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102 lines
3.3 KiB
C++
102 lines
3.3 KiB
C++
// Copyright 2013 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_FILES_MEMORY_MAPPED_FILE_H_
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#define BASE_FILES_MEMORY_MAPPED_FILE_H_
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#include "base/base_export.h"
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#include "base/basictypes.h"
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#include "base/files/file.h"
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#include "build/build_config.h"
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#if defined(OS_WIN)
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#include <windows.h>
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#endif
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namespace base {
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class FilePath;
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class BASE_EXPORT MemoryMappedFile {
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public:
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// The default constructor sets all members to invalid/null values.
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MemoryMappedFile();
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~MemoryMappedFile();
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// Used to hold information about a region [offset + size] of a file.
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struct BASE_EXPORT Region {
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static const Region kWholeFile;
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bool operator==(const Region& other) const;
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bool operator!=(const Region& other) const;
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// Start of the region (measured in bytes from the beginning of the file).
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int64 offset;
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// Length of the region in bytes.
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int64 size;
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};
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// Opens an existing file and maps it into memory. Access is restricted to
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// read only. If this object already points to a valid memory mapped file
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// then this method will fail and return false. If it cannot open the file,
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// the file does not exist, or the memory mapping fails, it will return false.
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// Later we may want to allow the user to specify access.
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bool Initialize(const FilePath& file_name);
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// As above, but works with an already-opened file. MemoryMappedFile takes
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// ownership of |file| and closes it when done.
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bool Initialize(File file);
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// As above, but works with a region of an already-opened file.
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bool Initialize(File file, const Region& region);
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#if defined(OS_WIN)
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// Opens an existing file and maps it as an image section. Please refer to
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// the Initialize function above for additional information.
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bool InitializeAsImageSection(const FilePath& file_name);
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#endif // OS_WIN
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const uint8* data() const { return data_; }
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size_t length() const { return length_; }
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// Is file_ a valid file handle that points to an open, memory mapped file?
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bool IsValid() const;
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private:
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// Given the arbitrarily aligned memory region [start, size], returns the
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// boundaries of the region aligned to the granularity specified by the OS,
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// (a page on Linux, ~32k on Windows) as follows:
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// - |aligned_start| is page aligned and <= |start|.
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// - |aligned_size| is a multiple of the VM granularity and >= |size|.
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// - |offset| is the displacement of |start| w.r.t |aligned_start|.
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static void CalculateVMAlignedBoundaries(int64 start,
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int64 size,
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int64* aligned_start,
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int64* aligned_size,
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int32* offset);
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// Map the file to memory, set data_ to that memory address. Return true on
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// success, false on any kind of failure. This is a helper for Initialize().
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bool MapFileRegionToMemory(const Region& region);
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// Closes all open handles.
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void CloseHandles();
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File file_;
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uint8* data_;
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size_t length_;
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#if defined(OS_WIN)
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win::ScopedHandle file_mapping_;
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bool image_; // Map as an image.
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#endif
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DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
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};
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} // namespace base
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#endif // BASE_FILES_MEMORY_MAPPED_FILE_H_
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