net/disk_cache/mapped_file.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 of the cache.
   6
   7 #ifndef NET_DISK_CACHE_MAPPED_FILE_H_
   8 #define NET_DISK_CACHE_MAPPED_FILE_H_
   9
  10 #include "net/base/net_export.h"
  11 #include "net/disk_cache/file.h"
  12 #include "net/disk_cache/file_block.h"
  13
  14 namespace base {
  15 class FilePath;
  16 }
  17
  18 namespace disk_cache {
  19
  20 // This class implements a memory mapped file used to access block-files. The
  21 // idea is that the header and bitmap will be memory mapped all the time, and
  22 // the actual data for the blocks will be access asynchronously (most of the
  23 // time).
  24 class NET_EXPORT_PRIVATE MappedFile : public File {
  25  public:
  26   MappedFile() : File(true), init_(false) {}
  27
  28   // Performs object initialization. name is the file to use, and size is the
  29   // amount of data to memory map from the file. If size is 0, the whole file
  30   // will be mapped in memory.
  31   void* Init(const base::FilePath& name, size_t size);
  32
  33   void* buffer() const {
  34     return buffer_;
  35   }
  36
  37   // Loads or stores a given block from the backing file (synchronously).
  38   bool Load(const FileBlock* block);
  39   bool Store(const FileBlock* block);
  40
  41   // Asynchronous versions of Load/Store, following the semantics of File::Read
  42   // and File::Write.
  43   bool Load(const FileBlock* block, FileIOCallback* callback, bool* completed);
  44   bool Store(const FileBlock* block, FileIOCallback* callback, bool* completed);
  45
  46   // Flush the memory-mapped section to disk (synchronously).
  47   void Flush();
  48
  49  private:
  50   virtual ~MappedFile();
  51
  52   bool init_;
  53 #if defined(OS_WIN)
  54   HANDLE section_;
  55 #endif
  56   void* buffer_;  // Address of the memory mapped buffer.
  57   size_t view_size_;  // Size of the memory pointed by buffer_.
  58 #if defined(POSIX_AVOID_MMAP)
  59   void* snapshot_;  // Copy of the buffer taken when it was last flushed.
  60 #endif
  61
  62   DISALLOW_COPY_AND_ASSIGN(MappedFile);
  63 };
  64
  65 // Helper class for calling Flush() on exit from the current scope.
  66 class ScopedFlush {
  67  public:
  68   explicit ScopedFlush(MappedFile* file) : file_(file) {}
  69   ~ScopedFlush() {
  70     file_->Flush();
  71   }
  72  private:
  73   MappedFile* file_;
  74 };
  75
  76 }  // namespace disk_cache
  77
  78 #endif  // NET_DISK_CACHE_MAPPED_FILE_H_