base: Move MemoryMappedFile out of file_util.h and into its own header file.

base/files/memory_mapped_file.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_FILES_MEMORY_MAPPED_FILE_H_
+#define BASE_FILES_MEMORY_MAPPED_FILE_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/platform_file.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+namespace base {
+
+class FilePath;
+
+class BASE_EXPORT MemoryMappedFile {
+ public:
+  // The default constructor sets all members to invalid/null values.
+  MemoryMappedFile();
+  ~MemoryMappedFile();
+
+  // Opens an existing file and maps it into memory. Access is restricted to
+  // read only. If this object already points to a valid memory mapped file
+  // then this method will fail and return false. If it cannot open the file,
+  // the file does not exist, or the memory mapping fails, it will return false.
+  // Later we may want to allow the user to specify access.
+  bool Initialize(const FilePath& file_name);
+  // As above, but works with an already-opened file. MemoryMappedFile will take
+  // ownership of |file| and close it when done.
+  bool Initialize(PlatformFile file);
+
+#if defined(OS_WIN)
+  // Opens an existing file and maps it as an image section. Please refer to
+  // the Initialize function above for additional information.
+  bool InitializeAsImageSection(const FilePath& file_name);
+#endif  // OS_WIN
+
+  const uint8* data() const { return data_; }
+  size_t length() const { return length_; }
+
+  // Is file_ a valid file handle that points to an open, memory mapped file?
+  bool IsValid() const;
+
+ private:
+  // Open the given file and pass it to MapFileToMemoryInternal().
+  bool MapFileToMemory(const FilePath& file_name);
+
+  // Map the file to memory, set data_ to that memory address. Return true on
+  // success, false on any kind of failure. This is a helper for Initialize().
+  bool MapFileToMemoryInternal();
+
+  // Closes all open handles. Later we may want to make this public.
+  void CloseHandles();
+
+#if defined(OS_WIN)
+  // MapFileToMemoryInternal calls this function. It provides the ability to
+  // pass in flags which control the mapped section.
+  bool MapFileToMemoryInternalEx(int flags);
+
+  HANDLE file_mapping_;
+#endif
+  PlatformFile file_;
+  uint8* data_;
+  size_t length_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
+};
+
+}  // namespace base
+
+#endif  // BASE_FILES_MEMORY_MAPPED_FILE_H_