net/disk_cache/block_files.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.
   6
   7 #ifndef NET_DISK_CACHE_BLOCK_FILES_H_
   8 #define NET_DISK_CACHE_BLOCK_FILES_H_
   9
  10 #include <vector>
  11
  12 #include "base/files/file_path.h"
  13 #include "base/gtest_prod_util.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "net/base/net_export.h"
  16 #include "net/disk_cache/addr.h"
  17 #include "net/disk_cache/disk_format_base.h"
  18 #include "net/disk_cache/mapped_file.h"
  19
  20 namespace base {
  21 class ThreadChecker;
  22 }
  23
  24 namespace disk_cache {
  25
  26 // An instance of this class represents the header of a block file in memory.
  27 // Note that this class doesn't perform any file operation (as in it only deals
  28 // with entities in memory).
  29 // The header of a block file (and hence, this object) is all that is needed to
  30 // perform common operations like allocating or releasing space for storage;
  31 // actual access to that storage, however, is not performed through this class.
  32 class NET_EXPORT_PRIVATE BlockHeader {
  33  public:
  34   BlockHeader();
  35   explicit BlockHeader(BlockFileHeader* header);
  36   explicit BlockHeader(MappedFile* file);
  37   BlockHeader(const BlockHeader& other);
  38   ~BlockHeader();
  39
  40   // Creates a new entry of |size| blocks on the allocation map, updating the
  41   // apropriate counters.
  42   bool CreateMapBlock(int size, int* index);
  43
  44   // Deletes the block pointed by |index|.
  45   void DeleteMapBlock(int index, int block_size);
  46
  47   // Returns true if the specified block is used.
  48   bool UsedMapBlock(int index, int size);
  49
  50   // Restores the "empty counters" and allocation hints.
  51   void FixAllocationCounters();
  52
  53   // Returns true if the current block file should not be used as-is to store
  54   // more records. |block_count| is the number of blocks to allocate.
  55   bool NeedToGrowBlockFile(int block_count) const;
  56
  57   // Returns true if this block file can be used to store an extra record of
  58   // size |block_count|.
  59   bool CanAllocate(int block_count) const;
  60
  61   // Returns the number of empty blocks for this file.
  62   int EmptyBlocks() const;
  63
  64   // Returns the minumum number of allocations that can be satisfied.
  65   int MinimumAllocations() const;
  66
  67   // Returns the number of blocks that this file can store.
  68   int Capacity() const;
  69
  70   // Returns true if the counters look OK.
  71   bool ValidateCounters() const;
  72
  73   // Returns the identifiers of this and the next file (0 if there is none).
  74   int FileId() const;
  75   int NextFileId() const;
  76
  77   // Returns the size of the wrapped structure (BlockFileHeader).
  78   int Size() const;
  79
  80   // Returns a pointer to the underlying BlockFileHeader.
  81   // TODO(rvargas): This may be removed with the support for V2.
  82   BlockFileHeader* Header();
  83
  84  private:
  85   BlockFileHeader* header_;
  86 };
  87
  88 typedef std::vector<BlockHeader> BlockFilesBitmaps;
  89
  90 // This class handles the set of block-files open by the disk cache.
  91 class NET_EXPORT_PRIVATE BlockFiles {
  92  public:
  93   explicit BlockFiles(const base::FilePath& path);
  94   ~BlockFiles();
  95
  96   // Performs the object initialization. create_files indicates if the backing
  97   // files should be created or just open.
  98   bool Init(bool create_files);
  99
 100   // Returns the file that stores a given address.
 101   MappedFile* GetFile(Addr address);
 102
 103   // Creates a new entry on a block file. block_type indicates the size of block
 104   // to be used (as defined on cache_addr.h), block_count is the number of
 105   // blocks to allocate, and block_address is the address of the new entry.
 106   bool CreateBlock(FileType block_type, int block_count, Addr* block_address);
 107
 108   // Removes an entry from the block files. If deep is true, the storage is zero
 109   // filled; otherwise the entry is removed but the data is not altered (must be
 110   // already zeroed).
 111   void DeleteBlock(Addr address, bool deep);
 112
 113   // Close all the files and set the internal state to be initializad again. The
 114   // cache is being purged.
 115   void CloseFiles();
 116
 117   // Sends UMA stats.
 118   void ReportStats();
 119
 120   // Returns true if the blocks pointed by a given address are currently used.
 121   // This method is only intended for debugging.
 122   bool IsValid(Addr address);
 123
 124  private:
 125   // Set force to true to overwrite the file if it exists.
 126   bool CreateBlockFile(int index, FileType file_type, bool force);
 127   bool OpenBlockFile(int index);
 128
 129   // Attemp to grow this file. Fails if the file cannot be extended anymore.
 130   bool GrowBlockFile(MappedFile* file, BlockFileHeader* header);
 131
 132   // Returns the appropriate file to use for a new block.
 133   MappedFile* FileForNewBlock(FileType block_type, int block_count);
 134
 135   // Returns the next block file on this chain, creating new files if needed.
 136   MappedFile* NextFile(MappedFile* file);
 137
 138   // Creates an empty block file and returns its index.
 139   int CreateNextBlockFile(FileType block_type);
 140
 141   // Removes a chained block file that is now empty.
 142   bool RemoveEmptyFile(FileType block_type);
 143
 144   // Restores the header of a potentially inconsistent file.
 145   bool FixBlockFileHeader(MappedFile* file);
 146
 147   // Retrieves stats for the given file index.
 148   void GetFileStats(int index, int* used_count, int* load);
 149
 150   // Returns the filename for a given file index.
 151   base::FilePath Name(int index);
 152
 153   bool init_;
 154   char* zero_buffer_;  // Buffer to speed-up cleaning deleted entries.
 155   base::FilePath path_;  // Path to the backing folder.
 156   std::vector<MappedFile*> block_files_;  // The actual files.
 157   scoped_ptr<base::ThreadChecker> thread_checker_;
 158
 159   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_ZeroSizeFile);
 160   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_TruncatedFile);
 161   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_InvalidFile);
 162   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_Stats);
 163
 164   DISALLOW_COPY_AND_ASSIGN(BlockFiles);
 165 };
 166
 167 }  // namespace disk_cache
 168
 169 #endif  // NET_DISK_CACHE_BLOCK_FILES_H_