net/disk_cache/memory/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_MEMORY_MEM_BACKEND_IMPL_H_
   8 #define NET_DISK_CACHE_MEMORY_MEM_BACKEND_IMPL_H_
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/containers/hash_tables.h"
  12 #include "base/memory/weak_ptr.h"
  13 #include "net/disk_cache/disk_cache.h"
  14 #include "net/disk_cache/memory/mem_rankings.h"
  15
  16 namespace net {
  17 class NetLog;
  18 }  // namespace net
  19
  20 namespace disk_cache {
  21
  22 class MemEntryImpl;
  23
  24 // This class implements the Backend interface. An object of this class handles
  25 // the operations of the cache without writing to disk.
  26 class NET_EXPORT_PRIVATE MemBackendImpl : public Backend {
  27  public:
  28   explicit MemBackendImpl(net::NetLog* net_log);
  29   ~MemBackendImpl() override;
  30
  31   // Returns an instance of a Backend implemented only in memory. The returned
  32   // object should be deleted when not needed anymore. max_bytes is the maximum
  33   // size the cache can grow to. If zero is passed in as max_bytes, the cache
  34   // will determine the value to use based on the available memory. The returned
  35   // pointer can be NULL if a fatal error is found.
  36   static scoped_ptr<Backend> CreateBackend(int max_bytes, net::NetLog* net_log);
  37
  38   // Performs general initialization for this current instance of the cache.
  39   bool Init();
  40
  41   // Sets the maximum size for the total amount of data stored by this instance.
  42   bool SetMaxSize(int max_bytes);
  43
  44   // Permanently deletes an entry.
  45   void InternalDoomEntry(MemEntryImpl* entry);
  46
  47   // Updates the ranking information for an entry.
  48   void UpdateRank(MemEntryImpl* node);
  49
  50   // A user data block is being created, extended or truncated.
  51   void ModifyStorageSize(int32 old_size, int32 new_size);
  52
  53   // Returns the maximum size for a file to reside on the cache.
  54   int MaxFileSize() const;
  55
  56   // Insert an MemEntryImpl into the ranking list. This method is only called
  57   // from MemEntryImpl to insert child entries. The reference can be removed
  58   // by calling RemoveFromRankingList(|entry|).
  59   void InsertIntoRankingList(MemEntryImpl* entry);
  60
  61   // Remove |entry| from ranking list. This method is only called from
  62   // MemEntryImpl to remove a child entry from the ranking list.
  63   void RemoveFromRankingList(MemEntryImpl* entry);
  64
  65   // Backend interface.
  66   net::CacheType GetCacheType() const override;
  67   int32 GetEntryCount() const override;
  68   int OpenEntry(const std::string& key,
  69                 Entry** entry,
  70                 const CompletionCallback& callback) override;
  71   int CreateEntry(const std::string& key,
  72                   Entry** entry,
  73                   const CompletionCallback& callback) override;
  74   int DoomEntry(const std::string& key,
  75                 const CompletionCallback& callback) override;
  76   int DoomAllEntries(const CompletionCallback& callback) override;
  77   int DoomEntriesBetween(base::Time initial_time,
  78                          base::Time end_time,
  79                          const CompletionCallback& callback) override;
  80   int DoomEntriesSince(base::Time initial_time,
  81                        const CompletionCallback& callback) override;
  82   scoped_ptr<Iterator> CreateIterator() override;
  83   void GetStats(
  84       std::vector<std::pair<std::string, std::string>>* stats) override {}
  85   void OnExternalCacheHit(const std::string& key) override;
  86
  87  private:
  88   class MemIterator;
  89   friend class MemIterator;
  90
  91   typedef base::hash_map<std::string, MemEntryImpl*> EntryMap;
  92
  93   // Old Backend interface.
  94   bool OpenEntry(const std::string& key, Entry** entry);
  95   bool CreateEntry(const std::string& key, Entry** entry);
  96   bool DoomEntry(const std::string& key);
  97   bool DoomAllEntries();
  98   bool DoomEntriesBetween(const base::Time initial_time,
  99                           const base::Time end_time);
 100   bool DoomEntriesSince(const base::Time initial_time);
 101
 102   // Deletes entries from the cache until the current size is below the limit.
 103   // If empty is true, the whole cache will be trimmed, regardless of being in
 104   // use.
 105   void TrimCache(bool empty);
 106
 107   // Handles the used storage count.
 108   void AddStorageSize(int32 bytes);
 109   void SubstractStorageSize(int32 bytes);
 110
 111   EntryMap entries_;
 112   MemRankings rankings_;  // Rankings to be able to trim the cache.
 113   int32 max_size_;        // Maximum data size for this instance.
 114   int32 current_size_;
 115
 116   net::NetLog* net_log_;
 117
 118   base::WeakPtrFactory<MemBackendImpl> weak_factory_;
 119
 120   DISALLOW_COPY_AND_ASSIGN(MemBackendImpl);
 121 };
 122
 123 }  // namespace disk_cache
 124
 125 #endif  // NET_DISK_CACHE_MEMORY_MEM_BACKEND_IMPL_H_