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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// See net/disk_cache/disk_cache.h for the public interface of the cache.
+
+#ifndef NET_DISK_CACHE_BACKEND_IMPL_H__
+#define NET_DISK_CACHE_BACKEND_IMPL_H__
+
+#include "net/disk_cache/block_files.h"
+#include "net/disk_cache/disk_cache.h"
+#include "net/disk_cache/rankings.h"
+#include "net/disk_cache/stats.h"
+#include "net/disk_cache/trace.h"
+
+class Timer;
+
+namespace disk_cache {
+
+// This class implements the Backend interface. An object of this
+// class handles the operations of the cache for a particular profile.
+class BackendImpl : public Backend {
+ public:
+  explicit BackendImpl(const std::wstring& path)
+      : path_(path), init_(false), mask_(0), block_files_(path),
+        unit_test_(false), restarted_(false), max_size_(0) {}
+  // mask can be used to limit the usable size of the hash table, for testing.
+  BackendImpl(const std::wstring& path, uint32 mask)
+      : path_(path), init_(false), mask_(mask), block_files_(path),
+        unit_test_(false), restarted_(false), max_size_(0) {}
+  ~BackendImpl();
+
+  // Performs general initialization for this current instance of the cache.
+  bool Init();
+
+  // Backend interface.
+  virtual int32 GetEntryCount() const;
+  virtual bool OpenEntry(const std::string& key, Entry** entry);
+  virtual bool CreateEntry(const std::string& key, Entry** entry);
+  virtual bool DoomEntry(const std::string& key);
+  virtual bool DoomAllEntries();
+  virtual bool DoomEntriesBetween(const Time initial_time,
+                                  const Time end_time);
+  virtual bool DoomEntriesSince(const Time initial_time);
+  virtual bool OpenNextEntry(void** iter, Entry** next_entry);
+  virtual void EndEnumeration(void** iter);
+  virtual void GetStats(StatsItems* stats);
+
+  // Sets the maximum size for the total amount of data stored by this instance.
+  bool SetMaxSize(int max_bytes);
+
+  // Returns the actual file used to store a given (non-external) address.
+  MappedFile* File(Addr address) {
+    if (disabled_)
+      return NULL;
+    return block_files_.GetFile(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);
+
+  // Permanently deletes an entry.
+  void InternalDoomEntry(EntryImpl* entry);
+
+  // Returns the full name for an external storage file.
+  std::wstring GetFileName(Addr address) const;
+
+  // Creates an external storage file.
+  bool CreateExternalFile(Addr* address);
+
+  // Updates the ranking information for an entry.
+  void UpdateRank(CacheRankingsBlock* node, bool modified);
+
+  // This method must be called whenever an entry is released for the last time.
+  void CacheEntryDestroyed();
+
+  // Handles the pending asynchronous IO count.
+  void IncrementIoCount();
+  void DecrementIoCount();
+
+  // Returns the id being used on this run of the cache.
+  int32 GetCurrentEntryId();
+
+  // 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);
+
+  // Clears the counter of references to test handling of corruptions.
+  void ClearRefCountForTest();
+
+  // Sets internal parameters to enable unit testing mode.
+  void SetUnitTestMode();
+
+  // A user data block is being created, extended or truncated.
+  void ModifyStorageSize(int32 old_size, int32 new_size);
+
+  // Returns the maximum size for a file to reside on the cache.
+  int MaxFileSize() const;
+
+  // Logs requests that are denied due to being too big.
+  void TooMuchStorageRequested(int32 size);
+
+  // Called when an interesting event should be logged (counted).
+  void OnEvent(Stats::Counters an_event);
+
+  // Timer callback to calculate usage statistics.
+  void OnStatsTimer();
+
+  // Peforms a simple self-check, and returns the number of dirty items
+  // or an error code (negative value).
+  int SelfCheck();
+
+  // Reports a critical error (and disables the cache).
+  void CriticalError(int error);
+
+ private:
+  // Creates a new backing file for the cache index.
+  bool CreateBackingStore(HANDLE file);
+  bool InitBackingStore(bool* file_created);
+
+  // 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).
+  EntryImpl* MatchEntry(const std::string& key, uint32 hash,
+                         bool find_parent);
+
+  // Deletes entries from the cache until the current size is below the limit.
+  // If empty is true, the whole cache will be trimmed, regardless of being in
+  // use.
+  void TrimCache(bool empty);
+
+  void DestroyInvalidEntry(Addr address, EntryImpl* entry);
+
+  // Creates a new entry object and checks to see if it is dirty. Returns zero
+  // on success, or a disk_cache error on failure.
+  int NewEntry(Addr address, EntryImpl** entry, bool* dirty);
+
+  // 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);
+
+  // Performs basic checks on the index file. Returns false on failure.
+  bool CheckIndex();
+
+  // Dumps current cache statistics to the log.
+  void LogStats();
+
+  // Deletes the cache and starts again.
+  void RestartCache();
+
+  // 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 AdjustMaxCacheSize(int table_len);
+
+  scoped_refptr<MappedFile> index_;  // The main cache index.
+  std::wstring 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.
+  int num_refs_;  // Number of referenced cache entries.
+  int max_refs_;  // Max number of eferenced cache entries.
+  int num_pending_io_;  // Number of pending IO operations;
+  bool init_;  // controls the initialization of the system.
+  bool restarted_;
+  bool unit_test_;
+  bool disabled_;
+
+  Stats stats_;  // Usage statistcs.
+  Task* timer_task_;
+  Timer* timer_;  // Usage timer.
+  TraceObject trace_object_;  // Inits and destroys internal tracing.
+
+  DISALLOW_EVIL_CONSTRUCTORS(BackendImpl);
+};
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_BACKEND_IMPL_H__