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

net/disk_cache/block_files.h

Index: net/disk_cache/block_files.h
===================================================================
--- net/disk_cache/block_files.h	(revision 199883)
+++ net/disk_cache/block_files.h	(working copy)
@@ -14,6 +14,7 @@
 #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 {
@@ -22,6 +23,60 @@
 
 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.
+class NET_EXPORT_PRIVATE BlockHeader {
+ public:
+  BlockHeader();
+  explicit BlockHeader(BlockFileHeader* header);
+  explicit BlockHeader(MappedFile* file);
+  BlockHeader(const BlockHeader& other);
+  ~BlockHeader();
+
+  // Creates a new entry on the allocation map, updating the apropriate
+  // counters. |target| is the type of block to use (number of empty blocks),
+  // and |size| is the actual number of blocks to use.
+  bool CreateMapBlock(int target, 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);
+
+  // Returns true if this block file can be used to store an extra record of
+  // size |block_count|.
+  bool CanAllocate(int block_count);
+
+  // Returns the number of empty blocks for this file.
+  int EmptyBlocks() const;
+
+  // Returns true if the counters look OK.
+  bool ValidateCounters() const;
+
+  // Returns the size of the wrapped structure (BlockFileHeader).
+  int Size() const;
+
+  BlockFileHeader* operator->() { return header_; }
+  void operator=(const BlockHeader& other) { header_ = other.header_; }
+  BlockFileHeader* Get() { return header_; }
+
+ private:
+  // Set force to true to overwrite the file if it exists.
+  //bool CreateBlockFile(int index, FileType file_type, bool force);
+
+  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:
@@ -30,8 +85,11 @@
 
   // 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);
 
@@ -56,13 +114,16 @@
   // 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);
@@ -70,25 +131,40 @@
   // 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);
 
   // 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);