1// Copyright 2013 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#ifndef BASE_FILES_MEMORY_MAPPED_FILE_H_
6#define BASE_FILES_MEMORY_MAPPED_FILE_H_
7
8#include "base/base_export.h"
9#include "base/basictypes.h"
10#include "base/files/file.h"
11#include "build/build_config.h"
12
13#if defined(OS_WIN)
14#include <windows.h>
15#endif
16
17namespace base {
18
19class FilePath;
20
21class BASE_EXPORT MemoryMappedFile {
22 public:
23  // The default constructor sets all members to invalid/null values.
24  MemoryMappedFile();
25  ~MemoryMappedFile();
26
27  // Used to hold information about a region [offset + size] of a file.
28  struct BASE_EXPORT Region {
29    static const Region kWholeFile;
30
31    Region(int64 offset, int64 size);
32
33    bool operator==(const Region& other) const;
34
35    // Start of the region (measured in bytes from the beginning of the file).
36    int64 offset;
37
38    // Length of the region in bytes.
39    int64 size;
40
41   private:
42    // This ctor is used only by kWholeFile, to construct a zero-sized Region
43    // (which is forbidden by the public ctor) and uniquely identify kWholeFile.
44    Region(base::LinkerInitialized);
45  };
46
47  // Opens an existing file and maps it into memory. Access is restricted to
48  // read only. If this object already points to a valid memory mapped file
49  // then this method will fail and return false. If it cannot open the file,
50  // the file does not exist, or the memory mapping fails, it will return false.
51  // Later we may want to allow the user to specify access.
52  bool Initialize(const FilePath& file_name);
53
54  // As above, but works with an already-opened file. MemoryMappedFile takes
55  // ownership of |file| and closes it when done.
56  bool Initialize(File file);
57
58  // As above, but works with a region of an already-opened file.
59  bool Initialize(File file, const Region& region);
60
61#if defined(OS_WIN)
62  // Opens an existing file and maps it as an image section. Please refer to
63  // the Initialize function above for additional information.
64  bool InitializeAsImageSection(const FilePath& file_name);
65#endif  // OS_WIN
66
67  const uint8* data() const { return data_; }
68  size_t length() const { return length_; }
69
70  // Is file_ a valid file handle that points to an open, memory mapped file?
71  bool IsValid() const;
72
73 private:
74  // Given the arbitrarily aligned memory region [start, size], returns the
75  // boundaries of the region aligned to the granularity specified by the OS,
76  // (a page on Linux, ~32k on Windows) as follows:
77  // - |aligned_start| is page aligned and <= |start|.
78  // - |aligned_size| is a multiple of the VM granularity and >= |size|.
79  // - |offset| is the displacement of |start| w.r.t |aligned_start|.
80  static void CalculateVMAlignedBoundaries(int64 start,
81                                           int64 size,
82                                           int64* aligned_start,
83                                           int64* aligned_size,
84                                           int32* offset);
85
86  // Map the file to memory, set data_ to that memory address. Return true on
87  // success, false on any kind of failure. This is a helper for Initialize().
88  bool MapFileRegionToMemory(const Region& region);
89
90  // Closes all open handles.
91  void CloseHandles();
92
93  File file_;
94  uint8* data_;
95  size_t length_;
96
97#if defined(OS_WIN)
98  win::ScopedHandle file_mapping_;
99  bool image_;  // Map as an image.
100#endif
101
102  DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
103};
104
105}  // namespace base
106
107#endif  // BASE_FILES_MEMORY_MAPPED_FILE_H_
108