Disk cache: Reference CL for the implementation of file format version 3.

net/disk_cache/block_files.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // See net/disk_cache/disk_cache.h for the public interface.
 
 #ifndef NET_DISK_CACHE_BLOCK_FILES_H_
 #define NET_DISK_CACHE_BLOCK_FILES_H_
 
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/base/net_export.h"
 #include "net/disk_cache/addr.h"
+#include "net/disk_cache/disk_format_base.h"
 #include "net/disk_cache/mapped_file.h"
 
 namespace base {
 class ThreadChecker;
 }
 
 namespace disk_cache {
 
+// An instance of this class represents the header of a block file in memory.
+// Note that this class doesn't perform any file operation (as in it only deals
+// with entities in memory).
+// The header of a block file (and hence, this object) is all that is needed to
+// perform common operations like allocating or releasing space for storage;
+// actual access to that storage, however, is not performed through this class.
+class NET_EXPORT_PRIVATE BlockHeader {
+ public:
+  BlockHeader();
+  explicit BlockHeader(BlockFileHeader* header);
+  explicit BlockHeader(MappedFile* file);
+  BlockHeader(const BlockHeader& other);
+  ~BlockHeader();
+
+  // Creates a new entry of |size| blocks on the allocation map, updating the
+  // apropriate counters.
+  bool CreateMapBlock(int size, int* index);
+
+  // Deletes the block pointed by |index|.
+  void DeleteMapBlock(int index, int block_size);
+
+  // Returns true if the specified block is used.
+  bool UsedMapBlock(int index, int size);
+
+  // Restores the "empty counters" and allocation hints.
+  void FixAllocationCounters();
+
+  // Returns true if the current block file should not be used as-is to store
+  // more records. |block_count| is the number of blocks to allocate.
+  bool NeedToGrowBlockFile(int block_count) const;
+
+  // Returns true if this block file can be used to store an extra record of
+  // size |block_count|.
+  bool CanAllocate(int block_count) const;
+
+  // Returns the number of empty blocks for this file.
+  int EmptyBlocks() const;
+
+  // Returns the minumum number of allocations that can be satisfied.
+  int MinimumAllocations() const;
+
+  // Returns the number of blocks that this file can store.
+  int Capacity() const;
+
+  // Returns true if the counters look OK.
+  bool ValidateCounters() const;
+
+  // Returns the identifiers of this and the next file (0 if there is none).
+  int FileId() const;
+  int NextFileId() const;
+
+  // Returns a pointer to the underlying BlockFileHeader.
+  // TODO(rvargas): This may be removed with the support for V2.
+  BlockFileHeader* Header();
+
+ private:
+  BlockFileHeader* header_;
+};
+
+typedef std::vector<BlockHeader> BlockFilesBitmaps;
+
 // This class handles the set of block-files open by the disk cache.
 class NET_EXPORT_PRIVATE BlockFiles {
  public:
   explicit BlockFiles(const base::FilePath& path);
   ~BlockFiles();
 
   // Performs the object initialization. create_files indicates if the backing
   // files should be created or just open.
-  bool Init(bool create_files);
+  bool Init(bool create_files, int num_files);
+
+  // Returns the allocation bitmaps for all the files managed by this object.
+  void GetBitmaps(int num_files, BlockFilesBitmaps* bitmaps);
 
   // Returns the file that stores a given address.
   MappedFile* GetFile(Addr address);
 
   // Creates a new entry on a block file. block_type indicates the size of block
   // to be used (as defined on cache_addr.h), block_count is the number of
   // blocks to allocate, and block_address is the address of the new entry.
   bool CreateBlock(FileType block_type, int block_count, Addr* block_address);
 
   // Removes an entry from the block files. If deep is true, the storage is zero
   // filled; otherwise the entry is removed but the data is not altered (must be
   // already zeroed).
   void DeleteBlock(Addr address, bool deep);
 
   // Close all the files and set the internal state to be initializad again. The
   // cache is being purged.
   void CloseFiles();
 
   // Sends UMA stats.
   void ReportStats();
 
   // Returns true if the blocks pointed by a given address are currently used.
   // This method is only intended for debugging.
   bool IsValid(Addr address);
 
+  // Increments the size of files very slowly.
+  void UseSmallSizeIncrementsForTest() { small_steps_ = true; }
+
  private:
   // Set force to true to overwrite the file if it exists.
   bool CreateBlockFile(int index, FileType file_type, bool force);
   bool OpenBlockFile(int index);
 
   // Attemp to grow this file. Fails if the file cannot be extended anymore.
-  bool GrowBlockFile(MappedFile* file, BlockFileHeader* header);
+  bool GrowBlockFile(BlockFileHeader* header);
 
   // Returns the appropriate file to use for a new block.
   MappedFile* FileForNewBlock(FileType block_type, int block_count);
 
   // Returns the next block file on this chain, creating new files if needed.
   MappedFile* NextFile(MappedFile* file);
 
+  // Returns the file index that stores a given address, or -1 on failure.
+  int GetFileIndex(Addr address);
+
+  // Returns the header file that stores a given address.
+  MappedFile* GetFileHeader(Addr address);
+
   // Creates an empty block file and returns its index.
   int CreateNextBlockFile(FileType block_type);
 
   // Removes a chained block file that is now empty.
   bool RemoveEmptyFile(FileType block_type);
 
+  bool PreallocateSpace(FileType block_type);
+
   // Restores the header of a potentially inconsistent file.
-  bool FixBlockFileHeader(MappedFile* file);
+  bool FixBlockFileHeader(int index);//pass BlockHeader instead.
 
   // Retrieves stats for the given file index.
   void GetFileStats(int index, int* used_count, int* load);
 
-  // Returns the filename for a given file index.
-  base::FilePath Name(int index);
+  // Returns the filename for the header section, given a file index.
+  base::FilePath HeaderName(int index);
+
+  // Returns the filename for the data portion, given a file index.
+  base::FilePath DataName(int index);
 
   bool init_;
+  bool small_steps_;
+  int data_offset_;  // Zero for V3.
   char* zero_buffer_;  // Buffer to speed-up cleaning deleted entries.
   base::FilePath path_;  // Path to the backing folder.
-  std::vector<MappedFile*> block_files_;  // The actual files.
+  std::vector<MappedFile*> block_headers_;  // The block file headers.
+  std::vector<MappedFile*> block_data_;  // The user data (if not stored with
+                                         // the header).
   scoped_ptr<base::ThreadChecker> thread_checker_;
 
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_ZeroSizeFile);
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_TruncatedFile);
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_InvalidFile);
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_Stats);
 
   DISALLOW_COPY_AND_ASSIGN(BlockFiles);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BLOCK_FILES_H_