VaryingLengths) {
+  char buffer[sizeof(int)];
+
+  // Count number of filters that significantly exceed the false positive rate
+  int mediocre_filters = 0;
+  int good_filters = 0;
+
+  for (int length = 1; length <= 10000; length = NextLength(length)) {
+    Reset();
+    for (int i = 0; i < length; i++) {
+      Add(Key(i, buffer));
+    }
+    Build();
+
+    ASSERT_LE(FilterSize(), (size_t)((length * 10 / 8) + 40)) << length;
+
+    // All added keys must match
+    for (int i = 0; i < length; i++) {
+      ASSERT_TRUE(Matches(Key(i, buffer)))
+          << "Length " << length << "; key " << i;
+    }
+
+    // Check false positive rate
+    double rate = FalsePositiveRate();
+    if (kVerbose >= 1) {
+      fprintf(stderr, "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
+              rate*100.0, length, static_cast<int>(FilterSize()));
+    }
+    ASSERT_LE(rate, 0.02);   // Must not be over 2%
+    if (rate > 0.0125) mediocre_filters++;  // Allowed, but not too often
+    else good_filters++;
+  }
+  if (kVerbose >= 1) {
+    fprintf(stderr, "Filters: %d good, %d mediocre\n",
+            good_filters, mediocre_filters);
+  }
+  ASSERT_LE(mediocre_filters, good_filters/5);
+}
+
+// Ensure the implementation doesn't accidentally change in an
+// incompatible way
+TEST_F(BlockBasedBloomTest, Schema) {
+  char buffer[sizeof(int)];
+
+  ResetPolicy(8);  // num_probes = 5
+  for (int key = 0; key < 87; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 3589896109U);
+
+  ResetPolicy(9);  // num_probes = 6
+  for (int key = 0; key < 87; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 969445585);
+
+  ResetPolicy(11);  // num_probes = 7
+  for (int key = 0; key < 87; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 1694458207);
+
+  ResetPolicy(10);  // num_probes = 6
+  for (int key = 0; key < 87; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 2373646410U);
+
+  ResetPolicy(10);
+  for (int key = /*CHANGED*/ 1; key < 87; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 1908442116);
+
+  ResetPolicy(10);
+  for (int key = 1; key < /*CHANGED*/ 88; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), 3057004015U);
+
+  // With new fractional bits_per_key, check that we are rounding to
+  // whole bits per key for old Bloom filters.
+  ResetPolicy(9.5);  // Treated as 10
+  for (int key = 1; key < 88; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), /*SAME*/ 3057004015U);
+
+  ResetPolicy(10.499);  // Treated as 10
+  for (int key = 1; key < 88; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  ASSERT_EQ(BloomHash(FilterData()), /*SAME*/ 3057004015U);
+
+  ResetPolicy();
+}
+
+// Different bits-per-byte
+
+class FullBloomTest : public testing::TestWithParam<BloomFilterPolicy::Mode> {
+ private:
+  BlockBasedTableOptions table_options_;
+  std::shared_ptr<const FilterPolicy>& policy_;
+  std::unique_ptr<FilterBitsBuilder> bits_builder_;
+  std::unique_ptr<FilterBitsReader> bits_reader_;
+  std::unique_ptr<const char[]> buf_;
+  size_t filter_size_;
+
+ public:
+  FullBloomTest() : policy_(table_options_.filter_policy), filter_size_(0) {
+    ResetPolicy();
+  }
+
+  BuiltinFilterBitsBuilder* GetBuiltinFilterBitsBuilder() {
+    // Throws on bad cast
+    return &dynamic_cast<BuiltinFilterBitsBuilder&>(*bits_builder_);
+  }
+
+  const BloomFilterPolicy* GetBloomFilterPolicy() {
+    // Throws on bad cast
+    return &dynamic_cast<const BloomFilterPolicy&>(*policy_);
+  }
+
+  void Reset() {
+    bits_builder_.reset(BloomFilterPolicy::GetBuilderFromContext(
+        FilterBuildingContext(table_options_)));
+    bits_reader_.reset(nullptr);
+    buf_.reset(nullptr);
+    filter_size_ = 0;
+  }
+
+  void ResetPolicy(double bits_per_key) {
+    policy_.reset(new BloomFilterPolicy(bits_per_key, GetParam()));
+    Reset();
+  }
+
+  void ResetPolicy() { ResetPolicy(FLAGS_bits_per_key); }
+
+  void Add(const Slice& s) {
+    bits_builder_->AddKey(s);
+  }
+
+  void OpenRaw(const Slice& s) {
+    bits_reader_.reset(policy_->GetFilterBitsReader(s));
+  }
+
+  void Build() {
+    Slice filter = bits_builder_->Finish(&buf_);
+    bits_reader_.reset(policy_->GetFilterBitsReader(filter));
+    filter_size_ = filter.size();
+  }
+
+  size_t FilterSize() const {
+    return filter_size_;
+  }
+
+  Slice FilterData() { return Slice(buf_.get(), filter_size_); }
+
+  int GetNumProbesFromFilterData() {
+    assert(filter_size_ >= 5);
+    int8_t raw_num_probes = static_cast<int8_t>(buf_.get()[filter_size_ - 5]);
+    if (raw_num_probes == -1) {  // New bloom filter marker
+      return static_cast<uint8_t>(buf_.get()[filter_size_ - 3]);
+    } else {
+      return raw_num_probes;
+    }
+  }
+
+  bool Matches(const Slice& s) {
+    if (bits_reader_ == nullptr) {
+      Build();
+    }
+    return bits_reader_->MayMatch(s);
+  }
+
+  // Provides a kind of fingerprint on the Bloom filter's
+  // behavior, for reasonbly high FP rates.
+  uint64_t PackedMatches() {
+    char buffer[sizeof(int)];
+    uint64_t result = 0;
+    for (int i = 0; i < 64; i++) {
+      if (Matches(Key(i + 12345, buffer))) {
+        result |= uint64_t{1} << i;
+      }
+    }
+    return result;
+  }
+
+  // Provides a kind of fingerprint on the Bloom filter's
+  // behavior, for lower FP rates.
+  std::string FirstFPs(int count) {
+    char buffer[sizeof(int)];
+    std::string rv;
+    int fp_count = 0;
+    for (int i = 0; i < 1000000; i++) {
+      // Pack four match booleans into each hexadecimal digit
+      if (Matches(Key(i + 1000000, buffer))) {
+        ++fp_count;
+        rv += std::to_string(i);
+        if (fp_count == count) {
+          break;
+        }
+        rv += ',';
+      }
+    }
+    return rv;
+  }
+
+  double FalsePositiveRate() {
+    char buffer[sizeof(int)];
+    int result = 0;
+    for (int i = 0; i < 10000; i++) {
+      if (Matches(Key(i + 1000000000, buffer))) {
+        result++;
+      }
+    }
+    return result / 10000.0;
+  }
+
+  uint32_t SelectByImpl(uint32_t for_legacy_bloom,
+                        uint32_t for_fast_local_bloom) {
+    switch (GetParam()) {
+      case BloomFilterPolicy::kLegacyBloom:
+        return for_legacy_bloom;
+      case BloomFilterPolicy::kFastLocalBloom:
+        return for_fast_local_bloom;
+      case BloomFilterPolicy::kDeprecatedBlock:
+      case BloomFilterPolicy::kAuto:
+          /* N/A */;
+    }
+    // otherwise
+    assert(false);
+    return 0;
+  }
+};
+
+TEST_P(FullBloomTest, FilterSize) {
+  // In addition to checking the consistency of space computation, we are
+  // checking that denoted and computed doubles are interpreted as expected
+  // as bits_per_key values.
+  bool some_computed_less_than_denoted = false;
+  // Note: enforced minimum is 1 bit per key (1000 millibits), and enforced
+  // maximum is 100 bits per key (100000 millibits).
+  for (auto bpk :
+       std::vector<std::pair<double, int> >{{-HUGE_VAL, 1000},
+                                            {-INFINITY, 1000},
+                                            {0.0, 1000},
+                                            {1.234, 1234},
+                                            {3.456, 3456},
+                                            {9.5, 9500},
+                                            {10.0, 10000},
+                                            {10.499, 10499},
+                                            {21.345, 21345},
+                                            {99.999, 99999},
+                                            {1234.0, 100000},
+                                            {HUGE_VAL, 100000},
+                                            {INFINITY, 100000},
+                                            {NAN, 100000}}) {
+    ResetPolicy(bpk.first);
+    auto bfp = GetBloomFilterPolicy();
+    EXPECT_EQ(bpk.second, bfp->GetMillibitsPerKey());
+    EXPECT_EQ((bpk.second + 500) / 1000, bfp->GetWholeBitsPerKey());
+
+    double computed = bpk.first;
+    // This transforms e.g. 9.5 -> 9.499999999999998, which we still
+    // round to 10 for whole bits per key.
+    computed += 0.5;
+    computed /= 1234567.0;
+    computed *= 1234567.0;
+    computed -= 0.5;
+    some_computed_less_than_denoted |= (computed < bpk.first);
+    ResetPolicy(computed);
+    bfp = GetBloomFilterPolicy();
+    EXPECT_EQ(bpk.second, bfp->GetMillibitsPerKey());
+    EXPECT_EQ((bpk.second + 500) / 1000, bfp->GetWholeBitsPerKey());
+
+    auto bits_builder = GetBuiltinFilterBitsBuilder();
+    for (int n = 1; n < 100; n++) {
+      auto space = bits_builder->CalculateSpace(n);
+      auto n2 = bits_builder->CalculateNumEntry(space);
+      EXPECT_GE(n2, n);
+      auto space2 = bits_builder->CalculateSpace(n2);
+      EXPECT_EQ(space, space2);
+    }
+  }
+  // Check that the compiler hasn't optimized our computation into nothing
+  EXPECT_TRUE(some_computed_less_than_denoted);
+  ResetPolicy();
+}
+
+TEST_P(FullBloomTest, FullEmptyFilter) {
+  // Empty filter is not match, at this level
+  ASSERT_TRUE(!Matches("hello"));
+  ASSERT_TRUE(!Matches("world"));
+}
+
+TEST_P(FullBloomTest, FullSmall) {
+  Add("hello");
+  Add("world");
+  ASSERT_TRUE(Matches("hello"));
+  ASSERT_TRUE(Matches("world"));
+  ASSERT_TRUE(!Matches("x"));
+  ASSERT_TRUE(!Matches("foo"));
+}
+
+TEST_P(FullBloomTest, FullVaryingLengths) {
+  char buffer[sizeof(int)];
+
+  // Count number of filters that significantly exceed the false positive rate
+  int mediocre_filters = 0;
+  int good_filters = 0;
+
+  for (int length = 1; length <= 10000; length = NextLength(length)) {
+    Reset();
+    for (int i = 0; i < length; i++) {
+      Add(Key(i, buffer));
+    }
+    Build();
+
+    ASSERT_LE(FilterSize(),
+              (size_t)((length * 10 / 8) + CACHE_LINE_SIZE * 2 + 5));
+
+    // All added keys must match
+    for (int i = 0; i < length; i++) {
+      ASSERT_TRUE(Matches(Key(i, buffer)))
+          << "Length " << length << "; key " << i;
+    }
+
+    // Check false positive rate
+    double rate = FalsePositiveRate();
+    if (kVerbose >= 1) {
+      fprintf(stderr, "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
+              rate*100.0, length, static_cast<int>(FilterSize()));
+    }
+    ASSERT_LE(rate, 0.02);   // Must not be over 2%
+    if (rate > 0.0125)
+      mediocre_filters++;  // Allowed, but not too often
+    else
+      good_filters++;
+  }
+  if (kVerbose >= 1) {
+    fprintf(stderr, "Filters: %d good, %d mediocre\n",
+            good_filters, mediocre_filters);
+  }
+  ASSERT_LE(mediocre_filters, good_filters/5);
+}
+
+namespace {
+inline uint32_t SelectByCacheLineSize(uint32_t for64, uint32_t for128,
+                                      uint32_t for256) {
+  (void)for64;
+  (void)for128;
+  (void)for256;
+#if CACHE_LINE_SIZE == 64
+  return for64;
+#elif CACHE_LINE_SIZE == 128
+  return for128;
+#elif CACHE_LINE_SIZE == 256
+  return for256;
+#else
+#error "CACHE_LINE_SIZE unknown or unrecognized"
+#endif
+}
+}  // namespace
+
+// Ensure the implementation doesn't accidentally change in an
+// incompatible way. This test doesn't check the reading side
+// (FirstFPs/PackedMatches) for LegacyBloom because it requires the
+// ability to read filters generated using other cache line sizes.
+// See RawSchema.
+TEST_P(FullBloomTest, Schema) {
+  char buffer[sizeof(int)];
+
+  // Use enough keys so that changing bits / key by 1 is guaranteed to
+  // change number of allocated cache lines. So keys > max cache line bits.
+
+  ResetPolicy(2);  // num_probes = 1
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 1);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(1567096579, 1964771444, 2659542661U),
+                   3817481309U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("11,13,17,25,29,30,35,37,45,53", FirstFPs(10));
+  }
+
+  ResetPolicy(3);  // num_probes = 2
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 2);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(2707206547U, 2571983456U, 218344685),
+                   2807269961U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("4,15,17,24,27,28,29,53,63,70", FirstFPs(10));
+  }
+
+  ResetPolicy(5);  // num_probes = 3
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 3);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(515748486, 94611728, 2436112214U),
+                   204628445));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("15,24,29,39,53,87,89,100,103,104", FirstFPs(10));
+  }
+
+  ResetPolicy(8);  // num_probes = 5
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 5);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(1302145999, 2811644657U, 756553699),
+                   355564975));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("16,60,66,126,220,238,244,256,265,287", FirstFPs(10));
+  }
+
+  ResetPolicy(9);  // num_probes = 6
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 6);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(2092755149, 661139132, 1182970461),
+                   2137566013U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("156,367,791,872,945,1015,1139,1159,1265,1435", FirstFPs(10));
+  }
+
+  ResetPolicy(11);  // num_probes = 7
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 7);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(3755609649U, 1812694762, 1449142939),
+                   2561502687U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("34,74,130,236,643,882,962,1015,1035,1110", FirstFPs(10));
+  }
+
+  // This used to be 9 probes, but 8 is a better choice for speed,
+  // especially with SIMD groups of 8 probes, with essentially no
+  // change in FP rate.
+  // FP rate @ 9 probes, old Bloom: 0.4321%
+  // FP rate @ 9 probes, new Bloom: 0.1846%
+  // FP rate @ 8 probes, new Bloom: 0.1843%
+  ResetPolicy(14);  // num_probes = 8 (new), 9 (old)
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), SelectByImpl(9, 8));
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(178861123, 379087593, 2574136516U),
+                   3709876890U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("130,240,522,565,989,2002,2526,3147,3543", FirstFPs(9));
+  }
+
+  // This used to be 11 probes, but 9 is a better choice for speed
+  // AND accuracy.
+  // FP rate @ 11 probes, old Bloom: 0.3571%
+  // FP rate @ 11 probes, new Bloom: 0.0884%
+  // FP rate @  9 probes, new Bloom: 0.0843%
+  ResetPolicy(16);  // num_probes = 9 (new), 11 (old)
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), SelectByImpl(11, 9));
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(1129406313, 3049154394U, 1727750964),
+                   1087138490));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("3299,3611,3916,6620,7822,8079,8482,8942,10167", FirstFPs(9));
+  }
+
+  ResetPolicy(10);  // num_probes = 6, but different memory ratio vs. 9
+  for (int key = 0; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 6);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(1478976371, 2910591341U, 1182970461),
+                   2498541272U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("16,126,133,422,466,472,813,1002,1035,1159", FirstFPs(10));
+  }
+
+  ResetPolicy(10);
+  for (int key = /*CHANGED*/ 1; key < 2087; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 6);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(4205696321U, 1132081253U, 2385981855U),
+                   2058382345U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("16,126,133,422,466,472,813,1002,1035,1159", FirstFPs(10));
+  }
+
+  ResetPolicy(10);
+  for (int key = 1; key < /*CHANGED*/ 2088; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 6);
+  EXPECT_EQ(
+      BloomHash(FilterData()),
+      SelectByImpl(SelectByCacheLineSize(2885052954U, 769447944, 4175124908U),
+                   23699164));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ("16,126,133,422,466,472,813,1002,1035,1159", FirstFPs(10));
+  }
+
+  // With new fractional bits_per_key, check that we are rounding to
+  // whole bits per key for old Bloom filters but fractional for
+  // new Bloom filter.
+  ResetPolicy(9.5);
+  for (int key = 1; key < 2088; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), 6);
+  EXPECT_EQ(BloomHash(FilterData()),
+            SelectByImpl(/*SAME*/ SelectByCacheLineSize(2885052954U, 769447944,
+                                                        4175124908U),
+                         /*CHANGED*/ 3166884174U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ(/*CHANGED*/ "126,156,367,444,458,791,813,976,1015,1035",
+              FirstFPs(10));
+  }
+
+  ResetPolicy(10.499);
+  for (int key = 1; key < 2088; key++) {
+    Add(Key(key, buffer));
+  }
+  Build();
+  EXPECT_EQ(GetNumProbesFromFilterData(), SelectByImpl(6, 7));
+  EXPECT_EQ(BloomHash(FilterData()),
+            SelectByImpl(/*SAME*/ SelectByCacheLineSize(2885052954U, 769447944,
+                                                        4175124908U),
+                         /*CHANGED*/ 4098502778U));
+  if (GetParam() == BloomFilterPolicy::kFastLocalBloom) {
+    EXPECT_EQ(/*CHANGED*/ "16,236,240,472,1015,1045,1111,1409,1465,1612",
+              FirstFPs(10));
+  }
+
+  ResetPolicy();
+}
+
+// A helper class for testing custom or corrupt filter bits as read by
+// built-in FilterBitsReaders.
+struct RawFilterTester {
+  // Buffer, from which we always return a tail Slice, so the
+  // last five bytes are always the metadata bytes.
+  std::array<char, 3000> data_;
+  // Points five bytes from the end
+  char* metadata_ptr_;
+
+  RawFilterTester() : metadata_ptr_(&*(data_.end() - 5)) {}
+
+  Slice ResetNoFill(uint32_t len_without_metadata, uint32_t num_lines,
+                     uint32_t num_probes) {
+    metadata_ptr_[0] = static_cast<char>(num_probes);
+    EncodeFixed32(metadata_ptr_ + 1, num_lines);
+    uint32_t len = len_without_metadata + /*metadata*/ 5;
+    assert(len <= data_.size());
+    return Slice(metadata_ptr_ - len_without_metadata, len);
+  }
+
+  Slice Reset(uint32_t len_without_metadata, uint32_t num_lines,
+               uint32_t num_probes, bool fill_ones) {
+    data_.fill(fill_ones ? 0xff : 0);
+    return ResetNoFill(len_without_metadata, num_lines, num_probes);
+  }
+
+  Slice ResetWeirdFill(uint32_t len_without_metadata, uint32_t num_lines,
+                        uint32_t num_probes) {
+    for (uint32_t i = 0; i < data_.size(); ++i) {
+      data_[i] = static_cast<char>(0x7b7b >> (i % 7));
+    }
+    return ResetNoFill(len_without_metadata, num_lines, num_probes);
+  }
+};
+
+TEST_P(FullBloomTest, RawSchema) {
+  RawFilterTester cft;
+  // Two probes, about 3/4 bits set: ~50% "FP" rate
+  // One 256-byte cache line.
+  OpenRaw(cft.ResetWeirdFill(256, 1, 2));
+  EXPECT_EQ(uint64_t{11384799501900898790U}, PackedMatches());
+
+  // Two 128-byte cache lines.
+  OpenRaw(cft.ResetWeirdFill(256, 2, 2));
+  EXPECT_EQ(uint64_t{10157853359773492589U}, PackedMatches());
+
+  // Four 64-byte cache lines.
+  OpenRaw(cft.ResetWeirdFill(256, 4, 2));
+  EXPECT_EQ(uint64_t{7123594913907464682U}, PackedMatches());
+}
+
+TEST_P(FullBloomTest, CorruptFilters) {
+  RawFilterTester cft;
+
+  for (bool fill : {false, true}) {
+    // Good filter bits - returns same as fill
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 6, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Good filter bits - returns same as fill
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE * 3, 3, 6, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Good filter bits - returns same as fill
+    // 256 is unusual but legal cache line size
+    OpenRaw(cft.Reset(256 * 3, 3, 6, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Good filter bits - returns same as fill
+    // 30 should be max num_probes
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 30, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Good filter bits - returns same as fill
+    // 1 should be min num_probes
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 1, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Type 1 trivial filter bits - returns true as if FP by zero probes
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 0, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Type 2 trivial filter bits - returns false as if built from zero keys
+    OpenRaw(cft.Reset(0, 0, 6, fill));
+    ASSERT_FALSE(Matches("hello"));
+    ASSERT_FALSE(Matches("world"));
+
+    // Type 2 trivial filter bits - returns false as if built from zero keys
+    OpenRaw(cft.Reset(0, 37, 6, fill));
+    ASSERT_FALSE(Matches("hello"));
+    ASSERT_FALSE(Matches("world"));
+
+    // Type 2 trivial filter bits - returns false as 0 size trumps 0 probes
+    OpenRaw(cft.Reset(0, 0, 0, fill));
+    ASSERT_FALSE(Matches("hello"));
+    ASSERT_FALSE(Matches("world"));
+
+    // Bad filter bits - returns true for safety
+    // No solution to 0 * x == CACHE_LINE_SIZE
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 0, 6, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Bad filter bits - returns true for safety
+    // Can't have 3 * x == 4 for integer x
+    OpenRaw(cft.Reset(4, 3, 6, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Bad filter bits - returns true for safety
+    // 97 bytes is not a power of two, so not a legal cache line size
+    OpenRaw(cft.Reset(97 * 3, 3, 6, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Bad filter bits - returns true for safety
+    // 65 bytes is not a power of two, so not a legal cache line size
+    OpenRaw(cft.Reset(65 * 3, 3, 6, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Bad filter bits - returns false as if built from zero keys
+    // < 5 bytes overall means missing even metadata
+    OpenRaw(cft.Reset(-1, 3, 6, fill));
+    ASSERT_FALSE(Matches("hello"));
+    ASSERT_FALSE(Matches("world"));
+
+    OpenRaw(cft.Reset(-5, 3, 6, fill));
+    ASSERT_FALSE(Matches("hello"));
+    ASSERT_FALSE(Matches("world"));
+
+    // Dubious filter bits - returns same as fill (for now)
+    // 31 is not a useful num_probes, nor generated by RocksDB unless directly
+    // using filter bits API without BloomFilterPolicy.
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 31, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Dubious filter bits - returns same as fill (for now)
+    // Similar, with 127, largest positive char
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 127, fill));
+    ASSERT_EQ(fill, Matches("hello"));
+    ASSERT_EQ(fill, Matches("world"));
+
+    // Dubious filter bits - returns true (for now)
+    // num_probes set to 128 / -128, lowest negative char
+    // NB: Bug in implementation interprets this as negative and has same
+    // effect as zero probes, but effectively reserves negative char values
+    // for future use.
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 128, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+
+    // Dubious filter bits - returns true (for now)
+    // Similar, with 255 / -1
+    OpenRaw(cft.Reset(CACHE_LINE_SIZE, 1, 255, fill));
+    ASSERT_TRUE(Matches("hello"));
+    ASSERT_TRUE(Matches("world"));
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(Full, FullBloomTest,
+                        testing::Values(BloomFilterPolicy::kLegacyBloom,
+                                        BloomFilterPolicy::kFastLocalBloom));
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  return RUN_ALL_TESTS();
+}
+
+#endif  // GFLAGS
diff --git a/src/rocksdb/util/build_version.cc.in b/src/rocksdb/util/build_version.cc.in
new file mode 100644
index 000000000..856958018
--- /dev/null
+++ b/src/rocksdb/util/build_version.cc.in
@@ -0,0 +1,5 @@
+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+#include "build_version.h"
+const char* rocksdb_build_git_sha = "rocksdb_build_git_sha:@@GIT_SHA@@";
+const char* rocksdb_build_git_date = "rocksdb_build_git_date:@@GIT_DATE_TIME@@";
+const char* rocksdb_build_compile_date = __DATE__;
diff --git a/src/rocksdb/util/build_version.h b/src/rocksdb/util/build_version.h
new file mode 100644
index 000000000..36ff92c07
--- /dev/null
+++ b/src/rocksdb/util/build_version.h
@@ -0,0 +1,15 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#pragma once
+#if !defined(IOS_CROSS_COMPILE)
+// if we compile with Xcode, we don't run build_detect_version, so we don't
+// generate these variables
+// this variable tells us about the git revision
+extern const char* rocksdb_build_git_sha;
+
+// Date on which the code was compiled:
+extern const char* rocksdb_build_compile_date;
+#endif
diff --git a/src/rocksdb/util/cast_util.h b/src/rocksdb/util/cast_util.h
new file mode 100644
index 000000000..d7d9a9e9c
--- /dev/null
+++ b/src/rocksdb/util/cast_util.h
@@ -0,0 +1,21 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+namespace ROCKSDB_NAMESPACE {
+// The helper function to assert the move from dynamic_cast<> to
+// static_cast<> is correct. This function is to deal with legacy code.
+// It is not recommanded to add new code to issue class casting. The preferred
+// solution is to implement the functionality without a need of casting.
+template <class DestClass, class SrcClass>
+inline DestClass* static_cast_with_check(SrcClass* x) {
+  DestClass* ret = static_cast<DestClass*>(x);
+#ifdef ROCKSDB_USE_RTTI
+  assert(ret == dynamic_cast<DestClass*>(x));
+#endif
+  return ret;
+}
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/channel.h b/src/rocksdb/util/channel.h
new file mode 100644
index 000000000..705fa2d28
--- /dev/null
+++ b/src/rocksdb/util/channel.h
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <condition_variable>
+#include <mutex>
+#include <queue>
+#include <utility>
+
+namespace ROCKSDB_NAMESPACE {
+
+template <class T>
+class channel {
+ public:
+  explicit channel() : eof_(false) {}
+
+  channel(const channel&) = delete;
+  void operator=(const channel&) = delete;
+
+  void sendEof() {
+    std::lock_guard<std::mutex> lk(lock_);
+    eof_ = true;
+    cv_.notify_all();
+  }
+
+  bool eof() {
+    std::lock_guard<std::mutex> lk(lock_);
+    return buffer_.empty() && eof_;
+  }
+
+  size_t size() const {
+    std::lock_guard<std::mutex> lk(lock_);
+    return buffer_.size();
+  }
+
+  // writes elem to the queue
+  void write(T&& elem) {
+    std::unique_lock<std::mutex> lk(lock_);
+    buffer_.emplace(std::forward<T>(elem));
+    cv_.notify_one();
+  }
+
+  /// Moves a dequeued element onto elem, blocking until an element
+  /// is available.
+  // returns false if EOF
+  bool read(T& elem) {
+    std::unique_lock<std::mutex> lk(lock_);
+    cv_.wait(lk, [&] { return eof_ || !buffer_.empty(); });
+    if (eof_ && buffer_.empty()) {
+      return false;
+    }
+    elem = std::move(buffer_.front());
+    buffer_.pop();
+    cv_.notify_one();
+    return true;
+  }
+
+ private:
+  std::condition_variable cv_;
+  mutable std::mutex lock_;
+  std::queue<T> buffer_;
+  bool eof_;
+};
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/coding.cc b/src/rocksdb/util/coding.cc
new file mode 100644
index 000000000..a54324d28
--- /dev/null
+++ b/src/rocksdb/util/coding.cc
@@ -0,0 +1,89 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/coding.h"
+
+#include <algorithm>
+#include "rocksdb/slice.h"
+#include "rocksdb/slice_transform.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// conversion' conversion from 'type1' to 'type2', possible loss of data
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable : 4244)
+#endif
+char* EncodeVarint32(char* dst, uint32_t v) {
+  // Operate on characters as unsigneds
+  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
+  static const int B = 128;
+  if (v < (1 << 7)) {
+    *(ptr++) = v;
+  } else if (v < (1 << 14)) {
+    *(ptr++) = v | B;
+    *(ptr++) = v >> 7;
+  } else if (v < (1 << 21)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = v >> 14;
+  } else if (v < (1 << 28)) {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = v >> 21;
+  } else {
+    *(ptr++) = v | B;
+    *(ptr++) = (v >> 7) | B;
+    *(ptr++) = (v >> 14) | B;
+    *(ptr++) = (v >> 21) | B;
+    *(ptr++) = v >> 28;
+  }
+  return reinterpret_cast<char*>(ptr);
+}
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+const char* GetVarint32PtrFallback(const char* p, const char* limit,
+                                   uint32_t* value) {
+  uint32_t result = 0;
+  for (uint32_t shift = 0; shift <= 28 && p < limit; shift += 7) {
+    uint32_t byte = *(reinterpret_cast<const unsigned char*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+const char* GetVarint64Ptr(const char* p, const char* limit, uint64_t* value) {
+  uint64_t result = 0;
+  for (uint32_t shift = 0; shift <= 63 && p < limit; shift += 7) {
+    uint64_t byte = *(reinterpret_cast<const unsigned char*>(p));
+    p++;
+    if (byte & 128) {
+      // More bytes are present
+      result |= ((byte & 127) << shift);
+    } else {
+      result |= (byte << shift);
+      *value = result;
+      return reinterpret_cast<const char*>(p);
+    }
+  }
+  return nullptr;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/coding.h b/src/rocksdb/util/coding.h
new file mode 100644
index 000000000..d46654ec4
--- /dev/null
+++ b/src/rocksdb/util/coding.h
@@ -0,0 +1,480 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Endian-neutral encoding:
+// * Fixed-length numbers are encoded with least-significant byte first
+// * In addition we support variable length "varint" encoding
+// * Strings are encoded prefixed by their length in varint format
+
+#pragma once
+#include <algorithm>
+#include <stdint.h>
+#include <string.h>
+#include <string>
+
+#include "rocksdb/write_batch.h"
+#include "port/port.h"
+
+// Some processors does not allow unaligned access to memory
+#if defined(__sparc)
+  #define PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+// The maximum length of a varint in bytes for 64-bit.
+const unsigned int kMaxVarint64Length = 10;
+
+// Standard Put... routines append to a string
+extern void PutFixed16(std::string* dst, uint16_t value);
+extern void PutFixed32(std::string* dst, uint32_t value);
+extern void PutFixed64(std::string* dst, uint64_t value);
+extern void PutVarint32(std::string* dst, uint32_t value);
+extern void PutVarint32Varint32(std::string* dst, uint32_t value1,
+                                uint32_t value2);
+extern void PutVarint32Varint32Varint32(std::string* dst, uint32_t value1,
+                                        uint32_t value2, uint32_t value3);
+extern void PutVarint64(std::string* dst, uint64_t value);
+extern void PutVarint64Varint64(std::string* dst, uint64_t value1,
+                                uint64_t value2);
+extern void PutVarint32Varint64(std::string* dst, uint32_t value1,
+                                uint64_t value2);
+extern void PutVarint32Varint32Varint64(std::string* dst, uint32_t value1,
+                                        uint32_t value2, uint64_t value3);
+extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
+extern void PutLengthPrefixedSliceParts(std::string* dst,
+                                        const SliceParts& slice_parts);
+extern void PutLengthPrefixedSlicePartsWithPadding(
+    std::string* dst, const SliceParts& slice_parts, size_t pad_sz);
+
+// Standard Get... routines parse a value from the beginning of a Slice
+// and advance the slice past the parsed value.
+extern bool GetFixed64(Slice* input, uint64_t* value);
+extern bool GetFixed32(Slice* input, uint32_t* value);
+extern bool GetFixed16(Slice* input, uint16_t* value);
+extern bool GetVarint32(Slice* input, uint32_t* value);
+extern bool GetVarint64(Slice* input, uint64_t* value);
+extern bool GetVarsignedint64(Slice* input, int64_t* value);
+extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
+// This function assumes data is well-formed.
+extern Slice GetLengthPrefixedSlice(const char* data);
+
+extern Slice GetSliceUntil(Slice* slice, char delimiter);
+
+// Borrowed from
+// https://github.com/facebook/fbthrift/blob/449a5f77f9f9bae72c9eb5e78093247eef185c04/thrift/lib/cpp/util/VarintUtils-inl.h#L202-L208
+constexpr inline uint64_t i64ToZigzag(const int64_t l) {
+  return (static_cast<uint64_t>(l) << 1) ^ static_cast<uint64_t>(l >> 63);
+}
+inline int64_t zigzagToI64(uint64_t n) {
+  return (n >> 1) ^ -static_cast<int64_t>(n & 1);
+}
+
+// Pointer-based variants of GetVarint...  These either store a value
+// in *v and return a pointer just past the parsed value, or return
+// nullptr on error.  These routines only look at bytes in the range
+// [p..limit-1]
+extern const char* GetVarint32Ptr(const char* p,const char* limit, uint32_t* v);
+extern const char* GetVarint64Ptr(const char* p,const char* limit, uint64_t* v);
+inline const char* GetVarsignedint64Ptr(const char* p, const char* limit,
+                                        int64_t* value) {
+  uint64_t u = 0;
+  const char* ret = GetVarint64Ptr(p, limit, &u);
+  *value = zigzagToI64(u);
+  return ret;
+}
+
+// Returns the length of the varint32 or varint64 encoding of "v"
+extern int VarintLength(uint64_t v);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// REQUIRES: dst has enough space for the value being written
+extern void EncodeFixed16(char* dst, uint16_t value);
+extern void EncodeFixed32(char* dst, uint32_t value);
+extern void EncodeFixed64(char* dst, uint64_t value);
+
+// Lower-level versions of Put... that write directly into a character buffer
+// and return a pointer just past the last byte written.
+// REQUIRES: dst has enough space for the value being written
+extern char* EncodeVarint32(char* dst, uint32_t value);
+extern char* EncodeVarint64(char* dst, uint64_t value);
+
+// Lower-level versions of Get... that read directly from a character buffer
+// without any bounds checking.
+
+inline uint16_t DecodeFixed16(const char* ptr) {
+  if (port::kLittleEndian) {
+    // Load the raw bytes
+    uint16_t result;
+    memcpy(&result, ptr, sizeof(result));  // gcc optimizes this to a plain load
+    return result;
+  } else {
+    return ((static_cast<uint16_t>(static_cast<unsigned char>(ptr[0]))) |
+            (static_cast<uint16_t>(static_cast<unsigned char>(ptr[1])) << 8));
+  }
+}
+
+inline uint32_t DecodeFixed32(const char* ptr) {
+  if (port::kLittleEndian) {
+    // Load the raw bytes
+    uint32_t result;
+    memcpy(&result, ptr, sizeof(result));  // gcc optimizes this to a plain load
+    return result;
+  } else {
+    return ((static_cast<uint32_t>(static_cast<unsigned char>(ptr[0])))
+        | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[1])) << 8)
+        | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[2])) << 16)
+        | (static_cast<uint32_t>(static_cast<unsigned char>(ptr[3])) << 24));
+  }
+}
+
+inline uint64_t DecodeFixed64(const char* ptr) {
+  if (port::kLittleEndian) {
+    // Load the raw bytes
+    uint64_t result;
+    memcpy(&result, ptr, sizeof(result));  // gcc optimizes this to a plain load
+    return result;
+  } else {
+    uint64_t lo = DecodeFixed32(ptr);
+    uint64_t hi = DecodeFixed32(ptr + 4);
+    return (hi << 32) | lo;
+  }
+}
+
+// Internal routine for use by fallback path of GetVarint32Ptr
+extern const char* GetVarint32PtrFallback(const char* p,
+                                          const char* limit,
+                                          uint32_t* value);
+inline const char* GetVarint32Ptr(const char* p,
+                                  const char* limit,
+                                  uint32_t* value) {
+  if (p < limit) {
+    uint32_t result = *(reinterpret_cast<const unsigned char*>(p));
+    if ((result & 128) == 0) {
+      *value = result;
+      return p + 1;
+    }
+  }
+  return GetVarint32PtrFallback(p, limit, value);
+}
+
+// -- Implementation of the functions declared above
+inline void EncodeFixed16(char* buf, uint16_t value) {
+  if (port::kLittleEndian) {
+    memcpy(buf, &value, sizeof(value));
+  } else {
+    buf[0] = value & 0xff;
+    buf[1] = (value >> 8) & 0xff;
+  }
+}
+
+inline void EncodeFixed32(char* buf, uint32_t value) {
+  if (port::kLittleEndian) {
+    memcpy(buf, &value, sizeof(value));
+  } else {
+    buf[0] = value & 0xff;
+    buf[1] = (value >> 8) & 0xff;
+    buf[2] = (value >> 16) & 0xff;
+    buf[3] = (value >> 24) & 0xff;
+  }
+}
+
+inline void EncodeFixed64(char* buf, uint64_t value) {
+  if (port::kLittleEndian) {
+    memcpy(buf, &value, sizeof(value));
+  } else {
+    buf[0] = value & 0xff;
+    buf[1] = (value >> 8) & 0xff;
+    buf[2] = (value >> 16) & 0xff;
+    buf[3] = (value >> 24) & 0xff;
+    buf[4] = (value >> 32) & 0xff;
+    buf[5] = (value >> 40) & 0xff;
+    buf[6] = (value >> 48) & 0xff;
+    buf[7] = (value >> 56) & 0xff;
+  }
+}
+
+// Pull the last 8 bits and cast it to a character
+inline void PutFixed16(std::string* dst, uint16_t value) {
+  if (port::kLittleEndian) {
+    dst->append(const_cast<const char*>(reinterpret_cast<char*>(&value)),
+                sizeof(value));
+  } else {
+    char buf[sizeof(value)];
+    EncodeFixed16(buf, value);
+    dst->append(buf, sizeof(buf));
+  }
+}
+
+inline void PutFixed32(std::string* dst, uint32_t value) {
+  if (port::kLittleEndian) {
+    dst->append(const_cast<const char*>(reinterpret_cast<char*>(&value)),
+      sizeof(value));
+  } else {
+    char buf[sizeof(value)];
+    EncodeFixed32(buf, value);
+    dst->append(buf, sizeof(buf));
+  }
+}
+
+inline void PutFixed64(std::string* dst, uint64_t value) {
+  if (port::kLittleEndian) {
+    dst->append(const_cast<const char*>(reinterpret_cast<char*>(&value)),
+      sizeof(value));
+  } else {
+    char buf[sizeof(value)];
+    EncodeFixed64(buf, value);
+    dst->append(buf, sizeof(buf));
+  }
+}
+
+inline void PutVarint32(std::string* dst, uint32_t v) {
+  char buf[5];
+  char* ptr = EncodeVarint32(buf, v);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarint32Varint32(std::string* dst, uint32_t v1, uint32_t v2) {
+  char buf[10];
+  char* ptr = EncodeVarint32(buf, v1);
+  ptr = EncodeVarint32(ptr, v2);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarint32Varint32Varint32(std::string* dst, uint32_t v1,
+                                        uint32_t v2, uint32_t v3) {
+  char buf[15];
+  char* ptr = EncodeVarint32(buf, v1);
+  ptr = EncodeVarint32(ptr, v2);
+  ptr = EncodeVarint32(ptr, v3);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline char* EncodeVarint64(char* dst, uint64_t v) {
+  static const unsigned int B = 128;
+  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
+  while (v >= B) {
+    *(ptr++) = (v & (B - 1)) | B;
+    v >>= 7;
+  }
+  *(ptr++) = static_cast<unsigned char>(v);
+  return reinterpret_cast<char*>(ptr);
+}
+
+inline void PutVarint64(std::string* dst, uint64_t v) {
+  char buf[kMaxVarint64Length];
+  char* ptr = EncodeVarint64(buf, v);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarsignedint64(std::string* dst, int64_t v) {
+  char buf[kMaxVarint64Length];
+  // Using Zigzag format to convert signed to unsigned
+  char* ptr = EncodeVarint64(buf, i64ToZigzag(v));
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarint64Varint64(std::string* dst, uint64_t v1, uint64_t v2) {
+  char buf[20];
+  char* ptr = EncodeVarint64(buf, v1);
+  ptr = EncodeVarint64(ptr, v2);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarint32Varint64(std::string* dst, uint32_t v1, uint64_t v2) {
+  char buf[15];
+  char* ptr = EncodeVarint32(buf, v1);
+  ptr = EncodeVarint64(ptr, v2);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutVarint32Varint32Varint64(std::string* dst, uint32_t v1,
+                                        uint32_t v2, uint64_t v3) {
+  char buf[20];
+  char* ptr = EncodeVarint32(buf, v1);
+  ptr = EncodeVarint32(ptr, v2);
+  ptr = EncodeVarint64(ptr, v3);
+  dst->append(buf, static_cast<size_t>(ptr - buf));
+}
+
+inline void PutLengthPrefixedSlice(std::string* dst, const Slice& value) {
+  PutVarint32(dst, static_cast<uint32_t>(value.size()));
+  dst->append(value.data(), value.size());
+}
+
+inline void PutLengthPrefixedSliceParts(std::string* dst, size_t total_bytes,
+                                        const SliceParts& slice_parts) {
+  for (int i = 0; i < slice_parts.num_parts; ++i) {
+    total_bytes += slice_parts.parts[i].size();
+  }
+  PutVarint32(dst, static_cast<uint32_t>(total_bytes));
+  for (int i = 0; i < slice_parts.num_parts; ++i) {
+    dst->append(slice_parts.parts[i].data(), slice_parts.parts[i].size());
+  }
+}
+
+inline void PutLengthPrefixedSliceParts(std::string* dst,
+                                        const SliceParts& slice_parts) {
+  PutLengthPrefixedSliceParts(dst, /*total_bytes=*/0, slice_parts);
+}
+
+inline void PutLengthPrefixedSlicePartsWithPadding(
+    std::string* dst, const SliceParts& slice_parts, size_t pad_sz) {
+  PutLengthPrefixedSliceParts(dst, /*total_bytes=*/pad_sz, slice_parts);
+  dst->append(pad_sz, '\0');
+}
+
+inline int VarintLength(uint64_t v) {
+  int len = 1;
+  while (v >= 128) {
+    v >>= 7;
+    len++;
+  }
+  return len;
+}
+
+inline bool GetFixed64(Slice* input, uint64_t* value) {
+  if (input->size() < sizeof(uint64_t)) {
+    return false;
+  }
+  *value = DecodeFixed64(input->data());
+  input->remove_prefix(sizeof(uint64_t));
+  return true;
+}
+
+inline bool GetFixed32(Slice* input, uint32_t* value) {
+  if (input->size() < sizeof(uint32_t)) {
+    return false;
+  }
+  *value = DecodeFixed32(input->data());
+  input->remove_prefix(sizeof(uint32_t));
+  return true;
+}
+
+inline bool GetFixed16(Slice* input, uint16_t* value) {
+  if (input->size() < sizeof(uint16_t)) {
+    return false;
+  }
+  *value = DecodeFixed16(input->data());
+  input->remove_prefix(sizeof(uint16_t));
+  return true;
+}
+
+inline bool GetVarint32(Slice* input, uint32_t* value) {
+  const char* p = input->data();
+  const char* limit = p + input->size();
+  const char* q = GetVarint32Ptr(p, limit, value);
+  if (q == nullptr) {
+    return false;
+  } else {
+    *input = Slice(q, static_cast<size_t>(limit - q));
+    return true;
+  }
+}
+
+inline bool GetVarint64(Slice* input, uint64_t* value) {
+  const char* p = input->data();
+  const char* limit = p + input->size();
+  const char* q = GetVarint64Ptr(p, limit, value);
+  if (q == nullptr) {
+    return false;
+  } else {
+    *input = Slice(q, static_cast<size_t>(limit - q));
+    return true;
+  }
+}
+
+inline bool GetVarsignedint64(Slice* input, int64_t* value) {
+  const char* p = input->data();
+  const char* limit = p + input->size();
+  const char* q = GetVarsignedint64Ptr(p, limit, value);
+  if (q == nullptr) {
+    return false;
+  } else {
+    *input = Slice(q, static_cast<size_t>(limit - q));
+    return true;
+  }
+}
+
+// Provide an interface for platform independent endianness transformation
+inline uint64_t EndianTransform(uint64_t input, size_t size) {
+  char* pos = reinterpret_cast<char*>(&input);
+  uint64_t ret_val = 0;
+  for (size_t i = 0; i < size; ++i) {
+    ret_val |= (static_cast<uint64_t>(static_cast<unsigned char>(pos[i]))
+                << ((size - i - 1) << 3));
+  }
+  return ret_val;
+}
+
+inline bool GetLengthPrefixedSlice(Slice* input, Slice* result) {
+  uint32_t len = 0;
+  if (GetVarint32(input, &len) && input->size() >= len) {
+    *result = Slice(input->data(), len);
+    input->remove_prefix(len);
+    return true;
+  } else {
+    return false;
+  }
+}
+
+inline Slice GetLengthPrefixedSlice(const char* data) {
+  uint32_t len = 0;
+  // +5: we assume "data" is not corrupted
+  // unsigned char is 7 bits, uint32_t is 32 bits, need 5 unsigned char
+  auto p = GetVarint32Ptr(data, data + 5 /* limit */, &len);
+  return Slice(p, len);
+}
+
+inline Slice GetSliceUntil(Slice* slice, char delimiter) {
+  uint32_t len = 0;
+  for (len = 0; len < slice->size() && slice->data()[len] != delimiter; ++len) {
+    // nothing
+  }
+
+  Slice ret(slice->data(), len);
+  slice->remove_prefix(len + ((len < slice->size()) ? 1 : 0));
+  return ret;
+}
+
+template<class T>
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+inline void PutUnaligned(T *memory, const T &value) {
+#if defined(PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED)
+  char *nonAlignedMemory = reinterpret_cast<char*>(memory);
+  memcpy(nonAlignedMemory, reinterpret_cast<const char*>(&value), sizeof(T));
+#else
+  *memory = value;
+#endif
+}
+
+template<class T>
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+inline void GetUnaligned(const T *memory, T *value) {
+#if defined(PLATFORM_UNALIGNED_ACCESS_NOT_ALLOWED)
+  char *nonAlignedMemory = reinterpret_cast<char*>(value);
+  memcpy(nonAlignedMemory, reinterpret_cast<const char*>(memory), sizeof(T));
+#else
+  *value = *memory;
+#endif
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/coding_test.cc b/src/rocksdb/util/coding_test.cc
new file mode 100644
index 000000000..383e3f514
--- /dev/null
+++ b/src/rocksdb/util/coding_test.cc
@@ -0,0 +1,217 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/coding.h"
+
+#include "test_util/testharness.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class Coding { };
+TEST(Coding, Fixed16) {
+  std::string s;
+  for (uint16_t v = 0; v < 0xFFFF; v++) {
+    PutFixed16(&s, v);
+  }
+
+  const char* p = s.data();
+  for (uint16_t v = 0; v < 0xFFFF; v++) {
+    uint16_t actual = DecodeFixed16(p);
+    ASSERT_EQ(v, actual);
+    p += sizeof(uint16_t);
+  }
+}
+
+TEST(Coding, Fixed32) {
+  std::string s;
+  for (uint32_t v = 0; v < 100000; v++) {
+    PutFixed32(&s, v);
+  }
+
+  const char* p = s.data();
+  for (uint32_t v = 0; v < 100000; v++) {
+    uint32_t actual = DecodeFixed32(p);
+    ASSERT_EQ(v, actual);
+    p += sizeof(uint32_t);
+  }
+}
+
+TEST(Coding, Fixed64) {
+  std::string s;
+  for (int power = 0; power <= 63; power++) {
+    uint64_t v = static_cast<uint64_t>(1) << power;
+    PutFixed64(&s, v - 1);
+    PutFixed64(&s, v + 0);
+    PutFixed64(&s, v + 1);
+  }
+
+  const char* p = s.data();
+  for (int power = 0; power <= 63; power++) {
+    uint64_t v = static_cast<uint64_t>(1) << power;
+    uint64_t actual = 0;
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v-1, actual);
+    p += sizeof(uint64_t);
+
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v+0, actual);
+    p += sizeof(uint64_t);
+
+    actual = DecodeFixed64(p);
+    ASSERT_EQ(v+1, actual);
+    p += sizeof(uint64_t);
+  }
+}
+
+// Test that encoding routines generate little-endian encodings
+TEST(Coding, EncodingOutput) {
+  std::string dst;
+  PutFixed32(&dst, 0x04030201);
+  ASSERT_EQ(4U, dst.size());
+  ASSERT_EQ(0x01, static_cast<int>(dst[0]));
+  ASSERT_EQ(0x02, static_cast<int>(dst[1]));
+  ASSERT_EQ(0x03, static_cast<int>(dst[2]));
+  ASSERT_EQ(0x04, static_cast<int>(dst[3]));
+
+  dst.clear();
+  PutFixed64(&dst, 0x0807060504030201ull);
+  ASSERT_EQ(8U, dst.size());
+  ASSERT_EQ(0x01, static_cast<int>(dst[0]));
+  ASSERT_EQ(0x02, static_cast<int>(dst[1]));
+  ASSERT_EQ(0x03, static_cast<int>(dst[2]));
+  ASSERT_EQ(0x04, static_cast<int>(dst[3]));
+  ASSERT_EQ(0x05, static_cast<int>(dst[4]));
+  ASSERT_EQ(0x06, static_cast<int>(dst[5]));
+  ASSERT_EQ(0x07, static_cast<int>(dst[6]));
+  ASSERT_EQ(0x08, static_cast<int>(dst[7]));
+}
+
+TEST(Coding, Varint32) {
+  std::string s;
+  for (uint32_t i = 0; i < (32 * 32); i++) {
+    uint32_t v = (i / 32) << (i % 32);
+    PutVarint32(&s, v);
+  }
+
+  const char* p = s.data();
+  const char* limit = p + s.size();
+  for (uint32_t i = 0; i < (32 * 32); i++) {
+    uint32_t expected = (i / 32) << (i % 32);
+    uint32_t actual = 0;
+    const char* start = p;
+    p = GetVarint32Ptr(p, limit, &actual);
+    ASSERT_TRUE(p != nullptr);
+    ASSERT_EQ(expected, actual);
+    ASSERT_EQ(VarintLength(actual), p - start);
+  }
+  ASSERT_EQ(p, s.data() + s.size());
+}
+
+TEST(Coding, Varint64) {
+  // Construct the list of values to check
+  std::vector<uint64_t> values;
+  // Some special values
+  values.push_back(0);
+  values.push_back(100);
+  values.push_back(~static_cast<uint64_t>(0));
+  values.push_back(~static_cast<uint64_t>(0) - 1);
+  for (uint32_t k = 0; k < 64; k++) {
+    // Test values near powers of two
+    const uint64_t power = 1ull << k;
+    values.push_back(power);
+    values.push_back(power-1);
+    values.push_back(power+1);
+  };
+
+  std::string s;
+  for (unsigned int i = 0; i < values.size(); i++) {
+    PutVarint64(&s, values[i]);
+  }
+
+  const char* p = s.data();
+  const char* limit = p + s.size();
+  for (unsigned int i = 0; i < values.size(); i++) {
+    ASSERT_TRUE(p < limit);
+    uint64_t actual = 0;
+    const char* start = p;
+    p = GetVarint64Ptr(p, limit, &actual);
+    ASSERT_TRUE(p != nullptr);
+    ASSERT_EQ(values[i], actual);
+    ASSERT_EQ(VarintLength(actual), p - start);
+  }
+  ASSERT_EQ(p, limit);
+
+}
+
+TEST(Coding, Varint32Overflow) {
+  uint32_t result;
+  std::string input("\x81\x82\x83\x84\x85\x11");
+  ASSERT_TRUE(GetVarint32Ptr(input.data(), input.data() + input.size(), &result)
+              == nullptr);
+}
+
+TEST(Coding, Varint32Truncation) {
+  uint32_t large_value = (1u << 31) + 100;
+  std::string s;
+  PutVarint32(&s, large_value);
+  uint32_t result;
+  for (unsigned int len = 0; len < s.size() - 1; len++) {
+    ASSERT_TRUE(GetVarint32Ptr(s.data(), s.data() + len, &result) == nullptr);
+  }
+  ASSERT_TRUE(
+      GetVarint32Ptr(s.data(), s.data() + s.size(), &result) != nullptr);
+  ASSERT_EQ(large_value, result);
+}
+
+TEST(Coding, Varint64Overflow) {
+  uint64_t result;
+  std::string input("\x81\x82\x83\x84\x85\x81\x82\x83\x84\x85\x11");
+  ASSERT_TRUE(GetVarint64Ptr(input.data(), input.data() + input.size(), &result)
+              == nullptr);
+}
+
+TEST(Coding, Varint64Truncation) {
+  uint64_t large_value = (1ull << 63) + 100ull;
+  std::string s;
+  PutVarint64(&s, large_value);
+  uint64_t result;
+  for (unsigned int len = 0; len < s.size() - 1; len++) {
+    ASSERT_TRUE(GetVarint64Ptr(s.data(), s.data() + len, &result) == nullptr);
+  }
+  ASSERT_TRUE(
+      GetVarint64Ptr(s.data(), s.data() + s.size(), &result) != nullptr);
+  ASSERT_EQ(large_value, result);
+}
+
+TEST(Coding, Strings) {
+  std::string s;
+  PutLengthPrefixedSlice(&s, Slice(""));
+  PutLengthPrefixedSlice(&s, Slice("foo"));
+  PutLengthPrefixedSlice(&s, Slice("bar"));
+  PutLengthPrefixedSlice(&s, Slice(std::string(200, 'x')));
+
+  Slice input(s);
+  Slice v;
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("foo", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ("bar", v.ToString());
+  ASSERT_TRUE(GetLengthPrefixedSlice(&input, &v));
+  ASSERT_EQ(std::string(200, 'x'), v.ToString());
+  ASSERT_EQ("", input.ToString());
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/compaction_job_stats_impl.cc b/src/rocksdb/util/compaction_job_stats_impl.cc
new file mode 100644
index 000000000..4d16891e4
--- /dev/null
+++ b/src/rocksdb/util/compaction_job_stats_impl.cc
@@ -0,0 +1,91 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "rocksdb/compaction_job_stats.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+#ifndef ROCKSDB_LITE
+
+void CompactionJobStats::Reset() {
+  elapsed_micros = 0;
+  cpu_micros = 0;
+
+  num_input_records = 0;
+  num_input_files = 0;
+  num_input_files_at_output_level = 0;
+
+  num_output_records = 0;
+  num_output_files = 0;
+
+  is_manual_compaction = 0;
+
+  total_input_bytes = 0;
+  total_output_bytes = 0;
+
+  num_records_replaced = 0;
+
+  total_input_raw_key_bytes = 0;
+  total_input_raw_value_bytes = 0;
+
+  num_input_deletion_records = 0;
+  num_expired_deletion_records = 0;
+
+  num_corrupt_keys = 0;
+
+  file_write_nanos = 0;
+  file_range_sync_nanos = 0;
+  file_fsync_nanos = 0;
+  file_prepare_write_nanos = 0;
+
+  smallest_output_key_prefix.clear();
+  largest_output_key_prefix.clear();
+
+  num_single_del_fallthru = 0;
+  num_single_del_mismatch = 0;
+}
+
+void CompactionJobStats::Add(const CompactionJobStats& stats) {
+  elapsed_micros += stats.elapsed_micros;
+  cpu_micros += stats.cpu_micros;
+
+  num_input_records += stats.num_input_records;
+  num_input_files += stats.num_input_files;
+  num_input_files_at_output_level += stats.num_input_files_at_output_level;
+
+  num_output_records += stats.num_output_records;
+  num_output_files += stats.num_output_files;
+
+  total_input_bytes += stats.total_input_bytes;
+  total_output_bytes += stats.total_output_bytes;
+
+  num_records_replaced += stats.num_records_replaced;
+
+  total_input_raw_key_bytes += stats.total_input_raw_key_bytes;
+  total_input_raw_value_bytes += stats.total_input_raw_value_bytes;
+
+  num_input_deletion_records += stats.num_input_deletion_records;
+  num_expired_deletion_records += stats.num_expired_deletion_records;
+
+  num_corrupt_keys += stats.num_corrupt_keys;
+
+  file_write_nanos += stats.file_write_nanos;
+  file_range_sync_nanos += stats.file_range_sync_nanos;
+  file_fsync_nanos += stats.file_fsync_nanos;
+  file_prepare_write_nanos += stats.file_prepare_write_nanos;
+
+  num_single_del_fallthru += stats.num_single_del_fallthru;
+  num_single_del_mismatch += stats.num_single_del_mismatch;
+}
+
+#else
+
+void CompactionJobStats::Reset() {}
+
+void CompactionJobStats::Add(const CompactionJobStats& /*stats*/) {}
+
+#endif  // !ROCKSDB_LITE
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/comparator.cc b/src/rocksdb/util/comparator.cc
new file mode 100644
index 000000000..48340bd96
--- /dev/null
+++ b/src/rocksdb/util/comparator.cc
@@ -0,0 +1,216 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "rocksdb/comparator.h"
+#include <stdint.h>
+#include <algorithm>
+#include <memory>
+#include "logging/logging.h"
+#include "port/port.h"
+#include "rocksdb/slice.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+namespace {
+class BytewiseComparatorImpl : public Comparator {
+ public:
+  BytewiseComparatorImpl() { }
+
+  const char* Name() const override { return "leveldb.BytewiseComparator"; }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    return a.compare(b);
+  }
+
+  bool Equal(const Slice& a, const Slice& b) const override { return a == b; }
+
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    // Find length of common prefix
+    size_t min_length = std::min(start->size(), limit.size());
+    size_t diff_index = 0;
+    while ((diff_index < min_length) &&
+           ((*start)[diff_index] == limit[diff_index])) {
+      diff_index++;
+    }
+
+    if (diff_index >= min_length) {
+      // Do not shorten if one string is a prefix of the other
+    } else {
+      uint8_t start_byte = static_cast<uint8_t>((*start)[diff_index]);
+      uint8_t limit_byte = static_cast<uint8_t>(limit[diff_index]);
+      if (start_byte >= limit_byte) {
+        // Cannot shorten since limit is smaller than start or start is
+        // already the shortest possible.
+        return;
+      }
+      assert(start_byte < limit_byte);
+
+      if (diff_index < limit.size() - 1 || start_byte + 1 < limit_byte) {
+        (*start)[diff_index]++;
+        start->resize(diff_index + 1);
+      } else {
+        //     v
+        // A A 1 A A A
+        // A A 2
+        //
+        // Incrementing the current byte will make start bigger than limit, we
+        // will skip this byte, and find the first non 0xFF byte in start and
+        // increment it.
+        diff_index++;
+
+        while (diff_index < start->size()) {
+          // Keep moving until we find the first non 0xFF byte to
+          // increment it
+          if (static_cast<uint8_t>((*start)[diff_index]) <
+              static_cast<uint8_t>(0xff)) {
+            (*start)[diff_index]++;
+            start->resize(diff_index + 1);
+            break;
+          }
+          diff_index++;
+        }
+      }
+      assert(Compare(*start, limit) < 0);
+    }
+  }
+
+  void FindShortSuccessor(std::string* key) const override {
+    // Find first character that can be incremented
+    size_t n = key->size();
+    for (size_t i = 0; i < n; i++) {
+      const uint8_t byte = (*key)[i];
+      if (byte != static_cast<uint8_t>(0xff)) {
+        (*key)[i] = byte + 1;
+        key->resize(i+1);
+        return;
+      }
+    }
+    // *key is a run of 0xffs.  Leave it alone.
+  }
+
+  bool IsSameLengthImmediateSuccessor(const Slice& s,
+                                      const Slice& t) const override {
+    if (s.size() != t.size() || s.size() == 0) {
+      return false;
+    }
+    size_t diff_ind = s.difference_offset(t);
+    // same slice
+    if (diff_ind >= s.size()) return false;
+    uint8_t byte_s = static_cast<uint8_t>(s[diff_ind]);
+    uint8_t byte_t = static_cast<uint8_t>(t[diff_ind]);
+    // first different byte must be consecutive, and remaining bytes must be
+    // 0xff for s and 0x00 for t
+    if (byte_s != uint8_t{0xff} && byte_s + 1 == byte_t) {
+      for (size_t i = diff_ind + 1; i < s.size(); ++i) {
+        byte_s = static_cast<uint8_t>(s[i]);
+        byte_t = static_cast<uint8_t>(t[i]);
+        if (byte_s != uint8_t{0xff} || byte_t != uint8_t{0x00}) {
+          return false;
+        }
+      }
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  bool CanKeysWithDifferentByteContentsBeEqual() const override {
+    return false;
+  }
+
+  int CompareWithoutTimestamp(const Slice& a, const Slice& b) const override {
+    return a.compare(b);
+  }
+};
+
+class ReverseBytewiseComparatorImpl : public BytewiseComparatorImpl {
+ public:
+  ReverseBytewiseComparatorImpl() { }
+
+  const char* Name() const override {
+    return "rocksdb.ReverseBytewiseComparator";
+  }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    return -a.compare(b);
+  }
+
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    // Find length of common prefix
+    size_t min_length = std::min(start->size(), limit.size());
+    size_t diff_index = 0;
+    while ((diff_index < min_length) &&
+           ((*start)[diff_index] == limit[diff_index])) {
+      diff_index++;
+    }
+
+    assert(diff_index <= min_length);
+    if (diff_index == min_length) {
+      // Do not shorten if one string is a prefix of the other
+      //
+      // We could handle cases like:
+      //     V
+      // A A 2 X Y
+      // A A 2
+      // in a similar way as BytewiseComparator::FindShortestSeparator().
+      // We keep it simple by not implementing it. We can come back to it
+      // later when needed.
+    } else {
+      uint8_t start_byte = static_cast<uint8_t>((*start)[diff_index]);
+      uint8_t limit_byte = static_cast<uint8_t>(limit[diff_index]);
+      if (start_byte > limit_byte && diff_index < start->size() - 1) {
+        // Case like
+        //     V
+        // A A 3 A A
+        // A A 1 B B
+        //
+        // or
+        //     v
+        // A A 2 A A
+        // A A 1 B B
+        // In this case "AA2" will be good.
+#ifndef NDEBUG
+        std::string old_start = *start;
+#endif
+        start->resize(diff_index + 1);
+#ifndef NDEBUG
+        assert(old_start >= *start);
+#endif
+        assert(Slice(*start).compare(limit) > 0);
+      }
+    }
+  }
+
+  void FindShortSuccessor(std::string* /*key*/) const override {
+    // Don't do anything for simplicity.
+  }
+
+  bool CanKeysWithDifferentByteContentsBeEqual() const override {
+    return false;
+  }
+
+  int CompareWithoutTimestamp(const Slice& a, const Slice& b) const override {
+    return -a.compare(b);
+  }
+};
+}// namespace
+
+const Comparator* BytewiseComparator() {
+  static BytewiseComparatorImpl bytewise;
+  return &bytewise;
+}
+
+const Comparator* ReverseBytewiseComparator() {
+  static ReverseBytewiseComparatorImpl rbytewise;
+  return &rbytewise;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/compression.h b/src/rocksdb/util/compression.h
new file mode 100644
index 000000000..8169841ba
--- /dev/null
+++ b/src/rocksdb/util/compression.h
@@ -0,0 +1,1407 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+#pragma once
+
+#include <algorithm>
+#include <limits>
+#ifdef ROCKSDB_MALLOC_USABLE_SIZE
+#ifdef OS_FREEBSD
+#include <malloc_np.h>
+#else  // OS_FREEBSD
+#include <malloc.h>
+#endif  // OS_FREEBSD
+#endif  // ROCKSDB_MALLOC_USABLE_SIZE
+#include <string>
+
+#include "memory/memory_allocator.h"
+#include "rocksdb/options.h"
+#include "rocksdb/table.h"
+#include "util/coding.h"
+#include "util/compression_context_cache.h"
+#include "util/string_util.h"
+
+#ifdef SNAPPY
+#include <snappy.h>
+#endif
+
+#ifdef ZLIB
+#include <zlib.h>
+#endif
+
+#ifdef BZIP2
+#include <bzlib.h>
+#endif
+
+#if defined(LZ4)
+#include <lz4.h>
+#include <lz4hc.h>
+#endif
+
+#if defined(ZSTD)
+#include <zstd.h>
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
+#include <zdict.h>
+#endif  // ZSTD_VERSION_NUMBER >= 10103
+namespace ROCKSDB_NAMESPACE {
+// Need this for the context allocation override
+// On windows we need to do this explicitly
+#if (ZSTD_VERSION_NUMBER >= 500)
+#if defined(ROCKSDB_JEMALLOC) && defined(OS_WIN) && \
+    defined(ZSTD_STATIC_LINKING_ONLY)
+#define ROCKSDB_ZSTD_CUSTOM_MEM
+namespace port {
+ZSTD_customMem GetJeZstdAllocationOverrides();
+}  // namespace port
+#endif  // defined(ROCKSDB_JEMALLOC) && defined(OS_WIN) &&
+        // defined(ZSTD_STATIC_LINKING_ONLY)
+
+// We require `ZSTD_sizeof_DDict` and `ZSTD_createDDict_byReference` to use
+// `ZSTD_DDict`. The former was introduced in v1.0.0 and the latter was
+// introduced in v1.1.3. But an important bug fix for `ZSTD_sizeof_DDict` came
+// in v1.1.4, so that is the version we require. As of today's latest version
+// (v1.3.8), they are both still in the experimental API, which means they are
+// only exported when the compiler flag `ZSTD_STATIC_LINKING_ONLY` is set.
+#if defined(ZSTD_STATIC_LINKING_ONLY) && ZSTD_VERSION_NUMBER >= 10104
+#define ROCKSDB_ZSTD_DDICT
+#endif  // defined(ZSTD_STATIC_LINKING_ONLY) && ZSTD_VERSION_NUMBER >= 10104
+
+// Cached data represents a portion that can be re-used
+// If, in the future we have more than one native context to
+// cache we can arrange this as a tuple
+class ZSTDUncompressCachedData {
+ public:
+  using ZSTDNativeContext = ZSTD_DCtx*;
+  ZSTDUncompressCachedData() {}
+  // Init from cache
+  ZSTDUncompressCachedData(const ZSTDUncompressCachedData& o) = delete;
+  ZSTDUncompressCachedData& operator=(const ZSTDUncompressCachedData&) = delete;
+  ZSTDUncompressCachedData(ZSTDUncompressCachedData&& o) ROCKSDB_NOEXCEPT
+      : ZSTDUncompressCachedData() {
+    *this = std::move(o);
+  }
+  ZSTDUncompressCachedData& operator=(ZSTDUncompressCachedData&& o)
+      ROCKSDB_NOEXCEPT {
+    assert(zstd_ctx_ == nullptr);
+    std::swap(zstd_ctx_, o.zstd_ctx_);
+    std::swap(cache_idx_, o.cache_idx_);
+    return *this;
+  }
+  ZSTDNativeContext Get() const { return zstd_ctx_; }
+  int64_t GetCacheIndex() const { return cache_idx_; }
+  void CreateIfNeeded() {
+    if (zstd_ctx_ == nullptr) {
+#ifdef ROCKSDB_ZSTD_CUSTOM_MEM
+      zstd_ctx_ =
+          ZSTD_createDCtx_advanced(port::GetJeZstdAllocationOverrides());
+#else   // ROCKSDB_ZSTD_CUSTOM_MEM
+      zstd_ctx_ = ZSTD_createDCtx();
+#endif  // ROCKSDB_ZSTD_CUSTOM_MEM
+      cache_idx_ = -1;
+    }
+  }
+  void InitFromCache(const ZSTDUncompressCachedData& o, int64_t idx) {
+    zstd_ctx_ = o.zstd_ctx_;
+    cache_idx_ = idx;
+  }
+  ~ZSTDUncompressCachedData() {
+    if (zstd_ctx_ != nullptr && cache_idx_ == -1) {
+      ZSTD_freeDCtx(zstd_ctx_);
+    }
+  }
+
+ private:
+  ZSTDNativeContext zstd_ctx_ = nullptr;
+  int64_t cache_idx_ = -1;  // -1 means this instance owns the context
+};
+#endif  // (ZSTD_VERSION_NUMBER >= 500)
+}  // namespace ROCKSDB_NAMESPACE
+#endif  // ZSTD
+
+#if !(defined ZSTD) || !(ZSTD_VERSION_NUMBER >= 500)
+namespace ROCKSDB_NAMESPACE {
+class ZSTDUncompressCachedData {
+  void* padding;  // unused
+ public:
+  using ZSTDNativeContext = void*;
+  ZSTDUncompressCachedData() {}
+  ZSTDUncompressCachedData(const ZSTDUncompressCachedData&) {}
+  ZSTDUncompressCachedData& operator=(const ZSTDUncompressCachedData&) = delete;
+  ZSTDUncompressCachedData(ZSTDUncompressCachedData&&)
+      ROCKSDB_NOEXCEPT = default;
+  ZSTDUncompressCachedData& operator=(ZSTDUncompressCachedData&&)
+      ROCKSDB_NOEXCEPT = default;
+  ZSTDNativeContext Get() const { return nullptr; }
+  int64_t GetCacheIndex() const { return -1; }
+  void CreateIfNeeded() {}
+  void InitFromCache(const ZSTDUncompressCachedData&, int64_t) {}
+ private:
+  void ignore_padding__() { padding = nullptr; }
+};
+}  // namespace ROCKSDB_NAMESPACE
+#endif
+
+#if defined(XPRESS)
+#include "port/xpress.h"
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+// Holds dictionary and related data, like ZSTD's digested compression
+// dictionary.
+struct CompressionDict {
+#if ZSTD_VERSION_NUMBER >= 700
+  ZSTD_CDict* zstd_cdict_ = nullptr;
+#endif  // ZSTD_VERSION_NUMBER >= 700
+  std::string dict_;
+
+ public:
+#if ZSTD_VERSION_NUMBER >= 700
+  CompressionDict(std::string dict, CompressionType type, int level) {
+#else   // ZSTD_VERSION_NUMBER >= 700
+  CompressionDict(std::string dict, CompressionType /*type*/, int /*level*/) {
+#endif  // ZSTD_VERSION_NUMBER >= 700
+    dict_ = std::move(dict);
+#if ZSTD_VERSION_NUMBER >= 700
+    zstd_cdict_ = nullptr;
+    if (!dict_.empty() && (type == kZSTD || type == kZSTDNotFinalCompression)) {
+      if (level == CompressionOptions::kDefaultCompressionLevel) {
+        // 3 is the value of ZSTD_CLEVEL_DEFAULT (not exposed publicly), see
+        // https://github.com/facebook/zstd/issues/1148
+        level = 3;
+      }
+      // Should be safe (but slower) if below call fails as we'll use the
+      // raw dictionary to compress.
+      zstd_cdict_ = ZSTD_createCDict(dict_.data(), dict_.size(), level);
+      assert(zstd_cdict_ != nullptr);
+    }
+#endif  // ZSTD_VERSION_NUMBER >= 700
+  }
+
+  ~CompressionDict() {
+#if ZSTD_VERSION_NUMBER >= 700
+    size_t res = 0;
+    if (zstd_cdict_ != nullptr) {
+      res = ZSTD_freeCDict(zstd_cdict_);
+    }
+    assert(res == 0);  // Last I checked they can't fail
+    (void)res;         // prevent unused var warning
+#endif                 // ZSTD_VERSION_NUMBER >= 700
+  }
+
+#if ZSTD_VERSION_NUMBER >= 700
+  const ZSTD_CDict* GetDigestedZstdCDict() const { return zstd_cdict_; }
+#endif  // ZSTD_VERSION_NUMBER >= 700
+
+  Slice GetRawDict() const { return dict_; }
+
+  static const CompressionDict& GetEmptyDict() {
+    static CompressionDict empty_dict{};
+    return empty_dict;
+  }
+
+  CompressionDict() = default;
+  // Disable copy/move
+  CompressionDict(const CompressionDict&) = delete;
+  CompressionDict& operator=(const CompressionDict&) = delete;
+  CompressionDict(CompressionDict&&) = delete;
+  CompressionDict& operator=(CompressionDict&&) = delete;
+};
+
+// Holds dictionary and related data, like ZSTD's digested uncompression
+// dictionary.
+struct UncompressionDict {
+  // Block containing the data for the compression dictionary in case the
+  // constructor that takes a string parameter is used.
+  std::string dict_;
+
+  // Block containing the data for the compression dictionary in case the
+  // constructor that takes a Slice parameter is used and the passed in
+  // CacheAllocationPtr is not nullptr.
+  CacheAllocationPtr allocation_;
+
+  // Slice pointing to the compression dictionary data. Can point to
+  // dict_, allocation_, or some other memory location, depending on how
+  // the object was constructed.
+  Slice slice_;
+
+#ifdef ROCKSDB_ZSTD_DDICT
+  // Processed version of the contents of slice_ for ZSTD compression.
+  ZSTD_DDict* zstd_ddict_ = nullptr;
+#endif  // ROCKSDB_ZSTD_DDICT
+
+#ifdef ROCKSDB_ZSTD_DDICT
+  UncompressionDict(std::string dict, bool using_zstd)
+#else   // ROCKSDB_ZSTD_DDICT
+  UncompressionDict(std::string dict, bool /* using_zstd */)
+#endif  // ROCKSDB_ZSTD_DDICT
+      : dict_(std::move(dict)), slice_(dict_) {
+#ifdef ROCKSDB_ZSTD_DDICT
+    if (!slice_.empty() && using_zstd) {
+      zstd_ddict_ = ZSTD_createDDict_byReference(slice_.data(), slice_.size());
+      assert(zstd_ddict_ != nullptr);
+    }
+#endif  // ROCKSDB_ZSTD_DDICT
+  }
+
+#ifdef ROCKSDB_ZSTD_DDICT
+  UncompressionDict(Slice slice, CacheAllocationPtr&& allocation,
+                    bool using_zstd)
+#else   // ROCKSDB_ZSTD_DDICT
+  UncompressionDict(Slice slice, CacheAllocationPtr&& allocation,
+                    bool /* using_zstd */)
+#endif  // ROCKSDB_ZSTD_DDICT
+      : allocation_(std::move(allocation)), slice_(std::move(slice)) {
+#ifdef ROCKSDB_ZSTD_DDICT
+    if (!slice_.empty() && using_zstd) {
+      zstd_ddict_ = ZSTD_createDDict_byReference(slice_.data(), slice_.size());
+      assert(zstd_ddict_ != nullptr);
+    }
+#endif  // ROCKSDB_ZSTD_DDICT
+  }
+
+  UncompressionDict(UncompressionDict&& rhs)
+      : dict_(std::move(rhs.dict_)),
+        allocation_(std::move(rhs.allocation_)),
+        slice_(std::move(rhs.slice_))
+#ifdef ROCKSDB_ZSTD_DDICT
+        ,
+        zstd_ddict_(rhs.zstd_ddict_)
+#endif
+  {
+#ifdef ROCKSDB_ZSTD_DDICT
+    rhs.zstd_ddict_ = nullptr;
+#endif
+  }
+
+  ~UncompressionDict() {
+#ifdef ROCKSDB_ZSTD_DDICT
+    size_t res = 0;
+    if (zstd_ddict_ != nullptr) {
+      res = ZSTD_freeDDict(zstd_ddict_);
+    }
+    assert(res == 0);  // Last I checked they can't fail
+    (void)res;         // prevent unused var warning
+#endif                 // ROCKSDB_ZSTD_DDICT
+  }
+
+  UncompressionDict& operator=(UncompressionDict&& rhs) {
+    if (this == &rhs) {
+      return *this;
+    }
+
+    dict_ = std::move(rhs.dict_);
+    allocation_ = std::move(rhs.allocation_);
+    slice_ = std::move(rhs.slice_);
+
+#ifdef ROCKSDB_ZSTD_DDICT
+    zstd_ddict_ = rhs.zstd_ddict_;
+    rhs.zstd_ddict_ = nullptr;
+#endif
+
+    return *this;
+  }
+
+  // The object is self-contained if the string constructor is used, or the
+  // Slice constructor is invoked with a non-null allocation. Otherwise, it
+  // is the caller's responsibility to ensure that the underlying storage
+  // outlives this object.
+  bool own_bytes() const { return !dict_.empty() || allocation_; }
+
+  const Slice& GetRawDict() const { return slice_; }
+
+#ifdef ROCKSDB_ZSTD_DDICT
+  const ZSTD_DDict* GetDigestedZstdDDict() const { return zstd_ddict_; }
+#endif  // ROCKSDB_ZSTD_DDICT
+
+  static const UncompressionDict& GetEmptyDict() {
+    static UncompressionDict empty_dict{};
+    return empty_dict;
+  }
+
+  size_t ApproximateMemoryUsage() const {
+    size_t usage = sizeof(struct UncompressionDict);
+    usage += dict_.size();
+    if (allocation_) {
+      auto allocator = allocation_.get_deleter().allocator;
+      if (allocator) {
+        usage += allocator->UsableSize(allocation_.get(), slice_.size());
+      } else {
+        usage += slice_.size();
+      }
+    }
+#ifdef ROCKSDB_ZSTD_DDICT
+    usage += ZSTD_sizeof_DDict(zstd_ddict_);
+#endif  // ROCKSDB_ZSTD_DDICT
+    return usage;
+  }
+
+  UncompressionDict() = default;
+  // Disable copy
+  UncompressionDict(const CompressionDict&) = delete;
+  UncompressionDict& operator=(const CompressionDict&) = delete;
+};
+
+class CompressionContext {
+ private:
+#if defined(ZSTD) && (ZSTD_VERSION_NUMBER >= 500)
+  ZSTD_CCtx* zstd_ctx_ = nullptr;
+  void CreateNativeContext(CompressionType type) {
+    if (type == kZSTD || type == kZSTDNotFinalCompression) {
+#ifdef ROCKSDB_ZSTD_CUSTOM_MEM
+      zstd_ctx_ =
+          ZSTD_createCCtx_advanced(port::GetJeZstdAllocationOverrides());
+#else   // ROCKSDB_ZSTD_CUSTOM_MEM
+      zstd_ctx_ = ZSTD_createCCtx();
+#endif  // ROCKSDB_ZSTD_CUSTOM_MEM
+    }
+  }
+  void DestroyNativeContext() {
+    if (zstd_ctx_ != nullptr) {
+      ZSTD_freeCCtx(zstd_ctx_);
+    }
+  }
+
+ public:
+  // callable inside ZSTD_Compress
+  ZSTD_CCtx* ZSTDPreallocCtx() const {
+    assert(zstd_ctx_ != nullptr);
+    return zstd_ctx_;
+  }
+
+#else   // ZSTD && (ZSTD_VERSION_NUMBER >= 500)
+ private:
+  void CreateNativeContext(CompressionType /* type */) {}
+  void DestroyNativeContext() {}
+#endif  // ZSTD && (ZSTD_VERSION_NUMBER >= 500)
+ public:
+  explicit CompressionContext(CompressionType type) {
+    CreateNativeContext(type);
+  }
+  ~CompressionContext() { DestroyNativeContext(); }
+  CompressionContext(const CompressionContext&) = delete;
+  CompressionContext& operator=(const CompressionContext&) = delete;
+};
+
+class CompressionInfo {
+  const CompressionOptions& opts_;
+  const CompressionContext& context_;
+  const CompressionDict& dict_;
+  const CompressionType type_;
+  const uint64_t sample_for_compression_;
+
+ public:
+  CompressionInfo(const CompressionOptions& _opts,
+                  const CompressionContext& _context,
+                  const CompressionDict& _dict, CompressionType _type,
+                  uint64_t _sample_for_compression)
+      : opts_(_opts),
+        context_(_context),
+        dict_(_dict),
+        type_(_type),
+        sample_for_compression_(_sample_for_compression) {}
+
+  const CompressionOptions& options() const { return opts_; }
+  const CompressionContext& context() const { return context_; }
+  const CompressionDict& dict() const { return dict_; }
+  CompressionType type() const { return type_; }
+  uint64_t SampleForCompression() const { return sample_for_compression_; }
+};
+
+class UncompressionContext {
+ private:
+  CompressionContextCache* ctx_cache_ = nullptr;
+  ZSTDUncompressCachedData uncomp_cached_data_;
+
+ public:
+  struct NoCache {};
+  // Do not use context cache, used by TableBuilder
+  UncompressionContext(NoCache, CompressionType /* type */) {}
+
+  explicit UncompressionContext(CompressionType type) {
+    if (type == kZSTD || type == kZSTDNotFinalCompression) {
+      ctx_cache_ = CompressionContextCache::Instance();
+      uncomp_cached_data_ = ctx_cache_->GetCachedZSTDUncompressData();
+    }
+  }
+  ~UncompressionContext() {
+    if (uncomp_cached_data_.GetCacheIndex() != -1) {
+      assert(ctx_cache_ != nullptr);
+      ctx_cache_->ReturnCachedZSTDUncompressData(
+          uncomp_cached_data_.GetCacheIndex());
+    }
+  }
+  UncompressionContext(const UncompressionContext&) = delete;
+  UncompressionContext& operator=(const UncompressionContext&) = delete;
+
+  ZSTDUncompressCachedData::ZSTDNativeContext GetZSTDContext() const {
+    return uncomp_cached_data_.Get();
+  }
+};
+
+class UncompressionInfo {
+  const UncompressionContext& context_;
+  const UncompressionDict& dict_;
+  const CompressionType type_;
+
+ public:
+  UncompressionInfo(const UncompressionContext& _context,
+                    const UncompressionDict& _dict, CompressionType _type)
+      : context_(_context), dict_(_dict), type_(_type) {}
+
+  const UncompressionContext& context() const { return context_; }
+  const UncompressionDict& dict() const { return dict_; }
+  CompressionType type() const { return type_; }
+};
+
+inline bool Snappy_Supported() {
+#ifdef SNAPPY
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool Zlib_Supported() {
+#ifdef ZLIB
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool BZip2_Supported() {
+#ifdef BZIP2
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool LZ4_Supported() {
+#ifdef LZ4
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool XPRESS_Supported() {
+#ifdef XPRESS
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool ZSTD_Supported() {
+#ifdef ZSTD
+  // ZSTD format is finalized since version 0.8.0.
+  return (ZSTD_versionNumber() >= 800);
+#else
+  return false;
+#endif
+}
+
+inline bool ZSTDNotFinal_Supported() {
+#ifdef ZSTD
+  return true;
+#else
+  return false;
+#endif
+}
+
+inline bool CompressionTypeSupported(CompressionType compression_type) {
+  switch (compression_type) {
+    case kNoCompression:
+      return true;
+    case kSnappyCompression:
+      return Snappy_Supported();
+    case kZlibCompression:
+      return Zlib_Supported();
+    case kBZip2Compression:
+      return BZip2_Supported();
+    case kLZ4Compression:
+      return LZ4_Supported();
+    case kLZ4HCCompression:
+      return LZ4_Supported();
+    case kXpressCompression:
+      return XPRESS_Supported();
+    case kZSTDNotFinalCompression:
+      return ZSTDNotFinal_Supported();
+    case kZSTD:
+      return ZSTD_Supported();
+    default:
+      assert(false);
+      return false;
+  }
+}
+
+inline std::string CompressionTypeToString(CompressionType compression_type) {
+  switch (compression_type) {
+    case kNoCompression:
+      return "NoCompression";
+    case kSnappyCompression:
+      return "Snappy";
+    case kZlibCompression:
+      return "Zlib";
+    case kBZip2Compression:
+      return "BZip2";
+    case kLZ4Compression:
+      return "LZ4";
+    case kLZ4HCCompression:
+      return "LZ4HC";
+    case kXpressCompression:
+      return "Xpress";
+    case kZSTD:
+      return "ZSTD";
+    case kZSTDNotFinalCompression:
+      return "ZSTDNotFinal";
+    case kDisableCompressionOption:
+      return "DisableOption";
+    default:
+      assert(false);
+      return "";
+  }
+}
+
+inline std::string CompressionOptionsToString(
+    CompressionOptions& compression_options) {
+  std::string result;
+  result.reserve(512);
+  result.append("window_bits=")
+      .append(ToString(compression_options.window_bits))
+      .append("; ");
+  result.append("level=")
+      .append(ToString(compression_options.level))
+      .append("; ");
+  result.append("strategy=")
+      .append(ToString(compression_options.strategy))
+      .append("; ");
+  result.append("max_dict_bytes=")
+      .append(ToString(compression_options.max_dict_bytes))
+      .append("; ");
+  result.append("zstd_max_train_bytes=")
+      .append(ToString(compression_options.zstd_max_train_bytes))
+      .append("; ");
+  result.append("enabled=")
+      .append(ToString(compression_options.enabled))
+      .append("; ");
+  return result;
+}
+
+// compress_format_version can have two values:
+// 1 -- decompressed sizes for BZip2 and Zlib are not included in the compressed
+// block. Also, decompressed sizes for LZ4 are encoded in platform-dependent
+// way.
+// 2 -- Zlib, BZip2 and LZ4 encode decompressed size as Varint32 just before the
+// start of compressed block. Snappy format is the same as version 1.
+
+inline bool Snappy_Compress(const CompressionInfo& /*info*/, const char* input,
+                            size_t length, ::std::string* output) {
+#ifdef SNAPPY
+  output->resize(snappy::MaxCompressedLength(length));
+  size_t outlen;
+  snappy::RawCompress(input, length, &(*output)[0], &outlen);
+  output->resize(outlen);
+  return true;
+#else
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
+                                         size_t* result) {
+#ifdef SNAPPY
+  return snappy::GetUncompressedLength(input, length, result);
+#else
+  (void)input;
+  (void)length;
+  (void)result;
+  return false;
+#endif
+}
+
+inline bool Snappy_Uncompress(const char* input, size_t length, char* output) {
+#ifdef SNAPPY
+  return snappy::RawUncompress(input, length, output);
+#else
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+namespace compression {
+// returns size
+inline size_t PutDecompressedSizeInfo(std::string* output, uint32_t length) {
+  PutVarint32(output, length);
+  return output->size();
+}
+
+inline bool GetDecompressedSizeInfo(const char** input_data,
+                                    size_t* input_length,
+                                    uint32_t* output_len) {
+  auto new_input_data =
+      GetVarint32Ptr(*input_data, *input_data + *input_length, output_len);
+  if (new_input_data == nullptr) {
+    return false;
+  }
+  *input_length -= (new_input_data - *input_data);
+  *input_data = new_input_data;
+  return true;
+}
+}  // namespace compression
+
+// compress_format_version == 1 -- decompressed size is not included in the
+// block header
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline bool Zlib_Compress(const CompressionInfo& info,
+                          uint32_t compress_format_version, const char* input,
+                          size_t length, ::std::string* output) {
+#ifdef ZLIB
+  if (length > std::numeric_limits<uint32_t>::max()) {
+    // Can't compress more than 4GB
+    return false;
+  }
+
+  size_t output_header_len = 0;
+  if (compress_format_version == 2) {
+    output_header_len = compression::PutDecompressedSizeInfo(
+        output, static_cast<uint32_t>(length));
+  }
+  // Resize output to be the plain data length.
+  // This may not be big enough if the compression actually expands data.
+  output->resize(output_header_len + length);
+
+  // The memLevel parameter specifies how much memory should be allocated for
+  // the internal compression state.
+  // memLevel=1 uses minimum memory but is slow and reduces compression ratio.
+  // memLevel=9 uses maximum memory for optimal speed.
+  // The default value is 8. See zconf.h for more details.
+  static const int memLevel = 8;
+  int level;
+  if (info.options().level == CompressionOptions::kDefaultCompressionLevel) {
+    level = Z_DEFAULT_COMPRESSION;
+  } else {
+    level = info.options().level;
+  }
+  z_stream _stream;
+  memset(&_stream, 0, sizeof(z_stream));
+  int st = deflateInit2(&_stream, level, Z_DEFLATED, info.options().window_bits,
+                        memLevel, info.options().strategy);
+  if (st != Z_OK) {
+    return false;
+  }
+
+  Slice compression_dict = info.dict().GetRawDict();
+  if (compression_dict.size()) {
+    // Initialize the compression library's dictionary
+    st = deflateSetDictionary(
+        &_stream, reinterpret_cast<const Bytef*>(compression_dict.data()),
+        static_cast<unsigned int>(compression_dict.size()));
+    if (st != Z_OK) {
+      deflateEnd(&_stream);
+      return false;
+    }
+  }
+
+  // Compress the input, and put compressed data in output.
+  _stream.next_in = (Bytef*)input;
+  _stream.avail_in = static_cast<unsigned int>(length);
+
+  // Initialize the output size.
+  _stream.avail_out = static_cast<unsigned int>(length);
+  _stream.next_out = reinterpret_cast<Bytef*>(&(*output)[output_header_len]);
+
+  bool compressed = false;
+  st = deflate(&_stream, Z_FINISH);
+  if (st == Z_STREAM_END) {
+    compressed = true;
+    output->resize(output->size() - _stream.avail_out);
+  }
+  // The only return value we really care about is Z_STREAM_END.
+  // Z_OK means insufficient output space. This means the compression is
+  // bigger than decompressed size. Just fail the compression in that case.
+
+  deflateEnd(&_stream);
+  return compressed;
+#else
+  (void)info;
+  (void)compress_format_version;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is not included in the
+// block header
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline CacheAllocationPtr Zlib_Uncompress(
+    const UncompressionInfo& info, const char* input_data, size_t input_length,
+    int* decompress_size, uint32_t compress_format_version,
+    MemoryAllocator* allocator = nullptr, int windowBits = -14) {
+#ifdef ZLIB
+  uint32_t output_len = 0;
+  if (compress_format_version == 2) {
+    if (!compression::GetDecompressedSizeInfo(&input_data, &input_length,
+                                              &output_len)) {
+      return nullptr;
+    }
+  } else {
+    // Assume the decompressed data size will 5x of compressed size, but round
+    // to the page size
+    size_t proposed_output_len = ((input_length * 5) & (~(4096 - 1))) + 4096;
+    output_len = static_cast<uint32_t>(
+        std::min(proposed_output_len,
+                 static_cast<size_t>(std::numeric_limits<uint32_t>::max())));
+  }
+
+  z_stream _stream;
+  memset(&_stream, 0, sizeof(z_stream));
+
+  // For raw inflate, the windowBits should be -8..-15.
+  // If windowBits is bigger than zero, it will use either zlib
+  // header or gzip header. Adding 32 to it will do automatic detection.
+  int st =
+      inflateInit2(&_stream, windowBits > 0 ? windowBits + 32 : windowBits);
+  if (st != Z_OK) {
+    return nullptr;
+  }
+
+  const Slice& compression_dict = info.dict().GetRawDict();
+  if (compression_dict.size()) {
+    // Initialize the compression library's dictionary
+    st = inflateSetDictionary(
+        &_stream, reinterpret_cast<const Bytef*>(compression_dict.data()),
+        static_cast<unsigned int>(compression_dict.size()));
+    if (st != Z_OK) {
+      return nullptr;
+    }
+  }
+
+  _stream.next_in = (Bytef*)input_data;
+  _stream.avail_in = static_cast<unsigned int>(input_length);
+
+  auto output = AllocateBlock(output_len, allocator);
+
+  _stream.next_out = (Bytef*)output.get();
+  _stream.avail_out = static_cast<unsigned int>(output_len);
+
+  bool done = false;
+  while (!done) {
+    st = inflate(&_stream, Z_SYNC_FLUSH);
+    switch (st) {
+      case Z_STREAM_END:
+        done = true;
+        break;
+      case Z_OK: {
+        // No output space. Increase the output space by 20%.
+        // We should never run out of output space if
+        // compress_format_version == 2
+        assert(compress_format_version != 2);
+        size_t old_sz = output_len;
+        uint32_t output_len_delta = output_len / 5;
+        output_len += output_len_delta < 10 ? 10 : output_len_delta;
+        auto tmp = AllocateBlock(output_len, allocator);
+        memcpy(tmp.get(), output.get(), old_sz);
+        output = std::move(tmp);
+
+        // Set more output.
+        _stream.next_out = (Bytef*)(output.get() + old_sz);
+        _stream.avail_out = static_cast<unsigned int>(output_len - old_sz);
+        break;
+      }
+      case Z_BUF_ERROR:
+      default:
+        inflateEnd(&_stream);
+        return nullptr;
+    }
+  }
+
+  // If we encoded decompressed block size, we should have no bytes left
+  assert(compress_format_version != 2 || _stream.avail_out == 0);
+  *decompress_size = static_cast<int>(output_len - _stream.avail_out);
+  inflateEnd(&_stream);
+  return output;
+#else
+  (void)info;
+  (void)input_data;
+  (void)input_length;
+  (void)decompress_size;
+  (void)compress_format_version;
+  (void)allocator;
+  (void)windowBits;
+  return nullptr;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is not included in the
+// block header
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+inline bool BZip2_Compress(const CompressionInfo& /*info*/,
+                           uint32_t compress_format_version, const char* input,
+                           size_t length, ::std::string* output) {
+#ifdef BZIP2
+  if (length > std::numeric_limits<uint32_t>::max()) {
+    // Can't compress more than 4GB
+    return false;
+  }
+  size_t output_header_len = 0;
+  if (compress_format_version == 2) {
+    output_header_len = compression::PutDecompressedSizeInfo(
+        output, static_cast<uint32_t>(length));
+  }
+  // Resize output to be the plain data length.
+  // This may not be big enough if the compression actually expands data.
+  output->resize(output_header_len + length);
+
+  bz_stream _stream;
+  memset(&_stream, 0, sizeof(bz_stream));
+
+  // Block size 1 is 100K.
+  // 0 is for silent.
+  // 30 is the default workFactor
+  int st = BZ2_bzCompressInit(&_stream, 1, 0, 30);
+  if (st != BZ_OK) {
+    return false;
+  }
+
+  // Compress the input, and put compressed data in output.
+  _stream.next_in = (char*)input;
+  _stream.avail_in = static_cast<unsigned int>(length);
+
+  // Initialize the output size.
+  _stream.avail_out = static_cast<unsigned int>(length);
+  _stream.next_out = reinterpret_cast<char*>(&(*output)[output_header_len]);
+
+  bool compressed = false;
+  st = BZ2_bzCompress(&_stream, BZ_FINISH);
+  if (st == BZ_STREAM_END) {
+    compressed = true;
+    output->resize(output->size() - _stream.avail_out);
+  }
+  // The only return value we really care about is BZ_STREAM_END.
+  // BZ_FINISH_OK means insufficient output space. This means the compression
+  // is bigger than decompressed size. Just fail the compression in that case.
+
+  BZ2_bzCompressEnd(&_stream);
+  return compressed;
+#else
+  (void)compress_format_version;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is not included in the
+// block header
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+inline CacheAllocationPtr BZip2_Uncompress(
+    const char* input_data, size_t input_length, int* decompress_size,
+    uint32_t compress_format_version, MemoryAllocator* allocator = nullptr) {
+#ifdef BZIP2
+  uint32_t output_len = 0;
+  if (compress_format_version == 2) {
+    if (!compression::GetDecompressedSizeInfo(&input_data, &input_length,
+                                              &output_len)) {
+      return nullptr;
+    }
+  } else {
+    // Assume the decompressed data size will 5x of compressed size, but round
+    // to the next page size
+    size_t proposed_output_len = ((input_length * 5) & (~(4096 - 1))) + 4096;
+    output_len = static_cast<uint32_t>(
+        std::min(proposed_output_len,
+                 static_cast<size_t>(std::numeric_limits<uint32_t>::max())));
+  }
+
+  bz_stream _stream;
+  memset(&_stream, 0, sizeof(bz_stream));
+
+  int st = BZ2_bzDecompressInit(&_stream, 0, 0);
+  if (st != BZ_OK) {
+    return nullptr;
+  }
+
+  _stream.next_in = (char*)input_data;
+  _stream.avail_in = static_cast<unsigned int>(input_length);
+
+  auto output = AllocateBlock(output_len, allocator);
+
+  _stream.next_out = (char*)output.get();
+  _stream.avail_out = static_cast<unsigned int>(output_len);
+
+  bool done = false;
+  while (!done) {
+    st = BZ2_bzDecompress(&_stream);
+    switch (st) {
+      case BZ_STREAM_END:
+        done = true;
+        break;
+      case BZ_OK: {
+        // No output space. Increase the output space by 20%.
+        // We should never run out of output space if
+        // compress_format_version == 2
+        assert(compress_format_version != 2);
+        uint32_t old_sz = output_len;
+        output_len = output_len * 1.2;
+        auto tmp = AllocateBlock(output_len, allocator);
+        memcpy(tmp.get(), output.get(), old_sz);
+        output = std::move(tmp);
+
+        // Set more output.
+        _stream.next_out = (char*)(output.get() + old_sz);
+        _stream.avail_out = static_cast<unsigned int>(output_len - old_sz);
+        break;
+      }
+      default:
+        BZ2_bzDecompressEnd(&_stream);
+        return nullptr;
+    }
+  }
+
+  // If we encoded decompressed block size, we should have no bytes left
+  assert(compress_format_version != 2 || _stream.avail_out == 0);
+  *decompress_size = static_cast<int>(output_len - _stream.avail_out);
+  BZ2_bzDecompressEnd(&_stream);
+  return output;
+#else
+  (void)input_data;
+  (void)input_length;
+  (void)decompress_size;
+  (void)compress_format_version;
+  (void)allocator;
+  return nullptr;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is included in the
+// block header using memcpy, which makes database non-portable)
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline bool LZ4_Compress(const CompressionInfo& info,
+                         uint32_t compress_format_version, const char* input,
+                         size_t length, ::std::string* output) {
+#ifdef LZ4
+  if (length > std::numeric_limits<uint32_t>::max()) {
+    // Can't compress more than 4GB
+    return false;
+  }
+
+  size_t output_header_len = 0;
+  if (compress_format_version == 2) {
+    // new encoding, using varint32 to store size information
+    output_header_len = compression::PutDecompressedSizeInfo(
+        output, static_cast<uint32_t>(length));
+  } else {
+    // legacy encoding, which is not really portable (depends on big/little
+    // endianness)
+    output_header_len = 8;
+    output->resize(output_header_len);
+    char* p = const_cast<char*>(output->c_str());
+    memcpy(p, &length, sizeof(length));
+  }
+  int compress_bound = LZ4_compressBound(static_cast<int>(length));
+  output->resize(static_cast<size_t>(output_header_len + compress_bound));
+
+  int outlen;
+#if LZ4_VERSION_NUMBER >= 10400  // r124+
+  LZ4_stream_t* stream = LZ4_createStream();
+  Slice compression_dict = info.dict().GetRawDict();
+  if (compression_dict.size()) {
+    LZ4_loadDict(stream, compression_dict.data(),
+                 static_cast<int>(compression_dict.size()));
+  }
+#if LZ4_VERSION_NUMBER >= 10700  // r129+
+  outlen =
+      LZ4_compress_fast_continue(stream, input, &(*output)[output_header_len],
+                                 static_cast<int>(length), compress_bound, 1);
+#else  // up to r128
+  outlen = LZ4_compress_limitedOutput_continue(
+      stream, input, &(*output)[output_header_len], static_cast<int>(length),
+      compress_bound);
+#endif
+  LZ4_freeStream(stream);
+#else   // up to r123
+  outlen = LZ4_compress_limitedOutput(input, &(*output)[output_header_len],
+                                      static_cast<int>(length), compress_bound);
+#endif  // LZ4_VERSION_NUMBER >= 10400
+
+  if (outlen == 0) {
+    return false;
+  }
+  output->resize(static_cast<size_t>(output_header_len + outlen));
+  return true;
+#else  // LZ4
+  (void)info;
+  (void)compress_format_version;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is included in the
+// block header using memcpy, which makes database non-portable)
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline CacheAllocationPtr LZ4_Uncompress(const UncompressionInfo& info,
+                                         const char* input_data,
+                                         size_t input_length,
+                                         int* decompress_size,
+                                         uint32_t compress_format_version,
+                                         MemoryAllocator* allocator = nullptr) {
+#ifdef LZ4
+  uint32_t output_len = 0;
+  if (compress_format_version == 2) {
+    // new encoding, using varint32 to store size information
+    if (!compression::GetDecompressedSizeInfo(&input_data, &input_length,
+                                              &output_len)) {
+      return nullptr;
+    }
+  } else {
+    // legacy encoding, which is not really portable (depends on big/little
+    // endianness)
+    if (input_length < 8) {
+      return nullptr;
+    }
+    memcpy(&output_len, input_data, sizeof(output_len));
+    input_length -= 8;
+    input_data += 8;
+  }
+
+  auto output = AllocateBlock(output_len, allocator);
+#if LZ4_VERSION_NUMBER >= 10400  // r124+
+  LZ4_streamDecode_t* stream = LZ4_createStreamDecode();
+  const Slice& compression_dict = info.dict().GetRawDict();
+  if (compression_dict.size()) {
+    LZ4_setStreamDecode(stream, compression_dict.data(),
+                        static_cast<int>(compression_dict.size()));
+  }
+  *decompress_size = LZ4_decompress_safe_continue(
+      stream, input_data, output.get(), static_cast<int>(input_length),
+      static_cast<int>(output_len));
+  LZ4_freeStreamDecode(stream);
+#else   // up to r123
+  *decompress_size = LZ4_decompress_safe(input_data, output.get(),
+                                         static_cast<int>(input_length),
+                                         static_cast<int>(output_len));
+#endif  // LZ4_VERSION_NUMBER >= 10400
+
+  if (*decompress_size < 0) {
+    return nullptr;
+  }
+  assert(*decompress_size == static_cast<int>(output_len));
+  return output;
+#else  // LZ4
+  (void)info;
+  (void)input_data;
+  (void)input_length;
+  (void)decompress_size;
+  (void)compress_format_version;
+  (void)allocator;
+  return nullptr;
+#endif
+}
+
+// compress_format_version == 1 -- decompressed size is included in the
+// block header using memcpy, which makes database non-portable)
+// compress_format_version == 2 -- decompressed size is included in the block
+// header in varint32 format
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline bool LZ4HC_Compress(const CompressionInfo& info,
+                           uint32_t compress_format_version, const char* input,
+                           size_t length, ::std::string* output) {
+#ifdef LZ4
+  if (length > std::numeric_limits<uint32_t>::max()) {
+    // Can't compress more than 4GB
+    return false;
+  }
+
+  size_t output_header_len = 0;
+  if (compress_format_version == 2) {
+    // new encoding, using varint32 to store size information
+    output_header_len = compression::PutDecompressedSizeInfo(
+        output, static_cast<uint32_t>(length));
+  } else {
+    // legacy encoding, which is not really portable (depends on big/little
+    // endianness)
+    output_header_len = 8;
+    output->resize(output_header_len);
+    char* p = const_cast<char*>(output->c_str());
+    memcpy(p, &length, sizeof(length));
+  }
+  int compress_bound = LZ4_compressBound(static_cast<int>(length));
+  output->resize(static_cast<size_t>(output_header_len + compress_bound));
+
+  int outlen;
+  int level;
+  if (info.options().level == CompressionOptions::kDefaultCompressionLevel) {
+    level = 0;  // lz4hc.h says any value < 1 will be sanitized to default
+  } else {
+    level = info.options().level;
+  }
+#if LZ4_VERSION_NUMBER >= 10400  // r124+
+  LZ4_streamHC_t* stream = LZ4_createStreamHC();
+  LZ4_resetStreamHC(stream, level);
+  Slice compression_dict = info.dict().GetRawDict();
+  const char* compression_dict_data =
+      compression_dict.size() > 0 ? compression_dict.data() : nullptr;
+  size_t compression_dict_size = compression_dict.size();
+  LZ4_loadDictHC(stream, compression_dict_data,
+                 static_cast<int>(compression_dict_size));
+
+#if LZ4_VERSION_NUMBER >= 10700  // r129+
+  outlen =
+      LZ4_compress_HC_continue(stream, input, &(*output)[output_header_len],
+                               static_cast<int>(length), compress_bound);
+#else   // r124-r128
+  outlen = LZ4_compressHC_limitedOutput_continue(
+      stream, input, &(*output)[output_header_len], static_cast<int>(length),
+      compress_bound);
+#endif  // LZ4_VERSION_NUMBER >= 10700
+  LZ4_freeStreamHC(stream);
+
+#elif LZ4_VERSION_MAJOR  // r113-r123
+  outlen = LZ4_compressHC2_limitedOutput(input, &(*output)[output_header_len],
+                                         static_cast<int>(length),
+                                         compress_bound, level);
+#else                    // up to r112
+  outlen =
+      LZ4_compressHC_limitedOutput(input, &(*output)[output_header_len],
+                                   static_cast<int>(length), compress_bound);
+#endif                   // LZ4_VERSION_NUMBER >= 10400
+
+  if (outlen == 0) {
+    return false;
+  }
+  output->resize(static_cast<size_t>(output_header_len + outlen));
+  return true;
+#else  // LZ4
+  (void)info;
+  (void)compress_format_version;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+#ifdef XPRESS
+inline bool XPRESS_Compress(const char* input, size_t length,
+                            std::string* output) {
+  return port::xpress::Compress(input, length, output);
+}
+#else
+inline bool XPRESS_Compress(const char* /*input*/, size_t /*length*/,
+                            std::string* /*output*/) {
+  return false;
+}
+#endif
+
+#ifdef XPRESS
+inline char* XPRESS_Uncompress(const char* input_data, size_t input_length,
+                               int* decompress_size) {
+  return port::xpress::Decompress(input_data, input_length, decompress_size);
+}
+#else
+inline char* XPRESS_Uncompress(const char* /*input_data*/,
+                               size_t /*input_length*/,
+                               int* /*decompress_size*/) {
+  return nullptr;
+}
+#endif
+
+inline bool ZSTD_Compress(const CompressionInfo& info, const char* input,
+                          size_t length, ::std::string* output) {
+#ifdef ZSTD
+  if (length > std::numeric_limits<uint32_t>::max()) {
+    // Can't compress more than 4GB
+    return false;
+  }
+
+  size_t output_header_len = compression::PutDecompressedSizeInfo(
+      output, static_cast<uint32_t>(length));
+
+  size_t compressBound = ZSTD_compressBound(length);
+  output->resize(static_cast<size_t>(output_header_len + compressBound));
+  size_t outlen = 0;
+  int level;
+  if (info.options().level == CompressionOptions::kDefaultCompressionLevel) {
+    // 3 is the value of ZSTD_CLEVEL_DEFAULT (not exposed publicly), see
+    // https://github.com/facebook/zstd/issues/1148
+    level = 3;
+  } else {
+    level = info.options().level;
+  }
+#if ZSTD_VERSION_NUMBER >= 500  // v0.5.0+
+  ZSTD_CCtx* context = info.context().ZSTDPreallocCtx();
+  assert(context != nullptr);
+#if ZSTD_VERSION_NUMBER >= 700  // v0.7.0+
+  if (info.dict().GetDigestedZstdCDict() != nullptr) {
+    outlen = ZSTD_compress_usingCDict(context, &(*output)[output_header_len],
+                                      compressBound, input, length,
+                                      info.dict().GetDigestedZstdCDict());
+  }
+#endif  // ZSTD_VERSION_NUMBER >= 700
+  if (outlen == 0) {
+    outlen = ZSTD_compress_usingDict(context, &(*output)[output_header_len],
+                                     compressBound, input, length,
+                                     info.dict().GetRawDict().data(),
+                                     info.dict().GetRawDict().size(), level);
+  }
+#else   // up to v0.4.x
+  outlen = ZSTD_compress(&(*output)[output_header_len], compressBound, input,
+                         length, level);
+#endif  // ZSTD_VERSION_NUMBER >= 500
+  if (outlen == 0) {
+    return false;
+  }
+  output->resize(output_header_len + outlen);
+  return true;
+#else  // ZSTD
+  (void)info;
+  (void)input;
+  (void)length;
+  (void)output;
+  return false;
+#endif
+}
+
+// @param compression_dict Data for presetting the compression library's
+//    dictionary.
+inline CacheAllocationPtr ZSTD_Uncompress(
+    const UncompressionInfo& info, const char* input_data, size_t input_length,
+    int* decompress_size, MemoryAllocator* allocator = nullptr) {
+#ifdef ZSTD
+  uint32_t output_len = 0;
+  if (!compression::GetDecompressedSizeInfo(&input_data, &input_length,
+                                            &output_len)) {
+    return nullptr;
+  }
+
+  auto output = AllocateBlock(output_len, allocator);
+  size_t actual_output_length = 0;
+#if ZSTD_VERSION_NUMBER >= 500  // v0.5.0+
+  ZSTD_DCtx* context = info.context().GetZSTDContext();
+  assert(context != nullptr);
+#ifdef ROCKSDB_ZSTD_DDICT
+  if (info.dict().GetDigestedZstdDDict() != nullptr) {
+    actual_output_length = ZSTD_decompress_usingDDict(
+        context, output.get(), output_len, input_data, input_length,
+        info.dict().GetDigestedZstdDDict());
+  }
+#endif  // ROCKSDB_ZSTD_DDICT
+  if (actual_output_length == 0) {
+    actual_output_length = ZSTD_decompress_usingDict(
+        context, output.get(), output_len, input_data, input_length,
+        info.dict().GetRawDict().data(), info.dict().GetRawDict().size());
+  }
+#else   // up to v0.4.x
+  (void)info;
+  actual_output_length =
+      ZSTD_decompress(output.get(), output_len, input_data, input_length);
+#endif  // ZSTD_VERSION_NUMBER >= 500
+  assert(actual_output_length == output_len);
+  *decompress_size = static_cast<int>(actual_output_length);
+  return output;
+#else  // ZSTD
+  (void)info;
+  (void)input_data;
+  (void)input_length;
+  (void)decompress_size;
+  (void)allocator;
+  return nullptr;
+#endif
+}
+
+inline bool ZSTD_TrainDictionarySupported() {
+#ifdef ZSTD
+  // Dictionary trainer is available since v0.6.1 for static linking, but not
+  // available for dynamic linking until v1.1.3. For now we enable the feature
+  // in v1.1.3+ only.
+  return (ZSTD_versionNumber() >= 10103);
+#else
+  return false;
+#endif
+}
+
+inline std::string ZSTD_TrainDictionary(const std::string& samples,
+                                        const std::vector<size_t>& sample_lens,
+                                        size_t max_dict_bytes) {
+  // Dictionary trainer is available since v0.6.1 for static linking, but not
+  // available for dynamic linking until v1.1.3. For now we enable the feature
+  // in v1.1.3+ only.
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
+  assert(samples.empty() == sample_lens.empty());
+  if (samples.empty()) {
+    return "";
+  }
+  std::string dict_data(max_dict_bytes, '\0');
+  size_t dict_len = ZDICT_trainFromBuffer(
+      &dict_data[0], max_dict_bytes, &samples[0], &sample_lens[0],
+      static_cast<unsigned>(sample_lens.size()));
+  if (ZDICT_isError(dict_len)) {
+    return "";
+  }
+  assert(dict_len <= max_dict_bytes);
+  dict_data.resize(dict_len);
+  return dict_data;
+#else   // up to v1.1.2
+  assert(false);
+  (void)samples;
+  (void)sample_lens;
+  (void)max_dict_bytes;
+  return "";
+#endif  // ZSTD_VERSION_NUMBER >= 10103
+}
+
+inline std::string ZSTD_TrainDictionary(const std::string& samples,
+                                        size_t sample_len_shift,
+                                        size_t max_dict_bytes) {
+  // Dictionary trainer is available since v0.6.1, but ZSTD was marked stable
+  // only since v0.8.0. For now we enable the feature in stable versions only.
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
+  // skips potential partial sample at the end of "samples"
+  size_t num_samples = samples.size() >> sample_len_shift;
+  std::vector<size_t> sample_lens(num_samples, size_t(1) << sample_len_shift);
+  return ZSTD_TrainDictionary(samples, sample_lens, max_dict_bytes);
+#else   // up to v1.1.2
+  assert(false);
+  (void)samples;
+  (void)sample_len_shift;
+  (void)max_dict_bytes;
+  return "";
+#endif  // ZSTD_VERSION_NUMBER >= 10103
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/compression_context_cache.cc b/src/rocksdb/util/compression_context_cache.cc
new file mode 100644
index 000000000..a06cfb279
--- /dev/null
+++ b/src/rocksdb/util/compression_context_cache.cc
@@ -0,0 +1,108 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+
+#include "util/compression_context_cache.h"
+
+#include "util/compression.h"
+#include "util/core_local.h"
+
+#include <atomic>
+
+namespace ROCKSDB_NAMESPACE {
+namespace compression_cache {
+
+void* const SentinelValue = nullptr;
+// Cache ZSTD uncompression contexts for reads
+// if needed we can add ZSTD compression context caching
+// which is currently is not done since BlockBasedTableBuilder
+// simply creates one compression context per new SST file.
+struct ZSTDCachedData {
+  // We choose to cache the below structure instead of a ptr
+  // because we want to avoid a) native types leak b) make
+  // cache use transparent for the user
+  ZSTDUncompressCachedData uncomp_cached_data_;
+  std::atomic<void*> zstd_uncomp_sentinel_;
+
+  char
+      padding[(CACHE_LINE_SIZE -
+               (sizeof(ZSTDUncompressCachedData) + sizeof(std::atomic<void*>)) %
+                   CACHE_LINE_SIZE)];  // unused padding field
+
+  ZSTDCachedData() : zstd_uncomp_sentinel_(&uncomp_cached_data_) {}
+  ZSTDCachedData(const ZSTDCachedData&) = delete;
+  ZSTDCachedData& operator=(const ZSTDCachedData&) = delete;
+
+  ZSTDUncompressCachedData GetUncompressData(int64_t idx) {
+    ZSTDUncompressCachedData result;
+    void* expected = &uncomp_cached_data_;
+    if (zstd_uncomp_sentinel_.compare_exchange_strong(expected,
+                                                      SentinelValue)) {
+      uncomp_cached_data_.CreateIfNeeded();
+      result.InitFromCache(uncomp_cached_data_, idx);
+    } else {
+      // Creates one time use data
+      result.CreateIfNeeded();
+    }
+    return result;
+  }
+  // Return the entry back into circulation
+  // This is executed only when we successfully obtained
+  // in the first place
+  void ReturnUncompressData() {
+    if (zstd_uncomp_sentinel_.exchange(&uncomp_cached_data_) != SentinelValue) {
+      // Means we are returning while not having it acquired.
+      assert(false);
+    }
+  }
+};
+static_assert(sizeof(ZSTDCachedData) % CACHE_LINE_SIZE == 0,
+              "Expected CACHE_LINE_SIZE alignment");
+}  // namespace compression_cache
+
+using namespace compression_cache;
+
+class CompressionContextCache::Rep {
+ public:
+  Rep() {}
+  ZSTDUncompressCachedData GetZSTDUncompressData() {
+    auto p = per_core_uncompr_.AccessElementAndIndex();
+    int64_t idx = static_cast<int64_t>(p.second);
+    return p.first->GetUncompressData(idx);
+  }
+  void ReturnZSTDUncompressData(int64_t idx) {
+    assert(idx >= 0);
+    auto* cn = per_core_uncompr_.AccessAtCore(static_cast<size_t>(idx));
+    cn->ReturnUncompressData();
+  }
+
+ private:
+  CoreLocalArray<ZSTDCachedData> per_core_uncompr_;
+};
+
+CompressionContextCache::CompressionContextCache() : rep_(new Rep()) {}
+
+CompressionContextCache* CompressionContextCache::Instance() {
+  static CompressionContextCache instance;
+  return &instance;
+}
+
+void CompressionContextCache::InitSingleton() { Instance(); }
+
+ZSTDUncompressCachedData
+CompressionContextCache::GetCachedZSTDUncompressData() {
+  return rep_->GetZSTDUncompressData();
+}
+
+void CompressionContextCache::ReturnCachedZSTDUncompressData(int64_t idx) {
+  rep_->ReturnZSTDUncompressData(idx);
+}
+
+CompressionContextCache::~CompressionContextCache() { delete rep_; }
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/compression_context_cache.h b/src/rocksdb/util/compression_context_cache.h
new file mode 100644
index 000000000..7b7b2d507
--- /dev/null
+++ b/src/rocksdb/util/compression_context_cache.h
@@ -0,0 +1,47 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+
+// Compression context cache allows to cache compression/uncompression contexts
+// This helps with Random Read latencies and reduces CPU utilization
+// Caching is implemented using CoreLocal facility. Compression/Uncompression
+// instances are cached on a per core basis using CoreLocalArray. A borrowed
+// instance is atomically replaced with a sentinel value for the time of being
+// used. If it turns out that another thread is already makes use of the
+// instance we still create one on the heap which is later is destroyed.
+
+#pragma once
+
+#include <stdint.h>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+class ZSTDUncompressCachedData;
+
+class CompressionContextCache {
+ public:
+  // Singleton
+  static CompressionContextCache* Instance();
+  static void InitSingleton();
+  CompressionContextCache(const CompressionContextCache&) = delete;
+  CompressionContextCache& operator=(const CompressionContextCache&) = delete;
+
+  ZSTDUncompressCachedData GetCachedZSTDUncompressData();
+  void ReturnCachedZSTDUncompressData(int64_t idx);
+
+ private:
+  // Singleton
+  CompressionContextCache();
+  ~CompressionContextCache();
+
+  class Rep;
+  Rep* rep_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/concurrent_task_limiter_impl.cc b/src/rocksdb/util/concurrent_task_limiter_impl.cc
new file mode 100644
index 000000000..2342677d8
--- /dev/null
+++ b/src/rocksdb/util/concurrent_task_limiter_impl.cc
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/concurrent_task_limiter_impl.h"
+#include "rocksdb/concurrent_task_limiter.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+ConcurrentTaskLimiterImpl::ConcurrentTaskLimiterImpl(
+    const std::string& name, int32_t max_outstanding_task)
+    : name_(name),
+      max_outstanding_tasks_{max_outstanding_task},
+      outstanding_tasks_{0} {
+
+}
+
+ConcurrentTaskLimiterImpl::~ConcurrentTaskLimiterImpl() {
+  assert(outstanding_tasks_ == 0);
+}
+
+const std::string& ConcurrentTaskLimiterImpl::GetName() const {
+  return name_;
+}
+
+void ConcurrentTaskLimiterImpl::SetMaxOutstandingTask(int32_t limit) {
+  max_outstanding_tasks_.store(limit, std::memory_order_relaxed);
+}
+
+void ConcurrentTaskLimiterImpl::ResetMaxOutstandingTask() {
+  max_outstanding_tasks_.store(-1, std::memory_order_relaxed);
+}
+
+int32_t ConcurrentTaskLimiterImpl::GetOutstandingTask() const {
+  return outstanding_tasks_.load(std::memory_order_relaxed);
+}
+
+std::unique_ptr<TaskLimiterToken> ConcurrentTaskLimiterImpl::GetToken(
+    bool force) {
+  int32_t limit = max_outstanding_tasks_.load(std::memory_order_relaxed);
+  int32_t tasks = outstanding_tasks_.load(std::memory_order_relaxed);
+  // force = true, bypass the throttle.
+  // limit < 0 means unlimited tasks.
+  while (force || limit < 0 || tasks < limit) {
+    if (outstanding_tasks_.compare_exchange_weak(tasks, tasks + 1)) {
+      return std::unique_ptr<TaskLimiterToken>(new TaskLimiterToken(this));
+    }
+  }
+  return nullptr;
+}
+
+ConcurrentTaskLimiter* NewConcurrentTaskLimiter(
+    const std::string& name, int32_t limit) {
+  return new ConcurrentTaskLimiterImpl(name, limit);
+}
+
+TaskLimiterToken::~TaskLimiterToken() {
+  --limiter_->outstanding_tasks_;
+  assert(limiter_->outstanding_tasks_ >= 0);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/concurrent_task_limiter_impl.h b/src/rocksdb/util/concurrent_task_limiter_impl.h
new file mode 100644
index 000000000..d8c1e03cb
--- /dev/null
+++ b/src/rocksdb/util/concurrent_task_limiter_impl.h
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+#include <atomic>
+#include <memory>
+
+#include "rocksdb/env.h"
+#include "rocksdb/concurrent_task_limiter.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class TaskLimiterToken;
+
+class ConcurrentTaskLimiterImpl : public ConcurrentTaskLimiter {
+ public:
+  explicit ConcurrentTaskLimiterImpl(const std::string& name,
+                                     int32_t max_outstanding_task);
+  // No copying allowed
+  ConcurrentTaskLimiterImpl(const ConcurrentTaskLimiterImpl&) = delete;
+  ConcurrentTaskLimiterImpl& operator=(const ConcurrentTaskLimiterImpl&) =
+      delete;
+
+  virtual ~ConcurrentTaskLimiterImpl();
+
+  virtual const std::string& GetName() const override;
+
+  virtual void SetMaxOutstandingTask(int32_t limit) override;
+
+  virtual void ResetMaxOutstandingTask() override;
+
+  virtual int32_t GetOutstandingTask() const override;
+
+  // Request token for adding a new task.
+  // If force == true, it requests a token bypassing throttle.
+  // Returns nullptr if it got throttled.
+  virtual std::unique_ptr<TaskLimiterToken> GetToken(bool force);
+
+ private:
+  friend class TaskLimiterToken;
+
+  std::string name_;
+  std::atomic<int32_t> max_outstanding_tasks_;
+  std::atomic<int32_t> outstanding_tasks_;
+};
+
+class TaskLimiterToken {
+ public:
+  explicit TaskLimiterToken(ConcurrentTaskLimiterImpl* limiter)
+      : limiter_(limiter) {}
+  ~TaskLimiterToken();
+
+ private:
+  ConcurrentTaskLimiterImpl* limiter_;
+
+  // no copying allowed
+  TaskLimiterToken(const TaskLimiterToken&) = delete;
+  void operator=(const TaskLimiterToken&) = delete;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/core_local.h b/src/rocksdb/util/core_local.h
new file mode 100644
index 000000000..b444a1152
--- /dev/null
+++ b/src/rocksdb/util/core_local.h
@@ -0,0 +1,83 @@
+//  Copyright (c) 2017-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <cstddef>
+#include <thread>
+#include <utility>
+#include <vector>
+
+#include "port/likely.h"
+#include "port/port.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// An array of core-local values. Ideally the value type, T, is cache aligned to
+// prevent false sharing.
+template <typename T>
+class CoreLocalArray {
+ public:
+  CoreLocalArray();
+
+  size_t Size() const;
+  // returns pointer to the element corresponding to the core that the thread
+  // currently runs on.
+  T* Access() const;
+  // same as above, but also returns the core index, which the client can cache
+  // to reduce how often core ID needs to be retrieved. Only do this if some
+  // inaccuracy is tolerable, as the thread may migrate to a different core.
+  std::pair<T*, size_t> AccessElementAndIndex() const;
+  // returns pointer to element for the specified core index. This can be used,
+  // e.g., for aggregation, or if the client caches core index.
+  T* AccessAtCore(size_t core_idx) const;
+
+ private:
+  std::unique_ptr<T[]> data_;
+  int size_shift_;
+};
+
+template <typename T>
+CoreLocalArray<T>::CoreLocalArray() {
+  int num_cpus = static_cast<int>(std::thread::hardware_concurrency());
+  // find a power of two >= num_cpus and >= 8
+  size_shift_ = 3;
+  while (1 << size_shift_ < num_cpus) {
+    ++size_shift_;
+  }
+  data_.reset(new T[static_cast<size_t>(1) << size_shift_]);
+}
+
+template <typename T>
+size_t CoreLocalArray<T>::Size() const {
+  return static_cast<size_t>(1) << size_shift_;
+}
+
+template <typename T>
+T* CoreLocalArray<T>::Access() const {
+  return AccessElementAndIndex().first;
+}
+
+template <typename T>
+std::pair<T*, size_t> CoreLocalArray<T>::AccessElementAndIndex() const {
+  int cpuid = port::PhysicalCoreID();
+  size_t core_idx;
+  if (UNLIKELY(cpuid < 0)) {
+    // cpu id unavailable, just pick randomly
+    core_idx = Random::GetTLSInstance()->Uniform(1 << size_shift_);
+  } else {
+    core_idx = static_cast<size_t>(cpuid & ((1 << size_shift_) - 1));
+  }
+  return {AccessAtCore(core_idx), core_idx};
+}
+
+template <typename T>
+T* CoreLocalArray<T>::AccessAtCore(size_t core_idx) const {
+  assert(core_idx < static_cast<size_t>(1) << size_shift_);
+  return &data_[core_idx];
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/crc32c.cc b/src/rocksdb/util/crc32c.cc
new file mode 100644
index 000000000..f0eee2f4f
--- /dev/null
+++ b/src/rocksdb/util/crc32c.cc
@@ -0,0 +1,1263 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A portable implementation of crc32c, optimized to handle
+// four bytes at a time.
+#include "util/crc32c.h"
+#include <stdint.h>
+#ifdef HAVE_SSE42
+#include <nmmintrin.h>
+#include <wmmintrin.h>
+#endif
+#include "util/coding.h"
+#include "util/util.h"
+
+#include "util/crc32c_arm64.h"
+
+#ifdef __powerpc64__
+#include "util/crc32c_ppc.h"
+#include "util/crc32c_ppc_constants.h"
+
+#if __linux__
+#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
+#include <sys/auxv.h>
+#endif
+
+#ifndef PPC_FEATURE2_VEC_CRYPTO
+#define PPC_FEATURE2_VEC_CRYPTO 0x02000000
+#endif
+
+#ifndef AT_HWCAP2
+#define AT_HWCAP2 26
+#endif
+
+#endif /* __linux__ */
+
+#endif
+
+#if defined(__linux__) && defined(HAVE_ARM64_CRC)
+bool pmull_runtime_flag = false;
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+namespace crc32c {
+
+#if defined(HAVE_POWER8) && defined(HAS_ALTIVEC)
+#ifdef __powerpc64__
+static int arch_ppc_crc32 = 0;
+#endif /* __powerpc64__ */
+#endif
+
+static const uint32_t table0_[256] = {
+  0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4,
+  0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
+  0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
+  0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
+  0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b,
+  0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+  0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54,
+  0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
+  0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
+  0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
+  0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5,
+  0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+  0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45,
+  0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
+  0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
+  0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
+  0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48,
+  0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+  0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687,
+  0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
+  0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
+  0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
+  0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8,
+  0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+  0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096,
+  0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
+  0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
+  0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
+  0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9,
+  0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+  0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36,
+  0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
+  0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
+  0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
+  0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043,
+  0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+  0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3,
+  0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
+  0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
+  0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
+  0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652,
+  0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+  0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d,
+  0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
+  0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
+  0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
+  0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2,
+  0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+  0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530,
+  0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
+  0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
+  0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
+  0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f,
+  0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+  0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90,
+  0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
+  0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
+  0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
+  0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321,
+  0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+  0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81,
+  0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
+  0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
+  0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351
+};
+static const uint32_t table1_[256] = {
+  0x00000000, 0x13a29877, 0x274530ee, 0x34e7a899,
+  0x4e8a61dc, 0x5d28f9ab, 0x69cf5132, 0x7a6dc945,
+  0x9d14c3b8, 0x8eb65bcf, 0xba51f356, 0xa9f36b21,
+  0xd39ea264, 0xc03c3a13, 0xf4db928a, 0xe7790afd,
+  0x3fc5f181, 0x2c6769f6, 0x1880c16f, 0x0b225918,
+  0x714f905d, 0x62ed082a, 0x560aa0b3, 0x45a838c4,
+  0xa2d13239, 0xb173aa4e, 0x859402d7, 0x96369aa0,
+  0xec5b53e5, 0xfff9cb92, 0xcb1e630b, 0xd8bcfb7c,
+  0x7f8be302, 0x6c297b75, 0x58ced3ec, 0x4b6c4b9b,
+  0x310182de, 0x22a31aa9, 0x1644b230, 0x05e62a47,
+  0xe29f20ba, 0xf13db8cd, 0xc5da1054, 0xd6788823,
+  0xac154166, 0xbfb7d911, 0x8b507188, 0x98f2e9ff,
+  0x404e1283, 0x53ec8af4, 0x670b226d, 0x74a9ba1a,
+  0x0ec4735f, 0x1d66eb28, 0x298143b1, 0x3a23dbc6,
+  0xdd5ad13b, 0xcef8494c, 0xfa1fe1d5, 0xe9bd79a2,
+  0x93d0b0e7, 0x80722890, 0xb4958009, 0xa737187e,
+  0xff17c604, 0xecb55e73, 0xd852f6ea, 0xcbf06e9d,
+  0xb19da7d8, 0xa23f3faf, 0x96d89736, 0x857a0f41,
+  0x620305bc, 0x71a19dcb, 0x45463552, 0x56e4ad25,
+  0x2c896460, 0x3f2bfc17, 0x0bcc548e, 0x186eccf9,
+  0xc0d23785, 0xd370aff2, 0xe797076b, 0xf4359f1c,
+  0x8e585659, 0x9dface2e, 0xa91d66b7, 0xbabffec0,
+  0x5dc6f43d, 0x4e646c4a, 0x7a83c4d3, 0x69215ca4,
+  0x134c95e1, 0x00ee0d96, 0x3409a50f, 0x27ab3d78,
+  0x809c2506, 0x933ebd71, 0xa7d915e8, 0xb47b8d9f,
+  0xce1644da, 0xddb4dcad, 0xe9537434, 0xfaf1ec43,
+  0x1d88e6be, 0x0e2a7ec9, 0x3acdd650, 0x296f4e27,
+  0x53028762, 0x40a01f15, 0x7447b78c, 0x67e52ffb,
+  0xbf59d487, 0xacfb4cf0, 0x981ce469, 0x8bbe7c1e,
+  0xf1d3b55b, 0xe2712d2c, 0xd69685b5, 0xc5341dc2,
+  0x224d173f, 0x31ef8f48, 0x050827d1, 0x16aabfa6,
+  0x6cc776e3, 0x7f65ee94, 0x4b82460d, 0x5820de7a,
+  0xfbc3faf9, 0xe861628e, 0xdc86ca17, 0xcf245260,
+  0xb5499b25, 0xa6eb0352, 0x920cabcb, 0x81ae33bc,
+  0x66d73941, 0x7575a136, 0x419209af, 0x523091d8,
+  0x285d589d, 0x3bffc0ea, 0x0f186873, 0x1cbaf004,
+  0xc4060b78, 0xd7a4930f, 0xe3433b96, 0xf0e1a3e1,
+  0x8a8c6aa4, 0x992ef2d3, 0xadc95a4a, 0xbe6bc23d,
+  0x5912c8c0, 0x4ab050b7, 0x7e57f82e, 0x6df56059,
+  0x1798a91c, 0x043a316b, 0x30dd99f2, 0x237f0185,
+  0x844819fb, 0x97ea818c, 0xa30d2915, 0xb0afb162,
+  0xcac27827, 0xd960e050, 0xed8748c9, 0xfe25d0be,
+  0x195cda43, 0x0afe4234, 0x3e19eaad, 0x2dbb72da,
+  0x57d6bb9f, 0x447423e8, 0x70938b71, 0x63311306,
+  0xbb8de87a, 0xa82f700d, 0x9cc8d894, 0x8f6a40e3,
+  0xf50789a6, 0xe6a511d1, 0xd242b948, 0xc1e0213f,
+  0x26992bc2, 0x353bb3b5, 0x01dc1b2c, 0x127e835b,
+  0x68134a1e, 0x7bb1d269, 0x4f567af0, 0x5cf4e287,
+  0x04d43cfd, 0x1776a48a, 0x23910c13, 0x30339464,
+  0x4a5e5d21, 0x59fcc556, 0x6d1b6dcf, 0x7eb9f5b8,
+  0x99c0ff45, 0x8a626732, 0xbe85cfab, 0xad2757dc,
+  0xd74a9e99, 0xc4e806ee, 0xf00fae77, 0xe3ad3600,
+  0x3b11cd7c, 0x28b3550b, 0x1c54fd92, 0x0ff665e5,
+  0x759baca0, 0x663934d7, 0x52de9c4e, 0x417c0439,
+  0xa6050ec4, 0xb5a796b3, 0x81403e2a, 0x92e2a65d,
+  0xe88f6f18, 0xfb2df76f, 0xcfca5ff6, 0xdc68c781,
+  0x7b5fdfff, 0x68fd4788, 0x5c1aef11, 0x4fb87766,
+  0x35d5be23, 0x26772654, 0x12908ecd, 0x013216ba,
+  0xe64b1c47, 0xf5e98430, 0xc10e2ca9, 0xd2acb4de,
+  0xa8c17d9b, 0xbb63e5ec, 0x8f844d75, 0x9c26d502,
+  0x449a2e7e, 0x5738b609, 0x63df1e90, 0x707d86e7,
+  0x0a104fa2, 0x19b2d7d5, 0x2d557f4c, 0x3ef7e73b,
+  0xd98eedc6, 0xca2c75b1, 0xfecbdd28, 0xed69455f,
+  0x97048c1a, 0x84a6146d, 0xb041bcf4, 0xa3e32483
+};
+static const uint32_t table2_[256] = {
+  0x00000000, 0xa541927e, 0x4f6f520d, 0xea2ec073,
+  0x9edea41a, 0x3b9f3664, 0xd1b1f617, 0x74f06469,
+  0x38513ec5, 0x9d10acbb, 0x773e6cc8, 0xd27ffeb6,
+  0xa68f9adf, 0x03ce08a1, 0xe9e0c8d2, 0x4ca15aac,
+  0x70a27d8a, 0xd5e3eff4, 0x3fcd2f87, 0x9a8cbdf9,
+  0xee7cd990, 0x4b3d4bee, 0xa1138b9d, 0x045219e3,
+  0x48f3434f, 0xedb2d131, 0x079c1142, 0xa2dd833c,
+  0xd62de755, 0x736c752b, 0x9942b558, 0x3c032726,
+  0xe144fb14, 0x4405696a, 0xae2ba919, 0x0b6a3b67,
+  0x7f9a5f0e, 0xdadbcd70, 0x30f50d03, 0x95b49f7d,
+  0xd915c5d1, 0x7c5457af, 0x967a97dc, 0x333b05a2,
+  0x47cb61cb, 0xe28af3b5, 0x08a433c6, 0xade5a1b8,
+  0x91e6869e, 0x34a714e0, 0xde89d493, 0x7bc846ed,
+  0x0f382284, 0xaa79b0fa, 0x40577089, 0xe516e2f7,
+  0xa9b7b85b, 0x0cf62a25, 0xe6d8ea56, 0x43997828,
+  0x37691c41, 0x92288e3f, 0x78064e4c, 0xdd47dc32,
+  0xc76580d9, 0x622412a7, 0x880ad2d4, 0x2d4b40aa,
+  0x59bb24c3, 0xfcfab6bd, 0x16d476ce, 0xb395e4b0,
+  0xff34be1c, 0x5a752c62, 0xb05bec11, 0x151a7e6f,
+  0x61ea1a06, 0xc4ab8878, 0x2e85480b, 0x8bc4da75,
+  0xb7c7fd53, 0x12866f2d, 0xf8a8af5e, 0x5de93d20,
+  0x29195949, 0x8c58cb37, 0x66760b44, 0xc337993a,
+  0x8f96c396, 0x2ad751e8, 0xc0f9919b, 0x65b803e5,
+  0x1148678c, 0xb409f5f2, 0x5e273581, 0xfb66a7ff,
+  0x26217bcd, 0x8360e9b3, 0x694e29c0, 0xcc0fbbbe,
+  0xb8ffdfd7, 0x1dbe4da9, 0xf7908dda, 0x52d11fa4,
+  0x1e704508, 0xbb31d776, 0x511f1705, 0xf45e857b,
+  0x80aee112, 0x25ef736c, 0xcfc1b31f, 0x6a802161,
+  0x56830647, 0xf3c29439, 0x19ec544a, 0xbcadc634,
+  0xc85da25d, 0x6d1c3023, 0x8732f050, 0x2273622e,
+  0x6ed23882, 0xcb93aafc, 0x21bd6a8f, 0x84fcf8f1,
+  0xf00c9c98, 0x554d0ee6, 0xbf63ce95, 0x1a225ceb,
+  0x8b277743, 0x2e66e53d, 0xc448254e, 0x6109b730,
+  0x15f9d359, 0xb0b84127, 0x5a968154, 0xffd7132a,
+  0xb3764986, 0x1637dbf8, 0xfc191b8b, 0x595889f5,
+  0x2da8ed9c, 0x88e97fe2, 0x62c7bf91, 0xc7862def,
+  0xfb850ac9, 0x5ec498b7, 0xb4ea58c4, 0x11abcaba,
+  0x655baed3, 0xc01a3cad, 0x2a34fcde, 0x8f756ea0,
+  0xc3d4340c, 0x6695a672, 0x8cbb6601, 0x29faf47f,
+  0x5d0a9016, 0xf84b0268, 0x1265c21b, 0xb7245065,
+  0x6a638c57, 0xcf221e29, 0x250cde5a, 0x804d4c24,
+  0xf4bd284d, 0x51fcba33, 0xbbd27a40, 0x1e93e83e,
+  0x5232b292, 0xf77320ec, 0x1d5de09f, 0xb81c72e1,
+  0xccec1688, 0x69ad84f6, 0x83834485, 0x26c2d6fb,
+  0x1ac1f1dd, 0xbf8063a3, 0x55aea3d0, 0xf0ef31ae,
+  0x841f55c7, 0x215ec7b9, 0xcb7007ca, 0x6e3195b4,
+  0x2290cf18, 0x87d15d66, 0x6dff9d15, 0xc8be0f6b,
+  0xbc4e6b02, 0x190ff97c, 0xf321390f, 0x5660ab71,
+  0x4c42f79a, 0xe90365e4, 0x032da597, 0xa66c37e9,
+  0xd29c5380, 0x77ddc1fe, 0x9df3018d, 0x38b293f3,
+  0x7413c95f, 0xd1525b21, 0x3b7c9b52, 0x9e3d092c,
+  0xeacd6d45, 0x4f8cff3b, 0xa5a23f48, 0x00e3ad36,
+  0x3ce08a10, 0x99a1186e, 0x738fd81d, 0xd6ce4a63,
+  0xa23e2e0a, 0x077fbc74, 0xed517c07, 0x4810ee79,
+  0x04b1b4d5, 0xa1f026ab, 0x4bdee6d8, 0xee9f74a6,
+  0x9a6f10cf, 0x3f2e82b1, 0xd50042c2, 0x7041d0bc,
+  0xad060c8e, 0x08479ef0, 0xe2695e83, 0x4728ccfd,
+  0x33d8a894, 0x96993aea, 0x7cb7fa99, 0xd9f668e7,
+  0x9557324b, 0x3016a035, 0xda386046, 0x7f79f238,
+  0x0b899651, 0xaec8042f, 0x44e6c45c, 0xe1a75622,
+  0xdda47104, 0x78e5e37a, 0x92cb2309, 0x378ab177,
+  0x437ad51e, 0xe63b4760, 0x0c158713, 0xa954156d,
+  0xe5f54fc1, 0x40b4ddbf, 0xaa9a1dcc, 0x0fdb8fb2,
+  0x7b2bebdb, 0xde6a79a5, 0x3444b9d6, 0x91052ba8
+};
+static const uint32_t table3_[256] = {
+  0x00000000, 0xdd45aab8, 0xbf672381, 0x62228939,
+  0x7b2231f3, 0xa6679b4b, 0xc4451272, 0x1900b8ca,
+  0xf64463e6, 0x2b01c95e, 0x49234067, 0x9466eadf,
+  0x8d665215, 0x5023f8ad, 0x32017194, 0xef44db2c,
+  0xe964b13d, 0x34211b85, 0x560392bc, 0x8b463804,
+  0x924680ce, 0x4f032a76, 0x2d21a34f, 0xf06409f7,
+  0x1f20d2db, 0xc2657863, 0xa047f15a, 0x7d025be2,
+  0x6402e328, 0xb9474990, 0xdb65c0a9, 0x06206a11,
+  0xd725148b, 0x0a60be33, 0x6842370a, 0xb5079db2,
+  0xac072578, 0x71428fc0, 0x136006f9, 0xce25ac41,
+  0x2161776d, 0xfc24ddd5, 0x9e0654ec, 0x4343fe54,
+  0x5a43469e, 0x8706ec26, 0xe524651f, 0x3861cfa7,
+  0x3e41a5b6, 0xe3040f0e, 0x81268637, 0x5c632c8f,
+  0x45639445, 0x98263efd, 0xfa04b7c4, 0x27411d7c,
+  0xc805c650, 0x15406ce8, 0x7762e5d1, 0xaa274f69,
+  0xb327f7a3, 0x6e625d1b, 0x0c40d422, 0xd1057e9a,
+  0xaba65fe7, 0x76e3f55f, 0x14c17c66, 0xc984d6de,
+  0xd0846e14, 0x0dc1c4ac, 0x6fe34d95, 0xb2a6e72d,
+  0x5de23c01, 0x80a796b9, 0xe2851f80, 0x3fc0b538,
+  0x26c00df2, 0xfb85a74a, 0x99a72e73, 0x44e284cb,
+  0x42c2eeda, 0x9f874462, 0xfda5cd5b, 0x20e067e3,
+  0x39e0df29, 0xe4a57591, 0x8687fca8, 0x5bc25610,
+  0xb4868d3c, 0x69c32784, 0x0be1aebd, 0xd6a40405,
+  0xcfa4bccf, 0x12e11677, 0x70c39f4e, 0xad8635f6,
+  0x7c834b6c, 0xa1c6e1d4, 0xc3e468ed, 0x1ea1c255,
+  0x07a17a9f, 0xdae4d027, 0xb8c6591e, 0x6583f3a6,
+  0x8ac7288a, 0x57828232, 0x35a00b0b, 0xe8e5a1b3,
+  0xf1e51979, 0x2ca0b3c1, 0x4e823af8, 0x93c79040,
+  0x95e7fa51, 0x48a250e9, 0x2a80d9d0, 0xf7c57368,
+  0xeec5cba2, 0x3380611a, 0x51a2e823, 0x8ce7429b,
+  0x63a399b7, 0xbee6330f, 0xdcc4ba36, 0x0181108e,
+  0x1881a844, 0xc5c402fc, 0xa7e68bc5, 0x7aa3217d,
+  0x52a0c93f, 0x8fe56387, 0xedc7eabe, 0x30824006,
+  0x2982f8cc, 0xf4c75274, 0x96e5db4d, 0x4ba071f5,
+  0xa4e4aad9, 0x79a10061, 0x1b838958, 0xc6c623e0,
+  0xdfc69b2a, 0x02833192, 0x60a1b8ab, 0xbde41213,
+  0xbbc47802, 0x6681d2ba, 0x04a35b83, 0xd9e6f13b,
+  0xc0e649f1, 0x1da3e349, 0x7f816a70, 0xa2c4c0c8,
+  0x4d801be4, 0x90c5b15c, 0xf2e73865, 0x2fa292dd,
+  0x36a22a17, 0xebe780af, 0x89c50996, 0x5480a32e,
+  0x8585ddb4, 0x58c0770c, 0x3ae2fe35, 0xe7a7548d,
+  0xfea7ec47, 0x23e246ff, 0x41c0cfc6, 0x9c85657e,
+  0x73c1be52, 0xae8414ea, 0xcca69dd3, 0x11e3376b,
+  0x08e38fa1, 0xd5a62519, 0xb784ac20, 0x6ac10698,
+  0x6ce16c89, 0xb1a4c631, 0xd3864f08, 0x0ec3e5b0,
+  0x17c35d7a, 0xca86f7c2, 0xa8a47efb, 0x75e1d443,
+  0x9aa50f6f, 0x47e0a5d7, 0x25c22cee, 0xf8878656,
+  0xe1873e9c, 0x3cc29424, 0x5ee01d1d, 0x83a5b7a5,
+  0xf90696d8, 0x24433c60, 0x4661b559, 0x9b241fe1,
+  0x8224a72b, 0x5f610d93, 0x3d4384aa, 0xe0062e12,
+  0x0f42f53e, 0xd2075f86, 0xb025d6bf, 0x6d607c07,
+  0x7460c4cd, 0xa9256e75, 0xcb07e74c, 0x16424df4,
+  0x106227e5, 0xcd278d5d, 0xaf050464, 0x7240aedc,
+  0x6b401616, 0xb605bcae, 0xd4273597, 0x09629f2f,
+  0xe6264403, 0x3b63eebb, 0x59416782, 0x8404cd3a,
+  0x9d0475f0, 0x4041df48, 0x22635671, 0xff26fcc9,
+  0x2e238253, 0xf36628eb, 0x9144a1d2, 0x4c010b6a,
+  0x5501b3a0, 0x88441918, 0xea669021, 0x37233a99,
+  0xd867e1b5, 0x05224b0d, 0x6700c234, 0xba45688c,
+  0xa345d046, 0x7e007afe, 0x1c22f3c7, 0xc167597f,
+  0xc747336e, 0x1a0299d6, 0x782010ef, 0xa565ba57,
+  0xbc65029d, 0x6120a825, 0x0302211c, 0xde478ba4,
+  0x31035088, 0xec46fa30, 0x8e647309, 0x5321d9b1,
+  0x4a21617b, 0x9764cbc3, 0xf54642fa, 0x2803e842
+};
+
+// Used to fetch a naturally-aligned 32-bit word in little endian byte-order
+static inline uint32_t LE_LOAD32(const uint8_t *p) {
+  return DecodeFixed32(reinterpret_cast<const char*>(p));
+}
+
+#if defined(HAVE_SSE42) && (defined(__LP64__) || defined(_WIN64))
+static inline uint64_t LE_LOAD64(const uint8_t *p) {
+  return DecodeFixed64(reinterpret_cast<const char*>(p));
+}
+#endif
+
+static inline void Slow_CRC32(uint64_t* l, uint8_t const **p) {
+  uint32_t c = static_cast<uint32_t>(*l ^ LE_LOAD32(*p));
+  *p += 4;
+  *l = table3_[c & 0xff] ^
+  table2_[(c >> 8) & 0xff] ^
+  table1_[(c >> 16) & 0xff] ^
+  table0_[c >> 24];
+  // DO it twice.
+  c = static_cast<uint32_t>(*l ^ LE_LOAD32(*p));
+  *p += 4;
+  *l = table3_[c & 0xff] ^
+  table2_[(c >> 8) & 0xff] ^
+  table1_[(c >> 16) & 0xff] ^
+  table0_[c >> 24];
+}
+
+static inline void Fast_CRC32(uint64_t* l, uint8_t const **p) {
+#ifndef HAVE_SSE42
+  Slow_CRC32(l, p);
+#elif defined(__LP64__) || defined(_WIN64)
+  *l = _mm_crc32_u64(*l, LE_LOAD64(*p));
+  *p += 8;
+#else
+  *l = _mm_crc32_u32(static_cast<unsigned int>(*l), LE_LOAD32(*p));
+  *p += 4;
+  *l = _mm_crc32_u32(static_cast<unsigned int>(*l), LE_LOAD32(*p));
+  *p += 4;
+#endif
+}
+
+template<void (*CRC32)(uint64_t*, uint8_t const**)>
+uint32_t ExtendImpl(uint32_t crc, const char* buf, size_t size) {
+
+  const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
+  const uint8_t *e = p + size;
+  uint64_t l = crc ^ 0xffffffffu;
+
+// Align n to (1 << m) byte boundary
+#define ALIGN(n, m)     ((n + ((1 << m) - 1)) & ~((1 << m) - 1))
+
+#define STEP1 do {                              \
+    int c = (l & 0xff) ^ *p++;                  \
+    l = table0_[c] ^ (l >> 8);                  \
+} while (0)
+
+
+  // Point x at first 16-byte aligned byte in string.  This might be
+  // just past the end of the string.
+  const uintptr_t pval = reinterpret_cast<uintptr_t>(p);
+  const uint8_t* x = reinterpret_cast<const uint8_t*>(ALIGN(pval, 4));
+  if (x <= e) {
+    // Process bytes until finished or p is 16-byte aligned
+    while (p != x) {
+      STEP1;
+    }
+  }
+  // Process bytes 16 at a time
+  while ((e-p) >= 16) {
+    CRC32(&l, &p);
+    CRC32(&l, &p);
+  }
+  // Process bytes 8 at a time
+  while ((e-p) >= 8) {
+    CRC32(&l, &p);
+  }
+  // Process the last few bytes
+  while (p != e) {
+    STEP1;
+  }
+#undef STEP1
+#undef ALIGN
+  return static_cast<uint32_t>(l ^ 0xffffffffu);
+}
+
+// Detect if ARM64 CRC or not.
+#ifndef HAVE_ARM64_CRC
+// Detect if SS42 or not.
+#ifndef HAVE_POWER8
+
+static bool isSSE42() {
+#ifndef HAVE_SSE42
+  return false;
+#elif defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
+  uint32_t c_;
+  __asm__("cpuid" : "=c"(c_) : "a"(1) : "ebx", "edx");
+  return c_ & (1U << 20);  // copied from CpuId.h in Folly. Test SSE42
+#elif defined(_WIN64)
+  int info[4];
+  __cpuidex(info, 0x00000001, 0);
+  return (info[2] & ((int)1 << 20)) != 0;
+#else
+  return false;
+#endif
+}
+
+static bool isPCLMULQDQ() {
+#ifndef HAVE_SSE42
+// in build_detect_platform we set this macro when both SSE42 and PCLMULQDQ are
+// supported by compiler
+  return false;
+#elif defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
+  uint32_t c_;
+  __asm__("cpuid" : "=c"(c_) : "a"(1) : "ebx", "edx");
+  return c_ & (1U << 1);  // PCLMULQDQ is in bit 1 (not bit 0)
+#elif defined(_WIN64)
+  int info[4];
+  __cpuidex(info, 0x00000001, 0);
+  return (info[2] & ((int)1 << 1)) != 0;
+#else
+  return false;
+#endif
+}
+
+#endif  // HAVE_POWER8
+#endif  // HAVE_ARM64_CRC
+
+typedef uint32_t (*Function)(uint32_t, const char*, size_t);
+
+#if defined(HAVE_POWER8) && defined(HAS_ALTIVEC)
+uint32_t ExtendPPCImpl(uint32_t crc, const char *buf, size_t size) {
+  return crc32c_ppc(crc, (const unsigned char *)buf, size);
+}
+
+#if __linux__
+static int arch_ppc_probe(void) {
+  arch_ppc_crc32 = 0;
+
+#if defined(__powerpc64__) && defined(ROCKSDB_AUXV_GETAUXVAL_PRESENT)
+  if (getauxval(AT_HWCAP2) & PPC_FEATURE2_VEC_CRYPTO) arch_ppc_crc32 = 1;
+#endif /* __powerpc64__ */
+
+  return arch_ppc_crc32;
+}
+#endif  // __linux__
+
+static bool isAltiVec() {
+  if (arch_ppc_probe()) {
+    return true;
+  } else {
+    return false;
+  }
+}
+#endif
+
+#if defined(__linux__) && defined(HAVE_ARM64_CRC)
+uint32_t ExtendARMImpl(uint32_t crc, const char *buf, size_t size) {
+  return crc32c_arm64(crc, (const unsigned char *)buf, size);
+}
+#endif
+
+std::string IsFastCrc32Supported() {
+  bool has_fast_crc = false;
+  std::string fast_zero_msg;
+  std::string arch;
+#ifdef HAVE_POWER8
+#ifdef HAS_ALTIVEC
+  if (arch_ppc_probe()) {
+    has_fast_crc = true;
+    arch = "PPC";
+  }
+#else
+  has_fast_crc = false;
+  arch = "PPC";
+#endif
+#elif defined(__linux__) && defined(HAVE_ARM64_CRC)
+  if (crc32c_runtime_check()) {
+    has_fast_crc = true;
+    arch = "Arm64";
+    pmull_runtime_flag = crc32c_pmull_runtime_check();
+  } else {
+    has_fast_crc = false;
+    arch = "Arm64";
+  }
+#else
+  has_fast_crc = isSSE42();
+  arch = "x86";
+#endif
+  if (has_fast_crc) {
+    fast_zero_msg.append("Supported on " + arch);
+  }
+  else {
+    fast_zero_msg.append("Not supported on " + arch);
+  }
+  return fast_zero_msg;
+}
+
+
+/*
+ * Copyright 2016 Ferry Toth, Exalon Delft BV, The Netherlands
+ *  This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the author be held liable for any damages
+ * arising from the use of this software.
+ *  Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *  1. The origin of this software must not be misrepresented; you must not
+ *   claim that you wrote the original software. If you use this software
+ *   in a product, an acknowledgment in the product documentation would be
+ *   appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *   misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ *  Ferry Toth
+ * ftoth@exalondelft.nl
+ *
+ * https://github.com/htot/crc32c
+ *
+ * Modified by Facebook
+ *
+ * Original intel whitepaper:
+ * "Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction"
+ * https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/crc-iscsi-polynomial-crc32-instruction-paper.pdf
+ *
+ * This version is from the folly library, created by Dave Watson <davejwatson@fb.com>
+ *
+*/
+#if defined HAVE_SSE42 && defined HAVE_PCLMUL
+
+#define CRCtriplet(crc, buf, offset)                  \
+  crc##0 = _mm_crc32_u64(crc##0, *(buf##0 + offset)); \
+  crc##1 = _mm_crc32_u64(crc##1, *(buf##1 + offset)); \
+  crc##2 = _mm_crc32_u64(crc##2, *(buf##2 + offset));
+
+#define CRCduplet(crc, buf, offset)                   \
+  crc##0 = _mm_crc32_u64(crc##0, *(buf##0 + offset)); \
+  crc##1 = _mm_crc32_u64(crc##1, *(buf##1 + offset));
+
+#define CRCsinglet(crc, buf, offset)                    \
+  crc = _mm_crc32_u64(crc, *(uint64_t*)(buf + offset));
+
+
+// Numbers taken directly from intel whitepaper.
+// clang-format off
+const uint64_t clmul_constants[] = {
+    0x14cd00bd6, 0x105ec76f0, 0x0ba4fc28e, 0x14cd00bd6,
+    0x1d82c63da, 0x0f20c0dfe, 0x09e4addf8, 0x0ba4fc28e,
+    0x039d3b296, 0x1384aa63a, 0x102f9b8a2, 0x1d82c63da,
+    0x14237f5e6, 0x01c291d04, 0x00d3b6092, 0x09e4addf8,
+    0x0c96cfdc0, 0x0740eef02, 0x18266e456, 0x039d3b296,
+    0x0daece73e, 0x0083a6eec, 0x0ab7aff2a, 0x102f9b8a2,
+    0x1248ea574, 0x1c1733996, 0x083348832, 0x14237f5e6,
+    0x12c743124, 0x02ad91c30, 0x0b9e02b86, 0x00d3b6092,
+    0x018b33a4e, 0x06992cea2, 0x1b331e26a, 0x0c96cfdc0,
+    0x17d35ba46, 0x07e908048, 0x1bf2e8b8a, 0x18266e456,
+    0x1a3e0968a, 0x11ed1f9d8, 0x0ce7f39f4, 0x0daece73e,
+    0x061d82e56, 0x0f1d0f55e, 0x0d270f1a2, 0x0ab7aff2a,
+    0x1c3f5f66c, 0x0a87ab8a8, 0x12ed0daac, 0x1248ea574,
+    0x065863b64, 0x08462d800, 0x11eef4f8e, 0x083348832,
+    0x1ee54f54c, 0x071d111a8, 0x0b3e32c28, 0x12c743124,
+    0x0064f7f26, 0x0ffd852c6, 0x0dd7e3b0c, 0x0b9e02b86,
+    0x0f285651c, 0x0dcb17aa4, 0x010746f3c, 0x018b33a4e,
+    0x1c24afea4, 0x0f37c5aee, 0x0271d9844, 0x1b331e26a,
+    0x08e766a0c, 0x06051d5a2, 0x093a5f730, 0x17d35ba46,
+    0x06cb08e5c, 0x11d5ca20e, 0x06b749fb2, 0x1bf2e8b8a,
+    0x1167f94f2, 0x021f3d99c, 0x0cec3662e, 0x1a3e0968a,
+    0x19329634a, 0x08f158014, 0x0e6fc4e6a, 0x0ce7f39f4,
+    0x08227bb8a, 0x1a5e82106, 0x0b0cd4768, 0x061d82e56,
+    0x13c2b89c4, 0x188815ab2, 0x0d7a4825c, 0x0d270f1a2,
+    0x10f5ff2ba, 0x105405f3e, 0x00167d312, 0x1c3f5f66c,
+    0x0f6076544, 0x0e9adf796, 0x026f6a60a, 0x12ed0daac,
+    0x1a2adb74e, 0x096638b34, 0x19d34af3a, 0x065863b64,
+    0x049c3cc9c, 0x1e50585a0, 0x068bce87a, 0x11eef4f8e,
+    0x1524fa6c6, 0x19f1c69dc, 0x16cba8aca, 0x1ee54f54c,
+    0x042d98888, 0x12913343e, 0x1329d9f7e, 0x0b3e32c28,
+    0x1b1c69528, 0x088f25a3a, 0x02178513a, 0x0064f7f26,
+    0x0e0ac139e, 0x04e36f0b0, 0x0170076fa, 0x0dd7e3b0c,
+    0x141a1a2e2, 0x0bd6f81f8, 0x16ad828b4, 0x0f285651c,
+    0x041d17b64, 0x19425cbba, 0x1fae1cc66, 0x010746f3c,
+    0x1a75b4b00, 0x18db37e8a, 0x0f872e54c, 0x1c24afea4,
+    0x01e41e9fc, 0x04c144932, 0x086d8e4d2, 0x0271d9844,
+    0x160f7af7a, 0x052148f02, 0x05bb8f1bc, 0x08e766a0c,
+    0x0a90fd27a, 0x0a3c6f37a, 0x0b3af077a, 0x093a5f730,
+    0x04984d782, 0x1d22c238e, 0x0ca6ef3ac, 0x06cb08e5c,
+    0x0234e0b26, 0x063ded06a, 0x1d88abd4a, 0x06b749fb2,
+    0x04597456a, 0x04d56973c, 0x0e9e28eb4, 0x1167f94f2,
+    0x07b3ff57a, 0x19385bf2e, 0x0c9c8b782, 0x0cec3662e,
+    0x13a9cba9e, 0x0e417f38a, 0x093e106a4, 0x19329634a,
+    0x167001a9c, 0x14e727980, 0x1ddffc5d4, 0x0e6fc4e6a,
+    0x00df04680, 0x0d104b8fc, 0x02342001e, 0x08227bb8a,
+    0x00a2a8d7e, 0x05b397730, 0x168763fa6, 0x0b0cd4768,
+    0x1ed5a407a, 0x0e78eb416, 0x0d2c3ed1a, 0x13c2b89c4,
+    0x0995a5724, 0x1641378f0, 0x19b1afbc4, 0x0d7a4825c,
+    0x109ffedc0, 0x08d96551c, 0x0f2271e60, 0x10f5ff2ba,
+    0x00b0bf8ca, 0x00bf80dd2, 0x123888b7a, 0x00167d312,
+    0x1e888f7dc, 0x18dcddd1c, 0x002ee03b2, 0x0f6076544,
+    0x183e8d8fe, 0x06a45d2b2, 0x133d7a042, 0x026f6a60a,
+    0x116b0f50c, 0x1dd3e10e8, 0x05fabe670, 0x1a2adb74e,
+    0x130004488, 0x0de87806c, 0x000bcf5f6, 0x19d34af3a,
+    0x18f0c7078, 0x014338754, 0x017f27698, 0x049c3cc9c,
+    0x058ca5f00, 0x15e3e77ee, 0x1af900c24, 0x068bce87a,
+    0x0b5cfca28, 0x0dd07448e, 0x0ded288f8, 0x1524fa6c6,
+    0x059f229bc, 0x1d8048348, 0x06d390dec, 0x16cba8aca,
+    0x037170390, 0x0a3e3e02c, 0x06353c1cc, 0x042d98888,
+    0x0c4584f5c, 0x0d73c7bea, 0x1f16a3418, 0x1329d9f7e,
+    0x0531377e2, 0x185137662, 0x1d8d9ca7c, 0x1b1c69528,
+    0x0b25b29f2, 0x18a08b5bc, 0x19fb2a8b0, 0x02178513a,
+    0x1a08fe6ac, 0x1da758ae0, 0x045cddf4e, 0x0e0ac139e,
+    0x1a91647f2, 0x169cf9eb0, 0x1a0f717c4, 0x0170076fa,
+};
+
+// Compute the crc32c value for buffer smaller than 8
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+inline void align_to_8(
+    size_t len,
+    uint64_t& crc0, // crc so far, updated on return
+    const unsigned char*& next) { // next data pointer, updated on return
+  uint32_t crc32bit = static_cast<uint32_t>(crc0);
+  if (len & 0x04) {
+    crc32bit = _mm_crc32_u32(crc32bit, *(uint32_t*)next);
+    next += sizeof(uint32_t);
+  }
+  if (len & 0x02) {
+    crc32bit = _mm_crc32_u16(crc32bit, *(uint16_t*)next);
+    next += sizeof(uint16_t);
+  }
+  if (len & 0x01) {
+    crc32bit = _mm_crc32_u8(crc32bit, *(next));
+    next++;
+  }
+  crc0 = crc32bit;
+}
+
+//
+// CombineCRC performs pclmulqdq multiplication of 2 partial CRC's and a well
+// chosen constant and xor's these with the remaining CRC.
+//
+inline uint64_t CombineCRC(
+    size_t block_size,
+    uint64_t crc0,
+    uint64_t crc1,
+    uint64_t crc2,
+    const uint64_t* next2) {
+  const auto multiplier =
+      *(reinterpret_cast<const __m128i*>(clmul_constants) + block_size - 1);
+  const auto crc0_xmm = _mm_set_epi64x(0, crc0);
+  const auto res0 = _mm_clmulepi64_si128(crc0_xmm, multiplier, 0x00);
+  const auto crc1_xmm = _mm_set_epi64x(0, crc1);
+  const auto res1 = _mm_clmulepi64_si128(crc1_xmm, multiplier, 0x10);
+  const auto res = _mm_xor_si128(res0, res1);
+  crc0 = _mm_cvtsi128_si64(res);
+  crc0 = crc0 ^ *((uint64_t*)next2 - 1);
+  crc2 = _mm_crc32_u64(crc2, crc0);
+  return crc2;
+}
+
+// Compute CRC-32C using the Intel hardware instruction.
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+uint32_t crc32c_3way(uint32_t crc, const char* buf, size_t len) {
+  const unsigned char* next = (const unsigned char*)buf;
+  uint64_t count;
+  uint64_t crc0, crc1, crc2;
+  crc0 = crc ^ 0xffffffffu;
+
+
+  if (len >= 8) {
+    // if len > 216 then align and use triplets
+    if (len > 216) {
+      {
+        // Work on the bytes (< 8) before the first 8-byte alignment addr starts
+        uint64_t align_bytes = (8 - (uintptr_t)next) & 7;
+        len -= align_bytes;
+        align_to_8(align_bytes, crc0, next);
+      }
+
+      // Now work on the remaining blocks
+      count = len / 24; // number of triplets
+      len %= 24; // bytes remaining
+      uint64_t n = count >> 7; // #blocks = first block + full blocks
+      uint64_t block_size = count & 127;
+      if (block_size == 0) {
+        block_size = 128;
+      } else {
+        n++;
+      }
+      // points to the first byte of the next block
+      const uint64_t* next0 = (uint64_t*)next + block_size;
+      const uint64_t* next1 = next0 + block_size;
+      const uint64_t* next2 = next1 + block_size;
+
+      crc1 = crc2 = 0;
+      // Use Duff's device, a for() loop inside a switch()
+      // statement. This needs to execute at least once, round len
+      // down to nearest triplet multiple
+      switch (block_size) {
+        case 128:
+          do {
+            // jumps here for a full block of len 128
+            CRCtriplet(crc, next, -128);
+	    FALLTHROUGH_INTENDED;
+            case 127:
+              // jumps here or below for the first block smaller
+              CRCtriplet(crc, next, -127);
+	      FALLTHROUGH_INTENDED;
+            case 126:
+              CRCtriplet(crc, next, -126); // than 128
+	      FALLTHROUGH_INTENDED;
+            case 125:
+              CRCtriplet(crc, next, -125);
+	      FALLTHROUGH_INTENDED;
+            case 124:
+              CRCtriplet(crc, next, -124);
+	      FALLTHROUGH_INTENDED;
+            case 123:
+              CRCtriplet(crc, next, -123);
+	      FALLTHROUGH_INTENDED;
+            case 122:
+              CRCtriplet(crc, next, -122);
+	      FALLTHROUGH_INTENDED;
+            case 121:
+              CRCtriplet(crc, next, -121);
+	      FALLTHROUGH_INTENDED;
+            case 120:
+              CRCtriplet(crc, next, -120);
+              FALLTHROUGH_INTENDED;
+            case 119:
+              CRCtriplet(crc, next, -119);
+              FALLTHROUGH_INTENDED;
+            case 118:
+              CRCtriplet(crc, next, -118);
+              FALLTHROUGH_INTENDED;
+            case 117:
+              CRCtriplet(crc, next, -117);
+              FALLTHROUGH_INTENDED;
+            case 116:
+              CRCtriplet(crc, next, -116);
+              FALLTHROUGH_INTENDED;
+            case 115:
+              CRCtriplet(crc, next, -115);
+              FALLTHROUGH_INTENDED;
+            case 114:
+              CRCtriplet(crc, next, -114);
+              FALLTHROUGH_INTENDED;
+            case 113:
+              CRCtriplet(crc, next, -113);
+              FALLTHROUGH_INTENDED;
+            case 112:
+              CRCtriplet(crc, next, -112);
+              FALLTHROUGH_INTENDED;
+            case 111:
+              CRCtriplet(crc, next, -111);
+              FALLTHROUGH_INTENDED;
+            case 110:
+              CRCtriplet(crc, next, -110);
+              FALLTHROUGH_INTENDED;
+            case 109:
+              CRCtriplet(crc, next, -109);
+              FALLTHROUGH_INTENDED;
+            case 108:
+              CRCtriplet(crc, next, -108);
+              FALLTHROUGH_INTENDED;
+            case 107:
+              CRCtriplet(crc, next, -107);
+              FALLTHROUGH_INTENDED;
+            case 106:
+              CRCtriplet(crc, next, -106);
+              FALLTHROUGH_INTENDED;
+            case 105:
+              CRCtriplet(crc, next, -105);
+              FALLTHROUGH_INTENDED;
+            case 104:
+              CRCtriplet(crc, next, -104);
+              FALLTHROUGH_INTENDED;
+            case 103:
+              CRCtriplet(crc, next, -103);
+              FALLTHROUGH_INTENDED;
+            case 102:
+              CRCtriplet(crc, next, -102);
+              FALLTHROUGH_INTENDED;
+            case 101:
+              CRCtriplet(crc, next, -101);
+              FALLTHROUGH_INTENDED;
+            case 100:
+              CRCtriplet(crc, next, -100);
+              FALLTHROUGH_INTENDED;
+            case 99:
+              CRCtriplet(crc, next, -99);
+              FALLTHROUGH_INTENDED;
+            case 98:
+              CRCtriplet(crc, next, -98);
+              FALLTHROUGH_INTENDED;
+            case 97:
+              CRCtriplet(crc, next, -97);
+              FALLTHROUGH_INTENDED;
+            case 96:
+              CRCtriplet(crc, next, -96);
+              FALLTHROUGH_INTENDED;
+            case 95:
+              CRCtriplet(crc, next, -95);
+              FALLTHROUGH_INTENDED;
+            case 94:
+              CRCtriplet(crc, next, -94);
+              FALLTHROUGH_INTENDED;
+            case 93:
+              CRCtriplet(crc, next, -93);
+              FALLTHROUGH_INTENDED;
+            case 92:
+              CRCtriplet(crc, next, -92);
+              FALLTHROUGH_INTENDED;
+            case 91:
+              CRCtriplet(crc, next, -91);
+              FALLTHROUGH_INTENDED;
+            case 90:
+              CRCtriplet(crc, next, -90);
+              FALLTHROUGH_INTENDED;
+            case 89:
+              CRCtriplet(crc, next, -89);
+              FALLTHROUGH_INTENDED;
+            case 88:
+              CRCtriplet(crc, next, -88);
+              FALLTHROUGH_INTENDED;
+            case 87:
+              CRCtriplet(crc, next, -87);
+              FALLTHROUGH_INTENDED;
+            case 86:
+              CRCtriplet(crc, next, -86);
+              FALLTHROUGH_INTENDED;
+            case 85:
+              CRCtriplet(crc, next, -85);
+              FALLTHROUGH_INTENDED;
+            case 84:
+              CRCtriplet(crc, next, -84);
+              FALLTHROUGH_INTENDED;
+            case 83:
+              CRCtriplet(crc, next, -83);
+              FALLTHROUGH_INTENDED;
+            case 82:
+              CRCtriplet(crc, next, -82);
+              FALLTHROUGH_INTENDED;
+            case 81:
+              CRCtriplet(crc, next, -81);
+              FALLTHROUGH_INTENDED;
+            case 80:
+              CRCtriplet(crc, next, -80);
+              FALLTHROUGH_INTENDED;
+            case 79:
+              CRCtriplet(crc, next, -79);
+              FALLTHROUGH_INTENDED;
+            case 78:
+              CRCtriplet(crc, next, -78);
+              FALLTHROUGH_INTENDED;
+            case 77:
+              CRCtriplet(crc, next, -77);
+              FALLTHROUGH_INTENDED;
+            case 76:
+              CRCtriplet(crc, next, -76);
+              FALLTHROUGH_INTENDED;
+            case 75:
+              CRCtriplet(crc, next, -75);
+              FALLTHROUGH_INTENDED;
+            case 74:
+              CRCtriplet(crc, next, -74);
+              FALLTHROUGH_INTENDED;
+            case 73:
+              CRCtriplet(crc, next, -73);
+              FALLTHROUGH_INTENDED;
+            case 72:
+              CRCtriplet(crc, next, -72);
+              FALLTHROUGH_INTENDED;
+            case 71:
+              CRCtriplet(crc, next, -71);
+              FALLTHROUGH_INTENDED;
+            case 70:
+              CRCtriplet(crc, next, -70);
+              FALLTHROUGH_INTENDED;
+            case 69:
+              CRCtriplet(crc, next, -69);
+              FALLTHROUGH_INTENDED;
+            case 68:
+              CRCtriplet(crc, next, -68);
+              FALLTHROUGH_INTENDED;
+            case 67:
+              CRCtriplet(crc, next, -67);
+              FALLTHROUGH_INTENDED;
+            case 66:
+              CRCtriplet(crc, next, -66);
+              FALLTHROUGH_INTENDED;
+            case 65:
+              CRCtriplet(crc, next, -65);
+              FALLTHROUGH_INTENDED;
+            case 64:
+              CRCtriplet(crc, next, -64);
+              FALLTHROUGH_INTENDED;
+            case 63:
+              CRCtriplet(crc, next, -63);
+              FALLTHROUGH_INTENDED;
+            case 62:
+              CRCtriplet(crc, next, -62);
+              FALLTHROUGH_INTENDED;
+            case 61:
+              CRCtriplet(crc, next, -61);
+              FALLTHROUGH_INTENDED;
+            case 60:
+              CRCtriplet(crc, next, -60);
+              FALLTHROUGH_INTENDED;
+            case 59:
+              CRCtriplet(crc, next, -59);
+              FALLTHROUGH_INTENDED;
+            case 58:
+              CRCtriplet(crc, next, -58);
+              FALLTHROUGH_INTENDED;
+            case 57:
+              CRCtriplet(crc, next, -57);
+              FALLTHROUGH_INTENDED;
+            case 56:
+              CRCtriplet(crc, next, -56);
+              FALLTHROUGH_INTENDED;
+            case 55:
+              CRCtriplet(crc, next, -55);
+              FALLTHROUGH_INTENDED;
+            case 54:
+              CRCtriplet(crc, next, -54);
+              FALLTHROUGH_INTENDED;
+            case 53:
+              CRCtriplet(crc, next, -53);
+              FALLTHROUGH_INTENDED;
+            case 52:
+              CRCtriplet(crc, next, -52);
+              FALLTHROUGH_INTENDED;
+            case 51:
+              CRCtriplet(crc, next, -51);
+              FALLTHROUGH_INTENDED;
+            case 50:
+              CRCtriplet(crc, next, -50);
+              FALLTHROUGH_INTENDED;
+            case 49:
+              CRCtriplet(crc, next, -49);
+              FALLTHROUGH_INTENDED;
+            case 48:
+              CRCtriplet(crc, next, -48);
+              FALLTHROUGH_INTENDED;
+            case 47:
+              CRCtriplet(crc, next, -47);
+              FALLTHROUGH_INTENDED;
+            case 46:
+              CRCtriplet(crc, next, -46);
+              FALLTHROUGH_INTENDED;
+            case 45:
+              CRCtriplet(crc, next, -45);
+              FALLTHROUGH_INTENDED;
+            case 44:
+              CRCtriplet(crc, next, -44);
+              FALLTHROUGH_INTENDED;
+            case 43:
+              CRCtriplet(crc, next, -43);
+              FALLTHROUGH_INTENDED;
+            case 42:
+              CRCtriplet(crc, next, -42);
+              FALLTHROUGH_INTENDED;
+            case 41:
+              CRCtriplet(crc, next, -41);
+              FALLTHROUGH_INTENDED;
+            case 40:
+              CRCtriplet(crc, next, -40);
+              FALLTHROUGH_INTENDED;
+            case 39:
+              CRCtriplet(crc, next, -39);
+              FALLTHROUGH_INTENDED;
+            case 38:
+              CRCtriplet(crc, next, -38);
+              FALLTHROUGH_INTENDED;
+            case 37:
+              CRCtriplet(crc, next, -37);
+              FALLTHROUGH_INTENDED;
+            case 36:
+              CRCtriplet(crc, next, -36);
+              FALLTHROUGH_INTENDED;
+            case 35:
+              CRCtriplet(crc, next, -35);
+              FALLTHROUGH_INTENDED;
+            case 34:
+              CRCtriplet(crc, next, -34);
+              FALLTHROUGH_INTENDED;
+            case 33:
+              CRCtriplet(crc, next, -33);
+              FALLTHROUGH_INTENDED;
+            case 32:
+              CRCtriplet(crc, next, -32);
+              FALLTHROUGH_INTENDED;
+            case 31:
+              CRCtriplet(crc, next, -31);
+              FALLTHROUGH_INTENDED;
+            case 30:
+              CRCtriplet(crc, next, -30);
+              FALLTHROUGH_INTENDED;
+            case 29:
+              CRCtriplet(crc, next, -29);
+              FALLTHROUGH_INTENDED;
+            case 28:
+              CRCtriplet(crc, next, -28);
+              FALLTHROUGH_INTENDED;
+            case 27:
+              CRCtriplet(crc, next, -27);
+              FALLTHROUGH_INTENDED;
+            case 26:
+              CRCtriplet(crc, next, -26);
+              FALLTHROUGH_INTENDED;
+            case 25:
+              CRCtriplet(crc, next, -25);
+              FALLTHROUGH_INTENDED;
+            case 24:
+              CRCtriplet(crc, next, -24);
+              FALLTHROUGH_INTENDED;
+            case 23:
+              CRCtriplet(crc, next, -23);
+              FALLTHROUGH_INTENDED;
+            case 22:
+              CRCtriplet(crc, next, -22);
+              FALLTHROUGH_INTENDED;
+            case 21:
+              CRCtriplet(crc, next, -21);
+              FALLTHROUGH_INTENDED;
+            case 20:
+              CRCtriplet(crc, next, -20);
+              FALLTHROUGH_INTENDED;
+            case 19:
+              CRCtriplet(crc, next, -19);
+              FALLTHROUGH_INTENDED;
+            case 18:
+              CRCtriplet(crc, next, -18);
+              FALLTHROUGH_INTENDED;
+            case 17:
+              CRCtriplet(crc, next, -17);
+              FALLTHROUGH_INTENDED;
+            case 16:
+              CRCtriplet(crc, next, -16);
+              FALLTHROUGH_INTENDED;
+            case 15:
+              CRCtriplet(crc, next, -15);
+              FALLTHROUGH_INTENDED;
+            case 14:
+              CRCtriplet(crc, next, -14);
+              FALLTHROUGH_INTENDED;
+            case 13:
+              CRCtriplet(crc, next, -13);
+              FALLTHROUGH_INTENDED;
+            case 12:
+              CRCtriplet(crc, next, -12);
+              FALLTHROUGH_INTENDED;
+            case 11:
+              CRCtriplet(crc, next, -11);
+              FALLTHROUGH_INTENDED;
+            case 10:
+              CRCtriplet(crc, next, -10);
+              FALLTHROUGH_INTENDED;
+            case 9:
+              CRCtriplet(crc, next, -9);
+              FALLTHROUGH_INTENDED;
+            case 8:
+              CRCtriplet(crc, next, -8);
+              FALLTHROUGH_INTENDED;
+            case 7:
+              CRCtriplet(crc, next, -7);
+              FALLTHROUGH_INTENDED;
+            case 6:
+              CRCtriplet(crc, next, -6);
+              FALLTHROUGH_INTENDED;
+            case 5:
+              CRCtriplet(crc, next, -5);
+              FALLTHROUGH_INTENDED;
+            case 4:
+              CRCtriplet(crc, next, -4);
+              FALLTHROUGH_INTENDED;
+            case 3:
+              CRCtriplet(crc, next, -3);
+              FALLTHROUGH_INTENDED;
+            case 2:
+              CRCtriplet(crc, next, -2);
+              FALLTHROUGH_INTENDED;
+            case 1:
+              CRCduplet(crc, next, -1); // the final triplet is actually only 2
+              //{ CombineCRC(); }
+              crc0 = CombineCRC(block_size, crc0, crc1, crc2, next2);
+              if (--n > 0) {
+                crc1 = crc2 = 0;
+                block_size = 128;
+                // points to the first byte of the next block
+                next0 = next2 + 128;
+                next1 = next0 + 128; // from here on all blocks are 128 long
+                next2 = next1 + 128;
+              }
+              FALLTHROUGH_INTENDED;
+            case 0:;
+          } while (n > 0);
+      }
+      next = (const unsigned char*)next2;
+    }
+    uint64_t count2 = len >> 3; // 216 of less bytes is 27 or less singlets
+    len = len & 7;
+    next += (count2 * 8);
+    switch (count2) {
+      case 27:
+        CRCsinglet(crc0, next, -27 * 8);
+        FALLTHROUGH_INTENDED;
+      case 26:
+        CRCsinglet(crc0, next, -26 * 8);
+        FALLTHROUGH_INTENDED;
+      case 25:
+        CRCsinglet(crc0, next, -25 * 8);
+        FALLTHROUGH_INTENDED;
+      case 24:
+        CRCsinglet(crc0, next, -24 * 8);
+        FALLTHROUGH_INTENDED;
+      case 23:
+        CRCsinglet(crc0, next, -23 * 8);
+        FALLTHROUGH_INTENDED;
+      case 22:
+        CRCsinglet(crc0, next, -22 * 8);
+        FALLTHROUGH_INTENDED;
+      case 21:
+        CRCsinglet(crc0, next, -21 * 8);
+        FALLTHROUGH_INTENDED;
+      case 20:
+        CRCsinglet(crc0, next, -20 * 8);
+        FALLTHROUGH_INTENDED;
+      case 19:
+        CRCsinglet(crc0, next, -19 * 8);
+        FALLTHROUGH_INTENDED;
+      case 18:
+        CRCsinglet(crc0, next, -18 * 8);
+        FALLTHROUGH_INTENDED;
+      case 17:
+        CRCsinglet(crc0, next, -17 * 8);
+        FALLTHROUGH_INTENDED;
+      case 16:
+        CRCsinglet(crc0, next, -16 * 8);
+        FALLTHROUGH_INTENDED;
+      case 15:
+        CRCsinglet(crc0, next, -15 * 8);
+        FALLTHROUGH_INTENDED;
+      case 14:
+        CRCsinglet(crc0, next, -14 * 8);
+        FALLTHROUGH_INTENDED;
+      case 13:
+        CRCsinglet(crc0, next, -13 * 8);
+        FALLTHROUGH_INTENDED;
+      case 12:
+        CRCsinglet(crc0, next, -12 * 8);
+        FALLTHROUGH_INTENDED;
+      case 11:
+        CRCsinglet(crc0, next, -11 * 8);
+        FALLTHROUGH_INTENDED;
+      case 10:
+        CRCsinglet(crc0, next, -10 * 8);
+        FALLTHROUGH_INTENDED;
+      case 9:
+        CRCsinglet(crc0, next, -9 * 8);
+        FALLTHROUGH_INTENDED;
+      case 8:
+        CRCsinglet(crc0, next, -8 * 8);
+        FALLTHROUGH_INTENDED;
+      case 7:
+        CRCsinglet(crc0, next, -7 * 8);
+        FALLTHROUGH_INTENDED;
+      case 6:
+        CRCsinglet(crc0, next, -6 * 8);
+        FALLTHROUGH_INTENDED;
+      case 5:
+        CRCsinglet(crc0, next, -5 * 8);
+        FALLTHROUGH_INTENDED;
+      case 4:
+        CRCsinglet(crc0, next, -4 * 8);
+        FALLTHROUGH_INTENDED;
+      case 3:
+        CRCsinglet(crc0, next, -3 * 8);
+        FALLTHROUGH_INTENDED;
+      case 2:
+        CRCsinglet(crc0, next, -2 * 8);
+        FALLTHROUGH_INTENDED;
+      case 1:
+        CRCsinglet(crc0, next, -1 * 8);
+        FALLTHROUGH_INTENDED;
+      case 0:;
+    }
+  }
+  {
+    align_to_8(len, crc0, next);
+    return (uint32_t)crc0 ^ 0xffffffffu;
+  }
+}
+
+#endif //HAVE_SSE42 && HAVE_PCLMUL
+
+static inline Function Choose_Extend() {
+#ifdef HAVE_POWER8
+  return isAltiVec() ? ExtendPPCImpl : ExtendImpl<Slow_CRC32>;
+#elif defined(__linux__) && defined(HAVE_ARM64_CRC)
+  if(crc32c_runtime_check()) {
+    pmull_runtime_flag = crc32c_pmull_runtime_check();
+    return ExtendARMImpl;
+  } else {
+    return ExtendImpl<Slow_CRC32>;
+  }
+#else
+  if (isSSE42()) {
+    if (isPCLMULQDQ()) {
+#if defined HAVE_SSE42  && defined HAVE_PCLMUL && !defined NO_THREEWAY_CRC32C
+      return crc32c_3way;
+#else
+    return ExtendImpl<Fast_CRC32>; // Fast_CRC32 will check HAVE_SSE42 itself
+#endif
+    }
+    else {  // no runtime PCLMULQDQ support but has SSE42 support
+      return ExtendImpl<Fast_CRC32>;
+    }
+  } // end of isSSE42()
+  else {
+    return ExtendImpl<Slow_CRC32>;
+  }
+#endif
+}
+
+static Function ChosenExtend = Choose_Extend();
+uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
+  return ChosenExtend(crc, buf, size);
+}
+
+
+}  // namespace crc32c
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/crc32c.h b/src/rocksdb/util/crc32c.h
new file mode 100644
index 000000000..a3c7cd1d7
--- /dev/null
+++ b/src/rocksdb/util/crc32c.h
@@ -0,0 +1,51 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+#include <stddef.h>
+#include <stdint.h>
+#include <string>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace crc32c {
+
+extern std::string IsFastCrc32Supported();
+
+// Return the crc32c of concat(A, data[0,n-1]) where init_crc is the
+// crc32c of some string A.  Extend() is often used to maintain the
+// crc32c of a stream of data.
+extern uint32_t Extend(uint32_t init_crc, const char* data, size_t n);
+
+// Return the crc32c of data[0,n-1]
+inline uint32_t Value(const char* data, size_t n) {
+  return Extend(0, data, n);
+}
+
+static const uint32_t kMaskDelta = 0xa282ead8ul;
+
+// Return a masked representation of crc.
+//
+// Motivation: it is problematic to compute the CRC of a string that
+// contains embedded CRCs.  Therefore we recommend that CRCs stored
+// somewhere (e.g., in files) should be masked before being stored.
+inline uint32_t Mask(uint32_t crc) {
+  // Rotate right by 15 bits and add a constant.
+  return ((crc >> 15) | (crc << 17)) + kMaskDelta;
+}
+
+// Return the crc whose masked representation is masked_crc.
+inline uint32_t Unmask(uint32_t masked_crc) {
+  uint32_t rot = masked_crc - kMaskDelta;
+  return ((rot >> 17) | (rot << 15));
+}
+
+}  // namespace crc32c
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/crc32c_arm64.cc b/src/rocksdb/util/crc32c_arm64.cc
new file mode 100644
index 000000000..566810f4b
--- /dev/null
+++ b/src/rocksdb/util/crc32c_arm64.cc
@@ -0,0 +1,165 @@
+//  Copyright (c) 2018, Arm Limited and affiliates. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "util/crc32c_arm64.h"
+
+#if defined(__linux__) && defined(HAVE_ARM64_CRC)
+
+#include <asm/hwcap.h>
+#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
+#include <sys/auxv.h>
+#endif
+#ifndef HWCAP_CRC32
+#define HWCAP_CRC32 (1 << 7)
+#endif
+#ifndef HWCAP_PMULL
+#define HWCAP_PMULL (1 << 4)
+#endif
+
+#ifdef HAVE_ARM64_CRYPTO
+/* unfolding to compute 8 * 3 = 24 bytes parallelly */
+#define CRC32C24BYTES(ITR)                                    \
+  crc1 = crc32c_u64(crc1, *(buf64 + BLK_LENGTH + (ITR)));     \
+  crc2 = crc32c_u64(crc2, *(buf64 + BLK_LENGTH * 2 + (ITR))); \
+  crc0 = crc32c_u64(crc0, *(buf64 + (ITR)));
+
+/* unfolding to compute 24 * 7 = 168 bytes parallelly */
+#define CRC32C7X24BYTES(ITR)   \
+  do {                         \
+    CRC32C24BYTES((ITR)*7 + 0) \
+    CRC32C24BYTES((ITR)*7 + 1) \
+    CRC32C24BYTES((ITR)*7 + 2) \
+    CRC32C24BYTES((ITR)*7 + 3) \
+    CRC32C24BYTES((ITR)*7 + 4) \
+    CRC32C24BYTES((ITR)*7 + 5) \
+    CRC32C24BYTES((ITR)*7 + 6) \
+  } while (0)
+#endif
+
+extern bool pmull_runtime_flag;
+
+uint32_t crc32c_runtime_check(void) {
+#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
+  uint64_t auxv = getauxval(AT_HWCAP);
+  return (auxv & HWCAP_CRC32) != 0;
+#else
+  return 0;
+#endif
+}
+
+bool crc32c_pmull_runtime_check(void) {
+#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
+  uint64_t auxv = getauxval(AT_HWCAP);
+  return (auxv & HWCAP_PMULL) != 0;
+#else
+  return false;
+#endif
+}
+
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+uint32_t crc32c_arm64(uint32_t crc, unsigned char const *data,
+                             unsigned len) {
+  const uint8_t *buf8;
+  const uint64_t *buf64 = (uint64_t *)data;
+  int length = (int)len;
+  crc ^= 0xffffffff;
+
+  /*
+   * Pmull runtime check here.
+   * Raspberry Pi supports crc32 but doesn't support pmull.
+   * Skip Crc32c Parallel computation if no crypto extension available.
+   */
+  if (pmull_runtime_flag) {
+/* Macro (HAVE_ARM64_CRYPTO) is used for compiling check  */
+#ifdef HAVE_ARM64_CRYPTO
+/* Crc32c Parallel computation
+ *   Algorithm comes from Intel whitepaper:
+ *   crc-iscsi-polynomial-crc32-instruction-paper
+ *
+ * Input data is divided into three equal-sized blocks
+ *   Three parallel blocks (crc0, crc1, crc2) for 1024 Bytes
+ *   One Block: 42(BLK_LENGTH) * 8(step length: crc32c_u64) bytes
+ */
+#define BLK_LENGTH 42
+    while (length >= 1024) {
+      uint64_t t0, t1;
+      uint32_t crc0 = 0, crc1 = 0, crc2 = 0;
+
+      /* Parallel Param:
+       *   k0 = CRC32(x ^ (42 * 8 * 8 * 2 - 1));
+       *   k1 = CRC32(x ^ (42 * 8 * 8 - 1));
+       */
+      uint32_t k0 = 0xe417f38a, k1 = 0x8f158014;
+
+      /* Prefetch data for following block to avoid cache miss */
+      PREF1KL1((uint8_t *)buf64, 1024);
+
+      /* First 8 byte for better pipelining */
+      crc0 = crc32c_u64(crc, *buf64++);
+
+      /* 3 blocks crc32c parallel computation
+       * Macro unfolding to compute parallelly
+       * 168 * 6 = 1008 (bytes)
+       */
+      CRC32C7X24BYTES(0);
+      CRC32C7X24BYTES(1);
+      CRC32C7X24BYTES(2);
+      CRC32C7X24BYTES(3);
+      CRC32C7X24BYTES(4);
+      CRC32C7X24BYTES(5);
+      buf64 += (BLK_LENGTH * 3);
+
+      /* Last 8 bytes */
+      crc = crc32c_u64(crc2, *buf64++);
+
+      t0 = (uint64_t)vmull_p64(crc0, k0);
+      t1 = (uint64_t)vmull_p64(crc1, k1);
+
+      /* Merge (crc0, crc1, crc2) -> crc */
+      crc1 = crc32c_u64(0, t1);
+      crc ^= crc1;
+      crc0 = crc32c_u64(0, t0);
+      crc ^= crc0;
+
+      length -= 1024;
+    }
+
+    if (length == 0) return crc ^ (0xffffffffU);
+#endif
+  }  // if Pmull runtime check here
+
+  buf8 = (const uint8_t *)buf64;
+  while (length >= 8) {
+    crc = crc32c_u64(crc, *(const uint64_t *)buf8);
+    buf8 += 8;
+    length -= 8;
+  }
+
+  /* The following is more efficient than the straight loop */
+  if (length >= 4) {
+    crc = crc32c_u32(crc, *(const uint32_t *)buf8);
+    buf8 += 4;
+    length -= 4;
+  }
+
+  if (length >= 2) {
+    crc = crc32c_u16(crc, *(const uint16_t *)buf8);
+    buf8 += 2;
+    length -= 2;
+  }
+
+  if (length >= 1) crc = crc32c_u8(crc, *buf8);
+
+  crc ^= 0xffffffff;
+  return crc;
+}
+
+#endif
diff --git a/src/rocksdb/util/crc32c_arm64.h b/src/rocksdb/util/crc32c_arm64.h
new file mode 100644
index 000000000..a12354683
--- /dev/null
+++ b/src/rocksdb/util/crc32c_arm64.h
@@ -0,0 +1,48 @@
+//  Copyright (c) 2018, Arm Limited and affiliates. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#ifndef UTIL_CRC32C_ARM64_H
+#define UTIL_CRC32C_ARM64_H
+
+#include <cinttypes>
+
+#if defined(__aarch64__) || defined(__AARCH64__)
+
+#ifdef __ARM_FEATURE_CRC32
+#define HAVE_ARM64_CRC
+#include <arm_acle.h>
+#define crc32c_u8(crc, v) __crc32cb(crc, v)
+#define crc32c_u16(crc, v) __crc32ch(crc, v)
+#define crc32c_u32(crc, v) __crc32cw(crc, v)
+#define crc32c_u64(crc, v) __crc32cd(crc, v)
+#define PREF4X64L1(buffer, PREF_OFFSET, ITR)                \
+  __asm__("PRFM PLDL1KEEP, [%x[v],%[c]]" ::[v] "r"(buffer), \
+          [c] "I"((PREF_OFFSET) + ((ITR) + 0) * 64));       \
+  __asm__("PRFM PLDL1KEEP, [%x[v],%[c]]" ::[v] "r"(buffer), \
+          [c] "I"((PREF_OFFSET) + ((ITR) + 1) * 64));       \
+  __asm__("PRFM PLDL1KEEP, [%x[v],%[c]]" ::[v] "r"(buffer), \
+          [c] "I"((PREF_OFFSET) + ((ITR) + 2) * 64));       \
+  __asm__("PRFM PLDL1KEEP, [%x[v],%[c]]" ::[v] "r"(buffer), \
+          [c] "I"((PREF_OFFSET) + ((ITR) + 3) * 64));
+
+#define PREF1KL1(buffer, PREF_OFFSET)  \
+  PREF4X64L1(buffer, (PREF_OFFSET), 0) \
+  PREF4X64L1(buffer, (PREF_OFFSET), 4) \
+  PREF4X64L1(buffer, (PREF_OFFSET), 8) \
+  PREF4X64L1(buffer, (PREF_OFFSET), 12)
+
+extern uint32_t crc32c_arm64(uint32_t crc, unsigned char const *data, unsigned len);
+extern uint32_t crc32c_runtime_check(void);
+extern bool crc32c_pmull_runtime_check(void);
+
+#ifdef __ARM_FEATURE_CRYPTO
+#define HAVE_ARM64_CRYPTO
+#include <arm_neon.h>
+#endif  // __ARM_FEATURE_CRYPTO
+#endif  // __ARM_FEATURE_CRC32
+
+#endif  // defined(__aarch64__) || defined(__AARCH64__)
+
+#endif
diff --git a/src/rocksdb/util/crc32c_ppc.c b/src/rocksdb/util/crc32c_ppc.c
new file mode 100644
index 000000000..888a4943e
--- /dev/null
+++ b/src/rocksdb/util/crc32c_ppc.c
@@ -0,0 +1,94 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  Copyright (c) 2017 International Business Machines Corp.
+//  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#define CRC_TABLE
+#include <stdint.h>
+#include <stdlib.h>
+#include <strings.h>
+#include "util/crc32c_ppc_constants.h"
+
+#define VMX_ALIGN 16
+#define VMX_ALIGN_MASK (VMX_ALIGN - 1)
+
+#ifdef REFLECT
+static unsigned int crc32_align(unsigned int crc, unsigned char const *p,
+                                unsigned long len) {
+  while (len--) crc = crc_table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
+  return crc;
+}
+#endif
+
+#ifdef HAVE_POWER8
+unsigned int __crc32_vpmsum(unsigned int crc, unsigned char const *p,
+                            unsigned long len);
+
+static uint32_t crc32_vpmsum(uint32_t crc, unsigned char const *data,
+                             unsigned len) {
+  unsigned int prealign;
+  unsigned int tail;
+
+#ifdef CRC_XOR
+  crc ^= 0xffffffff;
+#endif
+
+  if (len < VMX_ALIGN + VMX_ALIGN_MASK) {
+    crc = crc32_align(crc, data, (unsigned long)len);
+    goto out;
+  }
+
+  if ((unsigned long)data & VMX_ALIGN_MASK) {
+    prealign = VMX_ALIGN - ((unsigned long)data & VMX_ALIGN_MASK);
+    crc = crc32_align(crc, data, prealign);
+    len -= prealign;
+    data += prealign;
+  }
+
+  crc = __crc32_vpmsum(crc, data, (unsigned long)len & ~VMX_ALIGN_MASK);
+
+  tail = len & VMX_ALIGN_MASK;
+  if (tail) {
+    data += len & ~VMX_ALIGN_MASK;
+    crc = crc32_align(crc, data, tail);
+  }
+
+out:
+#ifdef CRC_XOR
+  crc ^= 0xffffffff;
+#endif
+
+  return crc;
+}
+
+/* This wrapper function works around the fact that crc32_vpmsum
+ * does not gracefully handle the case where the data pointer is NULL.  There
+ * may be room for performance improvement here.
+ */
+uint32_t crc32c_ppc(uint32_t crc, unsigned char const *data, unsigned len) {
+  unsigned char *buf2;
+
+  if (!data) {
+    buf2 = (unsigned char *)malloc(len);
+    bzero(buf2, len);
+    crc = crc32_vpmsum(crc, buf2, len);
+    free(buf2);
+  } else {
+    crc = crc32_vpmsum(crc, data, (unsigned long)len);
+  }
+  return crc;
+}
+
+#else /* HAVE_POWER8 */
+
+/* This symbol has to exist on non-ppc architectures (and on legacy
+ * ppc systems using power7 or below) in order to compile properly
+ * there, even though it won't be called.
+ */
+uint32_t crc32c_ppc(uint32_t crc, unsigned char const *data, unsigned len) {
+  return 0;
+}
+
+#endif /* HAVE_POWER8 */
diff --git a/src/rocksdb/util/crc32c_ppc.h b/src/rocksdb/util/crc32c_ppc.h
new file mode 100644
index 000000000..c359061c6
--- /dev/null
+++ b/src/rocksdb/util/crc32c_ppc.h
@@ -0,0 +1,19 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  Copyright (c) 2017 International Business Machines Corp.
+//  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uint32_t crc32c_ppc(uint32_t crc, unsigned char const *buffer,
+                           unsigned len);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/src/rocksdb/util/crc32c_ppc_asm.S b/src/rocksdb/util/crc32c_ppc_asm.S
new file mode 100644
index 000000000..a317bf96b
--- /dev/null
+++ b/src/rocksdb/util/crc32c_ppc_asm.S
@@ -0,0 +1,752 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  Copyright (c) 2015 Anton Blanchard <anton@au.ibm.com>, IBM
+//  Copyright (c) 2017 International Business Machines Corp.
+//  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <ppc-asm.h>
+#include "ppc-opcode.h"
+
+#undef toc
+
+#ifndef r1
+#define r1 1
+#endif
+
+#ifndef r2
+#define r2 2
+#endif
+
+	.section	.rodata
+.balign 16
+
+.byteswap_constant:
+	/* byte reverse permute constant */
+	.octa 0x0F0E0D0C0B0A09080706050403020100
+
+#define __ASSEMBLY__
+#include "crc32c_ppc_constants.h"
+
+	.text
+
+#if defined(__BIG_ENDIAN__) && defined(REFLECT)
+#define BYTESWAP_DATA
+#elif defined(__LITTLE_ENDIAN__) && !defined(REFLECT)
+#define BYTESWAP_DATA
+#else
+#undef BYTESWAP_DATA
+#endif
+
+#define off16		r25
+#define off32		r26
+#define off48		r27
+#define off64		r28
+#define off80		r29
+#define off96		r30
+#define off112		r31
+
+#define const1		v24
+#define const2		v25
+
+#define byteswap	v26
+#define	mask_32bit	v27
+#define	mask_64bit	v28
+#define zeroes		v29
+
+#ifdef BYTESWAP_DATA
+#define VPERM(A, B, C, D) vperm	A, B, C, D
+#else
+#define VPERM(A, B, C, D)
+#endif
+
+/* unsigned int __crc32_vpmsum(unsigned int crc, void *p, unsigned long len) */
+FUNC_START(__crc32_vpmsum)
+	std	r31,-8(r1)
+	std	r30,-16(r1)
+	std	r29,-24(r1)
+	std	r28,-32(r1)
+	std	r27,-40(r1)
+	std	r26,-48(r1)
+	std	r25,-56(r1)
+
+	li	off16,16
+	li	off32,32
+	li	off48,48
+	li	off64,64
+	li	off80,80
+	li	off96,96
+	li	off112,112
+	li	r0,0
+
+	/* Enough room for saving 10 non volatile VMX registers */
+	subi	r6,r1,56+10*16
+	subi	r7,r1,56+2*16
+
+	stvx	v20,0,r6
+	stvx	v21,off16,r6
+	stvx	v22,off32,r6
+	stvx	v23,off48,r6
+	stvx	v24,off64,r6
+	stvx	v25,off80,r6
+	stvx	v26,off96,r6
+	stvx	v27,off112,r6
+	stvx	v28,0,r7
+	stvx	v29,off16,r7
+
+	mr	r10,r3
+
+	vxor	zeroes,zeroes,zeroes
+	vspltisw v0,-1
+
+	vsldoi	mask_32bit,zeroes,v0,4
+	vsldoi	mask_64bit,zeroes,v0,8
+
+	/* Get the initial value into v8 */
+	vxor	v8,v8,v8
+	MTVRD(v8, r3)
+#ifdef REFLECT
+	vsldoi	v8,zeroes,v8,8	/* shift into bottom 32 bits */
+#else
+	vsldoi	v8,v8,zeroes,4	/* shift into top 32 bits */
+#endif
+
+#ifdef BYTESWAP_DATA
+	addis	r3,r2,.byteswap_constant@toc@ha
+	addi	r3,r3,.byteswap_constant@toc@l
+
+	lvx	byteswap,0,r3
+	addi	r3,r3,16
+#endif
+
+	cmpdi	r5,256
+	blt	.Lshort
+
+	rldicr	r6,r5,0,56
+
+	/* Checksum in blocks of MAX_SIZE */
+1:	lis	r7,MAX_SIZE@h
+	ori	r7,r7,MAX_SIZE@l
+	mr	r9,r7
+	cmpd	r6,r7
+	bgt	2f
+	mr	r7,r6
+2:	subf	r6,r7,r6
+
+	/* our main loop does 128 bytes at a time */
+	srdi	r7,r7,7
+
+	/*
+	 * Work out the offset into the constants table to start at. Each
+	 * constant is 16 bytes, and it is used against 128 bytes of input
+	 * data - 128 / 16 = 8
+	 */
+	sldi	r8,r7,4
+	srdi	r9,r9,3
+	subf	r8,r8,r9
+
+	/* We reduce our final 128 bytes in a separate step */
+	addi	r7,r7,-1
+	mtctr	r7
+
+	addis	r3,r2,.constants@toc@ha
+	addi	r3,r3,.constants@toc@l
+
+	/* Find the start of our constants */
+	add	r3,r3,r8
+
+	/* zero v0-v7 which will contain our checksums */
+	vxor	v0,v0,v0
+	vxor	v1,v1,v1
+	vxor	v2,v2,v2
+	vxor	v3,v3,v3
+	vxor	v4,v4,v4
+	vxor	v5,v5,v5
+	vxor	v6,v6,v6
+	vxor	v7,v7,v7
+
+	lvx	const1,0,r3
+
+	/*
+	 * If we are looping back to consume more data we use the values
+	 * already in v16-v23.
+	 */
+	cmpdi	r0,1
+	beq	2f
+
+	/* First warm up pass */
+	lvx	v16,0,r4
+	lvx	v17,off16,r4
+	VPERM(v16,v16,v16,byteswap)
+	VPERM(v17,v17,v17,byteswap)
+	lvx	v18,off32,r4
+	lvx	v19,off48,r4
+	VPERM(v18,v18,v18,byteswap)
+	VPERM(v19,v19,v19,byteswap)
+	lvx	v20,off64,r4
+	lvx	v21,off80,r4
+	VPERM(v20,v20,v20,byteswap)
+	VPERM(v21,v21,v21,byteswap)
+	lvx	v22,off96,r4
+	lvx	v23,off112,r4
+	VPERM(v22,v22,v22,byteswap)
+	VPERM(v23,v23,v23,byteswap)
+	addi	r4,r4,8*16
+
+	/* xor in initial value */
+	vxor	v16,v16,v8
+
+2:	bdz	.Lfirst_warm_up_done
+
+	addi	r3,r3,16
+	lvx	const2,0,r3
+
+	/* Second warm up pass */
+	VPMSUMD(v8,v16,const1)
+	lvx	v16,0,r4
+	VPERM(v16,v16,v16,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v9,v17,const1)
+	lvx	v17,off16,r4
+	VPERM(v17,v17,v17,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v10,v18,const1)
+	lvx	v18,off32,r4
+	VPERM(v18,v18,v18,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v11,v19,const1)
+	lvx	v19,off48,r4
+	VPERM(v19,v19,v19,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v12,v20,const1)
+	lvx	v20,off64,r4
+	VPERM(v20,v20,v20,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v13,v21,const1)
+	lvx	v21,off80,r4
+	VPERM(v21,v21,v21,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v14,v22,const1)
+	lvx	v22,off96,r4
+	VPERM(v22,v22,v22,byteswap)
+	ori	r2,r2,0
+
+	VPMSUMD(v15,v23,const1)
+	lvx	v23,off112,r4
+	VPERM(v23,v23,v23,byteswap)
+
+	addi	r4,r4,8*16
+
+	bdz	.Lfirst_cool_down
+
+	/*
+	 * main loop. We modulo schedule it such that it takes three iterations
+	 * to complete - first iteration load, second iteration vpmsum, third
+	 * iteration xor.
+	 */
+	.balign	16
+4:	lvx	const1,0,r3
+	addi	r3,r3,16
+	ori	r2,r2,0
+
+	vxor	v0,v0,v8
+	VPMSUMD(v8,v16,const2)
+	lvx	v16,0,r4
+	VPERM(v16,v16,v16,byteswap)
+	ori	r2,r2,0
+
+	vxor	v1,v1,v9
+	VPMSUMD(v9,v17,const2)
+	lvx	v17,off16,r4
+	VPERM(v17,v17,v17,byteswap)
+	ori	r2,r2,0
+
+	vxor	v2,v2,v10
+	VPMSUMD(v10,v18,const2)
+	lvx	v18,off32,r4
+	VPERM(v18,v18,v18,byteswap)
+	ori	r2,r2,0
+
+	vxor	v3,v3,v11
+	VPMSUMD(v11,v19,const2)
+	lvx	v19,off48,r4
+	VPERM(v19,v19,v19,byteswap)
+	lvx	const2,0,r3
+	ori	r2,r2,0
+
+	vxor	v4,v4,v12
+	VPMSUMD(v12,v20,const1)
+	lvx	v20,off64,r4
+	VPERM(v20,v20,v20,byteswap)
+	ori	r2,r2,0
+
+	vxor	v5,v5,v13
+	VPMSUMD(v13,v21,const1)
+	lvx	v21,off80,r4
+	VPERM(v21,v21,v21,byteswap)
+	ori	r2,r2,0
+
+	vxor	v6,v6,v14
+	VPMSUMD(v14,v22,const1)
+	lvx	v22,off96,r4
+	VPERM(v22,v22,v22,byteswap)
+	ori	r2,r2,0
+
+	vxor	v7,v7,v15
+	VPMSUMD(v15,v23,const1)
+	lvx	v23,off112,r4
+	VPERM(v23,v23,v23,byteswap)
+
+	addi	r4,r4,8*16
+
+	bdnz	4b
+
+.Lfirst_cool_down:
+	/* First cool down pass */
+	lvx	const1,0,r3
+	addi	r3,r3,16
+
+	vxor	v0,v0,v8
+	VPMSUMD(v8,v16,const1)
+	ori	r2,r2,0
+
+	vxor	v1,v1,v9
+	VPMSUMD(v9,v17,const1)
+	ori	r2,r2,0
+
+	vxor	v2,v2,v10
+	VPMSUMD(v10,v18,const1)
+	ori	r2,r2,0
+
+	vxor	v3,v3,v11
+	VPMSUMD(v11,v19,const1)
+	ori	r2,r2,0
+
+	vxor	v4,v4,v12
+	VPMSUMD(v12,v20,const1)
+	ori	r2,r2,0
+
+	vxor	v5,v5,v13
+	VPMSUMD(v13,v21,const1)
+	ori	r2,r2,0
+
+	vxor	v6,v6,v14
+	VPMSUMD(v14,v22,const1)
+	ori	r2,r2,0
+
+	vxor	v7,v7,v15
+	VPMSUMD(v15,v23,const1)
+	ori	r2,r2,0
+
+.Lsecond_cool_down:
+	/* Second cool down pass */
+	vxor	v0,v0,v8
+	vxor	v1,v1,v9
+	vxor	v2,v2,v10
+	vxor	v3,v3,v11
+	vxor	v4,v4,v12
+	vxor	v5,v5,v13
+	vxor	v6,v6,v14
+	vxor	v7,v7,v15
+
+#ifdef REFLECT
+	/*
+	 * vpmsumd produces a 96 bit result in the least significant bits
+	 * of the register. Since we are bit reflected we have to shift it
+	 * left 32 bits so it occupies the least significant bits in the
+	 * bit reflected domain.
+	 */
+	vsldoi	v0,v0,zeroes,4
+	vsldoi	v1,v1,zeroes,4
+	vsldoi	v2,v2,zeroes,4
+	vsldoi	v3,v3,zeroes,4
+	vsldoi	v4,v4,zeroes,4
+	vsldoi	v5,v5,zeroes,4
+	vsldoi	v6,v6,zeroes,4
+	vsldoi	v7,v7,zeroes,4
+#endif
+
+	/* xor with last 1024 bits */
+	lvx	v8,0,r4
+	lvx	v9,off16,r4
+	VPERM(v8,v8,v8,byteswap)
+	VPERM(v9,v9,v9,byteswap)
+	lvx	v10,off32,r4
+	lvx	v11,off48,r4
+	VPERM(v10,v10,v10,byteswap)
+	VPERM(v11,v11,v11,byteswap)
+	lvx	v12,off64,r4
+	lvx	v13,off80,r4
+	VPERM(v12,v12,v12,byteswap)
+	VPERM(v13,v13,v13,byteswap)
+	lvx	v14,off96,r4
+	lvx	v15,off112,r4
+	VPERM(v14,v14,v14,byteswap)
+	VPERM(v15,v15,v15,byteswap)
+
+	addi	r4,r4,8*16
+
+	vxor	v16,v0,v8
+	vxor	v17,v1,v9
+	vxor	v18,v2,v10
+	vxor	v19,v3,v11
+	vxor	v20,v4,v12
+	vxor	v21,v5,v13
+	vxor	v22,v6,v14
+	vxor	v23,v7,v15
+
+	li	r0,1
+	cmpdi	r6,0
+	addi	r6,r6,128
+	bne	1b
+
+	/* Work out how many bytes we have left */
+	andi.	r5,r5,127
+
+	/* Calculate where in the constant table we need to start */
+	subfic	r6,r5,128
+	add	r3,r3,r6
+
+	/* How many 16 byte chunks are in the tail */
+	srdi	r7,r5,4
+	mtctr	r7
+
+	/*
+	 * Reduce the previously calculated 1024 bits to 64 bits, shifting
+	 * 32 bits to include the trailing 32 bits of zeros
+	 */
+	lvx	v0,0,r3
+	lvx	v1,off16,r3
+	lvx	v2,off32,r3
+	lvx	v3,off48,r3
+	lvx	v4,off64,r3
+	lvx	v5,off80,r3
+	lvx	v6,off96,r3
+	lvx	v7,off112,r3
+	addi	r3,r3,8*16
+
+	VPMSUMW(v0,v16,v0)
+	VPMSUMW(v1,v17,v1)
+	VPMSUMW(v2,v18,v2)
+	VPMSUMW(v3,v19,v3)
+	VPMSUMW(v4,v20,v4)
+	VPMSUMW(v5,v21,v5)
+	VPMSUMW(v6,v22,v6)
+	VPMSUMW(v7,v23,v7)
+
+	/* Now reduce the tail (0 - 112 bytes) */
+	cmpdi	r7,0
+	beq	1f
+
+	lvx	v16,0,r4
+	lvx	v17,0,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off16,r4
+	lvx	v17,off16,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off32,r4
+	lvx	v17,off32,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off48,r4
+	lvx	v17,off48,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off64,r4
+	lvx	v17,off64,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off80,r4
+	lvx	v17,off80,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+	bdz	1f
+
+	lvx	v16,off96,r4
+	lvx	v17,off96,r3
+	VPERM(v16,v16,v16,byteswap)
+	VPMSUMW(v16,v16,v17)
+	vxor	v0,v0,v16
+
+	/* Now xor all the parallel chunks together */
+1:	vxor	v0,v0,v1
+	vxor	v2,v2,v3
+	vxor	v4,v4,v5
+	vxor	v6,v6,v7
+
+	vxor	v0,v0,v2
+	vxor	v4,v4,v6
+
+	vxor	v0,v0,v4
+
+.Lbarrett_reduction:
+	/* Barrett constants */
+	addis	r3,r2,.barrett_constants@toc@ha
+	addi	r3,r3,.barrett_constants@toc@l
+
+	lvx	const1,0,r3
+	lvx	const2,off16,r3
+
+	vsldoi	v1,v0,v0,8
+	vxor	v0,v0,v1		/* xor two 64 bit results together */
+
+#ifdef REFLECT
+	/* shift left one bit */
+	vspltisb v1,1
+	vsl	v0,v0,v1
+#endif
+
+	vand	v0,v0,mask_64bit
+
+#ifndef REFLECT
+	/*
+	 * Now for the Barrett reduction algorithm. The idea is to calculate q,
+	 * the multiple of our polynomial that we need to subtract. By
+	 * doing the computation 2x bits higher (ie 64 bits) and shifting the
+	 * result back down 2x bits, we round down to the nearest multiple.
+	 */
+	VPMSUMD(v1,v0,const1)	/* ma */
+	vsldoi	v1,zeroes,v1,8	/* q = floor(ma/(2^64)) */
+	VPMSUMD(v1,v1,const2)	/* qn */
+	vxor	v0,v0,v1	/* a - qn, subtraction is xor in GF(2) */
+
+	/*
+	 * Get the result into r3. We need to shift it left 8 bytes:
+	 * V0 [ 0 1 2 X ]
+	 * V0 [ 0 X 2 3 ]
+	 */
+	vsldoi	v0,v0,zeroes,8	/* shift result into top 64 bits */
+#else
+	/*
+	 * The reflected version of Barrett reduction. Instead of bit
+	 * reflecting our data (which is expensive to do), we bit reflect our
+	 * constants and our algorithm, which means the intermediate data in
+	 * our vector registers goes from 0-63 instead of 63-0. We can reflect
+	 * the algorithm because we don't carry in mod 2 arithmetic.
+	 */
+	vand	v1,v0,mask_32bit	/* bottom 32 bits of a */
+	VPMSUMD(v1,v1,const1)		/* ma */
+	vand	v1,v1,mask_32bit	/* bottom 32bits of ma */
+	VPMSUMD(v1,v1,const2)		/* qn */
+	vxor	v0,v0,v1		/* a - qn, subtraction is xor in GF(2) */
+
+	/*
+	 * Since we are bit reflected, the result (ie the low 32 bits) is in
+	 * the high 32 bits. We just need to shift it left 4 bytes
+	 * V0 [ 0 1 X 3 ]
+	 * V0 [ 0 X 2 3 ]
+	 */
+	vsldoi	v0,v0,zeroes,4		/* shift result into top 64 bits of */
+#endif
+
+	/* Get it into r3 */
+	MFVRD(r3, v0)
+
+.Lout:
+	subi	r6,r1,56+10*16
+	subi	r7,r1,56+2*16
+
+	lvx	v20,0,r6
+	lvx	v21,off16,r6
+	lvx	v22,off32,r6
+	lvx	v23,off48,r6
+	lvx	v24,off64,r6
+	lvx	v25,off80,r6
+	lvx	v26,off96,r6
+	lvx	v27,off112,r6
+	lvx	v28,0,r7
+	lvx	v29,off16,r7
+
+	ld	r31,-8(r1)
+	ld	r30,-16(r1)
+	ld	r29,-24(r1)
+	ld	r28,-32(r1)
+	ld	r27,-40(r1)
+	ld	r26,-48(r1)
+	ld	r25,-56(r1)
+
+	blr
+
+.Lfirst_warm_up_done:
+	lvx	const1,0,r3
+	addi	r3,r3,16
+
+	VPMSUMD(v8,v16,const1)
+	VPMSUMD(v9,v17,const1)
+	VPMSUMD(v10,v18,const1)
+	VPMSUMD(v11,v19,const1)
+	VPMSUMD(v12,v20,const1)
+	VPMSUMD(v13,v21,const1)
+	VPMSUMD(v14,v22,const1)
+	VPMSUMD(v15,v23,const1)
+
+	b	.Lsecond_cool_down
+
+.Lshort:
+	cmpdi	r5,0
+	beq	.Lzero
+
+	addis	r3,r2,.short_constants@toc@ha
+	addi	r3,r3,.short_constants@toc@l
+
+	/* Calculate where in the constant table we need to start */
+	subfic	r6,r5,256
+	add	r3,r3,r6
+
+	/* How many 16 byte chunks? */
+	srdi	r7,r5,4
+	mtctr	r7
+
+	vxor	v19,v19,v19
+	vxor	v20,v20,v20
+
+	lvx	v0,0,r4
+	lvx	v16,0,r3
+	VPERM(v0,v0,v16,byteswap)
+	vxor	v0,v0,v8	/* xor in initial value */
+	VPMSUMW(v0,v0,v16)
+	bdz	.Lv0
+
+	lvx	v1,off16,r4
+	lvx	v17,off16,r3
+	VPERM(v1,v1,v17,byteswap)
+	VPMSUMW(v1,v1,v17)
+	bdz	.Lv1
+
+	lvx	v2,off32,r4
+	lvx	v16,off32,r3
+	VPERM(v2,v2,v16,byteswap)
+	VPMSUMW(v2,v2,v16)
+	bdz	.Lv2
+
+	lvx	v3,off48,r4
+	lvx	v17,off48,r3
+	VPERM(v3,v3,v17,byteswap)
+	VPMSUMW(v3,v3,v17)
+	bdz	.Lv3
+
+	lvx	v4,off64,r4
+	lvx	v16,off64,r3
+	VPERM(v4,v4,v16,byteswap)
+	VPMSUMW(v4,v4,v16)
+	bdz	.Lv4
+
+	lvx	v5,off80,r4
+	lvx	v17,off80,r3
+	VPERM(v5,v5,v17,byteswap)
+	VPMSUMW(v5,v5,v17)
+	bdz	.Lv5
+
+	lvx	v6,off96,r4
+	lvx	v16,off96,r3
+	VPERM(v6,v6,v16,byteswap)
+	VPMSUMW(v6,v6,v16)
+	bdz	.Lv6
+
+	lvx	v7,off112,r4
+	lvx	v17,off112,r3
+	VPERM(v7,v7,v17,byteswap)
+	VPMSUMW(v7,v7,v17)
+	bdz	.Lv7
+
+	addi	r3,r3,128
+	addi	r4,r4,128
+
+	lvx	v8,0,r4
+	lvx	v16,0,r3
+	VPERM(v8,v8,v16,byteswap)
+	VPMSUMW(v8,v8,v16)
+	bdz	.Lv8
+
+	lvx	v9,off16,r4
+	lvx	v17,off16,r3
+	VPERM(v9,v9,v17,byteswap)
+	VPMSUMW(v9,v9,v17)
+	bdz	.Lv9
+
+	lvx	v10,off32,r4
+	lvx	v16,off32,r3
+	VPERM(v10,v10,v16,byteswap)
+	VPMSUMW(v10,v10,v16)
+	bdz	.Lv10
+
+	lvx	v11,off48,r4
+	lvx	v17,off48,r3
+	VPERM(v11,v11,v17,byteswap)
+	VPMSUMW(v11,v11,v17)
+	bdz	.Lv11
+
+	lvx	v12,off64,r4
+	lvx	v16,off64,r3
+	VPERM(v12,v12,v16,byteswap)
+	VPMSUMW(v12,v12,v16)
+	bdz	.Lv12
+
+	lvx	v13,off80,r4
+	lvx	v17,off80,r3
+	VPERM(v13,v13,v17,byteswap)
+	VPMSUMW(v13,v13,v17)
+	bdz	.Lv13
+
+	lvx	v14,off96,r4
+	lvx	v16,off96,r3
+	VPERM(v14,v14,v16,byteswap)
+	VPMSUMW(v14,v14,v16)
+	bdz	.Lv14
+
+	lvx	v15,off112,r4
+	lvx	v17,off112,r3
+	VPERM(v15,v15,v17,byteswap)
+	VPMSUMW(v15,v15,v17)
+
+.Lv15:	vxor	v19,v19,v15
+.Lv14:	vxor	v20,v20,v14
+.Lv13:	vxor	v19,v19,v13
+.Lv12:	vxor	v20,v20,v12
+.Lv11:	vxor	v19,v19,v11
+.Lv10:	vxor	v20,v20,v10
+.Lv9:	vxor	v19,v19,v9
+.Lv8:	vxor	v20,v20,v8
+.Lv7:	vxor	v19,v19,v7
+.Lv6:	vxor	v20,v20,v6
+.Lv5:	vxor	v19,v19,v5
+.Lv4:	vxor	v20,v20,v4
+.Lv3:	vxor	v19,v19,v3
+.Lv2:	vxor	v20,v20,v2
+.Lv1:	vxor	v19,v19,v1
+.Lv0:	vxor	v20,v20,v0
+
+	vxor	v0,v19,v20
+
+	b	.Lbarrett_reduction
+
+.Lzero:
+	mr	r3,r10
+	b	.Lout
+
+FUNC_END(__crc32_vpmsum)
diff --git a/src/rocksdb/util/crc32c_ppc_constants.h b/src/rocksdb/util/crc32c_ppc_constants.h
new file mode 100644
index 000000000..f6494cd01
--- /dev/null
+++ b/src/rocksdb/util/crc32c_ppc_constants.h
@@ -0,0 +1,900 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  Copyright (C) 2015, 2017 International Business Machines Corp.
+//  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#define CRC 0x1edc6f41
+#define REFLECT
+#define CRC_XOR
+
+#ifndef __ASSEMBLY__
+#ifdef CRC_TABLE
+static const unsigned int crc_table[] = {
+    0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c,
+    0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
+    0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 0x105ec76f, 0xe235446c,
+    0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+    0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc,
+    0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
+    0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35, 0xaa64d611, 0x580f5512,
+    0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+    0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad,
+    0x1642ae59, 0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
+    0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 0x417b1dbc, 0xb3109ebf,
+    0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f,
+    0xed03a29b, 0x1f682198, 0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
+    0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f,
+    0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+    0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e,
+    0x4767748a, 0xb50cf789, 0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
+    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e,
+    0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+    0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de,
+    0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
+    0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 0x082f63b7, 0xfa44e0b4,
+    0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b,
+    0xb4091bff, 0x466298fc, 0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
+    0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 0xa24bb5a6, 0x502036a5,
+    0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+    0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975,
+    0x0e330a81, 0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
+    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06, 0xcaa7a905,
+    0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+    0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8,
+    0xe52cc12c, 0x1747422f, 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
+    0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8,
+    0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78,
+    0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
+    0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6,
+    0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+    0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69,
+    0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
+    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351,
+};
+
+#endif
+
+#else
+#define MAX_SIZE 32768
+.constants :
+
+        /* Reduce 262144 kbits to 1024 bits */
+        /* x^261120 mod p(x)` << 1, x^261184 mod p(x)` << 1 */
+        .octa 0x00000000b6ca9e20000000009c37c408
+
+        /* x^260096 mod p(x)` << 1, x^260160 mod p(x)` << 1 */
+        .octa 0x00000000350249a800000001b51df26c
+
+        /* x^259072 mod p(x)` << 1, x^259136 mod p(x)` << 1 */
+        .octa 0x00000001862dac54000000000724b9d0
+
+        /* x^258048 mod p(x)` << 1, x^258112 mod p(x)` << 1 */
+        .octa 0x00000001d87fb48c00000001c00532fe
+
+        /* x^257024 mod p(x)` << 1, x^257088 mod p(x)` << 1 */
+        .octa 0x00000001f39b699e00000000f05a9362
+
+        /* x^256000 mod p(x)` << 1, x^256064 mod p(x)` << 1 */
+        .octa 0x0000000101da11b400000001e1007970
+
+        /* x^254976 mod p(x)` << 1, x^255040 mod p(x)` << 1 */
+        .octa 0x00000001cab571e000000000a57366ee
+
+        /* x^253952 mod p(x)` << 1, x^254016 mod p(x)` << 1 */
+        .octa 0x00000000c7020cfe0000000192011284
+
+        /* x^252928 mod p(x)` << 1, x^252992 mod p(x)` << 1 */
+        .octa 0x00000000cdaed1ae0000000162716d9a
+
+        /* x^251904 mod p(x)` << 1, x^251968 mod p(x)` << 1 */
+        .octa 0x00000001e804effc00000000cd97ecde
+
+        /* x^250880 mod p(x)` << 1, x^250944 mod p(x)` << 1 */
+        .octa 0x0000000077c3ea3a0000000058812bc0
+
+        /* x^249856 mod p(x)` << 1, x^249920 mod p(x)` << 1 */
+        .octa 0x0000000068df31b40000000088b8c12e
+
+        /* x^248832 mod p(x)` << 1, x^248896 mod p(x)` << 1 */
+        .octa 0x00000000b059b6c200000001230b234c
+
+        /* x^247808 mod p(x)` << 1, x^247872 mod p(x)` << 1 */
+        .octa 0x0000000145fb8ed800000001120b416e
+
+        /* x^246784 mod p(x)` << 1, x^246848 mod p(x)` << 1 */
+        .octa 0x00000000cbc0916800000001974aecb0
+
+        /* x^245760 mod p(x)` << 1, x^245824 mod p(x)` << 1 */
+        .octa 0x000000005ceeedc2000000008ee3f226
+
+        /* x^244736 mod p(x)` << 1, x^244800 mod p(x)` << 1 */
+        .octa 0x0000000047d74e8600000001089aba9a
+
+        /* x^243712 mod p(x)` << 1, x^243776 mod p(x)` << 1 */
+        .octa 0x00000001407e9e220000000065113872
+
+        /* x^242688 mod p(x)` << 1, x^242752 mod p(x)` << 1 */
+        .octa 0x00000001da967bda000000005c07ec10
+
+        /* x^241664 mod p(x)` << 1, x^241728 mod p(x)` << 1 */
+        .octa 0x000000006c8983680000000187590924
+
+        /* x^240640 mod p(x)` << 1, x^240704 mod p(x)` << 1 */
+        .octa 0x00000000f2d14c9800000000e35da7c6
+
+        /* x^239616 mod p(x)` << 1, x^239680 mod p(x)` << 1 */
+        .octa 0x00000001993c6ad4000000000415855a
+
+        /* x^238592 mod p(x)` << 1, x^238656 mod p(x)` << 1 */
+        .octa 0x000000014683d1ac0000000073617758
+
+        /* x^237568 mod p(x)` << 1, x^237632 mod p(x)` << 1 */
+        .octa 0x00000001a7c93e6c0000000176021d28
+
+        /* x^236544 mod p(x)` << 1, x^236608 mod p(x)` << 1 */
+        .octa 0x000000010211e90a00000001c358fd0a
+
+        /* x^235520 mod p(x)` << 1, x^235584 mod p(x)` << 1 */
+        .octa 0x000000001119403e00000001ff7a2c18
+
+        /* x^234496 mod p(x)` << 1, x^234560 mod p(x)` << 1 */
+        .octa 0x000000001c3261aa00000000f2d9f7e4
+
+        /* x^233472 mod p(x)` << 1, x^233536 mod p(x)` << 1 */
+        .octa 0x000000014e37a634000000016cf1f9c8
+
+        /* x^232448 mod p(x)` << 1, x^232512 mod p(x)` << 1 */
+        .octa 0x0000000073786c0c000000010af9279a
+
+        /* x^231424 mod p(x)` << 1, x^231488 mod p(x)` << 1 */
+        .octa 0x000000011dc037f80000000004f101e8
+
+        /* x^230400 mod p(x)` << 1, x^230464 mod p(x)` << 1 */
+        .octa 0x0000000031433dfc0000000070bcf184
+
+        /* x^229376 mod p(x)` << 1, x^229440 mod p(x)` << 1 */
+        .octa 0x000000009cde8348000000000a8de642
+
+        /* x^228352 mod p(x)` << 1, x^228416 mod p(x)` << 1 */
+        .octa 0x0000000038d3c2a60000000062ea130c
+
+        /* x^227328 mod p(x)` << 1, x^227392 mod p(x)` << 1 */
+        .octa 0x000000011b25f26000000001eb31cbb2
+
+        /* x^226304 mod p(x)` << 1, x^226368 mod p(x)` << 1 */
+        .octa 0x000000001629e6f00000000170783448
+
+        /* x^225280 mod p(x)` << 1, x^225344 mod p(x)` << 1 */
+        .octa 0x0000000160838b4c00000001a684b4c6
+
+        /* x^224256 mod p(x)` << 1, x^224320 mod p(x)` << 1 */
+        .octa 0x000000007a44011c00000000253ca5b4
+
+        /* x^223232 mod p(x)` << 1, x^223296 mod p(x)` << 1 */
+        .octa 0x00000000226f417a0000000057b4b1e2
+
+        /* x^222208 mod p(x)` << 1, x^222272 mod p(x)` << 1 */
+        .octa 0x0000000045eb2eb400000000b6bd084c
+
+        /* x^221184 mod p(x)` << 1, x^221248 mod p(x)` << 1 */
+        .octa 0x000000014459d70c0000000123c2d592
+
+        /* x^220160 mod p(x)` << 1, x^220224 mod p(x)` << 1 */
+        .octa 0x00000001d406ed8200000000159dafce
+
+        /* x^219136 mod p(x)` << 1, x^219200 mod p(x)` << 1 */
+        .octa 0x0000000160c8e1a80000000127e1a64e
+
+        /* x^218112 mod p(x)` << 1, x^218176 mod p(x)` << 1 */
+        .octa 0x0000000027ba80980000000056860754
+
+        /* x^217088 mod p(x)` << 1, x^217152 mod p(x)` << 1 */
+        .octa 0x000000006d92d01800000001e661aae8
+
+        /* x^216064 mod p(x)` << 1, x^216128 mod p(x)` << 1 */
+        .octa 0x000000012ed7e3f200000000f82c6166
+
+        /* x^215040 mod p(x)` << 1, x^215104 mod p(x)` << 1 */
+        .octa 0x000000002dc8778800000000c4f9c7ae
+
+        /* x^214016 mod p(x)` << 1, x^214080 mod p(x)` << 1 */
+        .octa 0x0000000018240bb80000000074203d20
+
+        /* x^212992 mod p(x)` << 1, x^213056 mod p(x)` << 1 */
+        .octa 0x000000001ad381580000000198173052
+
+        /* x^211968 mod p(x)` << 1, x^212032 mod p(x)` << 1 */
+        .octa 0x00000001396b78f200000001ce8aba54
+
+        /* x^210944 mod p(x)` << 1, x^211008 mod p(x)` << 1 */
+        .octa 0x000000011a68133400000001850d5d94
+
+        /* x^209920 mod p(x)` << 1, x^209984 mod p(x)` << 1 */
+        .octa 0x000000012104732e00000001d609239c
+
+        /* x^208896 mod p(x)` << 1, x^208960 mod p(x)` << 1 */
+        .octa 0x00000000a140d90c000000001595f048
+
+        /* x^207872 mod p(x)` << 1, x^207936 mod p(x)` << 1 */
+        .octa 0x00000001b7215eda0000000042ccee08
+
+        /* x^206848 mod p(x)` << 1, x^206912 mod p(x)` << 1 */
+        .octa 0x00000001aaf1df3c000000010a389d74
+
+        /* x^205824 mod p(x)` << 1, x^205888 mod p(x)` << 1 */
+        .octa 0x0000000029d15b8a000000012a840da6
+
+        /* x^204800 mod p(x)` << 1, x^204864 mod p(x)` << 1 */
+        .octa 0x00000000f1a96922000000001d181c0c
+
+        /* x^203776 mod p(x)` << 1, x^203840 mod p(x)` << 1 */
+        .octa 0x00000001ac80d03c0000000068b7d1f6
+
+        /* x^202752 mod p(x)` << 1, x^202816 mod p(x)` << 1 */
+        .octa 0x000000000f11d56a000000005b0f14fc
+
+        /* x^201728 mod p(x)` << 1, x^201792 mod p(x)` << 1 */
+        .octa 0x00000001f1c022a20000000179e9e730
+
+        /* x^200704 mod p(x)` << 1, x^200768 mod p(x)` << 1 */
+        .octa 0x0000000173d00ae200000001ce1368d6
+
+        /* x^199680 mod p(x)` << 1, x^199744 mod p(x)` << 1 */
+        .octa 0x00000001d4ffe4ac0000000112c3a84c
+
+        /* x^198656 mod p(x)` << 1, x^198720 mod p(x)` << 1 */
+        .octa 0x000000016edc5ae400000000de940fee
+
+        /* x^197632 mod p(x)` << 1, x^197696 mod p(x)` << 1 */
+        .octa 0x00000001f1a0214000000000fe896b7e
+
+        /* x^196608 mod p(x)` << 1, x^196672 mod p(x)` << 1 */
+        .octa 0x00000000ca0b28a000000001f797431c
+
+        /* x^195584 mod p(x)` << 1, x^195648 mod p(x)` << 1 */
+        .octa 0x00000001928e30a20000000053e989ba
+
+        /* x^194560 mod p(x)` << 1, x^194624 mod p(x)` << 1 */
+        .octa 0x0000000097b1b002000000003920cd16
+
+        /* x^193536 mod p(x)` << 1, x^193600 mod p(x)` << 1 */
+        .octa 0x00000000b15bf90600000001e6f579b8
+
+        /* x^192512 mod p(x)` << 1, x^192576 mod p(x)` << 1 */
+        .octa 0x00000000411c5d52000000007493cb0a
+
+        /* x^191488 mod p(x)` << 1, x^191552 mod p(x)` << 1 */
+        .octa 0x00000001c36f330000000001bdd376d8
+
+        /* x^190464 mod p(x)` << 1, x^190528 mod p(x)` << 1 */
+        .octa 0x00000001119227e0000000016badfee6
+
+        /* x^189440 mod p(x)` << 1, x^189504 mod p(x)` << 1 */
+        .octa 0x00000000114d47020000000071de5c58
+
+        /* x^188416 mod p(x)` << 1, x^188480 mod p(x)` << 1 */
+        .octa 0x00000000458b5b9800000000453f317c
+
+        /* x^187392 mod p(x)` << 1, x^187456 mod p(x)` << 1 */
+        .octa 0x000000012e31fb8e0000000121675cce
+
+        /* x^186368 mod p(x)` << 1, x^186432 mod p(x)` << 1 */
+        .octa 0x000000005cf619d800000001f409ee92
+
+        /* x^185344 mod p(x)` << 1, x^185408 mod p(x)` << 1 */
+        .octa 0x0000000063f4d8b200000000f36b9c88
+
+        /* x^184320 mod p(x)` << 1, x^184384 mod p(x)` << 1 */
+        .octa 0x000000004138dc8a0000000036b398f4
+
+        /* x^183296 mod p(x)` << 1, x^183360 mod p(x)` << 1 */
+        .octa 0x00000001d29ee8e000000001748f9adc
+
+        /* x^182272 mod p(x)` << 1, x^182336 mod p(x)` << 1 */
+        .octa 0x000000006a08ace800000001be94ec00
+
+        /* x^181248 mod p(x)` << 1, x^181312 mod p(x)` << 1 */
+        .octa 0x0000000127d4201000000000b74370d6
+
+        /* x^180224 mod p(x)` << 1, x^180288 mod p(x)` << 1 */
+        .octa 0x0000000019d76b6200000001174d0b98
+
+        /* x^179200 mod p(x)` << 1, x^179264 mod p(x)` << 1 */
+        .octa 0x00000001b1471f6e00000000befc06a4
+
+        /* x^178176 mod p(x)` << 1, x^178240 mod p(x)` << 1 */
+        .octa 0x00000001f64c19cc00000001ae125288
+
+        /* x^177152 mod p(x)` << 1, x^177216 mod p(x)` << 1 */
+        .octa 0x00000000003c0ea00000000095c19b34
+
+        /* x^176128 mod p(x)` << 1, x^176192 mod p(x)` << 1 */
+        .octa 0x000000014d73abf600000001a78496f2
+
+        /* x^175104 mod p(x)` << 1, x^175168 mod p(x)` << 1 */
+        .octa 0x00000001620eb84400000001ac5390a0
+
+        /* x^174080 mod p(x)` << 1, x^174144 mod p(x)` << 1 */
+        .octa 0x0000000147655048000000002a80ed6e
+
+        /* x^173056 mod p(x)` << 1, x^173120 mod p(x)` << 1 */
+        .octa 0x0000000067b5077e00000001fa9b0128
+
+        /* x^172032 mod p(x)` << 1, x^172096 mod p(x)` << 1 */
+        .octa 0x0000000010ffe20600000001ea94929e
+
+        /* x^171008 mod p(x)` << 1, x^171072 mod p(x)` << 1 */
+        .octa 0x000000000fee8f1e0000000125f4305c
+
+        /* x^169984 mod p(x)` << 1, x^170048 mod p(x)` << 1 */
+        .octa 0x00000001da26fbae00000001471e2002
+
+        /* x^168960 mod p(x)` << 1, x^169024 mod p(x)` << 1 */
+        .octa 0x00000001b3a8bd880000000132d2253a
+
+        /* x^167936 mod p(x)` << 1, x^168000 mod p(x)` << 1 */
+        .octa 0x00000000e8f3898e00000000f26b3592
+
+        /* x^166912 mod p(x)` << 1, x^166976 mod p(x)` << 1 */
+        .octa 0x00000000b0d0d28c00000000bc8b67b0
+
+        /* x^165888 mod p(x)` << 1, x^165952 mod p(x)` << 1 */
+        .octa 0x0000000030f2a798000000013a826ef2
+
+        /* x^164864 mod p(x)` << 1, x^164928 mod p(x)` << 1 */
+        .octa 0x000000000fba10020000000081482c84
+
+        /* x^163840 mod p(x)` << 1, x^163904 mod p(x)` << 1 */
+        .octa 0x00000000bdb9bd7200000000e77307c2
+
+        /* x^162816 mod p(x)` << 1, x^162880 mod p(x)` << 1 */
+        .octa 0x0000000075d3bf5a00000000d4a07ec8
+
+        /* x^161792 mod p(x)` << 1, x^161856 mod p(x)` << 1 */
+        .octa 0x00000000ef1f98a00000000017102100
+
+        /* x^160768 mod p(x)` << 1, x^160832 mod p(x)` << 1 */
+        .octa 0x00000000689c760200000000db406486
+
+        /* x^159744 mod p(x)` << 1, x^159808 mod p(x)` << 1 */
+        .octa 0x000000016d5fa5fe0000000192db7f88
+
+        /* x^158720 mod p(x)` << 1, x^158784 mod p(x)` << 1 */
+        .octa 0x00000001d0d2b9ca000000018bf67b1e
+
+        /* x^157696 mod p(x)` << 1, x^157760 mod p(x)` << 1 */
+        .octa 0x0000000041e7b470000000007c09163e
+
+        /* x^156672 mod p(x)` << 1, x^156736 mod p(x)` << 1 */
+        .octa 0x00000001cbb6495e000000000adac060
+
+        /* x^155648 mod p(x)` << 1, x^155712 mod p(x)` << 1 */
+        .octa 0x000000010052a0b000000000bd8316ae
+
+        /* x^154624 mod p(x)` << 1, x^154688 mod p(x)` << 1 */
+        .octa 0x00000001d8effb5c000000019f09ab54
+
+        /* x^153600 mod p(x)` << 1, x^153664 mod p(x)` << 1 */
+        .octa 0x00000001d969853c0000000125155542
+
+        /* x^152576 mod p(x)` << 1, x^152640 mod p(x)` << 1 */
+        .octa 0x00000000523ccce2000000018fdb5882
+
+        /* x^151552 mod p(x)` << 1, x^151616 mod p(x)` << 1 */
+        .octa 0x000000001e2436bc00000000e794b3f4
+
+        /* x^150528 mod p(x)` << 1, x^150592 mod p(x)` << 1 */
+        .octa 0x00000000ddd1c3a2000000016f9bb022
+
+        /* x^149504 mod p(x)` << 1, x^149568 mod p(x)` << 1 */
+        .octa 0x0000000019fcfe3800000000290c9978
+
+        /* x^148480 mod p(x)` << 1, x^148544 mod p(x)` << 1 */
+        .octa 0x00000001ce95db640000000083c0f350
+
+        /* x^147456 mod p(x)` << 1, x^147520 mod p(x)` << 1 */
+        .octa 0x00000000af5828060000000173ea6628
+
+        /* x^146432 mod p(x)` << 1, x^146496 mod p(x)` << 1 */
+        .octa 0x00000001006388f600000001c8b4e00a
+
+        /* x^145408 mod p(x)` << 1, x^145472 mod p(x)` << 1 */
+        .octa 0x0000000179eca00a00000000de95d6aa
+
+        /* x^144384 mod p(x)` << 1, x^144448 mod p(x)` << 1 */
+        .octa 0x0000000122410a6a000000010b7f7248
+
+        /* x^143360 mod p(x)` << 1, x^143424 mod p(x)` << 1 */
+        .octa 0x000000004288e87c00000001326e3a06
+
+        /* x^142336 mod p(x)` << 1, x^142400 mod p(x)` << 1 */
+        .octa 0x000000016c5490da00000000bb62c2e6
+
+        /* x^141312 mod p(x)` << 1, x^141376 mod p(x)` << 1 */
+        .octa 0x00000000d1c71f6e0000000156a4b2c2
+
+        /* x^140288 mod p(x)` << 1, x^140352 mod p(x)` << 1 */
+        .octa 0x00000001b4ce08a6000000011dfe763a
+
+        /* x^139264 mod p(x)` << 1, x^139328 mod p(x)` << 1 */
+        .octa 0x00000001466ba60c000000007bcca8e2
+
+        /* x^138240 mod p(x)` << 1, x^138304 mod p(x)` << 1 */
+        .octa 0x00000001f6c488a40000000186118faa
+
+        /* x^137216 mod p(x)` << 1, x^137280 mod p(x)` << 1 */
+        .octa 0x000000013bfb06820000000111a65a88
+
+        /* x^136192 mod p(x)` << 1, x^136256 mod p(x)` << 1 */
+        .octa 0x00000000690e9e54000000003565e1c4
+
+        /* x^135168 mod p(x)` << 1, x^135232 mod p(x)` << 1 */
+        .octa 0x00000000281346b6000000012ed02a82
+
+        /* x^134144 mod p(x)` << 1, x^134208 mod p(x)` << 1 */
+        .octa 0x000000015646402400000000c486ecfc
+
+        /* x^133120 mod p(x)` << 1, x^133184 mod p(x)` << 1 */
+        .octa 0x000000016063a8dc0000000001b951b2
+
+        /* x^132096 mod p(x)` << 1, x^132160 mod p(x)` << 1 */
+        .octa 0x0000000116a663620000000048143916
+
+        /* x^131072 mod p(x)` << 1, x^131136 mod p(x)` << 1 */
+        .octa 0x000000017e8aa4d200000001dc2ae124
+
+        /* x^130048 mod p(x)` << 1, x^130112 mod p(x)` << 1 */
+        .octa 0x00000001728eb10c00000001416c58d6
+
+        /* x^129024 mod p(x)` << 1, x^129088 mod p(x)` << 1 */
+        .octa 0x00000001b08fd7fa00000000a479744a
+
+        /* x^128000 mod p(x)` << 1, x^128064 mod p(x)` << 1 */
+        .octa 0x00000001092a16e80000000096ca3a26
+
+        /* x^126976 mod p(x)` << 1, x^127040 mod p(x)` << 1 */
+        .octa 0x00000000a505637c00000000ff223d4e
+
+        /* x^125952 mod p(x)` << 1, x^126016 mod p(x)` << 1 */
+        .octa 0x00000000d94869b2000000010e84da42
+
+        /* x^124928 mod p(x)` << 1, x^124992 mod p(x)` << 1 */
+        .octa 0x00000001c8b203ae00000001b61ba3d0
+
+        /* x^123904 mod p(x)` << 1, x^123968 mod p(x)` << 1 */
+        .octa 0x000000005704aea000000000680f2de8
+
+        /* x^122880 mod p(x)` << 1, x^122944 mod p(x)` << 1 */
+        .octa 0x000000012e295fa2000000008772a9a8
+
+        /* x^121856 mod p(x)` << 1, x^121920 mod p(x)` << 1 */
+        .octa 0x000000011d0908bc0000000155f295bc
+
+        /* x^120832 mod p(x)` << 1, x^120896 mod p(x)` << 1 */
+        .octa 0x0000000193ed97ea00000000595f9282
+
+        /* x^119808 mod p(x)` << 1, x^119872 mod p(x)` << 1 */
+        .octa 0x000000013a0f1c520000000164b1c25a
+
+        /* x^118784 mod p(x)` << 1, x^118848 mod p(x)` << 1 */
+        .octa 0x000000010c2c40c000000000fbd67c50
+
+        /* x^117760 mod p(x)` << 1, x^117824 mod p(x)` << 1 */
+        .octa 0x00000000ff6fac3e0000000096076268
+
+        /* x^116736 mod p(x)` << 1, x^116800 mod p(x)` << 1 */
+        .octa 0x000000017b3609c000000001d288e4cc
+
+        /* x^115712 mod p(x)` << 1, x^115776 mod p(x)` << 1 */
+        .octa 0x0000000088c8c92200000001eaac1bdc
+
+        /* x^114688 mod p(x)` << 1, x^114752 mod p(x)` << 1 */
+        .octa 0x00000001751baae600000001f1ea39e2
+
+        /* x^113664 mod p(x)` << 1, x^113728 mod p(x)` << 1 */
+        .octa 0x000000010795297200000001eb6506fc
+
+        /* x^112640 mod p(x)` << 1, x^112704 mod p(x)` << 1 */
+        .octa 0x0000000162b00abe000000010f806ffe
+
+        /* x^111616 mod p(x)` << 1, x^111680 mod p(x)` << 1 */
+        .octa 0x000000000d7b404c000000010408481e
+
+        /* x^110592 mod p(x)` << 1, x^110656 mod p(x)` << 1 */
+        .octa 0x00000000763b13d40000000188260534
+
+        /* x^109568 mod p(x)` << 1, x^109632 mod p(x)` << 1 */
+        .octa 0x00000000f6dc22d80000000058fc73e0
+
+        /* x^108544 mod p(x)` << 1, x^108608 mod p(x)` << 1 */
+        .octa 0x000000007daae06000000000391c59b8
+
+        /* x^107520 mod p(x)` << 1, x^107584 mod p(x)` << 1 */
+        .octa 0x000000013359ab7c000000018b638400
+
+        /* x^106496 mod p(x)` << 1, x^106560 mod p(x)` << 1 */
+        .octa 0x000000008add438a000000011738f5c4
+
+        /* x^105472 mod p(x)` << 1, x^105536 mod p(x)` << 1 */
+        .octa 0x00000001edbefdea000000008cf7c6da
+
+        /* x^104448 mod p(x)` << 1, x^104512 mod p(x)` << 1 */
+        .octa 0x000000004104e0f800000001ef97fb16
+
+        /* x^103424 mod p(x)` << 1, x^103488 mod p(x)` << 1 */
+        .octa 0x00000000b48a82220000000102130e20
+
+        /* x^102400 mod p(x)` << 1, x^102464 mod p(x)` << 1 */
+        .octa 0x00000001bcb4684400000000db968898
+
+        /* x^101376 mod p(x)` << 1, x^101440 mod p(x)` << 1 */
+        .octa 0x000000013293ce0a00000000b5047b5e
+
+        /* x^100352 mod p(x)` << 1, x^100416 mod p(x)` << 1 */
+        .octa 0x00000001710d0844000000010b90fdb2
+
+        /* x^99328 mod p(x)` << 1, x^99392 mod p(x)` << 1 */
+        .octa 0x0000000117907f6e000000004834a32e
+
+        /* x^98304 mod p(x)` << 1, x^98368 mod p(x)` << 1 */
+        .octa 0x0000000087ddf93e0000000059c8f2b0
+
+        /* x^97280 mod p(x)` << 1, x^97344 mod p(x)` << 1 */
+        .octa 0x000000005970e9b00000000122cec508
+
+        /* x^96256 mod p(x)` << 1, x^96320 mod p(x)` << 1 */
+        .octa 0x0000000185b2b7d0000000000a330cda
+
+        /* x^95232 mod p(x)` << 1, x^95296 mod p(x)` << 1 */
+        .octa 0x00000001dcee0efc000000014a47148c
+
+        /* x^94208 mod p(x)` << 1, x^94272 mod p(x)` << 1 */
+        .octa 0x0000000030da27220000000042c61cb8
+
+        /* x^93184 mod p(x)` << 1, x^93248 mod p(x)` << 1 */
+        .octa 0x000000012f925a180000000012fe6960
+
+        /* x^92160 mod p(x)` << 1, x^92224 mod p(x)` << 1 */
+        .octa 0x00000000dd2e357c00000000dbda2c20
+
+        /* x^91136 mod p(x)` << 1, x^91200 mod p(x)` << 1 */
+        .octa 0x00000000071c80de000000011122410c
+
+        /* x^90112 mod p(x)` << 1, x^90176 mod p(x)` << 1 */
+        .octa 0x000000011513140a00000000977b2070
+
+        /* x^89088 mod p(x)` << 1, x^89152 mod p(x)` << 1 */
+        .octa 0x00000001df876e8e000000014050438e
+
+        /* x^88064 mod p(x)` << 1, x^88128 mod p(x)` << 1 */
+        .octa 0x000000015f81d6ce0000000147c840e8
+
+        /* x^87040 mod p(x)` << 1, x^87104 mod p(x)` << 1 */
+        .octa 0x000000019dd94dbe00000001cc7c88ce
+
+        /* x^86016 mod p(x)` << 1, x^86080 mod p(x)` << 1 */
+        .octa 0x00000001373d206e00000001476b35a4
+
+        /* x^84992 mod p(x)` << 1, x^85056 mod p(x)` << 1 */
+        .octa 0x00000000668ccade000000013d52d508
+
+        /* x^83968 mod p(x)` << 1, x^84032 mod p(x)` << 1 */
+        .octa 0x00000001b192d268000000008e4be32e
+
+        /* x^82944 mod p(x)` << 1, x^83008 mod p(x)` << 1 */
+        .octa 0x00000000e30f3a7800000000024120fe
+
+        /* x^81920 mod p(x)` << 1, x^81984 mod p(x)` << 1 */
+        .octa 0x000000010ef1f7bc00000000ddecddb4
+
+        /* x^80896 mod p(x)` << 1, x^80960 mod p(x)` << 1 */
+        .octa 0x00000001f5ac738000000000d4d403bc
+
+        /* x^79872 mod p(x)` << 1, x^79936 mod p(x)` << 1 */
+        .octa 0x000000011822ea7000000001734b89aa
+
+        /* x^78848 mod p(x)` << 1, x^78912 mod p(x)` << 1 */
+        .octa 0x00000000c3a33848000000010e7a58d6
+
+        /* x^77824 mod p(x)` << 1, x^77888 mod p(x)` << 1 */
+        .octa 0x00000001bd151c2400000001f9f04e9c
+
+        /* x^76800 mod p(x)` << 1, x^76864 mod p(x)` << 1 */
+        .octa 0x0000000056002d7600000000b692225e
+
+        /* x^75776 mod p(x)` << 1, x^75840 mod p(x)` << 1 */
+        .octa 0x000000014657c4f4000000019b8d3f3e
+
+        /* x^74752 mod p(x)` << 1, x^74816 mod p(x)` << 1 */
+        .octa 0x0000000113742d7c00000001a874f11e
+
+        /* x^73728 mod p(x)` << 1, x^73792 mod p(x)` << 1 */
+        .octa 0x000000019c5920ba000000010d5a4254
+
+        /* x^72704 mod p(x)` << 1, x^72768 mod p(x)` << 1 */
+        .octa 0x000000005216d2d600000000bbb2f5d6
+
+        /* x^71680 mod p(x)` << 1, x^71744 mod p(x)` << 1 */
+        .octa 0x0000000136f5ad8a0000000179cc0e36
+
+        /* x^70656 mod p(x)` << 1, x^70720 mod p(x)` << 1 */
+        .octa 0x000000018b07beb600000001dca1da4a
+
+        /* x^69632 mod p(x)` << 1, x^69696 mod p(x)` << 1 */
+        .octa 0x00000000db1e93b000000000feb1a192
+
+        /* x^68608 mod p(x)` << 1, x^68672 mod p(x)` << 1 */
+        .octa 0x000000000b96fa3a00000000d1eeedd6
+
+        /* x^67584 mod p(x)` << 1, x^67648 mod p(x)` << 1 */
+        .octa 0x00000001d9968af0000000008fad9bb4
+
+        /* x^66560 mod p(x)` << 1, x^66624 mod p(x)` << 1 */
+        .octa 0x000000000e4a77a200000001884938e4
+
+        /* x^65536 mod p(x)` << 1, x^65600 mod p(x)` << 1 */
+        .octa 0x00000000508c2ac800000001bc2e9bc0
+
+        /* x^64512 mod p(x)` << 1, x^64576 mod p(x)` << 1 */
+        .octa 0x0000000021572a8000000001f9658a68
+
+        /* x^63488 mod p(x)` << 1, x^63552 mod p(x)` << 1 */
+        .octa 0x00000001b859daf2000000001b9224fc
+
+        /* x^62464 mod p(x)` << 1, x^62528 mod p(x)` << 1 */
+        .octa 0x000000016f7884740000000055b2fb84
+
+        /* x^61440 mod p(x)` << 1, x^61504 mod p(x)` << 1 */
+        .octa 0x00000001b438810e000000018b090348
+
+        /* x^60416 mod p(x)` << 1, x^60480 mod p(x)` << 1 */
+        .octa 0x0000000095ddc6f2000000011ccbd5ea
+
+        /* x^59392 mod p(x)` << 1, x^59456 mod p(x)` << 1 */
+        .octa 0x00000001d977c20c0000000007ae47f8
+
+        /* x^58368 mod p(x)` << 1, x^58432 mod p(x)` << 1 */
+        .octa 0x00000000ebedb99a0000000172acbec0
+
+        /* x^57344 mod p(x)` << 1, x^57408 mod p(x)` << 1 */
+        .octa 0x00000001df9e9e9200000001c6e3ff20
+
+        /* x^56320 mod p(x)` << 1, x^56384 mod p(x)` << 1 */
+        .octa 0x00000001a4a3f95200000000e1b38744
+
+        /* x^55296 mod p(x)` << 1, x^55360 mod p(x)` << 1 */
+        .octa 0x00000000e2f5122000000000791585b2
+
+        /* x^54272 mod p(x)` << 1, x^54336 mod p(x)` << 1 */
+        .octa 0x000000004aa01f3e00000000ac53b894
+
+        /* x^53248 mod p(x)` << 1, x^53312 mod p(x)` << 1 */
+        .octa 0x00000000b3e90a5800000001ed5f2cf4
+
+        /* x^52224 mod p(x)` << 1, x^52288 mod p(x)` << 1 */
+        .octa 0x000000000c9ca2aa00000001df48b2e0
+
+        /* x^51200 mod p(x)` << 1, x^51264 mod p(x)` << 1 */
+        .octa 0x000000015168231600000000049c1c62
+
+        /* x^50176 mod p(x)` << 1, x^50240 mod p(x)` << 1 */
+        .octa 0x0000000036fce78c000000017c460c12
+
+        /* x^49152 mod p(x)` << 1, x^49216 mod p(x)` << 1 */
+        .octa 0x000000009037dc10000000015be4da7e
+
+        /* x^48128 mod p(x)` << 1, x^48192 mod p(x)` << 1 */
+        .octa 0x00000000d3298582000000010f38f668
+
+        /* x^47104 mod p(x)` << 1, x^47168 mod p(x)` << 1 */
+        .octa 0x00000001b42e8ad60000000039f40a00
+
+        /* x^46080 mod p(x)` << 1, x^46144 mod p(x)` << 1 */
+        .octa 0x00000000142a983800000000bd4c10c4
+
+        /* x^45056 mod p(x)` << 1, x^45120 mod p(x)` << 1 */
+        .octa 0x0000000109c7f1900000000042db1d98
+
+        /* x^44032 mod p(x)` << 1, x^44096 mod p(x)` << 1 */
+        .octa 0x0000000056ff931000000001c905bae6
+
+        /* x^43008 mod p(x)` << 1, x^43072 mod p(x)` << 1 */
+        .octa 0x00000001594513aa00000000069d40ea
+
+        /* x^41984 mod p(x)` << 1, x^42048 mod p(x)` << 1 */
+        .octa 0x00000001e3b5b1e8000000008e4fbad0
+
+        /* x^40960 mod p(x)` << 1, x^41024 mod p(x)` << 1 */
+        .octa 0x000000011dd5fc080000000047bedd46
+
+        /* x^39936 mod p(x)` << 1, x^40000 mod p(x)` << 1 */
+        .octa 0x00000001675f0cc20000000026396bf8
+
+        /* x^38912 mod p(x)` << 1, x^38976 mod p(x)` << 1 */
+        .octa 0x00000000d1c8dd4400000000379beb92
+
+        /* x^37888 mod p(x)` << 1, x^37952 mod p(x)` << 1 */
+        .octa 0x0000000115ebd3d8000000000abae54a
+
+        /* x^36864 mod p(x)` << 1, x^36928 mod p(x)` << 1 */
+        .octa 0x00000001ecbd0dac0000000007e6a128
+
+        /* x^35840 mod p(x)` << 1, x^35904 mod p(x)` << 1 */
+        .octa 0x00000000cdf67af2000000000ade29d2
+
+        /* x^34816 mod p(x)` << 1, x^34880 mod p(x)` << 1 */
+        .octa 0x000000004c01ff4c00000000f974c45c
+
+        /* x^33792 mod p(x)` << 1, x^33856 mod p(x)` << 1 */
+        .octa 0x00000000f2d8657e00000000e77ac60a
+
+        /* x^32768 mod p(x)` << 1, x^32832 mod p(x)` << 1 */
+        .octa 0x000000006bae74c40000000145895816
+
+        /* x^31744 mod p(x)` << 1, x^31808 mod p(x)` << 1 */
+        .octa 0x0000000152af8aa00000000038e362be
+
+        /* x^30720 mod p(x)` << 1, x^30784 mod p(x)` << 1 */
+        .octa 0x0000000004663802000000007f991a64
+
+        /* x^29696 mod p(x)` << 1, x^29760 mod p(x)` << 1 */
+        .octa 0x00000001ab2f5afc00000000fa366d3a
+
+        /* x^28672 mod p(x)` << 1, x^28736 mod p(x)` << 1 */
+        .octa 0x0000000074a4ebd400000001a2bb34f0
+
+        /* x^27648 mod p(x)` << 1, x^27712 mod p(x)` << 1 */
+        .octa 0x00000001d7ab3a4c0000000028a9981e
+
+        /* x^26624 mod p(x)` << 1, x^26688 mod p(x)` << 1 */
+        .octa 0x00000001a8da60c600000001dbc672be
+
+        /* x^25600 mod p(x)` << 1, x^25664 mod p(x)` << 1 */
+        .octa 0x000000013cf6382000000000b04d77f6
+
+        /* x^24576 mod p(x)` << 1, x^24640 mod p(x)` << 1 */
+        .octa 0x00000000bec12e1e0000000124400d96
+
+        /* x^23552 mod p(x)` << 1, x^23616 mod p(x)` << 1 */
+        .octa 0x00000001c6368010000000014ca4b414
+
+        /* x^22528 mod p(x)` << 1, x^22592 mod p(x)` << 1 */
+        .octa 0x00000001e6e78758000000012fe2c938
+
+        /* x^21504 mod p(x)` << 1, x^21568 mod p(x)` << 1 */
+        .octa 0x000000008d7f2b3c00000001faed01e6
+
+        /* x^20480 mod p(x)` << 1, x^20544 mod p(x)` << 1 */
+        .octa 0x000000016b4a156e000000007e80ecfe
+
+        /* x^19456 mod p(x)` << 1, x^19520 mod p(x)` << 1 */
+        .octa 0x00000001c63cfeb60000000098daee94
+
+        /* x^18432 mod p(x)` << 1, x^18496 mod p(x)` << 1 */
+        .octa 0x000000015f902670000000010a04edea
+
+        /* x^17408 mod p(x)` << 1, x^17472 mod p(x)` << 1 */
+        .octa 0x00000001cd5de11e00000001c00b4524
+
+        /* x^16384 mod p(x)` << 1, x^16448 mod p(x)` << 1 */
+        .octa 0x000000001acaec540000000170296550
+
+        /* x^15360 mod p(x)` << 1, x^15424 mod p(x)` << 1 */
+        .octa 0x000000002bd0ca780000000181afaa48
+
+        /* x^14336 mod p(x)` << 1, x^14400 mod p(x)` << 1 */
+        .octa 0x0000000032d63d5c0000000185a31ffa
+
+        /* x^13312 mod p(x)` << 1, x^13376 mod p(x)` << 1 */
+        .octa 0x000000001c6d4e4c000000002469f608
+
+        /* x^12288 mod p(x)` << 1, x^12352 mod p(x)` << 1 */
+        .octa 0x0000000106a60b92000000006980102a
+
+        /* x^11264 mod p(x)` << 1, x^11328 mod p(x)` << 1 */
+        .octa 0x00000000d3855e120000000111ea9ca8
+
+        /* x^10240 mod p(x)` << 1, x^10304 mod p(x)` << 1 */
+        .octa 0x00000000e312563600000001bd1d29ce
+
+        /* x^9216 mod p(x)` << 1, x^9280 mod p(x)` << 1 */
+        .octa 0x000000009e8f7ea400000001b34b9580
+
+        /* x^8192 mod p(x)` << 1, x^8256 mod p(x)` << 1 */
+        .octa 0x00000001c82e562c000000003076054e
+
+        /* x^7168 mod p(x)` << 1, x^7232 mod p(x)` << 1 */
+        .octa 0x00000000ca9f09ce000000012a608ea4
+
+        /* x^6144 mod p(x)` << 1, x^6208 mod p(x)` << 1 */
+        .octa 0x00000000c63764e600000000784d05fe
+
+        /* x^5120 mod p(x)` << 1, x^5184 mod p(x)` << 1 */
+        .octa 0x0000000168d2e49e000000016ef0d82a
+
+        /* x^4096 mod p(x)` << 1, x^4160 mod p(x)` << 1 */
+        .octa 0x00000000e986c1480000000075bda454
+
+        /* x^3072 mod p(x)` << 1, x^3136 mod p(x)` << 1 */
+        .octa 0x00000000cfb65894000000003dc0a1c4
+
+        /* x^2048 mod p(x)` << 1, x^2112 mod p(x)` << 1 */
+        .octa 0x0000000111cadee400000000e9a5d8be
+
+        /* x^1024 mod p(x)` << 1, x^1088 mod p(x)` << 1 */
+        .octa 0x0000000171fb63ce00000001609bc4b4
+
+        .short_constants :
+
+        /* Reduce final 1024-2048 bits to 64 bits, shifting 32 bits to include
+           the trailing 32 bits of zeros */
+        /* x^1952 mod p(x)`, x^1984 mod p(x)`, x^2016 mod p(x)`, x^2048 mod
+           p(x)` */
+        .octa 0x7fec2963e5bf80485cf015c388e56f72
+
+        /* x^1824 mod p(x)`, x^1856 mod p(x)`, x^1888 mod p(x)`, x^1920 mod
+           p(x)` */
+        .octa 0x38e888d4844752a9963a18920246e2e6
+
+        /* x^1696 mod p(x)`, x^1728 mod p(x)`, x^1760 mod p(x)`, x^1792 mod
+           p(x)` */
+        .octa 0x42316c00730206ad419a441956993a31
+
+        /* x^1568 mod p(x)`, x^1600 mod p(x)`, x^1632 mod p(x)`, x^1664 mod
+           p(x)` */
+        .octa 0x543d5c543e65ddf9924752ba2b830011
+
+        /* x^1440 mod p(x)`, x^1472 mod p(x)`, x^1504 mod p(x)`, x^1536 mod
+           p(x)` */
+        .octa 0x78e87aaf56767c9255bd7f9518e4a304
+
+        /* x^1312 mod p(x)`, x^1344 mod p(x)`, x^1376 mod p(x)`, x^1408 mod
+           p(x)` */
+        .octa 0x8f68fcec1903da7f6d76739fe0553f1e
+
+        /* x^1184 mod p(x)`, x^1216 mod p(x)`, x^1248 mod p(x)`, x^1280 mod
+           p(x)` */
+        .octa 0x3f4840246791d588c133722b1fe0b5c3
+
+        /* x^1056 mod p(x)`, x^1088 mod p(x)`, x^1120 mod p(x)`, x^1152 mod
+           p(x)` */
+        .octa 0x34c96751b04de25a64b67ee0e55ef1f3
+
+        /* x^928 mod p(x)`, x^960 mod p(x)`, x^992 mod p(x)`, x^1024 mod p(x)`
+         */
+        .octa 0x156c8e180b4a395b069db049b8fdb1e7
+
+        /* x^800 mod p(x)`, x^832 mod p(x)`, x^864 mod p(x)`, x^896 mod p(x)` */
+        .octa 0xe0b99ccbe661f7bea11bfaf3c9e90b9e
+
+        /* x^672 mod p(x)`, x^704 mod p(x)`, x^736 mod p(x)`, x^768 mod p(x)` */
+        .octa 0x041d37768cd75659817cdc5119b29a35
+
+        /* x^544 mod p(x)`, x^576 mod p(x)`, x^608 mod p(x)`, x^640 mod p(x)` */
+        .octa 0x3a0777818cfaa9651ce9d94b36c41f1c
+
+        /* x^416 mod p(x)`, x^448 mod p(x)`, x^480 mod p(x)`, x^512 mod p(x)` */
+        .octa 0x0e148e8252377a554f256efcb82be955
+
+        /* x^288 mod p(x)`, x^320 mod p(x)`, x^352 mod p(x)`, x^384 mod p(x)` */
+        .octa 0x9c25531d19e65ddeec1631edb2dea967
+
+        /* x^160 mod p(x)`, x^192 mod p(x)`, x^224 mod p(x)`, x^256 mod p(x)` */
+        .octa 0x790606ff9957c0a65d27e147510ac59a
+
+        /* x^32 mod p(x)`, x^64 mod p(x)`, x^96 mod p(x)`, x^128 mod p(x)` */
+        .octa 0x82f63b786ea2d55ca66805eb18b8ea18
+
+        .barrett_constants :
+        /* 33 bit reflected Barrett constant m - (4^32)/n */
+        .octa 0x000000000000000000000000dea713f1 /* x^64 div p(x)` */
+        /* 33 bit reflected Barrett constant n */
+        .octa 0x00000000000000000000000105ec76f1
+#endif
diff --git a/src/rocksdb/util/crc32c_test.cc b/src/rocksdb/util/crc32c_test.cc
new file mode 100644
index 000000000..3e4f7396e
--- /dev/null
+++ b/src/rocksdb/util/crc32c_test.cc
@@ -0,0 +1,180 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#include "util/crc32c.h"
+#include "test_util/testharness.h"
+#include "util/coding.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace crc32c {
+
+class CRC { };
+
+
+// Tests for 3-way crc32c algorithm. We need these tests because it uses
+// different lookup tables than the original Fast_CRC32
+const unsigned int BUFFER_SIZE = 512 * 1024 * sizeof(uint64_t);
+char buffer[BUFFER_SIZE];
+
+struct ExpectedResult {
+  size_t offset;
+  size_t length;
+  uint32_t crc32c;
+};
+
+ExpectedResult expectedResults[] = {
+    // Zero-byte input
+    { 0, 0, ~0U },
+    // Small aligned inputs to test special cases in SIMD implementations
+    { 8, 1, 1543413366 },
+    { 8, 2, 523493126 },
+    { 8, 3, 1560427360 },
+    { 8, 4, 3422504776 },
+    { 8, 5, 447841138 },
+    { 8, 6, 3910050499 },
+    { 8, 7, 3346241981 },
+    // Small unaligned inputs
+    { 9, 1, 3855826643 },
+    { 10, 2, 560880875 },
+    { 11, 3, 1479707779 },
+    { 12, 4, 2237687071 },
+    { 13, 5, 4063855784 },
+    { 14, 6, 2553454047 },
+    { 15, 7, 1349220140 },
+    // Larger inputs to test leftover chunks at the end of aligned blocks
+    { 8, 8, 627613930 },
+    { 8, 9, 2105929409 },
+    { 8, 10, 2447068514 },
+    { 8, 11, 863807079 },
+    { 8, 12, 292050879 },
+    { 8, 13, 1411837737 },
+    { 8, 14, 2614515001 },
+    { 8, 15, 3579076296 },
+    { 8, 16, 2897079161 },
+    { 8, 17, 675168386 },
+    // // Much larger inputs
+    { 0, BUFFER_SIZE, 2096790750 },
+    { 1, BUFFER_SIZE / 2, 3854797577 },
+
+};
+
+TEST(CRC, StandardResults) {
+
+  // Original Fast_CRC32 tests.
+  // From rfc3720 section B.4.
+  char buf[32];
+
+  memset(buf, 0, sizeof(buf));
+  ASSERT_EQ(0x8a9136aaU, Value(buf, sizeof(buf)));
+
+  memset(buf, 0xff, sizeof(buf));
+  ASSERT_EQ(0x62a8ab43U, Value(buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; i++) {
+    buf[i] = static_cast<char>(i);
+  }
+  ASSERT_EQ(0x46dd794eU, Value(buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; i++) {
+    buf[i] = static_cast<char>(31 - i);
+  }
+  ASSERT_EQ(0x113fdb5cU, Value(buf, sizeof(buf)));
+
+  unsigned char data[48] = {
+    0x01, 0xc0, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x14, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x04, 0x00,
+    0x00, 0x00, 0x00, 0x14,
+    0x00, 0x00, 0x00, 0x18,
+    0x28, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x02, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+  };
+  ASSERT_EQ(0xd9963a56, Value(reinterpret_cast<char*>(data), sizeof(data)));
+
+  // 3-Way Crc32c tests ported from folly.
+  // Test 1: single computation
+  for (auto expected : expectedResults) {
+    uint32_t result = Value(buffer + expected.offset, expected.length);
+    EXPECT_EQ(~expected.crc32c, result);
+  }
+
+  // Test 2: stitching two computations
+  for (auto expected : expectedResults) {
+    size_t partialLength = expected.length / 2;
+    uint32_t partialChecksum = Value(buffer + expected.offset, partialLength);
+    uint32_t result = Extend(partialChecksum,
+        buffer + expected.offset + partialLength,
+        expected.length - partialLength);
+    EXPECT_EQ(~expected.crc32c, result);
+  }
+
+}
+
+TEST(CRC, Values) {
+  ASSERT_NE(Value("a", 1), Value("foo", 3));
+}
+
+TEST(CRC, Extend) {
+  ASSERT_EQ(Value("hello world", 11),
+            Extend(Value("hello ", 6), "world", 5));
+}
+
+TEST(CRC, Mask) {
+  uint32_t crc = Value("foo", 3);
+  ASSERT_NE(crc, Mask(crc));
+  ASSERT_NE(crc, Mask(Mask(crc)));
+  ASSERT_EQ(crc, Unmask(Mask(crc)));
+  ASSERT_EQ(crc, Unmask(Unmask(Mask(Mask(crc)))));
+}
+
+}  // namespace crc32c
+}  // namespace ROCKSDB_NAMESPACE
+
+// copied from folly
+const uint64_t FNV_64_HASH_START = 14695981039346656037ULL;
+inline uint64_t fnv64_buf(const void* buf,
+                          size_t n,
+                          uint64_t hash = FNV_64_HASH_START) {
+  // forcing signed char, since other platforms can use unsigned
+  const signed char* char_buf = reinterpret_cast<const signed char*>(buf);
+
+  for (size_t i = 0; i < n; ++i) {
+    hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) +
+      (hash << 8) + (hash << 40);
+    hash ^= char_buf[i];
+  }
+  return hash;
+}
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  // Populate a buffer with a deterministic pattern
+  // on which to compute checksums
+
+  const uint8_t* src = (uint8_t*)ROCKSDB_NAMESPACE::crc32c::buffer;
+  uint64_t* dst = (uint64_t*)ROCKSDB_NAMESPACE::crc32c::buffer;
+  const uint64_t* end =
+      (const uint64_t*)(ROCKSDB_NAMESPACE::crc32c::buffer +
+                        ROCKSDB_NAMESPACE::crc32c::BUFFER_SIZE);
+  *dst++ = 0;
+  while (dst < end) {
+    ROCKSDB_NAMESPACE::EncodeFixed64(
+        reinterpret_cast<char*>(dst),
+        fnv64_buf((const char*)src, sizeof(uint64_t)));
+    dst++;
+    src += sizeof(uint64_t);
+  }
+
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/defer.h b/src/rocksdb/util/defer.h
new file mode 100644
index 000000000..cb0b42a36
--- /dev/null
+++ b/src/rocksdb/util/defer.h
@@ -0,0 +1,52 @@
+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <functional>
+
+namespace ROCKSDB_NAMESPACE {
+
+// Defers the execution of the provided function until the Defer
+// object goes out of scope.
+//
+// Usage example:
+//
+// Status DeferTest() {
+//   Status s;
+//   Defer defer([&s]() {
+//     if (!s.ok()) {
+//       // do cleanups ...
+//     }
+//   });
+//   // do something ...
+//   if (!s.ok()) return;
+//   // do some other things ...
+//   return s;
+// }
+//
+// The above code ensures that cleanups will always happen on returning.
+//
+// Without the help of Defer, you can
+// 1. every time when !s.ok(), do the cleanup;
+// 2. instead of returning when !s.ok(), continue the work only when s.ok(),
+//    but sometimes, this might lead to nested blocks of "if (s.ok()) {...}".
+//
+// With the help of Defer, you can centralize the cleanup logic inside the
+// lambda passed to Defer, and you can return immediately on failure when necessary.
+class Defer final {
+ public:
+  Defer(std::function<void()>&& fn) : fn_(std::move(fn)) {}
+  ~Defer() { fn_(); }
+
+  // Disallow copy.
+  Defer(const Defer&) = delete;
+  Defer& operator=(const Defer&) = delete;
+
+ private:
+  std::function<void()> fn_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/defer_test.cc b/src/rocksdb/util/defer_test.cc
new file mode 100644
index 000000000..e13b25efb
--- /dev/null
+++ b/src/rocksdb/util/defer_test.cc
@@ -0,0 +1,39 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "port/port.h"
+#include "port/stack_trace.h"
+#include "test_util/testharness.h"
+#include "util/defer.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class DeferTest {};
+
+TEST(DeferTest, BlockScope) {
+  int v = 1;
+  {
+    Defer defer([&v]() { v *= 2; });
+  }
+  ASSERT_EQ(2, v);
+}
+
+TEST(DeferTest, FunctionScope) {
+  int v = 1;
+  auto f = [&v]() {
+    Defer defer([&v]() { v *= 2; });
+    v = 2;
+  };
+  f();
+  ASSERT_EQ(4, v);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/duplicate_detector.h b/src/rocksdb/util/duplicate_detector.h
new file mode 100644
index 000000000..72920ca3c
--- /dev/null
+++ b/src/rocksdb/util/duplicate_detector.h
@@ -0,0 +1,68 @@
+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <cinttypes>
+
+#include "util/set_comparator.h"
+
+namespace ROCKSDB_NAMESPACE {
+// During recovery if the memtable is flushed we cannot rely on its help on
+// duplicate key detection and as key insert will not be attempted. This class
+// will be used as a emulator of memtable to tell if insertion of a key/seq
+// would have resulted in duplication.
+class DuplicateDetector {
+ public:
+  explicit DuplicateDetector(DBImpl* db) : db_(db) {}
+  bool IsDuplicateKeySeq(uint32_t cf, const Slice& key, SequenceNumber seq) {
+    assert(seq >= batch_seq_);
+    if (batch_seq_ != seq) {  // it is a new batch
+      keys_.clear();
+    }
+    batch_seq_ = seq;
+    CFKeys& cf_keys = keys_[cf];
+    if (cf_keys.size() == 0) {  // just inserted
+      InitWithComp(cf);
+    }
+    auto it = cf_keys.insert(key);
+    if (it.second == false) {  // second is false if a element already existed.
+      keys_.clear();
+      InitWithComp(cf);
+      keys_[cf].insert(key);
+      return true;
+    }
+    return false;
+  }
+
+ private:
+  SequenceNumber batch_seq_ = 0;
+  DBImpl* db_;
+  using CFKeys = std::set<Slice, SetComparator>;
+  std::map<uint32_t, CFKeys> keys_;
+  void InitWithComp(const uint32_t cf) {
+    auto h = db_->GetColumnFamilyHandle(cf);
+    if (!h) {
+      // TODO(myabandeh): This is not a concern in MyRocks as drop cf is not
+      // implemented yet. When it does, we should return proper error instead
+      // of throwing exception.
+      ROCKS_LOG_FATAL(
+          db_->immutable_db_options().info_log,
+          "Recovering an entry from the dropped column family %" PRIu32
+          ". WAL must must have been emptied before dropping the column "
+          "family", cf);
+#ifndef ROCKSDB_LITE
+      throw std::runtime_error(
+          "Recovering an entry from a dropped column family. "
+          "WAL must must have been flushed before dropping the column "
+          "family");
+#endif
+      return;
+    }
+    auto cmp = h->GetComparator();
+    keys_[cf] = CFKeys(SetComparator(cmp));
+  }
+};
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/dynamic_bloom.cc b/src/rocksdb/util/dynamic_bloom.cc
new file mode 100644
index 000000000..60d4b2cf2
--- /dev/null
+++ b/src/rocksdb/util/dynamic_bloom.cc
@@ -0,0 +1,70 @@
+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "dynamic_bloom.h"
+
+#include <algorithm>
+
+#include "memory/allocator.h"
+#include "port/port.h"
+#include "rocksdb/slice.h"
+#include "util/hash.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+namespace {
+
+uint32_t roundUpToPow2(uint32_t x) {
+  uint32_t rv = 1;
+  while (rv < x) {
+    rv <<= 1;
+  }
+  return rv;
+}
+}
+
+DynamicBloom::DynamicBloom(Allocator* allocator, uint32_t total_bits,
+                           uint32_t num_probes, size_t huge_page_tlb_size,
+                           Logger* logger)
+    // Round down, except round up with 1
+    : kNumDoubleProbes((num_probes + (num_probes == 1)) / 2) {
+  assert(num_probes % 2 == 0);  // limitation of current implementation
+  assert(num_probes <= 10);     // limitation of current implementation
+  assert(kNumDoubleProbes > 0);
+
+  // Determine how much to round off + align by so that x ^ i (that's xor) is
+  // a valid u64 index if x is a valid u64 index and 0 <= i < kNumDoubleProbes.
+  uint32_t block_bytes = /*bytes/u64*/ 8 *
+                         /*u64s*/ std::max(1U, roundUpToPow2(kNumDoubleProbes));
+  uint32_t block_bits = block_bytes * 8;
+  uint32_t blocks = (total_bits + block_bits - 1) / block_bits;
+  uint32_t sz = blocks * block_bytes;
+  kLen = sz / /*bytes/u64*/ 8;
+  assert(kLen > 0);
+#ifndef NDEBUG
+  for (uint32_t i = 0; i < kNumDoubleProbes; ++i) {
+    // Ensure probes starting at last word are in range
+    assert(((kLen - 1) ^ i) < kLen);
+  }
+#endif
+
+  // Padding to correct for allocation not originally aligned on block_bytes
+  // boundary
+  sz += block_bytes - 1;
+  assert(allocator);
+
+  char* raw = allocator->AllocateAligned(sz, huge_page_tlb_size, logger);
+  memset(raw, 0, sz);
+  auto block_offset = reinterpret_cast<uintptr_t>(raw) % block_bytes;
+  if (block_offset > 0) {
+    // Align on block_bytes boundary
+    raw += block_bytes - block_offset;
+  }
+  static_assert(sizeof(std::atomic<uint64_t>) == sizeof(uint64_t),
+                "Expecting zero-space-overhead atomic");
+  data_ = reinterpret_cast<std::atomic<uint64_t>*>(raw);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/dynamic_bloom.h b/src/rocksdb/util/dynamic_bloom.h
new file mode 100644
index 000000000..d1f22cc75
--- /dev/null
+++ b/src/rocksdb/util/dynamic_bloom.h
@@ -0,0 +1,214 @@
+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <array>
+#include <string>
+#include "port/port.h"
+#include "rocksdb/slice.h"
+#include "table/multiget_context.h"
+#include "util/hash.h"
+
+#include <atomic>
+#include <memory>
+
+namespace ROCKSDB_NAMESPACE {
+
+class Slice;
+class Allocator;
+class Logger;
+
+// A Bloom filter intended only to be used in memory, never serialized in a way
+// that could lead to schema incompatibility. Supports opt-in lock-free
+// concurrent access.
+//
+// This implementation is also intended for applications generally preferring
+// speed vs. maximum accuracy: roughly 0.9x BF op latency for 1.1x FP rate.
+// For 1% FP rate, that means that the latency of a look-up triggered by an FP
+// should be less than roughly 100x the cost of a Bloom filter op.
+//
+// For simplicity and performance, the current implementation requires
+// num_probes to be a multiple of two and <= 10.
+//
+class DynamicBloom {
+ public:
+  // allocator: pass allocator to bloom filter, hence trace the usage of memory
+  // total_bits: fixed total bits for the bloom
+  // num_probes: number of hash probes for a single key
+  // hash_func:  customized hash function
+  // huge_page_tlb_size:  if >0, try to allocate bloom bytes from huge page TLB
+  //                      within this page size. Need to reserve huge pages for
+  //                      it to be allocated, like:
+  //                         sysctl -w vm.nr_hugepages=20
+  //                     See linux doc Documentation/vm/hugetlbpage.txt
+  explicit DynamicBloom(Allocator* allocator, uint32_t total_bits,
+                        uint32_t num_probes = 6, size_t huge_page_tlb_size = 0,
+                        Logger* logger = nullptr);
+
+  ~DynamicBloom() {}
+
+  // Assuming single threaded access to this function.
+  void Add(const Slice& key);
+
+  // Like Add, but may be called concurrent with other functions.
+  void AddConcurrently(const Slice& key);
+
+  // Assuming single threaded access to this function.
+  void AddHash(uint32_t hash);
+
+  // Like AddHash, but may be called concurrent with other functions.
+  void AddHashConcurrently(uint32_t hash);
+
+  // Multithreaded access to this function is OK
+  bool MayContain(const Slice& key) const;
+
+  void MayContain(int num_keys, Slice** keys, bool* may_match) const;
+
+  // Multithreaded access to this function is OK
+  bool MayContainHash(uint32_t hash) const;
+
+  void Prefetch(uint32_t h);
+
+ private:
+  // Length of the structure, in 64-bit words. For this structure, "word"
+  // will always refer to 64-bit words.
+  uint32_t kLen;
+  // We make the k probes in pairs, two for each 64-bit read/write. Thus,
+  // this stores k/2, the number of words to double-probe.
+  const uint32_t kNumDoubleProbes;
+
+  std::atomic<uint64_t>* data_;
+
+  // or_func(ptr, mask) should effect *ptr |= mask with the appropriate
+  // concurrency safety, working with bytes.
+  template <typename OrFunc>
+  void AddHash(uint32_t hash, const OrFunc& or_func);
+
+  bool DoubleProbe(uint32_t h32, size_t a) const;
+};
+
+inline void DynamicBloom::Add(const Slice& key) { AddHash(BloomHash(key)); }
+
+inline void DynamicBloom::AddConcurrently(const Slice& key) {
+  AddHashConcurrently(BloomHash(key));
+}
+
+inline void DynamicBloom::AddHash(uint32_t hash) {
+  AddHash(hash, [](std::atomic<uint64_t>* ptr, uint64_t mask) {
+    ptr->store(ptr->load(std::memory_order_relaxed) | mask,
+               std::memory_order_relaxed);
+  });
+}
+
+inline void DynamicBloom::AddHashConcurrently(uint32_t hash) {
+  AddHash(hash, [](std::atomic<uint64_t>* ptr, uint64_t mask) {
+    // Happens-before between AddHash and MaybeContains is handled by
+    // access to versions_->LastSequence(), so all we have to do here is
+    // avoid races (so we don't give the compiler a license to mess up
+    // our code) and not lose bits.  std::memory_order_relaxed is enough
+    // for that.
+    if ((mask & ptr->load(std::memory_order_relaxed)) != mask) {
+      ptr->fetch_or(mask, std::memory_order_relaxed);
+    }
+  });
+}
+
+inline bool DynamicBloom::MayContain(const Slice& key) const {
+  return (MayContainHash(BloomHash(key)));
+}
+
+inline void DynamicBloom::MayContain(int num_keys, Slice** keys,
+                                     bool* may_match) const {
+  std::array<uint32_t, MultiGetContext::MAX_BATCH_SIZE> hashes;
+  std::array<size_t, MultiGetContext::MAX_BATCH_SIZE> byte_offsets;
+  for (int i = 0; i < num_keys; ++i) {
+    hashes[i] = BloomHash(*keys[i]);
+    size_t a = fastrange32(kLen, hashes[i]);
+    PREFETCH(data_ + a, 0, 3);
+    byte_offsets[i] = a;
+  }
+
+  for (int i = 0; i < num_keys; i++) {
+    may_match[i] = DoubleProbe(hashes[i], byte_offsets[i]);
+  }
+}
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+// local variable is initialized but not referenced
+#pragma warning(disable : 4189)
+#endif
+inline void DynamicBloom::Prefetch(uint32_t h32) {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+}
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+// Speed hacks in this implementation:
+// * Uses fastrange instead of %
+// * Minimum logic to determine first (and all) probed memory addresses.
+//   (Uses constant bit-xor offsets from the starting probe address.)
+// * (Major) Two probes per 64-bit memory fetch/write.
+//   Code simplification / optimization: only allow even number of probes.
+// * Very fast and effective (murmur-like) hash expansion/re-mixing. (At
+// least on recent CPUs, integer multiplication is very cheap. Each 64-bit
+// remix provides five pairs of bit addresses within a uint64_t.)
+//   Code simplification / optimization: only allow up to 10 probes, from a
+//   single 64-bit remix.
+//
+// The FP rate penalty for this implementation, vs. standard Bloom filter, is
+// roughly 1.12x on top of the 1.15x penalty for a 512-bit cache-local Bloom.
+// This implementation does not explicitly use the cache line size, but is
+// effectively cache-local (up to 16 probes) because of the bit-xor offsetting.
+//
+// NB: could easily be upgraded to support a 64-bit hash and
+// total_bits > 2^32 (512MB). (The latter is a bad idea without the former,
+// because of false positives.)
+
+inline bool DynamicBloom::MayContainHash(uint32_t h32) const {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+  return DoubleProbe(h32, a);
+}
+
+inline bool DynamicBloom::DoubleProbe(uint32_t h32, size_t byte_offset) const {
+  // Expand/remix with 64-bit golden ratio
+  uint64_t h = 0x9e3779b97f4a7c13ULL * h32;
+  for (unsigned i = 0;; ++i) {
+    // Two bit probes per uint64_t probe
+    uint64_t mask =
+        ((uint64_t)1 << (h & 63)) | ((uint64_t)1 << ((h >> 6) & 63));
+    uint64_t val = data_[byte_offset ^ i].load(std::memory_order_relaxed);
+    if (i + 1 >= kNumDoubleProbes) {
+      return (val & mask) == mask;
+    } else if ((val & mask) != mask) {
+      return false;
+    }
+    h = (h >> 12) | (h << 52);
+  }
+}
+
+template <typename OrFunc>
+inline void DynamicBloom::AddHash(uint32_t h32, const OrFunc& or_func) {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+  // Expand/remix with 64-bit golden ratio
+  uint64_t h = 0x9e3779b97f4a7c13ULL * h32;
+  for (unsigned i = 0;; ++i) {
+    // Two bit probes per uint64_t probe
+    uint64_t mask =
+        ((uint64_t)1 << (h & 63)) | ((uint64_t)1 << ((h >> 6) & 63));
+    or_func(&data_[a ^ i], mask);
+    if (i + 1 >= kNumDoubleProbes) {
+      return;
+    }
+    h = (h >> 12) | (h << 52);
+  }
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/dynamic_bloom_test.cc b/src/rocksdb/util/dynamic_bloom_test.cc
new file mode 100644
index 000000000..47d04a36c
--- /dev/null
+++ b/src/rocksdb/util/dynamic_bloom_test.cc
@@ -0,0 +1,324 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#ifndef GFLAGS
+#include <cstdio>
+int main() {
+  fprintf(stderr, "Please install gflags to run this test... Skipping...\n");
+  return 0;
+}
+#else
+
+#include <algorithm>
+#include <atomic>
+#include <cinttypes>
+#include <functional>
+#include <memory>
+#include <thread>
+#include <vector>
+
+#include "dynamic_bloom.h"
+#include "logging/logging.h"
+#include "memory/arena.h"
+#include "port/port.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/gflags_compat.h"
+#include "util/stop_watch.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+
+DEFINE_int32(bits_per_key, 10, "");
+DEFINE_int32(num_probes, 6, "");
+DEFINE_bool(enable_perf, false, "");
+
+namespace ROCKSDB_NAMESPACE {
+
+struct KeyMaker {
+  uint64_t a;
+  uint64_t b;
+
+  // Sequential, within a hash function block
+  inline Slice Seq(uint64_t i) {
+    a = i;
+    return Slice(reinterpret_cast<char *>(&a), sizeof(a));
+  }
+  // Not quite sequential, varies across hash function blocks
+  inline Slice Nonseq(uint64_t i) {
+    a = i;
+    b = i * 123;
+    return Slice(reinterpret_cast<char *>(this), sizeof(*this));
+  }
+  inline Slice Key(uint64_t i, bool nonseq) {
+    return nonseq ? Nonseq(i) : Seq(i);
+  }
+};
+
+class DynamicBloomTest : public testing::Test {};
+
+TEST_F(DynamicBloomTest, EmptyFilter) {
+  Arena arena;
+  DynamicBloom bloom1(&arena, 100, 2);
+  ASSERT_TRUE(!bloom1.MayContain("hello"));
+  ASSERT_TRUE(!bloom1.MayContain("world"));
+
+  DynamicBloom bloom2(&arena, CACHE_LINE_SIZE * 8 * 2 - 1, 2);
+  ASSERT_TRUE(!bloom2.MayContain("hello"));
+  ASSERT_TRUE(!bloom2.MayContain("world"));
+}
+
+TEST_F(DynamicBloomTest, Small) {
+  Arena arena;
+  DynamicBloom bloom1(&arena, 100, 2);
+  bloom1.Add("hello");
+  bloom1.Add("world");
+  ASSERT_TRUE(bloom1.MayContain("hello"));
+  ASSERT_TRUE(bloom1.MayContain("world"));
+  ASSERT_TRUE(!bloom1.MayContain("x"));
+  ASSERT_TRUE(!bloom1.MayContain("foo"));
+
+  DynamicBloom bloom2(&arena, CACHE_LINE_SIZE * 8 * 2 - 1, 2);
+  bloom2.Add("hello");
+  bloom2.Add("world");
+  ASSERT_TRUE(bloom2.MayContain("hello"));
+  ASSERT_TRUE(bloom2.MayContain("world"));
+  ASSERT_TRUE(!bloom2.MayContain("x"));
+  ASSERT_TRUE(!bloom2.MayContain("foo"));
+}
+
+TEST_F(DynamicBloomTest, SmallConcurrentAdd) {
+  Arena arena;
+  DynamicBloom bloom1(&arena, 100, 2);
+  bloom1.AddConcurrently("hello");
+  bloom1.AddConcurrently("world");
+  ASSERT_TRUE(bloom1.MayContain("hello"));
+  ASSERT_TRUE(bloom1.MayContain("world"));
+  ASSERT_TRUE(!bloom1.MayContain("x"));
+  ASSERT_TRUE(!bloom1.MayContain("foo"));
+
+  DynamicBloom bloom2(&arena, CACHE_LINE_SIZE * 8 * 2 - 1, 2);
+  bloom2.AddConcurrently("hello");
+  bloom2.AddConcurrently("world");
+  ASSERT_TRUE(bloom2.MayContain("hello"));
+  ASSERT_TRUE(bloom2.MayContain("world"));
+  ASSERT_TRUE(!bloom2.MayContain("x"));
+  ASSERT_TRUE(!bloom2.MayContain("foo"));
+}
+
+static uint32_t NextNum(uint32_t num) {
+  if (num < 10) {
+    num += 1;
+  } else if (num < 100) {
+    num += 10;
+  } else if (num < 1000) {
+    num += 100;
+  } else {
+    num = num * 26 / 10;
+  }
+  return num;
+}
+
+TEST_F(DynamicBloomTest, VaryingLengths) {
+  KeyMaker km;
+
+  // Count number of filters that significantly exceed the false positive rate
+  int mediocre_filters = 0;
+  int good_filters = 0;
+  uint32_t num_probes = static_cast<uint32_t>(FLAGS_num_probes);
+
+  fprintf(stderr, "bits_per_key: %d  num_probes: %d\n", FLAGS_bits_per_key,
+          num_probes);
+
+  // NB: FP rate impact of 32-bit hash is noticeable starting around 10M keys.
+  // But that effect is hidden if using sequential keys (unique hashes).
+  for (bool nonseq : {false, true}) {
+    const uint32_t max_num = FLAGS_enable_perf ? 40000000 : 400000;
+    for (uint32_t num = 1; num <= max_num; num = NextNum(num)) {
+      uint32_t bloom_bits = 0;
+      Arena arena;
+      bloom_bits = num * FLAGS_bits_per_key;
+      DynamicBloom bloom(&arena, bloom_bits, num_probes);
+      for (uint64_t i = 0; i < num; i++) {
+        bloom.Add(km.Key(i, nonseq));
+        ASSERT_TRUE(bloom.MayContain(km.Key(i, nonseq)));
+      }
+
+      // All added keys must match
+      for (uint64_t i = 0; i < num; i++) {
+        ASSERT_TRUE(bloom.MayContain(km.Key(i, nonseq)));
+      }
+
+      // Check false positive rate
+      int result = 0;
+      for (uint64_t i = 0; i < 30000; i++) {
+        if (bloom.MayContain(km.Key(i + 1000000000, nonseq))) {
+          result++;
+        }
+      }
+      double rate = result / 30000.0;
+
+      fprintf(stderr,
+              "False positives (%s keys): "
+              "%5.2f%% @ num = %6u, bloom_bits = %6u\n",
+              nonseq ? "nonseq" : "seq", rate * 100.0, num, bloom_bits);
+
+      if (rate > 0.0125)
+        mediocre_filters++;  // Allowed, but not too often
+      else
+        good_filters++;
+    }
+  }
+
+  fprintf(stderr, "Filters: %d good, %d mediocre\n", good_filters,
+          mediocre_filters);
+  ASSERT_LE(mediocre_filters, good_filters / 25);
+}
+
+TEST_F(DynamicBloomTest, perf) {
+  KeyMaker km;
+  StopWatchNano timer(Env::Default());
+  uint32_t num_probes = static_cast<uint32_t>(FLAGS_num_probes);
+
+  if (!FLAGS_enable_perf) {
+    return;
+  }
+
+  for (uint32_t m = 1; m <= 8; ++m) {
+    Arena arena;
+    const uint32_t num_keys = m * 8 * 1024 * 1024;
+    fprintf(stderr, "testing %" PRIu32 "M keys\n", m * 8);
+
+    DynamicBloom std_bloom(&arena, num_keys * 10, num_probes);
+
+    timer.Start();
+    for (uint64_t i = 1; i <= num_keys; ++i) {
+      std_bloom.Add(km.Seq(i));
+    }
+
+    uint64_t elapsed = timer.ElapsedNanos();
+    fprintf(stderr, "dynamic bloom, avg add latency %3g\n",
+            static_cast<double>(elapsed) / num_keys);
+
+    uint32_t count = 0;
+    timer.Start();
+    for (uint64_t i = 1; i <= num_keys; ++i) {
+      if (std_bloom.MayContain(km.Seq(i))) {
+        ++count;
+      }
+    }
+    ASSERT_EQ(count, num_keys);
+    elapsed = timer.ElapsedNanos();
+    assert(count > 0);
+    fprintf(stderr, "dynamic bloom, avg query latency %3g\n",
+            static_cast<double>(elapsed) / count);
+  }
+}
+
+TEST_F(DynamicBloomTest, concurrent_with_perf) {
+  uint32_t num_probes = static_cast<uint32_t>(FLAGS_num_probes);
+
+  uint32_t m_limit = FLAGS_enable_perf ? 8 : 1;
+
+  uint32_t num_threads = 4;
+  std::vector<port::Thread> threads;
+
+  // NB: Uses sequential keys for speed, but that hides the FP rate
+  // impact of 32-bit hash, which is noticeable starting around 10M keys
+  // when they vary across hashing blocks.
+  for (uint32_t m = 1; m <= m_limit; ++m) {
+    Arena arena;
+    const uint32_t num_keys = m * 8 * 1024 * 1024;
+    fprintf(stderr, "testing %" PRIu32 "M keys\n", m * 8);
+
+    DynamicBloom std_bloom(&arena, num_keys * 10, num_probes);
+
+    std::atomic<uint64_t> elapsed(0);
+
+    std::function<void(size_t)> adder([&](size_t t) {
+      KeyMaker km;
+      StopWatchNano timer(Env::Default());
+      timer.Start();
+      for (uint64_t i = 1 + t; i <= num_keys; i += num_threads) {
+        std_bloom.AddConcurrently(km.Seq(i));
+      }
+      elapsed += timer.ElapsedNanos();
+    });
+    for (size_t t = 0; t < num_threads; ++t) {
+      threads.emplace_back(adder, t);
+    }
+    while (threads.size() > 0) {
+      threads.back().join();
+      threads.pop_back();
+    }
+
+    fprintf(stderr,
+            "dynamic bloom, avg parallel add latency %3g"
+            " nanos/key\n",
+            static_cast<double>(elapsed) / num_threads / num_keys);
+
+    elapsed = 0;
+    std::function<void(size_t)> hitter([&](size_t t) {
+      KeyMaker km;
+      StopWatchNano timer(Env::Default());
+      timer.Start();
+      for (uint64_t i = 1 + t; i <= num_keys; i += num_threads) {
+        bool f = std_bloom.MayContain(km.Seq(i));
+        ASSERT_TRUE(f);
+      }
+      elapsed += timer.ElapsedNanos();
+    });
+    for (size_t t = 0; t < num_threads; ++t) {
+      threads.emplace_back(hitter, t);
+    }
+    while (threads.size() > 0) {
+      threads.back().join();
+      threads.pop_back();
+    }
+
+    fprintf(stderr,
+            "dynamic bloom, avg parallel hit latency %3g"
+            " nanos/key\n",
+            static_cast<double>(elapsed) / num_threads / num_keys);
+
+    elapsed = 0;
+    std::atomic<uint32_t> false_positives(0);
+    std::function<void(size_t)> misser([&](size_t t) {
+      KeyMaker km;
+      StopWatchNano timer(Env::Default());
+      timer.Start();
+      for (uint64_t i = num_keys + 1 + t; i <= 2 * num_keys; i += num_threads) {
+        bool f = std_bloom.MayContain(km.Seq(i));
+        if (f) {
+          ++false_positives;
+        }
+      }
+      elapsed += timer.ElapsedNanos();
+    });
+    for (size_t t = 0; t < num_threads; ++t) {
+      threads.emplace_back(misser, t);
+    }
+    while (threads.size() > 0) {
+      threads.back().join();
+      threads.pop_back();
+    }
+
+    fprintf(stderr,
+            "dynamic bloom, avg parallel miss latency %3g"
+            " nanos/key, %f%% false positive rate\n",
+            static_cast<double>(elapsed) / num_threads / num_keys,
+            false_positives.load() * 100.0 / num_keys);
+  }
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  return RUN_ALL_TESTS();
+}
+
+#endif  // GFLAGS
diff --git a/src/rocksdb/util/file_checksum_helper.cc b/src/rocksdb/util/file_checksum_helper.cc
new file mode 100644
index 000000000..51dcf6a82
--- /dev/null
+++ b/src/rocksdb/util/file_checksum_helper.cc
@@ -0,0 +1,85 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+//  Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+//  Use of this source code is governed by a BSD-style license that can be
+//  found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/file_checksum_helper.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+void FileChecksumListImpl::reset() { checksum_map_.clear(); }
+
+size_t FileChecksumListImpl::size() const { return checksum_map_.size(); }
+
+Status FileChecksumListImpl::GetAllFileChecksums(
+    std::vector<uint64_t>* file_numbers, std::vector<std::string>* checksums,
+    std::vector<std::string>* checksum_func_names) {
+  if (file_numbers == nullptr || checksums == nullptr ||
+      checksum_func_names == nullptr) {
+    return Status::InvalidArgument("Pointer has not been initiated");
+  }
+
+  for (auto i : checksum_map_) {
+    file_numbers->push_back(i.first);
+    checksums->push_back(i.second.first);
+    checksum_func_names->push_back(i.second.second);
+  }
+  return Status::OK();
+}
+
+Status FileChecksumListImpl::SearchOneFileChecksum(
+    uint64_t file_number, std::string* checksum,
+    std::string* checksum_func_name) {
+  if (checksum == nullptr || checksum_func_name == nullptr) {
+    return Status::InvalidArgument("Pointer has not been initiated");
+  }
+
+  auto it = checksum_map_.find(file_number);
+  if (it == checksum_map_.end()) {
+    return Status::NotFound();
+  } else {
+    *checksum = it->second.first;
+    *checksum_func_name = it->second.second;
+  }
+  return Status::OK();
+}
+
+Status FileChecksumListImpl::InsertOneFileChecksum(
+    uint64_t file_number, const std::string& checksum,
+    const std::string& checksum_func_name) {
+  auto it = checksum_map_.find(file_number);
+  if (it == checksum_map_.end()) {
+    checksum_map_.insert(std::make_pair(
+        file_number, std::make_pair(checksum, checksum_func_name)));
+  } else {
+    it->second.first = checksum;
+    it->second.second = checksum_func_name;
+  }
+  return Status::OK();
+}
+
+Status FileChecksumListImpl::RemoveOneFileChecksum(uint64_t file_number) {
+  auto it = checksum_map_.find(file_number);
+  if (it == checksum_map_.end()) {
+    return Status::NotFound();
+  } else {
+    checksum_map_.erase(it);
+  }
+  return Status::OK();
+}
+
+FileChecksumList* NewFileChecksumList() {
+  FileChecksumListImpl* checksum_list = new FileChecksumListImpl();
+  return checksum_list;
+}
+
+FileChecksumFunc* CreateFileChecksumFuncCrc32c() {
+  FileChecksumFunc* file_checksum_crc32c = new FileChecksumFuncCrc32c();
+  return file_checksum_crc32c;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/file_checksum_helper.h b/src/rocksdb/util/file_checksum_helper.h
new file mode 100644
index 000000000..7ad9ea732
--- /dev/null
+++ b/src/rocksdb/util/file_checksum_helper.h
@@ -0,0 +1,117 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+#include <cassert>
+#include <unordered_map>
+#include "port/port.h"
+#include "rocksdb/file_checksum.h"
+#include "rocksdb/status.h"
+#include "util/crc32c.h"
+#include "util/string_util.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// This is the class to generate the file checksum based on Crc32. It
+// will be used as the default checksum method for SST file checksum
+class FileChecksumFuncCrc32c : public FileChecksumFunc {
+ public:
+  std::string Extend(const std::string& init_checksum, const char* data,
+                     size_t n) override {
+    assert(data != nullptr);
+    uint32_t checksum_value = StringToUint32(init_checksum);
+    return Uint32ToString(crc32c::Extend(checksum_value, data, n));
+  }
+
+  std::string Value(const char* data, size_t n) override {
+    assert(data != nullptr);
+    return Uint32ToString(crc32c::Value(data, n));
+  }
+
+  std::string ProcessChecksum(const std::string& checksum) override {
+    uint32_t checksum_value = StringToUint32(checksum);
+    return Uint32ToString(crc32c::Mask(checksum_value));
+  }
+
+  const char* Name() const override { return "FileChecksumCrc32c"; }
+
+  // Convert a uint32_t type data into a 4 bytes string.
+  static std::string Uint32ToString(uint32_t v) {
+    std::string s;
+    if (port::kLittleEndian) {
+      s.append(reinterpret_cast<char*>(&v), sizeof(v));
+    } else {
+      char buf[sizeof(v)];
+      buf[0] = v & 0xff;
+      buf[1] = (v >> 8) & 0xff;
+      buf[2] = (v >> 16) & 0xff;
+      buf[3] = (v >> 24) & 0xff;
+      s.append(buf, sizeof(v));
+    }
+    size_t i = 0, j = s.size() - 1;
+    while (i < j) {
+      char tmp = s[i];
+      s[i] = s[j];
+      s[j] = tmp;
+      ++i;
+      --j;
+    }
+    return s;
+  }
+
+  // Convert a 4 bytes size string into a uint32_t type data.
+  static uint32_t StringToUint32(std::string s) {
+    assert(s.size() == sizeof(uint32_t));
+    size_t i = 0, j = s.size() - 1;
+    while (i < j) {
+      char tmp = s[i];
+      s[i] = s[j];
+      s[j] = tmp;
+      ++i;
+      --j;
+    }
+    uint32_t v = 0;
+    if (port::kLittleEndian) {
+      memcpy(&v, s.c_str(), sizeof(uint32_t));
+    } else {
+      const char* buf = s.c_str();
+      v |= static_cast<uint32_t>(buf[0]);
+      v |= (static_cast<uint32_t>(buf[1]) << 8);
+      v |= (static_cast<uint32_t>(buf[2]) << 16);
+      v |= (static_cast<uint32_t>(buf[3]) << 24);
+    }
+    return v;
+  }
+};
+
+// The default implementaion of FileChecksumList
+class FileChecksumListImpl : public FileChecksumList {
+ public:
+  FileChecksumListImpl() {}
+  void reset() override;
+
+  size_t size() const override;
+
+  Status GetAllFileChecksums(
+      std::vector<uint64_t>* file_numbers, std::vector<std::string>* checksums,
+      std::vector<std::string>* checksum_func_names) override;
+
+  Status SearchOneFileChecksum(uint64_t file_number, std::string* checksum,
+                               std::string* checksum_func_name) override;
+
+  Status InsertOneFileChecksum(uint64_t file_number,
+                               const std::string& checksum,
+                               const std::string& checksum_func_name) override;
+
+  Status RemoveOneFileChecksum(uint64_t file_number) override;
+
+ private:
+  // Key is the file number, the first portion of the value is checksum, the
+  // second portion of the value is checksum function name.
+  std::unordered_map<uint64_t, std::pair<std::string, std::string>>
+      checksum_map_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/file_reader_writer_test.cc b/src/rocksdb/util/file_reader_writer_test.cc
new file mode 100644
index 000000000..f37bd5931
--- /dev/null
+++ b/src/rocksdb/util/file_reader_writer_test.cc
@@ -0,0 +1,444 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#include <algorithm>
+#include <vector>
+#include "env/composite_env_wrapper.h"
+#include "file/random_access_file_reader.h"
+#include "file/readahead_raf.h"
+#include "file/sequence_file_reader.h"
+#include "file/writable_file_writer.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class WritableFileWriterTest : public testing::Test {};
+
+const uint32_t kMb = 1 << 20;
+
+TEST_F(WritableFileWriterTest, RangeSync) {
+  class FakeWF : public WritableFile {
+   public:
+    explicit FakeWF() : size_(0), last_synced_(0) {}
+    ~FakeWF() override {}
+
+    Status Append(const Slice& data) override {
+      size_ += data.size();
+      return Status::OK();
+    }
+    Status Truncate(uint64_t /*size*/) override { return Status::OK(); }
+    Status Close() override {
+      EXPECT_GE(size_, last_synced_ + kMb);
+      EXPECT_LT(size_, last_synced_ + 2 * kMb);
+      // Make sure random writes generated enough writes.
+      EXPECT_GT(size_, 10 * kMb);
+      return Status::OK();
+    }
+    Status Flush() override { return Status::OK(); }
+    Status Sync() override { return Status::OK(); }
+    Status Fsync() override { return Status::OK(); }
+    void SetIOPriority(Env::IOPriority /*pri*/) override {}
+    uint64_t GetFileSize() override { return size_; }
+    void GetPreallocationStatus(size_t* /*block_size*/,
+                                size_t* /*last_allocated_block*/) override {}
+    size_t GetUniqueId(char* /*id*/, size_t /*max_size*/) const override {
+      return 0;
+    }
+    Status InvalidateCache(size_t /*offset*/, size_t /*length*/) override {
+      return Status::OK();
+    }
+
+   protected:
+    Status Allocate(uint64_t /*offset*/, uint64_t /*len*/) override {
+      return Status::OK();
+    }
+    Status RangeSync(uint64_t offset, uint64_t nbytes) override {
+      EXPECT_EQ(offset % 4096, 0u);
+      EXPECT_EQ(nbytes % 4096, 0u);
+
+      EXPECT_EQ(offset, last_synced_);
+      last_synced_ = offset + nbytes;
+      EXPECT_GE(size_, last_synced_ + kMb);
+      if (size_ > 2 * kMb) {
+        EXPECT_LT(size_, last_synced_ + 2 * kMb);
+      }
+      return Status::OK();
+    }
+
+    uint64_t size_;
+    uint64_t last_synced_;
+  };
+
+  EnvOptions env_options;
+  env_options.bytes_per_sync = kMb;
+  std::unique_ptr<FakeWF> wf(new FakeWF);
+  std::unique_ptr<WritableFileWriter> writer(
+      new WritableFileWriter(NewLegacyWritableFileWrapper(std::move(wf)),
+                             "" /* don't care */, env_options));
+  Random r(301);
+  std::unique_ptr<char[]> large_buf(new char[10 * kMb]);
+  for (int i = 0; i < 1000; i++) {
+    int skew_limit = (i < 700) ? 10 : 15;
+    uint32_t num = r.Skewed(skew_limit) * 100 + r.Uniform(100);
+    writer->Append(Slice(large_buf.get(), num));
+
+    // Flush in a chance of 1/10.
+    if (r.Uniform(10) == 0) {
+      writer->Flush();
+    }
+  }
+  writer->Close();
+}
+
+TEST_F(WritableFileWriterTest, IncrementalBuffer) {
+  class FakeWF : public WritableFile {
+   public:
+    explicit FakeWF(std::string* _file_data, bool _use_direct_io,
+                    bool _no_flush)
+        : file_data_(_file_data),
+          use_direct_io_(_use_direct_io),
+          no_flush_(_no_flush) {}
+    ~FakeWF() override {}
+
+    Status Append(const Slice& data) override {
+      file_data_->append(data.data(), data.size());
+      size_ += data.size();
+      return Status::OK();
+    }
+    Status PositionedAppend(const Slice& data, uint64_t pos) override {
+      EXPECT_TRUE(pos % 512 == 0);
+      EXPECT_TRUE(data.size() % 512 == 0);
+      file_data_->resize(pos);
+      file_data_->append(data.data(), data.size());
+      size_ += data.size();
+      return Status::OK();
+    }
+
+    Status Truncate(uint64_t size) override {
+      file_data_->resize(size);
+      return Status::OK();
+    }
+    Status Close() override { return Status::OK(); }
+    Status Flush() override { return Status::OK(); }
+    Status Sync() override { return Status::OK(); }
+    Status Fsync() override { return Status::OK(); }
+    void SetIOPriority(Env::IOPriority /*pri*/) override {}
+    uint64_t GetFileSize() override { return size_; }
+    void GetPreallocationStatus(size_t* /*block_size*/,
+                                size_t* /*last_allocated_block*/) override {}
+    size_t GetUniqueId(char* /*id*/, size_t /*max_size*/) const override {
+      return 0;
+    }
+    Status InvalidateCache(size_t /*offset*/, size_t /*length*/) override {
+      return Status::OK();
+    }
+    bool use_direct_io() const override { return use_direct_io_; }
+
+    std::string* file_data_;
+    bool use_direct_io_;
+    bool no_flush_;
+    size_t size_ = 0;
+  };
+
+  Random r(301);
+  const int kNumAttempts = 50;
+  for (int attempt = 0; attempt < kNumAttempts; attempt++) {
+    bool no_flush = (attempt % 3 == 0);
+    EnvOptions env_options;
+    env_options.writable_file_max_buffer_size =
+        (attempt < kNumAttempts / 2) ? 512 * 1024 : 700 * 1024;
+    std::string actual;
+    std::unique_ptr<FakeWF> wf(new FakeWF(&actual,
+#ifndef ROCKSDB_LITE
+                                          attempt % 2 == 1,
+#else
+                                          false,
+#endif
+                                          no_flush));
+    std::unique_ptr<WritableFileWriter> writer(
+        new WritableFileWriter(NewLegacyWritableFileWrapper(std::move(wf)),
+                               "" /* don't care */, env_options));
+
+    std::string target;
+    for (int i = 0; i < 20; i++) {
+      uint32_t num = r.Skewed(16) * 100 + r.Uniform(100);
+      std::string random_string;
+      test::RandomString(&r, num, &random_string);
+      writer->Append(Slice(random_string.c_str(), num));
+      target.append(random_string.c_str(), num);
+
+      // In some attempts, flush in a chance of 1/10.
+      if (!no_flush && r.Uniform(10) == 0) {
+        writer->Flush();
+      }
+    }
+    writer->Flush();
+    writer->Close();
+    ASSERT_EQ(target.size(), actual.size());
+    ASSERT_EQ(target, actual);
+  }
+}
+
+#ifndef ROCKSDB_LITE
+TEST_F(WritableFileWriterTest, AppendStatusReturn) {
+  class FakeWF : public WritableFile {
+   public:
+    explicit FakeWF() : use_direct_io_(false), io_error_(false) {}
+
+    bool use_direct_io() const override { return use_direct_io_; }
+    Status Append(const Slice& /*data*/) override {
+      if (io_error_) {
+        return Status::IOError("Fake IO error");
+      }
+      return Status::OK();
+    }
+    Status PositionedAppend(const Slice& /*data*/, uint64_t) override {
+      if (io_error_) {
+        return Status::IOError("Fake IO error");
+      }
+      return Status::OK();
+    }
+    Status Close() override { return Status::OK(); }
+    Status Flush() override { return Status::OK(); }
+    Status Sync() override { return Status::OK(); }
+    void Setuse_direct_io(bool val) { use_direct_io_ = val; }
+    void SetIOError(bool val) { io_error_ = val; }
+
+   protected:
+    bool use_direct_io_;
+    bool io_error_;
+  };
+  std::unique_ptr<FakeWF> wf(new FakeWF());
+  wf->Setuse_direct_io(true);
+  std::unique_ptr<WritableFileWriter> writer(
+      new WritableFileWriter(NewLegacyWritableFileWrapper(std::move(wf)),
+                             "" /* don't care */, EnvOptions()));
+
+  ASSERT_OK(writer->Append(std::string(2 * kMb, 'a')));
+
+  // Next call to WritableFile::Append() should fail
+  LegacyWritableFileWrapper* file =
+      static_cast<LegacyWritableFileWrapper*>(writer->writable_file());
+  static_cast<FakeWF*>(file->target())->SetIOError(true);
+  ASSERT_NOK(writer->Append(std::string(2 * kMb, 'b')));
+}
+#endif
+
+class ReadaheadRandomAccessFileTest
+    : public testing::Test,
+      public testing::WithParamInterface<size_t> {
+ public:
+  static std::vector<size_t> GetReadaheadSizeList() {
+    return {1lu << 12, 1lu << 16};
+  }
+  void SetUp() override {
+    readahead_size_ = GetParam();
+    scratch_.reset(new char[2 * readahead_size_]);
+    ResetSourceStr();
+  }
+  ReadaheadRandomAccessFileTest() : control_contents_() {}
+  std::string Read(uint64_t offset, size_t n) {
+    Slice result;
+    test_read_holder_->Read(offset, n, &result, scratch_.get());
+    return std::string(result.data(), result.size());
+  }
+  void ResetSourceStr(const std::string& str = "") {
+    auto write_holder =
+        std::unique_ptr<WritableFileWriter>(test::GetWritableFileWriter(
+            new test::StringSink(&control_contents_), "" /* don't care */));
+    write_holder->Append(Slice(str));
+    write_holder->Flush();
+    auto read_holder = std::unique_ptr<RandomAccessFile>(
+        new test::StringSource(control_contents_));
+    test_read_holder_ =
+        NewReadaheadRandomAccessFile(std::move(read_holder), readahead_size_);
+  }
+  size_t GetReadaheadSize() const { return readahead_size_; }
+
+ private:
+  size_t readahead_size_;
+  Slice control_contents_;
+  std::unique_ptr<RandomAccessFile> test_read_holder_;
+  std::unique_ptr<char[]> scratch_;
+};
+
+TEST_P(ReadaheadRandomAccessFileTest, EmptySourceStr) {
+  ASSERT_EQ("", Read(0, 1));
+  ASSERT_EQ("", Read(0, 0));
+  ASSERT_EQ("", Read(13, 13));
+}
+
+TEST_P(ReadaheadRandomAccessFileTest, SourceStrLenLessThanReadaheadSize) {
+  std::string str = "abcdefghijklmnopqrs";
+  ResetSourceStr(str);
+  ASSERT_EQ(str.substr(3, 4), Read(3, 4));
+  ASSERT_EQ(str.substr(0, 3), Read(0, 3));
+  ASSERT_EQ(str, Read(0, str.size()));
+  ASSERT_EQ(str.substr(7, std::min(static_cast<int>(str.size()) - 7, 30)),
+            Read(7, 30));
+  ASSERT_EQ("", Read(100, 100));
+}
+
+TEST_P(ReadaheadRandomAccessFileTest, SourceStrLenGreaterThanReadaheadSize) {
+  Random rng(42);
+  for (int k = 0; k < 100; ++k) {
+    size_t strLen = k * GetReadaheadSize() +
+                    rng.Uniform(static_cast<int>(GetReadaheadSize()));
+    std::string str =
+        test::RandomHumanReadableString(&rng, static_cast<int>(strLen));
+    ResetSourceStr(str);
+    for (int test = 1; test <= 100; ++test) {
+      size_t offset = rng.Uniform(static_cast<int>(strLen));
+      size_t n = rng.Uniform(static_cast<int>(GetReadaheadSize()));
+      ASSERT_EQ(str.substr(offset, std::min(n, strLen - offset)),
+                Read(offset, n));
+    }
+  }
+}
+
+TEST_P(ReadaheadRandomAccessFileTest, ReadExceedsReadaheadSize) {
+  Random rng(7);
+  size_t strLen = 4 * GetReadaheadSize() +
+                  rng.Uniform(static_cast<int>(GetReadaheadSize()));
+  std::string str =
+      test::RandomHumanReadableString(&rng, static_cast<int>(strLen));
+  ResetSourceStr(str);
+  for (int test = 1; test <= 100; ++test) {
+    size_t offset = rng.Uniform(static_cast<int>(strLen));
+    size_t n =
+        GetReadaheadSize() + rng.Uniform(static_cast<int>(GetReadaheadSize()));
+    ASSERT_EQ(str.substr(offset, std::min(n, strLen - offset)),
+              Read(offset, n));
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(
+    EmptySourceStr, ReadaheadRandomAccessFileTest,
+    ::testing::ValuesIn(ReadaheadRandomAccessFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    SourceStrLenLessThanReadaheadSize, ReadaheadRandomAccessFileTest,
+    ::testing::ValuesIn(ReadaheadRandomAccessFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    SourceStrLenGreaterThanReadaheadSize, ReadaheadRandomAccessFileTest,
+    ::testing::ValuesIn(ReadaheadRandomAccessFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    ReadExceedsReadaheadSize, ReadaheadRandomAccessFileTest,
+    ::testing::ValuesIn(ReadaheadRandomAccessFileTest::GetReadaheadSizeList()));
+
+class ReadaheadSequentialFileTest : public testing::Test,
+                                    public testing::WithParamInterface<size_t> {
+ public:
+  static std::vector<size_t> GetReadaheadSizeList() {
+    return {1lu << 8, 1lu << 12, 1lu << 16, 1lu << 18};
+  }
+  void SetUp() override {
+    readahead_size_ = GetParam();
+    scratch_.reset(new char[2 * readahead_size_]);
+    ResetSourceStr();
+  }
+  ReadaheadSequentialFileTest() {}
+  std::string Read(size_t n) {
+    Slice result;
+    test_read_holder_->Read(n, &result, scratch_.get());
+    return std::string(result.data(), result.size());
+  }
+  void Skip(size_t n) { test_read_holder_->Skip(n); }
+  void ResetSourceStr(const std::string& str = "") {
+    auto read_holder = std::unique_ptr<SequentialFile>(
+        new test::SeqStringSource(str, &seq_read_count_));
+    test_read_holder_.reset(new SequentialFileReader(
+        NewLegacySequentialFileWrapper(read_holder), "test", readahead_size_));
+  }
+  size_t GetReadaheadSize() const { return readahead_size_; }
+
+ private:
+  size_t readahead_size_;
+  std::unique_ptr<SequentialFileReader> test_read_holder_;
+  std::unique_ptr<char[]> scratch_;
+  std::atomic<int> seq_read_count_;
+};
+
+TEST_P(ReadaheadSequentialFileTest, EmptySourceStr) {
+  ASSERT_EQ("", Read(0));
+  ASSERT_EQ("", Read(1));
+  ASSERT_EQ("", Read(13));
+}
+
+TEST_P(ReadaheadSequentialFileTest, SourceStrLenLessThanReadaheadSize) {
+  std::string str = "abcdefghijklmnopqrs";
+  ResetSourceStr(str);
+  ASSERT_EQ(str.substr(0, 3), Read(3));
+  ASSERT_EQ(str.substr(3, 1), Read(1));
+  ASSERT_EQ(str.substr(4), Read(str.size()));
+  ASSERT_EQ("", Read(100));
+}
+
+TEST_P(ReadaheadSequentialFileTest, SourceStrLenGreaterThanReadaheadSize) {
+  Random rng(42);
+  for (int s = 0; s < 1; ++s) {
+    for (int k = 0; k < 100; ++k) {
+      size_t strLen = k * GetReadaheadSize() +
+                      rng.Uniform(static_cast<int>(GetReadaheadSize()));
+      std::string str =
+          test::RandomHumanReadableString(&rng, static_cast<int>(strLen));
+      ResetSourceStr(str);
+      size_t offset = 0;
+      for (int test = 1; test <= 100; ++test) {
+        size_t n = rng.Uniform(static_cast<int>(GetReadaheadSize()));
+        if (s && test % 2) {
+          Skip(n);
+        } else {
+          ASSERT_EQ(str.substr(offset, std::min(n, strLen - offset)), Read(n));
+        }
+        offset = std::min(offset + n, strLen);
+      }
+    }
+  }
+}
+
+TEST_P(ReadaheadSequentialFileTest, ReadExceedsReadaheadSize) {
+  Random rng(42);
+  for (int s = 0; s < 1; ++s) {
+    for (int k = 0; k < 100; ++k) {
+      size_t strLen = k * GetReadaheadSize() +
+                      rng.Uniform(static_cast<int>(GetReadaheadSize()));
+      std::string str =
+          test::RandomHumanReadableString(&rng, static_cast<int>(strLen));
+      ResetSourceStr(str);
+      size_t offset = 0;
+      for (int test = 1; test <= 100; ++test) {
+        size_t n = GetReadaheadSize() +
+                   rng.Uniform(static_cast<int>(GetReadaheadSize()));
+        if (s && test % 2) {
+          Skip(n);
+        } else {
+          ASSERT_EQ(str.substr(offset, std::min(n, strLen - offset)), Read(n));
+        }
+        offset = std::min(offset + n, strLen);
+      }
+    }
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(
+    EmptySourceStr, ReadaheadSequentialFileTest,
+    ::testing::ValuesIn(ReadaheadSequentialFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    SourceStrLenLessThanReadaheadSize, ReadaheadSequentialFileTest,
+    ::testing::ValuesIn(ReadaheadSequentialFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    SourceStrLenGreaterThanReadaheadSize, ReadaheadSequentialFileTest,
+    ::testing::ValuesIn(ReadaheadSequentialFileTest::GetReadaheadSizeList()));
+INSTANTIATE_TEST_CASE_P(
+    ReadExceedsReadaheadSize, ReadaheadSequentialFileTest,
+    ::testing::ValuesIn(ReadaheadSequentialFileTest::GetReadaheadSizeList()));
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/filelock_test.cc b/src/rocksdb/util/filelock_test.cc
new file mode 100644
index 000000000..20efd513f
--- /dev/null
+++ b/src/rocksdb/util/filelock_test.cc
@@ -0,0 +1,141 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#include "rocksdb/status.h"
+#include "rocksdb/env.h"
+
+#include <fcntl.h>
+#include <vector>
+#include "test_util/testharness.h"
+#include "util/coding.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class LockTest : public testing::Test {
+ public:
+  static LockTest* current_;
+  std::string file_;
+  ROCKSDB_NAMESPACE::Env* env_;
+
+  LockTest()
+      : file_(test::PerThreadDBPath("db_testlock_file")),
+        env_(ROCKSDB_NAMESPACE::Env::Default()) {
+    current_ = this;
+  }
+
+  ~LockTest() override {}
+
+  Status LockFile(FileLock** db_lock) {
+    return env_->LockFile(file_, db_lock);
+  }
+
+  Status UnlockFile(FileLock* db_lock) {
+    return env_->UnlockFile(db_lock);
+  }
+
+  bool AssertFileIsLocked(){
+    return CheckFileLock( /* lock_expected = */ true);
+  }
+
+  bool AssertFileIsNotLocked(){
+    return CheckFileLock( /* lock_expected = */ false);
+  }
+
+  bool CheckFileLock(bool lock_expected){
+    // We need to fork to check the fcntl lock as we need
+    // to open and close the file from a different process
+    // to avoid either releasing the lock on close, or not
+    // contending for it when requesting a lock.
+
+#ifdef OS_WIN
+
+    // WaitForSingleObject and GetExitCodeProcess can do what waitpid does.
+    // TODO - implement on Windows
+    return true;
+
+#else
+
+    pid_t pid = fork();
+    if ( 0 == pid ) {
+      // child process
+      int exit_val = EXIT_FAILURE;
+      int fd = open(file_.c_str(), O_RDWR | O_CREAT, 0644);
+      if (fd < 0) {
+        // could not open file, could not check if it was locked
+        fprintf( stderr, "Open on on file %s failed.\n",file_.c_str());
+        exit(exit_val);
+      }
+
+      struct flock f;
+      memset(&f, 0, sizeof(f));
+      f.l_type = (F_WRLCK);
+      f.l_whence = SEEK_SET;
+      f.l_start = 0;
+      f.l_len = 0; // Lock/unlock entire file
+      int value = fcntl(fd, F_SETLK, &f);
+      if( value == -1 ){
+        if( lock_expected ){
+          exit_val = EXIT_SUCCESS;
+        }
+      } else {
+        if( ! lock_expected ){
+          exit_val = EXIT_SUCCESS;
+        }
+      }
+      close(fd); // lock is released for child process
+      exit(exit_val);
+    } else if (pid > 0) {
+      // parent process
+      int status;
+      while (-1 == waitpid(pid, &status, 0));
+      if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+        // child process exited with non success status
+        return false;
+      } else {
+        return true;
+      }
+    } else {
+      fprintf( stderr, "Fork failed\n" );
+      return false;
+    }
+    return false;
+
+#endif
+
+  }
+
+};
+LockTest* LockTest::current_;
+
+TEST_F(LockTest, LockBySameThread) {
+  FileLock* lock1;
+  FileLock* lock2;
+
+  // acquire a lock on a file
+  ASSERT_OK(LockFile(&lock1));
+
+  // check the file is locked
+  ASSERT_TRUE( AssertFileIsLocked() );
+
+  // re-acquire the lock on the same file. This should fail.
+  ASSERT_TRUE(LockFile(&lock2).IsIOError());
+
+  // check the file is locked
+  ASSERT_TRUE( AssertFileIsLocked() );
+
+  // release the lock
+  ASSERT_OK(UnlockFile(lock1));
+
+  // check the file is not locked
+  ASSERT_TRUE( AssertFileIsNotLocked() );
+
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/filter_bench.cc b/src/rocksdb/util/filter_bench.cc
new file mode 100644
index 000000000..b474eee48
--- /dev/null
+++ b/src/rocksdb/util/filter_bench.cc
@@ -0,0 +1,751 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#if !defined(GFLAGS) || defined(ROCKSDB_LITE)
+#include <cstdio>
+int main() {
+  fprintf(stderr, "filter_bench requires gflags and !ROCKSDB_LITE\n");
+  return 1;
+}
+#else
+
+#include <cinttypes>
+#include <iostream>
+#include <sstream>
+#include <vector>
+
+#include "memory/arena.h"
+#include "port/port.h"
+#include "port/stack_trace.h"
+#include "table/block_based/filter_policy_internal.h"
+#include "table/block_based/full_filter_block.h"
+#include "table/block_based/mock_block_based_table.h"
+#include "table/plain/plain_table_bloom.h"
+#include "util/gflags_compat.h"
+#include "util/hash.h"
+#include "util/random.h"
+#include "util/stderr_logger.h"
+#include "util/stop_watch.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+using GFLAGS_NAMESPACE::RegisterFlagValidator;
+using GFLAGS_NAMESPACE::SetUsageMessage;
+
+DEFINE_uint32(seed, 0, "Seed for random number generators");
+
+DEFINE_double(working_mem_size_mb, 200,
+              "MB of memory to get up to among all filters, unless "
+              "m_keys_total_max is specified.");
+
+DEFINE_uint32(average_keys_per_filter, 10000,
+              "Average number of keys per filter");
+
+DEFINE_double(vary_key_count_ratio, 0.4,
+              "Vary number of keys by up to +/- vary_key_count_ratio * "
+              "average_keys_per_filter.");
+
+DEFINE_uint32(key_size, 24, "Average number of bytes for each key");
+
+DEFINE_bool(vary_key_alignment, true,
+            "Whether to vary key alignment (default: at least 32-bit "
+            "alignment)");
+
+DEFINE_uint32(vary_key_size_log2_interval, 5,
+              "Use same key size 2^n times, then change. Key size varies from "
+              "-2 to +2 bytes vs. average, unless n>=30 to fix key size.");
+
+DEFINE_uint32(batch_size, 8, "Number of keys to group in each batch");
+
+DEFINE_double(bits_per_key, 10.0, "Bits per key setting for filters");
+
+DEFINE_double(m_queries, 200, "Millions of queries for each test mode");
+
+DEFINE_double(m_keys_total_max, 0,
+              "Maximum total keys added to filters, in millions. "
+              "0 (default) disables. Non-zero overrides working_mem_size_mb "
+              "option.");
+
+DEFINE_bool(use_full_block_reader, false,
+            "Use FullFilterBlockReader interface rather than FilterBitsReader");
+
+DEFINE_bool(use_plain_table_bloom, false,
+            "Use PlainTableBloom structure and interface rather than "
+            "FilterBitsReader/FullFilterBlockReader");
+
+DEFINE_bool(new_builder, false,
+            "Whether to create a new builder for each new filter");
+
+DEFINE_uint32(impl, 0,
+              "Select filter implementation. Without -use_plain_table_bloom:"
+              "0 = full filter, 1 = block-based filter. With "
+              "-use_plain_table_bloom: 0 = no locality, 1 = locality.");
+
+DEFINE_bool(net_includes_hashing, false,
+            "Whether query net ns/op times should include hashing. "
+            "(if not, dry run will include hashing) "
+            "(build times always include hashing)");
+
+DEFINE_bool(quick, false, "Run more limited set of tests, fewer queries");
+
+DEFINE_bool(best_case, false, "Run limited tests only for best-case");
+
+DEFINE_bool(allow_bad_fp_rate, false, "Continue even if FP rate is bad");
+
+DEFINE_bool(legend, false,
+            "Print more information about interpreting results instead of "
+            "running tests");
+
+DEFINE_uint32(runs, 1, "Number of times to rebuild and run benchmark tests");
+
+void _always_assert_fail(int line, const char *file, const char *expr) {
+  fprintf(stderr, "%s: %d: Assertion %s failed\n", file, line, expr);
+  abort();
+}
+
+#define ALWAYS_ASSERT(cond) \
+  ((cond) ? (void)0 : ::_always_assert_fail(__LINE__, __FILE__, #cond))
+
+#ifndef NDEBUG
+// This could affect build times enough that we should not include it for
+// accurate speed tests
+#define PREDICT_FP_RATE
+#endif
+
+using ROCKSDB_NAMESPACE::Arena;
+using ROCKSDB_NAMESPACE::BlockContents;
+using ROCKSDB_NAMESPACE::BloomFilterPolicy;
+using ROCKSDB_NAMESPACE::BloomHash;
+using ROCKSDB_NAMESPACE::BuiltinFilterBitsBuilder;
+using ROCKSDB_NAMESPACE::CachableEntry;
+using ROCKSDB_NAMESPACE::EncodeFixed32;
+using ROCKSDB_NAMESPACE::fastrange32;
+using ROCKSDB_NAMESPACE::FilterBitsReader;
+using ROCKSDB_NAMESPACE::FilterBuildingContext;
+using ROCKSDB_NAMESPACE::FullFilterBlockReader;
+using ROCKSDB_NAMESPACE::GetSliceHash;
+using ROCKSDB_NAMESPACE::GetSliceHash64;
+using ROCKSDB_NAMESPACE::Lower32of64;
+using ROCKSDB_NAMESPACE::ParsedFullFilterBlock;
+using ROCKSDB_NAMESPACE::PlainTableBloomV1;
+using ROCKSDB_NAMESPACE::Random32;
+using ROCKSDB_NAMESPACE::Slice;
+using ROCKSDB_NAMESPACE::StderrLogger;
+using ROCKSDB_NAMESPACE::mock::MockBlockBasedTableTester;
+
+struct KeyMaker {
+  KeyMaker(size_t avg_size)
+      : smallest_size_(avg_size -
+                       (FLAGS_vary_key_size_log2_interval >= 30 ? 2 : 0)),
+        buf_size_(avg_size + 11),  // pad to vary key size and alignment
+        buf_(new char[buf_size_]) {
+    memset(buf_.get(), 0, buf_size_);
+    assert(smallest_size_ > 8);
+  }
+  size_t smallest_size_;
+  size_t buf_size_;
+  std::unique_ptr<char[]> buf_;
+
+  // Returns a unique(-ish) key based on the given parameter values. Each
+  // call returns a Slice from the same buffer so previously returned
+  // Slices should be considered invalidated.
+  Slice Get(uint32_t filter_num, uint32_t val_num) {
+    size_t start = FLAGS_vary_key_alignment ? val_num % 4 : 0;
+    size_t len = smallest_size_;
+    if (FLAGS_vary_key_size_log2_interval < 30) {
+      // To get range [avg_size - 2, avg_size + 2]
+      // use range [smallest_size, smallest_size + 4]
+      len += fastrange32(
+          (val_num >> FLAGS_vary_key_size_log2_interval) * 1234567891, 5);
+    }
+    char * data = buf_.get() + start;
+    // Populate key data such that all data makes it into a key of at
+    // least 8 bytes. We also don't want all the within-filter key
+    // variance confined to a contiguous 32 bits, because then a 32 bit
+    // hash function can "cheat" the false positive rate by
+    // approximating a perfect hash.
+    EncodeFixed32(data, val_num);
+    EncodeFixed32(data + 4, filter_num + val_num);
+    // ensure clearing leftovers from different alignment
+    EncodeFixed32(data + 8, 0);
+    return Slice(data, len);
+  }
+};
+
+void PrintWarnings() {
+#if defined(__GNUC__) && !defined(__OPTIMIZE__)
+  fprintf(stdout,
+          "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n");
+#endif
+#ifndef NDEBUG
+  fprintf(stdout,
+          "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
+#endif
+}
+
+struct FilterInfo {
+  uint32_t filter_id_ = 0;
+  std::unique_ptr<const char[]> owner_;
+  Slice filter_;
+  uint32_t keys_added_ = 0;
+  std::unique_ptr<FilterBitsReader> reader_;
+  std::unique_ptr<FullFilterBlockReader> full_block_reader_;
+  std::unique_ptr<PlainTableBloomV1> plain_table_bloom_;
+  uint64_t outside_queries_ = 0;
+  uint64_t false_positives_ = 0;
+};
+
+enum TestMode {
+  kSingleFilter,
+  kBatchPrepared,
+  kBatchUnprepared,
+  kFiftyOneFilter,
+  kEightyTwentyFilter,
+  kRandomFilter,
+};
+
+static const std::vector<TestMode> allTestModes = {
+    kSingleFilter,   kBatchPrepared,      kBatchUnprepared,
+    kFiftyOneFilter, kEightyTwentyFilter, kRandomFilter,
+};
+
+static const std::vector<TestMode> quickTestModes = {
+    kSingleFilter,
+    kRandomFilter,
+};
+
+static const std::vector<TestMode> bestCaseTestModes = {
+    kSingleFilter,
+};
+
+const char *TestModeToString(TestMode tm) {
+  switch (tm) {
+    case kSingleFilter:
+      return "Single filter";
+    case kBatchPrepared:
+      return "Batched, prepared";
+    case kBatchUnprepared:
+      return "Batched, unprepared";
+    case kFiftyOneFilter:
+      return "Skewed 50% in 1%";
+    case kEightyTwentyFilter:
+      return "Skewed 80% in 20%";
+    case kRandomFilter:
+      return "Random filter";
+  }
+  return "Bad TestMode";
+}
+
+// Do just enough to keep some data dependence for the
+// compiler / CPU
+static uint32_t DryRunNoHash(Slice &s) {
+  uint32_t sz = static_cast<uint32_t>(s.size());
+  if (sz >= 4) {
+    return sz + s.data()[3];
+  } else {
+    return sz;
+  }
+}
+
+static uint32_t DryRunHash32(Slice &s) {
+  // Same perf characteristics as GetSliceHash()
+  return BloomHash(s);
+}
+
+static uint32_t DryRunHash64(Slice &s) {
+  return Lower32of64(GetSliceHash64(s));
+}
+
+struct FilterBench : public MockBlockBasedTableTester {
+  std::vector<KeyMaker> kms_;
+  std::vector<FilterInfo> infos_;
+  Random32 random_;
+  std::ostringstream fp_rate_report_;
+  Arena arena_;
+  StderrLogger stderr_logger_;
+  double m_queries_;
+
+  FilterBench()
+      : MockBlockBasedTableTester(new BloomFilterPolicy(
+            FLAGS_bits_per_key,
+            static_cast<BloomFilterPolicy::Mode>(FLAGS_impl))),
+        random_(FLAGS_seed),
+        m_queries_(0) {
+    for (uint32_t i = 0; i < FLAGS_batch_size; ++i) {
+      kms_.emplace_back(FLAGS_key_size < 8 ? 8 : FLAGS_key_size);
+    }
+    ioptions_.info_log = &stderr_logger_;
+  }
+
+  void Go();
+
+  double RandomQueryTest(uint32_t inside_threshold, bool dry_run,
+                         TestMode mode);
+};
+
+void FilterBench::Go() {
+  if (FLAGS_use_plain_table_bloom && FLAGS_use_full_block_reader) {
+    throw std::runtime_error(
+        "Can't combine -use_plain_table_bloom and -use_full_block_reader");
+  }
+  if (FLAGS_use_plain_table_bloom) {
+    if (FLAGS_impl > 1) {
+      throw std::runtime_error(
+          "-impl must currently be >= 0 and <= 1 for Plain table");
+    }
+  } else {
+    if (FLAGS_impl == 1) {
+      throw std::runtime_error(
+          "Block-based filter not currently supported by filter_bench");
+    }
+    if (FLAGS_impl > 2) {
+      throw std::runtime_error(
+          "-impl must currently be 0 or 2 for Block-based table");
+    }
+  }
+
+  if (FLAGS_vary_key_count_ratio < 0.0 || FLAGS_vary_key_count_ratio > 1.0) {
+    throw std::runtime_error("-vary_key_count_ratio must be >= 0.0 and <= 1.0");
+  }
+
+  // For example, average_keys_per_filter = 100, vary_key_count_ratio = 0.1.
+  // Varys up to +/- 10 keys. variance_range = 21 (generating value 0..20).
+  // variance_offset = 10, so value - offset average value is always 0.
+  const uint32_t variance_range =
+      1 + 2 * static_cast<uint32_t>(FLAGS_vary_key_count_ratio *
+                                    FLAGS_average_keys_per_filter);
+  const uint32_t variance_offset = variance_range / 2;
+
+  const std::vector<TestMode> &testModes =
+      FLAGS_best_case ? bestCaseTestModes
+                      : FLAGS_quick ? quickTestModes : allTestModes;
+
+  m_queries_ = FLAGS_m_queries;
+  double working_mem_size_mb = FLAGS_working_mem_size_mb;
+  if (FLAGS_quick) {
+    m_queries_ /= 7.0;
+  } else if (FLAGS_best_case) {
+    m_queries_ /= 3.0;
+    working_mem_size_mb /= 10.0;
+  }
+
+  std::cout << "Building..." << std::endl;
+
+  std::unique_ptr<BuiltinFilterBitsBuilder> builder;
+
+  size_t total_memory_used = 0;
+  size_t total_keys_added = 0;
+#ifdef PREDICT_FP_RATE
+  double weighted_predicted_fp_rate = 0.0;
+#endif
+  size_t max_total_keys;
+  size_t max_mem;
+  if (FLAGS_m_keys_total_max > 0) {
+    max_total_keys = static_cast<size_t>(1000000 * FLAGS_m_keys_total_max);
+    max_mem = SIZE_MAX;
+  } else {
+    max_total_keys = SIZE_MAX;
+    max_mem = static_cast<size_t>(1024 * 1024 * working_mem_size_mb);
+  }
+
+  ROCKSDB_NAMESPACE::StopWatchNano timer(ROCKSDB_NAMESPACE::Env::Default(),
+                                         true);
+
+  infos_.clear();
+  while ((working_mem_size_mb == 0 || total_memory_used < max_mem) &&
+         total_keys_added < max_total_keys) {
+    uint32_t filter_id = random_.Next();
+    uint32_t keys_to_add = FLAGS_average_keys_per_filter +
+                           fastrange32(random_.Next(), variance_range) -
+                           variance_offset;
+    if (max_total_keys - total_keys_added < keys_to_add) {
+      keys_to_add = static_cast<uint32_t>(max_total_keys - total_keys_added);
+    }
+    infos_.emplace_back();
+    FilterInfo &info = infos_.back();
+    info.filter_id_ = filter_id;
+    info.keys_added_ = keys_to_add;
+    if (FLAGS_use_plain_table_bloom) {
+      info.plain_table_bloom_.reset(new PlainTableBloomV1());
+      info.plain_table_bloom_->SetTotalBits(
+          &arena_, static_cast<uint32_t>(keys_to_add * FLAGS_bits_per_key),
+          FLAGS_impl, 0 /*huge_page*/, nullptr /*logger*/);
+      for (uint32_t i = 0; i < keys_to_add; ++i) {
+        uint32_t hash = GetSliceHash(kms_[0].Get(filter_id, i));
+        info.plain_table_bloom_->AddHash(hash);
+      }
+      info.filter_ = info.plain_table_bloom_->GetRawData();
+    } else {
+      if (!builder) {
+        builder.reset(&dynamic_cast<BuiltinFilterBitsBuilder &>(*GetBuilder()));
+      }
+      for (uint32_t i = 0; i < keys_to_add; ++i) {
+        builder->AddKey(kms_[0].Get(filter_id, i));
+      }
+      info.filter_ = builder->Finish(&info.owner_);
+#ifdef PREDICT_FP_RATE
+      weighted_predicted_fp_rate +=
+          keys_to_add *
+          builder->EstimatedFpRate(keys_to_add, info.filter_.size());
+#endif
+      if (FLAGS_new_builder) {
+        builder.reset();
+      }
+      info.reader_.reset(
+          table_options_.filter_policy->GetFilterBitsReader(info.filter_));
+      CachableEntry<ParsedFullFilterBlock> block(
+          new ParsedFullFilterBlock(table_options_.filter_policy.get(),
+                                    BlockContents(info.filter_)),
+          nullptr /* cache */, nullptr /* cache_handle */,
+          true /* own_value */);
+      info.full_block_reader_.reset(
+          new FullFilterBlockReader(table_.get(), std::move(block)));
+    }
+    total_memory_used += info.filter_.size();
+    total_keys_added += keys_to_add;
+  }
+
+  uint64_t elapsed_nanos = timer.ElapsedNanos();
+  double ns = double(elapsed_nanos) / total_keys_added;
+  std::cout << "Build avg ns/key: " << ns << std::endl;
+  std::cout << "Number of filters: " << infos_.size() << std::endl;
+  std::cout << "Total memory (MB): " << total_memory_used / 1024.0 / 1024.0
+            << std::endl;
+
+  double bpk = total_memory_used * 8.0 / total_keys_added;
+  std::cout << "Bits/key actual: " << bpk << std::endl;
+#ifdef PREDICT_FP_RATE
+  std::cout << "Predicted FP rate %: "
+            << 100.0 * (weighted_predicted_fp_rate / total_keys_added)
+            << std::endl;
+#endif
+  if (!FLAGS_quick && !FLAGS_best_case) {
+    double tolerable_rate = std::pow(2.0, -(bpk - 1.0) / (1.4 + bpk / 50.0));
+    std::cout << "Best possible FP rate %: " << 100.0 * std::pow(2.0, -bpk)
+              << std::endl;
+    std::cout << "Tolerable FP rate %: " << 100.0 * tolerable_rate << std::endl;
+
+    std::cout << "----------------------------" << std::endl;
+    std::cout << "Verifying..." << std::endl;
+
+    uint32_t outside_q_per_f =
+        static_cast<uint32_t>(m_queries_ * 1000000 / infos_.size());
+    uint64_t fps = 0;
+    for (uint32_t i = 0; i < infos_.size(); ++i) {
+      FilterInfo &info = infos_[i];
+      for (uint32_t j = 0; j < info.keys_added_; ++j) {
+        if (FLAGS_use_plain_table_bloom) {
+          uint32_t hash = GetSliceHash(kms_[0].Get(info.filter_id_, j));
+          ALWAYS_ASSERT(info.plain_table_bloom_->MayContainHash(hash));
+        } else {
+          ALWAYS_ASSERT(
+              info.reader_->MayMatch(kms_[0].Get(info.filter_id_, j)));
+        }
+      }
+      for (uint32_t j = 0; j < outside_q_per_f; ++j) {
+        if (FLAGS_use_plain_table_bloom) {
+          uint32_t hash =
+              GetSliceHash(kms_[0].Get(info.filter_id_, j | 0x80000000));
+          fps += info.plain_table_bloom_->MayContainHash(hash);
+        } else {
+          fps += info.reader_->MayMatch(
+              kms_[0].Get(info.filter_id_, j | 0x80000000));
+        }
+      }
+    }
+    std::cout << " No FNs :)" << std::endl;
+    double prelim_rate = double(fps) / outside_q_per_f / infos_.size();
+    std::cout << " Prelim FP rate %: " << (100.0 * prelim_rate) << std::endl;
+
+    if (!FLAGS_allow_bad_fp_rate) {
+      ALWAYS_ASSERT(prelim_rate < tolerable_rate);
+    }
+  }
+
+  std::cout << "----------------------------" << std::endl;
+  std::cout << "Mixed inside/outside queries..." << std::endl;
+  // 50% each inside and outside
+  uint32_t inside_threshold = UINT32_MAX / 2;
+  for (TestMode tm : testModes) {
+    random_.Seed(FLAGS_seed + 1);
+    double f = RandomQueryTest(inside_threshold, /*dry_run*/ false, tm);
+    random_.Seed(FLAGS_seed + 1);
+    double d = RandomQueryTest(inside_threshold, /*dry_run*/ true, tm);
+    std::cout << "  " << TestModeToString(tm) << " net ns/op: " << (f - d)
+              << std::endl;
+  }
+
+  if (!FLAGS_quick) {
+    std::cout << "----------------------------" << std::endl;
+    std::cout << "Inside queries (mostly)..." << std::endl;
+    // Do about 95% inside queries rather than 100% so that branch predictor
+    // can't give itself an artifically crazy advantage.
+    inside_threshold = UINT32_MAX / 20 * 19;
+    for (TestMode tm : testModes) {
+      random_.Seed(FLAGS_seed + 1);
+      double f = RandomQueryTest(inside_threshold, /*dry_run*/ false, tm);
+      random_.Seed(FLAGS_seed + 1);
+      double d = RandomQueryTest(inside_threshold, /*dry_run*/ true, tm);
+      std::cout << "  " << TestModeToString(tm) << " net ns/op: " << (f - d)
+                << std::endl;
+    }
+
+    std::cout << "----------------------------" << std::endl;
+    std::cout << "Outside queries (mostly)..." << std::endl;
+    // Do about 95% outside queries rather than 100% so that branch predictor
+    // can't give itself an artifically crazy advantage.
+    inside_threshold = UINT32_MAX / 20;
+    for (TestMode tm : testModes) {
+      random_.Seed(FLAGS_seed + 2);
+      double f = RandomQueryTest(inside_threshold, /*dry_run*/ false, tm);
+      random_.Seed(FLAGS_seed + 2);
+      double d = RandomQueryTest(inside_threshold, /*dry_run*/ true, tm);
+      std::cout << "  " << TestModeToString(tm) << " net ns/op: " << (f - d)
+                << std::endl;
+    }
+  }
+  std::cout << fp_rate_report_.str();
+
+  std::cout << "----------------------------" << std::endl;
+  std::cout << "Done. (For more info, run with -legend or -help.)" << std::endl;
+}
+
+double FilterBench::RandomQueryTest(uint32_t inside_threshold, bool dry_run,
+                                    TestMode mode) {
+  for (auto &info : infos_) {
+    info.outside_queries_ = 0;
+    info.false_positives_ = 0;
+  }
+
+  auto dry_run_hash_fn = DryRunNoHash;
+  if (!FLAGS_net_includes_hashing) {
+    if (FLAGS_impl < 2 || FLAGS_use_plain_table_bloom) {
+      dry_run_hash_fn = DryRunHash32;
+    } else {
+      dry_run_hash_fn = DryRunHash64;
+    }
+  }
+
+  uint32_t num_infos = static_cast<uint32_t>(infos_.size());
+  uint32_t dry_run_hash = 0;
+  uint64_t max_queries = static_cast<uint64_t>(m_queries_ * 1000000 + 0.50);
+  // Some filters may be considered secondary in order to implement skewed
+  // queries. num_primary_filters is the number that are to be treated as
+  // equal, and any remainder will be treated as secondary.
+  uint32_t num_primary_filters = num_infos;
+  // The proportion (when divided by 2^32 - 1) of filter queries going to
+  // the primary filters (default = all). The remainder of queries are
+  // against secondary filters.
+  uint32_t primary_filter_threshold = 0xffffffff;
+  if (mode == kSingleFilter) {
+    // 100% of queries to 1 filter
+    num_primary_filters = 1;
+  } else if (mode == kFiftyOneFilter) {
+    // 50% of queries
+    primary_filter_threshold /= 2;
+    // to 1% of filters
+    num_primary_filters = (num_primary_filters + 99) / 100;
+  } else if (mode == kEightyTwentyFilter) {
+    // 80% of queries
+    primary_filter_threshold = primary_filter_threshold / 5 * 4;
+    // to 20% of filters
+    num_primary_filters = (num_primary_filters + 4) / 5;
+  }
+  uint32_t batch_size = 1;
+  std::unique_ptr<Slice[]> batch_slices;
+  std::unique_ptr<Slice *[]> batch_slice_ptrs;
+  std::unique_ptr<bool[]> batch_results;
+  if (mode == kBatchPrepared || mode == kBatchUnprepared) {
+    batch_size = static_cast<uint32_t>(kms_.size());
+  }
+
+  batch_slices.reset(new Slice[batch_size]);
+  batch_slice_ptrs.reset(new Slice *[batch_size]);
+  batch_results.reset(new bool[batch_size]);
+  for (uint32_t i = 0; i < batch_size; ++i) {
+    batch_results[i] = false;
+    batch_slice_ptrs[i] = &batch_slices[i];
+  }
+
+  ROCKSDB_NAMESPACE::StopWatchNano timer(ROCKSDB_NAMESPACE::Env::Default(),
+                                         true);
+
+  for (uint64_t q = 0; q < max_queries; q += batch_size) {
+    bool inside_this_time = random_.Next() <= inside_threshold;
+
+    uint32_t filter_index;
+    if (random_.Next() <= primary_filter_threshold) {
+      filter_index = random_.Uniformish(num_primary_filters);
+    } else {
+      // secondary
+      filter_index = num_primary_filters +
+                     random_.Uniformish(num_infos - num_primary_filters);
+    }
+    FilterInfo &info = infos_[filter_index];
+    for (uint32_t i = 0; i < batch_size; ++i) {
+      if (inside_this_time) {
+        batch_slices[i] =
+            kms_[i].Get(info.filter_id_, random_.Uniformish(info.keys_added_));
+      } else {
+        batch_slices[i] =
+            kms_[i].Get(info.filter_id_, random_.Uniformish(info.keys_added_) |
+                                             uint32_t{0x80000000});
+        info.outside_queries_++;
+      }
+    }
+    // TODO: implement batched interface to full block reader
+    // TODO: implement batched interface to plain table bloom
+    if (mode == kBatchPrepared && !FLAGS_use_full_block_reader &&
+        !FLAGS_use_plain_table_bloom) {
+      for (uint32_t i = 0; i < batch_size; ++i) {
+        batch_results[i] = false;
+      }
+      if (dry_run) {
+        for (uint32_t i = 0; i < batch_size; ++i) {
+          batch_results[i] = true;
+          dry_run_hash += dry_run_hash_fn(batch_slices[i]);
+        }
+      } else {
+        info.reader_->MayMatch(batch_size, batch_slice_ptrs.get(),
+                               batch_results.get());
+      }
+      for (uint32_t i = 0; i < batch_size; ++i) {
+        if (inside_this_time) {
+          ALWAYS_ASSERT(batch_results[i]);
+        } else {
+          info.false_positives_ += batch_results[i];
+        }
+      }
+    } else {
+      for (uint32_t i = 0; i < batch_size; ++i) {
+        bool may_match;
+        if (FLAGS_use_plain_table_bloom) {
+          if (dry_run) {
+            dry_run_hash += dry_run_hash_fn(batch_slices[i]);
+            may_match = true;
+          } else {
+            uint32_t hash = GetSliceHash(batch_slices[i]);
+            may_match = info.plain_table_bloom_->MayContainHash(hash);
+          }
+        } else if (FLAGS_use_full_block_reader) {
+          if (dry_run) {
+            dry_run_hash += dry_run_hash_fn(batch_slices[i]);
+            may_match = true;
+          } else {
+            may_match = info.full_block_reader_->KeyMayMatch(
+                batch_slices[i],
+                /*prefix_extractor=*/nullptr,
+                /*block_offset=*/ROCKSDB_NAMESPACE::kNotValid,
+                /*no_io=*/false, /*const_ikey_ptr=*/nullptr,
+                /*get_context=*/nullptr,
+                /*lookup_context=*/nullptr);
+          }
+        } else {
+          if (dry_run) {
+            dry_run_hash += dry_run_hash_fn(batch_slices[i]);
+            may_match = true;
+          } else {
+            may_match = info.reader_->MayMatch(batch_slices[i]);
+          }
+        }
+        if (inside_this_time) {
+          ALWAYS_ASSERT(may_match);
+        } else {
+          info.false_positives_ += may_match;
+        }
+      }
+    }
+  }
+
+  uint64_t elapsed_nanos = timer.ElapsedNanos();
+  double ns = double(elapsed_nanos) / max_queries;
+
+  if (!FLAGS_quick) {
+    if (dry_run) {
+      // Printing part of hash prevents dry run components from being optimized
+      // away by compiler
+      std::cout << "    Dry run (" << std::hex << (dry_run_hash & 0xfffff)
+                << std::dec << ") ";
+    } else {
+      std::cout << "    Gross filter    ";
+    }
+    std::cout << "ns/op: " << ns << std::endl;
+  }
+
+  if (!dry_run) {
+    fp_rate_report_.str("");
+    uint64_t q = 0;
+    uint64_t fp = 0;
+    double worst_fp_rate = 0.0;
+    double best_fp_rate = 1.0;
+    for (auto &info : infos_) {
+      q += info.outside_queries_;
+      fp += info.false_positives_;
+      if (info.outside_queries_ > 0) {
+        double fp_rate = double(info.false_positives_) / info.outside_queries_;
+        worst_fp_rate = std::max(worst_fp_rate, fp_rate);
+        best_fp_rate = std::min(best_fp_rate, fp_rate);
+      }
+    }
+    fp_rate_report_ << "    Average FP rate %: " << 100.0 * fp / q << std::endl;
+    if (!FLAGS_quick && !FLAGS_best_case) {
+      fp_rate_report_ << "    Worst   FP rate %: " << 100.0 * worst_fp_rate
+                      << std::endl;
+      fp_rate_report_ << "    Best    FP rate %: " << 100.0 * best_fp_rate
+                      << std::endl;
+      fp_rate_report_ << "    Best possible bits/key: "
+                      << -std::log(double(fp) / q) / std::log(2.0) << std::endl;
+    }
+  }
+  return ns;
+}
+
+int main(int argc, char **argv) {
+  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
+  SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
+                  " [-quick] [OTHER OPTIONS]...");
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  PrintWarnings();
+
+  if (FLAGS_legend) {
+    std::cout
+        << "Legend:" << std::endl
+        << "  \"Inside\" - key that was added to filter" << std::endl
+        << "  \"Outside\" - key that was not added to filter" << std::endl
+        << "  \"FN\" - false negative query (must not happen)" << std::endl
+        << "  \"FP\" - false positive query (OK at low rate)" << std::endl
+        << "  \"Dry run\" - cost of testing and hashing overhead." << std::endl
+        << "  \"Gross filter\" - cost of filter queries including testing "
+        << "\n     and hashing overhead." << std::endl
+        << "  \"net\" - best estimate of time in filter operation, without "
+        << "\n     testing and hashing overhead (gross filter - dry run)"
+        << std::endl
+        << "  \"ns/op\" - nanoseconds per operation (key query or add)"
+        << std::endl
+        << "  \"Single filter\" - essentially minimum cost, assuming filter"
+        << "\n     fits easily in L1 CPU cache." << std::endl
+        << "  \"Batched, prepared\" - several queries at once against a"
+        << "\n     randomly chosen filter, using multi-query interface."
+        << std::endl
+        << "  \"Batched, unprepared\" - similar, but using serial calls"
+        << "\n     to single query interface." << std::endl
+        << "  \"Random filter\" - a filter is chosen at random as target"
+        << "\n     of each query." << std::endl
+        << "  \"Skewed X% in Y%\" - like \"Random filter\" except Y% of"
+        << "\n      the filters are designated as \"hot\" and receive X%"
+        << "\n      of queries." << std::endl;
+  } else {
+    FilterBench b;
+    for (uint32_t i = 0; i < FLAGS_runs; ++i) {
+      b.Go();
+      FLAGS_seed += 100;
+      b.random_.Seed(FLAGS_seed);
+    }
+  }
+
+  return 0;
+}
+
+#endif  // !defined(GFLAGS) || defined(ROCKSDB_LITE)
diff --git a/src/rocksdb/util/gflags_compat.h b/src/rocksdb/util/gflags_compat.h
new file mode 100644
index 000000000..d5a30ce7e
--- /dev/null
+++ b/src/rocksdb/util/gflags_compat.h
@@ -0,0 +1,19 @@
+//  Copyright (c) 2017-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <gflags/gflags.h>
+
+#ifndef GFLAGS_NAMESPACE
+// in case it's not defined in old versions, that's probably because it was
+// still google by default.
+#define GFLAGS_NAMESPACE google
+#endif
+
+#ifndef DEFINE_uint32
+// DEFINE_uint32 does not appear in older versions of gflags. This should be
+// a sane definition for those versions.
+#define DEFINE_uint32(name, val, txt) \
+  DEFINE_VARIABLE(GFLAGS_NAMESPACE::uint32, U, name, val, txt)
+#endif
diff --git a/src/rocksdb/util/hash.cc b/src/rocksdb/util/hash.cc
new file mode 100644
index 000000000..d72be8a45
--- /dev/null
+++ b/src/rocksdb/util/hash.cc
@@ -0,0 +1,83 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <string.h>
+#include "util/coding.h"
+#include "util/hash.h"
+#include "util/util.h"
+#include "util/xxhash.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+uint32_t Hash(const char* data, size_t n, uint32_t seed) {
+  // MurmurHash1 - fast but mediocre quality
+  // https://github.com/aappleby/smhasher/wiki/MurmurHash1
+  //
+  const uint32_t m = 0xc6a4a793;
+  const uint32_t r = 24;
+  const char* limit = data + n;
+  uint32_t h = static_cast<uint32_t>(seed ^ (n * m));
+
+  // Pick up four bytes at a time
+  while (data + 4 <= limit) {
+    uint32_t w = DecodeFixed32(data);
+    data += 4;
+    h += w;
+    h *= m;
+    h ^= (h >> 16);
+  }
+
+  // Pick up remaining bytes
+  switch (limit - data) {
+    // Note: The original hash implementation used data[i] << shift, which
+    // promotes the char to int and then performs the shift. If the char is
+    // negative, the shift is undefined behavior in C++. The hash algorithm is
+    // part of the format definition, so we cannot change it; to obtain the same
+    // behavior in a legal way we just cast to uint32_t, which will do
+    // sign-extension. To guarantee compatibility with architectures where chars
+    // are unsigned we first cast the char to int8_t.
+    case 3:
+      h += static_cast<uint32_t>(static_cast<int8_t>(data[2])) << 16;
+      FALLTHROUGH_INTENDED;
+    case 2:
+      h += static_cast<uint32_t>(static_cast<int8_t>(data[1])) << 8;
+      FALLTHROUGH_INTENDED;
+    case 1:
+      h += static_cast<uint32_t>(static_cast<int8_t>(data[0]));
+      h *= m;
+      h ^= (h >> r);
+      break;
+  }
+  return h;
+}
+
+// We are standardizing on a preview release of XXH3, because that's
+// the best available at time of standardizing.
+//
+// In testing (mostly Intel Skylake), this hash function is much more
+// thorough than Hash32 and is almost universally faster. Hash() only
+// seems faster when passing runtime-sized keys of the same small size
+// (less than about 24 bytes) thousands of times in a row; this seems
+// to allow the branch predictor to work some magic. XXH3's speed is
+// much less dependent on branch prediction.
+//
+// Hashing with a prefix extractor is potentially a common case of
+// hashing objects of small, predictable size. We could consider
+// bundling hash functions specialized for particular lengths with
+// the prefix extractors.
+uint64_t Hash64(const char* data, size_t n, uint64_t seed) {
+  return XXH3p_64bits_withSeed(data, n, seed);
+}
+
+uint64_t Hash64(const char* data, size_t n) {
+  // Same as seed = 0
+  return XXH3p_64bits(data, n);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/hash.h b/src/rocksdb/util/hash.h
new file mode 100644
index 000000000..17490a366
--- /dev/null
+++ b/src/rocksdb/util/hash.h
@@ -0,0 +1,120 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Common hash functions with convenient interfaces. If hashing a
+// statically-sized input in a performance-critical context, consider
+// calling a specific hash implementation directly, such as
+// XXH3p_64bits from xxhash.h.
+//
+// Since this is a very common header, implementation details are kept
+// out-of-line. Out-of-lining also aids in tracking the time spent in
+// hashing functions. Inlining is of limited benefit for runtime-sized
+// hash inputs.
+
+#pragma once
+#include <stddef.h>
+#include <stdint.h>
+
+#include "rocksdb/slice.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Stable/persistent 64-bit hash. Higher quality and generally faster than
+// Hash(), especially for inputs > 24 bytes.
+extern uint64_t Hash64(const char* data, size_t n, uint64_t seed);
+
+// Specific optimization without seed (same as seed = 0)
+extern uint64_t Hash64(const char* data, size_t n);
+
+// Non-persistent hash. Must only used for in-memory data structure.
+// The hash results are thus applicable to change. (Thus, it rarely makes
+// sense to specify a seed for this function.)
+inline uint64_t NPHash64(const char* data, size_t n, uint32_t seed) {
+  // Currently same as Hash64
+  return Hash64(data, n, seed);
+}
+
+// Specific optimization without seed (same as seed = 0)
+inline uint64_t NPHash64(const char* data, size_t n) {
+  // Currently same as Hash64
+  return Hash64(data, n);
+}
+
+// Stable/persistent 32-bit hash. Moderate quality and high speed on
+// small inputs.
+// TODO: consider rename to Hash32
+extern uint32_t Hash(const char* data, size_t n, uint32_t seed);
+
+// TODO: consider rename to LegacyBloomHash32
+inline uint32_t BloomHash(const Slice& key) {
+  return Hash(key.data(), key.size(), 0xbc9f1d34);
+}
+
+inline uint64_t GetSliceHash64(const Slice& key) {
+  return Hash64(key.data(), key.size());
+}
+
+inline uint64_t GetSliceNPHash64(const Slice& s) {
+  return NPHash64(s.data(), s.size());
+}
+
+// TODO: consider rename to GetSliceHash32
+inline uint32_t GetSliceHash(const Slice& s) {
+  return Hash(s.data(), s.size(), 397);
+}
+
+// Useful for splitting up a 64-bit hash
+inline uint32_t Upper32of64(uint64_t v) {
+  return static_cast<uint32_t>(v >> 32);
+}
+inline uint32_t Lower32of64(uint64_t v) { return static_cast<uint32_t>(v); }
+
+// std::hash compatible interface.
+// TODO: consider rename to SliceHasher32
+struct SliceHasher {
+  uint32_t operator()(const Slice& s) const { return GetSliceHash(s); }
+};
+
+// An alternative to % for mapping a hash value to an arbitrary range. See
+// https://github.com/lemire/fastrange
+inline uint32_t fastrange32(uint32_t hash, uint32_t range) {
+  uint64_t product = uint64_t{range} * hash;
+  return static_cast<uint32_t>(product >> 32);
+}
+
+// An alternative to % for mapping a 64-bit hash value to an arbitrary range
+// that fits in size_t. See https://github.com/lemire/fastrange
+// We find size_t more convenient than uint64_t for the range, with side
+// benefit of better optimization on 32-bit platforms.
+inline size_t fastrange64(uint64_t hash, size_t range) {
+#if defined(HAVE_UINT128_EXTENSION)
+  // Can use compiler's 128-bit type. Trust it to do the right thing.
+  __uint128_t wide = __uint128_t{range} * hash;
+  return static_cast<size_t>(wide >> 64);
+#else
+  // Fall back: full decomposition.
+  // NOTE: GCC seems to fully understand this code as 64-bit x {32 or 64}-bit
+  // -> {96 or 128}-bit multiplication and optimize it down to a single
+  // wide-result multiplication (64-bit platform) or two wide-result
+  // multiplications (32-bit platforms, where range64 >> 32 is zero).
+  uint64_t range64 = range;  // ok to shift by 32, even if size_t is 32-bit
+  uint64_t tmp = uint64_t{range64 & 0xffffFFFF} * uint64_t{hash & 0xffffFFFF};
+  tmp >>= 32;
+  tmp += uint64_t{range64 & 0xffffFFFF} * uint64_t{hash >> 32};
+  // Avoid overflow: first add lower 32 of tmp2, and later upper 32
+  uint64_t tmp2 = uint64_t{range64 >> 32} * uint64_t{hash & 0xffffFFFF};
+  tmp += static_cast<uint32_t>(tmp2);
+  tmp >>= 32;
+  tmp += (tmp2 >> 32);
+  tmp += uint64_t{range64 >> 32} * uint64_t{hash >> 32};
+  return static_cast<size_t>(tmp);
+#endif
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/hash_map.h b/src/rocksdb/util/hash_map.h
new file mode 100644
index 000000000..6eb42506b
--- /dev/null
+++ b/src/rocksdb/util/hash_map.h
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <utility>
+
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// This is similar to std::unordered_map, except that it tries to avoid
+// allocating or deallocating memory as much as possible. With
+// std::unordered_map, an allocation/deallocation is made for every insertion
+// or deletion because of the requirement that iterators remain valid even
+// with insertions or deletions. This means that the hash chains will be
+// implemented as linked lists.
+//
+// This implementation uses autovector as hash chains insteads.
+//
+template <typename K, typename V, size_t size = 128>
+class HashMap {
+  std::array<autovector<std::pair<K, V>, 1>, size> table_;
+
+ public:
+  bool Contains(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    return it != bucket.end();
+  }
+
+  void Insert(K key, V value) {
+    auto& bucket = table_[key % size];
+    bucket.push_back({key, value});
+  }
+
+  void Delete(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    if (it != bucket.end()) {
+      auto last = bucket.end() - 1;
+      if (it != last) {
+        *it = *last;
+      }
+      bucket.pop_back();
+    }
+  }
+
+  V& Get(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    return it->second;
+  }
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/hash_test.cc b/src/rocksdb/util/hash_test.cc
new file mode 100644
index 000000000..9c3c6efe9
--- /dev/null
+++ b/src/rocksdb/util/hash_test.cc
@@ -0,0 +1,377 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstring>
+#include <vector>
+
+#include "test_util/testharness.h"
+#include "util/coding.h"
+#include "util/hash.h"
+
+using ROCKSDB_NAMESPACE::EncodeFixed32;
+using ROCKSDB_NAMESPACE::GetSliceHash64;
+using ROCKSDB_NAMESPACE::Hash;
+using ROCKSDB_NAMESPACE::Hash64;
+using ROCKSDB_NAMESPACE::Lower32of64;
+using ROCKSDB_NAMESPACE::Slice;
+using ROCKSDB_NAMESPACE::Upper32of64;
+
+// The hash algorithm is part of the file format, for example for the Bloom
+// filters. Test that the hash values are stable for a set of random strings of
+// varying lengths.
+TEST(HashTest, Values) {
+  constexpr uint32_t kSeed = 0xbc9f1d34;  // Same as BloomHash.
+
+  EXPECT_EQ(Hash("", 0, kSeed), 3164544308u);
+  EXPECT_EQ(Hash("\x08", 1, kSeed), 422599524u);
+  EXPECT_EQ(Hash("\x17", 1, kSeed), 3168152998u);
+  EXPECT_EQ(Hash("\x9a", 1, kSeed), 3195034349u);
+  EXPECT_EQ(Hash("\x1c", 1, kSeed), 2651681383u);
+  EXPECT_EQ(Hash("\x4d\x76", 2, kSeed), 2447836956u);
+  EXPECT_EQ(Hash("\x52\xd5", 2, kSeed), 3854228105u);
+  EXPECT_EQ(Hash("\x91\xf7", 2, kSeed), 31066776u);
+  EXPECT_EQ(Hash("\xd6\x27", 2, kSeed), 1806091603u);
+  EXPECT_EQ(Hash("\x30\x46\x0b", 3, kSeed), 3808221797u);
+  EXPECT_EQ(Hash("\x56\xdc\xd6", 3, kSeed), 2157698265u);
+  EXPECT_EQ(Hash("\xd4\x52\x33", 3, kSeed), 1721992661u);
+  EXPECT_EQ(Hash("\x6a\xb5\xf4", 3, kSeed), 2469105222u);
+  EXPECT_EQ(Hash("\x67\x53\x81\x1c", 4, kSeed), 118283265u);
+  EXPECT_EQ(Hash("\x69\xb8\xc0\x88", 4, kSeed), 3416318611u);
+  EXPECT_EQ(Hash("\x1e\x84\xaf\x2d", 4, kSeed), 3315003572u);
+  EXPECT_EQ(Hash("\x46\xdc\x54\xbe", 4, kSeed), 447346355u);
+  EXPECT_EQ(Hash("\xd0\x7a\x6e\xea\x56", 5, kSeed), 4255445370u);
+  EXPECT_EQ(Hash("\x86\x83\xd5\xa4\xd8", 5, kSeed), 2390603402u);
+  EXPECT_EQ(Hash("\xb7\x46\xbb\x77\xce", 5, kSeed), 2048907743u);
+  EXPECT_EQ(Hash("\x6c\xa8\xbc\xe5\x99", 5, kSeed), 2177978500u);
+  EXPECT_EQ(Hash("\x5c\x5e\xe1\xa0\x73\x81", 6, kSeed), 1036846008u);
+  EXPECT_EQ(Hash("\x08\x5d\x73\x1c\xe5\x2e", 6, kSeed), 229980482u);
+  EXPECT_EQ(Hash("\x42\xfb\xf2\x52\xb4\x10", 6, kSeed), 3655585422u);
+  EXPECT_EQ(Hash("\x73\xe1\xff\x56\x9c\xce", 6, kSeed), 3502708029u);
+  EXPECT_EQ(Hash("\x5c\xbe\x97\x75\x54\x9a\x52", 7, kSeed), 815120748u);
+  EXPECT_EQ(Hash("\x16\x82\x39\x49\x88\x2b\x36", 7, kSeed), 3056033698u);
+  EXPECT_EQ(Hash("\x59\x77\xf0\xa7\x24\xf4\x78", 7, kSeed), 587205227u);
+  EXPECT_EQ(Hash("\xd3\xa5\x7c\x0e\xc0\x02\x07", 7, kSeed), 2030937252u);
+  EXPECT_EQ(Hash("\x31\x1b\x98\x75\x96\x22\xd3\x9a", 8, kSeed), 469635402u);
+  EXPECT_EQ(Hash("\x38\xd6\xf7\x28\x20\xb4\x8a\xe9", 8, kSeed), 3530274698u);
+  EXPECT_EQ(Hash("\xbb\x18\x5d\xf4\x12\x03\xf7\x99", 8, kSeed), 1974545809u);
+  EXPECT_EQ(Hash("\x80\xd4\x3b\x3b\xae\x22\xa2\x78", 8, kSeed), 3563570120u);
+  EXPECT_EQ(Hash("\x1a\xb5\xd0\xfe\xab\xc3\x61\xb2\x99", 9, kSeed),
+            2706087434u);
+  EXPECT_EQ(Hash("\x8e\x4a\xc3\x18\x20\x2f\x06\xe6\x3c", 9, kSeed),
+            1534654151u);
+  EXPECT_EQ(Hash("\xb6\xc0\xdd\x05\x3f\xc4\x86\x4c\xef", 9, kSeed),
+            2355554696u);
+  EXPECT_EQ(Hash("\x9a\x5f\x78\x0d\xaf\x50\xe1\x1f\x55", 9, kSeed),
+            1400800912u);
+  EXPECT_EQ(Hash("\x22\x6f\x39\x1f\xf8\xdd\x4f\x52\x17\x94", 10, kSeed),
+            3420325137u);
+  EXPECT_EQ(Hash("\x32\x89\x2a\x75\x48\x3a\x4a\x02\x69\xdd", 10, kSeed),
+            3427803584u);
+  EXPECT_EQ(Hash("\x06\x92\x5c\xf4\x88\x0e\x7e\x68\x38\x3e", 10, kSeed),
+            1152407945u);
+  EXPECT_EQ(Hash("\xbd\x2c\x63\x38\xbf\xe9\x78\xb7\xbf\x15", 10, kSeed),
+            3382479516u);
+}
+
+// The hash algorithm is part of the file format, for example for the Bloom
+// filters.
+TEST(HashTest, Hash64Misc) {
+  constexpr uint32_t kSeed = 0;  // Same as GetSliceHash64
+
+  for (char fill : {'\0', 'a', '1', '\xff'}) {
+    const size_t max_size = 1000;
+    const std::string str(max_size, fill);
+
+    for (size_t size = 0; size <= max_size; ++size) {
+      uint64_t here = Hash64(str.data(), size, kSeed);
+
+      // Must be same as GetSliceHash64
+      EXPECT_EQ(here, GetSliceHash64(Slice(str.data(), size)));
+
+      // Upper and Lower must reconstruct hash
+      EXPECT_EQ(here, (uint64_t{Upper32of64(here)} << 32) | Lower32of64(here));
+      EXPECT_EQ(here, (uint64_t{Upper32of64(here)} << 32) + Lower32of64(here));
+      EXPECT_EQ(here, (uint64_t{Upper32of64(here)} << 32) ^ Lower32of64(here));
+
+      // Seed changes hash value (with high probability)
+      for (uint64_t var_seed = 1; var_seed != 0; var_seed <<= 1) {
+        EXPECT_NE(here, Hash64(str.data(), size, var_seed));
+      }
+
+      // Size changes hash value (with high probability)
+      size_t max_smaller_by = std::min(size_t{30}, size);
+      for (size_t smaller_by = 1; smaller_by <= max_smaller_by; ++smaller_by) {
+        EXPECT_NE(here, Hash64(str.data(), size - smaller_by, kSeed));
+      }
+    }
+  }
+}
+
+// Test that hash values are "non-trivial" for "trivial" inputs
+TEST(HashTest, Hash64Trivial) {
+  // Thorough test too slow for regression testing
+  constexpr bool thorough = false;
+
+  // For various seeds, make sure hash of empty string is not zero.
+  constexpr uint64_t max_seed = thorough ? 0x1000000 : 0x10000;
+  for (uint64_t seed = 0; seed < max_seed; ++seed) {
+    uint64_t here = Hash64("", 0, seed);
+    EXPECT_NE(Lower32of64(here), 0u);
+    EXPECT_NE(Upper32of64(here), 0u);
+  }
+
+  // For standard seed, make sure hash of small strings are not zero
+  constexpr uint32_t kSeed = 0;  // Same as GetSliceHash64
+  char input[4];
+  constexpr int max_len = thorough ? 3 : 2;
+  for (int len = 1; len <= max_len; ++len) {
+    for (uint32_t i = 0; (i >> (len * 8)) == 0; ++i) {
+      EncodeFixed32(input, i);
+      uint64_t here = Hash64(input, len, kSeed);
+      EXPECT_NE(Lower32of64(here), 0u);
+      EXPECT_NE(Upper32of64(here), 0u);
+    }
+  }
+}
+
+// Test that the hash values are stable for a set of random strings of
+// varying small lengths.
+TEST(HashTest, Hash64SmallValueSchema) {
+  constexpr uint32_t kSeed = 0;  // Same as GetSliceHash64
+
+  EXPECT_EQ(Hash64("", 0, kSeed), uint64_t{5999572062939766020u});
+  EXPECT_EQ(Hash64("\x08", 1, kSeed), uint64_t{583283813901344696u});
+  EXPECT_EQ(Hash64("\x17", 1, kSeed), uint64_t{16175549975585474943u});
+  EXPECT_EQ(Hash64("\x9a", 1, kSeed), uint64_t{16322991629225003903u});
+  EXPECT_EQ(Hash64("\x1c", 1, kSeed), uint64_t{13269285487706833447u});
+  EXPECT_EQ(Hash64("\x4d\x76", 2, kSeed), uint64_t{6859542833406258115u});
+  EXPECT_EQ(Hash64("\x52\xd5", 2, kSeed), uint64_t{4919611532550636959u});
+  EXPECT_EQ(Hash64("\x91\xf7", 2, kSeed), uint64_t{14199427467559720719u});
+  EXPECT_EQ(Hash64("\xd6\x27", 2, kSeed), uint64_t{12292689282614532691u});
+  EXPECT_EQ(Hash64("\x30\x46\x0b", 3, kSeed), uint64_t{11404699285340020889u});
+  EXPECT_EQ(Hash64("\x56\xdc\xd6", 3, kSeed), uint64_t{12404347133785524237u});
+  EXPECT_EQ(Hash64("\xd4\x52\x33", 3, kSeed), uint64_t{15853805298481534034u});
+  EXPECT_EQ(Hash64("\x6a\xb5\xf4", 3, kSeed), uint64_t{16863488758399383382u});
+  EXPECT_EQ(Hash64("\x67\x53\x81\x1c", 4, kSeed),
+            uint64_t{9010661983527562386u});
+  EXPECT_EQ(Hash64("\x69\xb8\xc0\x88", 4, kSeed),
+            uint64_t{6611781377647041447u});
+  EXPECT_EQ(Hash64("\x1e\x84\xaf\x2d", 4, kSeed),
+            uint64_t{15290969111616346501u});
+  EXPECT_EQ(Hash64("\x46\xdc\x54\xbe", 4, kSeed),
+            uint64_t{7063754590279313623u});
+  EXPECT_EQ(Hash64("\xd0\x7a\x6e\xea\x56", 5, kSeed),
+            uint64_t{6384167718754869899u});
+  EXPECT_EQ(Hash64("\x86\x83\xd5\xa4\xd8", 5, kSeed),
+            uint64_t{16874407254108011067u});
+  EXPECT_EQ(Hash64("\xb7\x46\xbb\x77\xce", 5, kSeed),
+            uint64_t{16809880630149135206u});
+  EXPECT_EQ(Hash64("\x6c\xa8\xbc\xe5\x99", 5, kSeed),
+            uint64_t{1249038833153141148u});
+  EXPECT_EQ(Hash64("\x5c\x5e\xe1\xa0\x73\x81", 6, kSeed),
+            uint64_t{17358142495308219330u});
+  EXPECT_EQ(Hash64("\x08\x5d\x73\x1c\xe5\x2e", 6, kSeed),
+            uint64_t{4237646583134806322u});
+  EXPECT_EQ(Hash64("\x42\xfb\xf2\x52\xb4\x10", 6, kSeed),
+            uint64_t{4373664924115234051u});
+  EXPECT_EQ(Hash64("\x73\xe1\xff\x56\x9c\xce", 6, kSeed),
+            uint64_t{12012981210634596029u});
+  EXPECT_EQ(Hash64("\x5c\xbe\x97\x75\x54\x9a\x52", 7, kSeed),
+            uint64_t{5716522398211028826u});
+  EXPECT_EQ(Hash64("\x16\x82\x39\x49\x88\x2b\x36", 7, kSeed),
+            uint64_t{15604531309862565013u});
+  EXPECT_EQ(Hash64("\x59\x77\xf0\xa7\x24\xf4\x78", 7, kSeed),
+            uint64_t{8601330687345614172u});
+  EXPECT_EQ(Hash64("\xd3\xa5\x7c\x0e\xc0\x02\x07", 7, kSeed),
+            uint64_t{8088079329364056942u});
+  EXPECT_EQ(Hash64("\x31\x1b\x98\x75\x96\x22\xd3\x9a", 8, kSeed),
+            uint64_t{9844314944338447628u});
+  EXPECT_EQ(Hash64("\x38\xd6\xf7\x28\x20\xb4\x8a\xe9", 8, kSeed),
+            uint64_t{10973293517982163143u});
+  EXPECT_EQ(Hash64("\xbb\x18\x5d\xf4\x12\x03\xf7\x99", 8, kSeed),
+            uint64_t{9986007080564743219u});
+  EXPECT_EQ(Hash64("\x80\xd4\x3b\x3b\xae\x22\xa2\x78", 8, kSeed),
+            uint64_t{1729303145008254458u});
+  EXPECT_EQ(Hash64("\x1a\xb5\xd0\xfe\xab\xc3\x61\xb2\x99", 9, kSeed),
+            uint64_t{13253403748084181481u});
+  EXPECT_EQ(Hash64("\x8e\x4a\xc3\x18\x20\x2f\x06\xe6\x3c", 9, kSeed),
+            uint64_t{7768754303876232188u});
+  EXPECT_EQ(Hash64("\xb6\xc0\xdd\x05\x3f\xc4\x86\x4c\xef", 9, kSeed),
+            uint64_t{12439346786701492u});
+  EXPECT_EQ(Hash64("\x9a\x5f\x78\x0d\xaf\x50\xe1\x1f\x55", 9, kSeed),
+            uint64_t{10841838338450144690u});
+  EXPECT_EQ(Hash64("\x22\x6f\x39\x1f\xf8\xdd\x4f\x52\x17\x94", 10, kSeed),
+            uint64_t{12883919702069153152u});
+  EXPECT_EQ(Hash64("\x32\x89\x2a\x75\x48\x3a\x4a\x02\x69\xdd", 10, kSeed),
+            uint64_t{12692903507676842188u});
+  EXPECT_EQ(Hash64("\x06\x92\x5c\xf4\x88\x0e\x7e\x68\x38\x3e", 10, kSeed),
+            uint64_t{6540985900674032620u});
+  EXPECT_EQ(Hash64("\xbd\x2c\x63\x38\xbf\xe9\x78\xb7\xbf\x15", 10, kSeed),
+            uint64_t{10551812464348219044u});
+}
+
+std::string Hash64TestDescriptor(const char *repeat, size_t limit) {
+  const char *mod61_encode =
+      "abcdefghijklmnopqrstuvwxyz123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+  std::string input;
+  while (input.size() < limit) {
+    input.append(repeat);
+  }
+  std::string rv;
+  for (size_t i = 0; i < limit; ++i) {
+    uint64_t h = GetSliceHash64(Slice(input.data(), i));
+    rv.append(1, mod61_encode[static_cast<size_t>(h % 61)]);
+  }
+  return rv;
+}
+
+// XXH3p changes its algorithm for various sizes up through 250 bytes, so
+// we need to check the stability of larger sizes also.
+TEST(HashTest, Hash64LargeValueSchema) {
+  // Each of these derives a "descriptor" from the hash values for all
+  // lengths up to 430.
+  // Note that "c" is common for the zero-length string.
+  EXPECT_EQ(
+      Hash64TestDescriptor("foo", 430),
+      "cRhyWsY67B6klRA1udmOuiYuX7IthyGBKqbeosz2hzVglWCmQx8nEdnpkvPfYX56Up2OWOTV"
+      "lTzfAoYwvtqKzjD8E9xttR2unelbXbIV67NUe6bOO23BxaSFRcA3njGu5cUWfgwOqNoTsszp"
+      "uPvKRP6qaUR5VdoBkJUCFIefd7edlNK5mv6JYWaGdwxehg65hTkTmjZoPKxTZo4PLyzbL9U4"
+      "xt12ITSfeP2MfBHuLI2z2pDlBb44UQKVMx27LEoAHsdLp3WfWfgH3sdRBRCHm33UxCM4QmE2"
+      "xJ7gqSvNwTeH7v9GlC8zWbGroyD3UVNeShMLx29O7tH1biemLULwAHyIw8zdtLMDpEJ8m2ic"
+      "l6Lb4fDuuFNAs1GCVUthjK8CV8SWI8Rsz5THSwn5CGhpqUwSZcFknjwWIl5rNCvDxXJqYr");
+  // Note that "1EeRk" is common for "Rocks"
+  EXPECT_EQ(
+      Hash64TestDescriptor("Rocks", 430),
+      "c1EeRkrzgOYWLA8PuhJrwTePJewoB44WdXYDfhbk3ZxTqqg25WlPExDl7IKIQLJvnA6gJxxn"
+      "9TCSLkFGfJeXehaSS1GBqWSzfhEH4VXiXIUCuxJXxtKXcSC6FrNIQGTZbYDiUOLD6Y5inzrF"
+      "9etwQhXUBanw55xAUdNMFQAm2GjJ6UDWp2mISLiMMkLjANWMKLaZMqaFLX37qB4MRO1ooVRv"
+      "zSvaNRSCLxlggQCasQq8icWjzf3HjBlZtU6pd4rkaUxSzHqmo9oM5MghbU5Rtxg8wEfO7lVN"
+      "5wdMONYecslQTwjZUpO1K3LDf3K3XK6sUXM6ShQQ3RHmMn2acB4YtTZ3QQcHYJSOHn2DuWpa"
+      "Q8RqzX5lab92YmOLaCdOHq1BPsM7SIBzMdLgePNsJ1vvMALxAaoDUHPxoFLO2wx18IXnyX");
+  EXPECT_EQ(
+      Hash64TestDescriptor("RocksDB", 430),
+      "c1EeRkukbkb28wLTahwD2sfUhZzaBEnF8SVrxnPVB6A7b8CaAl3UKsDZISF92GSq2wDCukOq"
+      "Jgrsp7A3KZhDiLW8dFXp8UPqPxMCRlMdZeVeJ2dJxrmA6cyt99zkQFj7ELbut6jAeVqARFnw"
+      "fnWVXOsaLrq7bDCbMcns2DKvTaaqTCLMYxI7nhtLpFN1jR755FRQFcOzrrDbh7QhypjdvlYw"
+      "cdAMSZgp9JMHxbM23wPSuH6BOFgxejz35PScZfhDPvTOxIy1jc3MZsWrMC3P324zNolO7JdW"
+      "CX2I5UDKjjaEJfxbgVgJIXxtQGlmj2xkO5sPpjULQV4X2HlY7FQleJ4QRaJIB4buhCA4vUTF"
+      "eMFlxCIYUpTCsal2qsmnGOWa8WCcefrohMjDj1fjzSvSaQwlpyR1GZHF2uPOoQagiCpHpm");
+}
+
+TEST(Fastrange32Test, Values) {
+  using ROCKSDB_NAMESPACE::fastrange32;
+  // Zero range
+  EXPECT_EQ(fastrange32(0, 0), 0U);
+  EXPECT_EQ(fastrange32(123, 0), 0U);
+  EXPECT_EQ(fastrange32(0xffffffff, 0), 0U);
+
+  // One range
+  EXPECT_EQ(fastrange32(0, 1), 0U);
+  EXPECT_EQ(fastrange32(123, 1), 0U);
+  EXPECT_EQ(fastrange32(0xffffffff, 1), 0U);
+
+  // Two range
+  EXPECT_EQ(fastrange32(0, 2), 0U);
+  EXPECT_EQ(fastrange32(123, 2), 0U);
+  EXPECT_EQ(fastrange32(0x7fffffff, 2), 0U);
+  EXPECT_EQ(fastrange32(0x80000000, 2), 1U);
+  EXPECT_EQ(fastrange32(0xffffffff, 2), 1U);
+
+  // Seven range
+  EXPECT_EQ(fastrange32(0, 7), 0U);
+  EXPECT_EQ(fastrange32(123, 7), 0U);
+  EXPECT_EQ(fastrange32(613566756, 7), 0U);
+  EXPECT_EQ(fastrange32(613566757, 7), 1U);
+  EXPECT_EQ(fastrange32(1227133513, 7), 1U);
+  EXPECT_EQ(fastrange32(1227133514, 7), 2U);
+  // etc.
+  EXPECT_EQ(fastrange32(0xffffffff, 7), 6U);
+
+  // Big
+  EXPECT_EQ(fastrange32(1, 0x80000000), 0U);
+  EXPECT_EQ(fastrange32(2, 0x80000000), 1U);
+  EXPECT_EQ(fastrange32(4, 0x7fffffff), 1U);
+  EXPECT_EQ(fastrange32(4, 0x80000000), 2U);
+  EXPECT_EQ(fastrange32(0xffffffff, 0x7fffffff), 0x7ffffffeU);
+  EXPECT_EQ(fastrange32(0xffffffff, 0x80000000), 0x7fffffffU);
+}
+
+TEST(Fastrange64Test, Values) {
+  using ROCKSDB_NAMESPACE::fastrange64;
+  // Zero range
+  EXPECT_EQ(fastrange64(0, 0), 0U);
+  EXPECT_EQ(fastrange64(123, 0), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFF, 0), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 0), 0U);
+
+  // One range
+  EXPECT_EQ(fastrange64(0, 1), 0U);
+  EXPECT_EQ(fastrange64(123, 1), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFF, 1), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 1), 0U);
+
+  // Two range
+  EXPECT_EQ(fastrange64(0, 2), 0U);
+  EXPECT_EQ(fastrange64(123, 2), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFF, 2), 0U);
+  EXPECT_EQ(fastrange64(0x7fffFFFFffffFFFF, 2), 0U);
+  EXPECT_EQ(fastrange64(0x8000000000000000, 2), 1U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 2), 1U);
+
+  // Seven range
+  EXPECT_EQ(fastrange64(0, 7), 0U);
+  EXPECT_EQ(fastrange64(123, 7), 0U);
+  EXPECT_EQ(fastrange64(0xffffFFFF, 7), 0U);
+  EXPECT_EQ(fastrange64(2635249153387078802, 7), 0U);
+  EXPECT_EQ(fastrange64(2635249153387078803, 7), 1U);
+  EXPECT_EQ(fastrange64(5270498306774157604, 7), 1U);
+  EXPECT_EQ(fastrange64(5270498306774157605, 7), 2U);
+  EXPECT_EQ(fastrange64(0x7fffFFFFffffFFFF, 7), 3U);
+  EXPECT_EQ(fastrange64(0x8000000000000000, 7), 3U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 7), 6U);
+
+  // Big but 32-bit range
+  EXPECT_EQ(fastrange64(0x100000000, 0x80000000), 0U);
+  EXPECT_EQ(fastrange64(0x200000000, 0x80000000), 1U);
+  EXPECT_EQ(fastrange64(0x400000000, 0x7fffFFFF), 1U);
+  EXPECT_EQ(fastrange64(0x400000000, 0x80000000), 2U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 0x7fffFFFF), 0x7fffFFFEU);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 0x80000000), 0x7fffFFFFU);
+
+  // Big, > 32-bit range
+#if SIZE_MAX == UINT64_MAX
+  EXPECT_EQ(fastrange64(0x7fffFFFFffffFFFF, 0x4200000002), 0x2100000000U);
+  EXPECT_EQ(fastrange64(0x8000000000000000, 0x4200000002), 0x2100000001U);
+
+  EXPECT_EQ(fastrange64(0x0000000000000000, 420000000002), 0U);
+  EXPECT_EQ(fastrange64(0x7fffFFFFffffFFFF, 420000000002), 210000000000U);
+  EXPECT_EQ(fastrange64(0x8000000000000000, 420000000002), 210000000001U);
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 420000000002), 420000000001U);
+
+  EXPECT_EQ(fastrange64(0xffffFFFFffffFFFF, 0xffffFFFFffffFFFF),
+            0xffffFFFFffffFFFEU);
+#endif
+}
+
+// for inspection of disassembly
+uint32_t fastrange32(uint32_t hash, uint32_t range) {
+  return ROCKSDB_NAMESPACE::fastrange32(hash, range);
+}
+
+// for inspection of disassembly
+size_t fastrange64(uint64_t hash, size_t range) {
+  return ROCKSDB_NAMESPACE::fastrange64(hash, range);
+}
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/heap.h b/src/rocksdb/util/heap.h
new file mode 100644
index 000000000..c72d944d3
--- /dev/null
+++ b/src/rocksdb/util/heap.h
@@ -0,0 +1,166 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <algorithm>
+#include <cstdint>
+#include <functional>
+#include "port/port.h"
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Binary heap implementation optimized for use in multi-way merge sort.
+// Comparison to std::priority_queue:
+// - In libstdc++, std::priority_queue::pop() usually performs just over logN
+//   comparisons but never fewer.
+// - std::priority_queue does not have a replace-top operation, requiring a
+//   pop+push.  If the replacement element is the new top, this requires
+//   around 2logN comparisons.
+// - This heap's pop() uses a "schoolbook" downheap which requires up to ~2logN
+//   comparisons.
+// - This heap provides a replace_top() operation which requires [1, 2logN]
+//   comparisons.  When the replacement element is also the new top, this
+//   takes just 1 or 2 comparisons.
+//
+// The last property can yield an order-of-magnitude performance improvement
+// when merge-sorting real-world non-random data.  If the merge operation is
+// likely to take chunks of elements from the same input stream, only 1
+// comparison per element is needed.  In RocksDB-land, this happens when
+// compacting a database where keys are not randomly distributed across L0
+// files but nearby keys are likely to be in the same L0 file.
+//
+// The container uses the same counterintuitive ordering as
+// std::priority_queue: the comparison operator is expected to provide the
+// less-than relation, but top() will return the maximum.
+
+template<typename T, typename Compare = std::less<T>>
+class BinaryHeap {
+ public:
+  BinaryHeap() { }
+  explicit BinaryHeap(Compare cmp) : cmp_(std::move(cmp)) { }
+
+  void push(const T& value) {
+    data_.push_back(value);
+    upheap(data_.size() - 1);
+  }
+
+  void push(T&& value) {
+    data_.push_back(std::move(value));
+    upheap(data_.size() - 1);
+  }
+
+  const T& top() const {
+    assert(!empty());
+    return data_.front();
+  }
+
+  void replace_top(const T& value) {
+    assert(!empty());
+    data_.front() = value;
+    downheap(get_root());
+  }
+
+  void replace_top(T&& value) {
+    assert(!empty());
+    data_.front() = std::move(value);
+    downheap(get_root());
+  }
+
+  void pop() {
+    assert(!empty());
+    data_.front() = std::move(data_.back());
+    data_.pop_back();
+    if (!empty()) {
+      downheap(get_root());
+    } else {
+      reset_root_cmp_cache();
+    }
+  }
+
+  void swap(BinaryHeap &other) {
+    std::swap(cmp_, other.cmp_);
+    data_.swap(other.data_);
+    std::swap(root_cmp_cache_, other.root_cmp_cache_);
+  }
+
+  void clear() {
+    data_.clear();
+    reset_root_cmp_cache();
+  }
+
+  bool empty() const { return data_.empty(); }
+
+  size_t size() const { return data_.size(); }
+
+  void reset_root_cmp_cache() { root_cmp_cache_ = port::kMaxSizet; }
+
+ private:
+  static inline size_t get_root() { return 0; }
+  static inline size_t get_parent(size_t index) { return (index - 1) / 2; }
+  static inline size_t get_left(size_t index) { return 2 * index + 1; }
+  static inline size_t get_right(size_t index) { return 2 * index + 2; }
+
+  void upheap(size_t index) {
+    T v = std::move(data_[index]);
+    while (index > get_root()) {
+      const size_t parent = get_parent(index);
+      if (!cmp_(data_[parent], v)) {
+        break;
+      }
+      data_[index] = std::move(data_[parent]);
+      index = parent;
+    }
+    data_[index] = std::move(v);
+    reset_root_cmp_cache();
+  }
+
+  void downheap(size_t index) {
+    T v = std::move(data_[index]);
+
+    size_t picked_child = port::kMaxSizet;
+    while (1) {
+      const size_t left_child = get_left(index);
+      if (get_left(index) >= data_.size()) {
+        break;
+      }
+      const size_t right_child = left_child + 1;
+      assert(right_child == get_right(index));
+      picked_child = left_child;
+      if (index == 0 && root_cmp_cache_ < data_.size()) {
+        picked_child = root_cmp_cache_;
+      } else if (right_child < data_.size() &&
+                 cmp_(data_[left_child], data_[right_child])) {
+        picked_child = right_child;
+      }
+      if (!cmp_(v, data_[picked_child])) {
+        break;
+      }
+      data_[index] = std::move(data_[picked_child]);
+      index = picked_child;
+    }
+
+    if (index == 0) {
+      // We did not change anything in the tree except for the value
+      // of the root node, left and right child did not change, we can
+      // cache that `picked_child` is the smallest child
+      // so next time we compare againist it directly
+      root_cmp_cache_ = picked_child;
+    } else {
+      // the tree changed, reset cache
+      reset_root_cmp_cache();
+    }
+
+    data_[index] = std::move(v);
+  }
+
+  Compare cmp_;
+  autovector<T> data_;
+  // Used to reduce number of cmp_ calls in downheap()
+  size_t root_cmp_cache_ = port::kMaxSizet;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/heap_test.cc b/src/rocksdb/util/heap_test.cc
new file mode 100644
index 000000000..1f188e73b
--- /dev/null
+++ b/src/rocksdb/util/heap_test.cc
@@ -0,0 +1,139 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <gtest/gtest.h>
+
+#include <climits>
+
+#include <queue>
+#include <random>
+#include <utility>
+
+#include "util/heap.h"
+
+#ifndef GFLAGS
+const int64_t FLAGS_iters = 100000;
+#else
+#include "util/gflags_compat.h"
+DEFINE_int64(iters, 100000, "number of pseudo-random operations in each test");
+#endif  // GFLAGS
+
+/*
+ * Compares the custom heap implementation in util/heap.h against
+ * std::priority_queue on a pseudo-random sequence of operations.
+ */
+
+namespace ROCKSDB_NAMESPACE {
+
+using HeapTestValue = uint64_t;
+using Params = std::tuple<size_t, HeapTestValue, int64_t>;
+
+class HeapTest : public ::testing::TestWithParam<Params> {
+};
+
+TEST_P(HeapTest, Test) {
+  // This test performs the same pseudorandom sequence of operations on a
+  // BinaryHeap and an std::priority_queue, comparing output.  The three
+  // possible operations are insert, replace top and pop.
+  //
+  // Insert is chosen slightly more often than the others so that the size of
+  // the heap slowly grows.  Once the size heats the MAX_HEAP_SIZE limit, we
+  // disallow inserting until the heap becomes empty, testing the "draining"
+  // scenario.
+
+  const auto MAX_HEAP_SIZE = std::get<0>(GetParam());
+  const auto MAX_VALUE = std::get<1>(GetParam());
+  const auto RNG_SEED = std::get<2>(GetParam());
+
+  BinaryHeap<HeapTestValue> heap;
+  std::priority_queue<HeapTestValue> ref;
+
+  std::mt19937 rng(static_cast<unsigned int>(RNG_SEED));
+  std::uniform_int_distribution<HeapTestValue> value_dist(0, MAX_VALUE);
+  int ndrains = 0;
+  bool draining = false;     // hit max size, draining until we empty the heap
+  size_t size = 0;
+  for (int64_t i = 0; i < FLAGS_iters; ++i) {
+    if (size == 0) {
+      draining = false;
+    }
+
+    if (!draining &&
+        (size == 0 || std::bernoulli_distribution(0.4)(rng))) {
+      // insert
+      HeapTestValue val = value_dist(rng);
+      heap.push(val);
+      ref.push(val);
+      ++size;
+      if (size == MAX_HEAP_SIZE) {
+        draining = true;
+        ++ndrains;
+      }
+    } else if (std::bernoulli_distribution(0.5)(rng)) {
+      // replace top
+      HeapTestValue val = value_dist(rng);
+      heap.replace_top(val);
+      ref.pop();
+      ref.push(val);
+    } else {
+      // pop
+      assert(size > 0);
+      heap.pop();
+      ref.pop();
+      --size;
+    }
+
+    // After every operation, check that the public methods give the same
+    // results
+    assert((size == 0) == ref.empty());
+    ASSERT_EQ(size == 0, heap.empty());
+    if (size > 0) {
+      ASSERT_EQ(ref.top(), heap.top());
+    }
+  }
+
+  // Probabilities should be set up to occasionally hit the max heap size and
+  // drain it
+  assert(ndrains > 0);
+
+  heap.clear();
+  ASSERT_TRUE(heap.empty());
+}
+
+// Basic test, MAX_VALUE = 3*MAX_HEAP_SIZE (occasional duplicates)
+INSTANTIATE_TEST_CASE_P(
+  Basic, HeapTest,
+  ::testing::Values(Params(1000, 3000, 0x1b575cf05b708945))
+);
+// Mid-size heap with small values (many duplicates)
+INSTANTIATE_TEST_CASE_P(
+  SmallValues, HeapTest,
+  ::testing::Values(Params(100, 10, 0x5ae213f7bd5dccd0))
+);
+// Small heap, large value range (no duplicates)
+INSTANTIATE_TEST_CASE_P(
+  SmallHeap, HeapTest,
+  ::testing::Values(Params(10, ULLONG_MAX, 0x3e1fa8f4d01707cf))
+);
+// Two-element heap
+INSTANTIATE_TEST_CASE_P(
+  TwoElementHeap, HeapTest,
+  ::testing::Values(Params(2, 5, 0x4b5e13ea988c6abc))
+);
+// One-element heap
+INSTANTIATE_TEST_CASE_P(
+  OneElementHeap, HeapTest,
+  ::testing::Values(Params(1, 3, 0x176a1019ab0b612e))
+);
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+#ifdef GFLAGS
+  GFLAGS_NAMESPACE::ParseCommandLineFlags(&argc, &argv, true);
+#endif  // GFLAGS
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/kv_map.h b/src/rocksdb/util/kv_map.h
new file mode 100644
index 000000000..0f713ccea
--- /dev/null
+++ b/src/rocksdb/util/kv_map.h
@@ -0,0 +1,33 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+#pragma once
+
+#include <map>
+#include <string>
+
+#include "rocksdb/comparator.h"
+#include "rocksdb/slice.h"
+#include "util/coding.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace stl_wrappers {
+
+struct LessOfComparator {
+  explicit LessOfComparator(const Comparator* c = BytewiseComparator())
+      : cmp(c) {}
+
+  bool operator()(const std::string& a, const std::string& b) const {
+    return cmp->Compare(Slice(a), Slice(b)) < 0;
+  }
+  bool operator()(const Slice& a, const Slice& b) const {
+    return cmp->Compare(a, b) < 0;
+  }
+
+  const Comparator* cmp;
+};
+
+typedef std::map<std::string, std::string, LessOfComparator> KVMap;
+}
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/log_write_bench.cc b/src/rocksdb/util/log_write_bench.cc
new file mode 100644
index 000000000..60798babf
--- /dev/null
+++ b/src/rocksdb/util/log_write_bench.cc
@@ -0,0 +1,86 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#ifndef GFLAGS
+#include <cstdio>
+int main() {
+  fprintf(stderr, "Please install gflags to run rocksdb tools\n");
+  return 1;
+}
+#else
+
+#include "file/writable_file_writer.h"
+#include "monitoring/histogram.h"
+#include "rocksdb/env.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/gflags_compat.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+using GFLAGS_NAMESPACE::SetUsageMessage;
+
+// A simple benchmark to simulate transactional logs
+
+DEFINE_int32(num_records, 6000, "Number of records.");
+DEFINE_int32(record_size, 249, "Size of each record.");
+DEFINE_int32(record_interval, 10000, "Interval between records (microSec)");
+DEFINE_int32(bytes_per_sync, 0, "bytes_per_sync parameter in EnvOptions");
+DEFINE_bool(enable_sync, false, "sync after each write.");
+
+namespace ROCKSDB_NAMESPACE {
+void RunBenchmark() {
+  std::string file_name = test::PerThreadDBPath("log_write_benchmark.log");
+  DBOptions options;
+  Env* env = Env::Default();
+  EnvOptions env_options = env->OptimizeForLogWrite(EnvOptions(), options);
+  env_options.bytes_per_sync = FLAGS_bytes_per_sync;
+  std::unique_ptr<WritableFile> file;
+  env->NewWritableFile(file_name, &file, env_options);
+  std::unique_ptr<WritableFileWriter> writer;
+  writer.reset(new WritableFileWriter(std::move(file), file_name, env_options,
+                                      env, nullptr /* stats */,
+                                      options.listeners));
+
+  std::string record;
+  record.assign(FLAGS_record_size, 'X');
+
+  HistogramImpl hist;
+
+  uint64_t start_time = env->NowMicros();
+  for (int i = 0; i < FLAGS_num_records; i++) {
+    uint64_t start_nanos = env->NowNanos();
+    writer->Append(record);
+    writer->Flush();
+    if (FLAGS_enable_sync) {
+      writer->Sync(false);
+    }
+    hist.Add(env->NowNanos() - start_nanos);
+
+    if (i % 1000 == 1) {
+      fprintf(stderr, "Wrote %d records...\n", i);
+    }
+
+    int time_to_sleep =
+        (i + 1) * FLAGS_record_interval - (env->NowMicros() - start_time);
+    if (time_to_sleep > 0) {
+      env->SleepForMicroseconds(time_to_sleep);
+    }
+  }
+
+  fprintf(stderr, "Distribution of latency of append+flush: \n%s",
+          hist.ToString().c_str());
+}
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
+                  " [OPTIONS]...");
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  ROCKSDB_NAMESPACE::RunBenchmark();
+  return 0;
+}
+
+#endif  // GFLAGS
diff --git a/src/rocksdb/util/murmurhash.cc b/src/rocksdb/util/murmurhash.cc
new file mode 100644
index 000000000..3b759c5e6
--- /dev/null
+++ b/src/rocksdb/util/murmurhash.cc
@@ -0,0 +1,191 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+/*
+  Murmurhash from http://sites.google.com/site/murmurhash/
+
+  All code is released to the public domain. For business purposes, Murmurhash
+  is under the MIT license.
+*/
+#include "murmurhash.h"
+#include "util/util.h"
+
+#if defined(__x86_64__)
+
+// -------------------------------------------------------------------
+//
+// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment
+// and endian-ness issues if used across multiple platforms.
+//
+// 64-bit hash for 64-bit platforms
+
+#ifdef ROCKSDB_UBSAN_RUN
+#if defined(__clang__)
+__attribute__((__no_sanitize__("alignment")))
+#elif defined(__GNUC__)
+__attribute__((__no_sanitize_undefined__))
+#endif
+#endif
+uint64_t MurmurHash64A ( const void * key, int len, unsigned int seed )
+{
+    const uint64_t m = 0xc6a4a7935bd1e995;
+    const int r = 47;
+
+    uint64_t h = seed ^ (len * m);
+
+    const uint64_t * data = (const uint64_t *)key;
+    const uint64_t * end = data + (len/8);
+
+    while(data != end)
+    {
+        uint64_t k = *data++;
+
+        k *= m;
+        k ^= k >> r;
+        k *= m;
+
+        h ^= k;
+        h *= m;
+    }
+
+    const unsigned char * data2 = (const unsigned char*)data;
+
+    switch(len & 7)
+    {
+    case 7: h ^= ((uint64_t)data2[6]) << 48; FALLTHROUGH_INTENDED;
+    case 6: h ^= ((uint64_t)data2[5]) << 40; FALLTHROUGH_INTENDED;
+    case 5: h ^= ((uint64_t)data2[4]) << 32; FALLTHROUGH_INTENDED;
+    case 4: h ^= ((uint64_t)data2[3]) << 24; FALLTHROUGH_INTENDED;
+    case 3: h ^= ((uint64_t)data2[2]) << 16; FALLTHROUGH_INTENDED;
+    case 2: h ^= ((uint64_t)data2[1]) << 8;  FALLTHROUGH_INTENDED;
+    case 1: h ^= ((uint64_t)data2[0]);
+        h *= m;
+    };
+
+    h ^= h >> r;
+    h *= m;
+    h ^= h >> r;
+
+    return h;
+}
+
+#elif defined(__i386__)
+
+// -------------------------------------------------------------------
+//
+// Note - This code makes a few assumptions about how your machine behaves -
+//
+// 1. We can read a 4-byte value from any address without crashing
+// 2. sizeof(int) == 4
+//
+// And it has a few limitations -
+//
+// 1. It will not work incrementally.
+// 2. It will not produce the same results on little-endian and big-endian
+//    machines.
+
+unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed )
+{
+    // 'm' and 'r' are mixing constants generated offline.
+    // They're not really 'magic', they just happen to work well.
+
+    const unsigned int m = 0x5bd1e995;
+    const int r = 24;
+
+    // Initialize the hash to a 'random' value
+
+    unsigned int h = seed ^ len;
+
+    // Mix 4 bytes at a time into the hash
+
+    const unsigned char * data = (const unsigned char *)key;
+
+    while(len >= 4)
+    {
+        unsigned int k = *(unsigned int *)data;
+
+        k *= m;
+        k ^= k >> r;
+        k *= m;
+
+        h *= m;
+        h ^= k;
+
+        data += 4;
+        len -= 4;
+    }
+
+    // Handle the last few bytes of the input array
+
+    switch(len)
+    {
+    case 3: h ^= data[2] << 16; FALLTHROUGH_INTENDED;
+    case 2: h ^= data[1] << 8;  FALLTHROUGH_INTENDED;
+    case 1: h ^= data[0];
+        h *= m;
+    };
+
+    // Do a few final mixes of the hash to ensure the last few
+    // bytes are well-incorporated.
+
+    h ^= h >> 13;
+    h *= m;
+    h ^= h >> 15;
+
+    return h;
+}
+
+#else
+
+// -------------------------------------------------------------------
+//
+// Same as MurmurHash2, but endian- and alignment-neutral.
+// Half the speed though, alas.
+
+unsigned int MurmurHashNeutral2 ( const void * key, int len, unsigned int seed )
+{
+    const unsigned int m = 0x5bd1e995;
+    const int r = 24;
+
+    unsigned int h = seed ^ len;
+
+    const unsigned char * data = (const unsigned char *)key;
+
+    while(len >= 4)
+    {
+        unsigned int k;
+
+        k  = data[0];
+        k |= data[1] << 8;
+        k |= data[2] << 16;
+        k |= data[3] << 24;
+
+        k *= m;
+        k ^= k >> r;
+        k *= m;
+
+        h *= m;
+        h ^= k;
+
+        data += 4;
+        len -= 4;
+    }
+
+    switch(len)
+    {
+    case 3: h ^= data[2] << 16; FALLTHROUGH_INTENDED;
+    case 2: h ^= data[1] << 8;  FALLTHROUGH_INTENDED;
+    case 1: h ^= data[0];
+        h *= m;
+    };
+
+    h ^= h >> 13;
+    h *= m;
+    h ^= h >> 15;
+
+    return h;
+}
+
+#endif
diff --git a/src/rocksdb/util/murmurhash.h b/src/rocksdb/util/murmurhash.h
new file mode 100644
index 000000000..1dbb57398
--- /dev/null
+++ b/src/rocksdb/util/murmurhash.h
@@ -0,0 +1,42 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+/*
+  Murmurhash from http://sites.google.com/site/murmurhash/
+
+  All code is released to the public domain. For business purposes, Murmurhash
+  is under the MIT license.
+*/
+#pragma once
+#include <stdint.h>
+#include "rocksdb/slice.h"
+
+#if defined(__x86_64__)
+#define MURMUR_HASH MurmurHash64A
+uint64_t MurmurHash64A ( const void * key, int len, unsigned int seed );
+#define MurmurHash MurmurHash64A
+typedef uint64_t murmur_t;
+
+#elif defined(__i386__)
+#define MURMUR_HASH MurmurHash2
+unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed );
+#define MurmurHash MurmurHash2
+typedef unsigned int murmur_t;
+
+#else
+#define MURMUR_HASH MurmurHashNeutral2
+unsigned int MurmurHashNeutral2 ( const void * key, int len, unsigned int seed );
+#define MurmurHash MurmurHashNeutral2
+typedef unsigned int murmur_t;
+#endif
+
+// Allow slice to be hashable by murmur hash.
+namespace ROCKSDB_NAMESPACE {
+struct murmur_hash {
+  size_t operator()(const Slice& slice) const {
+    return MurmurHash(slice.data(), static_cast<int>(slice.size()), 0);
+  }
+};
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/mutexlock.h b/src/rocksdb/util/mutexlock.h
new file mode 100644
index 000000000..91ba4fda7
--- /dev/null
+++ b/src/rocksdb/util/mutexlock.h
@@ -0,0 +1,135 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+#include <assert.h>
+#include <atomic>
+#include <mutex>
+#include <thread>
+#include "port/port.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Helper class that locks a mutex on construction and unlocks the mutex when
+// the destructor of the MutexLock object is invoked.
+//
+// Typical usage:
+//
+//   void MyClass::MyMethod() {
+//     MutexLock l(&mu_);       // mu_ is an instance variable
+//     ... some complex code, possibly with multiple return paths ...
+//   }
+
+class MutexLock {
+ public:
+  explicit MutexLock(port::Mutex *mu) : mu_(mu) {
+    this->mu_->Lock();
+  }
+  // No copying allowed
+  MutexLock(const MutexLock &) = delete;
+  void operator=(const MutexLock &) = delete;
+
+  ~MutexLock() { this->mu_->Unlock(); }
+
+ private:
+  port::Mutex *const mu_;
+};
+
+//
+// Acquire a ReadLock on the specified RWMutex.
+// The Lock will be automatically released then the
+// object goes out of scope.
+//
+class ReadLock {
+ public:
+  explicit ReadLock(port::RWMutex *mu) : mu_(mu) {
+    this->mu_->ReadLock();
+  }
+  // No copying allowed
+  ReadLock(const ReadLock &) = delete;
+  void operator=(const ReadLock &) = delete;
+
+  ~ReadLock() { this->mu_->ReadUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// Automatically unlock a locked mutex when the object is destroyed
+//
+class ReadUnlock {
+ public:
+  explicit ReadUnlock(port::RWMutex *mu) : mu_(mu) { mu->AssertHeld(); }
+  // No copying allowed
+  ReadUnlock(const ReadUnlock &) = delete;
+  ReadUnlock &operator=(const ReadUnlock &) = delete;
+
+  ~ReadUnlock() { mu_->ReadUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// Acquire a WriteLock on the specified RWMutex.
+// The Lock will be automatically released then the
+// object goes out of scope.
+//
+class WriteLock {
+ public:
+  explicit WriteLock(port::RWMutex *mu) : mu_(mu) {
+    this->mu_->WriteLock();
+  }
+  // No copying allowed
+  WriteLock(const WriteLock &) = delete;
+  void operator=(const WriteLock &) = delete;
+
+  ~WriteLock() { this->mu_->WriteUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// SpinMutex has very low overhead for low-contention cases.  Method names
+// are chosen so you can use std::unique_lock or std::lock_guard with it.
+//
+class SpinMutex {
+ public:
+  SpinMutex() : locked_(false) {}
+
+  bool try_lock() {
+    auto currently_locked = locked_.load(std::memory_order_relaxed);
+    return !currently_locked &&
+           locked_.compare_exchange_weak(currently_locked, true,
+                                         std::memory_order_acquire,
+                                         std::memory_order_relaxed);
+  }
+
+  void lock() {
+    for (size_t tries = 0;; ++tries) {
+      if (try_lock()) {
+        // success
+        break;
+      }
+      port::AsmVolatilePause();
+      if (tries > 100) {
+        std::this_thread::yield();
+      }
+    }
+  }
+
+  void unlock() { locked_.store(false, std::memory_order_release); }
+
+ private:
+  std::atomic<bool> locked_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/ppc-opcode.h b/src/rocksdb/util/ppc-opcode.h
new file mode 100644
index 000000000..5cc5af0e3
--- /dev/null
+++ b/src/rocksdb/util/ppc-opcode.h
@@ -0,0 +1,27 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  Copyright (c) 2017 International Business Machines Corp.
+//  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#define __PPC_RA(a) (((a)&0x1f) << 16)
+#define __PPC_RB(b) (((b)&0x1f) << 11)
+#define __PPC_XA(a) ((((a)&0x1f) << 16) | (((a)&0x20) >> 3))
+#define __PPC_XB(b) ((((b)&0x1f) << 11) | (((b)&0x20) >> 4))
+#define __PPC_XS(s) ((((s)&0x1f) << 21) | (((s)&0x20) >> 5))
+#define __PPC_XT(s) __PPC_XS(s)
+#define VSX_XX3(t, a, b) (__PPC_XT(t) | __PPC_XA(a) | __PPC_XB(b))
+#define VSX_XX1(s, a, b) (__PPC_XS(s) | __PPC_RA(a) | __PPC_RB(b))
+
+#define PPC_INST_VPMSUMW 0x10000488
+#define PPC_INST_VPMSUMD 0x100004c8
+#define PPC_INST_MFVSRD 0x7c000066
+#define PPC_INST_MTVSRD 0x7c000166
+
+#define VPMSUMW(t, a, b) .long PPC_INST_VPMSUMW | VSX_XX3((t), a, b)
+#define VPMSUMD(t, a, b) .long PPC_INST_VPMSUMD | VSX_XX3((t), a, b)
+#define MFVRD(a, t) .long PPC_INST_MFVSRD | VSX_XX1((t) + 32, a, 0)
+#define MTVRD(t, a) .long PPC_INST_MTVSRD | VSX_XX1((t) + 32, a, 0)
diff --git a/src/rocksdb/util/random.cc b/src/rocksdb/util/random.cc
new file mode 100644
index 000000000..38c36defd
--- /dev/null
+++ b/src/rocksdb/util/random.cc
@@ -0,0 +1,38 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+
+#include "util/random.h"
+
+#include <stdint.h>
+#include <string.h>
+#include <thread>
+#include <utility>
+
+#include "port/likely.h"
+#include "util/thread_local.h"
+
+#ifdef ROCKSDB_SUPPORT_THREAD_LOCAL
+#define STORAGE_DECL static __thread
+#else
+#define STORAGE_DECL static
+#endif
+
+namespace ROCKSDB_NAMESPACE {
+
+Random* Random::GetTLSInstance() {
+  STORAGE_DECL Random* tls_instance;
+  STORAGE_DECL std::aligned_storage<sizeof(Random)>::type tls_instance_bytes;
+
+  auto rv = tls_instance;
+  if (UNLIKELY(rv == nullptr)) {
+    size_t seed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    rv = new (&tls_instance_bytes) Random((uint32_t)seed);
+    tls_instance = rv;
+  }
+  return rv;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/random.h b/src/rocksdb/util/random.h
new file mode 100644
index 000000000..f97b2126f
--- /dev/null
+++ b/src/rocksdb/util/random.h
@@ -0,0 +1,166 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+#include <stdint.h>
+#include <random>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// A very simple random number generator.  Not especially good at
+// generating truly random bits, but good enough for our needs in this
+// package.
+class Random {
+ private:
+  enum : uint32_t {
+    M = 2147483647L  // 2^31-1
+  };
+  enum : uint64_t {
+    A = 16807  // bits 14, 8, 7, 5, 2, 1, 0
+  };
+
+  uint32_t seed_;
+
+  static uint32_t GoodSeed(uint32_t s) { return (s & M) != 0 ? (s & M) : 1; }
+
+ public:
+  // This is the largest value that can be returned from Next()
+  enum : uint32_t { kMaxNext = M };
+
+  explicit Random(uint32_t s) : seed_(GoodSeed(s)) {}
+
+  void Reset(uint32_t s) { seed_ = GoodSeed(s); }
+
+  uint32_t Next() {
+    // We are computing
+    //       seed_ = (seed_ * A) % M,    where M = 2^31-1
+    //
+    // seed_ must not be zero or M, or else all subsequent computed values
+    // will be zero or M respectively.  For all other values, seed_ will end
+    // up cycling through every number in [1,M-1]
+    uint64_t product = seed_ * A;
+
+    // Compute (product % M) using the fact that ((x << 31) % M) == x.
+    seed_ = static_cast<uint32_t>((product >> 31) + (product & M));
+    // The first reduction may overflow by 1 bit, so we may need to
+    // repeat.  mod == M is not possible; using > allows the faster
+    // sign-bit-based test.
+    if (seed_ > M) {
+      seed_ -= M;
+    }
+    return seed_;
+  }
+
+  // Returns a uniformly distributed value in the range [0..n-1]
+  // REQUIRES: n > 0
+  uint32_t Uniform(int n) { return Next() % n; }
+
+  // Randomly returns true ~"1/n" of the time, and false otherwise.
+  // REQUIRES: n > 0
+  bool OneIn(int n) { return Uniform(n) == 0; }
+
+  // "Optional" one-in-n, where 0 or negative always returns false
+  // (may or may not consume a random value)
+  bool OneInOpt(int n) { return n > 0 && OneIn(n); }
+
+  // Returns random bool that is true for the given percentage of
+  // calls on average. Zero or less is always false and 100 or more
+  // is always true (may or may not consume a random value)
+  bool PercentTrue(int percentage) {
+    return static_cast<int>(Uniform(100)) < percentage;
+  }
+
+  // Skewed: pick "base" uniformly from range [0,max_log] and then
+  // return "base" random bits.  The effect is to pick a number in the
+  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
+  uint32_t Skewed(int max_log) {
+    return Uniform(1 << Uniform(max_log + 1));
+  }
+
+  // Returns a Random instance for use by the current thread without
+  // additional locking
+  static Random* GetTLSInstance();
+};
+
+// A good 32-bit random number generator based on std::mt19937.
+// This exists in part to avoid compiler variance in warning about coercing
+// uint_fast32_t from mt19937 to uint32_t.
+class Random32 {
+ private:
+  std::mt19937 generator_;
+
+ public:
+  explicit Random32(uint32_t s) : generator_(s) {}
+
+  // Generates the next random number
+  uint32_t Next() { return static_cast<uint32_t>(generator_()); }
+
+  // Returns a uniformly distributed value in the range [0..n-1]
+  // REQUIRES: n > 0
+  uint32_t Uniform(uint32_t n) {
+    return static_cast<uint32_t>(
+        std::uniform_int_distribution<std::mt19937::result_type>(
+            0, n - 1)(generator_));
+  }
+
+  // Returns an *almost* uniformly distributed value in the range [0..n-1].
+  // Much faster than Uniform().
+  // REQUIRES: n > 0
+  uint32_t Uniformish(uint32_t n) {
+    // fastrange (without the header)
+    return static_cast<uint32_t>((uint64_t(generator_()) * uint64_t(n)) >> 32);
+  }
+
+  // Randomly returns true ~"1/n" of the time, and false otherwise.
+  // REQUIRES: n > 0
+  bool OneIn(uint32_t n) { return Uniform(n) == 0; }
+
+  // Skewed: pick "base" uniformly from range [0,max_log] and then
+  // return "base" random bits.  The effect is to pick a number in the
+  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
+  uint32_t Skewed(int max_log) {
+    return Uniform(uint32_t{1} << Uniform(max_log + 1));
+  }
+
+  // Reset the seed of the generator to the given value
+  void Seed(uint32_t new_seed) { generator_.seed(new_seed); }
+};
+
+// A good 64-bit random number generator based on std::mt19937_64
+class Random64 {
+ private:
+  std::mt19937_64 generator_;
+
+ public:
+  explicit Random64(uint64_t s) : generator_(s) { }
+
+  // Generates the next random number
+  uint64_t Next() { return generator_(); }
+
+  // Returns a uniformly distributed value in the range [0..n-1]
+  // REQUIRES: n > 0
+  uint64_t Uniform(uint64_t n) {
+    return std::uniform_int_distribution<uint64_t>(0, n - 1)(generator_);
+  }
+
+  // Randomly returns true ~"1/n" of the time, and false otherwise.
+  // REQUIRES: n > 0
+  bool OneIn(uint64_t n) { return Uniform(n) == 0; }
+
+  // Skewed: pick "base" uniformly from range [0,max_log] and then
+  // return "base" random bits.  The effect is to pick a number in the
+  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
+  uint64_t Skewed(int max_log) {
+    return Uniform(uint64_t(1) << Uniform(max_log + 1));
+  }
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/random_test.cc b/src/rocksdb/util/random_test.cc
new file mode 100644
index 000000000..ad5208193
--- /dev/null
+++ b/src/rocksdb/util/random_test.cc
@@ -0,0 +1,105 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstring>
+#include <vector>
+
+#include "test_util/testharness.h"
+#include "util/random.h"
+
+using ROCKSDB_NAMESPACE::Random;
+
+TEST(RandomTest, Uniform) {
+  const int average = 20;
+  for (uint32_t seed : {0, 1, 2, 37, 4096}) {
+    Random r(seed);
+    for (int range : {1, 2, 8, 12, 100}) {
+      std::vector<int> counts(range, 0);
+
+      for (int i = 0; i < range * average; ++i) {
+        ++counts.at(r.Uniform(range));
+      }
+      int max_variance = static_cast<int>(std::sqrt(range) * 2 + 4);
+      for (int i = 0; i < range; ++i) {
+        EXPECT_GE(counts[i], std::max(1, average - max_variance));
+        EXPECT_LE(counts[i], average + max_variance + 1);
+      }
+    }
+  }
+}
+
+TEST(RandomTest, OneIn) {
+  Random r(42);
+  for (int range : {1, 2, 8, 12, 100, 1234}) {
+    const int average = 100;
+    int count = 0;
+    for (int i = 0; i < average * range; ++i) {
+      if (r.OneIn(range)) {
+        ++count;
+      }
+    }
+    if (range == 1) {
+      EXPECT_EQ(count, average);
+    } else {
+      int max_variance = static_cast<int>(std::sqrt(average) * 1.5);
+      EXPECT_GE(count, average - max_variance);
+      EXPECT_LE(count, average + max_variance);
+    }
+  }
+}
+
+TEST(RandomTest, OneInOpt) {
+  Random r(42);
+  for (int range : {-12, 0, 1, 2, 8, 12, 100, 1234}) {
+    const int average = 100;
+    int count = 0;
+    for (int i = 0; i < average * range; ++i) {
+      if (r.OneInOpt(range)) {
+        ++count;
+      }
+    }
+    if (range < 1) {
+      EXPECT_EQ(count, 0);
+    } else if (range == 1) {
+      EXPECT_EQ(count, average);
+    } else {
+      int max_variance = static_cast<int>(std::sqrt(average) * 1.5);
+      EXPECT_GE(count, average - max_variance);
+      EXPECT_LE(count, average + max_variance);
+    }
+  }
+}
+
+TEST(RandomTest, PercentTrue) {
+  Random r(42);
+  for (int pct : {-12, 0, 1, 2, 10, 50, 90, 98, 99, 100, 1234}) {
+    const int samples = 10000;
+
+    int count = 0;
+    for (int i = 0; i < samples; ++i) {
+      if (r.PercentTrue(pct)) {
+        ++count;
+      }
+    }
+    if (pct <= 0) {
+      EXPECT_EQ(count, 0);
+    } else if (pct >= 100) {
+      EXPECT_EQ(count, samples);
+    } else {
+      int est = (count * 100 + (samples / 2)) / samples;
+      EXPECT_EQ(est, pct);
+    }
+  }
+}
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/rate_limiter.cc b/src/rocksdb/util/rate_limiter.cc
new file mode 100644
index 000000000..b1eefe620
--- /dev/null
+++ b/src/rocksdb/util/rate_limiter.cc
@@ -0,0 +1,339 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/rate_limiter.h"
+#include "monitoring/statistics.h"
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "test_util/sync_point.h"
+#include "util/aligned_buffer.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+size_t RateLimiter::RequestToken(size_t bytes, size_t alignment,
+                                 Env::IOPriority io_priority, Statistics* stats,
+                                 RateLimiter::OpType op_type) {
+  if (io_priority < Env::IO_TOTAL && IsRateLimited(op_type)) {
+    bytes = std::min(bytes, static_cast<size_t>(GetSingleBurstBytes()));
+
+    if (alignment > 0) {
+      // Here we may actually require more than burst and block
+      // but we can not write less than one page at a time on direct I/O
+      // thus we may want not to use ratelimiter
+      bytes = std::max(alignment, TruncateToPageBoundary(alignment, bytes));
+    }
+    Request(bytes, io_priority, stats, op_type);
+  }
+  return bytes;
+}
+
+// Pending request
+struct GenericRateLimiter::Req {
+  explicit Req(int64_t _bytes, port::Mutex* _mu)
+      : request_bytes(_bytes), bytes(_bytes), cv(_mu), granted(false) {}
+  int64_t request_bytes;
+  int64_t bytes;
+  port::CondVar cv;
+  bool granted;
+};
+
+GenericRateLimiter::GenericRateLimiter(int64_t rate_bytes_per_sec,
+                                       int64_t refill_period_us,
+                                       int32_t fairness, RateLimiter::Mode mode,
+                                       Env* env, bool auto_tuned)
+    : RateLimiter(mode),
+      refill_period_us_(refill_period_us),
+      rate_bytes_per_sec_(auto_tuned ? rate_bytes_per_sec / 2
+                                     : rate_bytes_per_sec),
+      refill_bytes_per_period_(
+          CalculateRefillBytesPerPeriod(rate_bytes_per_sec_)),
+      env_(env),
+      stop_(false),
+      exit_cv_(&request_mutex_),
+      requests_to_wait_(0),
+      available_bytes_(0),
+      next_refill_us_(NowMicrosMonotonic(env_)),
+      fairness_(fairness > 100 ? 100 : fairness),
+      rnd_((uint32_t)time(nullptr)),
+      leader_(nullptr),
+      auto_tuned_(auto_tuned),
+      num_drains_(0),
+      prev_num_drains_(0),
+      max_bytes_per_sec_(rate_bytes_per_sec),
+      tuned_time_(NowMicrosMonotonic(env_)) {
+  total_requests_[0] = 0;
+  total_requests_[1] = 0;
+  total_bytes_through_[0] = 0;
+  total_bytes_through_[1] = 0;
+}
+
+GenericRateLimiter::~GenericRateLimiter() {
+  MutexLock g(&request_mutex_);
+  stop_ = true;
+  requests_to_wait_ = static_cast<int32_t>(queue_[Env::IO_LOW].size() +
+                                           queue_[Env::IO_HIGH].size());
+  for (auto& r : queue_[Env::IO_HIGH]) {
+    r->cv.Signal();
+  }
+  for (auto& r : queue_[Env::IO_LOW]) {
+    r->cv.Signal();
+  }
+  while (requests_to_wait_ > 0) {
+    exit_cv_.Wait();
+  }
+}
+
+// This API allows user to dynamically change rate limiter's bytes per second.
+void GenericRateLimiter::SetBytesPerSecond(int64_t bytes_per_second) {
+  assert(bytes_per_second > 0);
+  rate_bytes_per_sec_ = bytes_per_second;
+  refill_bytes_per_period_.store(
+      CalculateRefillBytesPerPeriod(bytes_per_second),
+      std::memory_order_relaxed);
+}
+
+void GenericRateLimiter::Request(int64_t bytes, const Env::IOPriority pri,
+                                 Statistics* stats) {
+  assert(bytes <= refill_bytes_per_period_.load(std::memory_order_relaxed));
+  TEST_SYNC_POINT("GenericRateLimiter::Request");
+  TEST_SYNC_POINT_CALLBACK("GenericRateLimiter::Request:1",
+                           &rate_bytes_per_sec_);
+  MutexLock g(&request_mutex_);
+
+  if (auto_tuned_) {
+    static const int kRefillsPerTune = 100;
+    std::chrono::microseconds now(NowMicrosMonotonic(env_));
+    if (now - tuned_time_ >=
+        kRefillsPerTune * std::chrono::microseconds(refill_period_us_)) {
+      Tune();
+    }
+  }
+
+  if (stop_) {
+    return;
+  }
+
+  ++total_requests_[pri];
+
+  if (available_bytes_ >= bytes) {
+    // Refill thread assigns quota and notifies requests waiting on
+    // the queue under mutex. So if we get here, that means nobody
+    // is waiting?
+    available_bytes_ -= bytes;
+    total_bytes_through_[pri] += bytes;
+    return;
+  }
+
+  // Request cannot be satisfied at this moment, enqueue
+  Req r(bytes, &request_mutex_);
+  queue_[pri].push_back(&r);
+
+  do {
+    bool timedout = false;
+    // Leader election, candidates can be:
+    // (1) a new incoming request,
+    // (2) a previous leader, whose quota has not been not assigned yet due
+    //     to lower priority
+    // (3) a previous waiter at the front of queue, who got notified by
+    //     previous leader
+    if (leader_ == nullptr &&
+        ((!queue_[Env::IO_HIGH].empty() &&
+            &r == queue_[Env::IO_HIGH].front()) ||
+         (!queue_[Env::IO_LOW].empty() &&
+            &r == queue_[Env::IO_LOW].front()))) {
+      leader_ = &r;
+      int64_t delta = next_refill_us_ - NowMicrosMonotonic(env_);
+      delta = delta > 0 ? delta : 0;
+      if (delta == 0) {
+        timedout = true;
+      } else {
+        int64_t wait_until = env_->NowMicros() + delta;
+        RecordTick(stats, NUMBER_RATE_LIMITER_DRAINS);
+        ++num_drains_;
+        timedout = r.cv.TimedWait(wait_until);
+      }
+    } else {
+      // Not at the front of queue or an leader has already been elected
+      r.cv.Wait();
+    }
+
+    // request_mutex_ is held from now on
+    if (stop_) {
+      --requests_to_wait_;
+      exit_cv_.Signal();
+      return;
+    }
+
+    // Make sure the waken up request is always the header of its queue
+    assert(r.granted ||
+           (!queue_[Env::IO_HIGH].empty() &&
+            &r == queue_[Env::IO_HIGH].front()) ||
+           (!queue_[Env::IO_LOW].empty() &&
+            &r == queue_[Env::IO_LOW].front()));
+    assert(leader_ == nullptr ||
+           (!queue_[Env::IO_HIGH].empty() &&
+            leader_ == queue_[Env::IO_HIGH].front()) ||
+           (!queue_[Env::IO_LOW].empty() &&
+            leader_ == queue_[Env::IO_LOW].front()));
+
+    if (leader_ == &r) {
+      // Waken up from TimedWait()
+      if (timedout) {
+        // Time to do refill!
+        Refill();
+
+        // Re-elect a new leader regardless. This is to simplify the
+        // election handling.
+        leader_ = nullptr;
+
+        // Notify the header of queue if current leader is going away
+        if (r.granted) {
+          // Current leader already got granted with quota. Notify header
+          // of waiting queue to participate next round of election.
+          assert((queue_[Env::IO_HIGH].empty() ||
+                    &r != queue_[Env::IO_HIGH].front()) &&
+                 (queue_[Env::IO_LOW].empty() ||
+                    &r != queue_[Env::IO_LOW].front()));
+          if (!queue_[Env::IO_HIGH].empty()) {
+            queue_[Env::IO_HIGH].front()->cv.Signal();
+          } else if (!queue_[Env::IO_LOW].empty()) {
+            queue_[Env::IO_LOW].front()->cv.Signal();
+          }
+          // Done
+          break;
+        }
+      } else {
+        // Spontaneous wake up, need to continue to wait
+        assert(!r.granted);
+        leader_ = nullptr;
+      }
+    } else {
+      // Waken up by previous leader:
+      // (1) if requested quota is granted, it is done.
+      // (2) if requested quota is not granted, this means current thread
+      // was picked as a new leader candidate (previous leader got quota).
+      // It needs to participate leader election because a new request may
+      // come in before this thread gets waken up. So it may actually need
+      // to do Wait() again.
+      assert(!timedout);
+    }
+  } while (!r.granted);
+}
+
+void GenericRateLimiter::Refill() {
+  TEST_SYNC_POINT("GenericRateLimiter::Refill");
+  next_refill_us_ = NowMicrosMonotonic(env_) + refill_period_us_;
+  // Carry over the left over quota from the last period
+  auto refill_bytes_per_period =
+      refill_bytes_per_period_.load(std::memory_order_relaxed);
+  if (available_bytes_ < refill_bytes_per_period) {
+    available_bytes_ += refill_bytes_per_period;
+  }
+
+  int use_low_pri_first = rnd_.OneIn(fairness_) ? 0 : 1;
+  for (int q = 0; q < 2; ++q) {
+    auto use_pri = (use_low_pri_first == q) ? Env::IO_LOW : Env::IO_HIGH;
+    auto* queue = &queue_[use_pri];
+    while (!queue->empty()) {
+      auto* next_req = queue->front();
+      if (available_bytes_ < next_req->request_bytes) {
+        // avoid starvation
+        next_req->request_bytes -= available_bytes_;
+        available_bytes_ = 0;
+        break;
+      }
+      available_bytes_ -= next_req->request_bytes;
+      next_req->request_bytes = 0;
+      total_bytes_through_[use_pri] += next_req->bytes;
+      queue->pop_front();
+
+      next_req->granted = true;
+      if (next_req != leader_) {
+        // Quota granted, signal the thread
+        next_req->cv.Signal();
+      }
+    }
+  }
+}
+
+int64_t GenericRateLimiter::CalculateRefillBytesPerPeriod(
+    int64_t rate_bytes_per_sec) {
+  if (port::kMaxInt64 / rate_bytes_per_sec < refill_period_us_) {
+    // Avoid unexpected result in the overflow case. The result now is still
+    // inaccurate but is a number that is large enough.
+    return port::kMaxInt64 / 1000000;
+  } else {
+    return std::max(kMinRefillBytesPerPeriod,
+                    rate_bytes_per_sec * refill_period_us_ / 1000000);
+  }
+}
+
+Status GenericRateLimiter::Tune() {
+  const int kLowWatermarkPct = 50;
+  const int kHighWatermarkPct = 90;
+  const int kAdjustFactorPct = 5;
+  // computed rate limit will be in
+  // `[max_bytes_per_sec_ / kAllowedRangeFactor, max_bytes_per_sec_]`.
+  const int kAllowedRangeFactor = 20;
+
+  std::chrono::microseconds prev_tuned_time = tuned_time_;
+  tuned_time_ = std::chrono::microseconds(NowMicrosMonotonic(env_));
+
+  int64_t elapsed_intervals = (tuned_time_ - prev_tuned_time +
+                               std::chrono::microseconds(refill_period_us_) -
+                               std::chrono::microseconds(1)) /
+                              std::chrono::microseconds(refill_period_us_);
+  // We tune every kRefillsPerTune intervals, so the overflow and division-by-
+  // zero conditions should never happen.
+  assert(num_drains_ - prev_num_drains_ <= port::kMaxInt64 / 100);
+  assert(elapsed_intervals > 0);
+  int64_t drained_pct =
+      (num_drains_ - prev_num_drains_) * 100 / elapsed_intervals;
+
+  int64_t prev_bytes_per_sec = GetBytesPerSecond();
+  int64_t new_bytes_per_sec;
+  if (drained_pct == 0) {
+    new_bytes_per_sec = max_bytes_per_sec_ / kAllowedRangeFactor;
+  } else if (drained_pct < kLowWatermarkPct) {
+    // sanitize to prevent overflow
+    int64_t sanitized_prev_bytes_per_sec =
+        std::min(prev_bytes_per_sec, port::kMaxInt64 / 100);
+    new_bytes_per_sec =
+        std::max(max_bytes_per_sec_ / kAllowedRangeFactor,
+                 sanitized_prev_bytes_per_sec * 100 / (100 + kAdjustFactorPct));
+  } else if (drained_pct > kHighWatermarkPct) {
+    // sanitize to prevent overflow
+    int64_t sanitized_prev_bytes_per_sec = std::min(
+        prev_bytes_per_sec, port::kMaxInt64 / (100 + kAdjustFactorPct));
+    new_bytes_per_sec =
+        std::min(max_bytes_per_sec_,
+                 sanitized_prev_bytes_per_sec * (100 + kAdjustFactorPct) / 100);
+  } else {
+    new_bytes_per_sec = prev_bytes_per_sec;
+  }
+  if (new_bytes_per_sec != prev_bytes_per_sec) {
+    SetBytesPerSecond(new_bytes_per_sec);
+  }
+  num_drains_ = prev_num_drains_;
+  return Status::OK();
+}
+
+RateLimiter* NewGenericRateLimiter(
+    int64_t rate_bytes_per_sec, int64_t refill_period_us /* = 100 * 1000 */,
+    int32_t fairness /* = 10 */,
+    RateLimiter::Mode mode /* = RateLimiter::Mode::kWritesOnly */,
+    bool auto_tuned /* = false */) {
+  assert(rate_bytes_per_sec > 0);
+  assert(refill_period_us > 0);
+  assert(fairness > 0);
+  return new GenericRateLimiter(rate_bytes_per_sec, refill_period_us, fairness,
+                                mode, Env::Default(), auto_tuned);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/rate_limiter.h b/src/rocksdb/util/rate_limiter.h
new file mode 100644
index 000000000..5f047a567
--- /dev/null
+++ b/src/rocksdb/util/rate_limiter.h
@@ -0,0 +1,113 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+
+#include <algorithm>
+#include <atomic>
+#include <chrono>
+#include <deque>
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "rocksdb/rate_limiter.h"
+#include "util/mutexlock.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class GenericRateLimiter : public RateLimiter {
+ public:
+  GenericRateLimiter(int64_t refill_bytes, int64_t refill_period_us,
+                     int32_t fairness, RateLimiter::Mode mode, Env* env,
+                     bool auto_tuned);
+
+  virtual ~GenericRateLimiter();
+
+  // This API allows user to dynamically change rate limiter's bytes per second.
+  virtual void SetBytesPerSecond(int64_t bytes_per_second) override;
+
+  // Request for token to write bytes. If this request can not be satisfied,
+  // the call is blocked. Caller is responsible to make sure
+  // bytes <= GetSingleBurstBytes()
+  using RateLimiter::Request;
+  virtual void Request(const int64_t bytes, const Env::IOPriority pri,
+                       Statistics* stats) override;
+
+  virtual int64_t GetSingleBurstBytes() const override {
+    return refill_bytes_per_period_.load(std::memory_order_relaxed);
+  }
+
+  virtual int64_t GetTotalBytesThrough(
+      const Env::IOPriority pri = Env::IO_TOTAL) const override {
+    MutexLock g(&request_mutex_);
+    if (pri == Env::IO_TOTAL) {
+      return total_bytes_through_[Env::IO_LOW] +
+             total_bytes_through_[Env::IO_HIGH];
+    }
+    return total_bytes_through_[pri];
+  }
+
+  virtual int64_t GetTotalRequests(
+      const Env::IOPriority pri = Env::IO_TOTAL) const override {
+    MutexLock g(&request_mutex_);
+    if (pri == Env::IO_TOTAL) {
+      return total_requests_[Env::IO_LOW] + total_requests_[Env::IO_HIGH];
+    }
+    return total_requests_[pri];
+  }
+
+  virtual int64_t GetBytesPerSecond() const override {
+    return rate_bytes_per_sec_;
+  }
+
+ private:
+  void Refill();
+  int64_t CalculateRefillBytesPerPeriod(int64_t rate_bytes_per_sec);
+  Status Tune();
+
+  uint64_t NowMicrosMonotonic(Env* env) {
+    return env->NowNanos() / std::milli::den;
+  }
+
+  // This mutex guard all internal states
+  mutable port::Mutex request_mutex_;
+
+  const int64_t kMinRefillBytesPerPeriod = 100;
+
+  const int64_t refill_period_us_;
+
+  int64_t rate_bytes_per_sec_;
+  // This variable can be changed dynamically.
+  std::atomic<int64_t> refill_bytes_per_period_;
+  Env* const env_;
+
+  bool stop_;
+  port::CondVar exit_cv_;
+  int32_t requests_to_wait_;
+
+  int64_t total_requests_[Env::IO_TOTAL];
+  int64_t total_bytes_through_[Env::IO_TOTAL];
+  int64_t available_bytes_;
+  int64_t next_refill_us_;
+
+  int32_t fairness_;
+  Random rnd_;
+
+  struct Req;
+  Req* leader_;
+  std::deque<Req*> queue_[Env::IO_TOTAL];
+
+  bool auto_tuned_;
+  int64_t num_drains_;
+  int64_t prev_num_drains_;
+  const int64_t max_bytes_per_sec_;
+  std::chrono::microseconds tuned_time_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/rate_limiter_test.cc b/src/rocksdb/util/rate_limiter_test.cc
new file mode 100644
index 000000000..6ca91e9e2
--- /dev/null
+++ b/src/rocksdb/util/rate_limiter_test.cc
@@ -0,0 +1,235 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/rate_limiter.h"
+
+#include <chrono>
+#include <cinttypes>
+#include <limits>
+
+#include "db/db_test_util.h"
+#include "rocksdb/env.h"
+#include "test_util/sync_point.h"
+#include "test_util/testharness.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// TODO(yhchiang): the rate will not be accurate when we run test in parallel.
+class RateLimiterTest : public testing::Test {};
+
+TEST_F(RateLimiterTest, OverflowRate) {
+  GenericRateLimiter limiter(port::kMaxInt64, 1000, 10,
+                             RateLimiter::Mode::kWritesOnly, Env::Default(),
+                             false /* auto_tuned */);
+  ASSERT_GT(limiter.GetSingleBurstBytes(), 1000000000ll);
+}
+
+TEST_F(RateLimiterTest, StartStop) {
+  std::unique_ptr<RateLimiter> limiter(NewGenericRateLimiter(100, 100, 10));
+}
+
+TEST_F(RateLimiterTest, Modes) {
+  for (auto mode : {RateLimiter::Mode::kWritesOnly,
+                    RateLimiter::Mode::kReadsOnly, RateLimiter::Mode::kAllIo}) {
+    GenericRateLimiter limiter(
+        2000 /* rate_bytes_per_sec */, 1000 * 1000 /* refill_period_us */,
+        10 /* fairness */, mode, Env::Default(), false /* auto_tuned */);
+    limiter.Request(1000 /* bytes */, Env::IO_HIGH, nullptr /* stats */,
+                    RateLimiter::OpType::kRead);
+    if (mode == RateLimiter::Mode::kWritesOnly) {
+      ASSERT_EQ(0, limiter.GetTotalBytesThrough(Env::IO_HIGH));
+    } else {
+      ASSERT_EQ(1000, limiter.GetTotalBytesThrough(Env::IO_HIGH));
+    }
+
+    limiter.Request(1000 /* bytes */, Env::IO_HIGH, nullptr /* stats */,
+                    RateLimiter::OpType::kWrite);
+    if (mode == RateLimiter::Mode::kAllIo) {
+      ASSERT_EQ(2000, limiter.GetTotalBytesThrough(Env::IO_HIGH));
+    } else {
+      ASSERT_EQ(1000, limiter.GetTotalBytesThrough(Env::IO_HIGH));
+    }
+  }
+}
+
+#if !(defined(TRAVIS) && defined(OS_MACOSX))
+TEST_F(RateLimiterTest, Rate) {
+  auto* env = Env::Default();
+  struct Arg {
+    Arg(int32_t _target_rate, int _burst)
+        : limiter(NewGenericRateLimiter(_target_rate, 100 * 1000, 10)),
+          request_size(_target_rate / 10),
+          burst(_burst) {}
+    std::unique_ptr<RateLimiter> limiter;
+    int32_t request_size;
+    int burst;
+  };
+
+  auto writer = [](void* p) {
+    auto* thread_env = Env::Default();
+    auto* arg = static_cast<Arg*>(p);
+    // Test for 2 seconds
+    auto until = thread_env->NowMicros() + 2 * 1000000;
+    Random r((uint32_t)(thread_env->NowNanos() %
+                        std::numeric_limits<uint32_t>::max()));
+    while (thread_env->NowMicros() < until) {
+      for (int i = 0; i < static_cast<int>(r.Skewed(arg->burst) + 1); ++i) {
+        arg->limiter->Request(r.Uniform(arg->request_size - 1) + 1,
+                              Env::IO_HIGH, nullptr /* stats */,
+                              RateLimiter::OpType::kWrite);
+      }
+      arg->limiter->Request(r.Uniform(arg->request_size - 1) + 1, Env::IO_LOW,
+                            nullptr /* stats */, RateLimiter::OpType::kWrite);
+    }
+  };
+
+  for (int i = 1; i <= 16; i *= 2) {
+    int32_t target = i * 1024 * 10;
+    Arg arg(target, i / 4 + 1);
+    int64_t old_total_bytes_through = 0;
+    for (int iter = 1; iter <= 2; ++iter) {
+      // second iteration changes the target dynamically
+      if (iter == 2) {
+        target *= 2;
+        arg.limiter->SetBytesPerSecond(target);
+      }
+      auto start = env->NowMicros();
+      for (int t = 0; t < i; ++t) {
+        env->StartThread(writer, &arg);
+      }
+      env->WaitForJoin();
+
+      auto elapsed = env->NowMicros() - start;
+      double rate =
+          (arg.limiter->GetTotalBytesThrough() - old_total_bytes_through) *
+          1000000.0 / elapsed;
+      old_total_bytes_through = arg.limiter->GetTotalBytesThrough();
+      fprintf(stderr,
+              "request size [1 - %" PRIi32 "], limit %" PRIi32
+              " KB/sec, actual rate: %lf KB/sec, elapsed %.2lf seconds\n",
+              arg.request_size - 1, target / 1024, rate / 1024,
+              elapsed / 1000000.0);
+
+      ASSERT_GE(rate / target, 0.80);
+      ASSERT_LE(rate / target, 1.25);
+    }
+  }
+}
+#endif
+
+TEST_F(RateLimiterTest, LimitChangeTest) {
+  // starvation test when limit changes to a smaller value
+  int64_t refill_period = 1000 * 1000;
+  auto* env = Env::Default();
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+  struct Arg {
+    Arg(int32_t _request_size, Env::IOPriority _pri,
+        std::shared_ptr<RateLimiter> _limiter)
+        : request_size(_request_size), pri(_pri), limiter(_limiter) {}
+    int32_t request_size;
+    Env::IOPriority pri;
+    std::shared_ptr<RateLimiter> limiter;
+  };
+
+  auto writer = [](void* p) {
+    auto* arg = static_cast<Arg*>(p);
+    arg->limiter->Request(arg->request_size, arg->pri, nullptr /* stats */,
+                          RateLimiter::OpType::kWrite);
+  };
+
+  for (uint32_t i = 1; i <= 16; i <<= 1) {
+    int32_t target = i * 1024 * 10;
+    // refill per second
+    for (int iter = 0; iter < 2; iter++) {
+      std::shared_ptr<RateLimiter> limiter =
+          std::make_shared<GenericRateLimiter>(
+              target, refill_period, 10, RateLimiter::Mode::kWritesOnly,
+              Env::Default(), false /* auto_tuned */);
+      ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->LoadDependency(
+          {{"GenericRateLimiter::Request",
+            "RateLimiterTest::LimitChangeTest:changeLimitStart"},
+           {"RateLimiterTest::LimitChangeTest:changeLimitEnd",
+            "GenericRateLimiter::Refill"}});
+      Arg arg(target, Env::IO_HIGH, limiter);
+      // The idea behind is to start a request first, then before it refills,
+      // update limit to a different value (2X/0.5X). No starvation should
+      // be guaranteed under any situation
+      // TODO(lightmark): more test cases are welcome.
+      env->StartThread(writer, &arg);
+      int32_t new_limit = (target << 1) >> (iter << 1);
+      TEST_SYNC_POINT("RateLimiterTest::LimitChangeTest:changeLimitStart");
+      arg.limiter->SetBytesPerSecond(new_limit);
+      TEST_SYNC_POINT("RateLimiterTest::LimitChangeTest:changeLimitEnd");
+      env->WaitForJoin();
+      fprintf(stderr,
+              "[COMPLETE] request size %" PRIi32 " KB, new limit %" PRIi32
+              "KB/sec, refill period %" PRIi64 " ms\n",
+              target / 1024, new_limit / 1024, refill_period / 1000);
+    }
+  }
+}
+
+TEST_F(RateLimiterTest, AutoTuneIncreaseWhenFull) {
+  const std::chrono::seconds kTimePerRefill(1);
+  const int kRefillsPerTune = 100;  // needs to match util/rate_limiter.cc
+
+  SpecialEnv special_env(Env::Default());
+  special_env.no_slowdown_ = true;
+  special_env.time_elapse_only_sleep_ = true;
+
+  auto stats = CreateDBStatistics();
+  std::unique_ptr<RateLimiter> rate_limiter(new GenericRateLimiter(
+      1000 /* rate_bytes_per_sec */,
+      std::chrono::microseconds(kTimePerRefill).count(), 10 /* fairness */,
+      RateLimiter::Mode::kWritesOnly, &special_env, true /* auto_tuned */));
+
+  // Use callback to advance time because we need to advance (1) after Request()
+  // has determined the bytes are not available; and (2) before Refill()
+  // computes the next refill time (ensuring refill time in the future allows
+  // the next request to drain the rate limiter).
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+      "GenericRateLimiter::Refill", [&](void* /*arg*/) {
+        special_env.SleepForMicroseconds(static_cast<int>(
+            std::chrono::microseconds(kTimePerRefill).count()));
+      });
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+
+  // verify rate limit increases after a sequence of periods where rate limiter
+  // is always drained
+  int64_t orig_bytes_per_sec = rate_limiter->GetSingleBurstBytes();
+  rate_limiter->Request(orig_bytes_per_sec, Env::IO_HIGH, stats.get(),
+                        RateLimiter::OpType::kWrite);
+  while (std::chrono::microseconds(special_env.NowMicros()) <=
+         kRefillsPerTune * kTimePerRefill) {
+    rate_limiter->Request(orig_bytes_per_sec, Env::IO_HIGH, stats.get(),
+                          RateLimiter::OpType::kWrite);
+  }
+  int64_t new_bytes_per_sec = rate_limiter->GetSingleBurstBytes();
+  ASSERT_GT(new_bytes_per_sec, orig_bytes_per_sec);
+
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->DisableProcessing();
+
+  // decreases after a sequence of periods where rate limiter is not drained
+  orig_bytes_per_sec = new_bytes_per_sec;
+  special_env.SleepForMicroseconds(static_cast<int>(
+      kRefillsPerTune * std::chrono::microseconds(kTimePerRefill).count()));
+  // make a request so tuner can be triggered
+  rate_limiter->Request(1 /* bytes */, Env::IO_HIGH, stats.get(),
+                        RateLimiter::OpType::kWrite);
+  new_bytes_per_sec = rate_limiter->GetSingleBurstBytes();
+  ASSERT_LT(new_bytes_per_sec, orig_bytes_per_sec);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/repeatable_thread.h b/src/rocksdb/util/repeatable_thread.h
new file mode 100644
index 000000000..1ac8edee6
--- /dev/null
+++ b/src/rocksdb/util/repeatable_thread.h
@@ -0,0 +1,149 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <functional>
+#include <string>
+
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "test_util/mock_time_env.h"
+#include "util/mutexlock.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Simple wrapper around port::Thread that supports calling a callback every
+// X seconds. If you pass in 0, then it will call your callback repeatedly
+// without delay.
+class RepeatableThread {
+ public:
+  RepeatableThread(std::function<void()> function,
+                   const std::string& thread_name, Env* env, uint64_t delay_us,
+                   uint64_t initial_delay_us = 0)
+      : function_(function),
+        thread_name_("rocksdb:" + thread_name),
+        env_(env),
+        delay_us_(delay_us),
+        initial_delay_us_(initial_delay_us),
+        mutex_(env),
+        cond_var_(&mutex_),
+        running_(true),
+#ifndef NDEBUG
+        waiting_(false),
+        run_count_(0),
+#endif
+        thread_([this] { thread(); }) {
+  }
+
+  void cancel() {
+    {
+      InstrumentedMutexLock l(&mutex_);
+      if (!running_) {
+        return;
+      }
+      running_ = false;
+      cond_var_.SignalAll();
+    }
+    thread_.join();
+  }
+
+  bool IsRunning() { return running_; }
+
+  ~RepeatableThread() { cancel(); }
+
+#ifndef NDEBUG
+  // Wait until RepeatableThread starting waiting, call the optional callback,
+  // then wait for one run of RepeatableThread. Tests can use provide a
+  // custom env object to mock time, and use the callback here to bump current
+  // time and trigger RepeatableThread. See repeatable_thread_test for example.
+  //
+  // Note: only support one caller of this method.
+  void TEST_WaitForRun(std::function<void()> callback = nullptr) {
+    InstrumentedMutexLock l(&mutex_);
+    while (!waiting_) {
+      cond_var_.Wait();
+    }
+    uint64_t prev_count = run_count_;
+    if (callback != nullptr) {
+      callback();
+    }
+    cond_var_.SignalAll();
+    while (!(run_count_ > prev_count)) {
+      cond_var_.Wait();
+    }
+  }
+#endif
+
+ private:
+  bool wait(uint64_t delay) {
+    InstrumentedMutexLock l(&mutex_);
+    if (running_ && delay > 0) {
+      uint64_t wait_until = env_->NowMicros() + delay;
+#ifndef NDEBUG
+      waiting_ = true;
+      cond_var_.SignalAll();
+#endif
+      while (running_) {
+        cond_var_.TimedWait(wait_until);
+        if (env_->NowMicros() >= wait_until) {
+          break;
+        }
+      }
+#ifndef NDEBUG
+      waiting_ = false;
+#endif
+    }
+    return running_;
+  }
+
+  void thread() {
+#if defined(_GNU_SOURCE) && defined(__GLIBC_PREREQ)
+#if __GLIBC_PREREQ(2, 12)
+    // Set thread name.
+    auto thread_handle = thread_.native_handle();
+    int ret __attribute__((__unused__)) =
+        pthread_setname_np(thread_handle, thread_name_.c_str());
+    assert(ret == 0);
+#endif
+#endif
+
+    assert(delay_us_ > 0);
+    if (!wait(initial_delay_us_)) {
+      return;
+    }
+    do {
+      function_();
+#ifndef NDEBUG
+      {
+        InstrumentedMutexLock l(&mutex_);
+        run_count_++;
+        cond_var_.SignalAll();
+      }
+#endif
+    } while (wait(delay_us_));
+  }
+
+  const std::function<void()> function_;
+  const std::string thread_name_;
+  Env* const env_;
+  const uint64_t delay_us_;
+  const uint64_t initial_delay_us_;
+
+  // Mutex lock should be held when accessing running_, waiting_
+  // and run_count_.
+  InstrumentedMutex mutex_;
+  InstrumentedCondVar cond_var_;
+  bool running_;
+#ifndef NDEBUG
+  // RepeatableThread waiting for timeout.
+  bool waiting_;
+  // Times function_ had run.
+  uint64_t run_count_;
+#endif
+  port::Thread thread_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/repeatable_thread_test.cc b/src/rocksdb/util/repeatable_thread_test.cc
new file mode 100644
index 000000000..a18aa6cd1
--- /dev/null
+++ b/src/rocksdb/util/repeatable_thread_test.cc
@@ -0,0 +1,107 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <atomic>
+#include <memory>
+
+#include "db/db_test_util.h"
+#include "test_util/sync_point.h"
+#include "test_util/testharness.h"
+#include "util/repeatable_thread.h"
+
+class RepeatableThreadTest : public testing::Test {
+ public:
+  RepeatableThreadTest()
+      : mock_env_(new ROCKSDB_NAMESPACE::MockTimeEnv(
+            ROCKSDB_NAMESPACE::Env::Default())) {}
+
+ protected:
+  std::unique_ptr<ROCKSDB_NAMESPACE::MockTimeEnv> mock_env_;
+};
+
+TEST_F(RepeatableThreadTest, TimedTest) {
+  constexpr uint64_t kSecond = 1000000;  // 1s = 1000000us
+  constexpr int kIteration = 3;
+  ROCKSDB_NAMESPACE::Env* env = ROCKSDB_NAMESPACE::Env::Default();
+  ROCKSDB_NAMESPACE::port::Mutex mutex;
+  ROCKSDB_NAMESPACE::port::CondVar test_cv(&mutex);
+  int count = 0;
+  uint64_t prev_time = env->NowMicros();
+  ROCKSDB_NAMESPACE::RepeatableThread thread(
+      [&] {
+        ROCKSDB_NAMESPACE::MutexLock l(&mutex);
+        count++;
+        uint64_t now = env->NowMicros();
+        assert(count == 1 || prev_time + 1 * kSecond <= now);
+        prev_time = now;
+        if (count >= kIteration) {
+          test_cv.SignalAll();
+        }
+      },
+      "rt_test", env, 1 * kSecond);
+  // Wait for execution finish.
+  {
+    ROCKSDB_NAMESPACE::MutexLock l(&mutex);
+    while (count < kIteration) {
+      test_cv.Wait();
+    }
+  }
+
+  // Test cancel
+  thread.cancel();
+}
+
+TEST_F(RepeatableThreadTest, MockEnvTest) {
+  constexpr uint64_t kSecond = 1000000;  // 1s = 1000000us
+  constexpr int kIteration = 3;
+  mock_env_->set_current_time(0);  // in seconds
+  std::atomic<int> count{0};
+
+#if defined(OS_MACOSX) && !defined(NDEBUG)
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->DisableProcessing();
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->ClearAllCallBacks();
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+      "InstrumentedCondVar::TimedWaitInternal", [&](void* arg) {
+        // Obtain the current (real) time in seconds and add 1000 extra seconds
+        // to ensure that RepeatableThread::wait invokes TimedWait with a time
+        // greater than (real) current time. This is to prevent the TimedWait
+        // function from returning immediately without sleeping and releasing
+        // the mutex on certain platforms, e.g. OS X. If TimedWait returns
+        // immediately, the mutex will not be released, and
+        // RepeatableThread::TEST_WaitForRun never has a chance to execute the
+        // callback which, in this case, updates the result returned by
+        // mock_env->NowMicros. Consequently, RepeatableThread::wait cannot
+        // break out of the loop, causing test to hang. The extra 1000 seconds
+        // is a best-effort approach because there seems no reliable and
+        // deterministic way to provide the aforementioned guarantee. By the
+        // time RepeatableThread::wait is called, it is no guarantee that the
+        // delay + mock_env->NowMicros will be greater than the current real
+        // time. However, 1000 seconds should be sufficient in most cases.
+        uint64_t time_us = *reinterpret_cast<uint64_t*>(arg);
+        if (time_us < mock_env_->RealNowMicros()) {
+          *reinterpret_cast<uint64_t*>(arg) = mock_env_->RealNowMicros() + 1000;
+        }
+      });
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+#endif  // OS_MACOSX && !NDEBUG
+
+  ROCKSDB_NAMESPACE::RepeatableThread thread(
+      [&] { count++; }, "rt_test", mock_env_.get(), 1 * kSecond, 1 * kSecond);
+  for (int i = 1; i <= kIteration; i++) {
+    // Bump current time
+    thread.TEST_WaitForRun([&] { mock_env_->set_current_time(i); });
+  }
+  // Test function should be exectued exactly kIteraion times.
+  ASSERT_EQ(kIteration, count.load());
+
+  // Test cancel
+  thread.cancel();
+}
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/set_comparator.h b/src/rocksdb/util/set_comparator.h
new file mode 100644
index 000000000..9b5cfc1dc
--- /dev/null
+++ b/src/rocksdb/util/set_comparator.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+namespace ROCKSDB_NAMESPACE {
+// A comparator to be used in std::set
+struct SetComparator {
+  explicit SetComparator() : user_comparator_(BytewiseComparator()) {}
+  explicit SetComparator(const Comparator* user_comparator)
+      : user_comparator_(user_comparator ? user_comparator
+                                         : BytewiseComparator()) {}
+  bool operator()(const Slice& lhs, const Slice& rhs) const {
+    return user_comparator_->Compare(lhs, rhs) < 0;
+  }
+
+ private:
+  const Comparator* user_comparator_;
+};
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/slice.cc b/src/rocksdb/util/slice.cc
new file mode 100644
index 000000000..6db11cc94
--- /dev/null
+++ b/src/rocksdb/util/slice.cc
@@ -0,0 +1,243 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <algorithm>
+#include "rocksdb/slice_transform.h"
+#include "rocksdb/slice.h"
+#include "util/string_util.h"
+#include <stdio.h>
+
+namespace ROCKSDB_NAMESPACE {
+
+namespace {
+
+class FixedPrefixTransform : public SliceTransform {
+ private:
+  size_t prefix_len_;
+  std::string name_;
+
+ public:
+  explicit FixedPrefixTransform(size_t prefix_len)
+      : prefix_len_(prefix_len),
+        // Note that if any part of the name format changes, it will require
+        // changes on options_helper in order to make RocksDBOptionsParser work
+        // for the new change.
+        // TODO(yhchiang): move serialization / deserializaion code inside
+        // the class implementation itself.
+        name_("rocksdb.FixedPrefix." + ToString(prefix_len_)) {}
+
+  const char* Name() const override { return name_.c_str(); }
+
+  Slice Transform(const Slice& src) const override {
+    assert(InDomain(src));
+    return Slice(src.data(), prefix_len_);
+  }
+
+  bool InDomain(const Slice& src) const override {
+    return (src.size() >= prefix_len_);
+  }
+
+  bool InRange(const Slice& dst) const override {
+    return (dst.size() == prefix_len_);
+  }
+
+  bool FullLengthEnabled(size_t* len) const override {
+    *len = prefix_len_;
+    return true;
+  }
+
+  bool SameResultWhenAppended(const Slice& prefix) const override {
+    return InDomain(prefix);
+  }
+};
+
+class CappedPrefixTransform : public SliceTransform {
+ private:
+  size_t cap_len_;
+  std::string name_;
+
+ public:
+  explicit CappedPrefixTransform(size_t cap_len)
+      : cap_len_(cap_len),
+        // Note that if any part of the name format changes, it will require
+        // changes on options_helper in order to make RocksDBOptionsParser work
+        // for the new change.
+        // TODO(yhchiang): move serialization / deserializaion code inside
+        // the class implementation itself.
+        name_("rocksdb.CappedPrefix." + ToString(cap_len_)) {}
+
+  const char* Name() const override { return name_.c_str(); }
+
+  Slice Transform(const Slice& src) const override {
+    assert(InDomain(src));
+    return Slice(src.data(), std::min(cap_len_, src.size()));
+  }
+
+  bool InDomain(const Slice& /*src*/) const override { return true; }
+
+  bool InRange(const Slice& dst) const override {
+    return (dst.size() <= cap_len_);
+  }
+
+  bool FullLengthEnabled(size_t* len) const override {
+    *len = cap_len_;
+    return true;
+  }
+
+  bool SameResultWhenAppended(const Slice& prefix) const override {
+    return prefix.size() >= cap_len_;
+  }
+};
+
+class NoopTransform : public SliceTransform {
+ public:
+  explicit NoopTransform() { }
+
+  const char* Name() const override { return "rocksdb.Noop"; }
+
+  Slice Transform(const Slice& src) const override { return src; }
+
+  bool InDomain(const Slice& /*src*/) const override { return true; }
+
+  bool InRange(const Slice& /*dst*/) const override { return true; }
+
+  bool SameResultWhenAppended(const Slice& /*prefix*/) const override {
+    return false;
+  }
+};
+
+}
+
+// 2 small internal utility functions, for efficient hex conversions
+// and no need for snprintf, toupper etc...
+// Originally from wdt/util/EncryptionUtils.cpp - for ToString(true)/DecodeHex:
+char toHex(unsigned char v) {
+  if (v <= 9) {
+    return '0' + v;
+  }
+  return 'A' + v - 10;
+}
+// most of the code is for validation/error check
+int fromHex(char c) {
+  // toupper:
+  if (c >= 'a' && c <= 'f') {
+    c -= ('a' - 'A');  // aka 0x20
+  }
+  // validation
+  if (c < '0' || (c > '9' && (c < 'A' || c > 'F'))) {
+    return -1;  // invalid not 0-9A-F hex char
+  }
+  if (c <= '9') {
+    return c - '0';
+  }
+  return c - 'A' + 10;
+}
+
+Slice::Slice(const SliceParts& parts, std::string* buf) {
+  size_t length = 0;
+  for (int i = 0; i < parts.num_parts; ++i) {
+    length += parts.parts[i].size();
+  }
+  buf->reserve(length);
+
+  for (int i = 0; i < parts.num_parts; ++i) {
+    buf->append(parts.parts[i].data(), parts.parts[i].size());
+  }
+  data_ = buf->data();
+  size_ = buf->size();
+}
+
+// Return a string that contains the copy of the referenced data.
+std::string Slice::ToString(bool hex) const {
+  std::string result;  // RVO/NRVO/move
+  if (hex) {
+    result.reserve(2 * size_);
+    for (size_t i = 0; i < size_; ++i) {
+      unsigned char c = data_[i];
+      result.push_back(toHex(c >> 4));
+      result.push_back(toHex(c & 0xf));
+    }
+    return result;
+  } else {
+    result.assign(data_, size_);
+    return result;
+  }
+}
+
+// Originally from rocksdb/utilities/ldb_cmd.h
+bool Slice::DecodeHex(std::string* result) const {
+  std::string::size_type len = size_;
+  if (len % 2) {
+    // Hex string must be even number of hex digits to get complete bytes back
+    return false;
+  }
+  if (!result) {
+    return false;
+  }
+  result->clear();
+  result->reserve(len / 2);
+
+  for (size_t i = 0; i < len;) {
+    int h1 = fromHex(data_[i++]);
+    if (h1 < 0) {
+      return false;
+    }
+    int h2 = fromHex(data_[i++]);
+    if (h2 < 0) {
+      return false;
+    }
+    result->push_back(static_cast<char>((h1 << 4) | h2));
+  }
+  return true;
+}
+
+const SliceTransform* NewFixedPrefixTransform(size_t prefix_len) {
+  return new FixedPrefixTransform(prefix_len);
+}
+
+const SliceTransform* NewCappedPrefixTransform(size_t cap_len) {
+  return new CappedPrefixTransform(cap_len);
+}
+
+const SliceTransform* NewNoopTransform() {
+  return new NoopTransform;
+}
+
+PinnableSlice::PinnableSlice(PinnableSlice&& other) {
+  *this = std::move(other);
+}
+
+PinnableSlice& PinnableSlice::operator=(PinnableSlice&& other) {
+  if (this != &other) {
+    Cleanable::Reset();
+    Cleanable::operator=(std::move(other));
+    size_ = other.size_;
+    pinned_ = other.pinned_;
+    if (pinned_) {
+      data_ = other.data_;
+      // When it's pinned, buf should no longer be of use.
+    } else {
+      if (other.buf_ == &other.self_space_) {
+        self_space_ = std::move(other.self_space_);
+        buf_ = &self_space_;
+        data_ = buf_->data();
+      } else {
+        buf_ = other.buf_;
+        data_ = other.data_;
+      }
+    }
+    other.self_space_.clear();
+    other.buf_ = &other.self_space_;
+    other.pinned_ = false;
+    other.PinSelf();
+  }
+  return *this;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/slice_test.cc b/src/rocksdb/util/slice_test.cc
new file mode 100644
index 000000000..9e8a8e340
--- /dev/null
+++ b/src/rocksdb/util/slice_test.cc
@@ -0,0 +1,163 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "port/port.h"
+#include "port/stack_trace.h"
+#include "rocksdb/slice.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Use this to keep track of the cleanups that were actually performed
+void Multiplier(void* arg1, void* arg2) {
+  int* res = reinterpret_cast<int*>(arg1);
+  int* num = reinterpret_cast<int*>(arg2);
+  *res *= *num;
+}
+
+class PinnableSliceTest : public testing::Test {
+ public:
+  void AssertSameData(const std::string& expected,
+                      const PinnableSlice& slice) {
+    std::string got;
+    got.assign(slice.data(), slice.size());
+    ASSERT_EQ(expected, got);
+  }
+};
+
+// Test that the external buffer is moved instead of being copied.
+TEST_F(PinnableSliceTest, MoveExternalBuffer) {
+  Slice s("123");
+  std::string buf;
+  PinnableSlice v1(&buf);
+  v1.PinSelf(s);
+
+  PinnableSlice v2(std::move(v1));
+  ASSERT_EQ(buf.data(), v2.data());
+  ASSERT_EQ(&buf, v2.GetSelf());
+
+  PinnableSlice v3;
+  v3 = std::move(v2);
+  ASSERT_EQ(buf.data(), v3.data());
+  ASSERT_EQ(&buf, v3.GetSelf());
+}
+
+TEST_F(PinnableSliceTest, Move) {
+  int n2 = 2;
+  int res = 1;
+  const std::string const_str1 = "123";
+  const std::string const_str2 = "ABC";
+  Slice slice1(const_str1);
+  Slice slice2(const_str2);
+
+  {
+    // Test move constructor on a pinned slice.
+    res = 1;
+    PinnableSlice v1;
+    v1.PinSlice(slice1, Multiplier, &res, &n2);
+    PinnableSlice v2(std::move(v1));
+
+    // Since v1's Cleanable has been moved to v2,
+    // no cleanup should happen in Reset.
+    v1.Reset();
+    ASSERT_EQ(1, res);
+
+    AssertSameData(const_str1, v2);
+  }
+  // v2 is cleaned up.
+  ASSERT_EQ(2, res);
+
+  {
+    // Test move constructor on an unpinned slice.
+    PinnableSlice v1;
+    v1.PinSelf(slice1);
+    PinnableSlice v2(std::move(v1));
+
+    AssertSameData(const_str1, v2);
+  }
+
+  {
+    // Test move assignment from a pinned slice to
+    // another pinned slice.
+    res = 1;
+    PinnableSlice v1;
+    v1.PinSlice(slice1, Multiplier, &res, &n2);
+    PinnableSlice v2;
+    v2.PinSlice(slice2, Multiplier, &res, &n2);
+    v2 = std::move(v1);
+
+    // v2's Cleanable will be Reset before moving
+    // anything from v1.
+    ASSERT_EQ(2, res);
+    // Since v1's Cleanable has been moved to v2,
+    // no cleanup should happen in Reset.
+    v1.Reset();
+    ASSERT_EQ(2, res);
+
+    AssertSameData(const_str1, v2);
+  }
+  // The Cleanable moved from v1 to v2 will be Reset.
+  ASSERT_EQ(4, res);
+
+  {
+    // Test move assignment from a pinned slice to
+    // an unpinned slice.
+    res = 1;
+    PinnableSlice v1;
+    v1.PinSlice(slice1, Multiplier, &res, &n2);
+    PinnableSlice v2;
+    v2.PinSelf(slice2);
+    v2 = std::move(v1);
+
+    // Since v1's Cleanable has been moved to v2,
+    // no cleanup should happen in Reset.
+    v1.Reset();
+    ASSERT_EQ(1, res);
+
+    AssertSameData(const_str1, v2);
+  }
+  // The Cleanable moved from v1 to v2 will be Reset.
+  ASSERT_EQ(2, res);
+
+  {
+    // Test move assignment from an upinned slice to
+    // another unpinned slice.
+    PinnableSlice v1;
+    v1.PinSelf(slice1);
+    PinnableSlice v2;
+    v2.PinSelf(slice2);
+    v2 = std::move(v1);
+
+    AssertSameData(const_str1, v2);
+  }
+
+  {
+    // Test move assignment from an upinned slice to
+    // a pinned slice.
+    res = 1;
+    PinnableSlice v1;
+    v1.PinSelf(slice1);
+    PinnableSlice v2;
+    v2.PinSlice(slice2, Multiplier, &res, &n2);
+    v2 = std::move(v1);
+
+    // v2's Cleanable will be Reset before moving
+    // anything from v1.
+    ASSERT_EQ(2, res);
+
+    AssertSameData(const_str1, v2);
+  }
+  // No Cleanable is moved from v1 to v2, so no more cleanup.
+  ASSERT_EQ(2, res);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/slice_transform_test.cc b/src/rocksdb/util/slice_transform_test.cc
new file mode 100644
index 000000000..6550cadea
--- /dev/null
+++ b/src/rocksdb/util/slice_transform_test.cc
@@ -0,0 +1,153 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "rocksdb/slice_transform.h"
+
+#include "rocksdb/db.h"
+#include "rocksdb/env.h"
+#include "rocksdb/filter_policy.h"
+#include "rocksdb/statistics.h"
+#include "rocksdb/table.h"
+#include "test_util/testharness.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class SliceTransformTest : public testing::Test {};
+
+TEST_F(SliceTransformTest, CapPrefixTransform) {
+  std::string s;
+  s = "abcdefge";
+
+  std::unique_ptr<const SliceTransform> transform;
+
+  transform.reset(NewCappedPrefixTransform(6));
+  ASSERT_EQ(transform->Transform(s).ToString(), "abcdef");
+  ASSERT_TRUE(transform->SameResultWhenAppended("123456"));
+  ASSERT_TRUE(transform->SameResultWhenAppended("1234567"));
+  ASSERT_TRUE(!transform->SameResultWhenAppended("12345"));
+
+  transform.reset(NewCappedPrefixTransform(8));
+  ASSERT_EQ(transform->Transform(s).ToString(), "abcdefge");
+
+  transform.reset(NewCappedPrefixTransform(10));
+  ASSERT_EQ(transform->Transform(s).ToString(), "abcdefge");
+
+  transform.reset(NewCappedPrefixTransform(0));
+  ASSERT_EQ(transform->Transform(s).ToString(), "");
+
+  transform.reset(NewCappedPrefixTransform(0));
+  ASSERT_EQ(transform->Transform("").ToString(), "");
+}
+
+class SliceTransformDBTest : public testing::Test {
+ private:
+  std::string dbname_;
+  Env* env_;
+  DB* db_;
+
+ public:
+  SliceTransformDBTest() : env_(Env::Default()), db_(nullptr) {
+    dbname_ = test::PerThreadDBPath("slice_transform_db_test");
+    EXPECT_OK(DestroyDB(dbname_, last_options_));
+  }
+
+  ~SliceTransformDBTest() override {
+    delete db_;
+    EXPECT_OK(DestroyDB(dbname_, last_options_));
+  }
+
+  DB* db() { return db_; }
+
+  // Return the current option configuration.
+  Options* GetOptions() { return &last_options_; }
+
+  void DestroyAndReopen() {
+    // Destroy using last options
+    Destroy();
+    ASSERT_OK(TryReopen());
+  }
+
+  void Destroy() {
+    delete db_;
+    db_ = nullptr;
+    ASSERT_OK(DestroyDB(dbname_, last_options_));
+  }
+
+  Status TryReopen() {
+    delete db_;
+    db_ = nullptr;
+    last_options_.create_if_missing = true;
+
+    return DB::Open(last_options_, dbname_, &db_);
+  }
+
+  Options last_options_;
+};
+
+namespace {
+uint64_t TestGetTickerCount(const Options& options, Tickers ticker_type) {
+  return options.statistics->getTickerCount(ticker_type);
+}
+}  // namespace
+
+TEST_F(SliceTransformDBTest, CapPrefix) {
+  last_options_.prefix_extractor.reset(NewCappedPrefixTransform(8));
+  last_options_.statistics = ROCKSDB_NAMESPACE::CreateDBStatistics();
+  BlockBasedTableOptions bbto;
+  bbto.filter_policy.reset(NewBloomFilterPolicy(10, false));
+  bbto.whole_key_filtering = false;
+  last_options_.table_factory.reset(NewBlockBasedTableFactory(bbto));
+  ASSERT_OK(TryReopen());
+
+  ReadOptions ro;
+  FlushOptions fo;
+  WriteOptions wo;
+
+  ASSERT_OK(db()->Put(wo, "barbarbar", "foo"));
+  ASSERT_OK(db()->Put(wo, "barbarbar2", "foo2"));
+  ASSERT_OK(db()->Put(wo, "foo", "bar"));
+  ASSERT_OK(db()->Put(wo, "foo3", "bar3"));
+  ASSERT_OK(db()->Flush(fo));
+
+  std::unique_ptr<Iterator> iter(db()->NewIterator(ro));
+
+  iter->Seek("foo");
+  ASSERT_OK(iter->status());
+  ASSERT_TRUE(iter->Valid());
+  ASSERT_EQ(iter->value().ToString(), "bar");
+  ASSERT_EQ(TestGetTickerCount(last_options_, BLOOM_FILTER_PREFIX_USEFUL), 0U);
+
+  iter->Seek("foo2");
+  ASSERT_OK(iter->status());
+  ASSERT_TRUE(!iter->Valid());
+  ASSERT_EQ(TestGetTickerCount(last_options_, BLOOM_FILTER_PREFIX_USEFUL), 1U);
+
+  iter->Seek("barbarbar");
+  ASSERT_OK(iter->status());
+  ASSERT_TRUE(iter->Valid());
+  ASSERT_EQ(iter->value().ToString(), "foo");
+  ASSERT_EQ(TestGetTickerCount(last_options_, BLOOM_FILTER_PREFIX_USEFUL), 1U);
+
+  iter->Seek("barfoofoo");
+  ASSERT_OK(iter->status());
+  ASSERT_TRUE(!iter->Valid());
+  ASSERT_EQ(TestGetTickerCount(last_options_, BLOOM_FILTER_PREFIX_USEFUL), 2U);
+
+  iter->Seek("foobarbar");
+  ASSERT_OK(iter->status());
+  ASSERT_TRUE(!iter->Valid());
+  ASSERT_EQ(TestGetTickerCount(last_options_, BLOOM_FILTER_PREFIX_USEFUL), 3U);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/status.cc b/src/rocksdb/util/status.cc
new file mode 100644
index 000000000..3b1ffde56
--- /dev/null
+++ b/src/rocksdb/util/status.cc
@@ -0,0 +1,143 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "rocksdb/status.h"
+#include <stdio.h>
+#ifdef OS_WIN
+#include <string.h>
+#endif
+#include <cstring>
+#include "port/port.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+const char* Status::CopyState(const char* state) {
+#ifdef OS_WIN
+  const size_t cch = std::strlen(state) + 1;  // +1 for the null terminator
+  char* result = new char[cch];
+  errno_t ret
+#if defined(_MSC_VER)
+    ;
+#else
+    __attribute__((__unused__));
+#endif
+  ret = strncpy_s(result, cch, state, cch - 1);
+  result[cch - 1] = '\0';
+  assert(ret == 0);
+  return result;
+#else
+  const size_t cch = std::strlen(state) + 1;  // +1 for the null terminator
+  return std::strncpy(new char[cch], state, cch);
+#endif
+}
+
+static const char* msgs[static_cast<int>(Status::kMaxSubCode)] = {
+    "",                                                   // kNone
+    "Timeout Acquiring Mutex",                            // kMutexTimeout
+    "Timeout waiting to lock key",                        // kLockTimeout
+    "Failed to acquire lock due to max_num_locks limit",  // kLockLimit
+    "No space left on device",                            // kNoSpace
+    "Deadlock",                                           // kDeadlock
+    "Stale file handle",                                  // kStaleFile
+    "Memory limit reached",                               // kMemoryLimit
+    "Space limit reached",                                // kSpaceLimit
+    "No such file or directory",                          // kPathNotFound
+    // KMergeOperandsInsufficientCapacity
+    "Insufficient capacity for merge operands",
+    // kManualCompactionPaused
+    "Manual compaction paused",
+};
+
+Status::Status(Code _code, SubCode _subcode, const Slice& msg,
+               const Slice& msg2)
+    : code_(_code), subcode_(_subcode), sev_(kNoError) {
+  assert(code_ != kOk);
+  assert(subcode_ != kMaxSubCode);
+  const size_t len1 = msg.size();
+  const size_t len2 = msg2.size();
+  const size_t size = len1 + (len2 ? (2 + len2) : 0);
+  char* const result = new char[size + 1];  // +1 for null terminator
+  memcpy(result, msg.data(), len1);
+  if (len2) {
+    result[len1] = ':';
+    result[len1 + 1] = ' ';
+    memcpy(result + len1 + 2, msg2.data(), len2);
+  }
+  result[size] = '\0';  // null terminator for C style string
+  state_ = result;
+}
+
+std::string Status::ToString() const {
+  char tmp[30];
+  const char* type;
+  switch (code_) {
+    case kOk:
+      return "OK";
+    case kNotFound:
+      type = "NotFound: ";
+      break;
+    case kCorruption:
+      type = "Corruption: ";
+      break;
+    case kNotSupported:
+      type = "Not implemented: ";
+      break;
+    case kInvalidArgument:
+      type = "Invalid argument: ";
+      break;
+    case kIOError:
+      type = "IO error: ";
+      break;
+    case kMergeInProgress:
+      type = "Merge in progress: ";
+      break;
+    case kIncomplete:
+      type = "Result incomplete: ";
+      break;
+    case kShutdownInProgress:
+      type = "Shutdown in progress: ";
+      break;
+    case kTimedOut:
+      type = "Operation timed out: ";
+      break;
+    case kAborted:
+      type = "Operation aborted: ";
+      break;
+    case kBusy:
+      type = "Resource busy: ";
+      break;
+    case kExpired:
+      type = "Operation expired: ";
+      break;
+    case kTryAgain:
+      type = "Operation failed. Try again.: ";
+      break;
+    case kColumnFamilyDropped:
+      type = "Column family dropped: ";
+      break;
+    default:
+      snprintf(tmp, sizeof(tmp), "Unknown code(%d): ",
+               static_cast<int>(code()));
+      type = tmp;
+      break;
+  }
+  std::string result(type);
+  if (subcode_ != kNone) {
+    uint32_t index = static_cast<int32_t>(subcode_);
+    assert(sizeof(msgs) > index);
+    result.append(msgs[index]);
+  }
+
+  if (state_ != nullptr) {
+    result.append(state_);
+  }
+  return result;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/stderr_logger.h b/src/rocksdb/util/stderr_logger.h
new file mode 100644
index 000000000..abf8f5701
--- /dev/null
+++ b/src/rocksdb/util/stderr_logger.h
@@ -0,0 +1,31 @@
+//  Copyright (c) 2016-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "rocksdb/env.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Prints logs to stderr for faster debugging
+class StderrLogger : public Logger {
+ public:
+  explicit StderrLogger(const InfoLogLevel log_level = InfoLogLevel::INFO_LEVEL)
+      : Logger(log_level) {}
+
+  // Brings overloaded Logv()s into scope so they're not hidden when we override
+  // a subset of them.
+  using Logger::Logv;
+
+  virtual void Logv(const char* format, va_list ap) override {
+    vfprintf(stderr, format, ap);
+    fprintf(stderr, "\n");
+  }
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/stop_watch.h b/src/rocksdb/util/stop_watch.h
new file mode 100644
index 000000000..ad4905960
--- /dev/null
+++ b/src/rocksdb/util/stop_watch.h
@@ -0,0 +1,118 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#pragma once
+#include "monitoring/statistics.h"
+#include "rocksdb/env.h"
+
+namespace ROCKSDB_NAMESPACE {
+// Auto-scoped.
+// Records the measure time into the corresponding histogram if statistics
+// is not nullptr. It is also saved into *elapsed if the pointer is not nullptr
+// and overwrite is true, it will be added to *elapsed if overwrite is false.
+class StopWatch {
+ public:
+  StopWatch(Env* const env, Statistics* statistics, const uint32_t hist_type,
+            uint64_t* elapsed = nullptr, bool overwrite = true,
+            bool delay_enabled = false)
+      : env_(env),
+        statistics_(statistics),
+        hist_type_(hist_type),
+        elapsed_(elapsed),
+        overwrite_(overwrite),
+        stats_enabled_(statistics &&
+                       statistics->get_stats_level() >=
+                           StatsLevel::kExceptTimers &&
+                       statistics->HistEnabledForType(hist_type)),
+        delay_enabled_(delay_enabled),
+        total_delay_(0),
+        delay_start_time_(0),
+        start_time_((stats_enabled_ || elapsed != nullptr) ? env->NowMicros()
+                                                           : 0) {}
+
+  ~StopWatch() {
+    if (elapsed_) {
+      if (overwrite_) {
+        *elapsed_ = env_->NowMicros() - start_time_;
+      } else {
+        *elapsed_ += env_->NowMicros() - start_time_;
+      }
+    }
+    if (elapsed_ && delay_enabled_) {
+      *elapsed_ -= total_delay_;
+    }
+    if (stats_enabled_) {
+      statistics_->reportTimeToHistogram(
+          hist_type_, (elapsed_ != nullptr)
+                          ? *elapsed_
+                          : (env_->NowMicros() - start_time_));
+    }
+  }
+
+  void DelayStart() {
+    // if delay_start_time_ is not 0, it means we are already tracking delay,
+    // so delay_start_time_ should not be overwritten
+    if (elapsed_ && delay_enabled_ && delay_start_time_ == 0) {
+      delay_start_time_ = env_->NowMicros();
+    }
+  }
+
+  void DelayStop() {
+    if (elapsed_ && delay_enabled_ && delay_start_time_ != 0) {
+      total_delay_ += env_->NowMicros() - delay_start_time_;
+    }
+    // reset to 0 means currently no delay is being tracked, so two consecutive
+    // calls to DelayStop will not increase total_delay_
+    delay_start_time_ = 0;
+  }
+
+  uint64_t GetDelay() const { return delay_enabled_ ? total_delay_ : 0; }
+
+  uint64_t start_time() const { return start_time_; }
+
+ private:
+  Env* const env_;
+  Statistics* statistics_;
+  const uint32_t hist_type_;
+  uint64_t* elapsed_;
+  bool overwrite_;
+  bool stats_enabled_;
+  bool delay_enabled_;
+  uint64_t total_delay_;
+  uint64_t delay_start_time_;
+  const uint64_t start_time_;
+};
+
+// a nano second precision stopwatch
+class StopWatchNano {
+ public:
+  explicit StopWatchNano(Env* const env, bool auto_start = false)
+      : env_(env), start_(0) {
+    if (auto_start) {
+      Start();
+    }
+  }
+
+  void Start() { start_ = env_->NowNanos(); }
+
+  uint64_t ElapsedNanos(bool reset = false) {
+    auto now = env_->NowNanos();
+    auto elapsed = now - start_;
+    if (reset) {
+      start_ = now;
+    }
+    return elapsed;
+  }
+
+  uint64_t ElapsedNanosSafe(bool reset = false) {
+    return (env_ != nullptr) ? ElapsedNanos(reset) : 0U;
+  }
+
+ private:
+  Env* const env_;
+  uint64_t start_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/string_util.cc b/src/rocksdb/util/string_util.cc
new file mode 100644
index 000000000..bb234f239
--- /dev/null
+++ b/src/rocksdb/util/string_util.cc
@@ -0,0 +1,409 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#include "util/string_util.h"
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <algorithm>
+#include <cinttypes>
+#include <cmath>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+#include "port/port.h"
+#include "port/sys_time.h"
+#include "rocksdb/slice.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+const std::string kNullptrString = "nullptr";
+
+std::vector<std::string> StringSplit(const std::string& arg, char delim) {
+  std::vector<std::string> splits;
+  std::stringstream ss(arg);
+  std::string item;
+  while (std::getline(ss, item, delim)) {
+    splits.push_back(item);
+  }
+  return splits;
+}
+
+// for micros < 10ms, print "XX us".
+// for micros < 10sec, print "XX ms".
+// for micros >= 10 sec, print "XX sec".
+// for micros <= 1 hour, print Y:X M:S".
+// for micros > 1 hour, print Z:Y:X H:M:S".
+int AppendHumanMicros(uint64_t micros, char* output, int len,
+                      bool fixed_format) {
+  if (micros < 10000 && !fixed_format) {
+    return snprintf(output, len, "%" PRIu64 " us", micros);
+  } else if (micros < 10000000 && !fixed_format) {
+    return snprintf(output, len, "%.3lf ms",
+                    static_cast<double>(micros) / 1000);
+  } else if (micros < 1000000l * 60 && !fixed_format) {
+    return snprintf(output, len, "%.3lf sec",
+                    static_cast<double>(micros) / 1000000);
+  } else if (micros < 1000000ll * 60 * 60 && !fixed_format) {
+    return snprintf(output, len, "%02" PRIu64 ":%05.3f M:S",
+                    micros / 1000000 / 60,
+                    static_cast<double>(micros % 60000000) / 1000000);
+  } else {
+    return snprintf(output, len, "%02" PRIu64 ":%02" PRIu64 ":%05.3f H:M:S",
+                    micros / 1000000 / 3600, (micros / 1000000 / 60) % 60,
+                    static_cast<double>(micros % 60000000) / 1000000);
+  }
+}
+
+// for sizes >=10TB, print "XXTB"
+// for sizes >=10GB, print "XXGB"
+// etc.
+// append file size summary to output and return the len
+int AppendHumanBytes(uint64_t bytes, char* output, int len) {
+  const uint64_t ull10 = 10;
+  if (bytes >= ull10 << 40) {
+    return snprintf(output, len, "%" PRIu64 "TB", bytes >> 40);
+  } else if (bytes >= ull10 << 30) {
+    return snprintf(output, len, "%" PRIu64 "GB", bytes >> 30);
+  } else if (bytes >= ull10 << 20) {
+    return snprintf(output, len, "%" PRIu64 "MB", bytes >> 20);
+  } else if (bytes >= ull10 << 10) {
+    return snprintf(output, len, "%" PRIu64 "KB", bytes >> 10);
+  } else {
+    return snprintf(output, len, "%" PRIu64 "B", bytes);
+  }
+}
+
+void AppendNumberTo(std::string* str, uint64_t num) {
+  char buf[30];
+  snprintf(buf, sizeof(buf), "%" PRIu64, num);
+  str->append(buf);
+}
+
+void AppendEscapedStringTo(std::string* str, const Slice& value) {
+  for (size_t i = 0; i < value.size(); i++) {
+    char c = value[i];
+    if (c >= ' ' && c <= '~') {
+      str->push_back(c);
+    } else {
+      char buf[10];
+      snprintf(buf, sizeof(buf), "\\x%02x",
+               static_cast<unsigned int>(c) & 0xff);
+      str->append(buf);
+    }
+  }
+}
+
+std::string NumberToString(uint64_t num) {
+  std::string r;
+  AppendNumberTo(&r, num);
+  return r;
+}
+
+std::string NumberToHumanString(int64_t num) {
+  char buf[19];
+  int64_t absnum = num < 0 ? -num : num;
+  if (absnum < 10000) {
+    snprintf(buf, sizeof(buf), "%" PRIi64, num);
+  } else if (absnum < 10000000) {
+    snprintf(buf, sizeof(buf), "%" PRIi64 "K", num / 1000);
+  } else if (absnum < 10000000000LL) {
+    snprintf(buf, sizeof(buf), "%" PRIi64 "M", num / 1000000);
+  } else {
+    snprintf(buf, sizeof(buf), "%" PRIi64 "G", num / 1000000000);
+  }
+  return std::string(buf);
+}
+
+std::string BytesToHumanString(uint64_t bytes) {
+  const char* size_name[] = {"KB", "MB", "GB", "TB"};
+  double final_size = static_cast<double>(bytes);
+  size_t size_idx;
+
+  // always start with KB
+  final_size /= 1024;
+  size_idx = 0;
+
+  while (size_idx < 3 && final_size >= 1024) {
+    final_size /= 1024;
+    size_idx++;
+  }
+
+  char buf[20];
+  snprintf(buf, sizeof(buf), "%.2f %s", final_size, size_name[size_idx]);
+  return std::string(buf);
+}
+
+std::string TimeToHumanString(int unixtime) {
+  char time_buffer[80];
+  time_t rawtime = unixtime;
+  struct tm tInfo;
+  struct tm* timeinfo = localtime_r(&rawtime, &tInfo);
+  assert(timeinfo == &tInfo);
+  strftime(time_buffer, 80, "%c", timeinfo);
+  return std::string(time_buffer);
+}
+
+std::string EscapeString(const Slice& value) {
+  std::string r;
+  AppendEscapedStringTo(&r, value);
+  return r;
+}
+
+bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
+  uint64_t v = 0;
+  int digits = 0;
+  while (!in->empty()) {
+    char c = (*in)[0];
+    if (c >= '0' && c <= '9') {
+      ++digits;
+      const unsigned int delta = (c - '0');
+      static const uint64_t kMaxUint64 = ~static_cast<uint64_t>(0);
+      if (v > kMaxUint64 / 10 ||
+          (v == kMaxUint64 / 10 && delta > kMaxUint64 % 10)) {
+        // Overflow
+        return false;
+      }
+      v = (v * 10) + delta;
+      in->remove_prefix(1);
+    } else {
+      break;
+    }
+  }
+  *val = v;
+  return (digits > 0);
+}
+
+bool isSpecialChar(const char c) {
+  if (c == '\\' || c == '#' || c == ':' || c == '\r' || c == '\n') {
+    return true;
+  }
+  return false;
+}
+
+namespace {
+using CharMap = std::pair<char, char>;
+}
+
+char UnescapeChar(const char c) {
+  static const CharMap convert_map[] = {{'r', '\r'}, {'n', '\n'}};
+
+  auto iter = std::find_if(std::begin(convert_map), std::end(convert_map),
+                           [c](const CharMap& p) { return p.first == c; });
+
+  if (iter == std::end(convert_map)) {
+    return c;
+  }
+  return iter->second;
+}
+
+char EscapeChar(const char c) {
+  static const CharMap convert_map[] = {{'\n', 'n'}, {'\r', 'r'}};
+
+  auto iter = std::find_if(std::begin(convert_map), std::end(convert_map),
+                           [c](const CharMap& p) { return p.first == c; });
+
+  if (iter == std::end(convert_map)) {
+    return c;
+  }
+  return iter->second;
+}
+
+std::string EscapeOptionString(const std::string& raw_string) {
+  std::string output;
+  for (auto c : raw_string) {
+    if (isSpecialChar(c)) {
+      output += '\\';
+      output += EscapeChar(c);
+    } else {
+      output += c;
+    }
+  }
+
+  return output;
+}
+
+std::string UnescapeOptionString(const std::string& escaped_string) {
+  bool escaped = false;
+  std::string output;
+
+  for (auto c : escaped_string) {
+    if (escaped) {
+      output += UnescapeChar(c);
+      escaped = false;
+    } else {
+      if (c == '\\') {
+        escaped = true;
+        continue;
+      }
+      output += c;
+    }
+  }
+  return output;
+}
+
+std::string trim(const std::string& str) {
+  if (str.empty()) return std::string();
+  size_t start = 0;
+  size_t end = str.size() - 1;
+  while (isspace(str[start]) != 0 && start < end) {
+    ++start;
+  }
+  while (isspace(str[end]) != 0 && start < end) {
+    --end;
+  }
+  if (start <= end) {
+    return str.substr(start, end - start + 1);
+  }
+  return std::string();
+}
+
+#ifndef ROCKSDB_LITE
+
+bool ParseBoolean(const std::string& type, const std::string& value) {
+  if (value == "true" || value == "1") {
+    return true;
+  } else if (value == "false" || value == "0") {
+    return false;
+  }
+  throw std::invalid_argument(type);
+}
+
+uint32_t ParseUint32(const std::string& value) {
+  uint64_t num = ParseUint64(value);
+  if ((num >> 32LL) == 0) {
+    return static_cast<uint32_t>(num);
+  } else {
+    throw std::out_of_range(value);
+  }
+}
+
+int32_t ParseInt32(const std::string& value) {
+  int64_t num = ParseInt64(value);
+  if (num <= port::kMaxInt32 && num >= port::kMinInt32) {
+    return static_cast<int32_t>(num);
+  } else {
+    throw std::out_of_range(value);
+  }
+}
+
+#endif
+
+uint64_t ParseUint64(const std::string& value) {
+  size_t endchar;
+#ifndef CYGWIN
+  uint64_t num = std::stoull(value.c_str(), &endchar);
+#else
+  char* endptr;
+  uint64_t num = std::strtoul(value.c_str(), &endptr, 0);
+  endchar = endptr - value.c_str();
+#endif
+
+  if (endchar < value.length()) {
+    char c = value[endchar];
+    if (c == 'k' || c == 'K')
+      num <<= 10LL;
+    else if (c == 'm' || c == 'M')
+      num <<= 20LL;
+    else if (c == 'g' || c == 'G')
+      num <<= 30LL;
+    else if (c == 't' || c == 'T')
+      num <<= 40LL;
+  }
+
+  return num;
+}
+
+int64_t ParseInt64(const std::string& value) {
+  size_t endchar;
+#ifndef CYGWIN
+  int64_t num = std::stoll(value.c_str(), &endchar);
+#else
+  char* endptr;
+  int64_t num = std::strtoll(value.c_str(), &endptr, 0);
+  endchar = endptr - value.c_str();
+#endif
+
+  if (endchar < value.length()) {
+    char c = value[endchar];
+    if (c == 'k' || c == 'K')
+      num <<= 10LL;
+    else if (c == 'm' || c == 'M')
+      num <<= 20LL;
+    else if (c == 'g' || c == 'G')
+      num <<= 30LL;
+    else if (c == 't' || c == 'T')
+      num <<= 40LL;
+  }
+
+  return num;
+}
+
+int ParseInt(const std::string& value) {
+  size_t endchar;
+#ifndef CYGWIN
+  int num = std::stoi(value.c_str(), &endchar);
+#else
+  char* endptr;
+  int num = std::strtoul(value.c_str(), &endptr, 0);
+  endchar = endptr - value.c_str();
+#endif
+
+  if (endchar < value.length()) {
+    char c = value[endchar];
+    if (c == 'k' || c == 'K')
+      num <<= 10;
+    else if (c == 'm' || c == 'M')
+      num <<= 20;
+    else if (c == 'g' || c == 'G')
+      num <<= 30;
+  }
+
+  return num;
+}
+
+double ParseDouble(const std::string& value) {
+#ifndef CYGWIN
+  return std::stod(value);
+#else
+  return std::strtod(value.c_str(), 0);
+#endif
+}
+
+size_t ParseSizeT(const std::string& value) {
+  return static_cast<size_t>(ParseUint64(value));
+}
+
+std::vector<int> ParseVectorInt(const std::string& value) {
+  std::vector<int> result;
+  size_t start = 0;
+  while (start < value.size()) {
+    size_t end = value.find(':', start);
+    if (end == std::string::npos) {
+      result.push_back(ParseInt(value.substr(start)));
+      break;
+    } else {
+      result.push_back(ParseInt(value.substr(start, end - start)));
+      start = end + 1;
+    }
+  }
+  return result;
+}
+
+bool SerializeIntVector(const std::vector<int>& vec, std::string* value) {
+  *value = "";
+  for (size_t i = 0; i < vec.size(); ++i) {
+    if (i > 0) {
+      *value += ":";
+    }
+    *value += ToString(vec[i]);
+  }
+  return true;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/string_util.h b/src/rocksdb/util/string_util.h
new file mode 100644
index 000000000..a761be66c
--- /dev/null
+++ b/src/rocksdb/util/string_util.h
@@ -0,0 +1,138 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+
+#pragma once
+
+#include <sstream>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class Slice;
+
+extern std::vector<std::string> StringSplit(const std::string& arg, char delim);
+
+template <typename T>
+inline std::string ToString(T value) {
+#if !(defined OS_ANDROID) && !(defined CYGWIN) && !(defined OS_FREEBSD)
+  return std::to_string(value);
+#else
+  // Andorid or cygwin doesn't support all of C++11, std::to_string() being
+  // one of the not supported features.
+  std::ostringstream os;
+  os << value;
+  return os.str();
+#endif
+}
+
+// Append a human-readable printout of "num" to *str
+extern void AppendNumberTo(std::string* str, uint64_t num);
+
+// Append a human-readable printout of "value" to *str.
+// Escapes any non-printable characters found in "value".
+extern void AppendEscapedStringTo(std::string* str, const Slice& value);
+
+// Return a string printout of "num"
+extern std::string NumberToString(uint64_t num);
+
+// Return a human-readable version of num.
+// for num >= 10.000, prints "xxK"
+// for num >= 10.000.000, prints "xxM"
+// for num >= 10.000.000.000, prints "xxG"
+extern std::string NumberToHumanString(int64_t num);
+
+// Return a human-readable version of bytes
+// ex: 1048576 -> 1.00 GB
+extern std::string BytesToHumanString(uint64_t bytes);
+
+// Return a human-readable version of unix time
+// ex: 1562116015 -> "Tue Jul  2 18:06:55 2019"
+extern std::string TimeToHumanString(int unixtime);
+
+// Append a human-readable time in micros.
+int AppendHumanMicros(uint64_t micros, char* output, int len,
+                      bool fixed_format);
+
+// Append a human-readable size in bytes
+int AppendHumanBytes(uint64_t bytes, char* output, int len);
+
+// Return a human-readable version of "value".
+// Escapes any non-printable characters found in "value".
+extern std::string EscapeString(const Slice& value);
+
+// Parse a human-readable number from "*in" into *value.  On success,
+// advances "*in" past the consumed number and sets "*val" to the
+// numeric value.  Otherwise, returns false and leaves *in in an
+// unspecified state.
+extern bool ConsumeDecimalNumber(Slice* in, uint64_t* val);
+
+// Returns true if the input char "c" is considered as a special character
+// that will be escaped when EscapeOptionString() is called.
+//
+// @param c the input char
+// @return true if the input char "c" is considered as a special character.
+// @see EscapeOptionString
+bool isSpecialChar(const char c);
+
+// If the input char is an escaped char, it will return the its
+// associated raw-char.  Otherwise, the function will simply return
+// the original input char.
+char UnescapeChar(const char c);
+
+// If the input char is a control char, it will return the its
+// associated escaped char.  Otherwise, the function will simply return
+// the original input char.
+char EscapeChar(const char c);
+
+// Converts a raw string to an escaped string.  Escaped-characters are
+// defined via the isSpecialChar() function.  When a char in the input
+// string "raw_string" is classified as a special characters, then it
+// will be prefixed by '\' in the output.
+//
+// It's inverse function is UnescapeOptionString().
+// @param raw_string the input string
+// @return the '\' escaped string of the input "raw_string"
+// @see isSpecialChar, UnescapeOptionString
+std::string EscapeOptionString(const std::string& raw_string);
+
+// The inverse function of EscapeOptionString.  It converts
+// an '\' escaped string back to a raw string.
+//
+// @param escaped_string the input '\' escaped string
+// @return the raw string of the input "escaped_string"
+std::string UnescapeOptionString(const std::string& escaped_string);
+
+std::string trim(const std::string& str);
+
+#ifndef ROCKSDB_LITE
+bool ParseBoolean(const std::string& type, const std::string& value);
+
+uint32_t ParseUint32(const std::string& value);
+
+int32_t ParseInt32(const std::string& value);
+#endif
+
+uint64_t ParseUint64(const std::string& value);
+
+int ParseInt(const std::string& value);
+
+int64_t ParseInt64(const std::string& value);
+
+double ParseDouble(const std::string& value);
+
+size_t ParseSizeT(const std::string& value);
+
+std::vector<int> ParseVectorInt(const std::string& value);
+
+bool SerializeIntVector(const std::vector<int>& vec, std::string* value);
+
+extern const std::string kNullptrString;
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/thread_list_test.cc b/src/rocksdb/util/thread_list_test.cc
new file mode 100644
index 000000000..44c3ebc99
--- /dev/null
+++ b/src/rocksdb/util/thread_list_test.cc
@@ -0,0 +1,352 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <mutex>
+#include <condition_variable>
+
+#include "monitoring/thread_status_updater.h"
+#include "rocksdb/db.h"
+#include "test_util/testharness.h"
+
+#ifdef ROCKSDB_USING_THREAD_STATUS
+
+namespace ROCKSDB_NAMESPACE {
+
+class SimulatedBackgroundTask {
+ public:
+  SimulatedBackgroundTask(
+      const void* db_key, const std::string& db_name,
+      const void* cf_key, const std::string& cf_name,
+      const ThreadStatus::OperationType operation_type =
+          ThreadStatus::OP_UNKNOWN,
+      const ThreadStatus::StateType state_type =
+          ThreadStatus::STATE_UNKNOWN)
+      : db_key_(db_key), db_name_(db_name),
+        cf_key_(cf_key), cf_name_(cf_name),
+        operation_type_(operation_type), state_type_(state_type),
+        should_run_(true), running_count_(0) {
+    Env::Default()->GetThreadStatusUpdater()->NewColumnFamilyInfo(
+        db_key_, db_name_, cf_key_, cf_name_);
+  }
+
+  ~SimulatedBackgroundTask() {
+    Env::Default()->GetThreadStatusUpdater()->EraseDatabaseInfo(db_key_);
+  }
+
+  void Run() {
+    std::unique_lock<std::mutex> l(mutex_);
+    running_count_++;
+    Env::Default()->GetThreadStatusUpdater()->SetColumnFamilyInfoKey(cf_key_);
+    Env::Default()->GetThreadStatusUpdater()->SetThreadOperation(
+        operation_type_);
+    Env::Default()->GetThreadStatusUpdater()->SetThreadState(state_type_);
+    while (should_run_) {
+      bg_cv_.wait(l);
+    }
+    Env::Default()->GetThreadStatusUpdater()->ClearThreadState();
+    Env::Default()->GetThreadStatusUpdater()->ClearThreadOperation();
+    Env::Default()->GetThreadStatusUpdater()->SetColumnFamilyInfoKey(nullptr);
+    running_count_--;
+    bg_cv_.notify_all();
+  }
+
+  void FinishAllTasks() {
+    std::unique_lock<std::mutex> l(mutex_);
+    should_run_ = false;
+    bg_cv_.notify_all();
+  }
+
+  void WaitUntilScheduled(int job_count, Env* env) {
+    while (running_count_ < job_count) {
+      env->SleepForMicroseconds(1000);
+    }
+  }
+
+  void WaitUntilDone() {
+    std::unique_lock<std::mutex> l(mutex_);
+    while (running_count_ > 0) {
+      bg_cv_.wait(l);
+    }
+  }
+
+  static void DoSimulatedTask(void* arg) {
+    reinterpret_cast<SimulatedBackgroundTask*>(arg)->Run();
+  }
+
+ private:
+  const void* db_key_;
+  const std::string db_name_;
+  const void* cf_key_;
+  const std::string cf_name_;
+  const ThreadStatus::OperationType operation_type_;
+  const ThreadStatus::StateType state_type_;
+  std::mutex mutex_;
+  std::condition_variable bg_cv_;
+  bool should_run_;
+  std::atomic<int> running_count_;
+};
+
+class ThreadListTest : public testing::Test {
+ public:
+  ThreadListTest() {
+  }
+};
+
+TEST_F(ThreadListTest, GlobalTables) {
+  // verify the global tables for operations and states are properly indexed.
+  for (int type = 0; type != ThreadStatus::NUM_OP_TYPES; ++type) {
+    ASSERT_EQ(global_operation_table[type].type, type);
+    ASSERT_EQ(global_operation_table[type].name,
+              ThreadStatus::GetOperationName(
+                  ThreadStatus::OperationType(type)));
+  }
+
+  for (int type = 0; type != ThreadStatus::NUM_STATE_TYPES; ++type) {
+    ASSERT_EQ(global_state_table[type].type, type);
+    ASSERT_EQ(global_state_table[type].name,
+              ThreadStatus::GetStateName(
+                  ThreadStatus::StateType(type)));
+  }
+
+  for (int stage = 0; stage != ThreadStatus::NUM_OP_STAGES; ++stage) {
+    ASSERT_EQ(global_op_stage_table[stage].stage, stage);
+    ASSERT_EQ(global_op_stage_table[stage].name,
+              ThreadStatus::GetOperationStageName(
+                  ThreadStatus::OperationStage(stage)));
+  }
+}
+
+TEST_F(ThreadListTest, SimpleColumnFamilyInfoTest) {
+  Env* env = Env::Default();
+  const int kHighPriorityThreads = 3;
+  const int kLowPriorityThreads = 5;
+  const int kSimulatedHighPriThreads = kHighPriorityThreads - 1;
+  const int kSimulatedLowPriThreads = kLowPriorityThreads / 3;
+  env->SetBackgroundThreads(kHighPriorityThreads, Env::HIGH);
+  env->SetBackgroundThreads(kLowPriorityThreads, Env::LOW);
+
+  SimulatedBackgroundTask running_task(
+      reinterpret_cast<void*>(1234), "running",
+      reinterpret_cast<void*>(5678), "pikachu");
+
+  for (int test = 0; test < kSimulatedHighPriThreads; ++test) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &running_task, Env::Priority::HIGH);
+  }
+  for (int test = 0; test < kSimulatedLowPriThreads; ++test) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &running_task, Env::Priority::LOW);
+  }
+  running_task.WaitUntilScheduled(
+      kSimulatedHighPriThreads + kSimulatedLowPriThreads, env);
+
+  std::vector<ThreadStatus> thread_list;
+
+  // Verify the number of running threads in each pool.
+  env->GetThreadList(&thread_list);
+  int running_count[ThreadStatus::NUM_THREAD_TYPES] = {0};
+  for (auto thread_status : thread_list) {
+    if (thread_status.cf_name == "pikachu" &&
+        thread_status.db_name == "running") {
+      running_count[thread_status.thread_type]++;
+    }
+  }
+  ASSERT_EQ(
+      running_count[ThreadStatus::HIGH_PRIORITY],
+      kSimulatedHighPriThreads);
+  ASSERT_EQ(
+      running_count[ThreadStatus::LOW_PRIORITY],
+      kSimulatedLowPriThreads);
+  ASSERT_EQ(
+      running_count[ThreadStatus::USER], 0);
+
+  running_task.FinishAllTasks();
+  running_task.WaitUntilDone();
+
+  // Verify none of the threads are running
+  env->GetThreadList(&thread_list);
+
+  for (int i = 0; i < ThreadStatus::NUM_THREAD_TYPES; ++i) {
+    running_count[i] = 0;
+  }
+  for (auto thread_status : thread_list) {
+    if (thread_status.cf_name == "pikachu" &&
+        thread_status.db_name == "running") {
+      running_count[thread_status.thread_type]++;
+    }
+  }
+
+  ASSERT_EQ(
+      running_count[ThreadStatus::HIGH_PRIORITY], 0);
+  ASSERT_EQ(
+      running_count[ThreadStatus::LOW_PRIORITY], 0);
+  ASSERT_EQ(
+      running_count[ThreadStatus::USER], 0);
+}
+
+namespace {
+  void UpdateStatusCounts(
+      const std::vector<ThreadStatus>& thread_list,
+      int operation_counts[], int state_counts[]) {
+    for (auto thread_status : thread_list) {
+      operation_counts[thread_status.operation_type]++;
+      state_counts[thread_status.state_type]++;
+    }
+  }
+
+  void VerifyAndResetCounts(
+      const int correct_counts[], int collected_counts[], int size) {
+    for (int i = 0; i < size; ++i) {
+      ASSERT_EQ(collected_counts[i], correct_counts[i]);
+      collected_counts[i] = 0;
+    }
+  }
+
+  void UpdateCount(
+      int operation_counts[], int from_event, int to_event, int amount) {
+    operation_counts[from_event] -= amount;
+    operation_counts[to_event] += amount;
+  }
+}  // namespace
+
+TEST_F(ThreadListTest, SimpleEventTest) {
+  Env* env = Env::Default();
+
+  // simulated tasks
+  const int kFlushWriteTasks = 3;
+  SimulatedBackgroundTask flush_write_task(
+      reinterpret_cast<void*>(1234), "running",
+      reinterpret_cast<void*>(5678), "pikachu",
+      ThreadStatus::OP_FLUSH);
+
+  const int kCompactionWriteTasks = 4;
+  SimulatedBackgroundTask compaction_write_task(
+      reinterpret_cast<void*>(1234), "running",
+      reinterpret_cast<void*>(5678), "pikachu",
+      ThreadStatus::OP_COMPACTION);
+
+  const int kCompactionReadTasks = 5;
+  SimulatedBackgroundTask compaction_read_task(
+      reinterpret_cast<void*>(1234), "running",
+      reinterpret_cast<void*>(5678), "pikachu",
+      ThreadStatus::OP_COMPACTION);
+
+  const int kCompactionWaitTasks = 6;
+  SimulatedBackgroundTask compaction_wait_task(
+      reinterpret_cast<void*>(1234), "running",
+      reinterpret_cast<void*>(5678), "pikachu",
+      ThreadStatus::OP_COMPACTION);
+
+  // setup right answers
+  int correct_operation_counts[ThreadStatus::NUM_OP_TYPES] = {0};
+  correct_operation_counts[ThreadStatus::OP_FLUSH] =
+      kFlushWriteTasks;
+  correct_operation_counts[ThreadStatus::OP_COMPACTION] =
+      kCompactionWriteTasks + kCompactionReadTasks + kCompactionWaitTasks;
+
+  env->SetBackgroundThreads(
+      correct_operation_counts[ThreadStatus::OP_FLUSH], Env::HIGH);
+  env->SetBackgroundThreads(
+      correct_operation_counts[ThreadStatus::OP_COMPACTION], Env::LOW);
+
+  // schedule the simulated tasks
+  for (int t = 0; t < kFlushWriteTasks; ++t) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &flush_write_task, Env::Priority::HIGH);
+  }
+  flush_write_task.WaitUntilScheduled(kFlushWriteTasks, env);
+
+  for (int t = 0; t < kCompactionWriteTasks; ++t) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &compaction_write_task, Env::Priority::LOW);
+  }
+  compaction_write_task.WaitUntilScheduled(kCompactionWriteTasks, env);
+
+  for (int t = 0; t < kCompactionReadTasks; ++t) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &compaction_read_task, Env::Priority::LOW);
+  }
+  compaction_read_task.WaitUntilScheduled(kCompactionReadTasks, env);
+
+  for (int t = 0; t < kCompactionWaitTasks; ++t) {
+    env->Schedule(&SimulatedBackgroundTask::DoSimulatedTask,
+        &compaction_wait_task, Env::Priority::LOW);
+  }
+  compaction_wait_task.WaitUntilScheduled(kCompactionWaitTasks, env);
+
+  // verify the thread-status
+  int operation_counts[ThreadStatus::NUM_OP_TYPES] = {0};
+  int state_counts[ThreadStatus::NUM_STATE_TYPES] = {0};
+
+  std::vector<ThreadStatus> thread_list;
+  env->GetThreadList(&thread_list);
+  UpdateStatusCounts(thread_list, operation_counts, state_counts);
+  VerifyAndResetCounts(correct_operation_counts, operation_counts,
+                       ThreadStatus::NUM_OP_TYPES);
+
+  // terminate compaction-wait tasks and see if the thread-status
+  // reflects this update
+  compaction_wait_task.FinishAllTasks();
+  compaction_wait_task.WaitUntilDone();
+  UpdateCount(correct_operation_counts, ThreadStatus::OP_COMPACTION,
+              ThreadStatus::OP_UNKNOWN, kCompactionWaitTasks);
+
+  env->GetThreadList(&thread_list);
+  UpdateStatusCounts(thread_list, operation_counts, state_counts);
+  VerifyAndResetCounts(correct_operation_counts, operation_counts,
+                       ThreadStatus::NUM_OP_TYPES);
+
+  // terminate flush-write tasks and see if the thread-status
+  // reflects this update
+  flush_write_task.FinishAllTasks();
+  flush_write_task.WaitUntilDone();
+  UpdateCount(correct_operation_counts, ThreadStatus::OP_FLUSH,
+              ThreadStatus::OP_UNKNOWN, kFlushWriteTasks);
+
+  env->GetThreadList(&thread_list);
+  UpdateStatusCounts(thread_list, operation_counts, state_counts);
+  VerifyAndResetCounts(correct_operation_counts, operation_counts,
+                       ThreadStatus::NUM_OP_TYPES);
+
+  // terminate compaction-write tasks and see if the thread-status
+  // reflects this update
+  compaction_write_task.FinishAllTasks();
+  compaction_write_task.WaitUntilDone();
+  UpdateCount(correct_operation_counts, ThreadStatus::OP_COMPACTION,
+              ThreadStatus::OP_UNKNOWN, kCompactionWriteTasks);
+
+  env->GetThreadList(&thread_list);
+  UpdateStatusCounts(thread_list, operation_counts, state_counts);
+  VerifyAndResetCounts(correct_operation_counts, operation_counts,
+                       ThreadStatus::NUM_OP_TYPES);
+
+  // terminate compaction-write tasks and see if the thread-status
+  // reflects this update
+  compaction_read_task.FinishAllTasks();
+  compaction_read_task.WaitUntilDone();
+  UpdateCount(correct_operation_counts, ThreadStatus::OP_COMPACTION,
+              ThreadStatus::OP_UNKNOWN, kCompactionReadTasks);
+
+  env->GetThreadList(&thread_list);
+  UpdateStatusCounts(thread_list, operation_counts, state_counts);
+  VerifyAndResetCounts(correct_operation_counts, operation_counts,
+                       ThreadStatus::NUM_OP_TYPES);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+
+#else
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return 0;
+}
+
+#endif  // ROCKSDB_USING_THREAD_STATUS
diff --git a/src/rocksdb/util/thread_local.cc b/src/rocksdb/util/thread_local.cc
new file mode 100644
index 000000000..9fa16f609
--- /dev/null
+++ b/src/rocksdb/util/thread_local.cc
@@ -0,0 +1,554 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/thread_local.h"
+#include "util/mutexlock.h"
+#include "port/likely.h"
+#include <stdlib.h>
+
+namespace ROCKSDB_NAMESPACE {
+
+struct Entry {
+  Entry() : ptr(nullptr) {}
+  Entry(const Entry& e) : ptr(e.ptr.load(std::memory_order_relaxed)) {}
+  std::atomic<void*> ptr;
+};
+
+class StaticMeta;
+
+// This is the structure that is declared as "thread_local" storage.
+// The vector keep list of atomic pointer for all instances for "current"
+// thread. The vector is indexed by an Id that is unique in process and
+// associated with one ThreadLocalPtr instance. The Id is assigned by a
+// global StaticMeta singleton. So if we instantiated 3 ThreadLocalPtr
+// instances, each thread will have a ThreadData with a vector of size 3:
+//     ---------------------------------------------------
+//     |          | instance 1 | instance 2 | instnace 3 |
+//     ---------------------------------------------------
+//     | thread 1 |    void*   |    void*   |    void*   | <- ThreadData
+//     ---------------------------------------------------
+//     | thread 2 |    void*   |    void*   |    void*   | <- ThreadData
+//     ---------------------------------------------------
+//     | thread 3 |    void*   |    void*   |    void*   | <- ThreadData
+//     ---------------------------------------------------
+struct ThreadData {
+  explicit ThreadData(ThreadLocalPtr::StaticMeta* _inst)
+    : entries(),
+      next(nullptr),
+      prev(nullptr),
+      inst(_inst) {}
+  std::vector<Entry> entries;
+  ThreadData* next;
+  ThreadData* prev;
+  ThreadLocalPtr::StaticMeta* inst;
+};
+
+class ThreadLocalPtr::StaticMeta {
+public:
+  StaticMeta();
+
+  // Return the next available Id
+  uint32_t GetId();
+  // Return the next available Id without claiming it
+  uint32_t PeekId() const;
+  // Return the given Id back to the free pool. This also triggers
+  // UnrefHandler for associated pointer value (if not NULL) for all threads.
+  void ReclaimId(uint32_t id);
+
+  // Return the pointer value for the given id for the current thread.
+  void* Get(uint32_t id) const;
+  // Reset the pointer value for the given id for the current thread.
+  void Reset(uint32_t id, void* ptr);
+  // Atomically swap the supplied ptr and return the previous value
+  void* Swap(uint32_t id, void* ptr);
+  // Atomically compare and swap the provided value only if it equals
+  // to expected value.
+  bool CompareAndSwap(uint32_t id, void* ptr, void*& expected);
+  // Reset all thread local data to replacement, and return non-nullptr
+  // data for all existing threads
+  void Scrape(uint32_t id, autovector<void*>* ptrs, void* const replacement);
+  // Update res by applying func on each thread-local value. Holds a lock that
+  // prevents unref handler from running during this call, but clients must
+  // still provide external synchronization since the owning thread can
+  // access the values without internal locking, e.g., via Get() and Reset().
+  void Fold(uint32_t id, FoldFunc func, void* res);
+
+  // Register the UnrefHandler for id
+  void SetHandler(uint32_t id, UnrefHandler handler);
+
+  // protect inst, next_instance_id_, free_instance_ids_, head_,
+  // ThreadData.entries
+  //
+  // Note that here we prefer function static variable instead of the usual
+  // global static variable.  The reason is that c++ destruction order of
+  // static variables in the reverse order of their construction order.
+  // However, C++ does not guarantee any construction order when global
+  // static variables are defined in different files, while the function
+  // static variables are initialized when their function are first called.
+  // As a result, the construction order of the function static variables
+  // can be controlled by properly invoke their first function calls in
+  // the right order.
+  //
+  // For instance, the following function contains a function static
+  // variable.  We place a dummy function call of this inside
+  // Env::Default() to ensure the construction order of the construction
+  // order.
+  static port::Mutex* Mutex();
+
+  // Returns the member mutex of the current StaticMeta.  In general,
+  // Mutex() should be used instead of this one.  However, in case where
+  // the static variable inside Instance() goes out of scope, MemberMutex()
+  // should be used.  One example is OnThreadExit() function.
+  port::Mutex* MemberMutex() { return &mutex_; }
+
+private:
+  // Get UnrefHandler for id with acquiring mutex
+  // REQUIRES: mutex locked
+  UnrefHandler GetHandler(uint32_t id);
+
+  // Triggered before a thread terminates
+  static void OnThreadExit(void* ptr);
+
+  // Add current thread's ThreadData to the global chain
+  // REQUIRES: mutex locked
+  void AddThreadData(ThreadData* d);
+
+  // Remove current thread's ThreadData from the global chain
+  // REQUIRES: mutex locked
+  void RemoveThreadData(ThreadData* d);
+
+  static ThreadData* GetThreadLocal();
+
+  uint32_t next_instance_id_;
+  // Used to recycle Ids in case ThreadLocalPtr is instantiated and destroyed
+  // frequently. This also prevents it from blowing up the vector space.
+  autovector<uint32_t> free_instance_ids_;
+  // Chain all thread local structure together. This is necessary since
+  // when one ThreadLocalPtr gets destroyed, we need to loop over each
+  // thread's version of pointer corresponding to that instance and
+  // call UnrefHandler for it.
+  ThreadData head_;
+
+  std::unordered_map<uint32_t, UnrefHandler> handler_map_;
+
+  // The private mutex.  Developers should always use Mutex() instead of
+  // using this variable directly.
+  port::Mutex mutex_;
+#ifdef ROCKSDB_SUPPORT_THREAD_LOCAL
+  // Thread local storage
+  static __thread ThreadData* tls_;
+#endif
+
+  // Used to make thread exit trigger possible if !defined(OS_MACOSX).
+  // Otherwise, used to retrieve thread data.
+  pthread_key_t pthread_key_;
+};
+
+
+#ifdef ROCKSDB_SUPPORT_THREAD_LOCAL
+__thread ThreadData* ThreadLocalPtr::StaticMeta::tls_ = nullptr;
+#endif
+
+// Windows doesn't support a per-thread destructor with its
+// TLS primitives.  So, we build it manually by inserting a
+// function to be called on each thread's exit.
+// See http://www.codeproject.com/Articles/8113/Thread-Local-Storage-The-C-Way
+// and http://www.nynaeve.net/?p=183
+//
+// really we do this to have clear conscience since using TLS with thread-pools
+// is iffy
+// although OK within a request. But otherwise, threads have no identity in its
+// modern use.
+
+// This runs on windows only called from the System Loader
+#ifdef OS_WIN
+
+// Windows cleanup routine is invoked from a System Loader with a different
+// signature so we can not directly hookup the original OnThreadExit which is
+// private member
+// so we make StaticMeta class share with the us the address of the function so
+// we can invoke it.
+namespace wintlscleanup {
+
+// This is set to OnThreadExit in StaticMeta singleton constructor
+UnrefHandler thread_local_inclass_routine = nullptr;
+pthread_key_t thread_local_key = pthread_key_t (-1);
+
+// Static callback function to call with each thread termination.
+void NTAPI WinOnThreadExit(PVOID module, DWORD reason, PVOID reserved) {
+  // We decided to punt on PROCESS_EXIT
+  if (DLL_THREAD_DETACH == reason) {
+    if (thread_local_key != pthread_key_t(-1) &&
+        thread_local_inclass_routine != nullptr) {
+      void* tls = TlsGetValue(thread_local_key);
+      if (tls != nullptr) {
+        thread_local_inclass_routine(tls);
+      }
+    }
+  }
+}
+
+}  // wintlscleanup
+
+// extern "C" suppresses C++ name mangling so we know the symbol name for the
+// linker /INCLUDE:symbol pragma above.
+extern "C" {
+
+#ifdef _MSC_VER
+// The linker must not discard thread_callback_on_exit.  (We force a reference
+// to this variable with a linker /include:symbol pragma to ensure that.) If
+// this variable is discarded, the OnThreadExit function will never be called.
+#ifndef _X86_
+
+// .CRT section is merged with .rdata on x64 so it must be constant data.
+#pragma const_seg(".CRT$XLB")
+// When defining a const variable, it must have external linkage to be sure the
+// linker doesn't discard it.
+extern const PIMAGE_TLS_CALLBACK p_thread_callback_on_exit;
+const PIMAGE_TLS_CALLBACK p_thread_callback_on_exit =
+    wintlscleanup::WinOnThreadExit;
+// Reset the default section.
+#pragma const_seg()
+
+#pragma comment(linker, "/include:_tls_used")
+#pragma comment(linker, "/include:p_thread_callback_on_exit")
+
+#else  // _X86_
+
+#pragma data_seg(".CRT$XLB")
+PIMAGE_TLS_CALLBACK p_thread_callback_on_exit = wintlscleanup::WinOnThreadExit;
+// Reset the default section.
+#pragma data_seg()
+
+#pragma comment(linker, "/INCLUDE:__tls_used")
+#pragma comment(linker, "/INCLUDE:_p_thread_callback_on_exit")
+
+#endif  // _X86_
+
+#else
+// https://github.com/couchbase/gperftools/blob/master/src/windows/port.cc
+BOOL WINAPI DllMain(HINSTANCE h, DWORD dwReason, PVOID pv) {
+  if (dwReason == DLL_THREAD_DETACH)
+    wintlscleanup::WinOnThreadExit(h, dwReason, pv);
+  return TRUE;
+}
+#endif
+}  // extern "C"
+
+#endif  // OS_WIN
+
+void ThreadLocalPtr::InitSingletons() { ThreadLocalPtr::Instance(); }
+
+ThreadLocalPtr::StaticMeta* ThreadLocalPtr::Instance() {
+  // Here we prefer function static variable instead of global
+  // static variable as function static variable is initialized
+  // when the function is first call.  As a result, we can properly
+  // control their construction order by properly preparing their
+  // first function call.
+  //
+  // Note that here we decide to make "inst" a static pointer w/o deleting
+  // it at the end instead of a static variable.  This is to avoid the following
+  // destruction order disaster happens when a child thread using ThreadLocalPtr
+  // dies AFTER the main thread dies:  When a child thread happens to use
+  // ThreadLocalPtr, it will try to delete its thread-local data on its
+  // OnThreadExit when the child thread dies.  However, OnThreadExit depends
+  // on the following variable.  As a result, if the main thread dies before any
+  // child thread happen to use ThreadLocalPtr dies, then the destruction of
+  // the following variable will go first, then OnThreadExit, therefore causing
+  // invalid access.
+  //
+  // The above problem can be solved by using thread_local to store tls_ instead
+  // of using __thread.  The major difference between thread_local and __thread
+  // is that thread_local supports dynamic construction and destruction of
+  // non-primitive typed variables.  As a result, we can guarantee the
+  // destruction order even when the main thread dies before any child threads.
+  // However, thread_local is not supported in all compilers that accept -std=c++11
+  // (e.g., eg Mac with XCode < 8. XCode 8+ supports thread_local).
+  static ThreadLocalPtr::StaticMeta* inst = new ThreadLocalPtr::StaticMeta();
+  return inst;
+}
+
+port::Mutex* ThreadLocalPtr::StaticMeta::Mutex() { return &Instance()->mutex_; }
+
+void ThreadLocalPtr::StaticMeta::OnThreadExit(void* ptr) {
+  auto* tls = static_cast<ThreadData*>(ptr);
+  assert(tls != nullptr);
+
+  // Use the cached StaticMeta::Instance() instead of directly calling
+  // the variable inside StaticMeta::Instance() might already go out of
+  // scope here in case this OnThreadExit is called after the main thread
+  // dies.
+  auto* inst = tls->inst;
+  pthread_setspecific(inst->pthread_key_, nullptr);
+
+  MutexLock l(inst->MemberMutex());
+  inst->RemoveThreadData(tls);
+  // Unref stored pointers of current thread from all instances
+  uint32_t id = 0;
+  for (auto& e : tls->entries) {
+    void* raw = e.ptr.load();
+    if (raw != nullptr) {
+      auto unref = inst->GetHandler(id);
+      if (unref != nullptr) {
+        unref(raw);
+      }
+    }
+    ++id;
+  }
+  // Delete thread local structure no matter if it is Mac platform
+  delete tls;
+}
+
+ThreadLocalPtr::StaticMeta::StaticMeta()
+  : next_instance_id_(0),
+    head_(this),
+    pthread_key_(0) {
+  if (pthread_key_create(&pthread_key_, &OnThreadExit) != 0) {
+    abort();
+  }
+
+  // OnThreadExit is not getting called on the main thread.
+  // Call through the static destructor mechanism to avoid memory leak.
+  //
+  // Caveats: ~A() will be invoked _after_ ~StaticMeta for the global
+  // singleton (destructors are invoked in reverse order of constructor
+  // _completion_); the latter must not mutate internal members. This
+  // cleanup mechanism inherently relies on use-after-release of the
+  // StaticMeta, and is brittle with respect to compiler-specific handling
+  // of memory backing destructed statically-scoped objects. Perhaps
+  // registering with atexit(3) would be more robust.
+  //
+// This is not required on Windows.
+#if !defined(OS_WIN)
+  static struct A {
+    ~A() {
+#ifndef ROCKSDB_SUPPORT_THREAD_LOCAL
+      ThreadData* tls_ =
+        static_cast<ThreadData*>(pthread_getspecific(Instance()->pthread_key_));
+#endif
+      if (tls_) {
+        OnThreadExit(tls_);
+      }
+    }
+  } a;
+#endif  // !defined(OS_WIN)
+
+  head_.next = &head_;
+  head_.prev = &head_;
+
+#ifdef OS_WIN
+  // Share with Windows its cleanup routine and the key
+  wintlscleanup::thread_local_inclass_routine = OnThreadExit;
+  wintlscleanup::thread_local_key = pthread_key_;
+#endif
+}
+
+void ThreadLocalPtr::StaticMeta::AddThreadData(ThreadData* d) {
+  Mutex()->AssertHeld();
+  d->next = &head_;
+  d->prev = head_.prev;
+  head_.prev->next = d;
+  head_.prev = d;
+}
+
+void ThreadLocalPtr::StaticMeta::RemoveThreadData(
+    ThreadData* d) {
+  Mutex()->AssertHeld();
+  d->next->prev = d->prev;
+  d->prev->next = d->next;
+  d->next = d->prev = d;
+}
+
+ThreadData* ThreadLocalPtr::StaticMeta::GetThreadLocal() {
+#ifndef ROCKSDB_SUPPORT_THREAD_LOCAL
+  // Make this local variable name look like a member variable so that we
+  // can share all the code below
+  ThreadData* tls_ =
+      static_cast<ThreadData*>(pthread_getspecific(Instance()->pthread_key_));
+#endif
+
+  if (UNLIKELY(tls_ == nullptr)) {
+    auto* inst = Instance();
+    tls_ = new ThreadData(inst);
+    {
+      // Register it in the global chain, needs to be done before thread exit
+      // handler registration
+      MutexLock l(Mutex());
+      inst->AddThreadData(tls_);
+    }
+    // Even it is not OS_MACOSX, need to register value for pthread_key_ so that
+    // its exit handler will be triggered.
+    if (pthread_setspecific(inst->pthread_key_, tls_) != 0) {
+      {
+        MutexLock l(Mutex());
+        inst->RemoveThreadData(tls_);
+      }
+      delete tls_;
+      abort();
+    }
+  }
+  return tls_;
+}
+
+void* ThreadLocalPtr::StaticMeta::Get(uint32_t id) const {
+  auto* tls = GetThreadLocal();
+  if (UNLIKELY(id >= tls->entries.size())) {
+    return nullptr;
+  }
+  return tls->entries[id].ptr.load(std::memory_order_acquire);
+}
+
+void ThreadLocalPtr::StaticMeta::Reset(uint32_t id, void* ptr) {
+  auto* tls = GetThreadLocal();
+  if (UNLIKELY(id >= tls->entries.size())) {
+    // Need mutex to protect entries access within ReclaimId
+    MutexLock l(Mutex());
+    tls->entries.resize(id + 1);
+  }
+  tls->entries[id].ptr.store(ptr, std::memory_order_release);
+}
+
+void* ThreadLocalPtr::StaticMeta::Swap(uint32_t id, void* ptr) {
+  auto* tls = GetThreadLocal();
+  if (UNLIKELY(id >= tls->entries.size())) {
+    // Need mutex to protect entries access within ReclaimId
+    MutexLock l(Mutex());
+    tls->entries.resize(id + 1);
+  }
+  return tls->entries[id].ptr.exchange(ptr, std::memory_order_acquire);
+}
+
+bool ThreadLocalPtr::StaticMeta::CompareAndSwap(uint32_t id, void* ptr,
+    void*& expected) {
+  auto* tls = GetThreadLocal();
+  if (UNLIKELY(id >= tls->entries.size())) {
+    // Need mutex to protect entries access within ReclaimId
+    MutexLock l(Mutex());
+    tls->entries.resize(id + 1);
+  }
+  return tls->entries[id].ptr.compare_exchange_strong(
+      expected, ptr, std::memory_order_release, std::memory_order_relaxed);
+}
+
+void ThreadLocalPtr::StaticMeta::Scrape(uint32_t id, autovector<void*>* ptrs,
+    void* const replacement) {
+  MutexLock l(Mutex());
+  for (ThreadData* t = head_.next; t != &head_; t = t->next) {
+    if (id < t->entries.size()) {
+      void* ptr =
+          t->entries[id].ptr.exchange(replacement, std::memory_order_acquire);
+      if (ptr != nullptr) {
+        ptrs->push_back(ptr);
+      }
+    }
+  }
+}
+
+void ThreadLocalPtr::StaticMeta::Fold(uint32_t id, FoldFunc func, void* res) {
+  MutexLock l(Mutex());
+  for (ThreadData* t = head_.next; t != &head_; t = t->next) {
+    if (id < t->entries.size()) {
+      void* ptr = t->entries[id].ptr.load();
+      if (ptr != nullptr) {
+        func(ptr, res);
+      }
+    }
+  }
+}
+
+uint32_t ThreadLocalPtr::TEST_PeekId() {
+  return Instance()->PeekId();
+}
+
+void ThreadLocalPtr::StaticMeta::SetHandler(uint32_t id, UnrefHandler handler) {
+  MutexLock l(Mutex());
+  handler_map_[id] = handler;
+}
+
+UnrefHandler ThreadLocalPtr::StaticMeta::GetHandler(uint32_t id) {
+  Mutex()->AssertHeld();
+  auto iter = handler_map_.find(id);
+  if (iter == handler_map_.end()) {
+    return nullptr;
+  }
+  return iter->second;
+}
+
+uint32_t ThreadLocalPtr::StaticMeta::GetId() {
+  MutexLock l(Mutex());
+  if (free_instance_ids_.empty()) {
+    return next_instance_id_++;
+  }
+
+  uint32_t id = free_instance_ids_.back();
+  free_instance_ids_.pop_back();
+  return id;
+}
+
+uint32_t ThreadLocalPtr::StaticMeta::PeekId() const {
+  MutexLock l(Mutex());
+  if (!free_instance_ids_.empty()) {
+    return free_instance_ids_.back();
+  }
+  return next_instance_id_;
+}
+
+void ThreadLocalPtr::StaticMeta::ReclaimId(uint32_t id) {
+  // This id is not used, go through all thread local data and release
+  // corresponding value
+  MutexLock l(Mutex());
+  auto unref = GetHandler(id);
+  for (ThreadData* t = head_.next; t != &head_; t = t->next) {
+    if (id < t->entries.size()) {
+      void* ptr = t->entries[id].ptr.exchange(nullptr);
+      if (ptr != nullptr && unref != nullptr) {
+        unref(ptr);
+      }
+    }
+  }
+  handler_map_[id] = nullptr;
+  free_instance_ids_.push_back(id);
+}
+
+ThreadLocalPtr::ThreadLocalPtr(UnrefHandler handler)
+    : id_(Instance()->GetId()) {
+  if (handler != nullptr) {
+    Instance()->SetHandler(id_, handler);
+  }
+}
+
+ThreadLocalPtr::~ThreadLocalPtr() {
+  Instance()->ReclaimId(id_);
+}
+
+void* ThreadLocalPtr::Get() const {
+  return Instance()->Get(id_);
+}
+
+void ThreadLocalPtr::Reset(void* ptr) {
+  Instance()->Reset(id_, ptr);
+}
+
+void* ThreadLocalPtr::Swap(void* ptr) {
+  return Instance()->Swap(id_, ptr);
+}
+
+bool ThreadLocalPtr::CompareAndSwap(void* ptr, void*& expected) {
+  return Instance()->CompareAndSwap(id_, ptr, expected);
+}
+
+void ThreadLocalPtr::Scrape(autovector<void*>* ptrs, void* const replacement) {
+  Instance()->Scrape(id_, ptrs, replacement);
+}
+
+void ThreadLocalPtr::Fold(FoldFunc func, void* res) {
+  Instance()->Fold(id_, func, res);
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/thread_local.h b/src/rocksdb/util/thread_local.h
new file mode 100644
index 000000000..c4b762ab6
--- /dev/null
+++ b/src/rocksdb/util/thread_local.h
@@ -0,0 +1,101 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+
+#include <atomic>
+#include <functional>
+#include <memory>
+#include <unordered_map>
+#include <vector>
+
+#include "util/autovector.h"
+#include "port/port.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Cleanup function that will be called for a stored thread local
+// pointer (if not NULL) when one of the following happens:
+// (1) a thread terminates
+// (2) a ThreadLocalPtr is destroyed
+//
+// Warning: this function is called while holding a global mutex. The same mutex
+// is used (at least in some cases) by most methods of ThreadLocalPtr, and it's
+// shared across all instances of ThreadLocalPtr. Thereforere extra care
+// is needed to avoid deadlocks. In particular, the handler shouldn't lock any
+// mutexes and shouldn't call any methods of any ThreadLocalPtr instances,
+// unless you know what you're doing.
+typedef void (*UnrefHandler)(void* ptr);
+
+// ThreadLocalPtr stores only values of pointer type.  Different from
+// the usual thread-local-storage, ThreadLocalPtr has the ability to
+// distinguish data coming from different threads and different
+// ThreadLocalPtr instances.  For example, if a regular thread_local
+// variable A is declared in DBImpl, two DBImpl objects would share
+// the same A.  However, a ThreadLocalPtr that is defined under the
+// scope of DBImpl can avoid such confliction.  As a result, its memory
+// usage would be O(# of threads * # of ThreadLocalPtr instances).
+class ThreadLocalPtr {
+ public:
+  explicit ThreadLocalPtr(UnrefHandler handler = nullptr);
+
+  ThreadLocalPtr(const ThreadLocalPtr&) = delete;
+  ThreadLocalPtr& operator=(const ThreadLocalPtr&) = delete;
+
+  ~ThreadLocalPtr();
+
+  // Return the current pointer stored in thread local
+  void* Get() const;
+
+  // Set a new pointer value to the thread local storage.
+  void Reset(void* ptr);
+
+  // Atomically swap the supplied ptr and return the previous value
+  void* Swap(void* ptr);
+
+  // Atomically compare the stored value with expected. Set the new
+  // pointer value to thread local only if the comparison is true.
+  // Otherwise, expected returns the stored value.
+  // Return true on success, false on failure
+  bool CompareAndSwap(void* ptr, void*& expected);
+
+  // Reset all thread local data to replacement, and return non-nullptr
+  // data for all existing threads
+  void Scrape(autovector<void*>* ptrs, void* const replacement);
+
+  typedef std::function<void(void*, void*)> FoldFunc;
+  // Update res by applying func on each thread-local value. Holds a lock that
+  // prevents unref handler from running during this call, but clients must
+  // still provide external synchronization since the owning thread can
+  // access the values without internal locking, e.g., via Get() and Reset().
+  void Fold(FoldFunc func, void* res);
+
+  // Add here for testing
+  // Return the next available Id without claiming it
+  static uint32_t TEST_PeekId();
+
+  // Initialize the static singletons of the ThreadLocalPtr.
+  //
+  // If this function is not called, then the singletons will be
+  // automatically initialized when they are used.
+  //
+  // Calling this function twice or after the singletons have been
+  // initialized will be no-op.
+  static void InitSingletons();
+
+  class StaticMeta;
+
+private:
+
+  static StaticMeta* Instance();
+
+  const uint32_t id_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/thread_local_test.cc b/src/rocksdb/util/thread_local_test.cc
new file mode 100644
index 000000000..b788b1773
--- /dev/null
+++ b/src/rocksdb/util/thread_local_test.cc
@@ -0,0 +1,580 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <thread>
+#include <atomic>
+#include <string>
+
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "test_util/sync_point.h"
+#include "test_util/testharness.h"
+#include "test_util/testutil.h"
+#include "util/autovector.h"
+#include "util/thread_local.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class ThreadLocalTest : public testing::Test {
+ public:
+  ThreadLocalTest() : env_(Env::Default()) {}
+
+  Env* env_;
+};
+
+namespace {
+
+struct Params {
+  Params(port::Mutex* m, port::CondVar* c, int* u, int n,
+         UnrefHandler handler = nullptr)
+      : mu(m),
+        cv(c),
+        unref(u),
+        total(n),
+        started(0),
+        completed(0),
+        doWrite(false),
+        tls1(handler),
+        tls2(nullptr) {}
+
+  port::Mutex* mu;
+  port::CondVar* cv;
+  int* unref;
+  int total;
+  int started;
+  int completed;
+  bool doWrite;
+  ThreadLocalPtr tls1;
+  ThreadLocalPtr* tls2;
+};
+
+class IDChecker : public ThreadLocalPtr {
+public:
+  static uint32_t PeekId() {
+    return TEST_PeekId();
+  }
+};
+
+}  // anonymous namespace
+
+// Suppress false positive clang analyzer warnings.
+#ifndef __clang_analyzer__
+TEST_F(ThreadLocalTest, UniqueIdTest) {
+  port::Mutex mu;
+  port::CondVar cv(&mu);
+
+  uint32_t base_id = IDChecker::PeekId();
+  // New ThreadLocal instance bumps id by 1
+  {
+    // Id used 0
+    Params p1(&mu, &cv, nullptr, 1u);
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 1u);
+    // Id used 1
+    Params p2(&mu, &cv, nullptr, 1u);
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 2u);
+    // Id used 2
+    Params p3(&mu, &cv, nullptr, 1u);
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 3u);
+    // Id used 3
+    Params p4(&mu, &cv, nullptr, 1u);
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 4u);
+  }
+  // id 3, 2, 1, 0 are in the free queue in order
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 0u);
+
+  // pick up 0
+  Params p1(&mu, &cv, nullptr, 1u);
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 1u);
+  // pick up 1
+  Params* p2 = new Params(&mu, &cv, nullptr, 1u);
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 2u);
+  // pick up 2
+  Params p3(&mu, &cv, nullptr, 1u);
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 3u);
+  // return up 1
+  delete p2;
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 1u);
+  // Now we have 3, 1 in queue
+  // pick up 1
+  Params p4(&mu, &cv, nullptr, 1u);
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 3u);
+  // pick up 3
+  Params p5(&mu, &cv, nullptr, 1u);
+  // next new id
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 4u);
+  // After exit, id sequence in queue:
+  // 3, 1, 2, 0
+}
+#endif  // __clang_analyzer__
+
+TEST_F(ThreadLocalTest, SequentialReadWriteTest) {
+  // global id list carries over 3, 1, 2, 0
+  uint32_t base_id = IDChecker::PeekId();
+
+  port::Mutex mu;
+  port::CondVar cv(&mu);
+  Params p(&mu, &cv, nullptr, 1);
+  ThreadLocalPtr tls2;
+  p.tls2 = &tls2;
+
+  auto func = [](void* ptr) {
+    auto& params = *static_cast<Params*>(ptr);
+
+    ASSERT_TRUE(params.tls1.Get() == nullptr);
+    params.tls1.Reset(reinterpret_cast<int*>(1));
+    ASSERT_TRUE(params.tls1.Get() == reinterpret_cast<int*>(1));
+    params.tls1.Reset(reinterpret_cast<int*>(2));
+    ASSERT_TRUE(params.tls1.Get() == reinterpret_cast<int*>(2));
+
+    ASSERT_TRUE(params.tls2->Get() == nullptr);
+    params.tls2->Reset(reinterpret_cast<int*>(1));
+    ASSERT_TRUE(params.tls2->Get() == reinterpret_cast<int*>(1));
+    params.tls2->Reset(reinterpret_cast<int*>(2));
+    ASSERT_TRUE(params.tls2->Get() == reinterpret_cast<int*>(2));
+
+    params.mu->Lock();
+    ++(params.completed);
+    params.cv->SignalAll();
+    params.mu->Unlock();
+  };
+
+  for (int iter = 0; iter < 1024; ++iter) {
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 1u);
+    // Another new thread, read/write should not see value from previous thread
+    env_->StartThread(func, static_cast<void*>(&p));
+    mu.Lock();
+    while (p.completed != iter + 1) {
+      cv.Wait();
+    }
+    mu.Unlock();
+    ASSERT_EQ(IDChecker::PeekId(), base_id + 1u);
+  }
+}
+
+TEST_F(ThreadLocalTest, ConcurrentReadWriteTest) {
+  // global id list carries over 3, 1, 2, 0
+  uint32_t base_id = IDChecker::PeekId();
+
+  ThreadLocalPtr tls2;
+  port::Mutex mu1;
+  port::CondVar cv1(&mu1);
+  Params p1(&mu1, &cv1, nullptr, 16);
+  p1.tls2 = &tls2;
+
+  port::Mutex mu2;
+  port::CondVar cv2(&mu2);
+  Params p2(&mu2, &cv2, nullptr, 16);
+  p2.doWrite = true;
+  p2.tls2 = &tls2;
+
+  auto func = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+
+    p.mu->Lock();
+    // Size_T switches size along with the ptr size
+    // we want to cast to.
+    size_t own = ++(p.started);
+    p.cv->SignalAll();
+    while (p.started != p.total) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+
+    // Let write threads write a different value from the read threads
+    if (p.doWrite) {
+      own += 8192;
+    }
+
+    ASSERT_TRUE(p.tls1.Get() == nullptr);
+    ASSERT_TRUE(p.tls2->Get() == nullptr);
+
+    auto* env = Env::Default();
+    auto start = env->NowMicros();
+
+    p.tls1.Reset(reinterpret_cast<size_t*>(own));
+    p.tls2->Reset(reinterpret_cast<size_t*>(own + 1));
+    // Loop for 1 second
+    while (env->NowMicros() - start < 1000 * 1000) {
+      for (int iter = 0; iter < 100000; ++iter) {
+        ASSERT_TRUE(p.tls1.Get() == reinterpret_cast<size_t*>(own));
+        ASSERT_TRUE(p.tls2->Get() == reinterpret_cast<size_t*>(own + 1));
+        if (p.doWrite) {
+          p.tls1.Reset(reinterpret_cast<size_t*>(own));
+          p.tls2->Reset(reinterpret_cast<size_t*>(own + 1));
+        }
+      }
+    }
+
+    p.mu->Lock();
+    ++(p.completed);
+    p.cv->SignalAll();
+    p.mu->Unlock();
+  };
+
+  // Initiate 2 instnaces: one keeps writing and one keeps reading.
+  // The read instance should not see data from the write instance.
+  // Each thread local copy of the value are also different from each
+  // other.
+  for (int th = 0; th < p1.total; ++th) {
+    env_->StartThread(func, static_cast<void*>(&p1));
+  }
+  for (int th = 0; th < p2.total; ++th) {
+    env_->StartThread(func, static_cast<void*>(&p2));
+  }
+
+  mu1.Lock();
+  while (p1.completed != p1.total) {
+    cv1.Wait();
+  }
+  mu1.Unlock();
+
+  mu2.Lock();
+  while (p2.completed != p2.total) {
+    cv2.Wait();
+  }
+  mu2.Unlock();
+
+  ASSERT_EQ(IDChecker::PeekId(), base_id + 3u);
+}
+
+TEST_F(ThreadLocalTest, Unref) {
+  auto unref = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+    p.mu->Lock();
+    ++(*p.unref);
+    p.mu->Unlock();
+  };
+
+  // Case 0: no unref triggered if ThreadLocalPtr is never accessed
+  auto func0 = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+
+    p.mu->Lock();
+    ++(p.started);
+    p.cv->SignalAll();
+    while (p.started != p.total) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+  };
+
+  for (int th = 1; th <= 128; th += th) {
+    port::Mutex mu;
+    port::CondVar cv(&mu);
+    int unref_count = 0;
+    Params p(&mu, &cv, &unref_count, th, unref);
+
+    for (int i = 0; i < p.total; ++i) {
+      env_->StartThread(func0, static_cast<void*>(&p));
+    }
+    env_->WaitForJoin();
+    ASSERT_EQ(unref_count, 0);
+  }
+
+  // Case 1: unref triggered by thread exit
+  auto func1 = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+
+    p.mu->Lock();
+    ++(p.started);
+    p.cv->SignalAll();
+    while (p.started != p.total) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+
+    ASSERT_TRUE(p.tls1.Get() == nullptr);
+    ASSERT_TRUE(p.tls2->Get() == nullptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+  };
+
+  for (int th = 1; th <= 128; th += th) {
+    port::Mutex mu;
+    port::CondVar cv(&mu);
+    int unref_count = 0;
+    ThreadLocalPtr tls2(unref);
+    Params p(&mu, &cv, &unref_count, th, unref);
+    p.tls2 = &tls2;
+
+    for (int i = 0; i < p.total; ++i) {
+      env_->StartThread(func1, static_cast<void*>(&p));
+    }
+
+    env_->WaitForJoin();
+
+    // N threads x 2 ThreadLocal instance cleanup on thread exit
+    ASSERT_EQ(unref_count, 2 * p.total);
+  }
+
+  // Case 2: unref triggered by ThreadLocal instance destruction
+  auto func2 = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+
+    p.mu->Lock();
+    ++(p.started);
+    p.cv->SignalAll();
+    while (p.started != p.total) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+
+    ASSERT_TRUE(p.tls1.Get() == nullptr);
+    ASSERT_TRUE(p.tls2->Get() == nullptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+
+    p.mu->Lock();
+    ++(p.completed);
+    p.cv->SignalAll();
+
+    // Waiting for instruction to exit thread
+    while (p.completed != 0) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+  };
+
+  for (int th = 1; th <= 128; th += th) {
+    port::Mutex mu;
+    port::CondVar cv(&mu);
+    int unref_count = 0;
+    Params p(&mu, &cv, &unref_count, th, unref);
+    p.tls2 = new ThreadLocalPtr(unref);
+
+    for (int i = 0; i < p.total; ++i) {
+      env_->StartThread(func2, static_cast<void*>(&p));
+    }
+
+    // Wait for all threads to finish using Params
+    mu.Lock();
+    while (p.completed != p.total) {
+      cv.Wait();
+    }
+    mu.Unlock();
+
+    // Now destroy one ThreadLocal instance
+    delete p.tls2;
+    p.tls2 = nullptr;
+    // instance destroy for N threads
+    ASSERT_EQ(unref_count, p.total);
+
+    // Signal to exit
+    mu.Lock();
+    p.completed = 0;
+    cv.SignalAll();
+    mu.Unlock();
+    env_->WaitForJoin();
+    // additional N threads exit unref for the left instance
+    ASSERT_EQ(unref_count, 2 * p.total);
+  }
+}
+
+TEST_F(ThreadLocalTest, Swap) {
+  ThreadLocalPtr tls;
+  tls.Reset(reinterpret_cast<void*>(1));
+  ASSERT_EQ(reinterpret_cast<int64_t>(tls.Swap(nullptr)), 1);
+  ASSERT_TRUE(tls.Swap(reinterpret_cast<void*>(2)) == nullptr);
+  ASSERT_EQ(reinterpret_cast<int64_t>(tls.Get()), 2);
+  ASSERT_EQ(reinterpret_cast<int64_t>(tls.Swap(reinterpret_cast<void*>(3))), 2);
+}
+
+TEST_F(ThreadLocalTest, Scrape) {
+  auto unref = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+    p.mu->Lock();
+    ++(*p.unref);
+    p.mu->Unlock();
+  };
+
+  auto func = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+
+    ASSERT_TRUE(p.tls1.Get() == nullptr);
+    ASSERT_TRUE(p.tls2->Get() == nullptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+
+    p.tls1.Reset(ptr);
+    p.tls2->Reset(ptr);
+
+    p.mu->Lock();
+    ++(p.completed);
+    p.cv->SignalAll();
+
+    // Waiting for instruction to exit thread
+    while (p.completed != 0) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+  };
+
+  for (int th = 1; th <= 128; th += th) {
+    port::Mutex mu;
+    port::CondVar cv(&mu);
+    int unref_count = 0;
+    Params p(&mu, &cv, &unref_count, th, unref);
+    p.tls2 = new ThreadLocalPtr(unref);
+
+    for (int i = 0; i < p.total; ++i) {
+      env_->StartThread(func, static_cast<void*>(&p));
+    }
+
+    // Wait for all threads to finish using Params
+    mu.Lock();
+    while (p.completed != p.total) {
+      cv.Wait();
+    }
+    mu.Unlock();
+
+    ASSERT_EQ(unref_count, 0);
+
+    // Scrape all thread local data. No unref at thread
+    // exit or ThreadLocalPtr destruction
+    autovector<void*> ptrs;
+    p.tls1.Scrape(&ptrs, nullptr);
+    p.tls2->Scrape(&ptrs, nullptr);
+    delete p.tls2;
+    // Signal to exit
+    mu.Lock();
+    p.completed = 0;
+    cv.SignalAll();
+    mu.Unlock();
+    env_->WaitForJoin();
+
+    ASSERT_EQ(unref_count, 0);
+  }
+}
+
+TEST_F(ThreadLocalTest, Fold) {
+  auto unref = [](void* ptr) {
+    delete static_cast<std::atomic<int64_t>*>(ptr);
+  };
+  static const int kNumThreads = 16;
+  static const int kItersPerThread = 10;
+  port::Mutex mu;
+  port::CondVar cv(&mu);
+  Params params(&mu, &cv, nullptr, kNumThreads, unref);
+  auto func = [](void* ptr) {
+    auto& p = *static_cast<Params*>(ptr);
+    ASSERT_TRUE(p.tls1.Get() == nullptr);
+    p.tls1.Reset(new std::atomic<int64_t>(0));
+
+    for (int i = 0; i < kItersPerThread; ++i) {
+      static_cast<std::atomic<int64_t>*>(p.tls1.Get())->fetch_add(1);
+    }
+
+    p.mu->Lock();
+    ++(p.completed);
+    p.cv->SignalAll();
+
+    // Waiting for instruction to exit thread
+    while (p.completed != 0) {
+      p.cv->Wait();
+    }
+    p.mu->Unlock();
+  };
+
+  for (int th = 0; th < params.total; ++th) {
+    env_->StartThread(func, static_cast<void*>(&params));
+  }
+
+  // Wait for all threads to finish using Params
+  mu.Lock();
+  while (params.completed != params.total) {
+    cv.Wait();
+  }
+  mu.Unlock();
+
+  // Verify Fold() behavior
+  int64_t sum = 0;
+  params.tls1.Fold(
+      [](void* ptr, void* res) {
+        auto sum_ptr = static_cast<int64_t*>(res);
+        *sum_ptr += static_cast<std::atomic<int64_t>*>(ptr)->load();
+      },
+      &sum);
+  ASSERT_EQ(sum, kNumThreads * kItersPerThread);
+
+  // Signal to exit
+  mu.Lock();
+  params.completed = 0;
+  cv.SignalAll();
+  mu.Unlock();
+  env_->WaitForJoin();
+}
+
+TEST_F(ThreadLocalTest, CompareAndSwap) {
+  ThreadLocalPtr tls;
+  ASSERT_TRUE(tls.Swap(reinterpret_cast<void*>(1)) == nullptr);
+  void* expected = reinterpret_cast<void*>(1);
+  // Swap in 2
+  ASSERT_TRUE(tls.CompareAndSwap(reinterpret_cast<void*>(2), expected));
+  expected = reinterpret_cast<void*>(100);
+  // Fail Swap, still 2
+  ASSERT_TRUE(!tls.CompareAndSwap(reinterpret_cast<void*>(2), expected));
+  ASSERT_EQ(expected, reinterpret_cast<void*>(2));
+  // Swap in 3
+  expected = reinterpret_cast<void*>(2);
+  ASSERT_TRUE(tls.CompareAndSwap(reinterpret_cast<void*>(3), expected));
+  ASSERT_EQ(tls.Get(), reinterpret_cast<void*>(3));
+}
+
+namespace {
+
+void* AccessThreadLocal(void* /*arg*/) {
+  TEST_SYNC_POINT("AccessThreadLocal:Start");
+  ThreadLocalPtr tlp;
+  tlp.Reset(new std::string("hello RocksDB"));
+  TEST_SYNC_POINT("AccessThreadLocal:End");
+  return nullptr;
+}
+
+}  // namespace
+
+// The following test is disabled as it requires manual steps to run it
+// correctly.
+//
+// Currently we have no way to acess SyncPoint w/o ASAN error when the
+// child thread dies after the main thread dies.  So if you manually enable
+// this test and only see an ASAN error on SyncPoint, it means you pass the
+// test.
+TEST_F(ThreadLocalTest, DISABLED_MainThreadDiesFirst) {
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->LoadDependency(
+      {{"AccessThreadLocal:Start", "MainThreadDiesFirst:End"},
+       {"PosixEnv::~PosixEnv():End", "AccessThreadLocal:End"}});
+
+  // Triggers the initialization of singletons.
+  Env::Default();
+
+#ifndef ROCKSDB_LITE
+  try {
+#endif  // ROCKSDB_LITE
+    ROCKSDB_NAMESPACE::port::Thread th(&AccessThreadLocal, nullptr);
+    th.detach();
+    TEST_SYNC_POINT("MainThreadDiesFirst:End");
+#ifndef ROCKSDB_LITE
+  } catch (const std::system_error& ex) {
+    std::cerr << "Start thread: " << ex.code() << std::endl;
+    FAIL();
+  }
+#endif  // ROCKSDB_LITE
+}
+
+}  // namespace ROCKSDB_NAMESPACE
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/rocksdb/util/thread_operation.h b/src/rocksdb/util/thread_operation.h
new file mode 100644
index 000000000..b5d4b6906
--- /dev/null
+++ b/src/rocksdb/util/thread_operation.h
@@ -0,0 +1,121 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// This file defines the structures for thread operation and state.
+// Thread operations are used to describe high level action of a
+// thread such as doing compaction or flush, while thread state
+// are used to describe lower-level action such as reading /
+// writing a file or waiting for a mutex.  Operations and states
+// are designed to be independent.  Typically, a thread usually involves
+// in one operation and one state at any specific point in time.
+
+#pragma once
+
+#include "rocksdb/thread_status.h"
+
+#include <string>
+
+namespace ROCKSDB_NAMESPACE {
+
+#ifdef ROCKSDB_USING_THREAD_STATUS
+
+// The structure that describes a major thread operation.
+struct OperationInfo {
+  const ThreadStatus::OperationType type;
+  const std::string name;
+};
+
+// The global operation table.
+//
+// When updating a status of a thread, the pointer of the OperationInfo
+// of the current ThreadStatusData will be pointing to one of the
+// rows in this global table.
+//
+// Note that it's not designed to be constant as in the future we
+// might consider adding global count to the OperationInfo.
+static OperationInfo global_operation_table[] = {
+  {ThreadStatus::OP_UNKNOWN, ""},
+  {ThreadStatus::OP_COMPACTION, "Compaction"},
+  {ThreadStatus::OP_FLUSH, "Flush"}
+};
+
+struct OperationStageInfo {
+  const ThreadStatus::OperationStage stage;
+  const std::string name;
+};
+
+// A table maintains the mapping from stage type to stage string.
+// Note that the string must be changed accordingly when the
+// associated function name changed.
+static OperationStageInfo global_op_stage_table[] = {
+  {ThreadStatus::STAGE_UNKNOWN, ""},
+  {ThreadStatus::STAGE_FLUSH_RUN,
+      "FlushJob::Run"},
+  {ThreadStatus::STAGE_FLUSH_WRITE_L0,
+      "FlushJob::WriteLevel0Table"},
+  {ThreadStatus::STAGE_COMPACTION_PREPARE,
+      "CompactionJob::Prepare"},
+  {ThreadStatus::STAGE_COMPACTION_RUN,
+      "CompactionJob::Run"},
+  {ThreadStatus::STAGE_COMPACTION_PROCESS_KV,
+      "CompactionJob::ProcessKeyValueCompaction"},
+  {ThreadStatus::STAGE_COMPACTION_INSTALL,
+      "CompactionJob::Install"},
+  {ThreadStatus::STAGE_COMPACTION_SYNC_FILE,
+      "CompactionJob::FinishCompactionOutputFile"},
+  {ThreadStatus::STAGE_PICK_MEMTABLES_TO_FLUSH,
+      "MemTableList::PickMemtablesToFlush"},
+  {ThreadStatus::STAGE_MEMTABLE_ROLLBACK,
+      "MemTableList::RollbackMemtableFlush"},
+  {ThreadStatus::STAGE_MEMTABLE_INSTALL_FLUSH_RESULTS,
+      "MemTableList::TryInstallMemtableFlushResults"},
+};
+
+// The structure that describes a state.
+struct StateInfo {
+  const ThreadStatus::StateType type;
+  const std::string name;
+};
+
+// The global state table.
+//
+// When updating a status of a thread, the pointer of the StateInfo
+// of the current ThreadStatusData will be pointing to one of the
+// rows in this global table.
+static StateInfo global_state_table[] = {
+  {ThreadStatus::STATE_UNKNOWN, ""},
+  {ThreadStatus::STATE_MUTEX_WAIT, "Mutex Wait"},
+};
+
+struct OperationProperty {
+  int code;
+  std::string name;
+};
+
+static OperationProperty compaction_operation_properties[] = {
+  {ThreadStatus::COMPACTION_JOB_ID, "JobID"},
+  {ThreadStatus::COMPACTION_INPUT_OUTPUT_LEVEL, "InputOutputLevel"},
+  {ThreadStatus::COMPACTION_PROP_FLAGS, "Manual/Deletion/Trivial"},
+  {ThreadStatus::COMPACTION_TOTAL_INPUT_BYTES, "TotalInputBytes"},
+  {ThreadStatus::COMPACTION_BYTES_READ, "BytesRead"},
+  {ThreadStatus::COMPACTION_BYTES_WRITTEN, "BytesWritten"},
+};
+
+static OperationProperty flush_operation_properties[] = {
+  {ThreadStatus::FLUSH_JOB_ID, "JobID"},
+  {ThreadStatus::FLUSH_BYTES_MEMTABLES, "BytesMemtables"},
+  {ThreadStatus::FLUSH_BYTES_WRITTEN, "BytesWritten"}
+};
+
+#else
+
+struct OperationInfo {
+};
+
+struct StateInfo {
+};
+
+#endif  // ROCKSDB_USING_THREAD_STATUS
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/threadpool_imp.cc b/src/rocksdb/util/threadpool_imp.cc
new file mode 100644
index 000000000..bf216c956
--- /dev/null
+++ b/src/rocksdb/util/threadpool_imp.cc
@@ -0,0 +1,507 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "util/threadpool_imp.h"
+
+#include "monitoring/thread_status_util.h"
+#include "port/port.h"
+
+#ifndef OS_WIN
+#  include <unistd.h>
+#endif
+
+#ifdef OS_LINUX
+#  include <sys/syscall.h>
+#  include <sys/resource.h>
+#endif
+
+#include <stdlib.h>
+#include <algorithm>
+#include <atomic>
+#include <condition_variable>
+#include <deque>
+#include <mutex>
+#include <sstream>
+#include <thread>
+#include <vector>
+
+namespace ROCKSDB_NAMESPACE {
+
+void ThreadPoolImpl::PthreadCall(const char* label, int result) {
+  if (result != 0) {
+    fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
+    abort();
+  }
+}
+
+struct ThreadPoolImpl::Impl {
+
+  Impl();
+  ~Impl();
+
+  void JoinThreads(bool wait_for_jobs_to_complete);
+
+  void SetBackgroundThreadsInternal(int num, bool allow_reduce);
+  int GetBackgroundThreads();
+
+  unsigned int GetQueueLen() const {
+    return queue_len_.load(std::memory_order_relaxed);
+  }
+
+  void LowerIOPriority();
+
+  void LowerCPUPriority();
+
+  void WakeUpAllThreads() {
+    bgsignal_.notify_all();
+  }
+
+  void BGThread(size_t thread_id);
+
+  void StartBGThreads();
+
+  void Submit(std::function<void()>&& schedule,
+    std::function<void()>&& unschedule, void* tag);
+
+  int UnSchedule(void* arg);
+
+  void SetHostEnv(Env* env) { env_ = env; }
+
+  Env* GetHostEnv() const { return env_; }
+
+  bool HasExcessiveThread() const {
+    return static_cast<int>(bgthreads_.size()) > total_threads_limit_;
+  }
+
+  // Return true iff the current thread is the excessive thread to terminate.
+  // Always terminate the running thread that is added last, even if there are
+  // more than one thread to terminate.
+  bool IsLastExcessiveThread(size_t thread_id) const {
+    return HasExcessiveThread() && thread_id == bgthreads_.size() - 1;
+  }
+
+  bool IsExcessiveThread(size_t thread_id) const {
+    return static_cast<int>(thread_id) >= total_threads_limit_;
+  }
+
+  // Return the thread priority.
+  // This would allow its member-thread to know its priority.
+  Env::Priority GetThreadPriority() const { return priority_; }
+
+  // Set the thread priority.
+  void SetThreadPriority(Env::Priority priority) { priority_ = priority; }
+
+private:
+ static void BGThreadWrapper(void* arg);
+
+ bool low_io_priority_;
+ bool low_cpu_priority_;
+ Env::Priority priority_;
+ Env* env_;
+
+ int total_threads_limit_;
+ std::atomic_uint queue_len_;  // Queue length. Used for stats reporting
+ bool exit_all_threads_;
+ bool wait_for_jobs_to_complete_;
+
+ // Entry per Schedule()/Submit() call
+ struct BGItem {
+   void* tag = nullptr;
+   std::function<void()> function;
+   std::function<void()> unschedFunction;
+  };
+
+  using BGQueue = std::deque<BGItem>;
+  BGQueue       queue_;
+
+  std::mutex               mu_;
+  std::condition_variable  bgsignal_;
+  std::vector<port::Thread> bgthreads_;
+};
+
+
+inline
+ThreadPoolImpl::Impl::Impl()
+    :
+      low_io_priority_(false),
+      low_cpu_priority_(false),
+      priority_(Env::LOW),
+      env_(nullptr),
+      total_threads_limit_(0),
+      queue_len_(),
+      exit_all_threads_(false),
+      wait_for_jobs_to_complete_(false),
+      queue_(),
+      mu_(),
+      bgsignal_(),
+      bgthreads_() {
+}
+
+inline
+ThreadPoolImpl::Impl::~Impl() { assert(bgthreads_.size() == 0U); }
+
+void ThreadPoolImpl::Impl::JoinThreads(bool wait_for_jobs_to_complete) {
+
+  std::unique_lock<std::mutex> lock(mu_);
+  assert(!exit_all_threads_);
+
+  wait_for_jobs_to_complete_ = wait_for_jobs_to_complete;
+  exit_all_threads_ = true;
+  // prevent threads from being recreated right after they're joined, in case
+  // the user is concurrently submitting jobs.
+  total_threads_limit_ = 0;
+
+  lock.unlock();
+
+  bgsignal_.notify_all();
+
+  for (auto& th : bgthreads_) {
+    th.join();
+  }
+
+  bgthreads_.clear();
+
+  exit_all_threads_ = false;
+  wait_for_jobs_to_complete_ = false;
+}
+
+inline
+void ThreadPoolImpl::Impl::LowerIOPriority() {
+  std::lock_guard<std::mutex> lock(mu_);
+  low_io_priority_ = true;
+}
+
+inline
+void ThreadPoolImpl::Impl::LowerCPUPriority() {
+  std::lock_guard<std::mutex> lock(mu_);
+  low_cpu_priority_ = true;
+}
+
+void ThreadPoolImpl::Impl::BGThread(size_t thread_id) {
+  bool low_io_priority = false;
+  bool low_cpu_priority = false;
+
+  while (true) {
+    // Wait until there is an item that is ready to run
+    std::unique_lock<std::mutex> lock(mu_);
+    // Stop waiting if the thread needs to do work or needs to terminate.
+    while (!exit_all_threads_ && !IsLastExcessiveThread(thread_id) &&
+           (queue_.empty() || IsExcessiveThread(thread_id))) {
+      bgsignal_.wait(lock);
+    }
+
+    if (exit_all_threads_) {  // mechanism to let BG threads exit safely
+
+      if (!wait_for_jobs_to_complete_ ||
+          queue_.empty()) {
+        break;
+       }
+    }
+
+    if (IsLastExcessiveThread(thread_id)) {
+      // Current thread is the last generated one and is excessive.
+      // We always terminate excessive thread in the reverse order of
+      // generation time.
+      auto& terminating_thread = bgthreads_.back();
+      terminating_thread.detach();
+      bgthreads_.pop_back();
+
+      if (HasExcessiveThread()) {
+        // There is still at least more excessive thread to terminate.
+        WakeUpAllThreads();
+      }
+      break;
+    }
+
+    auto func = std::move(queue_.front().function);
+    queue_.pop_front();
+
+    queue_len_.store(static_cast<unsigned int>(queue_.size()),
+                     std::memory_order_relaxed);
+
+    bool decrease_io_priority = (low_io_priority != low_io_priority_);
+    bool decrease_cpu_priority = (low_cpu_priority != low_cpu_priority_);
+    lock.unlock();
+
+#ifdef OS_LINUX
+    if (decrease_cpu_priority) {
+      setpriority(
+          PRIO_PROCESS,
+          // Current thread.
+          0,
+          // Lowest priority possible.
+          19);
+      low_cpu_priority = true;
+    }
+
+    if (decrease_io_priority) {
+#define IOPRIO_CLASS_SHIFT (13)
+#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
+      // Put schedule into IOPRIO_CLASS_IDLE class (lowest)
+      // These system calls only have an effect when used in conjunction
+      // with an I/O scheduler that supports I/O priorities. As at
+      // kernel 2.6.17 the only such scheduler is the Completely
+      // Fair Queuing (CFQ) I/O scheduler.
+      // To change scheduler:
+      //  echo cfq > /sys/block/<device_name>/queue/schedule
+      // Tunables to consider:
+      //  /sys/block/<device_name>/queue/slice_idle
+      //  /sys/block/<device_name>/queue/slice_sync
+      syscall(SYS_ioprio_set, 1,  // IOPRIO_WHO_PROCESS
+              0,                  // current thread
+              IOPRIO_PRIO_VALUE(3, 0));
+      low_io_priority = true;
+    }
+#else
+    (void)decrease_io_priority;  // avoid 'unused variable' error
+    (void)decrease_cpu_priority;
+#endif
+    func();
+  }
+}
+
+// Helper struct for passing arguments when creating threads.
+struct BGThreadMetadata {
+  ThreadPoolImpl::Impl* thread_pool_;
+  size_t thread_id_;  // Thread count in the thread.
+  BGThreadMetadata(ThreadPoolImpl::Impl* thread_pool, size_t thread_id)
+      : thread_pool_(thread_pool), thread_id_(thread_id) {}
+};
+
+void ThreadPoolImpl::Impl::BGThreadWrapper(void* arg) {
+  BGThreadMetadata* meta = reinterpret_cast<BGThreadMetadata*>(arg);
+  size_t thread_id = meta->thread_id_;
+  ThreadPoolImpl::Impl* tp = meta->thread_pool_;
+#ifdef ROCKSDB_USING_THREAD_STATUS
+  // initialize it because compiler isn't good enough to see we don't use it
+  // uninitialized
+  ThreadStatus::ThreadType thread_type = ThreadStatus::NUM_THREAD_TYPES;
+  switch (tp->GetThreadPriority()) {
+    case Env::Priority::HIGH:
+      thread_type = ThreadStatus::HIGH_PRIORITY;
+      break;
+    case Env::Priority::LOW:
+      thread_type = ThreadStatus::LOW_PRIORITY;
+      break;
+    case Env::Priority::BOTTOM:
+      thread_type = ThreadStatus::BOTTOM_PRIORITY;
+      break;
+    case Env::Priority::USER:
+      thread_type = ThreadStatus::USER;
+      break;
+    case Env::Priority::TOTAL:
+      assert(false);
+      return;
+  }
+  assert(thread_type != ThreadStatus::NUM_THREAD_TYPES);
+  ThreadStatusUtil::RegisterThread(tp->GetHostEnv(), thread_type);
+#endif
+  delete meta;
+  tp->BGThread(thread_id);
+#ifdef ROCKSDB_USING_THREAD_STATUS
+  ThreadStatusUtil::UnregisterThread();
+#endif
+  return;
+}
+
+void ThreadPoolImpl::Impl::SetBackgroundThreadsInternal(int num,
+  bool allow_reduce) {
+  std::lock_guard<std::mutex> lock(mu_);
+  if (exit_all_threads_) {
+    return;
+  }
+  if (num > total_threads_limit_ ||
+      (num < total_threads_limit_ && allow_reduce)) {
+    total_threads_limit_ = std::max(0, num);
+    WakeUpAllThreads();
+    StartBGThreads();
+  }
+}
+
+int ThreadPoolImpl::Impl::GetBackgroundThreads() {
+  std::unique_lock<std::mutex> lock(mu_);
+  return total_threads_limit_;
+}
+
+void ThreadPoolImpl::Impl::StartBGThreads() {
+  // Start background thread if necessary
+  while ((int)bgthreads_.size() < total_threads_limit_) {
+
+    port::Thread p_t(&BGThreadWrapper,
+      new BGThreadMetadata(this, bgthreads_.size()));
+
+// Set the thread name to aid debugging
+#if defined(_GNU_SOURCE) && defined(__GLIBC_PREREQ)
+#if __GLIBC_PREREQ(2, 12)
+    auto th_handle = p_t.native_handle();
+    std::string thread_priority = Env::PriorityToString(GetThreadPriority());
+    std::ostringstream thread_name_stream;
+    thread_name_stream << "rocksdb:";
+    for (char c : thread_priority) {
+      thread_name_stream << static_cast<char>(tolower(c));
+    }
+    thread_name_stream << bgthreads_.size();
+    pthread_setname_np(th_handle, thread_name_stream.str().c_str());
+#endif
+#endif
+    bgthreads_.push_back(std::move(p_t));
+  }
+}
+
+void ThreadPoolImpl::Impl::Submit(std::function<void()>&& schedule,
+  std::function<void()>&& unschedule, void* tag) {
+
+  std::lock_guard<std::mutex> lock(mu_);
+
+  if (exit_all_threads_) {
+    return;
+  }
+
+  StartBGThreads();
+
+  // Add to priority queue
+  queue_.push_back(BGItem());
+
+  auto& item = queue_.back();
+  item.tag = tag;
+  item.function = std::move(schedule);
+  item.unschedFunction = std::move(unschedule);
+
+  queue_len_.store(static_cast<unsigned int>(queue_.size()),
+    std::memory_order_relaxed);
+
+  if (!HasExcessiveThread()) {
+    // Wake up at least one waiting thread.
+    bgsignal_.notify_one();
+  } else {
+    // Need to wake up all threads to make sure the one woken
+    // up is not the one to terminate.
+    WakeUpAllThreads();
+  }
+}
+
+int ThreadPoolImpl::Impl::UnSchedule(void* arg) {
+  int count = 0;
+
+  std::vector<std::function<void()>> candidates;
+  {
+    std::lock_guard<std::mutex> lock(mu_);
+
+    // Remove from priority queue
+    BGQueue::iterator it = queue_.begin();
+    while (it != queue_.end()) {
+      if (arg == (*it).tag) {
+        if (it->unschedFunction) {
+          candidates.push_back(std::move(it->unschedFunction));
+        }
+        it = queue_.erase(it);
+        count++;
+      } else {
+        ++it;
+      }
+    }
+    queue_len_.store(static_cast<unsigned int>(queue_.size()),
+      std::memory_order_relaxed);
+  }
+
+
+ // Run unschedule functions outside the mutex
+  for (auto& f : candidates) {
+    f();
+  }
+
+  return count;
+}
+
+ThreadPoolImpl::ThreadPoolImpl() :
+  impl_(new Impl()) {
+}
+
+
+ThreadPoolImpl::~ThreadPoolImpl() {
+}
+
+void ThreadPoolImpl::JoinAllThreads() {
+  impl_->JoinThreads(false);
+}
+
+void ThreadPoolImpl::SetBackgroundThreads(int num) {
+  impl_->SetBackgroundThreadsInternal(num, true);
+}
+
+int ThreadPoolImpl::GetBackgroundThreads() {
+  return impl_->GetBackgroundThreads();
+}
+
+unsigned int ThreadPoolImpl::GetQueueLen() const {
+  return impl_->GetQueueLen();
+}
+
+void ThreadPoolImpl::WaitForJobsAndJoinAllThreads() {
+  impl_->JoinThreads(true);
+}
+
+void ThreadPoolImpl::LowerIOPriority() {
+  impl_->LowerIOPriority();
+}
+
+void ThreadPoolImpl::LowerCPUPriority() {
+  impl_->LowerCPUPriority();
+}
+
+void ThreadPoolImpl::IncBackgroundThreadsIfNeeded(int num) {
+  impl_->SetBackgroundThreadsInternal(num, false);
+}
+
+void ThreadPoolImpl::SubmitJob(const std::function<void()>& job) {
+  auto copy(job);
+  impl_->Submit(std::move(copy), std::function<void()>(), nullptr);
+}
+
+
+void ThreadPoolImpl::SubmitJob(std::function<void()>&& job) {
+  impl_->Submit(std::move(job), std::function<void()>(), nullptr);
+}
+
+void ThreadPoolImpl::Schedule(void(*function)(void* arg1), void* arg,
+  void* tag, void(*unschedFunction)(void* arg)) {
+  if (unschedFunction == nullptr) {
+    impl_->Submit(std::bind(function, arg), std::function<void()>(), tag);
+  } else {
+    impl_->Submit(std::bind(function, arg), std::bind(unschedFunction, arg),
+                  tag);
+  }
+}
+
+int ThreadPoolImpl::UnSchedule(void* arg) {
+  return impl_->UnSchedule(arg);
+}
+
+void ThreadPoolImpl::SetHostEnv(Env* env) { impl_->SetHostEnv(env); }
+
+Env* ThreadPoolImpl::GetHostEnv() const { return impl_->GetHostEnv(); }
+
+// Return the thread priority.
+// This would allow its member-thread to know its priority.
+Env::Priority ThreadPoolImpl::GetThreadPriority() const {
+  return impl_->GetThreadPriority();
+}
+
+// Set the thread priority.
+void ThreadPoolImpl::SetThreadPriority(Env::Priority priority) {
+  impl_->SetThreadPriority(priority);
+}
+
+ThreadPool* NewThreadPool(int num_threads) {
+  ThreadPoolImpl* thread_pool = new ThreadPoolImpl();
+  thread_pool->SetBackgroundThreads(num_threads);
+  return thread_pool;
+}
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/threadpool_imp.h b/src/rocksdb/util/threadpool_imp.h
new file mode 100644
index 000000000..e3c12577b
--- /dev/null
+++ b/src/rocksdb/util/threadpool_imp.h
@@ -0,0 +1,112 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include "rocksdb/threadpool.h"
+#include "rocksdb/env.h"
+
+#include <memory>
+#include <functional>
+
+namespace ROCKSDB_NAMESPACE {
+
+class ThreadPoolImpl : public ThreadPool {
+ public:
+  ThreadPoolImpl();
+  ~ThreadPoolImpl();
+
+  ThreadPoolImpl(ThreadPoolImpl&&) = delete;
+  ThreadPoolImpl& operator=(ThreadPoolImpl&&) = delete;
+
+  // Implement ThreadPool interfaces
+
+  // Wait for all threads to finish.
+  // Discards all the jobs that did not
+  // start executing and waits for those running
+  // to complete
+  void JoinAllThreads() override;
+
+  // Set the number of background threads that will be executing the
+  // scheduled jobs.
+  void SetBackgroundThreads(int num) override;
+  int GetBackgroundThreads() override;
+
+  // Get the number of jobs scheduled in the ThreadPool queue.
+  unsigned int GetQueueLen() const override;
+
+  // Waits for all jobs to complete those
+  // that already started running and those that did not
+  // start yet
+  void WaitForJobsAndJoinAllThreads() override;
+
+  // Make threads to run at a lower kernel IO priority
+  // Currently only has effect on Linux
+  void LowerIOPriority();
+
+  // Make threads to run at a lower kernel CPU priority
+  // Currently only has effect on Linux
+  void LowerCPUPriority();
+
+  // Ensure there is at aleast num threads in the pool
+  // but do not kill threads if there are more
+  void IncBackgroundThreadsIfNeeded(int num);
+
+  // Submit a fire and forget job
+  // These jobs can not be unscheduled
+
+  // This allows to submit the same job multiple times
+  void SubmitJob(const std::function<void()>&) override;
+  // This moves the function in for efficiency
+  void SubmitJob(std::function<void()>&&) override;
+
+  // Schedule a job with an unschedule tag and unschedule function
+  // Can be used to filter and unschedule jobs by a tag
+  // that are still in the queue and did not start running
+  void Schedule(void (*function)(void* arg1), void* arg, void* tag,
+                void (*unschedFunction)(void* arg));
+
+  // Filter jobs that are still in a queue and match
+  // the given tag. Remove them from a queue if any
+  // and for each such job execute an unschedule function
+  // if such was given at scheduling time.
+  int UnSchedule(void* tag);
+
+  void SetHostEnv(Env* env);
+
+  Env* GetHostEnv() const;
+
+  // Return the thread priority.
+  // This would allow its member-thread to know its priority.
+  Env::Priority GetThreadPriority() const;
+
+  // Set the thread priority.
+  void SetThreadPriority(Env::Priority priority);
+
+  static void PthreadCall(const char* label, int result);
+
+  struct Impl;
+
+ private:
+
+   // Current public virtual interface does not provide usable
+   // functionality and thus can not be used internally to
+   // facade different implementations.
+   //
+   // We propose a pimpl idiom in order to easily replace the thread pool impl
+   // w/o touching the header file but providing a different .cc potentially
+   // CMake option driven.
+   //
+   // Another option is to introduce a Env::MakeThreadPool() virtual interface
+   // and override the environment. This would require refactoring ThreadPool usage.
+   //
+   // We can also combine these two approaches
+   std::unique_ptr<Impl>   impl_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/timer_queue.h b/src/rocksdb/util/timer_queue.h
new file mode 100644
index 000000000..3bd517531
--- /dev/null
+++ b/src/rocksdb/util/timer_queue.h
@@ -0,0 +1,230 @@
+//  Portions Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Borrowed from
+// http://www.crazygaze.com/blog/2016/03/24/portable-c-timer-queue/
+// Timer Queue
+//
+// License
+//
+// The source code in this article is licensed under the CC0 license, so feel
+// free to copy, modify, share, do whatever you want with it.
+// No attribution is required, but Ill be happy if you do.
+// CC0 license
+
+// The person who associated a work with this deed has dedicated the work to the
+// public domain by waiving all of his or her rights to the work worldwide
+// under copyright law, including all related and neighboring rights, to the
+// extent allowed by law.  You can copy, modify, distribute and perform the
+// work, even for commercial purposes, all without asking permission.
+
+#pragma once
+
+#include <assert.h>
+#include <chrono>
+#include <condition_variable>
+#include <functional>
+#include <queue>
+#include <thread>
+#include <utility>
+#include <vector>
+
+#include "port/port.h"
+#include "test_util/sync_point.h"
+
+// Allows execution of handlers at a specified time in the future
+// Guarantees:
+//  - All handlers are executed ONCE, even if cancelled (aborted parameter will
+// be set to true)
+//      - If TimerQueue is destroyed, it will cancel all handlers.
+//  - Handlers are ALWAYS executed in the Timer Queue worker thread.
+//  - Handlers execution order is NOT guaranteed
+//
+////////////////////////////////////////////////////////////////////////////////
+// borrowed from
+// http://www.crazygaze.com/blog/2016/03/24/portable-c-timer-queue/
+class TimerQueue {
+ public:
+  TimerQueue() : m_th(&TimerQueue::run, this) {}
+
+  ~TimerQueue() { shutdown(); }
+
+  // This function is not thread-safe.
+  void shutdown() {
+    if (closed_) {
+      return;
+    }
+    cancelAll();
+    // Abusing the timer queue to trigger the shutdown.
+    add(0, [this](bool) {
+      m_finish = true;
+      return std::make_pair(false, 0);
+    });
+    m_th.join();
+    closed_ = true;
+  }
+
+  // Adds a new timer
+  // \return
+  //  Returns the ID of the new timer. You can use this ID to cancel the
+  // timer
+  uint64_t add(int64_t milliseconds,
+               std::function<std::pair<bool, int64_t>(bool)> handler) {
+    WorkItem item;
+    Clock::time_point tp = Clock::now();
+    item.end = tp + std::chrono::milliseconds(milliseconds);
+    TEST_SYNC_POINT_CALLBACK("TimeQueue::Add:item.end", &item.end);
+    item.period = milliseconds;
+    item.handler = std::move(handler);
+
+    std::unique_lock<std::mutex> lk(m_mtx);
+    uint64_t id = ++m_idcounter;
+    item.id = id;
+    m_items.push(std::move(item));
+
+    // Something changed, so wake up timer thread
+    m_checkWork.notify_one();
+    return id;
+  }
+
+  // Cancels the specified timer
+  // \return
+  //  1 if the timer was cancelled.
+  //  0 if you were too late to cancel (or the timer ID was never valid to
+  // start with)
+  size_t cancel(uint64_t id) {
+    // Instead of removing the item from the container (thus breaking the
+    // heap integrity), we set the item as having no handler, and put
+    // that handler on a new item at the top for immediate execution
+    // The timer thread will then ignore the original item, since it has no
+    // handler.
+    std::unique_lock<std::mutex> lk(m_mtx);
+    for (auto&& item : m_items.getContainer()) {
+      if (item.id == id && item.handler) {
+        WorkItem newItem;
+        // Zero time, so it stays at the top for immediate execution
+        newItem.end = Clock::time_point();
+        newItem.id = 0;  // Means it is a canceled item
+        // Move the handler from item to newitem (thus clearing item)
+        newItem.handler = std::move(item.handler);
+        m_items.push(std::move(newItem));
+
+        // Something changed, so wake up timer thread
+        m_checkWork.notify_one();
+        return 1;
+      }
+    }
+    return 0;
+  }
+
+  // Cancels all timers
+  // \return
+  //  The number of timers cancelled
+  size_t cancelAll() {
+    // Setting all "end" to 0 (for immediate execution) is ok,
+    // since it maintains the heap integrity
+    std::unique_lock<std::mutex> lk(m_mtx);
+    m_cancel = true;
+    for (auto&& item : m_items.getContainer()) {
+      if (item.id && item.handler) {
+        item.end = Clock::time_point();
+        item.id = 0;
+      }
+    }
+    auto ret = m_items.size();
+
+    m_checkWork.notify_one();
+    return ret;
+  }
+
+ private:
+  using Clock = std::chrono::steady_clock;
+  TimerQueue(const TimerQueue&) = delete;
+  TimerQueue& operator=(const TimerQueue&) = delete;
+
+  void run() {
+    std::unique_lock<std::mutex> lk(m_mtx);
+    while (!m_finish) {
+      auto end = calcWaitTime_lock();
+      if (end.first) {
+        // Timers found, so wait until it expires (or something else
+        // changes)
+        m_checkWork.wait_until(lk, end.second);
+      } else {
+        // No timers exist, so wait forever until something changes
+        m_checkWork.wait(lk);
+      }
+
+      // Check and execute as much work as possible, such as, all expired
+      // timers
+      checkWork(&lk);
+    }
+
+    // If we are shutting down, we should not have any items left,
+    // since the shutdown cancels all items
+    assert(m_items.size() == 0);
+  }
+
+  std::pair<bool, Clock::time_point> calcWaitTime_lock() {
+    while (m_items.size()) {
+      if (m_items.top().handler) {
+        // Item present, so return the new wait time
+        return std::make_pair(true, m_items.top().end);
+      } else {
+        // Discard empty handlers (they were cancelled)
+        m_items.pop();
+      }
+    }
+
+    // No items found, so return no wait time (causes the thread to wait
+    // indefinitely)
+    return std::make_pair(false, Clock::time_point());
+  }
+
+  void checkWork(std::unique_lock<std::mutex>* lk) {
+    while (m_items.size() && m_items.top().end <= Clock::now()) {
+      WorkItem item(m_items.top());
+      m_items.pop();
+
+      if (item.handler) {
+        (*lk).unlock();
+        auto reschedule_pair = item.handler(item.id == 0);
+        (*lk).lock();
+        if (!m_cancel && reschedule_pair.first) {
+          int64_t new_period = (reschedule_pair.second == -1)
+                                   ? item.period
+                                   : reschedule_pair.second;
+
+          item.period = new_period;
+          item.end = Clock::now() + std::chrono::milliseconds(new_period);
+          m_items.push(std::move(item));
+        }
+      }
+    }
+  }
+
+  bool m_finish = false;
+  bool m_cancel = false;
+  uint64_t m_idcounter = 0;
+  std::condition_variable m_checkWork;
+
+  struct WorkItem {
+    Clock::time_point end;
+    int64_t period;
+    uint64_t id;  // id==0 means it was cancelled
+    std::function<std::pair<bool, int64_t>(bool)> handler;
+    bool operator>(const WorkItem& other) const { return end > other.end; }
+  };
+
+  std::mutex m_mtx;
+  // Inheriting from priority_queue, so we can access the internal container
+  class Queue : public std::priority_queue<WorkItem, std::vector<WorkItem>,
+                                           std::greater<WorkItem>> {
+   public:
+    std::vector<WorkItem>& getContainer() { return this->c; }
+  } m_items;
+  ROCKSDB_NAMESPACE::port::Thread m_th;
+  bool closed_ = false;
+};
diff --git a/src/rocksdb/util/timer_queue_test.cc b/src/rocksdb/util/timer_queue_test.cc
new file mode 100644
index 000000000..5f5f08f21
--- /dev/null
+++ b/src/rocksdb/util/timer_queue_test.cc
@@ -0,0 +1,72 @@
+//  Portions Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+// borrowed from
+// http://www.crazygaze.com/blog/2016/03/24/portable-c-timer-queue/
+// Timer Queue
+//
+// License
+//
+// The source code in this article is licensed under the CC0 license, so feel
+// free
+// to copy, modify, share, do whatever you want with it.
+// No attribution is required, but Ill be happy if you do.
+// CC0 license
+
+// The person who associated a work with this deed has dedicated the work to the
+// public domain by waiving all of his or her rights to the work worldwide
+// under copyright law, including all related and neighboring rights, to the
+// extent allowed by law.  You can copy, modify, distribute and perform the
+// work, even for
+// commercial purposes, all without asking permission. See Other Information
+// below.
+//
+
+#include "util/timer_queue.h"
+#include <future>
+
+namespace Timing {
+
+using Clock = std::chrono::high_resolution_clock;
+double now() {
+  static auto start = Clock::now();
+  return std::chrono::duration<double, std::milli>(Clock::now() - start)
+      .count();
+}
+
+}  // namespace Timing
+
+int main() {
+  TimerQueue q;
+
+  double tnow = Timing::now();
+
+  q.add(10000, [tnow](bool aborted) mutable {
+    printf("T 1: %d, Elapsed %4.2fms\n", aborted, Timing::now() - tnow);
+    return std::make_pair(false, 0);
+  });
+  q.add(10001, [tnow](bool aborted) mutable {
+    printf("T 2: %d, Elapsed %4.2fms\n", aborted, Timing::now() - tnow);
+    return std::make_pair(false, 0);
+  });
+
+  q.add(1000, [tnow](bool aborted) mutable {
+    printf("T 3: %d, Elapsed %4.2fms\n", aborted, Timing::now() - tnow);
+    return std::make_pair(!aborted, 1000);
+  });
+
+  auto id = q.add(2000, [tnow](bool aborted) mutable {
+    printf("T 4: %d, Elapsed %4.2fms\n", aborted, Timing::now() - tnow);
+    return std::make_pair(!aborted, 2000);
+  });
+
+  (void)id;
+  // auto ret = q.cancel(id);
+  // assert(ret == 1);
+  // q.cancelAll();
+
+  return 0;
+}
+//////////////////////////////////////////
diff --git a/src/rocksdb/util/user_comparator_wrapper.h b/src/rocksdb/util/user_comparator_wrapper.h
new file mode 100644
index 000000000..fdb27f33e
--- /dev/null
+++ b/src/rocksdb/util/user_comparator_wrapper.h
@@ -0,0 +1,65 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+
+#include "monitoring/perf_context_imp.h"
+#include "rocksdb/comparator.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Wrapper of user comparator, with auto increment to
+// perf_context.user_key_comparison_count.
+class UserComparatorWrapper final : public Comparator {
+ public:
+  explicit UserComparatorWrapper(const Comparator* const user_cmp)
+      : user_comparator_(user_cmp) {}
+  
+  ~UserComparatorWrapper() = default;
+
+  const Comparator* user_comparator() const { return user_comparator_; }
+
+  int Compare(const Slice& a, const Slice& b) const override {
+    PERF_COUNTER_ADD(user_key_comparison_count, 1);
+    return user_comparator_->Compare(a, b);
+  }
+
+  bool Equal(const Slice& a, const Slice& b) const override {
+    PERF_COUNTER_ADD(user_key_comparison_count, 1);
+    return user_comparator_->Equal(a, b);
+  }
+
+  const char* Name() const override { return user_comparator_->Name(); }
+
+  void FindShortestSeparator(std::string* start,
+                             const Slice& limit) const override {
+    return user_comparator_->FindShortestSeparator(start, limit);
+  }
+
+  void FindShortSuccessor(std::string* key) const override {
+    return user_comparator_->FindShortSuccessor(key);
+  }
+
+  const Comparator* GetRootComparator() const override {
+    return user_comparator_->GetRootComparator();
+  }
+
+  bool IsSameLengthImmediateSuccessor(const Slice& s,
+                                      const Slice& t) const override {
+    return user_comparator_->IsSameLengthImmediateSuccessor(s, t);
+  }
+
+  bool CanKeysWithDifferentByteContentsBeEqual() const override {
+    return user_comparator_->CanKeysWithDifferentByteContentsBeEqual();
+  }
+
+ private:
+  const Comparator* user_comparator_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/util.h b/src/rocksdb/util/util.h
new file mode 100644
index 000000000..a5fd36490
--- /dev/null
+++ b/src/rocksdb/util/util.h
@@ -0,0 +1,16 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#ifndef FALLTHROUGH_INTENDED
+#if defined(__clang__)
+#define FALLTHROUGH_INTENDED [[clang::fallthrough]]
+#elif defined(__GNUC__) && __GNUC__ >= 7
+#define FALLTHROUGH_INTENDED [[gnu::fallthrough]]
+#else
+#define FALLTHROUGH_INTENDED do {} while (0)
+#endif
+#endif
diff --git a/src/rocksdb/util/vector_iterator.h b/src/rocksdb/util/vector_iterator.h
new file mode 100644
index 000000000..fc26ec0c0
--- /dev/null
+++ b/src/rocksdb/util/vector_iterator.h
@@ -0,0 +1,101 @@
+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+#pragma once
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include "db/dbformat.h"
+#include "rocksdb/iterator.h"
+#include "rocksdb/slice.h"
+#include "table/internal_iterator.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Iterator over a vector of keys/values
+class VectorIterator : public InternalIterator {
+ public:
+  VectorIterator(std::vector<std::string> keys, std::vector<std::string> values,
+                 const InternalKeyComparator* icmp)
+      : keys_(std::move(keys)),
+        values_(std::move(values)),
+        indexed_cmp_(icmp, &keys_),
+        current_(0) {
+    assert(keys_.size() == values_.size());
+
+    indices_.reserve(keys_.size());
+    for (size_t i = 0; i < keys_.size(); i++) {
+      indices_.push_back(i);
+    }
+    std::sort(indices_.begin(), indices_.end(), indexed_cmp_);
+  }
+
+  virtual bool Valid() const override {
+    return !indices_.empty() && current_ < indices_.size();
+  }
+
+  virtual void SeekToFirst() override { current_ = 0; }
+  virtual void SeekToLast() override { current_ = indices_.size() - 1; }
+
+  virtual void Seek(const Slice& target) override {
+    current_ = std::lower_bound(indices_.begin(), indices_.end(), target,
+                                indexed_cmp_) -
+               indices_.begin();
+  }
+
+  virtual void SeekForPrev(const Slice& target) override {
+    current_ = std::lower_bound(indices_.begin(), indices_.end(), target,
+                                indexed_cmp_) -
+               indices_.begin();
+    if (!Valid()) {
+      SeekToLast();
+    } else {
+      Prev();
+    }
+  }
+
+  virtual void Next() override { current_++; }
+  virtual void Prev() override { current_--; }
+
+  virtual Slice key() const override {
+    return Slice(keys_[indices_[current_]]);
+  }
+  virtual Slice value() const override {
+    return Slice(values_[indices_[current_]]);
+  }
+
+  virtual Status status() const override { return Status::OK(); }
+
+  virtual bool IsKeyPinned() const override { return true; }
+  virtual bool IsValuePinned() const override { return true; }
+
+ private:
+  struct IndexedKeyComparator {
+    IndexedKeyComparator(const InternalKeyComparator* c,
+                         const std::vector<std::string>* ks)
+        : cmp(c), keys(ks) {}
+
+    bool operator()(size_t a, size_t b) const {
+      return cmp->Compare((*keys)[a], (*keys)[b]) < 0;
+    }
+
+    bool operator()(size_t a, const Slice& b) const {
+      return cmp->Compare((*keys)[a], b) < 0;
+    }
+
+    bool operator()(const Slice& a, size_t b) const {
+      return cmp->Compare(a, (*keys)[b]) < 0;
+    }
+
+    const InternalKeyComparator* cmp;
+    const std::vector<std::string>* keys;
+  };
+
+  std::vector<std::string> keys_;
+  std::vector<std::string> values_;
+  IndexedKeyComparator indexed_cmp_;
+  std::vector<size_t> indices_;
+  size_t current_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
diff --git a/src/rocksdb/util/xxh3p.h b/src/rocksdb/util/xxh3p.h
new file mode 100644
index 000000000..0a3cd9808
--- /dev/null
+++ b/src/rocksdb/util/xxh3p.h
@@ -0,0 +1,1648 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+/*
+   xxHash - Extremely Fast Hash algorithm
+   Development source file for `xxh3`
+   Copyright (C) 2019-present, Yann Collet.
+
+   BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions are
+   met:
+
+       * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+       * Redistributions in binary form must reproduce the above
+   copyright notice, this list of conditions and the following disclaimer
+   in the documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+   You can contact the author at :
+   - xxHash source repository : https://github.com/Cyan4973/xxHash
+*/
+
+/* RocksDB Note: This file contains a preview release (xxhash repository
+   version 0.7.2) of XXH3 that is unlikely to be compatible with the final
+   version of XXH3. We have therefore renamed this XXH3p ("preview"), for
+   clarity so that we can continue to use this version even after
+   integrating a newer incompatible version.
+*/
+
+/* Note :
+   This file is separated for development purposes.
+   It will be integrated into `xxhash.c` when development phase is complete.
+*/
+
+#ifndef XXH3p_H
+#define XXH3p_H
+
+
+/* ===   Dependencies   === */
+
+#undef XXH_INLINE_ALL   /* in case it's already defined */
+#define XXH_INLINE_ALL
+#include "xxhash.h"
+
+
+/* ===   Compiler specifics   === */
+
+#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* >= C99 */
+#  define XXH_RESTRICT   restrict
+#else
+/* note : it might be useful to define __restrict or __restrict__ for some C++ compilers */
+#  define XXH_RESTRICT   /* disable */
+#endif
+
+#if defined(__GNUC__)
+#  if defined(__AVX2__)
+#    include <immintrin.h>
+#  elif defined(__SSE2__)
+#    include <emmintrin.h>
+#  elif defined(__ARM_NEON__) || defined(__ARM_NEON)
+#    define inline __inline__  /* clang bug */
+#    include <arm_neon.h>
+#    undef inline
+#  endif
+#elif defined(_MSC_VER)
+#  include <intrin.h>
+#endif
+
+/*
+ * Sanity check.
+ *
+ * XXH3 only requires these features to be efficient:
+ *
+ *  - Usable unaligned access
+ *  - A 32-bit or 64-bit ALU
+ *      - If 32-bit, a decent ADC instruction
+ *  - A 32 or 64-bit multiply with a 64-bit result
+ *
+ * Almost all 32-bit and 64-bit targets meet this, except for Thumb-1, the
+ * classic 16-bit only subset of ARM's instruction set.
+ *
+ * First of all, Thumb-1 lacks support for the UMULL instruction which
+ * performs the important long multiply. This means numerous __aeabi_lmul
+ * calls.
+ *
+ * Second of all, the 8 functional registers are just not enough.
+ * Setup for __aeabi_lmul, byteshift loads, pointers, and all arithmetic need
+ * Lo registers, and this shuffling results in thousands more MOVs than A32.
+ *
+ * A32 and T32 don't have this limitation. They can access all 14 registers,
+ * do a 32->64 multiply with UMULL, and the flexible operand is helpful too.
+ *
+ * If compiling Thumb-1 for a target which supports ARM instructions, we
+ * will give a warning.
+ *
+ * Usually, if this happens, it is because of an accident and you probably
+ * need to specify -march, as you probably meant to compileh for a newer
+ * architecture.
+ */
+#if defined(__thumb__) && !defined(__thumb2__) && defined(__ARM_ARCH_ISA_ARM)
+#   warning "XXH3 is highly inefficient without ARM or Thumb-2."
+#endif
+
+/* ==========================================
+ * Vectorization detection
+ * ========================================== */
+#define XXH_SCALAR 0
+#define XXH_SSE2   1
+#define XXH_AVX2   2
+#define XXH_NEON   3
+#define XXH_VSX    4
+
+#ifndef XXH_VECTOR    /* can be defined on command line */
+#  if defined(__AVX2__)
+#    define XXH_VECTOR XXH_AVX2
+#  elif defined(__SSE2__) || defined(_M_AMD64) || defined(_M_X64) || (defined(_M_IX86_FP) && (_M_IX86_FP == 2))
+#    define XXH_VECTOR XXH_SSE2
+#  elif defined(__GNUC__) /* msvc support maybe later */ \
+  && (defined(__ARM_NEON__) || defined(__ARM_NEON)) \
+  && (defined(__LITTLE_ENDIAN__) /* We only support little endian NEON */ \
+    || (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__))
+#    define XXH_VECTOR XXH_NEON
+#  elif defined(__PPC64__) && defined(__POWER8_VECTOR__) && defined(__GNUC__)
+#    define XXH_VECTOR XXH_VSX
+#  else
+#    define XXH_VECTOR XXH_SCALAR
+#  endif
+#endif
+
+/* control alignment of accumulator,
+ * for compatibility with fast vector loads */
+#ifndef XXH_ACC_ALIGN
+#  if XXH_VECTOR == 0   /* scalar */
+#     define XXH_ACC_ALIGN 8
+#  elif XXH_VECTOR == 1  /* sse2 */
+#     define XXH_ACC_ALIGN 16
+#  elif XXH_VECTOR == 2  /* avx2 */
+#     define XXH_ACC_ALIGN 32
+#  elif XXH_VECTOR == 3  /* neon */
+#     define XXH_ACC_ALIGN 16
+#  elif XXH_VECTOR == 4  /* vsx */
+#     define XXH_ACC_ALIGN 16
+#  endif
+#endif
+
+/* xxh_u64 XXH_mult32to64(xxh_u32 a, xxh_u64 b) { return (xxh_u64)a * (xxh_u64)b; } */
+#if defined(_MSC_VER) && defined(_M_IX86)
+#    include <intrin.h>
+#    define XXH_mult32to64(x, y) __emulu(x, y)
+#else
+#    define XXH_mult32to64(x, y) ((xxh_u64)((x) & 0xFFFFFFFF) * (xxh_u64)((y) & 0xFFFFFFFF))
+#endif
+
+/* VSX stuff. It's a lot because VSX support is mediocre across compilers and
+ * there is a lot of mischief with endianness. */
+#if XXH_VECTOR == XXH_VSX
+#  include <altivec.h>
+#  undef vector
+typedef __vector unsigned long long U64x2;
+typedef __vector unsigned char U8x16;
+typedef __vector unsigned U32x4;
+
+#ifndef XXH_VSX_BE
+#  if defined(__BIG_ENDIAN__) \
+  || (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#    define XXH_VSX_BE 1
+#  elif defined(__VEC_ELEMENT_REG_ORDER__) && __VEC_ELEMENT_REG_ORDER__ == __ORDER_BIG_ENDIAN__
+#    warning "-maltivec=be is not recommended. Please use native endianness."
+#    define XXH_VSX_BE 1
+#  else
+#    define XXH_VSX_BE 0
+#  endif
+#endif
+
+/* We need some helpers for big endian mode. */
+#if XXH_VSX_BE
+/* A wrapper for POWER9's vec_revb. */
+#  ifdef __POWER9_VECTOR__
+#    define XXH_vec_revb vec_revb
+#  else
+XXH_FORCE_INLINE U64x2 XXH_vec_revb(U64x2 val)
+{
+    U8x16 const vByteSwap = { 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01, 0x00,
+                              0x0F, 0x0E, 0x0D, 0x0C, 0x0B, 0x0A, 0x09, 0x08 };
+    return vec_perm(val, val, vByteSwap);
+}
+#  endif
+
+/* Power8 Crypto gives us vpermxor which is very handy for
+ * PPC64EB.
+ *
+ * U8x16 vpermxor(U8x16 a, U8x16 b, U8x16 mask)
+ * {
+ *     U8x16 ret;
+ *     for (int i = 0; i < 16; i++) {
+ *         ret[i] = a[mask[i] & 0xF] ^ b[mask[i] >> 4];
+ *     }
+ *     return ret;
+ * }
+ *
+ * Because both of the main loops load the key, swap, and xor it with input,
+ * we can combine the key swap into this instruction.
+ */
+#  ifdef vec_permxor
+#    define XXH_vec_permxor vec_permxor
+#  else
+#    define XXH_vec_permxor __builtin_crypto_vpermxor
+#  endif
+#endif  /* XXH_VSX_BE */
+/*
+ * Because we reinterpret the multiply, there are endian memes: vec_mulo actually becomes
+ * vec_mule.
+ *
+ * Additionally, the intrinsic wasn't added until GCC 8, despite existing for a while.
+ * Clang has an easy way to control this, we can just use the builtin which doesn't swap.
+ * GCC needs inline assembly. */
+#if __has_builtin(__builtin_altivec_vmuleuw)
+#  define XXH_vec_mulo __builtin_altivec_vmulouw
+#  define XXH_vec_mule __builtin_altivec_vmuleuw
+#else
+/* Adapted from https://github.com/google/highwayhash/blob/master/highwayhash/hh_vsx.h. */
+XXH_FORCE_INLINE U64x2 XXH_vec_mulo(U32x4 a, U32x4 b) {
+    U64x2 result;
+    __asm__("vmulouw %0, %1, %2" : "=v" (result) : "v" (a), "v" (b));
+    return result;
+}
+XXH_FORCE_INLINE U64x2 XXH_vec_mule(U32x4 a, U32x4 b) {
+    U64x2 result;
+    __asm__("vmuleuw %0, %1, %2" : "=v" (result) : "v" (a), "v" (b));
+    return result;
+}
+#endif /* __has_builtin(__builtin_altivec_vmuleuw) */
+#endif /* XXH_VECTOR == XXH_VSX */
+
+/* prefetch
+ * can be disabled, by declaring XXH_NO_PREFETCH build macro */
+#if defined(XXH_NO_PREFETCH)
+#  define XXH_PREFETCH(ptr)  (void)(ptr)  /* disabled */
+#else
+#  if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_I86))  /* _mm_prefetch() is not defined outside of x86/x64 */
+#    include <mmintrin.h>   /* https://msdn.microsoft.com/fr-fr/library/84szxsww(v=vs.90).aspx */
+#    define XXH_PREFETCH(ptr)  _mm_prefetch((const char*)(ptr), _MM_HINT_T0)
+#  elif defined(__GNUC__) && ( (__GNUC__ >= 4) || ( (__GNUC__ == 3) && (__GNUC_MINOR__ >= 1) ) )
+#    define XXH_PREFETCH(ptr)  __builtin_prefetch((ptr), 0 /* rw==read */, 3 /* locality */)
+#  else
+#    define XXH_PREFETCH(ptr) (void)(ptr)  /* disabled */
+#  endif
+#endif  /* XXH_NO_PREFETCH */
+
+
+/* ==========================================
+ * XXH3 default settings
+ * ========================================== */
+
+#define XXH_SECRET_DEFAULT_SIZE 192   /* minimum XXH3p_SECRET_SIZE_MIN */
+
+#if (XXH_SECRET_DEFAULT_SIZE < XXH3p_SECRET_SIZE_MIN)
+#  error "default keyset is not large enough"
+#endif
+
+XXH_ALIGN(64) static const xxh_u8 kSecret[XXH_SECRET_DEFAULT_SIZE] = {
+    0xb8, 0xfe, 0x6c, 0x39, 0x23, 0xa4, 0x4b, 0xbe, 0x7c, 0x01, 0x81, 0x2c, 0xf7, 0x21, 0xad, 0x1c,
+    0xde, 0xd4, 0x6d, 0xe9, 0x83, 0x90, 0x97, 0xdb, 0x72, 0x40, 0xa4, 0xa4, 0xb7, 0xb3, 0x67, 0x1f,
+    0xcb, 0x79, 0xe6, 0x4e, 0xcc, 0xc0, 0xe5, 0x78, 0x82, 0x5a, 0xd0, 0x7d, 0xcc, 0xff, 0x72, 0x21,
+    0xb8, 0x08, 0x46, 0x74, 0xf7, 0x43, 0x24, 0x8e, 0xe0, 0x35, 0x90, 0xe6, 0x81, 0x3a, 0x26, 0x4c,
+    0x3c, 0x28, 0x52, 0xbb, 0x91, 0xc3, 0x00, 0xcb, 0x88, 0xd0, 0x65, 0x8b, 0x1b, 0x53, 0x2e, 0xa3,
+    0x71, 0x64, 0x48, 0x97, 0xa2, 0x0d, 0xf9, 0x4e, 0x38, 0x19, 0xef, 0x46, 0xa9, 0xde, 0xac, 0xd8,
+    0xa8, 0xfa, 0x76, 0x3f, 0xe3, 0x9c, 0x34, 0x3f, 0xf9, 0xdc, 0xbb, 0xc7, 0xc7, 0x0b, 0x4f, 0x1d,
+    0x8a, 0x51, 0xe0, 0x4b, 0xcd, 0xb4, 0x59, 0x31, 0xc8, 0x9f, 0x7e, 0xc9, 0xd9, 0x78, 0x73, 0x64,
+
+    0xea, 0xc5, 0xac, 0x83, 0x34, 0xd3, 0xeb, 0xc3, 0xc5, 0x81, 0xa0, 0xff, 0xfa, 0x13, 0x63, 0xeb,
+    0x17, 0x0d, 0xdd, 0x51, 0xb7, 0xf0, 0xda, 0x49, 0xd3, 0x16, 0x55, 0x26, 0x29, 0xd4, 0x68, 0x9e,
+    0x2b, 0x16, 0xbe, 0x58, 0x7d, 0x47, 0xa1, 0xfc, 0x8f, 0xf8, 0xb8, 0xd1, 0x7a, 0xd0, 0x31, 0xce,
+    0x45, 0xcb, 0x3a, 0x8f, 0x95, 0x16, 0x04, 0x28, 0xaf, 0xd7, 0xfb, 0xca, 0xbb, 0x4b, 0x40, 0x7e,
+};
+
+/*
+ * GCC for x86 has a tendency to use SSE in this loop. While it
+ * successfully avoids swapping (as MUL overwrites EAX and EDX), it
+ * slows it down because instead of free register swap shifts, it
+ * must use pshufd and punpckl/hd.
+ *
+ * To prevent this, we use this attribute to shut off SSE.
+ */
+#if defined(__GNUC__) && !defined(__clang__) && defined(__i386__)
+__attribute__((__target__("no-sse")))
+#endif
+static XXH128_hash_t
+XXH_mult64to128(xxh_u64 lhs, xxh_u64 rhs)
+{
+    /*
+     * GCC/Clang __uint128_t method.
+     *
+     * On most 64-bit targets, GCC and Clang define a __uint128_t type.
+     * This is usually the best way as it usually uses a native long 64-bit
+     * multiply, such as MULQ on x86_64 or MUL + UMULH on aarch64.
+     *
+     * Usually.
+     *
+     * Despite being a 32-bit platform, Clang (and emscripten) define this
+     * type despite not having the arithmetic for it. This results in a
+     * laggy compiler builtin call which calculates a full 128-bit multiply.
+     * In that case it is best to use the portable one.
+     * https://github.com/Cyan4973/xxHash/issues/211#issuecomment-515575677
+     */
+#if defined(__GNUC__) && !defined(__wasm__) \
+    && defined(__SIZEOF_INT128__) \
+    || (defined(_INTEGRAL_MAX_BITS) && _INTEGRAL_MAX_BITS >= 128)
+
+    __uint128_t product = (__uint128_t)lhs * (__uint128_t)rhs;
+    XXH128_hash_t const r128 = { (xxh_u64)(product), (xxh_u64)(product >> 64) };
+    return r128;
+
+    /*
+     * MSVC for x64's _umul128 method.
+     *
+     * xxh_u64 _umul128(xxh_u64 Multiplier, xxh_u64 Multiplicand, xxh_u64 *HighProduct);
+     *
+     * This compiles to single operand MUL on x64.
+     */
+#elif defined(_M_X64) || defined(_M_IA64)
+
+#ifndef _MSC_VER
+#   pragma intrinsic(_umul128)
+#endif
+    xxh_u64 product_high;
+    xxh_u64 const product_low = _umul128(lhs, rhs, &product_high);
+    XXH128_hash_t const r128 = { product_low, product_high };
+    return r128;
+
+#else
+    /*
+     * Portable scalar method. Optimized for 32-bit and 64-bit ALUs.
+     *
+     * This is a fast and simple grade school multiply, which is shown
+     * below with base 10 arithmetic instead of base 0x100000000.
+     *
+     *           9 3 // D2 lhs = 93
+     *         x 7 5 // D2 rhs = 75
+     *     ----------
+     *           1 5 // D2 lo_lo = (93 % 10) * (75 % 10)
+     *         4 5 | // D2 hi_lo = (93 / 10) * (75 % 10)
+     *         2 1 | // D2 lo_hi = (93 % 10) * (75 / 10)
+     *     + 6 3 | | // D2 hi_hi = (93 / 10) * (75 / 10)
+     *     ---------
+     *         2 7 | // D2 cross  = (15 / 10) + (45 % 10) + 21
+     *     + 6 7 | | // D2 upper  = (27 / 10) + (45 / 10) + 63
+     *     ---------
+     *       6 9 7 5
+     *
+     * The reasons for adding the products like this are:
+     *  1. It avoids manual carry tracking. Just like how
+     *     (9 * 9) + 9 + 9 = 99, the same applies with this for
+     *     UINT64_MAX. This avoids a lot of complexity.
+     *
+     *  2. It hints for, and on Clang, compiles to, the powerful UMAAL
+     *     instruction available in ARMv6+ A32/T32, which is shown below:
+     *
+     *         void UMAAL(xxh_u32 *RdLo, xxh_u32 *RdHi, xxh_u32 Rn, xxh_u32 Rm)
+     *         {
+     *             xxh_u64 product = (xxh_u64)*RdLo * (xxh_u64)*RdHi + Rn + Rm;
+     *             *RdLo = (xxh_u32)(product & 0xFFFFFFFF);
+     *             *RdHi = (xxh_u32)(product >> 32);
+     *         }
+     *
+     *     This instruction was designed for efficient long multiplication,
+     *     and allows this to be calculated in only 4 instructions which
+     *     is comparable to some 64-bit ALUs.
+     *
+     *  3. It isn't terrible on other platforms. Usually this will be
+     *     a couple of 32-bit ADD/ADCs.
+     */
+
+    /* First calculate all of the cross products. */
+    xxh_u64 const lo_lo = XXH_mult32to64(lhs & 0xFFFFFFFF, rhs & 0xFFFFFFFF);
+    xxh_u64 const hi_lo = XXH_mult32to64(lhs >> 32,        rhs & 0xFFFFFFFF);
+    xxh_u64 const lo_hi = XXH_mult32to64(lhs & 0xFFFFFFFF, rhs >> 32);
+    xxh_u64 const hi_hi = XXH_mult32to64(lhs >> 32,        rhs >> 32);
+
+    /* Now add the products together. These will never overflow. */
+    xxh_u64 const cross = (lo_lo >> 32) + (hi_lo & 0xFFFFFFFF) + lo_hi;
+    xxh_u64 const upper = (hi_lo >> 32) + (cross >> 32)        + hi_hi;
+    xxh_u64 const lower = (cross << 32) | (lo_lo & 0xFFFFFFFF);
+
+    XXH128_hash_t r128 = { lower, upper };
+    return r128;
+#endif
+}
+
+/*
+ * We want to keep the attribute here because a target switch
+ * disables inlining.
+ *
+ * Does a 64-bit to 128-bit multiply, then XOR folds it.
+ * The reason for the separate function is to prevent passing
+ * too many structs around by value. This will hopefully inline
+ * the multiply, but we don't force it.
+ */
+#if defined(__GNUC__) && !defined(__clang__) && defined(__i386__)
+__attribute__((__target__("no-sse")))
+#endif
+static xxh_u64
+XXH3p_mul128_fold64(xxh_u64 lhs, xxh_u64 rhs)
+{
+    XXH128_hash_t product = XXH_mult64to128(lhs, rhs);
+    return product.low64 ^ product.high64;
+}
+
+
+static XXH64_hash_t XXH3p_avalanche(xxh_u64 h64)
+{
+    h64 ^= h64 >> 37;
+    h64 *= PRIME64_3;
+    h64 ^= h64 >> 32;
+    return h64;
+}
+
+
+/* ==========================================
+ * Short keys
+ * ========================================== */
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_len_1to3_64b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(1 <= len && len <= 3);
+    XXH_ASSERT(secret != NULL);
+    {   xxh_u8 const c1 = input[0];
+        xxh_u8 const c2 = input[len >> 1];
+        xxh_u8 const c3 = input[len - 1];
+        xxh_u32  const combined = ((xxh_u32)c1) | (((xxh_u32)c2) << 8) | (((xxh_u32)c3) << 16) | (((xxh_u32)len) << 24);
+        xxh_u64  const keyed = (xxh_u64)combined ^ (XXH_readLE32(secret) + seed);
+        xxh_u64  const mixed = keyed * PRIME64_1;
+        return XXH3p_avalanche(mixed);
+    }
+}
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_len_4to8_64b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(secret != NULL);
+    XXH_ASSERT(4 <= len && len <= 8);
+    {   xxh_u32 const input_lo = XXH_readLE32(input);
+        xxh_u32 const input_hi = XXH_readLE32(input + len - 4);
+        xxh_u64 const input_64 = input_lo | ((xxh_u64)input_hi << 32);
+        xxh_u64 const keyed = input_64 ^ (XXH_readLE64(secret) + seed);
+        xxh_u64 const mix64 = len + ((keyed ^ (keyed >> 51)) * PRIME32_1);
+        return XXH3p_avalanche((mix64 ^ (mix64 >> 47)) * PRIME64_2);
+    }
+}
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_len_9to16_64b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(secret != NULL);
+    XXH_ASSERT(9 <= len && len <= 16);
+    {   xxh_u64 const input_lo = XXH_readLE64(input)           ^ (XXH_readLE64(secret)     + seed);
+        xxh_u64 const input_hi = XXH_readLE64(input + len - 8) ^ (XXH_readLE64(secret + 8) - seed);
+        xxh_u64 const acc = len + (input_lo + input_hi) + XXH3p_mul128_fold64(input_lo, input_hi);
+        return XXH3p_avalanche(acc);
+    }
+}
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_len_0to16_64b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(len <= 16);
+    {   if (len > 8) return XXH3p_len_9to16_64b(input, len, secret, seed);
+        if (len >= 4) return XXH3p_len_4to8_64b(input, len, secret, seed);
+        if (len) return XXH3p_len_1to3_64b(input, len, secret, seed);
+        /*
+         * RocksDB modification from XXH3 preview: zero result for empty
+         * string can be problematic for multiplication-based algorithms.
+         * Return a hash of the seed instead.
+         */
+        return XXH3p_mul128_fold64(seed + XXH_readLE64(secret), PRIME64_2);
+    }
+}
+
+
+/* ===    Long Keys    === */
+
+#define STRIPE_LEN 64
+#define XXH_SECRET_CONSUME_RATE 8   /* nb of secret bytes consumed at each accumulation */
+#define ACC_NB (STRIPE_LEN / sizeof(xxh_u64))
+
+typedef enum { XXH3p_acc_64bits, XXH3p_acc_128bits } XXH3p_accWidth_e;
+
+XXH_FORCE_INLINE void
+XXH3p_accumulate_512(      void* XXH_RESTRICT acc,
+                    const void* XXH_RESTRICT input,
+                    const void* XXH_RESTRICT secret,
+                    XXH3p_accWidth_e accWidth)
+{
+#if (XXH_VECTOR == XXH_AVX2)
+
+    XXH_ASSERT((((size_t)acc) & 31) == 0);
+    {   XXH_ALIGN(32) __m256i* const xacc  =       (__m256i *) acc;
+        const         __m256i* const xinput = (const __m256i *) input;  /* not really aligned, just for ptr arithmetic, and because _mm256_loadu_si256() requires this type */
+        const         __m256i* const xsecret = (const __m256i *) secret;   /* not really aligned, just for ptr arithmetic, and because _mm256_loadu_si256() requires this type */
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN/sizeof(__m256i); i++) {
+            __m256i const data_vec = _mm256_loadu_si256 (xinput+i);
+            __m256i const key_vec = _mm256_loadu_si256 (xsecret+i);
+            __m256i const data_key = _mm256_xor_si256 (data_vec, key_vec);                                  /* uint32 dk[8]  = {d0+k0, d1+k1, d2+k2, d3+k3, ...} */
+            __m256i const product = _mm256_mul_epu32 (data_key, _mm256_shuffle_epi32 (data_key, 0x31));  /* uint64 mul[4] = {dk0*dk1, dk2*dk3, ...} */
+            if (accWidth == XXH3p_acc_128bits) {
+                __m256i const data_swap = _mm256_shuffle_epi32(data_vec, _MM_SHUFFLE(1,0,3,2));
+                __m256i const sum = _mm256_add_epi64(xacc[i], data_swap);
+                xacc[i]  = _mm256_add_epi64(product, sum);
+            } else {  /* XXH3p_acc_64bits */
+                __m256i const sum = _mm256_add_epi64(xacc[i], data_vec);
+                xacc[i]  = _mm256_add_epi64(product, sum);
+            }
+    }   }
+
+#elif (XXH_VECTOR == XXH_SSE2)
+
+    XXH_ASSERT((((size_t)acc) & 15) == 0);
+    {   XXH_ALIGN(16) __m128i* const xacc  =       (__m128i *) acc;
+        const         __m128i* const xinput = (const __m128i *) input;  /* not really aligned, just for ptr arithmetic, and because _mm_loadu_si128() requires this type */
+        const         __m128i* const xsecret = (const __m128i *) secret;   /* not really aligned, just for ptr arithmetic, and because _mm_loadu_si128() requires this type */
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN/sizeof(__m128i); i++) {
+            __m128i const data_vec = _mm_loadu_si128 (xinput+i);
+            __m128i const key_vec = _mm_loadu_si128 (xsecret+i);
+            __m128i const data_key = _mm_xor_si128 (data_vec, key_vec);                                  /* uint32 dk[8]  = {d0+k0, d1+k1, d2+k2, d3+k3, ...} */
+            __m128i const product = _mm_mul_epu32 (data_key, _mm_shuffle_epi32 (data_key, 0x31));  /* uint64 mul[4] = {dk0*dk1, dk2*dk3, ...} */
+            if (accWidth == XXH3p_acc_128bits) {
+                __m128i const data_swap = _mm_shuffle_epi32(data_vec, _MM_SHUFFLE(1,0,3,2));
+                __m128i const sum = _mm_add_epi64(xacc[i], data_swap);
+                xacc[i]  = _mm_add_epi64(product, sum);
+            } else {  /* XXH3p_acc_64bits */
+                __m128i const sum = _mm_add_epi64(xacc[i], data_vec);
+                xacc[i]  = _mm_add_epi64(product, sum);
+            }
+    }   }
+
+#elif (XXH_VECTOR == XXH_NEON)
+
+    XXH_ASSERT((((size_t)acc) & 15) == 0);
+    {
+        XXH_ALIGN(16) uint64x2_t* const xacc = (uint64x2_t *) acc;
+        /* We don't use a uint32x4_t pointer because it causes bus errors on ARMv7. */
+        uint8_t const* const xinput = (const uint8_t *) input;
+        uint8_t const* const xsecret  = (const uint8_t *) secret;
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN / sizeof(uint64x2_t); i++) {
+#if !defined(__aarch64__) && !defined(__arm64__) && defined(__GNUC__) /* ARM32-specific hack */
+            /* vzip on ARMv7 Clang generates a lot of vmovs (technically vorrs) without this.
+             * vzip on 32-bit ARM NEON will overwrite the original register, and I think that Clang
+             * assumes I don't want to destroy it and tries to make a copy. This slows down the code
+             * a lot.
+             * aarch64 not only uses an entirely different syntax, but it requires three
+             * instructions...
+             *    ext    v1.16B, v0.16B, #8    // select high bits because aarch64 can't address them directly
+             *    zip1   v3.2s, v0.2s, v1.2s   // first zip
+             *    zip2   v2.2s, v0.2s, v1.2s   // second zip
+             * ...to do what ARM does in one:
+             *    vzip.32 d0, d1               // Interleave high and low bits and overwrite. */
+
+            /* data_vec = xsecret[i]; */
+            uint8x16_t const data_vec    = vld1q_u8(xinput + (i * 16));
+            /* key_vec  = xsecret[i];  */
+            uint8x16_t const key_vec     = vld1q_u8(xsecret  + (i * 16));
+            /* data_key = data_vec ^ key_vec; */
+            uint32x4_t       data_key;
+
+            if (accWidth == XXH3p_acc_64bits) {
+                /* Add first to prevent register swaps */
+                /* xacc[i] += data_vec; */
+                xacc[i] = vaddq_u64 (xacc[i], vreinterpretq_u64_u8(data_vec));
+            } else {  /* XXH3p_acc_128bits */
+                /* xacc[i] += swap(data_vec); */
+                /* can probably be optimized better */
+                uint64x2_t const data64 = vreinterpretq_u64_u8(data_vec);
+                uint64x2_t const swapped= vextq_u64(data64, data64, 1);
+                xacc[i] = vaddq_u64 (xacc[i], swapped);
+            }
+
+            data_key = vreinterpretq_u32_u8(veorq_u8(data_vec, key_vec));
+
+            /* Here's the magic. We use the quirkiness of vzip to shuffle data_key in place.
+             * shuffle: data_key[0, 1, 2, 3] = data_key[0, 2, 1, 3] */
+            __asm__("vzip.32 %e0, %f0" : "+w" (data_key));
+            /* xacc[i] += (uint64x2_t) data_key[0, 1] * (uint64x2_t) data_key[2, 3]; */
+            xacc[i] = vmlal_u32(xacc[i], vget_low_u32(data_key), vget_high_u32(data_key));
+
+#else
+            /* On aarch64, vshrn/vmovn seems to be equivalent to, if not faster than, the vzip method. */
+
+            /* data_vec = xsecret[i]; */
+            uint8x16_t const data_vec    = vld1q_u8(xinput + (i * 16));
+            /* key_vec  = xsecret[i];  */
+            uint8x16_t const key_vec     = vld1q_u8(xsecret  + (i * 16));
+            /* data_key = data_vec ^ key_vec; */
+            uint64x2_t const data_key    = vreinterpretq_u64_u8(veorq_u8(data_vec, key_vec));
+            /* data_key_lo = (uint32x2_t) (data_key & 0xFFFFFFFF); */
+            uint32x2_t const data_key_lo = vmovn_u64  (data_key);
+            /* data_key_hi = (uint32x2_t) (data_key >> 32); */
+            uint32x2_t const data_key_hi = vshrn_n_u64 (data_key, 32);
+            if (accWidth == XXH3p_acc_64bits) {
+                /* xacc[i] += data_vec; */
+                xacc[i] = vaddq_u64 (xacc[i], vreinterpretq_u64_u8(data_vec));
+            } else {  /* XXH3p_acc_128bits */
+                /* xacc[i] += swap(data_vec); */
+                uint64x2_t const data64 = vreinterpretq_u64_u8(data_vec);
+                uint64x2_t const swapped= vextq_u64(data64, data64, 1);
+                xacc[i] = vaddq_u64 (xacc[i], swapped);
+            }
+            /* xacc[i] += (uint64x2_t) data_key_lo * (uint64x2_t) data_key_hi; */
+            xacc[i] = vmlal_u32 (xacc[i], data_key_lo, data_key_hi);
+
+#endif
+        }
+    }
+
+#elif (XXH_VECTOR == XXH_VSX)
+          U64x2* const xacc =        (U64x2*) acc;    /* presumed aligned */
+    U64x2 const* const xinput = (U64x2 const*) input;   /* no alignment restriction */
+    U64x2 const* const xsecret  = (U64x2 const*) secret;    /* no alignment restriction */
+    U64x2 const v32 = { 32,  32 };
+#if XXH_VSX_BE
+    U8x16 const vXorSwap  = { 0x07, 0x16, 0x25, 0x34, 0x43, 0x52, 0x61, 0x70,
+                              0x8F, 0x9E, 0xAD, 0xBC, 0xCB, 0xDA, 0xE9, 0xF8 };
+#endif
+    size_t i;
+    for (i = 0; i < STRIPE_LEN / sizeof(U64x2); i++) {
+        /* data_vec = xinput[i]; */
+        /* key_vec = xsecret[i]; */
+#if XXH_VSX_BE
+        /* byteswap */
+        U64x2 const data_vec = XXH_vec_revb(vec_vsx_ld(0, xinput + i));
+        U64x2 const key_raw = vec_vsx_ld(0, xsecret + i);
+        /* See comment above. data_key = data_vec ^ swap(xsecret[i]); */
+        U64x2 const data_key = (U64x2)XXH_vec_permxor((U8x16)data_vec, (U8x16)key_raw, vXorSwap);
+#else
+        U64x2 const data_vec = vec_vsx_ld(0, xinput + i);
+        U64x2 const key_vec = vec_vsx_ld(0, xsecret + i);
+        U64x2 const data_key = data_vec ^ key_vec;
+#endif
+        /* shuffled = (data_key << 32) | (data_key >> 32); */
+        U32x4 const shuffled = (U32x4)vec_rl(data_key, v32);
+        /* product = ((U64x2)data_key & 0xFFFFFFFF) * ((U64x2)shuffled & 0xFFFFFFFF); */
+        U64x2 const product = XXH_vec_mulo((U32x4)data_key, shuffled);
+        xacc[i] += product;
+
+        if (accWidth == XXH3p_acc_64bits) {
+            xacc[i] += data_vec;
+        } else {  /* XXH3p_acc_128bits */
+            /* swap high and low halves */
+            U64x2 const data_swapped = vec_xxpermdi(data_vec, data_vec, 2);
+            xacc[i] += data_swapped;
+        }
+    }
+
+#else   /* scalar variant of Accumulator - universal */
+
+    XXH_ALIGN(XXH_ACC_ALIGN) xxh_u64* const xacc = (xxh_u64*) acc;    /* presumed aligned on 32-bytes boundaries, little hint for the auto-vectorizer */
+    const xxh_u8* const xinput = (const xxh_u8*) input;  /* no alignment restriction */
+    const xxh_u8* const xsecret  = (const xxh_u8*) secret;   /* no alignment restriction */
+    size_t i;
+    XXH_ASSERT(((size_t)acc & (XXH_ACC_ALIGN-1)) == 0);
+    for (i=0; i < ACC_NB; i++) {
+        xxh_u64 const data_val = XXH_readLE64(xinput + 8*i);
+        xxh_u64 const data_key = data_val ^ XXH_readLE64(xsecret + i*8);
+
+        if (accWidth == XXH3p_acc_64bits) {
+            xacc[i] += data_val;
+        } else {
+            xacc[i ^ 1] += data_val; /* swap adjacent lanes */
+        }
+        xacc[i] += XXH_mult32to64(data_key & 0xFFFFFFFF, data_key >> 32);
+    }
+#endif
+}
+
+XXH_FORCE_INLINE void
+XXH3p_scrambleAcc(void* XXH_RESTRICT acc, const void* XXH_RESTRICT secret)
+{
+#if (XXH_VECTOR == XXH_AVX2)
+
+    XXH_ASSERT((((size_t)acc) & 31) == 0);
+    {   XXH_ALIGN(32) __m256i* const xacc = (__m256i*) acc;
+        const         __m256i* const xsecret = (const __m256i *) secret;   /* not really aligned, just for ptr arithmetic, and because _mm256_loadu_si256() requires this argument type */
+        const __m256i prime32 = _mm256_set1_epi32((int)PRIME32_1);
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN/sizeof(__m256i); i++) {
+            /* xacc[i] ^= (xacc[i] >> 47) */
+            __m256i const acc_vec     = xacc[i];
+            __m256i const shifted     = _mm256_srli_epi64    (acc_vec, 47);
+            __m256i const data_vec    = _mm256_xor_si256     (acc_vec, shifted);
+            /* xacc[i] ^= xsecret; */
+            __m256i const key_vec     = _mm256_loadu_si256   (xsecret+i);
+            __m256i const data_key    = _mm256_xor_si256     (data_vec, key_vec);
+
+            /* xacc[i] *= PRIME32_1; */
+            __m256i const data_key_hi = _mm256_shuffle_epi32 (data_key, 0x31);
+            __m256i const prod_lo     = _mm256_mul_epu32     (data_key, prime32);
+            __m256i const prod_hi     = _mm256_mul_epu32     (data_key_hi, prime32);
+            xacc[i] = _mm256_add_epi64(prod_lo, _mm256_slli_epi64(prod_hi, 32));
+        }
+    }
+
+#elif (XXH_VECTOR == XXH_SSE2)
+
+    XXH_ASSERT((((size_t)acc) & 15) == 0);
+    {   XXH_ALIGN(16) __m128i* const xacc = (__m128i*) acc;
+        const         __m128i* const xsecret = (const __m128i *) secret;   /* not really aligned, just for ptr arithmetic, and because _mm_loadu_si128() requires this argument type */
+        const __m128i prime32 = _mm_set1_epi32((int)PRIME32_1);
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN/sizeof(__m128i); i++) {
+            /* xacc[i] ^= (xacc[i] >> 47) */
+            __m128i const acc_vec     = xacc[i];
+            __m128i const shifted     = _mm_srli_epi64    (acc_vec, 47);
+            __m128i const data_vec    = _mm_xor_si128     (acc_vec, shifted);
+            /* xacc[i] ^= xsecret; */
+            __m128i const key_vec     = _mm_loadu_si128   (xsecret+i);
+            __m128i const data_key    = _mm_xor_si128     (data_vec, key_vec);
+
+            /* xacc[i] *= PRIME32_1; */
+            __m128i const data_key_hi = _mm_shuffle_epi32 (data_key, 0x31);
+            __m128i const prod_lo     = _mm_mul_epu32     (data_key, prime32);
+            __m128i const prod_hi     = _mm_mul_epu32     (data_key_hi, prime32);
+            xacc[i] = _mm_add_epi64(prod_lo, _mm_slli_epi64(prod_hi, 32));
+        }
+    }
+
+#elif (XXH_VECTOR == XXH_NEON)
+
+    XXH_ASSERT((((size_t)acc) & 15) == 0);
+
+    {   uint64x2_t* const xacc =     (uint64x2_t*) acc;
+        uint8_t const* const xsecret = (uint8_t const*) secret;
+        uint32x2_t const prime     = vdup_n_u32 (PRIME32_1);
+
+        size_t i;
+        for (i=0; i < STRIPE_LEN/sizeof(uint64x2_t); i++) {
+            /* data_vec = xacc[i] ^ (xacc[i] >> 47); */
+            uint64x2_t const   acc_vec  = xacc[i];
+            uint64x2_t const   shifted  = vshrq_n_u64 (acc_vec, 47);
+            uint64x2_t const   data_vec = veorq_u64   (acc_vec, shifted);
+
+            /* key_vec  = xsecret[i]; */
+            uint32x4_t const   key_vec  = vreinterpretq_u32_u8(vld1q_u8(xsecret + (i * 16)));
+            /* data_key = data_vec ^ key_vec; */
+            uint32x4_t const   data_key = veorq_u32   (vreinterpretq_u32_u64(data_vec), key_vec);
+            /* shuffled = { data_key[0, 2], data_key[1, 3] }; */
+            uint32x2x2_t const shuffled = vzip_u32    (vget_low_u32(data_key), vget_high_u32(data_key));
+
+            /* data_key *= PRIME32_1 */
+
+            /* prod_hi = (data_key >> 32) * PRIME32_1; */
+            uint64x2_t const   prod_hi = vmull_u32    (shuffled.val[1], prime);
+            /* xacc[i] = prod_hi << 32; */
+            xacc[i] = vshlq_n_u64(prod_hi, 32);
+            /* xacc[i] += (prod_hi & 0xFFFFFFFF) * PRIME32_1; */
+            xacc[i] = vmlal_u32(xacc[i], shuffled.val[0], prime);
+    }   }
+
+#elif (XXH_VECTOR == XXH_VSX)
+
+          U64x2* const xacc =       (U64x2*) acc;
+    const U64x2* const xsecret = (const U64x2*) secret;
+    /* constants */
+    U64x2 const v32  = { 32, 32 };
+    U64x2 const v47 = { 47, 47 };
+    U32x4 const prime = { PRIME32_1, PRIME32_1, PRIME32_1, PRIME32_1 };
+    size_t i;
+#if XXH_VSX_BE
+    /* endian swap */
+    U8x16 const vXorSwap  = { 0x07, 0x16, 0x25, 0x34, 0x43, 0x52, 0x61, 0x70,
+                              0x8F, 0x9E, 0xAD, 0xBC, 0xCB, 0xDA, 0xE9, 0xF8 };
+#endif
+    for (i = 0; i < STRIPE_LEN / sizeof(U64x2); i++) {
+        U64x2 const acc_vec  = xacc[i];
+        U64x2 const data_vec = acc_vec ^ (acc_vec >> v47);
+        /* key_vec = xsecret[i]; */
+#if XXH_VSX_BE
+        /* swap bytes words */
+        U64x2 const key_raw  = vec_vsx_ld(0, xsecret + i);
+        U64x2 const data_key = (U64x2)XXH_vec_permxor((U8x16)data_vec, (U8x16)key_raw, vXorSwap);
+#else
+        U64x2 const key_vec  = vec_vsx_ld(0, xsecret + i);
+        U64x2 const data_key = data_vec ^ key_vec;
+#endif
+
+        /* data_key *= PRIME32_1 */
+
+        /* prod_lo = ((U64x2)data_key & 0xFFFFFFFF) * ((U64x2)prime & 0xFFFFFFFF);  */
+        U64x2 const prod_even  = XXH_vec_mule((U32x4)data_key, prime);
+        /* prod_hi = ((U64x2)data_key >> 32) * ((U64x2)prime >> 32);  */
+        U64x2 const prod_odd  = XXH_vec_mulo((U32x4)data_key, prime);
+        xacc[i] = prod_odd + (prod_even << v32);
+    }
+
+#else   /* scalar variant of Scrambler - universal */
+
+    XXH_ALIGN(XXH_ACC_ALIGN) xxh_u64* const xacc = (xxh_u64*) acc;   /* presumed aligned on 32-bytes boundaries, little hint for the auto-vectorizer */
+    const xxh_u8* const xsecret = (const xxh_u8*) secret;   /* no alignment restriction */
+    size_t i;
+    XXH_ASSERT((((size_t)acc) & (XXH_ACC_ALIGN-1)) == 0);
+    for (i=0; i < ACC_NB; i++) {
+        xxh_u64 const key64 = XXH_readLE64(xsecret + 8*i);
+        xxh_u64 acc64 = xacc[i];
+        acc64 ^= acc64 >> 47;
+        acc64 ^= key64;
+        acc64 *= PRIME32_1;
+        xacc[i] = acc64;
+    }
+
+#endif
+}
+
+#define XXH_PREFETCH_DIST 384
+
+/* assumption : nbStripes will not overflow secret size */
+XXH_FORCE_INLINE void
+XXH3p_accumulate(       xxh_u64* XXH_RESTRICT acc,
+                const xxh_u8* XXH_RESTRICT input,
+                const xxh_u8* XXH_RESTRICT secret,
+                      size_t nbStripes,
+                      XXH3p_accWidth_e accWidth)
+{
+    size_t n;
+    for (n = 0; n < nbStripes; n++ ) {
+        const xxh_u8* const in = input + n*STRIPE_LEN;
+        XXH_PREFETCH(in + XXH_PREFETCH_DIST);
+        XXH3p_accumulate_512(acc,
+                            in,
+                            secret + n*XXH_SECRET_CONSUME_RATE,
+                            accWidth);
+    }
+}
+
+/* note : clang auto-vectorizes well in SS2 mode _if_ this function is `static`,
+ *        and doesn't auto-vectorize it at all if it is `FORCE_INLINE`.
+ *        However, it auto-vectorizes better AVX2 if it is `FORCE_INLINE`
+ *        Pretty much every other modes and compilers prefer `FORCE_INLINE`.
+ */
+
+#if defined(__clang__) && (XXH_VECTOR==0) && !defined(__AVX2__) && !defined(__arm__) && !defined(__thumb__)
+static void
+#else
+XXH_FORCE_INLINE void
+#endif
+XXH3p_hashLong_internal_loop( xxh_u64* XXH_RESTRICT acc,
+                      const xxh_u8* XXH_RESTRICT input, size_t len,
+                      const xxh_u8* XXH_RESTRICT secret, size_t secretSize,
+                            XXH3p_accWidth_e accWidth)
+{
+    size_t const nb_rounds = (secretSize - STRIPE_LEN) / XXH_SECRET_CONSUME_RATE;
+    size_t const block_len = STRIPE_LEN * nb_rounds;
+    size_t const nb_blocks = len / block_len;
+
+    size_t n;
+
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN);
+
+    for (n = 0; n < nb_blocks; n++) {
+        XXH3p_accumulate(acc, input + n*block_len, secret, nb_rounds, accWidth);
+        XXH3p_scrambleAcc(acc, secret + secretSize - STRIPE_LEN);
+    }
+
+    /* last partial block */
+    XXH_ASSERT(len > STRIPE_LEN);
+    {   size_t const nbStripes = (len - (block_len * nb_blocks)) / STRIPE_LEN;
+        XXH_ASSERT(nbStripes <= (secretSize / XXH_SECRET_CONSUME_RATE));
+        XXH3p_accumulate(acc, input + nb_blocks*block_len, secret, nbStripes, accWidth);
+
+        /* last stripe */
+        if (len & (STRIPE_LEN - 1)) {
+            const xxh_u8* const p = input + len - STRIPE_LEN;
+#define XXH_SECRET_LASTACC_START 7  /* do not align on 8, so that secret is different from scrambler */
+            XXH3p_accumulate_512(acc, p, secret + secretSize - STRIPE_LEN - XXH_SECRET_LASTACC_START, accWidth);
+    }   }
+}
+
+XXH_FORCE_INLINE xxh_u64
+XXH3p_mix2Accs(const xxh_u64* XXH_RESTRICT acc, const xxh_u8* XXH_RESTRICT secret)
+{
+    return XXH3p_mul128_fold64(
+               acc[0] ^ XXH_readLE64(secret),
+               acc[1] ^ XXH_readLE64(secret+8) );
+}
+
+static XXH64_hash_t
+XXH3p_mergeAccs(const xxh_u64* XXH_RESTRICT acc, const xxh_u8* XXH_RESTRICT secret, xxh_u64 start)
+{
+    xxh_u64 result64 = start;
+
+    result64 += XXH3p_mix2Accs(acc+0, secret +  0);
+    result64 += XXH3p_mix2Accs(acc+2, secret + 16);
+    result64 += XXH3p_mix2Accs(acc+4, secret + 32);
+    result64 += XXH3p_mix2Accs(acc+6, secret + 48);
+
+    return XXH3p_avalanche(result64);
+}
+
+#define XXH3p_INIT_ACC { PRIME32_3, PRIME64_1, PRIME64_2, PRIME64_3, \
+                        PRIME64_4, PRIME32_2, PRIME64_5, PRIME32_1 };
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_hashLong_internal(const xxh_u8* XXH_RESTRICT input, size_t len,
+                       const xxh_u8* XXH_RESTRICT secret, size_t secretSize)
+{
+    XXH_ALIGN(XXH_ACC_ALIGN) xxh_u64 acc[ACC_NB] = XXH3p_INIT_ACC;
+
+    XXH3p_hashLong_internal_loop(acc, input, len, secret, secretSize, XXH3p_acc_64bits);
+
+    /* converge into final hash */
+    XXH_STATIC_ASSERT(sizeof(acc) == 64);
+#define XXH_SECRET_MERGEACCS_START 11  /* do not align on 8, so that secret is different from accumulator */
+    XXH_ASSERT(secretSize >= sizeof(acc) + XXH_SECRET_MERGEACCS_START);
+    return XXH3p_mergeAccs(acc, secret + XXH_SECRET_MERGEACCS_START, (xxh_u64)len * PRIME64_1);
+}
+
+
+XXH_NO_INLINE XXH64_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_64b_defaultSecret(const xxh_u8* XXH_RESTRICT input, size_t len)
+{
+    return XXH3p_hashLong_internal(input, len, kSecret, sizeof(kSecret));
+}
+
+XXH_NO_INLINE XXH64_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_64b_withSecret(const xxh_u8* XXH_RESTRICT input, size_t len,
+                             const xxh_u8* XXH_RESTRICT secret, size_t secretSize)
+{
+    return XXH3p_hashLong_internal(input, len, secret, secretSize);
+}
+
+
+XXH_FORCE_INLINE void XXH_writeLE64(void* dst, xxh_u64 v64)
+{
+    if (!XXH_CPU_LITTLE_ENDIAN) v64 = XXH_swap64(v64);
+    memcpy(dst, &v64, sizeof(v64));
+}
+
+/* XXH3p_initCustomSecret() :
+ * destination `customSecret` is presumed allocated and same size as `kSecret`.
+ */
+XXH_FORCE_INLINE void XXH3p_initCustomSecret(xxh_u8* customSecret, xxh_u64 seed64)
+{
+    int const nbRounds = XXH_SECRET_DEFAULT_SIZE / 16;
+    int i;
+
+    XXH_STATIC_ASSERT((XXH_SECRET_DEFAULT_SIZE & 15) == 0);
+
+    for (i=0; i < nbRounds; i++) {
+        XXH_writeLE64(customSecret + 16*i,     XXH_readLE64(kSecret + 16*i)     + seed64);
+        XXH_writeLE64(customSecret + 16*i + 8, XXH_readLE64(kSecret + 16*i + 8) - seed64);
+    }
+}
+
+
+/* XXH3p_hashLong_64b_withSeed() :
+ * Generate a custom key,
+ * based on alteration of default kSecret with the seed,
+ * and then use this key for long mode hashing.
+ * This operation is decently fast but nonetheless costs a little bit of time.
+ * Try to avoid it whenever possible (typically when seed==0).
+ */
+XXH_NO_INLINE XXH64_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_64b_withSeed(const xxh_u8* input, size_t len, XXH64_hash_t seed)
+{
+    XXH_ALIGN(8) xxh_u8 secret[XXH_SECRET_DEFAULT_SIZE];
+    if (seed==0) return XXH3p_hashLong_64b_defaultSecret(input, len);
+    XXH3p_initCustomSecret(secret, seed);
+    return XXH3p_hashLong_internal(input, len, secret, sizeof(secret));
+}
+
+
+XXH_FORCE_INLINE xxh_u64 XXH3p_mix16B(const xxh_u8* XXH_RESTRICT input,
+                                 const xxh_u8* XXH_RESTRICT secret, xxh_u64 seed64)
+{
+    xxh_u64 const input_lo = XXH_readLE64(input);
+    xxh_u64 const input_hi = XXH_readLE64(input+8);
+    return XXH3p_mul128_fold64(
+               input_lo ^ (XXH_readLE64(secret)   + seed64),
+               input_hi ^ (XXH_readLE64(secret+8) - seed64) );
+}
+
+
+XXH_FORCE_INLINE XXH64_hash_t
+XXH3p_len_17to128_64b(const xxh_u8* XXH_RESTRICT input, size_t len,
+                     const xxh_u8* XXH_RESTRICT secret, size_t secretSize,
+                     XXH64_hash_t seed)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN); (void)secretSize;
+    XXH_ASSERT(16 < len && len <= 128);
+
+    {   xxh_u64 acc = len * PRIME64_1;
+        if (len > 32) {
+            if (len > 64) {
+                if (len > 96) {
+                    acc += XXH3p_mix16B(input+48, secret+96, seed);
+                    acc += XXH3p_mix16B(input+len-64, secret+112, seed);
+                }
+                acc += XXH3p_mix16B(input+32, secret+64, seed);
+                acc += XXH3p_mix16B(input+len-48, secret+80, seed);
+            }
+            acc += XXH3p_mix16B(input+16, secret+32, seed);
+            acc += XXH3p_mix16B(input+len-32, secret+48, seed);
+        }
+        acc += XXH3p_mix16B(input+0, secret+0, seed);
+        acc += XXH3p_mix16B(input+len-16, secret+16, seed);
+
+        return XXH3p_avalanche(acc);
+    }
+}
+
+#define XXH3p_MIDSIZE_MAX 240
+
+XXH_NO_INLINE XXH64_hash_t
+XXH3p_len_129to240_64b(const xxh_u8* XXH_RESTRICT input, size_t len,
+                      const xxh_u8* XXH_RESTRICT secret, size_t secretSize,
+                      XXH64_hash_t seed)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN); (void)secretSize;
+    XXH_ASSERT(128 < len && len <= XXH3p_MIDSIZE_MAX);
+
+    #define XXH3p_MIDSIZE_STARTOFFSET 3
+    #define XXH3p_MIDSIZE_LASTOFFSET  17
+
+    {   xxh_u64 acc = len * PRIME64_1;
+        int const nbRounds = (int)len / 16;
+        int i;
+        for (i=0; i<8; i++) {
+            acc += XXH3p_mix16B(input+(16*i), secret+(16*i), seed);
+        }
+        acc = XXH3p_avalanche(acc);
+        XXH_ASSERT(nbRounds >= 8);
+        for (i=8 ; i < nbRounds; i++) {
+            acc += XXH3p_mix16B(input+(16*i), secret+(16*(i-8)) + XXH3p_MIDSIZE_STARTOFFSET, seed);
+        }
+        /* last bytes */
+        acc += XXH3p_mix16B(input + len - 16, secret + XXH3p_SECRET_SIZE_MIN - XXH3p_MIDSIZE_LASTOFFSET, seed);
+        return XXH3p_avalanche(acc);
+    }
+}
+
+/* ===   Public entry point   === */
+
+XXH_PUBLIC_API XXH64_hash_t XXH3p_64bits(const void* input, size_t len)
+{
+    if (len <= 16) return XXH3p_len_0to16_64b((const xxh_u8*)input, len, kSecret, 0);
+    if (len <= 128) return XXH3p_len_17to128_64b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), 0);
+    if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_64b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), 0);
+    return XXH3p_hashLong_64b_defaultSecret((const xxh_u8*)input, len);
+}
+
+XXH_PUBLIC_API XXH64_hash_t
+XXH3p_64bits_withSecret(const void* input, size_t len, const void* secret, size_t secretSize)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN);
+    /* if an action must be taken should `secret` conditions not be respected,
+     * it should be done here.
+     * For now, it's a contract pre-condition.
+     * Adding a check and a branch here would cost performance at every hash */
+     if (len <= 16) return XXH3p_len_0to16_64b((const xxh_u8*)input, len, (const xxh_u8*)secret, 0);
+     if (len <= 128) return XXH3p_len_17to128_64b((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize, 0);
+     if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_64b((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize, 0);
+     return XXH3p_hashLong_64b_withSecret((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize);
+}
+
+XXH_PUBLIC_API XXH64_hash_t
+XXH3p_64bits_withSeed(const void* input, size_t len, XXH64_hash_t seed)
+{
+    if (len <= 16) return XXH3p_len_0to16_64b((const xxh_u8*)input, len, kSecret, seed);
+    if (len <= 128) return XXH3p_len_17to128_64b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), seed);
+    if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_64b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), seed);
+    return XXH3p_hashLong_64b_withSeed((const xxh_u8*)input, len, seed);
+}
+
+/* ===   XXH3 streaming   === */
+
+XXH_PUBLIC_API XXH3p_state_t* XXH3p_createState(void)
+{
+    return (XXH3p_state_t*)XXH_malloc(sizeof(XXH3p_state_t));
+}
+
+XXH_PUBLIC_API XXH_errorcode XXH3p_freeState(XXH3p_state_t* statePtr)
+{
+    XXH_free(statePtr);
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API void
+XXH3p_copyState(XXH3p_state_t* dst_state, const XXH3p_state_t* src_state)
+{
+    memcpy(dst_state, src_state, sizeof(*dst_state));
+}
+
+static void
+XXH3p_64bits_reset_internal(XXH3p_state_t* statePtr,
+                           XXH64_hash_t seed,
+                           const xxh_u8* secret, size_t secretSize)
+{
+    XXH_ASSERT(statePtr != NULL);
+    memset(statePtr, 0, sizeof(*statePtr));
+    statePtr->acc[0] = PRIME32_3;
+    statePtr->acc[1] = PRIME64_1;
+    statePtr->acc[2] = PRIME64_2;
+    statePtr->acc[3] = PRIME64_3;
+    statePtr->acc[4] = PRIME64_4;
+    statePtr->acc[5] = PRIME32_2;
+    statePtr->acc[6] = PRIME64_5;
+    statePtr->acc[7] = PRIME32_1;
+    statePtr->seed = seed;
+    XXH_ASSERT(secret != NULL);
+    statePtr->secret = secret;
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN);
+    statePtr->secretLimit = (XXH32_hash_t)(secretSize - STRIPE_LEN);
+    statePtr->nbStripesPerBlock = statePtr->secretLimit / XXH_SECRET_CONSUME_RATE;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_64bits_reset(XXH3p_state_t* statePtr)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_64bits_reset_internal(statePtr, 0, kSecret, XXH_SECRET_DEFAULT_SIZE);
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_64bits_reset_withSecret(XXH3p_state_t* statePtr, const void* secret, size_t secretSize)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_64bits_reset_internal(statePtr, 0, (const xxh_u8*)secret, secretSize);
+    if (secret == NULL) return XXH_ERROR;
+    if (secretSize < XXH3p_SECRET_SIZE_MIN) return XXH_ERROR;
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_64bits_reset_withSeed(XXH3p_state_t* statePtr, XXH64_hash_t seed)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_64bits_reset_internal(statePtr, seed, kSecret, XXH_SECRET_DEFAULT_SIZE);
+    XXH3p_initCustomSecret(statePtr->customSecret, seed);
+    statePtr->secret = statePtr->customSecret;
+    return XXH_OK;
+}
+
+XXH_FORCE_INLINE void
+XXH3p_consumeStripes( xxh_u64* acc,
+                    XXH32_hash_t* nbStripesSoFarPtr, XXH32_hash_t nbStripesPerBlock,
+                    const xxh_u8* input, size_t totalStripes,
+                    const xxh_u8* secret, size_t secretLimit,
+                    XXH3p_accWidth_e accWidth)
+{
+    XXH_ASSERT(*nbStripesSoFarPtr < nbStripesPerBlock);
+    if (nbStripesPerBlock - *nbStripesSoFarPtr <= totalStripes) {
+        /* need a scrambling operation */
+        size_t const nbStripes = nbStripesPerBlock - *nbStripesSoFarPtr;
+        XXH3p_accumulate(acc, input, secret + nbStripesSoFarPtr[0] * XXH_SECRET_CONSUME_RATE, nbStripes, accWidth);
+        XXH3p_scrambleAcc(acc, secret + secretLimit);
+        XXH3p_accumulate(acc, input + nbStripes * STRIPE_LEN, secret, totalStripes - nbStripes, accWidth);
+        *nbStripesSoFarPtr = (XXH32_hash_t)(totalStripes - nbStripes);
+    } else {
+        XXH3p_accumulate(acc, input, secret + nbStripesSoFarPtr[0] * XXH_SECRET_CONSUME_RATE, totalStripes, accWidth);
+        *nbStripesSoFarPtr += (XXH32_hash_t)totalStripes;
+    }
+}
+
+XXH_FORCE_INLINE XXH_errorcode
+XXH3p_update(XXH3p_state_t* state, const xxh_u8* input, size_t len, XXH3p_accWidth_e accWidth)
+{
+    if (input==NULL)
+#if defined(XXH_ACCEPT_NULL_INPUT_POINTER) && (XXH_ACCEPT_NULL_INPUT_POINTER>=1)
+        return XXH_OK;
+#else
+        return XXH_ERROR;
+#endif
+
+    {   const xxh_u8* const bEnd = input + len;
+
+        state->totalLen += len;
+
+        if (state->bufferedSize + len <= XXH3p_INTERNALBUFFER_SIZE) {  /* fill in tmp buffer */
+            XXH_memcpy(state->buffer + state->bufferedSize, input, len);
+            state->bufferedSize += (XXH32_hash_t)len;
+            return XXH_OK;
+        }
+        /* input now > XXH3p_INTERNALBUFFER_SIZE */
+
+        #define XXH3p_INTERNALBUFFER_STRIPES (XXH3p_INTERNALBUFFER_SIZE / STRIPE_LEN)
+        XXH_STATIC_ASSERT(XXH3p_INTERNALBUFFER_SIZE % STRIPE_LEN == 0);   /* clean multiple */
+
+        if (state->bufferedSize) {   /* some input within internal buffer: fill then consume it */
+            size_t const loadSize = XXH3p_INTERNALBUFFER_SIZE - state->bufferedSize;
+            XXH_memcpy(state->buffer + state->bufferedSize, input, loadSize);
+            input += loadSize;
+            XXH3p_consumeStripes(state->acc,
+                               &state->nbStripesSoFar, state->nbStripesPerBlock,
+                                state->buffer, XXH3p_INTERNALBUFFER_STRIPES,
+                                state->secret, state->secretLimit,
+                                accWidth);
+            state->bufferedSize = 0;
+        }
+
+        /* consume input by full buffer quantities */
+        if (input+XXH3p_INTERNALBUFFER_SIZE <= bEnd) {
+            const xxh_u8* const limit = bEnd - XXH3p_INTERNALBUFFER_SIZE;
+            do {
+                XXH3p_consumeStripes(state->acc,
+                                   &state->nbStripesSoFar, state->nbStripesPerBlock,
+                                    input, XXH3p_INTERNALBUFFER_STRIPES,
+                                    state->secret, state->secretLimit,
+                                    accWidth);
+                input += XXH3p_INTERNALBUFFER_SIZE;
+            } while (input<=limit);
+        }
+
+        if (input < bEnd) { /* some remaining input input : buffer it */
+            XXH_memcpy(state->buffer, input, (size_t)(bEnd-input));
+            state->bufferedSize = (XXH32_hash_t)(bEnd-input);
+        }
+    }
+
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_64bits_update(XXH3p_state_t* state, const void* input, size_t len)
+{
+    return XXH3p_update(state, (const xxh_u8*)input, len, XXH3p_acc_64bits);
+}
+
+
+XXH_FORCE_INLINE void
+XXH3p_digest_long (XXH64_hash_t* acc, const XXH3p_state_t* state, XXH3p_accWidth_e accWidth)
+{
+    memcpy(acc, state->acc, sizeof(state->acc));  /* digest locally, state remains unaltered, and can continue ingesting more input afterwards */
+    if (state->bufferedSize >= STRIPE_LEN) {
+        size_t const totalNbStripes = state->bufferedSize / STRIPE_LEN;
+        XXH32_hash_t nbStripesSoFar = state->nbStripesSoFar;
+        XXH3p_consumeStripes(acc,
+                           &nbStripesSoFar, state->nbStripesPerBlock,
+                            state->buffer, totalNbStripes,
+                            state->secret, state->secretLimit,
+                            accWidth);
+        if (state->bufferedSize % STRIPE_LEN) {  /* one last partial stripe */
+            XXH3p_accumulate_512(acc,
+                                state->buffer + state->bufferedSize - STRIPE_LEN,
+                                state->secret + state->secretLimit - XXH_SECRET_LASTACC_START,
+                                accWidth);
+        }
+    } else {  /* bufferedSize < STRIPE_LEN */
+        if (state->bufferedSize) { /* one last stripe */
+            xxh_u8 lastStripe[STRIPE_LEN];
+            size_t const catchupSize = STRIPE_LEN - state->bufferedSize;
+            memcpy(lastStripe, state->buffer + sizeof(state->buffer) - catchupSize, catchupSize);
+            memcpy(lastStripe + catchupSize, state->buffer, state->bufferedSize);
+            XXH3p_accumulate_512(acc,
+                                lastStripe,
+                                state->secret + state->secretLimit - XXH_SECRET_LASTACC_START,
+                                accWidth);
+    }   }
+}
+
+XXH_PUBLIC_API XXH64_hash_t XXH3p_64bits_digest (const XXH3p_state_t* state)
+{
+    if (state->totalLen > XXH3p_MIDSIZE_MAX) {
+        XXH_ALIGN(XXH_ACC_ALIGN) XXH64_hash_t acc[ACC_NB];
+        XXH3p_digest_long(acc, state, XXH3p_acc_64bits);
+        return XXH3p_mergeAccs(acc, state->secret + XXH_SECRET_MERGEACCS_START, (xxh_u64)state->totalLen * PRIME64_1);
+    }
+    /* len <= XXH3p_MIDSIZE_MAX : short code */
+    if (state->seed)
+        return XXH3p_64bits_withSeed(state->buffer, (size_t)state->totalLen, state->seed);
+    return XXH3p_64bits_withSecret(state->buffer, (size_t)(state->totalLen), state->secret, state->secretLimit + STRIPE_LEN);
+}
+
+/* ==========================================
+ * XXH3 128 bits (=> XXH128)
+ * ========================================== */
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_len_1to3_128b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(1 <= len && len <= 3);
+    XXH_ASSERT(secret != NULL);
+    {   xxh_u8 const c1 = input[0];
+        xxh_u8 const c2 = input[len >> 1];
+        xxh_u8 const c3 = input[len - 1];
+        xxh_u32  const combinedl = ((xxh_u32)c1) + (((xxh_u32)c2) << 8) + (((xxh_u32)c3) << 16) + (((xxh_u32)len) << 24);
+        xxh_u32  const combinedh = XXH_swap32(combinedl);
+        xxh_u64  const keyed_lo = (xxh_u64)combinedl ^ (XXH_readLE32(secret)   + seed);
+        xxh_u64  const keyed_hi = (xxh_u64)combinedh ^ (XXH_readLE32(secret+4) - seed);
+        xxh_u64  const mixedl = keyed_lo * PRIME64_1;
+        xxh_u64  const mixedh = keyed_hi * PRIME64_5;
+        XXH128_hash_t const h128 = { XXH3p_avalanche(mixedl) /*low64*/, XXH3p_avalanche(mixedh) /*high64*/ };
+        return h128;
+    }
+}
+
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_len_4to8_128b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(secret != NULL);
+    XXH_ASSERT(4 <= len && len <= 8);
+    {   xxh_u32 const input_lo = XXH_readLE32(input);
+        xxh_u32 const input_hi = XXH_readLE32(input + len - 4);
+        xxh_u64 const input_64_lo = input_lo + ((xxh_u64)input_hi << 32);
+        xxh_u64 const input_64_hi = XXH_swap64(input_64_lo);
+        xxh_u64 const keyed_lo = input_64_lo ^ (XXH_readLE64(secret) + seed);
+        xxh_u64 const keyed_hi = input_64_hi ^ (XXH_readLE64(secret + 8) - seed);
+        xxh_u64 const mix64l1 = len + ((keyed_lo ^ (keyed_lo >> 51)) * PRIME32_1);
+        xxh_u64 const mix64l2 = (mix64l1 ^ (mix64l1 >> 47)) * PRIME64_2;
+        xxh_u64 const mix64h1 = ((keyed_hi ^ (keyed_hi >> 47)) * PRIME64_1) - len;
+        xxh_u64 const mix64h2 = (mix64h1 ^ (mix64h1 >> 43)) * PRIME64_4;
+        {   XXH128_hash_t const h128 = { XXH3p_avalanche(mix64l2) /*low64*/, XXH3p_avalanche(mix64h2) /*high64*/ };
+            return h128;
+    }   }
+}
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_len_9to16_128b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(input != NULL);
+    XXH_ASSERT(secret != NULL);
+    XXH_ASSERT(9 <= len && len <= 16);
+    {   xxh_u64 const input_lo = XXH_readLE64(input) ^ (XXH_readLE64(secret) + seed);
+        xxh_u64 const input_hi = XXH_readLE64(input + len - 8) ^ (XXH_readLE64(secret+8) - seed);
+        XXH128_hash_t m128 = XXH_mult64to128(input_lo ^ input_hi, PRIME64_1);
+        xxh_u64 const lenContrib = XXH_mult32to64(len, PRIME32_5);
+        m128.low64 += lenContrib;
+        m128.high64 += input_hi * PRIME64_1;
+        m128.low64  ^= (m128.high64 >> 32);
+        {   XXH128_hash_t h128 = XXH_mult64to128(m128.low64, PRIME64_2);
+            h128.high64 += m128.high64 * PRIME64_2;
+            h128.low64   = XXH3p_avalanche(h128.low64);
+            h128.high64  = XXH3p_avalanche(h128.high64);
+            return h128;
+    }   }
+}
+
+/* Assumption : `secret` size is >= 16
+ * Note : it should be >= XXH3p_SECRET_SIZE_MIN anyway */
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_len_0to16_128b(const xxh_u8* input, size_t len, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    XXH_ASSERT(len <= 16);
+    {   if (len > 8) return XXH3p_len_9to16_128b(input, len, secret, seed);
+        if (len >= 4) return XXH3p_len_4to8_128b(input, len, secret, seed);
+        if (len) return XXH3p_len_1to3_128b(input, len, secret, seed);
+        {   XXH128_hash_t const h128 = { 0, 0 };
+            return h128;
+    }   }
+}
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_hashLong_128b_internal(const xxh_u8* XXH_RESTRICT input, size_t len,
+                            const xxh_u8* XXH_RESTRICT secret, size_t secretSize)
+{
+    XXH_ALIGN(XXH_ACC_ALIGN) xxh_u64 acc[ACC_NB] = XXH3p_INIT_ACC;
+
+    XXH3p_hashLong_internal_loop(acc, input, len, secret, secretSize, XXH3p_acc_128bits);
+
+    /* converge into final hash */
+    XXH_STATIC_ASSERT(sizeof(acc) == 64);
+    XXH_ASSERT(secretSize >= sizeof(acc) + XXH_SECRET_MERGEACCS_START);
+    {   xxh_u64 const low64 = XXH3p_mergeAccs(acc, secret + XXH_SECRET_MERGEACCS_START, (xxh_u64)len * PRIME64_1);
+        xxh_u64 const high64 = XXH3p_mergeAccs(acc, secret + secretSize - sizeof(acc) - XXH_SECRET_MERGEACCS_START, ~((xxh_u64)len * PRIME64_2));
+        XXH128_hash_t const h128 = { low64, high64 };
+        return h128;
+    }
+}
+
+XXH_NO_INLINE XXH128_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_128b_defaultSecret(const xxh_u8* input, size_t len)
+{
+    return XXH3p_hashLong_128b_internal(input, len, kSecret, sizeof(kSecret));
+}
+
+XXH_NO_INLINE XXH128_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_128b_withSecret(const xxh_u8* input, size_t len,
+                              const xxh_u8* secret, size_t secretSize)
+{
+    return XXH3p_hashLong_128b_internal(input, len, secret, secretSize);
+}
+
+XXH_NO_INLINE XXH128_hash_t    /* It's important for performance that XXH3p_hashLong is not inlined. Not sure why (uop cache maybe ?), but difference is large and easily measurable */
+XXH3p_hashLong_128b_withSeed(const xxh_u8* input, size_t len, XXH64_hash_t seed)
+{
+    XXH_ALIGN(8) xxh_u8 secret[XXH_SECRET_DEFAULT_SIZE];
+    if (seed == 0) return XXH3p_hashLong_128b_defaultSecret(input, len);
+    XXH3p_initCustomSecret(secret, seed);
+    return XXH3p_hashLong_128b_internal(input, len, secret, sizeof(secret));
+}
+
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH128_mix32B(XXH128_hash_t acc, const xxh_u8* input_1, const xxh_u8* input_2, const xxh_u8* secret, XXH64_hash_t seed)
+{
+    acc.low64  += XXH3p_mix16B (input_1, secret+0, seed);
+    acc.low64  ^= XXH_readLE64(input_2) + XXH_readLE64(input_2 + 8);
+    acc.high64 += XXH3p_mix16B (input_2, secret+16, seed);
+    acc.high64 ^= XXH_readLE64(input_1) + XXH_readLE64(input_1 + 8);
+    return acc;
+}
+
+XXH_NO_INLINE XXH128_hash_t
+XXH3p_len_129to240_128b(const xxh_u8* XXH_RESTRICT input, size_t len,
+                       const xxh_u8* XXH_RESTRICT secret, size_t secretSize,
+                       XXH64_hash_t seed)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN); (void)secretSize;
+    XXH_ASSERT(128 < len && len <= XXH3p_MIDSIZE_MAX);
+
+    {   XXH128_hash_t acc;
+        int const nbRounds = (int)len / 32;
+        int i;
+        acc.low64 = len * PRIME64_1;
+        acc.high64 = 0;
+        for (i=0; i<4; i++) {
+            acc = XXH128_mix32B(acc, input+(32*i), input+(32*i)+16, secret+(32*i), seed);
+        }
+        acc.low64 = XXH3p_avalanche(acc.low64);
+        acc.high64 = XXH3p_avalanche(acc.high64);
+        XXH_ASSERT(nbRounds >= 4);
+        for (i=4 ; i < nbRounds; i++) {
+            acc = XXH128_mix32B(acc, input+(32*i), input+(32*i)+16, secret+XXH3p_MIDSIZE_STARTOFFSET+(32*(i-4)), seed);
+        }
+        /* last bytes */
+        acc = XXH128_mix32B(acc, input + len - 16, input + len - 32, secret + XXH3p_SECRET_SIZE_MIN - XXH3p_MIDSIZE_LASTOFFSET - 16, 0ULL - seed);
+
+        {   xxh_u64 const low64 = acc.low64 + acc.high64;
+            xxh_u64 const high64 = (acc.low64 * PRIME64_1) + (acc.high64 * PRIME64_4) + ((len - seed) * PRIME64_2);
+            XXH128_hash_t const h128 = { XXH3p_avalanche(low64), (XXH64_hash_t)0 - XXH3p_avalanche(high64) };
+            return h128;
+        }
+    }
+}
+
+
+XXH_FORCE_INLINE XXH128_hash_t
+XXH3p_len_17to128_128b(const xxh_u8* XXH_RESTRICT input, size_t len,
+                      const xxh_u8* XXH_RESTRICT secret, size_t secretSize,
+                      XXH64_hash_t seed)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN); (void)secretSize;
+    XXH_ASSERT(16 < len && len <= 128);
+
+    {   XXH128_hash_t acc;
+        acc.low64 = len * PRIME64_1;
+        acc.high64 = 0;
+        if (len > 32) {
+            if (len > 64) {
+                if (len > 96) {
+                    acc = XXH128_mix32B(acc, input+48, input+len-64, secret+96, seed);
+                }
+                acc = XXH128_mix32B(acc, input+32, input+len-48, secret+64, seed);
+            }
+            acc = XXH128_mix32B(acc, input+16, input+len-32, secret+32, seed);
+        }
+        acc = XXH128_mix32B(acc, input, input+len-16, secret, seed);
+        {   xxh_u64 const low64 = acc.low64 + acc.high64;
+            xxh_u64 const high64 = (acc.low64 * PRIME64_1) + (acc.high64 * PRIME64_4) + ((len - seed) * PRIME64_2);
+            XXH128_hash_t const h128 = { XXH3p_avalanche(low64), (XXH64_hash_t)0 - XXH3p_avalanche(high64) };
+            return h128;
+        }
+    }
+}
+
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits(const void* input, size_t len)
+{
+    if (len <= 16) return XXH3p_len_0to16_128b((const xxh_u8*)input, len, kSecret, 0);
+    if (len <= 128) return XXH3p_len_17to128_128b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), 0);
+    if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_128b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), 0);
+    return XXH3p_hashLong_128b_defaultSecret((const xxh_u8*)input, len);
+}
+
+XXH_PUBLIC_API XXH128_hash_t
+XXH3p_128bits_withSecret(const void* input, size_t len, const void* secret, size_t secretSize)
+{
+    XXH_ASSERT(secretSize >= XXH3p_SECRET_SIZE_MIN);
+    /* if an action must be taken should `secret` conditions not be respected,
+     * it should be done here.
+     * For now, it's a contract pre-condition.
+     * Adding a check and a branch here would cost performance at every hash */
+     if (len <= 16) return XXH3p_len_0to16_128b((const xxh_u8*)input, len, (const xxh_u8*)secret, 0);
+     if (len <= 128) return XXH3p_len_17to128_128b((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize, 0);
+     if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_128b((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize, 0);
+     return XXH3p_hashLong_128b_withSecret((const xxh_u8*)input, len, (const xxh_u8*)secret, secretSize);
+}
+
+XXH_PUBLIC_API XXH128_hash_t
+XXH3p_128bits_withSeed(const void* input, size_t len, XXH64_hash_t seed)
+{
+    if (len <= 16) return XXH3p_len_0to16_128b((const xxh_u8*)input, len, kSecret, seed);
+    if (len <= 128) return XXH3p_len_17to128_128b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), seed);
+    if (len <= XXH3p_MIDSIZE_MAX) return XXH3p_len_129to240_128b((const xxh_u8*)input, len, kSecret, sizeof(kSecret), seed);
+    return XXH3p_hashLong_128b_withSeed((const xxh_u8*)input, len, seed);
+}
+
+XXH_PUBLIC_API XXH128_hash_t
+XXH128(const void* input, size_t len, XXH64_hash_t seed)
+{
+    return XXH3p_128bits_withSeed(input, len, seed);
+}
+
+
+/* ===   XXH3 128-bit streaming   === */
+
+/* all the functions are actually the same as for 64-bit streaming variant,
+   just the reset one is different (different initial acc values for 0,5,6,7),
+   and near the end of the digest function */
+
+static void
+XXH3p_128bits_reset_internal(XXH3p_state_t* statePtr,
+                           XXH64_hash_t seed,
+                           const xxh_u8* secret, size_t secretSize)
+{
+    XXH3p_64bits_reset_internal(statePtr, seed, secret, secretSize);
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_128bits_reset(XXH3p_state_t* statePtr)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_128bits_reset_internal(statePtr, 0, kSecret, XXH_SECRET_DEFAULT_SIZE);
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_128bits_reset_withSecret(XXH3p_state_t* statePtr, const void* secret, size_t secretSize)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_128bits_reset_internal(statePtr, 0, (const xxh_u8*)secret, secretSize);
+    if (secret == NULL) return XXH_ERROR;
+    if (secretSize < XXH3p_SECRET_SIZE_MIN) return XXH_ERROR;
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_128bits_reset_withSeed(XXH3p_state_t* statePtr, XXH64_hash_t seed)
+{
+    if (statePtr == NULL) return XXH_ERROR;
+    XXH3p_128bits_reset_internal(statePtr, seed, kSecret, XXH_SECRET_DEFAULT_SIZE);
+    XXH3p_initCustomSecret(statePtr->customSecret, seed);
+    statePtr->secret = statePtr->customSecret;
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH3p_128bits_update(XXH3p_state_t* state, const void* input, size_t len)
+{
+    return XXH3p_update(state, (const xxh_u8*)input, len, XXH3p_acc_128bits);
+}
+
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits_digest (const XXH3p_state_t* state)
+{
+    if (state->totalLen > XXH3p_MIDSIZE_MAX) {
+        XXH_ALIGN(XXH_ACC_ALIGN) XXH64_hash_t acc[ACC_NB];
+        XXH3p_digest_long(acc, state, XXH3p_acc_128bits);
+        XXH_ASSERT(state->secretLimit + STRIPE_LEN >= sizeof(acc) + XXH_SECRET_MERGEACCS_START);
+        {   xxh_u64 const low64 = XXH3p_mergeAccs(acc, state->secret + XXH_SECRET_MERGEACCS_START, (xxh_u64)state->totalLen * PRIME64_1);
+            xxh_u64 const high64 = XXH3p_mergeAccs(acc, state->secret + state->secretLimit + STRIPE_LEN - sizeof(acc) - XXH_SECRET_MERGEACCS_START, ~((xxh_u64)state->totalLen * PRIME64_2));
+            XXH128_hash_t const h128 = { low64, high64 };
+            return h128;
+        }
+    }
+    /* len <= XXH3p_MIDSIZE_MAX : short code */
+    if (state->seed)
+        return XXH3p_128bits_withSeed(state->buffer, (size_t)state->totalLen, state->seed);
+    return XXH3p_128bits_withSecret(state->buffer, (size_t)(state->totalLen), state->secret, state->secretLimit + STRIPE_LEN);
+}
+
+/* 128-bit utility functions */
+
+#include <string.h>   /* memcmp */
+
+/* return : 1 is equal, 0 if different */
+XXH_PUBLIC_API int XXH128_isEqual(XXH128_hash_t h1, XXH128_hash_t h2)
+{
+    /* note : XXH128_hash_t is compact, it has no padding byte */
+    return !(memcmp(&h1, &h2, sizeof(h1)));
+}
+
+/* This prototype is compatible with stdlib's qsort().
+ * return : >0 if *h128_1  > *h128_2
+ *          <0 if *h128_1  < *h128_2
+ *          =0 if *h128_1 == *h128_2  */
+XXH_PUBLIC_API int XXH128_cmp(const void* h128_1, const void* h128_2)
+{
+    XXH128_hash_t const h1 = *(const XXH128_hash_t*)h128_1;
+    XXH128_hash_t const h2 = *(const XXH128_hash_t*)h128_2;
+    int const hcmp = (h1.high64 > h2.high64) - (h2.high64 > h1.high64);
+    /* note : bets that, in most cases, hash values are different */
+    if (hcmp) return hcmp;
+    return (h1.low64 > h2.low64) - (h2.low64 > h1.low64);
+}
+
+
+/*======   Canonical representation   ======*/
+XXH_PUBLIC_API void
+XXH128_canonicalFromHash(XXH128_canonical_t* dst, XXH128_hash_t hash)
+{
+    XXH_STATIC_ASSERT(sizeof(XXH128_canonical_t) == sizeof(XXH128_hash_t));
+    if (XXH_CPU_LITTLE_ENDIAN) {
+        hash.high64 = XXH_swap64(hash.high64);
+        hash.low64  = XXH_swap64(hash.low64);
+    }
+    memcpy(dst, &hash.high64, sizeof(hash.high64));
+    memcpy((char*)dst + sizeof(hash.high64), &hash.low64, sizeof(hash.low64));
+}
+
+XXH_PUBLIC_API XXH128_hash_t
+XXH128_hashFromCanonical(const XXH128_canonical_t* src)
+{
+    XXH128_hash_t h;
+    h.high64 = XXH_readBE64(src);
+    h.low64  = XXH_readBE64(src->digest + 8);
+    return h;
+}
+
+
+
+#endif  /* XXH3p_H */
diff --git a/src/rocksdb/util/xxhash.cc b/src/rocksdb/util/xxhash.cc
new file mode 100644
index 000000000..6620ae8b6
--- /dev/null
+++ b/src/rocksdb/util/xxhash.cc
@@ -0,0 +1,1160 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+/*
+*  xxHash - Fast Hash algorithm
+*  Copyright (C) 2012-2016, Yann Collet
+*
+*  BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+*
+*  Redistribution and use in source and binary forms, with or without
+*  modification, are permitted provided that the following conditions are
+*  met:
+*
+*  * Redistributions of source code must retain the above copyright
+*  notice, this list of conditions and the following disclaimer.
+*  * Redistributions in binary form must reproduce the above
+*  copyright notice, this list of conditions and the following disclaimer
+*  in the documentation and/or other materials provided with the
+*  distribution.
+*
+*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+*  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+*  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+*  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+*  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+*  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+*  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+*  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+*  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+*  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+*  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*
+*  You can contact the author at :
+*  - xxHash homepage: http://www.xxhash.com
+*  - xxHash source repository : https://github.com/Cyan4973/xxHash
+*/
+
+
+/* since xxhash.c can be included (via XXH_INLINE_ALL),
+ * it's good practice to protect it with guard
+ * in case of multiples inclusions */
+#ifndef XXHASH_C_01393879
+#define XXHASH_C_01393879
+
+/* *************************************
+*  Tuning parameters
+***************************************/
+/*!XXH_FORCE_MEMORY_ACCESS :
+ * By default, access to unaligned memory is controlled by `memcpy()`, which is safe and portable.
+ * Unfortunately, on some target/compiler combinations, the generated assembly is sub-optimal.
+ * The below switch allow to select different access method for improved performance.
+ * Method 0 (default) : use `memcpy()`. Safe and portable.
+ * Method 1 : `__packed` statement. It depends on compiler extension (ie, not portable).
+ *            This method is safe if your compiler supports it, and *generally* as fast or faster than `memcpy`.
+ * Method 2 : direct access. This method doesn't depend on compiler but violate C standard.
+ *            It can generate buggy code on targets which do not support unaligned memory accesses.
+ *            But in some circumstances, it's the only known way to get the most performance (ie GCC + ARMv6)
+ * See http://stackoverflow.com/a/32095106/646947 for details.
+ * Prefer these methods in priority order (0 > 1 > 2)
+ */
+#ifndef XXH_FORCE_MEMORY_ACCESS   /* can be defined externally, on command line for example */
+#  if !defined(__clang__) && defined(__GNUC__) && defined(__ARM_FEATURE_UNALIGNED) && defined(__ARM_ARCH) && (__ARM_ARCH == 6)
+#    define XXH_FORCE_MEMORY_ACCESS 2
+#  elif !defined(__clang__) && ((defined(__INTEL_COMPILER) && !defined(_WIN32)) || \
+  (defined(__GNUC__) && (defined(__ARM_ARCH) && __ARM_ARCH >= 7)))
+#    define XXH_FORCE_MEMORY_ACCESS 1
+#  endif
+#endif
+
+/*!XXH_ACCEPT_NULL_INPUT_POINTER :
+ * If input pointer is NULL, xxHash default behavior is to dereference it, triggering a segfault.
+ * When this macro is enabled, xxHash actively checks input for null pointer.
+ * It it is, result for null input pointers is the same as a null-length input.
+ */
+#ifndef XXH_ACCEPT_NULL_INPUT_POINTER   /* can be defined externally */
+#  define XXH_ACCEPT_NULL_INPUT_POINTER 0
+#endif
+
+/*!XXH_FORCE_ALIGN_CHECK :
+ * This is a minor performance trick, only useful with lots of very small keys.
+ * It means : check for aligned/unaligned input.
+ * The check costs one initial branch per hash;
+ * set it to 0 when the input is guaranteed to be aligned,
+ * or when alignment doesn't matter for performance.
+ */
+#ifndef XXH_FORCE_ALIGN_CHECK /* can be defined externally */
+#  if defined(__i386) || defined(_M_IX86) || defined(__x86_64__) || defined(_M_X64)
+#    define XXH_FORCE_ALIGN_CHECK 0
+#  else
+#    define XXH_FORCE_ALIGN_CHECK 1
+#  endif
+#endif
+
+/*!XXH_REROLL:
+ * Whether to reroll XXH32_finalize, and XXH64_finalize,
+ * instead of using an unrolled jump table/if statement loop.
+ *
+ * This is automatically defined on -Os/-Oz on GCC and Clang. */
+#ifndef XXH_REROLL
+#  if defined(__OPTIMIZE_SIZE__)
+#    define XXH_REROLL 1
+#  else
+#    define XXH_REROLL 0
+#  endif
+#endif
+
+/* *************************************
+*  Includes & Memory related functions
+***************************************/
+/*! Modify the local functions below should you wish to use some other memory routines
+*   for malloc(), free() */
+#include <stdlib.h>
+static void* XXH_malloc(size_t s) { return malloc(s); }
+static void  XXH_free  (void* p)  { free(p); }
+/*! and for memcpy() */
+#include <string.h>
+static void* XXH_memcpy(void* dest, const void* src, size_t size) { return memcpy(dest,src,size); }
+
+#include <limits.h>   /* ULLONG_MAX */
+
+#ifndef XXH_STATIC_LINKING_ONLY
+#define XXH_STATIC_LINKING_ONLY
+#endif
+
+#include "xxhash.h"
+
+/* BEGIN RocksDB customizations */
+#include "util/util.h" /* for FALLTHROUGH_INTENDED, inserted as appropriate */
+/* END RocksDB customizations */
+
+/* *************************************
+*  Compiler Specific Options
+***************************************/
+#ifdef _MSC_VER    /* Visual Studio */
+#  pragma warning(disable : 4127)      /* disable: C4127: conditional expression is constant */
+#  define XXH_FORCE_INLINE static __forceinline
+#  define XXH_NO_INLINE static __declspec(noinline)
+#else
+#  if defined (__cplusplus) || defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L   /* C99 */
+#    ifdef __GNUC__
+#      define XXH_FORCE_INLINE static inline __attribute__((always_inline))
+#      define XXH_NO_INLINE static __attribute__((noinline))
+#    else
+#      define XXH_FORCE_INLINE static inline
+#      define XXH_NO_INLINE static
+#    endif
+#  else
+#    define XXH_FORCE_INLINE static
+#    define XXH_NO_INLINE static
+#  endif /* __STDC_VERSION__ */
+#endif
+
+
+
+/* *************************************
+*  Debug
+***************************************/
+/* DEBUGLEVEL is expected to be defined externally,
+ * typically through compiler command line.
+ * Value must be a number. */
+#ifndef DEBUGLEVEL
+#  define DEBUGLEVEL 0
+#endif
+
+#if (DEBUGLEVEL>=1)
+#  include <assert.h>   /* note : can still be disabled with NDEBUG */
+#  define XXH_ASSERT(c)   assert(c)
+#else
+#  define XXH_ASSERT(c)   ((void)0)
+#endif
+
+/* note : use after variable declarations */
+#define XXH_STATIC_ASSERT(c)  { enum { XXH_sa = 1/(int)(!!(c)) }; }
+
+
+/* *************************************
+*  Basic Types
+***************************************/
+#if !defined (__VMS) \
+ && (defined (__cplusplus) \
+ || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
+# include <stdint.h>
+  typedef uint8_t  xxh_u8;
+#else
+  typedef unsigned char      xxh_u8;
+#endif
+typedef XXH32_hash_t xxh_u32;
+
+
+/* ===   Memory access   === */
+
+#if (defined(XXH_FORCE_MEMORY_ACCESS) && (XXH_FORCE_MEMORY_ACCESS==2))
+
+/* Force direct memory access. Only works on CPU which support unaligned memory access in hardware */
+static xxh_u32 XXH_read32(const void* memPtr) { return *(const xxh_u32*) memPtr; }
+
+#elif (defined(XXH_FORCE_MEMORY_ACCESS) && (XXH_FORCE_MEMORY_ACCESS==1))
+
+/* __pack instructions are safer, but compiler specific, hence potentially problematic for some compilers */
+/* currently only defined for gcc and icc */
+typedef union { xxh_u32 u32; } __attribute__((packed)) unalign;
+static xxh_u32 XXH_read32(const void* ptr) { return ((const unalign*)ptr)->u32; }
+
+#else
+
+/* portable and safe solution. Generally efficient.
+ * see : http://stackoverflow.com/a/32095106/646947
+ */
+static xxh_u32 XXH_read32(const void* memPtr)
+{
+    xxh_u32 val;
+    memcpy(&val, memPtr, sizeof(val));
+    return val;
+}
+
+#endif   /* XXH_FORCE_DIRECT_MEMORY_ACCESS */
+
+
+/* ===   Endianess   === */
+typedef enum { XXH_bigEndian=0, XXH_littleEndian=1 } XXH_endianess;
+
+/* XXH_CPU_LITTLE_ENDIAN can be defined externally, for example on the compiler command line */
+#ifndef XXH_CPU_LITTLE_ENDIAN
+#  if defined(_WIN32) /* Windows is always little endian */ \
+     || defined(__LITTLE_ENDIAN__) \
+     || (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+#    define XXH_CPU_LITTLE_ENDIAN 1
+#  elif defined(__BIG_ENDIAN__) \
+     || (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#    define XXH_CPU_LITTLE_ENDIAN 0
+#  else
+static int XXH_isLittleEndian(void)
+{
+    const union { xxh_u32 u; xxh_u8 c[4]; } one = { 1 };   /* don't use static : performance detrimental  */
+    return one.c[0];
+}
+#   define XXH_CPU_LITTLE_ENDIAN   XXH_isLittleEndian()
+#  endif
+#endif
+
+
+
+
+/* ****************************************
+*  Compiler-specific Functions and Macros
+******************************************/
+#define XXH_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
+
+#ifndef __has_builtin
+#  define __has_builtin(x) 0
+#endif
+
+#if !defined(NO_CLANG_BUILTIN) && __has_builtin(__builtin_rotateleft32) && __has_builtin(__builtin_rotateleft64)
+#  define XXH_rotl32 __builtin_rotateleft32
+#  define XXH_rotl64 __builtin_rotateleft64
+/* Note : although _rotl exists for minGW (GCC under windows), performance seems poor */
+#elif defined(_MSC_VER)
+#  define XXH_rotl32(x,r) _rotl(x,r)
+#  define XXH_rotl64(x,r) _rotl64(x,r)
+#else
+#  define XXH_rotl32(x,r) (((x) << (r)) | ((x) >> (32 - (r))))
+#  define XXH_rotl64(x,r) (((x) << (r)) | ((x) >> (64 - (r))))
+#endif
+
+#if defined(_MSC_VER)     /* Visual Studio */
+#  define XXH_swap32 _byteswap_ulong
+#elif XXH_GCC_VERSION >= 403
+#  define XXH_swap32 __builtin_bswap32
+#else
+static xxh_u32 XXH_swap32 (xxh_u32 x)
+{
+    return  ((x << 24) & 0xff000000 ) |
+            ((x <<  8) & 0x00ff0000 ) |
+            ((x >>  8) & 0x0000ff00 ) |
+            ((x >> 24) & 0x000000ff );
+}
+#endif
+
+
+/* ***************************
+*  Memory reads
+*****************************/
+typedef enum { XXH_aligned, XXH_unaligned } XXH_alignment;
+
+XXH_FORCE_INLINE xxh_u32 XXH_readLE32(const void* ptr)
+{
+    return XXH_CPU_LITTLE_ENDIAN ? XXH_read32(ptr) : XXH_swap32(XXH_read32(ptr));
+}
+
+static xxh_u32 XXH_readBE32(const void* ptr)
+{
+    return XXH_CPU_LITTLE_ENDIAN ? XXH_swap32(XXH_read32(ptr)) : XXH_read32(ptr);
+}
+
+XXH_FORCE_INLINE xxh_u32
+XXH_readLE32_align(const void* ptr, XXH_alignment align)
+{
+    if (align==XXH_unaligned) {
+        return XXH_readLE32(ptr);
+    } else {
+        return XXH_CPU_LITTLE_ENDIAN ? *(const xxh_u32*)ptr : XXH_swap32(*(const xxh_u32*)ptr);
+    }
+}
+
+
+/* *************************************
+*  Misc
+***************************************/
+XXH_PUBLIC_API unsigned XXH_versionNumber (void) { return XXH_VERSION_NUMBER; }
+
+
+/* *******************************************************************
+*  32-bit hash functions
+*********************************************************************/
+static const xxh_u32 PRIME32_1 = 0x9E3779B1U;   /* 0b10011110001101110111100110110001 */
+static const xxh_u32 PRIME32_2 = 0x85EBCA77U;   /* 0b10000101111010111100101001110111 */
+static const xxh_u32 PRIME32_3 = 0xC2B2AE3DU;   /* 0b11000010101100101010111000111101 */
+static const xxh_u32 PRIME32_4 = 0x27D4EB2FU;   /* 0b00100111110101001110101100101111 */
+static const xxh_u32 PRIME32_5 = 0x165667B1U;   /* 0b00010110010101100110011110110001 */
+
+static xxh_u32 XXH32_round(xxh_u32 acc, xxh_u32 input)
+{
+    acc += input * PRIME32_2;
+    acc  = XXH_rotl32(acc, 13);
+    acc *= PRIME32_1;
+#if defined(__GNUC__) && defined(__SSE4_1__) && !defined(XXH_ENABLE_AUTOVECTORIZE)
+    /* UGLY HACK:
+     * This inline assembly hack forces acc into a normal register. This is the
+     * only thing that prevents GCC and Clang from autovectorizing the XXH32 loop
+     * (pragmas and attributes don't work for some resason) without globally
+     * disabling SSE4.1.
+     *
+     * The reason we want to avoid vectorization is because despite working on
+     * 4 integers at a time, there are multiple factors slowing XXH32 down on
+     * SSE4:
+     * - There's a ridiculous amount of lag from pmulld (10 cycles of latency on newer chips!)
+     *   making it slightly slower to multiply four integers at once compared to four
+     *   integers independently. Even when pmulld was fastest, Sandy/Ivy Bridge, it is
+     *   still not worth it to go into SSE just to multiply unless doing a long operation.
+     *
+     * - Four instructions are required to rotate,
+     *      movqda tmp,  v // not required with VEX encoding
+     *      pslld  tmp, 13 // tmp <<= 13
+     *      psrld  v,   19 // x >>= 19
+     *      por    v,  tmp // x |= tmp
+     *   compared to one for scalar:
+     *      roll   v, 13    // reliably fast across the board
+     *      shldl  v, v, 13 // Sandy Bridge and later prefer this for some reason
+     *
+     * - Instruction level parallelism is actually more beneficial here because the
+     *   SIMD actually serializes this operation: While v1 is rotating, v2 can load data,
+     *   while v3 can multiply. SSE forces them to operate together.
+     *
+     * How this hack works:
+     * __asm__(""       // Declare an assembly block but don't declare any instructions
+     *          :       // However, as an Input/Output Operand,
+     *          "+r"    // constrain a read/write operand (+) as a general purpose register (r).
+     *          (acc)   // and set acc as the operand
+     * );
+     *
+     * Because of the 'r', the compiler has promised that seed will be in a
+     * general purpose register and the '+' says that it will be 'read/write',
+     * so it has to assume it has changed. It is like volatile without all the
+     * loads and stores.
+     *
+     * Since the argument has to be in a normal register (not an SSE register),
+     * each time XXH32_round is called, it is impossible to vectorize. */
+    __asm__("" : "+r" (acc));
+#endif
+    return acc;
+}
+
+/* mix all bits */
+static xxh_u32 XXH32_avalanche(xxh_u32 h32)
+{
+    h32 ^= h32 >> 15;
+    h32 *= PRIME32_2;
+    h32 ^= h32 >> 13;
+    h32 *= PRIME32_3;
+    h32 ^= h32 >> 16;
+    return(h32);
+}
+
+#define XXH_get32bits(p) XXH_readLE32_align(p, align)
+
+static xxh_u32
+XXH32_finalize(xxh_u32 h32, const xxh_u8* ptr, size_t len, XXH_alignment align)
+{
+#define PROCESS1               \
+    h32 += (*ptr++) * PRIME32_5; \
+    h32 = XXH_rotl32(h32, 11) * PRIME32_1 ;
+
+#define PROCESS4                         \
+    h32 += XXH_get32bits(ptr) * PRIME32_3; \
+    ptr+=4;                                \
+    h32  = XXH_rotl32(h32, 17) * PRIME32_4 ;
+
+    /* Compact rerolled version */
+    if (XXH_REROLL) {
+        len &= 15;
+        while (len >= 4) {
+            PROCESS4;
+            len -= 4;
+        }
+        while (len > 0) {
+            PROCESS1;
+            --len;
+        }
+        return XXH32_avalanche(h32);
+    } else {
+         switch(len&15) /* or switch(bEnd - p) */ {
+           case 12:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 8:       PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 4:       PROCESS4;
+                         return XXH32_avalanche(h32);
+
+           case 13:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 9:       PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 5:       PROCESS4;
+                         PROCESS1;
+                         return XXH32_avalanche(h32);
+
+           case 14:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 10:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 6:       PROCESS4;
+                         PROCESS1;
+                         PROCESS1;
+                         return XXH32_avalanche(h32);
+
+           case 15:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 11:      PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 7:       PROCESS4;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 3:       PROCESS1;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 2:       PROCESS1;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 1:       PROCESS1;
+                         FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 0:       return XXH32_avalanche(h32);
+        }
+        XXH_ASSERT(0);
+        return h32;   /* reaching this point is deemed impossible */
+    }
+}
+
+XXH_FORCE_INLINE xxh_u32
+XXH32_endian_align(const xxh_u8* input, size_t len, xxh_u32 seed, XXH_alignment align)
+{
+    const xxh_u8* bEnd = input + len;
+    xxh_u32 h32;
+
+#if defined(XXH_ACCEPT_NULL_INPUT_POINTER) && (XXH_ACCEPT_NULL_INPUT_POINTER>=1)
+    if (input==NULL) {
+        len=0;
+        bEnd=input=(const xxh_u8*)(size_t)16;
+    }
+#endif
+
+    if (len>=16) {
+        const xxh_u8* const limit = bEnd - 15;
+        xxh_u32 v1 = seed + PRIME32_1 + PRIME32_2;
+        xxh_u32 v2 = seed + PRIME32_2;
+        xxh_u32 v3 = seed + 0;
+        xxh_u32 v4 = seed - PRIME32_1;
+
+        do {
+            v1 = XXH32_round(v1, XXH_get32bits(input)); input += 4;
+            v2 = XXH32_round(v2, XXH_get32bits(input)); input += 4;
+            v3 = XXH32_round(v3, XXH_get32bits(input)); input += 4;
+            v4 = XXH32_round(v4, XXH_get32bits(input)); input += 4;
+        } while (input < limit);
+
+        h32 = XXH_rotl32(v1, 1)  + XXH_rotl32(v2, 7)
+            + XXH_rotl32(v3, 12) + XXH_rotl32(v4, 18);
+    } else {
+        h32  = seed + PRIME32_5;
+    }
+
+    h32 += (xxh_u32)len;
+
+    return XXH32_finalize(h32, input, len&15, align);
+}
+
+
+XXH_PUBLIC_API XXH32_hash_t XXH32 (const void* input, size_t len, XXH32_hash_t seed)
+{
+#if 0
+    /* Simple version, good for code maintenance, but unfortunately slow for small inputs */
+    XXH32_state_t state;
+    XXH32_reset(&state, seed);
+    XXH32_update(&state, (const xxh_u8*)input, len);
+    return XXH32_digest(&state);
+
+#else
+
+    if (XXH_FORCE_ALIGN_CHECK) {
+        if ((((size_t)input) & 3) == 0) {   /* Input is 4-bytes aligned, leverage the speed benefit */
+            return XXH32_endian_align((const xxh_u8*)input, len, seed, XXH_aligned);
+    }   }
+
+    return XXH32_endian_align((const xxh_u8*)input, len, seed, XXH_unaligned);
+#endif
+}
+
+
+
+/*======   Hash streaming   ======*/
+
+XXH_PUBLIC_API XXH32_state_t* XXH32_createState(void)
+{
+    return (XXH32_state_t*)XXH_malloc(sizeof(XXH32_state_t));
+}
+XXH_PUBLIC_API XXH_errorcode XXH32_freeState(XXH32_state_t* statePtr)
+{
+    XXH_free(statePtr);
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API void XXH32_copyState(XXH32_state_t* dstState, const XXH32_state_t* srcState)
+{
+    memcpy(dstState, srcState, sizeof(*dstState));
+}
+
+XXH_PUBLIC_API XXH_errorcode XXH32_reset(XXH32_state_t* statePtr, XXH32_hash_t seed)
+{
+    XXH32_state_t state;   /* using a local state to memcpy() in order to avoid strict-aliasing warnings */
+    memset(&state, 0, sizeof(state));
+    state.v1 = seed + PRIME32_1 + PRIME32_2;
+    state.v2 = seed + PRIME32_2;
+    state.v3 = seed + 0;
+    state.v4 = seed - PRIME32_1;
+    /* do not write into reserved, planned to be removed in a future version */
+    memcpy(statePtr, &state, sizeof(state) - sizeof(state.reserved));
+    return XXH_OK;
+}
+
+
+XXH_PUBLIC_API XXH_errorcode
+XXH32_update(XXH32_state_t* state, const void* input, size_t len)
+{
+    if (input==NULL)
+#if defined(XXH_ACCEPT_NULL_INPUT_POINTER) && (XXH_ACCEPT_NULL_INPUT_POINTER>=1)
+        return XXH_OK;
+#else
+        return XXH_ERROR;
+#endif
+
+    {   const xxh_u8* p = (const xxh_u8*)input;
+        const xxh_u8* const bEnd = p + len;
+
+        state->total_len_32 += (XXH32_hash_t)len;
+        state->large_len |= (XXH32_hash_t)((len>=16) | (state->total_len_32>=16));
+
+        if (state->memsize + len < 16)  {   /* fill in tmp buffer */
+            XXH_memcpy((xxh_u8*)(state->mem32) + state->memsize, input, len);
+            state->memsize += (XXH32_hash_t)len;
+            return XXH_OK;
+        }
+
+        if (state->memsize) {   /* some data left from previous update */
+            XXH_memcpy((xxh_u8*)(state->mem32) + state->memsize, input, 16-state->memsize);
+            {   const xxh_u32* p32 = state->mem32;
+                state->v1 = XXH32_round(state->v1, XXH_readLE32(p32)); p32++;
+                state->v2 = XXH32_round(state->v2, XXH_readLE32(p32)); p32++;
+                state->v3 = XXH32_round(state->v3, XXH_readLE32(p32)); p32++;
+                state->v4 = XXH32_round(state->v4, XXH_readLE32(p32));
+            }
+            p += 16-state->memsize;
+            state->memsize = 0;
+        }
+
+        // uintptr_t casts added to avoid array-bounds error on
+        // some inlined calls
+        if ((uintptr_t)p <= (uintptr_t)bEnd - 16) {
+            const uintptr_t limit = (uintptr_t)bEnd - 16;
+            xxh_u32 v1 = state->v1;
+            xxh_u32 v2 = state->v2;
+            xxh_u32 v3 = state->v3;
+            xxh_u32 v4 = state->v4;
+
+            do {
+                v1 = XXH32_round(v1, XXH_readLE32(p)); p+=4;
+                v2 = XXH32_round(v2, XXH_readLE32(p)); p+=4;
+                v3 = XXH32_round(v3, XXH_readLE32(p)); p+=4;
+                v4 = XXH32_round(v4, XXH_readLE32(p)); p+=4;
+            } while ((uintptr_t)p <= limit);
+
+            state->v1 = v1;
+            state->v2 = v2;
+            state->v3 = v3;
+            state->v4 = v4;
+        }
+
+        if (p < bEnd) {
+            XXH_memcpy(state->mem32, p, (size_t)(bEnd-p));
+            state->memsize = (unsigned)(bEnd-p);
+        }
+    }
+
+    return XXH_OK;
+}
+
+
+XXH_PUBLIC_API XXH32_hash_t XXH32_digest (const XXH32_state_t* state)
+{
+    xxh_u32 h32;
+
+    if (state->large_len) {
+        h32 = XXH_rotl32(state->v1, 1)
+            + XXH_rotl32(state->v2, 7)
+            + XXH_rotl32(state->v3, 12)
+            + XXH_rotl32(state->v4, 18);
+    } else {
+        h32 = state->v3 /* == seed */ + PRIME32_5;
+    }
+
+    h32 += state->total_len_32;
+
+    return XXH32_finalize(h32, (const xxh_u8*)state->mem32, state->memsize, XXH_aligned);
+}
+
+
+/*======   Canonical representation   ======*/
+
+/*! Default XXH result types are basic unsigned 32 and 64 bits.
+*   The canonical representation follows human-readable write convention, aka big-endian (large digits first).
+*   These functions allow transformation of hash result into and from its canonical format.
+*   This way, hash values can be written into a file or buffer, remaining comparable across different systems.
+*/
+
+XXH_PUBLIC_API void XXH32_canonicalFromHash(XXH32_canonical_t* dst, XXH32_hash_t hash)
+{
+    XXH_STATIC_ASSERT(sizeof(XXH32_canonical_t) == sizeof(XXH32_hash_t));
+    if (XXH_CPU_LITTLE_ENDIAN) hash = XXH_swap32(hash);
+    memcpy(dst, &hash, sizeof(*dst));
+}
+
+XXH_PUBLIC_API XXH32_hash_t XXH32_hashFromCanonical(const XXH32_canonical_t* src)
+{
+    return XXH_readBE32(src);
+}
+
+
+#ifndef XXH_NO_LONG_LONG
+
+/* *******************************************************************
+*  64-bit hash functions
+*********************************************************************/
+
+/*======   Memory access   ======*/
+
+typedef XXH64_hash_t xxh_u64;
+
+
+/*! XXH_REROLL_XXH64:
+ * Whether to reroll the XXH64_finalize() loop.
+ *
+ * Just like XXH32, we can unroll the XXH64_finalize() loop. This can be a performance gain
+ * on 64-bit hosts, as only one jump is required.
+ *
+ * However, on 32-bit hosts, because arithmetic needs to be done with two 32-bit registers,
+ * and 64-bit arithmetic needs to be simulated, it isn't beneficial to unroll. The code becomes
+ * ridiculously large (the largest function in the binary on i386!), and rerolling it saves
+ * anywhere from 3kB to 20kB. It is also slightly faster because it fits into cache better
+ * and is more likely to be inlined by the compiler.
+ *
+ * If XXH_REROLL is defined, this is ignored and the loop is always rerolled. */
+#ifndef XXH_REROLL_XXH64
+#  if (defined(__ILP32__) || defined(_ILP32)) /* ILP32 is often defined on 32-bit GCC family */ \
+   || !(defined(__x86_64__) || defined(_M_X64) || defined(_M_AMD64) /* x86-64 */ \
+     || defined(_M_ARM64) || defined(__aarch64__) || defined(__arm64__) /* aarch64 */ \
+     || defined(__PPC64__) || defined(__PPC64LE__) || defined(__ppc64__) || defined(__powerpc64__) /* ppc64 */ \
+     || defined(__mips64__) || defined(__mips64)) /* mips64 */ \
+   || (!defined(SIZE_MAX) || SIZE_MAX < ULLONG_MAX) /* check limits */
+#    define XXH_REROLL_XXH64 1
+#  else
+#    define XXH_REROLL_XXH64 0
+#  endif
+#endif /* !defined(XXH_REROLL_XXH64) */
+
+#if (defined(XXH_FORCE_MEMORY_ACCESS) && (XXH_FORCE_MEMORY_ACCESS==2))
+
+/* Force direct memory access. Only works on CPU which support unaligned memory access in hardware */
+static xxh_u64 XXH_read64(const void* memPtr) { return *(const xxh_u64*) memPtr; }
+
+#elif (defined(XXH_FORCE_MEMORY_ACCESS) && (XXH_FORCE_MEMORY_ACCESS==1))
+
+/* __pack instructions are safer, but compiler specific, hence potentially problematic for some compilers */
+/* currently only defined for gcc and icc */
+typedef union { xxh_u32 u32; xxh_u64 u64; } __attribute__((packed)) unalign64;
+static xxh_u64 XXH_read64(const void* ptr) { return ((const unalign64*)ptr)->u64; }
+
+#else
+
+/* portable and safe solution. Generally efficient.
+ * see : http://stackoverflow.com/a/32095106/646947
+ */
+
+static xxh_u64 XXH_read64(const void* memPtr)
+{
+    xxh_u64 val;
+    memcpy(&val, memPtr, sizeof(val));
+    return val;
+}
+
+#endif   /* XXH_FORCE_DIRECT_MEMORY_ACCESS */
+
+#if defined(_MSC_VER)     /* Visual Studio */
+#  define XXH_swap64 _byteswap_uint64
+#elif XXH_GCC_VERSION >= 403
+#  define XXH_swap64 __builtin_bswap64
+#else
+static xxh_u64 XXH_swap64 (xxh_u64 x)
+{
+    return  ((x << 56) & 0xff00000000000000ULL) |
+            ((x << 40) & 0x00ff000000000000ULL) |
+            ((x << 24) & 0x0000ff0000000000ULL) |
+            ((x << 8)  & 0x000000ff00000000ULL) |
+            ((x >> 8)  & 0x00000000ff000000ULL) |
+            ((x >> 24) & 0x0000000000ff0000ULL) |
+            ((x >> 40) & 0x000000000000ff00ULL) |
+            ((x >> 56) & 0x00000000000000ffULL);
+}
+#endif
+
+XXH_FORCE_INLINE xxh_u64 XXH_readLE64(const void* ptr)
+{
+    return XXH_CPU_LITTLE_ENDIAN ? XXH_read64(ptr) : XXH_swap64(XXH_read64(ptr));
+}
+
+static xxh_u64 XXH_readBE64(const void* ptr)
+{
+    return XXH_CPU_LITTLE_ENDIAN ? XXH_swap64(XXH_read64(ptr)) : XXH_read64(ptr);
+}
+
+XXH_FORCE_INLINE xxh_u64
+XXH_readLE64_align(const void* ptr, XXH_alignment align)
+{
+    if (align==XXH_unaligned)
+        return XXH_readLE64(ptr);
+    else
+        return XXH_CPU_LITTLE_ENDIAN ? *(const xxh_u64*)ptr : XXH_swap64(*(const xxh_u64*)ptr);
+}
+
+
+/*======   xxh64   ======*/
+
+static const xxh_u64 PRIME64_1 = 0x9E3779B185EBCA87ULL;   /* 0b1001111000110111011110011011000110000101111010111100101010000111 */
+static const xxh_u64 PRIME64_2 = 0xC2B2AE3D27D4EB4FULL;   /* 0b1100001010110010101011100011110100100111110101001110101101001111 */
+static const xxh_u64 PRIME64_3 = 0x165667B19E3779F9ULL;   /* 0b0001011001010110011001111011000110011110001101110111100111111001 */
+static const xxh_u64 PRIME64_4 = 0x85EBCA77C2B2AE63ULL;   /* 0b1000010111101011110010100111011111000010101100101010111001100011 */
+static const xxh_u64 PRIME64_5 = 0x27D4EB2F165667C5ULL;   /* 0b0010011111010100111010110010111100010110010101100110011111000101 */
+
+static xxh_u64 XXH64_round(xxh_u64 acc, xxh_u64 input)
+{
+    acc += input * PRIME64_2;
+    acc  = XXH_rotl64(acc, 31);
+    acc *= PRIME64_1;
+    return acc;
+}
+
+static xxh_u64 XXH64_mergeRound(xxh_u64 acc, xxh_u64 val)
+{
+    val  = XXH64_round(0, val);
+    acc ^= val;
+    acc  = acc * PRIME64_1 + PRIME64_4;
+    return acc;
+}
+
+static xxh_u64 XXH64_avalanche(xxh_u64 h64)
+{
+    h64 ^= h64 >> 33;
+    h64 *= PRIME64_2;
+    h64 ^= h64 >> 29;
+    h64 *= PRIME64_3;
+    h64 ^= h64 >> 32;
+    return h64;
+}
+
+
+#define XXH_get64bits(p) XXH_readLE64_align(p, align)
+
+static xxh_u64
+XXH64_finalize(xxh_u64 h64, const xxh_u8* ptr, size_t len, XXH_alignment align)
+{
+#define PROCESS1_64            \
+    h64 ^= (*ptr++) * PRIME64_5; \
+    h64 = XXH_rotl64(h64, 11) * PRIME64_1;
+
+#define PROCESS4_64          \
+    h64 ^= (xxh_u64)(XXH_get32bits(ptr)) * PRIME64_1; \
+    ptr+=4;                    \
+    h64 = XXH_rotl64(h64, 23) * PRIME64_2 + PRIME64_3;
+
+#define PROCESS8_64 {        \
+    xxh_u64 const k1 = XXH64_round(0, XXH_get64bits(ptr)); \
+    ptr+=8;                    \
+    h64 ^= k1;               \
+    h64  = XXH_rotl64(h64,27) * PRIME64_1 + PRIME64_4; \
+}
+
+    /* Rerolled version for 32-bit targets is faster and much smaller. */
+    if (XXH_REROLL || XXH_REROLL_XXH64) {
+        len &= 31;
+        while (len >= 8) {
+            PROCESS8_64;
+            len -= 8;
+        }
+        if (len >= 4) {
+            PROCESS4_64;
+            len -= 4;
+        }
+        while (len > 0) {
+            PROCESS1_64;
+            --len;
+        }
+         return  XXH64_avalanche(h64);
+    } else {
+        switch(len & 31) {
+           case 24: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 16: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  8: PROCESS8_64;
+                    return XXH64_avalanche(h64);
+
+           case 28: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 20: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 12: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  4: PROCESS4_64;
+                    return XXH64_avalanche(h64);
+
+           case 25: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 17: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  9: PROCESS8_64;
+                    PROCESS1_64;
+                    return XXH64_avalanche(h64);
+
+           case 29: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 21: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 13: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  5: PROCESS4_64;
+                    PROCESS1_64;
+                    return XXH64_avalanche(h64);
+
+           case 26: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 18: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 10: PROCESS8_64;
+                    PROCESS1_64;
+                    PROCESS1_64;
+                    return XXH64_avalanche(h64);
+
+           case 30: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 22: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 14: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  6: PROCESS4_64;
+                    PROCESS1_64;
+                    PROCESS1_64;
+                    return XXH64_avalanche(h64);
+
+           case 27: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 19: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 11: PROCESS8_64;
+                    PROCESS1_64;
+                    PROCESS1_64;
+                    PROCESS1_64;
+                    return XXH64_avalanche(h64);
+
+           case 31: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 23: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case 15: PROCESS8_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  7: PROCESS4_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  3: PROCESS1_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  2: PROCESS1_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  1: PROCESS1_64;
+                    FALLTHROUGH_INTENDED;
+                         /* fallthrough */
+           case  0: return XXH64_avalanche(h64);
+        }
+    }
+    /* impossible to reach */
+    XXH_ASSERT(0);
+    return 0;  /* unreachable, but some compilers complain without it */
+}
+
+XXH_FORCE_INLINE xxh_u64
+XXH64_endian_align(const xxh_u8* input, size_t len, xxh_u64 seed, XXH_alignment align)
+{
+    const xxh_u8* bEnd = input + len;
+    xxh_u64 h64;
+
+#if defined(XXH_ACCEPT_NULL_INPUT_POINTER) && (XXH_ACCEPT_NULL_INPUT_POINTER>=1)
+    if (input==NULL) {
+        len=0;
+        bEnd=input=(const xxh_u8*)(size_t)32;
+    }
+#endif
+
+    if (len>=32) {
+        const xxh_u8* const limit = bEnd - 32;
+        xxh_u64 v1 = seed + PRIME64_1 + PRIME64_2;
+        xxh_u64 v2 = seed + PRIME64_2;
+        xxh_u64 v3 = seed + 0;
+        xxh_u64 v4 = seed - PRIME64_1;
+
+        do {
+            v1 = XXH64_round(v1, XXH_get64bits(input)); input+=8;
+            v2 = XXH64_round(v2, XXH_get64bits(input)); input+=8;
+            v3 = XXH64_round(v3, XXH_get64bits(input)); input+=8;
+            v4 = XXH64_round(v4, XXH_get64bits(input)); input+=8;
+        } while (input<=limit);
+
+        h64 = XXH_rotl64(v1, 1) + XXH_rotl64(v2, 7) + XXH_rotl64(v3, 12) + XXH_rotl64(v4, 18);
+        h64 = XXH64_mergeRound(h64, v1);
+        h64 = XXH64_mergeRound(h64, v2);
+        h64 = XXH64_mergeRound(h64, v3);
+        h64 = XXH64_mergeRound(h64, v4);
+
+    } else {
+        h64  = seed + PRIME64_5;
+    }
+
+    h64 += (xxh_u64) len;
+
+    return XXH64_finalize(h64, input, len, align);
+}
+
+
+XXH_PUBLIC_API XXH64_hash_t XXH64 (const void* input, size_t len, XXH64_hash_t seed)
+{
+#if 0
+    /* Simple version, good for code maintenance, but unfortunately slow for small inputs */
+    XXH64_state_t state;
+    XXH64_reset(&state, seed);
+    XXH64_update(&state, (const xxh_u8*)input, len);
+    return XXH64_digest(&state);
+
+#else
+
+    if (XXH_FORCE_ALIGN_CHECK) {
+        if ((((size_t)input) & 7)==0) {  /* Input is aligned, let's leverage the speed advantage */
+            return XXH64_endian_align((const xxh_u8*)input, len, seed, XXH_aligned);
+    }   }
+
+    return XXH64_endian_align((const xxh_u8*)input, len, seed, XXH_unaligned);
+
+#endif
+}
+
+/*======   Hash Streaming   ======*/
+
+XXH_PUBLIC_API XXH64_state_t* XXH64_createState(void)
+{
+    return (XXH64_state_t*)XXH_malloc(sizeof(XXH64_state_t));
+}
+XXH_PUBLIC_API XXH_errorcode XXH64_freeState(XXH64_state_t* statePtr)
+{
+    XXH_free(statePtr);
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API void XXH64_copyState(XXH64_state_t* dstState, const XXH64_state_t* srcState)
+{
+    memcpy(dstState, srcState, sizeof(*dstState));
+}
+
+XXH_PUBLIC_API XXH_errorcode XXH64_reset(XXH64_state_t* statePtr, XXH64_hash_t seed)
+{
+    XXH64_state_t state;   /* using a local state to memcpy() in order to avoid strict-aliasing warnings */
+    memset(&state, 0, sizeof(state));
+    state.v1 = seed + PRIME64_1 + PRIME64_2;
+    state.v2 = seed + PRIME64_2;
+    state.v3 = seed + 0;
+    state.v4 = seed - PRIME64_1;
+     /* do not write into reserved64, might be removed in a future version */
+    memcpy(statePtr, &state, sizeof(state) - sizeof(state.reserved64));
+    return XXH_OK;
+}
+
+XXH_PUBLIC_API XXH_errorcode
+XXH64_update (XXH64_state_t* state, const void* input, size_t len)
+{
+    if (input==NULL)
+#if defined(XXH_ACCEPT_NULL_INPUT_POINTER) && (XXH_ACCEPT_NULL_INPUT_POINTER>=1)
+        return XXH_OK;
+#else
+        return XXH_ERROR;
+#endif
+
+    {   const xxh_u8* p = (const xxh_u8*)input;
+        const xxh_u8* const bEnd = p + len;
+
+        state->total_len += len;
+
+        if (state->memsize + len < 32) {  /* fill in tmp buffer */
+            XXH_memcpy(((xxh_u8*)state->mem64) + state->memsize, input, len);
+            state->memsize += (xxh_u32)len;
+            return XXH_OK;
+        }
+
+        if (state->memsize) {   /* tmp buffer is full */
+            XXH_memcpy(((xxh_u8*)state->mem64) + state->memsize, input, 32-state->memsize);
+            state->v1 = XXH64_round(state->v1, XXH_readLE64(state->mem64+0));
+            state->v2 = XXH64_round(state->v2, XXH_readLE64(state->mem64+1));
+            state->v3 = XXH64_round(state->v3, XXH_readLE64(state->mem64+2));
+            state->v4 = XXH64_round(state->v4, XXH_readLE64(state->mem64+3));
+            p += 32-state->memsize;
+            state->memsize = 0;
+        }
+
+        // uintptr_t casts added to avoid array-bounds error on
+        // some inlined calls
+        if ((uintptr_t)p + 32 <= (uintptr_t)bEnd) {
+            const uintptr_t limit = (uintptr_t)bEnd - 32;
+            xxh_u64 v1 = state->v1;
+            xxh_u64 v2 = state->v2;
+            xxh_u64 v3 = state->v3;
+            xxh_u64 v4 = state->v4;
+
+            do {
+                v1 = XXH64_round(v1, XXH_readLE64(p)); p+=8;
+                v2 = XXH64_round(v2, XXH_readLE64(p)); p+=8;
+                v3 = XXH64_round(v3, XXH_readLE64(p)); p+=8;
+                v4 = XXH64_round(v4, XXH_readLE64(p)); p+=8;
+            } while ((uintptr_t)p <= limit);
+
+            state->v1 = v1;
+            state->v2 = v2;
+            state->v3 = v3;
+            state->v4 = v4;
+        }
+
+        if (p < bEnd) {
+            XXH_memcpy(state->mem64, p, (size_t)(bEnd-p));
+            state->memsize = (unsigned)(bEnd-p);
+        }
+    }
+
+    return XXH_OK;
+}
+
+
+XXH_PUBLIC_API XXH64_hash_t XXH64_digest (const XXH64_state_t* state)
+{
+    xxh_u64 h64;
+
+    if (state->total_len >= 32) {
+        xxh_u64 const v1 = state->v1;
+        xxh_u64 const v2 = state->v2;
+        xxh_u64 const v3 = state->v3;
+        xxh_u64 const v4 = state->v4;
+
+        h64 = XXH_rotl64(v1, 1) + XXH_rotl64(v2, 7) + XXH_rotl64(v3, 12) + XXH_rotl64(v4, 18);
+        h64 = XXH64_mergeRound(h64, v1);
+        h64 = XXH64_mergeRound(h64, v2);
+        h64 = XXH64_mergeRound(h64, v3);
+        h64 = XXH64_mergeRound(h64, v4);
+    } else {
+        h64  = state->v3 /*seed*/ + PRIME64_5;
+    }
+
+    h64 += (xxh_u64) state->total_len;
+
+    return XXH64_finalize(h64, (const xxh_u8*)state->mem64, (size_t)state->total_len, XXH_aligned);
+}
+
+
+/*====== Canonical representation   ======*/
+
+XXH_PUBLIC_API void XXH64_canonicalFromHash(XXH64_canonical_t* dst, XXH64_hash_t hash)
+{
+    XXH_STATIC_ASSERT(sizeof(XXH64_canonical_t) == sizeof(XXH64_hash_t));
+    if (XXH_CPU_LITTLE_ENDIAN) hash = XXH_swap64(hash);
+    memcpy(dst, &hash, sizeof(*dst));
+}
+
+XXH_PUBLIC_API XXH64_hash_t XXH64_hashFromCanonical(const XXH64_canonical_t* src)
+{
+    return XXH_readBE64(src);
+}
+
+
+
+/* *********************************************************************
+*  XXH3
+*  New generation hash designed for speed on small keys and vectorization
+************************************************************************ */
+
+#include "xxh3p.h" /* XXH3 preview for RocksDB */
+
+
+#endif  /* XXH_NO_LONG_LONG */
+
+#endif  /* XXHASH_C_01393879 */
diff --git a/src/rocksdb/util/xxhash.h b/src/rocksdb/util/xxhash.h
new file mode 100644
index 000000000..59d9b97d6
--- /dev/null
+++ b/src/rocksdb/util/xxhash.h
@@ -0,0 +1,598 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+/*
+   xxHash - Extremely Fast Hash algorithm
+   Header File
+   Copyright (C) 2012-2016, Yann Collet.
+
+   BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions are
+   met:
+
+       * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+       * Redistributions in binary form must reproduce the above
+   copyright notice, this list of conditions and the following disclaimer
+   in the documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+   You can contact the author at :
+   - xxHash source repository : https://github.com/Cyan4973/xxHash
+*/
+
+/* Notice extracted from xxHash homepage :
+
+xxHash is an extremely fast Hash algorithm, running at RAM speed limits.
+It also successfully passes all tests from the SMHasher suite.
+
+Comparison (single thread, Windows Seven 32 bits, using SMHasher on a Core 2 Duo @3GHz)
+
+Name            Speed       Q.Score   Author
+xxHash          5.4 GB/s     10
+CrapWow         3.2 GB/s      2       Andrew
+MumurHash 3a    2.7 GB/s     10       Austin Appleby
+SpookyHash      2.0 GB/s     10       Bob Jenkins
+SBox            1.4 GB/s      9       Bret Mulvey
+Lookup3         1.2 GB/s      9       Bob Jenkins
+SuperFastHash   1.2 GB/s      1       Paul Hsieh
+CityHash64      1.05 GB/s    10       Pike & Alakuijala
+FNV             0.55 GB/s     5       Fowler, Noll, Vo
+CRC32           0.43 GB/s #   9
+MD5-32          0.33 GB/s    10       Ronald L. Rivest
+SHA1-32         0.28 GB/s    10
+
+Note #: other CRC32 implementations can be over 40x faster than SMHasher's:
+http://fastcompression.blogspot.com/2019/03/presenting-xxh3.html?showComment=1552696407071#c3490092340461170735
+
+Q.Score is a measure of quality of the hash function.
+It depends on successfully passing SMHasher test set.
+10 is a perfect score.
+
+A 64-bit version, named XXH64, is available since r35.
+It offers much better speed, but for 64-bit applications only.
+Name     Speed on 64 bits    Speed on 32 bits
+XXH64       13.8 GB/s            1.9 GB/s
+XXH32        6.8 GB/s            6.0 GB/s
+*/
+
+#ifndef XXHASH_H_5627135585666179
+#define XXHASH_H_5627135585666179 1
+
+/* BEGIN RocksDB customizations */
+#ifndef XXH_STATIC_LINKING_ONLY
+#define XXH_STATIC_LINKING_ONLY 1 /* access experimental APIs like XXH3 */
+#endif
+#define XXH_NAMESPACE ROCKSDB_
+/* END RocksDB customizations */
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+
+/* ****************************
+*  Definitions
+******************************/
+#include <stddef.h>   /* size_t */
+typedef enum { XXH_OK=0, XXH_ERROR } XXH_errorcode;
+
+
+/* ****************************
+ *  API modifier
+ ******************************/
+/** XXH_INLINE_ALL (and XXH_PRIVATE_API)
+ *  This build macro includes xxhash functions in `static` mode
+ *  in order to inline them, and remove their symbol from the public list.
+ *  Inlining offers great performance improvement on small keys,
+ *  and dramatic ones when length is expressed as a compile-time constant.
+ *  See https://fastcompression.blogspot.com/2018/03/xxhash-for-small-keys-impressive-power.html .
+ *  Methodology :
+ *     #define XXH_INLINE_ALL
+ *     #include "xxhash.h"
+ * `xxhash.c` is automatically included.
+ *  It's not useful to compile and link it as a separate object.
+ */
+#if defined(XXH_INLINE_ALL) || defined(XXH_PRIVATE_API)
+#  ifndef XXH_STATIC_LINKING_ONLY
+#    define XXH_STATIC_LINKING_ONLY
+#  endif
+#  if defined(__GNUC__)
+#    define XXH_PUBLIC_API static __inline __attribute__((unused))
+#  elif defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
+#    define XXH_PUBLIC_API static inline
+#  elif defined(_MSC_VER)
+#    define XXH_PUBLIC_API static __inline
+#  else
+     /* this version may generate warnings for unused static functions */
+#    define XXH_PUBLIC_API static
+#  endif
+#else
+#  if defined(WIN32) && defined(_MSC_VER) && (defined(XXH_IMPORT) || defined(XXH_EXPORT))
+#    ifdef XXH_EXPORT
+#      define XXH_PUBLIC_API __declspec(dllexport)
+#    elif XXH_IMPORT
+#      define XXH_PUBLIC_API __declspec(dllimport)
+#    endif
+#  else
+#    define XXH_PUBLIC_API   /* do nothing */
+#  endif
+#endif /* XXH_INLINE_ALL || XXH_PRIVATE_API */
+
+/*! XXH_NAMESPACE, aka Namespace Emulation :
+ *
+ * If you want to include _and expose_ xxHash functions from within your own library,
+ * but also want to avoid symbol collisions with other libraries which may also include xxHash,
+ *
+ * you can use XXH_NAMESPACE, to automatically prefix any public symbol from xxhash library
+ * with the value of XXH_NAMESPACE (therefore, avoid NULL and numeric values).
+ *
+ * Note that no change is required within the calling program as long as it includes `xxhash.h` :
+ * regular symbol name will be automatically translated by this header.
+ */
+#ifdef XXH_NAMESPACE
+#  define XXH_CAT(A,B) A##B
+#  define XXH_NAME2(A,B) XXH_CAT(A,B)
+#  define XXH_versionNumber XXH_NAME2(XXH_NAMESPACE, XXH_versionNumber)
+#  define XXH32 XXH_NAME2(XXH_NAMESPACE, XXH32)
+#  define XXH32_createState XXH_NAME2(XXH_NAMESPACE, XXH32_createState)
+#  define XXH32_freeState XXH_NAME2(XXH_NAMESPACE, XXH32_freeState)
+#  define XXH32_reset XXH_NAME2(XXH_NAMESPACE, XXH32_reset)
+#  define XXH32_update XXH_NAME2(XXH_NAMESPACE, XXH32_update)
+#  define XXH32_digest XXH_NAME2(XXH_NAMESPACE, XXH32_digest)
+#  define XXH32_copyState XXH_NAME2(XXH_NAMESPACE, XXH32_copyState)
+#  define XXH32_canonicalFromHash XXH_NAME2(XXH_NAMESPACE, XXH32_canonicalFromHash)
+#  define XXH32_hashFromCanonical XXH_NAME2(XXH_NAMESPACE, XXH32_hashFromCanonical)
+#  define XXH64 XXH_NAME2(XXH_NAMESPACE, XXH64)
+#  define XXH64_createState XXH_NAME2(XXH_NAMESPACE, XXH64_createState)
+#  define XXH64_freeState XXH_NAME2(XXH_NAMESPACE, XXH64_freeState)
+#  define XXH64_reset XXH_NAME2(XXH_NAMESPACE, XXH64_reset)
+#  define XXH64_update XXH_NAME2(XXH_NAMESPACE, XXH64_update)
+#  define XXH64_digest XXH_NAME2(XXH_NAMESPACE, XXH64_digest)
+#  define XXH64_copyState XXH_NAME2(XXH_NAMESPACE, XXH64_copyState)
+#  define XXH64_canonicalFromHash XXH_NAME2(XXH_NAMESPACE, XXH64_canonicalFromHash)
+#  define XXH64_hashFromCanonical XXH_NAME2(XXH_NAMESPACE, XXH64_hashFromCanonical)
+#endif
+
+
+/* *************************************
+*  Version
+***************************************/
+#define XXH_VERSION_MAJOR    0
+#define XXH_VERSION_MINOR    7
+#define XXH_VERSION_RELEASE  2
+#define XXH_VERSION_NUMBER  (XXH_VERSION_MAJOR *100*100 + XXH_VERSION_MINOR *100 + XXH_VERSION_RELEASE)
+XXH_PUBLIC_API unsigned XXH_versionNumber (void);
+
+
+/*-**********************************************************************
+*  32-bit hash
+************************************************************************/
+#if !defined (__VMS) \
+  && (defined (__cplusplus) \
+  || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
+#   include <stdint.h>
+    typedef uint32_t XXH32_hash_t;
+#else
+#   include <limits.h>
+#   if UINT_MAX == 0xFFFFFFFFUL
+      typedef unsigned int XXH32_hash_t;
+#   else
+#     if ULONG_MAX == 0xFFFFFFFFUL
+        typedef unsigned long XXH32_hash_t;
+#     else
+#       error "unsupported platform : need a 32-bit type"
+#     endif
+#   endif
+#endif
+
+/*! XXH32() :
+    Calculate the 32-bit hash of sequence "length" bytes stored at memory address "input".
+    The memory between input & input+length must be valid (allocated and read-accessible).
+    "seed" can be used to alter the result predictably.
+    Speed on Core 2 Duo @ 3 GHz (single thread, SMHasher benchmark) : 5.4 GB/s */
+XXH_PUBLIC_API XXH32_hash_t XXH32 (const void* input, size_t length, XXH32_hash_t seed);
+
+/*======   Streaming   ======*/
+
+/*
+ * Streaming functions generate the xxHash value from an incrememtal input.
+ * This method is slower than single-call functions, due to state management.
+ * For small inputs, prefer `XXH32()` and `XXH64()`, which are better optimized.
+ *
+ * XXH state must first be allocated, using XXH*_createState() .
+ *
+ * Start a new hash by initializing state with a seed, using XXH*_reset().
+ *
+ * Then, feed the hash state by calling XXH*_update() as many times as necessary.
+ * The function returns an error code, with 0 meaning OK, and any other value meaning there is an error.
+ *
+ * Finally, a hash value can be produced anytime, by using XXH*_digest().
+ * This function returns the nn-bits hash as an int or long long.
+ *
+ * It's still possible to continue inserting input into the hash state after a digest,
+ * and generate some new hash values later on, by invoking again XXH*_digest().
+ *
+ * When done, release the state, using XXH*_freeState().
+ */
+
+typedef struct XXH32_state_s XXH32_state_t;   /* incomplete type */
+XXH_PUBLIC_API XXH32_state_t* XXH32_createState(void);
+XXH_PUBLIC_API XXH_errorcode  XXH32_freeState(XXH32_state_t* statePtr);
+XXH_PUBLIC_API void XXH32_copyState(XXH32_state_t* dst_state, const XXH32_state_t* src_state);
+
+XXH_PUBLIC_API XXH_errorcode XXH32_reset  (XXH32_state_t* statePtr, XXH32_hash_t seed);
+XXH_PUBLIC_API XXH_errorcode XXH32_update (XXH32_state_t* statePtr, const void* input, size_t length);
+XXH_PUBLIC_API XXH32_hash_t  XXH32_digest (const XXH32_state_t* statePtr);
+
+/*======   Canonical representation   ======*/
+
+/* Default return values from XXH functions are basic unsigned 32 and 64 bits.
+ * This the simplest and fastest format for further post-processing.
+ * However, this leaves open the question of what is the order of bytes,
+ * since little and big endian conventions will write the same number differently.
+ *
+ * The canonical representation settles this issue,
+ * by mandating big-endian convention,
+ * aka, the same convention as human-readable numbers (large digits first).
+ * When writing hash values to storage, sending them over a network, or printing them,
+ * it's highly recommended to use the canonical representation,
+ * to ensure portability across a wider range of systems, present and future.
+ *
+ * The following functions allow transformation of hash values into and from canonical format.
+ */
+
+typedef struct { unsigned char digest[4]; } XXH32_canonical_t;
+XXH_PUBLIC_API void XXH32_canonicalFromHash(XXH32_canonical_t* dst, XXH32_hash_t hash);
+XXH_PUBLIC_API XXH32_hash_t XXH32_hashFromCanonical(const XXH32_canonical_t* src);
+
+
+#ifndef XXH_NO_LONG_LONG
+/*-**********************************************************************
+*  64-bit hash
+************************************************************************/
+#if !defined (__VMS) \
+  && (defined (__cplusplus) \
+  || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
+#   include <stdint.h>
+    typedef uint64_t XXH64_hash_t;
+#else
+    /* the following type must have a width of 64-bit */
+    typedef unsigned long long XXH64_hash_t;
+#endif
+
+/*! XXH64() :
+    Calculate the 64-bit hash of sequence of length "len" stored at memory address "input".
+    "seed" can be used to alter the result predictably.
+    This function runs faster on 64-bit systems, but slower on 32-bit systems (see benchmark).
+*/
+XXH_PUBLIC_API XXH64_hash_t XXH64 (const void* input, size_t length, XXH64_hash_t seed);
+
+/*======   Streaming   ======*/
+typedef struct XXH64_state_s XXH64_state_t;   /* incomplete type */
+XXH_PUBLIC_API XXH64_state_t* XXH64_createState(void);
+XXH_PUBLIC_API XXH_errorcode  XXH64_freeState(XXH64_state_t* statePtr);
+XXH_PUBLIC_API void XXH64_copyState(XXH64_state_t* dst_state, const XXH64_state_t* src_state);
+
+XXH_PUBLIC_API XXH_errorcode XXH64_reset  (XXH64_state_t* statePtr, XXH64_hash_t seed);
+XXH_PUBLIC_API XXH_errorcode XXH64_update (XXH64_state_t* statePtr, const void* input, size_t length);
+XXH_PUBLIC_API XXH64_hash_t  XXH64_digest (const XXH64_state_t* statePtr);
+
+/*======   Canonical representation   ======*/
+typedef struct { unsigned char digest[8]; } XXH64_canonical_t;
+XXH_PUBLIC_API void XXH64_canonicalFromHash(XXH64_canonical_t* dst, XXH64_hash_t hash);
+XXH_PUBLIC_API XXH64_hash_t XXH64_hashFromCanonical(const XXH64_canonical_t* src);
+
+
+#endif  /* XXH_NO_LONG_LONG */
+
+
+
+#ifdef XXH_STATIC_LINKING_ONLY
+
+/* ================================================================================================
+   This section contains declarations which are not guaranteed to remain stable.
+   They may change in future versions, becoming incompatible with a different version of the library.
+   These declarations should only be used with static linking.
+   Never use them in association with dynamic linking !
+=================================================================================================== */
+
+/* These definitions are only present to allow
+ * static allocation of XXH state, on stack or in a struct for example.
+ * Never **ever** use members directly. */
+
+struct XXH32_state_s {
+   XXH32_hash_t total_len_32;
+   XXH32_hash_t large_len;
+   XXH32_hash_t v1;
+   XXH32_hash_t v2;
+   XXH32_hash_t v3;
+   XXH32_hash_t v4;
+   XXH32_hash_t mem32[4];
+   XXH32_hash_t memsize;
+   XXH32_hash_t reserved;   /* never read nor write, might be removed in a future version */
+};   /* typedef'd to XXH32_state_t */
+
+#ifndef XXH_NO_LONG_LONG  /* remove 64-bit support */
+struct XXH64_state_s {
+   XXH64_hash_t total_len;
+   XXH64_hash_t v1;
+   XXH64_hash_t v2;
+   XXH64_hash_t v3;
+   XXH64_hash_t v4;
+   XXH64_hash_t mem64[4];
+   XXH32_hash_t memsize;
+   XXH32_hash_t reserved32;  /* required for padding anyway */
+   XXH64_hash_t reserved64;  /* never read nor write, might be removed in a future version */
+};   /* typedef'd to XXH64_state_t */
+#endif   /* XXH_NO_LONG_LONG */
+
+
+/*-**********************************************************************
+*  XXH3
+*  New experimental hash
+************************************************************************/
+#ifndef XXH_NO_LONG_LONG
+
+
+/* ============================================
+ * XXH3 is a new hash algorithm,
+ * featuring improved speed performance for both small and large inputs.
+ * See full speed analysis at : http://fastcompression.blogspot.com/2019/03/presenting-xxh3.html
+ * In general, expect XXH3 to run about ~2x faster on large inputs,
+ * and >3x faster on small ones, though exact differences depend on platform.
+ *
+ * The algorithm is portable, will generate the same hash on all platforms.
+ * It benefits greatly from vectorization units, but does not require it.
+ *
+ * XXH3 offers 2 variants, _64bits and _128bits.
+ * When only 64 bits are needed, prefer calling the _64bits variant :
+ * it reduces the amount of mixing, resulting in faster speed on small inputs.
+ * It's also generally simpler to manipulate a scalar return type than a struct.
+ *
+ * The XXH3 algorithm is still considered experimental.
+ * Produced results can still change between versions.
+ * Results produced by v0.7.x are not comparable with results from v0.7.y .
+ * It's nonetheless possible to use XXH3 for ephemeral data (local sessions),
+ * but avoid storing values in long-term storage for later reads.
+ *
+ * The API supports one-shot hashing, streaming mode, and custom secrets.
+ *
+ * There are still a number of opened questions that community can influence during the experimental period.
+ * I'm trying to list a few of them below, though don't consider this list as complete.
+ *
+ * - 128-bits output type : currently defined as a structure of two 64-bits fields.
+ *                          That's because 128-bit values do not exist in C standard.
+ *                          Note that it means that, at byte level, result is not identical depending on endianess.
+ *                          However, at field level, they are identical on all platforms.
+ *                          The canonical representation solves the issue of identical byte-level representation across platforms,
+ *                          which is necessary for serialization.
+ *                          Q1 : Would there be a better representation for a 128-bit hash result ?
+ *                          Q2 : Are the names of the inner 64-bit fields important ? Should they be changed ?
+ *
+ * - Prototype XXH128() :   XXH128() uses the same arguments as XXH64(), for consistency.
+ *                          It means it maps to XXH3p_128bits_withSeed().
+ *                          This variant is slightly slower than XXH3p_128bits(),
+ *                          because the seed is now part of the algorithm, and can't be simplified.
+ *                          Is that a good idea ?
+ *
+ * - Seed type for XXH128() : currently, it's a single 64-bit value, like the 64-bit variant.
+ *                          It could be argued that it's more logical to offer a 128-bit seed input parameter for a 128-bit hash.
+ *                          But 128-bit seed is more difficult to use, since it requires to pass a structure instead of a scalar value.
+ *                          Such a variant could either replace current one, or become an additional one.
+ *                          Farmhash, for example, offers both variants (the 128-bits seed variant is called `doubleSeed`).
+ *                          Follow up question : if both 64-bit and 128-bit seeds are allowed, which variant should be called XXH128 ?
+ *
+ * - Result for len==0 :    Currently, the result of hashing a zero-length input is always `0`.
+ *                          It seems okay as a return value when using "default" secret and seed.
+ *                          But is it still fine to return `0` when secret or seed are non-default ?
+ *                          Are there use cases which could depend on generating a different hash result for zero-length input when the secret is different ?
+ *
+ * - Consistency (1) :      Streaming XXH128 uses an XXH3 state, which is the same state as XXH3p_64bits().
+ *                          It means a 128bit streaming loop must invoke the following symbols :
+ *                          XXH3p_createState(), XXH3p_128bits_reset(), XXH3p_128bits_update() (loop), XXH3p_128bits_digest(), XXH3p_freeState().
+ *                          Is that consistent enough ?
+ *
+ * - Consistency (2) :      The canonical representation of `XXH3p_64bits` is provided by existing functions
+ *                          XXH64_canonicalFromHash(), and reverse operation XXH64_hashFromCanonical().
+ *                          As a mirror, canonical functions for XXH128_hash_t results generated by `XXH3p_128bits`
+ *                          are XXH128_canonicalFromHash() and XXH128_hashFromCanonical().
+ *                          Which means, `XXH3` doesn't appear in the names, because canonical functions operate on a type,
+ *                          independently of which algorithm was used to generate that type.
+ *                          Is that consistent enough ?
+ */
+
+#ifdef XXH_NAMESPACE
+#  define XXH3p_64bits XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits)
+#  define XXH3p_64bits_withSecret XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_withSecret)
+#  define XXH3p_64bits_withSeed XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_withSeed)
+
+#  define XXH3p_createState XXH_NAME2(XXH_NAMESPACE, XXH3p_createState)
+#  define XXH3p_freeState XXH_NAME2(XXH_NAMESPACE, XXH3p_freeState)
+#  define XXH3p_copyState XXH_NAME2(XXH_NAMESPACE, XXH3p_copyState)
+
+#  define XXH3p_64bits_reset XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_reset)
+#  define XXH3p_64bits_reset_withSeed XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_reset_withSeed)
+#  define XXH3p_64bits_reset_withSecret XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_reset_withSecret)
+#  define XXH3p_64bits_update XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_update)
+#  define XXH3p_64bits_digest XXH_NAME2(XXH_NAMESPACE, XXH3p_64bits_digest)
+#endif
+
+/* XXH3p_64bits() :
+ * default 64-bit variant, using default secret and default seed of 0.
+ * It's the fastest variant. */
+XXH_PUBLIC_API XXH64_hash_t XXH3p_64bits(const void* data, size_t len);
+
+/* XXH3p_64bits_withSecret() :
+ * It's possible to provide any blob of bytes as a "secret" to generate the hash.
+ * This makes it more difficult for an external actor to prepare an intentional collision.
+ * The secret *must* be large enough (>= XXH3p_SECRET_SIZE_MIN).
+ * It should consist of random bytes.
+ * Avoid repeating same character, or sequences of bytes,
+ * and especially avoid swathes of \0.
+ * Failure to respect these conditions will result in a poor quality hash.
+ */
+#define XXH3p_SECRET_SIZE_MIN 136
+XXH_PUBLIC_API XXH64_hash_t XXH3p_64bits_withSecret(const void* data, size_t len, const void* secret, size_t secretSize);
+
+/* XXH3p_64bits_withSeed() :
+ * This variant generates on the fly a custom secret,
+ * based on the default secret, altered using the `seed` value.
+ * While this operation is decently fast, note that it's not completely free.
+ * note : seed==0 produces same results as XXH3p_64bits() */
+XXH_PUBLIC_API XXH64_hash_t XXH3p_64bits_withSeed(const void* data, size_t len, XXH64_hash_t seed);
+
+
+/* streaming 64-bit */
+
+#if defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)   /* C11+ */
+#  include <stdalign.h>
+#  define XXH_ALIGN(n)      alignas(n)
+#elif defined(__GNUC__)
+#  define XXH_ALIGN(n)      __attribute__ ((aligned(n)))
+#elif defined(_MSC_VER)
+#  define XXH_ALIGN(n)      __declspec(align(n))
+#else
+#  define XXH_ALIGN(n)   /* disabled */
+#endif
+
+typedef struct XXH3p_state_s XXH3p_state_t;
+
+#define XXH3p_SECRET_DEFAULT_SIZE 192   /* minimum XXH3p_SECRET_SIZE_MIN */
+#define XXH3p_INTERNALBUFFER_SIZE 256
+struct XXH3p_state_s {
+   XXH_ALIGN(64) XXH64_hash_t acc[8];
+   XXH_ALIGN(64) unsigned char customSecret[XXH3p_SECRET_DEFAULT_SIZE];  /* used to store a custom secret generated from the seed. Makes state larger. Design might change */
+   XXH_ALIGN(64) unsigned char buffer[XXH3p_INTERNALBUFFER_SIZE];
+   XXH32_hash_t bufferedSize;
+   XXH32_hash_t nbStripesPerBlock;
+   XXH32_hash_t nbStripesSoFar;
+   XXH32_hash_t secretLimit;
+   XXH32_hash_t reserved32;
+   XXH32_hash_t reserved32_2;
+   XXH64_hash_t totalLen;
+   XXH64_hash_t seed;
+   XXH64_hash_t reserved64;
+   const unsigned char* secret;    /* note : there is some padding after, due to alignment on 64 bytes */
+};   /* typedef'd to XXH3p_state_t */
+
+/* Streaming requires state maintenance.
+ * This operation costs memory and cpu.
+ * As a consequence, streaming is slower than one-shot hashing.
+ * For better performance, prefer using one-shot functions whenever possible. */
+
+XXH_PUBLIC_API XXH3p_state_t* XXH3p_createState(void);
+XXH_PUBLIC_API XXH_errorcode XXH3p_freeState(XXH3p_state_t* statePtr);
+XXH_PUBLIC_API void XXH3p_copyState(XXH3p_state_t* dst_state, const XXH3p_state_t* src_state);
+
+
+/* XXH3p_64bits_reset() :
+ * initialize with default parameters.
+ * result will be equivalent to `XXH3p_64bits()`. */
+XXH_PUBLIC_API XXH_errorcode XXH3p_64bits_reset(XXH3p_state_t* statePtr);
+/* XXH3p_64bits_reset_withSeed() :
+ * generate a custom secret from `seed`, and store it into state.
+ * digest will be equivalent to `XXH3p_64bits_withSeed()`. */
+XXH_PUBLIC_API XXH_errorcode XXH3p_64bits_reset_withSeed(XXH3p_state_t* statePtr, XXH64_hash_t seed);
+/* XXH3p_64bits_reset_withSecret() :
+ * `secret` is referenced, and must outlive the hash streaming session.
+ * secretSize must be >= XXH3p_SECRET_SIZE_MIN.
+ */
+XXH_PUBLIC_API XXH_errorcode XXH3p_64bits_reset_withSecret(XXH3p_state_t* statePtr, const void* secret, size_t secretSize);
+
+XXH_PUBLIC_API XXH_errorcode XXH3p_64bits_update (XXH3p_state_t* statePtr, const void* input, size_t length);
+XXH_PUBLIC_API XXH64_hash_t  XXH3p_64bits_digest (const XXH3p_state_t* statePtr);
+
+
+/* 128-bit */
+
+#ifdef XXH_NAMESPACE
+#  define XXH128 XXH_NAME2(XXH_NAMESPACE, XXH128)
+#  define XXH3p_128bits XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits)
+#  define XXH3p_128bits_withSeed XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_withSeed)
+#  define XXH3p_128bits_withSecret XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_withSecret)
+
+#  define XXH3p_128bits_reset XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_reset)
+#  define XXH3p_128bits_reset_withSeed XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_reset_withSeed)
+#  define XXH3p_128bits_reset_withSecret XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_reset_withSecret)
+#  define XXH3p_128bits_update XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_update)
+#  define XXH3p_128bits_digest XXH_NAME2(XXH_NAMESPACE, XXH3p_128bits_digest)
+
+#  define XXH128_isEqual XXH_NAME2(XXH_NAMESPACE, XXH128_isEqual)
+#  define XXH128_cmp     XXH_NAME2(XXH_NAMESPACE, XXH128_cmp)
+#  define XXH128_canonicalFromHash XXH_NAME2(XXH_NAMESPACE, XXH128_canonicalFromHash)
+#  define XXH128_hashFromCanonical XXH_NAME2(XXH_NAMESPACE, XXH128_hashFromCanonical)
+#endif
+
+typedef struct {
+    XXH64_hash_t low64;
+    XXH64_hash_t high64;
+} XXH128_hash_t;
+
+XXH_PUBLIC_API XXH128_hash_t XXH128(const void* data, size_t len, XXH64_hash_t seed);
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits(const void* data, size_t len);
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits_withSeed(const void* data, size_t len, XXH64_hash_t seed);  /* == XXH128() */
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits_withSecret(const void* data, size_t len, const void* secret, size_t secretSize);
+
+XXH_PUBLIC_API XXH_errorcode XXH3p_128bits_reset(XXH3p_state_t* statePtr);
+XXH_PUBLIC_API XXH_errorcode XXH3p_128bits_reset_withSeed(XXH3p_state_t* statePtr, XXH64_hash_t seed);
+XXH_PUBLIC_API XXH_errorcode XXH3p_128bits_reset_withSecret(XXH3p_state_t* statePtr, const void* secret, size_t secretSize);
+
+XXH_PUBLIC_API XXH_errorcode XXH3p_128bits_update (XXH3p_state_t* statePtr, const void* input, size_t length);
+XXH_PUBLIC_API XXH128_hash_t XXH3p_128bits_digest (const XXH3p_state_t* statePtr);
+
+
+/* Note : for better performance, following functions can be inlined,
+ * using XXH_INLINE_ALL */
+
+/* return : 1 is equal, 0 if different */
+XXH_PUBLIC_API int XXH128_isEqual(XXH128_hash_t h1, XXH128_hash_t h2);
+
+/* This comparator is compatible with stdlib's qsort().
+ * return : >0 if *h128_1  > *h128_2
+ *          <0 if *h128_1  < *h128_2
+ *          =0 if *h128_1 == *h128_2  */
+XXH_PUBLIC_API int XXH128_cmp(const void* h128_1, const void* h128_2);
+
+
+/*======   Canonical representation   ======*/
+typedef struct { unsigned char digest[16]; } XXH128_canonical_t;
+XXH_PUBLIC_API void XXH128_canonicalFromHash(XXH128_canonical_t* dst, XXH128_hash_t hash);
+XXH_PUBLIC_API XXH128_hash_t XXH128_hashFromCanonical(const XXH128_canonical_t* src);
+
+
+#endif  /* XXH_NO_LONG_LONG */
+
+
+/*-**********************************************************************
+*  XXH_INLINE_ALL
+************************************************************************/
+#if defined(XXH_INLINE_ALL) || defined(XXH_PRIVATE_API)
+#  include "xxhash.cc"   /* include xxhash function bodies as `static`, for inlining */
+#endif
+
+
+
+#endif /* XXH_STATIC_LINKING_ONLY */
+
+
+#if defined (__cplusplus)
+}
+#endif
+
+#endif /* XXHASH_H_5627135585666179 */