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
14namespace base {
15class FilePath;
16}
17
18namespace 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).
24class 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.
61class 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_
74