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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/rocksdb/cache/cache_helpers.h | |
parent | Initial commit. (diff) | |
download | ceph-upstream/18.2.2.tar.xz ceph-upstream/18.2.2.zip |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/rocksdb/cache/cache_helpers.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/src/rocksdb/cache/cache_helpers.h b/src/rocksdb/cache/cache_helpers.h new file mode 100644 index 000000000..7ea2365b8 --- /dev/null +++ b/src/rocksdb/cache/cache_helpers.h @@ -0,0 +1,145 @@ +// 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 "rocksdb/cache.h" +#include "rocksdb/rocksdb_namespace.h" + +namespace ROCKSDB_NAMESPACE { + +// Returns the cached value given a cache handle. +template <typename T> +T* GetFromCacheHandle(Cache* cache, Cache::Handle* handle) { + assert(cache); + assert(handle); + + return static_cast<T*>(cache->Value(handle)); +} + +// Simple generic deleter for Cache (to be used with Cache::Insert). +template <typename T> +void DeleteCacheEntry(const Slice& /* key */, void* value) { + delete static_cast<T*>(value); +} + +// Turns a T* into a Slice so it can be used as a key with Cache. +template <typename T> +Slice GetSlice(const T* t) { + return Slice(reinterpret_cast<const char*>(t), sizeof(T)); +} + +// Generic resource management object for cache handles that releases the handle +// when destroyed. Has unique ownership of the handle, so copying it is not +// allowed, while moving it transfers ownership. +template <typename T> +class CacheHandleGuard { + public: + CacheHandleGuard() = default; + + CacheHandleGuard(Cache* cache, Cache::Handle* handle) + : cache_(cache), + handle_(handle), + value_(GetFromCacheHandle<T>(cache, handle)) { + assert(cache_ && handle_ && value_); + } + + CacheHandleGuard(const CacheHandleGuard&) = delete; + CacheHandleGuard& operator=(const CacheHandleGuard&) = delete; + + CacheHandleGuard(CacheHandleGuard&& rhs) noexcept + : cache_(rhs.cache_), handle_(rhs.handle_), value_(rhs.value_) { + assert((!cache_ && !handle_ && !value_) || (cache_ && handle_ && value_)); + + rhs.ResetFields(); + } + + CacheHandleGuard& operator=(CacheHandleGuard&& rhs) noexcept { + if (this == &rhs) { + return *this; + } + + ReleaseHandle(); + + cache_ = rhs.cache_; + handle_ = rhs.handle_; + value_ = rhs.value_; + + assert((!cache_ && !handle_ && !value_) || (cache_ && handle_ && value_)); + + rhs.ResetFields(); + + return *this; + } + + ~CacheHandleGuard() { ReleaseHandle(); } + + bool IsEmpty() const { return !handle_; } + + Cache* GetCache() const { return cache_; } + Cache::Handle* GetCacheHandle() const { return handle_; } + T* GetValue() const { return value_; } + + void TransferTo(Cleanable* cleanable) { + if (cleanable) { + if (handle_ != nullptr) { + assert(cache_); + cleanable->RegisterCleanup(&ReleaseCacheHandle, cache_, handle_); + } + } + ResetFields(); + } + + void Reset() { + ReleaseHandle(); + ResetFields(); + } + + private: + void ReleaseHandle() { + if (IsEmpty()) { + return; + } + + assert(cache_); + cache_->Release(handle_); + } + + void ResetFields() { + cache_ = nullptr; + handle_ = nullptr; + value_ = nullptr; + } + + 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); + } + + private: + Cache* cache_ = nullptr; + Cache::Handle* handle_ = nullptr; + T* value_ = nullptr; +}; + +// Build an aliasing shared_ptr that keeps `handle` in cache while there +// are references, but the pointer is to the value for that cache entry, +// which must be of type T. This is copyable, unlike CacheHandleGuard, but +// does not provide access to caching details. +template <typename T> +std::shared_ptr<T> MakeSharedCacheHandleGuard(Cache* cache, + Cache::Handle* handle) { + auto wrapper = std::make_shared<CacheHandleGuard<T>>(cache, handle); + return std::shared_ptr<T>(wrapper, static_cast<T*>(cache->Value(handle))); +} + +} // namespace ROCKSDB_NAMESPACE |