text: // 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.
  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 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:
    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);
  
    // 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);
  
   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);
  
    // 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);
  
    // 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);
  
    // Restores the header of a potentially inconsistent file.
    bool FixBlockFileHeader(MappedFile* file);
  
    // 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);
  
    bool init_;
    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.
    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_
  