base/files/memory_mapped_file.h

   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
  17 namespace base {
  18
  19 class FilePath;
  20
  21 class BASE_EXPORT MemoryMappedFile {
  22  public:
  23   // The default constructor sets all members to invalid/null values.
  24   MemoryMappedFile();
  25   ~MemoryMappedFile();
  26
  27   // Opens an existing file and maps it into memory. Access is restricted to
  28   // read only. If this object already points to a valid memory mapped file
  29   // then this method will fail and return false. If it cannot open the file,
  30   // the file does not exist, or the memory mapping fails, it will return false.
  31   // Later we may want to allow the user to specify access.
  32   bool Initialize(const FilePath& file_name);
  33
  34   // As above, but works with an already-opened file. MemoryMappedFile takes
  35   // ownership of |file| and closes it when done.
  36   bool Initialize(File file);
  37
  38 #if defined(OS_WIN)
  39   // Opens an existing file and maps it as an image section. Please refer to
  40   // the Initialize function above for additional information.
  41   bool InitializeAsImageSection(const FilePath& file_name);
  42 #endif  // OS_WIN
  43
  44   const uint8* data() const { return data_; }
  45   size_t length() const { return length_; }
  46
  47   // Is file_ a valid file handle that points to an open, memory mapped file?
  48   bool IsValid() const;
  49
  50  private:
  51   // Map the file to memory, set data_ to that memory address. Return true on
  52   // success, false on any kind of failure. This is a helper for Initialize().
  53   bool MapFileToMemory();
  54
  55   // Closes all open handles.
  56   void CloseHandles();
  57
  58   File file_;
  59   uint8* data_;
  60   size_t length_;
  61
  62 #if defined(OS_WIN)
  63   win::ScopedHandle file_mapping_;
  64   bool image_;  // Map as an image.
  65 #endif
  66
  67   DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
  68 };
  69
  70 }  // namespace base
  71
  72 #endif  // BASE_FILES_MEMORY_MAPPED_FILE_H_