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// 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/files/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();
// Used to hold information about a region [offset + size] of a file.
struct BASE_EXPORT Region {
static const Region kWholeFile;
Region(int64 offset, int64 size);
bool operator==(const Region& other) const;
// Start of the region (measured in bytes from the beginning of the file).
int64 offset;
// Length of the region in bytes.
int64 size;
private:
// This ctor is used only by kWholeFile, to construct a zero-sized Region
// (which is forbidden by the public ctor) and uniquely identify kWholeFile.
Region();
};
// 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 takes
// ownership of |file| and closes it when done.
bool Initialize(File file);
// As above, but works with a region of an already-opened file.
bool Initialize(File file, const Region& region);
#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:
// Given the arbitrarily aligned memory region [start, size], returns the
// boundaries of the region aligned to the granularity specified by the OS,
// (a page on Linux, ~32k on Windows) as follows:
// - |aligned_start| is page aligned and <= |start|.
// - |aligned_size| is a multiple of the VM granularity and >= |size|.
// - |offset| is the displacement of |start| w.r.t |aligned_start|.
static void CalculateVMAlignedBoundaries(int64 start,
int64 size,
int64* aligned_start,
int64* aligned_size,
int32* offset);
// 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 MapFileRegionToMemory(const Region& region);
// Closes all open handles.
void CloseHandles();
File file_;
uint8* data_;
size_t length_;
#if defined(OS_WIN)
win::ScopedHandle file_mapping_;
bool image_; // Map as an image.
#endif
DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
};
} // namespace base
#endif // BASE_FILES_MEMORY_MAPPED_FILE_H_