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// Copyright (c) 2012 The Chromium 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 net/disk_cache/disk_cache.h for the public interface of the cache.
#ifndef NET_DISK_CACHE_MEMORY_MEM_BACKEND_IMPL_H_
#define NET_DISK_CACHE_MEMORY_MEM_BACKEND_IMPL_H_
#include <stdint.h>
#include <string>
#include <unordered_map>
#include "base/callback_forward.h"
#include "base/compiler_specific.h"
#include "base/containers/linked_list.h"
#include "base/macros.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/weak_ptr.h"
#include "base/strings/string_split.h"
#include "base/time/time.h"
#include "net/base/net_export.h"
#include "net/disk_cache/disk_cache.h"
#include "net/disk_cache/memory/mem_entry_impl.h"
namespace base {
class Clock;
}
namespace net {
class NetLog;
} // namespace net
namespace disk_cache {
// This class implements the Backend interface. An object of this class handles
// the operations of the cache without writing to disk.
class NET_EXPORT_PRIVATE MemBackendImpl final : public Backend {
public:
explicit MemBackendImpl(net::NetLog* net_log);
~MemBackendImpl() override;
// Returns an instance of a Backend implemented only in memory. The returned
// object should be deleted when not needed anymore. max_bytes is the maximum
// size the cache can grow to. If zero is passed in as max_bytes, the cache
// will determine the value to use based on the available memory. The returned
// pointer can be NULL if a fatal error is found.
static std::unique_ptr<MemBackendImpl> CreateBackend(int64_t max_bytes,
net::NetLog* net_log);
// Performs general initialization for this current instance of the cache.
bool Init();
// Sets the maximum size for the total amount of data stored by this instance.
bool SetMaxSize(int64_t max_bytes);
// Returns the maximum size for a file to reside on the cache.
int64_t MaxFileSize() const override;
// These next methods (before the implementation of the Backend interface) are
// called by MemEntryImpl to update the state of the backend during the entry
// lifecycle.
// Signals that new entry has been created, and should be placed in
// |lru_list_| so that it is eligable for eviction.
void OnEntryInserted(MemEntryImpl* entry);
// Signals that an entry has been updated, and thus should be moved to the end
// of |lru_list_|.
void OnEntryUpdated(MemEntryImpl* entry);
// Signals that an entry has been doomed, and so it should be removed from the
// list of active entries as appropriate, as well as removed from the
// |lru_list_|.
void OnEntryDoomed(MemEntryImpl* entry);
// Adjust the current size of this backend by |delta|. This is used to
// determine if eviction is necessary and when eviction is finished.
void ModifyStorageSize(int32_t delta);
// Returns true if the cache's size is greater than the maximum allowed
// size.
bool HasExceededStorageSize() const;
// Sets a callback to be posted after we are destroyed. Should be called at
// most once.
void SetPostCleanupCallback(base::OnceClosure cb);
static base::Time Now(const base::WeakPtr<MemBackendImpl>& self);
void SetClockForTesting(base::Clock* clock); // doesn't take ownership.
// Backend interface.
int32_t GetEntryCount() const override;
EntryResult OpenOrCreateEntry(const std::string& key,
net::RequestPriority request_priority,
EntryResultCallback callback) override;
EntryResult OpenEntry(const std::string& key,
net::RequestPriority request_priority,
EntryResultCallback callback) override;
EntryResult CreateEntry(const std::string& key,
net::RequestPriority request_priority,
EntryResultCallback callback) override;
net::Error DoomEntry(const std::string& key,
net::RequestPriority priority,
CompletionOnceCallback callback) override;
net::Error DoomAllEntries(CompletionOnceCallback callback) override;
net::Error DoomEntriesBetween(base::Time initial_time,
base::Time end_time,
CompletionOnceCallback callback) override;
net::Error DoomEntriesSince(base::Time initial_time,
CompletionOnceCallback callback) override;
int64_t CalculateSizeOfAllEntries(
Int64CompletionOnceCallback callback) override;
int64_t CalculateSizeOfEntriesBetween(
base::Time initial_time,
base::Time end_time,
Int64CompletionOnceCallback callback) override;
std::unique_ptr<Iterator> CreateIterator() override;
void GetStats(base::StringPairs* stats) override {}
void OnExternalCacheHit(const std::string& key) override;
size_t DumpMemoryStats(
base::trace_event::ProcessMemoryDump* pmd,
const std::string& parent_absolute_name) const override;
private:
class MemIterator;
friend class MemIterator;
using EntryMap = std::unordered_map<std::string, MemEntryImpl*>;
// Deletes entries from the cache until the current size is below the limit.
void EvictIfNeeded();
// Deletes entries until the current size is below |goal|.
void EvictTill(int target_size);
// Called when we get low on memory.
void OnMemoryPressure(
base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
base::Clock* custom_clock_for_testing_; // usually nullptr.
EntryMap entries_;
// Stored in increasing order of last use time, from least recently used to
// most recently used.
base::LinkedList<MemEntryImpl> lru_list_;
int32_t max_size_; // Maximum data size for this instance.
int32_t current_size_;
net::NetLog* net_log_;
base::OnceClosure post_cleanup_callback_;
base::MemoryPressureListener memory_pressure_listener_;
base::WeakPtrFactory<MemBackendImpl> weak_factory_{this};
DISALLOW_COPY_AND_ASSIGN(MemBackendImpl);
};
} // namespace disk_cache
#endif // NET_DISK_CACHE_MEMORY_MEM_BACKEND_IMPL_H_