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Diffstat (limited to 'src/leveldb/include/leveldb/cache.h')
-rw-r--r-- | src/leveldb/include/leveldb/cache.h | 99 |
1 files changed, 0 insertions, 99 deletions
diff --git a/src/leveldb/include/leveldb/cache.h b/src/leveldb/include/leveldb/cache.h deleted file mode 100644 index 5e3b47637..000000000 --- a/src/leveldb/include/leveldb/cache.h +++ /dev/null @@ -1,99 +0,0 @@ -// 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 Cache is an interface that maps keys to values. It has internal -// synchronization and may be safely accessed concurrently from -// multiple threads. It may automatically evict entries to make room -// for new entries. Values have a specified charge against the cache -// capacity. For example, a cache where the values are variable -// length strings, may use the length of the string as the charge for -// the string. -// -// A builtin cache implementation with a least-recently-used eviction -// policy is provided. Clients may use their own implementations if -// they want something more sophisticated (like scan-resistance, a -// custom eviction policy, variable cache sizing, etc.) - -#ifndef STORAGE_LEVELDB_INCLUDE_CACHE_H_ -#define STORAGE_LEVELDB_INCLUDE_CACHE_H_ - -#include <stdint.h> -#include "leveldb/slice.h" - -namespace leveldb { - -class Cache; - -// Create a new cache with a fixed size capacity. This implementation -// of Cache uses a least-recently-used eviction policy. -extern Cache* NewLRUCache(size_t capacity); - -class Cache { - public: - Cache() { } - - // Destroys all existing entries by calling the "deleter" - // function that was passed to the constructor. - virtual ~Cache(); - - // Opaque handle to an entry stored in the cache. - struct Handle { }; - - // Insert a mapping from key->value into the cache and assign it - // the specified charge against the total cache capacity. - // - // Returns a handle that corresponds to the mapping. The caller - // must call this->Release(handle) when the returned mapping is no - // longer needed. - // - // When the inserted entry is no longer needed, the key and - // value will be passed to "deleter". - virtual Handle* Insert(const Slice& key, void* value, size_t charge, - void (*deleter)(const Slice& key, void* value)) = 0; - - // If the cache has no mapping for "key", returns NULL. - // - // Else return a handle that corresponds to the mapping. The caller - // must call this->Release(handle) when the returned mapping is no - // longer needed. - virtual Handle* Lookup(const Slice& key) = 0; - - // Release a mapping returned by a previous Lookup(). - // REQUIRES: handle must not have been released yet. - // REQUIRES: handle must have been returned by a method on *this. - virtual void Release(Handle* handle) = 0; - - // Return the value encapsulated in a handle returned by a - // successful Lookup(). - // REQUIRES: handle must not have been released yet. - // REQUIRES: handle must have been returned by a method on *this. - virtual void* Value(Handle* handle) = 0; - - // If the cache contains entry for key, erase it. Note that the - // underlying entry will be kept around until all existing handles - // to it have been released. - virtual void Erase(const Slice& key) = 0; - - // Return a new numeric id. May be used by multiple clients who are - // sharing the same cache to partition the key space. Typically the - // client will allocate a new id at startup and prepend the id to - // its cache keys. - virtual uint64_t NewId() = 0; - - private: - void LRU_Remove(Handle* e); - void LRU_Append(Handle* e); - void Unref(Handle* e); - - struct Rep; - Rep* rep_; - - // No copying allowed - Cache(const Cache&); - void operator=(const Cache&); -}; - -} // namespace leveldb - -#endif // STORAGE_LEVELDB_UTIL_CACHE_H_ |