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   // Flush the memory-mapped section to disk (synchronously).
  42   void Flush();
  43
  44  private:
  45   virtual ~MappedFile();
  46
  47   bool init_;
  48 #if defined(OS_WIN)
  49   HANDLE section_;
  50 #endif
  51   void* buffer_;  // Address of the memory mapped buffer.
  52   size_t view_size_;  // Size of the memory pointed by buffer_.
  53 #if defined(POSIX_AVOID_MMAP)
  54   void* snapshot_;  // Copy of the buffer taken when it was last flushed.
  55 #endif
  56
  57   DISALLOW_COPY_AND_ASSIGN(MappedFile);
  58 };
  59
  60 // Helper class for calling Flush() on exit from the current scope.
  61 class ScopedFlush {
  62  public:
  63   explicit ScopedFlush(MappedFile* file) : file_(file) {}
  64   ~ScopedFlush() {
  65     file_->Flush();
  66   }
  67  private:
  68   MappedFile* file_;
  69 };
  70
  71 }  // namespace disk_cache
  72
  73 #endif  // NET_DISK_CACHE_MAPPED_FILE_H_