Adding upstream version 18.2.2.upstream/18.2.2

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

1 files changed, 232 insertions, 0 deletions

diff --git a/src/rocksdb/table/block_based/cachable_entry.h b/src/rocksdb/table/block_based/cachable_entry.h
new file mode 100644
index 000000000..ad8acb18d
--- /dev/null
+++ b/src/rocksdb/table/block_based/cachable_entry.h
@@ -0,0 +1,232 @@
+//  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.
+
+#pragma once
+
+#include <cassert>
+
+#include "port/likely.h"
+#include "rocksdb/cache.h"
+#include "rocksdb/cleanable.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// CachableEntry is a handle to an object that may or may not be in the block
+// cache. It is used in a variety of ways:
+//
+// 1) It may refer to an object in the block cache. In this case, cache_ and
+// cache_handle_ are not nullptr, and the cache handle has to be released when
+// the CachableEntry is destroyed (the lifecycle of the cached object, on the
+// other hand, is managed by the cache itself).
+// 2) It may uniquely own the (non-cached) object it refers to (examples include
+// a block read directly from file, or uncompressed blocks when there is a
+// compressed block cache but no uncompressed block cache). In such cases, the
+// object has to be destroyed when the CachableEntry is destroyed.
+// 3) It may point to an object (cached or not) without owning it. In this case,
+// no action is needed when the CachableEntry is destroyed.
+// 4) Sometimes, management of a cached or owned object (see #1 and #2 above)
+// is transferred to some other object. This is used for instance with iterators
+// (where cleanup is performed using a chain of cleanup functions,
+// see Cleanable).
+//
+// Because of #1 and #2 above, copying a CachableEntry is not safe (and thus not
+// allowed); hence, this is a move-only type, where a move transfers the
+// management responsibilities, and leaves the source object in an empty state.
+
+template <class T>
+class CachableEntry {
+ public:
+  CachableEntry() = default;
+
+  CachableEntry(T* value, Cache* cache, Cache::Handle* cache_handle,
+                bool own_value)
+      : value_(value),
+        cache_(cache),
+        cache_handle_(cache_handle),
+        own_value_(own_value) {
+    assert(value_ != nullptr ||
+           (cache_ == nullptr && cache_handle_ == nullptr && !own_value_));
+    assert(!!cache_ == !!cache_handle_);
+    assert(!cache_handle_ || !own_value_);
+  }
+
+  CachableEntry(const CachableEntry&) = delete;
+  CachableEntry& operator=(const CachableEntry&) = delete;
+
+  CachableEntry(CachableEntry&& rhs) noexcept
+      : value_(rhs.value_),
+        cache_(rhs.cache_),
+        cache_handle_(rhs.cache_handle_),
+        own_value_(rhs.own_value_) {
+    assert(value_ != nullptr ||
+           (cache_ == nullptr && cache_handle_ == nullptr && !own_value_));
+    assert(!!cache_ == !!cache_handle_);
+    assert(!cache_handle_ || !own_value_);
+
+    rhs.ResetFields();
+  }
+
+  CachableEntry& operator=(CachableEntry&& rhs) noexcept {
+    if (UNLIKELY(this == &rhs)) {
+      return *this;
+    }
+
+    ReleaseResource();
+
+    value_ = rhs.value_;
+    cache_ = rhs.cache_;
+    cache_handle_ = rhs.cache_handle_;
+    own_value_ = rhs.own_value_;
+
+    assert(value_ != nullptr ||
+           (cache_ == nullptr && cache_handle_ == nullptr && !own_value_));
+    assert(!!cache_ == !!cache_handle_);
+    assert(!cache_handle_ || !own_value_);
+
+    rhs.ResetFields();
+
+    return *this;
+  }
+
+  ~CachableEntry() { ReleaseResource(); }
+
+  bool IsEmpty() const {
+    return value_ == nullptr && cache_ == nullptr && cache_handle_ == nullptr &&
+           !own_value_;
+  }
+
+  bool IsCached() const {
+    assert(!!cache_ == !!cache_handle_);
+
+    return cache_handle_ != nullptr;
+  }
+
+  T* GetValue() const { return value_; }
+  Cache* GetCache() const { return cache_; }
+  Cache::Handle* GetCacheHandle() const { return cache_handle_; }
+  bool GetOwnValue() const { return own_value_; }
+
+  void Reset() {
+    ReleaseResource();
+    ResetFields();
+  }
+
+  void TransferTo(Cleanable* cleanable) {
+    if (cleanable) {
+      if (cache_handle_ != nullptr) {
+        assert(cache_ != nullptr);
+        cleanable->RegisterCleanup(&ReleaseCacheHandle, cache_, cache_handle_);
+      } else if (own_value_) {
+        cleanable->RegisterCleanup(&DeleteValue, value_, nullptr);
+      }
+    }
+
+    ResetFields();
+  }
+
+  void SetOwnedValue(std::unique_ptr<T>&& value) {
+    assert(value.get() != nullptr);
+
+    if (UNLIKELY(value_ == value.get() && own_value_)) {
+      assert(cache_ == nullptr && cache_handle_ == nullptr);
+      return;
+    }
+
+    Reset();
+
+    value_ = value.release();
+    own_value_ = true;
+  }
+
+  void SetUnownedValue(T* value) {
+    assert(value != nullptr);
+
+    if (UNLIKELY(value_ == value && cache_ == nullptr &&
+                 cache_handle_ == nullptr && !own_value_)) {
+      return;
+    }
+
+    Reset();
+
+    value_ = value;
+    assert(!own_value_);
+  }
+
+  void SetCachedValue(T* value, Cache* cache, Cache::Handle* cache_handle) {
+    assert(cache != nullptr);
+    assert(cache_handle != nullptr);
+
+    if (UNLIKELY(value_ == value && cache_ == cache &&
+                 cache_handle_ == cache_handle && !own_value_)) {
+      return;
+    }
+
+    Reset();
+
+    value_ = value;
+    cache_ = cache;
+    cache_handle_ = cache_handle;
+    assert(!own_value_);
+  }
+
+  void UpdateCachedValue() {
+    assert(cache_ != nullptr);
+    assert(cache_handle_ != nullptr);
+
+    value_ = static_cast<T*>(cache_->Value(cache_handle_));
+  }
+
+  bool IsReady() {
+    if (!own_value_) {
+      assert(cache_ != nullptr);
+      assert(cache_handle_ != nullptr);
+      return cache_->IsReady(cache_handle_);
+    }
+    return true;
+  }
+
+ private:
+  void ReleaseResource() noexcept {
+    if (LIKELY(cache_handle_ != nullptr)) {
+      assert(cache_ != nullptr);
+      cache_->Release(cache_handle_);
+    } else if (own_value_) {
+      delete value_;
+    }
+  }
+
+  void ResetFields() noexcept {
+    value_ = nullptr;
+    cache_ = nullptr;
+    cache_handle_ = nullptr;
+    own_value_ = false;
+  }
+
+  static void ReleaseCacheHandle(void* arg1, void* arg2) {
+    Cache* const cache = static_cast<Cache*>(arg1);
+    assert(cache);
+
+    Cache::Handle* const cache_handle = static_cast<Cache::Handle*>(arg2);
+    assert(cache_handle);
+
+    cache->Release(cache_handle);
+  }
+
+  static void DeleteValue(void* arg1, void* /* arg2 */) {
+    delete static_cast<T*>(arg1);
+  }
+
+ private:
+  T* value_ = nullptr;
+  Cache* cache_ = nullptr;
+  Cache::Handle* cache_handle_ = nullptr;
+  bool own_value_ = false;
+};
+
+}  // namespace ROCKSDB_NAMESPACE