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  // 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.
66class 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_
79