net/disk_cache/mem_backend_impl.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // See net/disk_cache/disk_cache.h for the public interface of the cache.
   6
   7 #ifndef NET_DISK_CACHE_MEM_BACKEND_IMPL_H__
   8 #define NET_DISK_CACHE_MEM_BACKEND_IMPL_H__
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/containers/hash_tables.h"
  12 #include "net/disk_cache/disk_cache.h"
  13 #include "net/disk_cache/mem_rankings.h"
  14
  15 namespace net {
  16 class NetLog;
  17 }  // namespace net
  18
  19 namespace disk_cache {
  20
  21 class MemEntryImpl;
  22
  23 // This class implements the Backend interface. An object of this class handles
  24 // the operations of the cache without writing to disk.
  25 class NET_EXPORT_PRIVATE MemBackendImpl : public Backend {
  26  public:
  27   explicit MemBackendImpl(net::NetLog* net_log);
  28   virtual ~MemBackendImpl();
  29
  30   // Returns an instance of a Backend implemented only in memory. The returned
  31   // object should be deleted when not needed anymore. max_bytes is the maximum
  32   // size the cache can grow to. If zero is passed in as max_bytes, the cache
  33   // will determine the value to use based on the available memory. The returned
  34   // pointer can be NULL if a fatal error is found.
  35   static Backend* CreateBackend(int max_bytes, net::NetLog* net_log);
  36
  37   // Performs general initialization for this current instance of the cache.
  38   bool Init();
  39
  40   // Sets the maximum size for the total amount of data stored by this instance.
  41   bool SetMaxSize(int max_bytes);
  42
  43   // Permanently deletes an entry.
  44   void InternalDoomEntry(MemEntryImpl* entry);
  45
  46   // Updates the ranking information for an entry.
  47   void UpdateRank(MemEntryImpl* node);
  48
  49   // A user data block is being created, extended or truncated.
  50   void ModifyStorageSize(int32 old_size, int32 new_size);
  51
  52   // Returns the maximum size for a file to reside on the cache.
  53   int MaxFileSize() const;
  54
  55   // Insert an MemEntryImpl into the ranking list. This method is only called
  56   // from MemEntryImpl to insert child entries. The reference can be removed
  57   // by calling RemoveFromRankingList(|entry|).
  58   void InsertIntoRankingList(MemEntryImpl* entry);
  59
  60   // Remove |entry| from ranking list. This method is only called from
  61   // MemEntryImpl to remove a child entry from the ranking list.
  62   void RemoveFromRankingList(MemEntryImpl* entry);
  63
  64   // Backend interface.
  65   virtual net::CacheType GetCacheType() const OVERRIDE;
  66   virtual int32 GetEntryCount() const OVERRIDE;
  67   virtual int OpenEntry(const std::string& key, Entry** entry,
  68                         const CompletionCallback& callback) OVERRIDE;
  69   virtual int CreateEntry(const std::string& key, Entry** entry,
  70                           const CompletionCallback& callback) OVERRIDE;
  71   virtual int DoomEntry(const std::string& key,
  72                         const CompletionCallback& callback) OVERRIDE;
  73   virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
  74   virtual int DoomEntriesBetween(base::Time initial_time,
  75                                  base::Time end_time,
  76                                  const CompletionCallback& callback) OVERRIDE;
  77   virtual int DoomEntriesSince(base::Time initial_time,
  78                                const CompletionCallback& callback) OVERRIDE;
  79   virtual int OpenNextEntry(void** iter, Entry** next_entry,
  80                             const CompletionCallback& callback) OVERRIDE;
  81   virtual void EndEnumeration(void** iter) OVERRIDE;
  82   virtual void GetStats(
  83       std::vector<std::pair<std::string, std::string> >* stats) OVERRIDE {}
  84   virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
  85
  86  private:
  87   typedef base::hash_map<std::string, MemEntryImpl*> EntryMap;
  88
  89   // Old Backend interface.
  90   bool OpenEntry(const std::string& key, Entry** entry);
  91   bool CreateEntry(const std::string& key, Entry** entry);
  92   bool DoomEntry(const std::string& key);
  93   bool DoomAllEntries();
  94   bool DoomEntriesBetween(const base::Time initial_time,
  95                           const base::Time end_time);
  96   bool DoomEntriesSince(const base::Time initial_time);
  97   bool OpenNextEntry(void** iter, Entry** next_entry);
  98
  99   // Deletes entries from the cache until the current size is below the limit.
 100   // If empty is true, the whole cache will be trimmed, regardless of being in
 101   // use.
 102   void TrimCache(bool empty);
 103
 104   // Handles the used storage count.
 105   void AddStorageSize(int32 bytes);
 106   void SubstractStorageSize(int32 bytes);
 107
 108   EntryMap entries_;
 109   MemRankings rankings_;  // Rankings to be able to trim the cache.
 110   int32 max_size_;        // Maximum data size for this instance.
 111   int32 current_size_;
 112
 113   net::NetLog* net_log_;
 114
 115   DISALLOW_COPY_AND_ASSIGN(MemBackendImpl);
 116 };
 117
 118 }  // namespace disk_cache
 119
 120 #endif  // NET_DISK_CACHE_MEM_BACKEND_IMPL_H__