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.
  28 class NET_EXPORT_PRIVATE BlockHeader {
  29  public:
  30   BlockHeader();
  31   explicit BlockHeader(BlockFileHeader* header);
  32   explicit BlockHeader(MappedFile* file);
  33   BlockHeader(const BlockHeader& other);
  34   ~BlockHeader();
  35
  36   // Creates a new entry on the allocation map, updating the apropriate
  37   // counters. |target| is the type of block to use (number of empty blocks),
  38   // and |size| is the actual number of blocks to use.
  39   bool CreateMapBlock(int target, int size, int* index);
  40
  41   // Deletes the block pointed by |index|.
  42   void DeleteMapBlock(int index, int block_size);
  43
  44   // Returns true if the specified block is used.
  45   bool UsedMapBlock(int index, int size);
  46
  47   // Restores the "empty counters" and allocation hints.
  48   void FixAllocationCounters();
  49
  50   // Returns true if the current block file should not be used as-is to store
  51   // more records. |block_count| is the number of blocks to allocate.
  52   bool NeedToGrowBlockFile(int block_count);
  53
  54   // Returns the number of empty blocks for this file.
  55   int EmptyBlocks() const;
  56
  57   // Returns true if the counters look OK.
  58   bool ValidateCounters() const;
  59
  60   // Returns the size of the wrapped structure (BlockFileHeader).
  61   int Size() const;
  62
  63   BlockFileHeader* operator->() { return header_; }
  64   void operator=(const BlockHeader& other) { header_ = other.header_; }
  65   BlockFileHeader* Get() { return header_; }
  66
  67  private:
  68   BlockFileHeader* header_;
  69 };
  70
  71 typedef std::vector<BlockHeader> BlockFilesBitmaps;
  72
  73 // This class handles the set of block-files open by the disk cache.
  74 class NET_EXPORT_PRIVATE BlockFiles {
  75  public:
  76   explicit BlockFiles(const base::FilePath& path);
  77   ~BlockFiles();
  78
  79   // Performs the object initialization. create_files indicates if the backing
  80   // files should be created or just open.
  81   bool Init(bool create_files);
  82
  83   // Returns the file that stores a given address.
  84   MappedFile* GetFile(Addr address);
  85
  86   // Creates a new entry on a block file. block_type indicates the size of block
  87   // to be used (as defined on cache_addr.h), block_count is the number of
  88   // blocks to allocate, and block_address is the address of the new entry.
  89   bool CreateBlock(FileType block_type, int block_count, Addr* block_address);
  90
  91   // Removes an entry from the block files. If deep is true, the storage is zero
  92   // filled; otherwise the entry is removed but the data is not altered (must be
  93   // already zeroed).
  94   void DeleteBlock(Addr address, bool deep);
  95
  96   // Close all the files and set the internal state to be initializad again. The
  97   // cache is being purged.
  98   void CloseFiles();
  99
 100   // Sends UMA stats.
 101   void ReportStats();
 102
 103   // Returns true if the blocks pointed by a given address are currently used.
 104   // This method is only intended for debugging.
 105   bool IsValid(Addr address);
 106
 107  private:
 108   // Set force to true to overwrite the file if it exists.
 109   bool CreateBlockFile(int index, FileType file_type, bool force);
 110   bool OpenBlockFile(int index);
 111
 112   // Attemp to grow this file. Fails if the file cannot be extended anymore.
 113   bool GrowBlockFile(MappedFile* file, BlockFileHeader* header);
 114
 115   // Returns the appropriate file to use for a new block.
 116   MappedFile* FileForNewBlock(FileType block_type, int block_count);
 117
 118   // Returns the next block file on this chain, creating new files if needed.
 119   MappedFile* NextFile(MappedFile* file);
 120
 121   // Creates an empty block file and returns its index.
 122   int CreateNextBlockFile(FileType block_type);
 123
 124   // Removes a chained block file that is now empty.
 125   bool RemoveEmptyFile(FileType block_type);
 126
 127   // Restores the header of a potentially inconsistent file.
 128   bool FixBlockFileHeader(MappedFile* file);
 129
 130   // Retrieves stats for the given file index.
 131   void GetFileStats(int index, int* used_count, int* load);
 132
 133   // Returns the filename for a given file index.
 134   base::FilePath Name(int index);
 135
 136   bool init_;
 137   char* zero_buffer_;  // Buffer to speed-up cleaning deleted entries.
 138   base::FilePath path_;  // Path to the backing folder.
 139   std::vector<MappedFile*> block_files_;  // The actual files.
 140   scoped_ptr<base::ThreadChecker> thread_checker_;
 141
 142   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_ZeroSizeFile);
 143   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_TruncatedFile);
 144   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_InvalidFile);
 145   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_Stats);
 146
 147   DISALLOW_COPY_AND_ASSIGN(BlockFiles);
 148 };
 149
 150 }  // namespace disk_cache
 151
 152 #endif  // NET_DISK_CACHE_BLOCK_FILES_H_