memory_mapped_file.h

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// Copyright (c) 2011, Google Inc.

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// memory_mapped_file.h: Define the google_breakpad::MemoryMappedFile

// class, which maps a file into memory for read-only access.

#ifndef COMMON_LINUX_MEMORY_MAPPED_FILE_H_

#define COMMON_LINUX_MEMORY_MAPPED_FILE_H_

#include <stddef.h>

#include "common/basictypes.h"

#include "common/memory_range.h"

namespace google_breakpad {

// A utility class for mapping a file into memory for read-only access of

// the file content. Its implementation avoids calling into libc functions

// by directly making system calls for open, close, mmap, and munmap.

class MemoryMappedFile {

 public:

  MemoryMappedFile();

  // Constructor that calls Map() to map a file at |path| into memory.

  // If Map() fails, the object behaves as if it is default constructed.

  MemoryMappedFile(const char* path, size_t offset);

  ~MemoryMappedFile();

  // Maps a file at |path| into memory, which can then be accessed via

  // content() as a MemoryRange object or via data(), and returns true on

  // success. Mapping an empty file will succeed but with data() and size()

  // returning NULL and 0, respectively. An existing mapping is unmapped

  // before a new mapping is created.

  bool Map(const char* path, size_t offset);

  // Unmaps the memory for the mapped file. It's a no-op if no file is

  // mapped.

  void Unmap();

  // Returns a MemoryRange object that covers the memory for the mapped

  // file. The MemoryRange object is empty if no file is mapped.

  const MemoryRange& content() const { return content_; }

  // Returns a pointer to the beginning of the memory for the mapped file.

  // or NULL if no file is mapped or the mapped file is empty.

  const void* data() const { return content_.data(); }

  // Returns the size in bytes of the mapped file, or zero if no file

  // is mapped.

  size_t size() const { return content_.length(); }

 private:

  // Mapped file content as a MemoryRange object.

  MemoryRange content_;

  DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);

};

}  // namespace google_breakpad

#endif  // COMMON_LINUX_MEMORY_MAPPED_FILE_H_