/// @param map_writable If true, the file will be mapped in r/w such
/// that changes to the mapped buffer will be flushed back
/// to the file. If false, the file will be mapped read-only
/// and the buffer will be read-only.
/// @param result Set to the start address of the mapped buffer.
/// @param map_writable If true, the file will be mapped in r/w such
/// that changes to the mapped buffer will be flushed back
/// to the file. If false, the file will be mapped read-only
/// and the buffer will be read-only.
/// @param result Set to the start address of the mapped buffer.