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diff --git a/src/rocksdb/util/hash.h b/src/rocksdb/util/hash.h
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+//  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
+// XXH3_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 <cstddef>
+#include <cstdint>
+
+#include "rocksdb/slice.h"
+#include "util/fastrange.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Stable/persistent 64-bit hash. Higher quality and generally faster than
+// Hash(), especially for inputs > 24 bytes.
+// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
+// results from previous seed. Recommend incrementing by a large odd number.
+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 structures.
+// The hash results are thus subject to change between releases,
+// architectures, build configuration, etc. (Thus, it rarely makes sense
+// to specify a seed for this function, except for a "rolling" hash.)
+// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
+// results from previous seed. Recommend incrementing by a large odd number.
+inline uint64_t NPHash64(const char* data, size_t n, uint64_t seed) {
+#ifdef ROCKSDB_MODIFY_NPHASH
+  // For testing "subject to change"
+  return Hash64(data, n, seed + 123456789);
+#else
+  // Currently same as Hash64
+  return Hash64(data, n, seed);
+#endif
+}
+
+// Specific optimization without seed (same as seed = 0)
+inline uint64_t NPHash64(const char* data, size_t n) {
+#ifdef ROCKSDB_MODIFY_NPHASH
+  // For testing "subject to change"
+  return Hash64(data, n, 123456789);
+#else
+  // Currently same as Hash64
+  return Hash64(data, n);
+#endif
+}
+
+// Convenient and equivalent version of Hash128 without depending on 128-bit
+// scalars
+void Hash2x64(const char* data, size_t n, uint64_t* high64, uint64_t* low64);
+void Hash2x64(const char* data, size_t n, uint64_t seed, uint64_t* high64,
+              uint64_t* low64);
+
+// Hash 128 bits to 128 bits, guaranteed not to lose data (equivalent to
+// Hash2x64 on 16 bytes little endian)
+void BijectiveHash2x64(uint64_t in_high64, uint64_t in_low64,
+                       uint64_t* out_high64, uint64_t* out_low64);
+void BijectiveHash2x64(uint64_t in_high64, uint64_t in_low64, uint64_t seed,
+                       uint64_t* out_high64, uint64_t* out_low64);
+
+// Inverse of above (mostly for testing)
+void BijectiveUnhash2x64(uint64_t in_high64, uint64_t in_low64,
+                         uint64_t* out_high64, uint64_t* out_low64);
+void BijectiveUnhash2x64(uint64_t in_high64, uint64_t in_low64, uint64_t seed,
+                         uint64_t* out_high64, uint64_t* out_low64);
+
+// Stable/persistent 32-bit hash. Moderate quality and high speed on
+// small inputs.
+// TODO: consider rename to Hash32
+// KNOWN FLAW: incrementing seed by 1 might not give sufficiently independent
+// results from previous seed. Recommend pseudorandom or hashed seeds.
+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());
+}
+// Provided for convenience for use with template argument deduction, where a
+// specific overload needs to be used.
+extern uint64_t (*kGetSliceNPHash64UnseededFnPtr)(const Slice&);
+
+inline uint64_t GetSliceNPHash64(const Slice& s) {
+  return NPHash64(s.data(), s.size());
+}
+
+inline uint64_t GetSliceNPHash64(const Slice& s, uint64_t seed) {
+  return NPHash64(s.data(), s.size(), seed);
+}
+
+// Similar to `GetSliceNPHash64()` with `seed`, but input comes from
+// concatenation of `Slice`s in `data`.
+extern uint64_t GetSlicePartsNPHash64(const SliceParts& data, uint64_t seed);
+
+inline size_t GetSliceRangedNPHash(const Slice& s, size_t range) {
+  return FastRange64(NPHash64(s.data(), s.size()), range);
+}
+
+// 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); }
+};
+
+}  // namespace ROCKSDB_NAMESPACE