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// Copyright (c) 2011 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.
#pragma once
#include "base/file_path.h"
#include "base/hash_tables.h"
#include "base/timer.h"
#include "net/disk_cache/block_files.h"
#include "net/disk_cache/disk_cache.h"
#include "net/disk_cache/eviction.h"
#include "net/disk_cache/in_flight_backend_io.h"
#include "net/disk_cache/rankings.h"
#include "net/disk_cache/stats.h"
#include "net/disk_cache/trace.h"
namespace net {
class NetLog;
} // namespace net
namespace disk_cache {
enum BackendFlags {
kNone = 0,
kMask = 1, // A mask (for the index table) was specified.
kMaxSize = 1 << 1, // A maximum size was provided.
kUnitTestMode = 1 << 2, // We are modifying the behavior for testing.
kUpgradeMode = 1 << 3, // This is the upgrade tool (dump).
kNewEviction = 1 << 4, // Use of new eviction was specified.
kNoRandom = 1 << 5, // Don't add randomness to the behavior.
kNoLoadProtection = 1 << 6, // Don't act conservatively under load.
kNoBuffering = 1 << 7 // Disable extended IO buffering.
// This class implements the Backend interface. An object of this
// class handles the operations of the cache for a particular profile.
class NET_TEST BackendImpl : public Backend {
friend class Eviction;
BackendImpl(const FilePath& path, base::MessageLoopProxy* cache_thread,
net::NetLog* net_log);
// mask can be used to limit the usable size of the hash table, for testing.
BackendImpl(const FilePath& path, uint32 mask,
base::MessageLoopProxy* cache_thread, net::NetLog* net_log);
virtual ~BackendImpl();
// Returns a new backend with the desired flags. See the declaration of
// CreateCacheBackend().
static int CreateBackend(const FilePath& full_path, bool force,
int max_bytes, net::CacheType type,
uint32 flags, base::MessageLoopProxy* thread,
net::NetLog* net_log, Backend** backend,
CompletionCallback* callback);
// Performs general initialization for this current instance of the cache.
int Init(CompletionCallback* callback);
// Performs the actual initialization and final cleanup on destruction.
int SyncInit();
void CleanupCache();
// Same bahavior as OpenNextEntry but walks the list from back to front.
int OpenPrevEntry(void** iter, Entry** prev_entry,
CompletionCallback* callback);
// Synchronous implementation of the asynchronous interface.
int SyncOpenEntry(const std::string& key, Entry** entry);
int SyncCreateEntry(const std::string& key, Entry** entry);
int SyncDoomEntry(const std::string& key);
int SyncDoomAllEntries();
int SyncDoomEntriesBetween(const base::Time initial_time,
const base::Time end_time);
int SyncDoomEntriesSince(const base::Time initial_time);
int SyncOpenNextEntry(void** iter, Entry** next_entry);
int SyncOpenPrevEntry(void** iter, Entry** prev_entry);
void SyncEndEnumeration(void* iter);
// Open or create an entry for the given |key| or |iter|.
EntryImpl* OpenEntryImpl(const std::string& key);
EntryImpl* CreateEntryImpl(const std::string& key);
EntryImpl* OpenNextEntryImpl(void** iter);
EntryImpl* OpenPrevEntryImpl(void** iter);
// Sets the maximum size for the total amount of data stored by this instance.
bool SetMaxSize(int max_bytes);
// Sets the cache type for this backend.
void SetType(net::CacheType type);
// Returns the full name for an external storage file.
FilePath GetFileName(Addr address) const;
// Returns the actual file used to store a given (non-external) address.
MappedFile* File(Addr address);
InFlightBackendIO* background_queue() {
return &background_queue_;
// Creates an external storage file.
bool CreateExternalFile(Addr* address);
// Creates a new storage block of size block_count.
bool CreateBlock(FileType block_type, int block_count,
Addr* block_address);
// Deletes a given storage block. deep set to true can be used to zero-fill
// the related storage in addition of releasing the related block.
void DeleteBlock(Addr block_address, bool deep);
// Retrieves a pointer to the lru-related data.
LruData* GetLruData();
// Updates the ranking information for an entry.
void UpdateRank(EntryImpl* entry, bool modified);
// A node was recovered from a crash, it may not be on the index, so this
// method checks it and takes the appropriate action.
void RecoveredEntry(CacheRankingsBlock* rankings);
// Permanently deletes an entry, but still keeps track of it.
void InternalDoomEntry(EntryImpl* entry);
// Removes all references to this entry.
void RemoveEntry(EntryImpl* entry);
// This method must be called when an entry is released for the last time, so
// the entry should not be used anymore. |address| is the cache address of the
// entry.
void OnEntryDestroyBegin(Addr address);
// This method must be called after all resources for an entry have been
// released.
void OnEntryDestroyEnd();
// If the data stored by the provided |rankings| points to an open entry,
// returns a pointer to that entry, otherwise returns NULL. Note that this
// method does NOT increase the ref counter for the entry.
EntryImpl* GetOpenEntry(CacheRankingsBlock* rankings) const;
// Returns the id being used on this run of the cache.
int32 GetCurrentEntryId() const;
// Returns the maximum size for a file to reside on the cache.
int MaxFileSize() const;
// A user data block is being created, extended or truncated.
void ModifyStorageSize(int32 old_size, int32 new_size);
// Logs requests that are denied due to being too big.
void TooMuchStorageRequested(int32 size);
// Returns true if a temporary buffer is allowed to be extended.
bool IsAllocAllowed(int current_size, int new_size);
// Tracks the release of |size| bytes by an entry buffer.
void BufferDeleted(int size);
// Only intended for testing the two previous methods.
int GetTotalBuffersSize() const {
return buffer_bytes_;
// Returns true if this instance seems to be under heavy load.
bool IsLoaded() const;
// Returns the full histogram name, for the given base |name| and experiment,
// and the current cache type. The name will be "DiskCache.t.name_e" where n
// is the cache type and e the provided |experiment|.
std::string HistogramName(const char* name, int experiment) const;
net::CacheType cache_type() const {
return cache_type_;
// Returns a weak pointer to this object.
base::WeakPtr<BackendImpl> GetWeakPtr();
// Returns the group for this client, based on the current cache size.
int GetSizeGroup() const;
// Returns true if we should send histograms for this user again. The caller
// must call this function only once per run (because it returns always the
// same thing on a given run).
bool ShouldReportAgain();
// Reports some data when we filled up the cache.
void FirstEviction();
// Reports a critical error (and disables the cache).
void CriticalError(int error);
// Reports an uncommon, recoverable error.
void ReportError(int error);
// Called when an interesting event should be logged (counted).
void OnEvent(Stats::Counters an_event);
// Keeps track of paylod access (doesn't include metadata).
void OnRead(int bytes);
void OnWrite(int bytes);
// Timer callback to calculate usage statistics.
void OnStatsTimer();
// Handles the pending asynchronous IO count.
void IncrementIoCount();
void DecrementIoCount();
// Sets internal parameters to enable unit testing mode.
void SetUnitTestMode();
// Sets internal parameters to enable upgrade mode (for internal tools).
void SetUpgradeMode();
// Sets the eviction algorithm to version 2.
void SetNewEviction();
// Sets an explicit set of BackendFlags.
void SetFlags(uint32 flags);
// Clears the counter of references to test handling of corruptions.
void ClearRefCountForTest();
// Sends a dummy operation through the operation queue, for unit tests.
int FlushQueueForTest(CompletionCallback* callback);
// Runs the provided task on the cache thread. The task will be automatically
// deleted after it runs.
int RunTaskForTest(Task* task, CompletionCallback* callback);
// Trims an entry (all if |empty| is true) from the list of deleted
// entries. This method should be called directly on the cache thread.
void TrimForTest(bool empty);
// Trims an entry (all if |empty| is true) from the list of deleted
// entries. This method should be called directly on the cache thread.
void TrimDeletedListForTest(bool empty);
// Peforms a simple self-check, and returns the number of dirty items
// or an error code (negative value).
int SelfCheck();
// Backend interface.
virtual int32 GetEntryCount() const;
virtual int OpenEntry(const std::string& key, Entry** entry,
CompletionCallback* callback);
virtual int CreateEntry(const std::string& key, Entry** entry,
CompletionCallback* callback);
virtual int DoomEntry(const std::string& key, CompletionCallback* callback);
virtual int DoomAllEntries(CompletionCallback* callback);
virtual int DoomEntriesBetween(const base::Time initial_time,
const base::Time end_time,
CompletionCallback* callback);
virtual int DoomEntriesSince(const base::Time initial_time,
CompletionCallback* callback);
virtual int OpenNextEntry(void** iter, Entry** next_entry,
CompletionCallback* callback);
virtual void EndEnumeration(void** iter);
virtual void GetStats(StatsItems* stats);
typedef base::hash_map<CacheAddr, EntryImpl*> EntriesMap;
// Creates a new backing file for the cache index.
bool CreateBackingStore(disk_cache::File* file);
bool InitBackingStore(bool* file_created);
void AdjustMaxCacheSize(int table_len);
// Deletes the cache and starts again.
void RestartCache(bool failure);
void PrepareForRestart();
// Creates a new entry object. Returns zero on success, or a disk_cache error
// on failure.
int NewEntry(Addr address, EntryImpl** entry);
// Returns a given entry from the cache. The entry to match is determined by
// key and hash, and the returned entry may be the matched one or it's parent
// on the list of entries with the same hash (or bucket). To look for a parent
// of a given entry, |entry_addr| should be grabbed from that entry, so that
// if it doesn't match the entry on the index, we know that it was replaced
// with a new entry; in this case |*match_error| will be set to true and the
// return value will be NULL.
EntryImpl* MatchEntry(const std::string& key, uint32 hash, bool find_parent,
Addr entry_addr, bool* match_error);
// Opens the next or previous entry on a cache iteration.
EntryImpl* OpenFollowingEntry(bool forward, void** iter);
// Opens the next or previous entry on a single list. If successfull,
// |from_entry| will be updated to point to the new entry, otherwise it will
// be set to NULL; in other words, it is used as an explicit iterator.
bool OpenFollowingEntryFromList(bool forward, Rankings::List list,
CacheRankingsBlock** from_entry,
EntryImpl** next_entry);
// Returns the entry that is pointed by |next|.
EntryImpl* GetEnumeratedEntry(CacheRankingsBlock* next);
// Re-opens an entry that was previously deleted.
EntryImpl* ResurrectEntry(EntryImpl* deleted_entry);
void DestroyInvalidEntry(EntryImpl* entry);
// Handles the used storage count.
void AddStorageSize(int32 bytes);
void SubstractStorageSize(int32 bytes);
// Update the number of referenced cache entries.
void IncreaseNumRefs();
void DecreaseNumRefs();
void IncreaseNumEntries();
void DecreaseNumEntries();
// Dumps current cache statistics to the log.
void LogStats();
// Send UMA stats.
void ReportStats();
// Upgrades the index file to version 2.1.
void UpgradeTo2_1();
// Performs basic checks on the index file. Returns false on failure.
bool CheckIndex();
// Part of the selt test. Returns the number or dirty entries, or an error.
int CheckAllEntries();
// Part of the self test. Returns false if the entry is corrupt.
bool CheckEntry(EntryImpl* cache_entry);
// Returns the maximum total memory for the memory buffers.
int MaxBuffersSize();
InFlightBackendIO background_queue_; // The controller of pending operations.
scoped_refptr<MappedFile> index_; // The main cache index.
FilePath path_; // Path to the folder used as backing storage.
Index* data_; // Pointer to the index data.
BlockFiles block_files_; // Set of files used to store all data.
Rankings rankings_; // Rankings to be able to trim the cache.
uint32 mask_; // Binary mask to map a hash to the hash table.
int32 max_size_; // Maximum data size for this instance.
Eviction eviction_; // Handler of the eviction algorithm.
EntriesMap open_entries_; // Map of open entries.
int num_refs_; // Number of referenced cache entries.
int max_refs_; // Max number of referenced cache entries.
int num_pending_io_; // Number of pending IO operations.
int entry_count_; // Number of entries accessed lately.
int byte_count_; // Number of bytes read/written lately.
int buffer_bytes_; // Total size of the temporary entries' buffers.
int io_delay_; // Average time (ms) required to complete some IO operations.
net::CacheType cache_type_;
int uma_report_; // Controls transmision of UMA data.
uint32 user_flags_; // Flags set by the user.
bool init_; // controls the initialization of the system.
bool restarted_;
bool unit_test_;
bool read_only_; // Prevents updates of the rankings data (used by tools).
bool disabled_;
bool new_eviction_; // What eviction algorithm should be used.
bool first_timer_; // True if the timer has not been called.
bool throttle_requests_;
net::NetLog* net_log_;
Stats stats_; // Usage statistcs.
base::RepeatingTimer<BackendImpl> timer_; // Usage timer.
base::WaitableEvent done_; // Signals the end of background work.
scoped_refptr<TraceObject> trace_object_; // Inits internal tracing.
ScopedRunnableMethodFactory<BackendImpl> factory_;
base::WeakPtrFactory<BackendImpl> ptr_factory_;
// Returns the prefered max cache size given the available disk space.
NET_TEST int PreferedCacheSize(int64 available);
} // namespace disk_cache