mapped_struct.py 文件源码

def map_file(cls, fileobj, offset = 0, size = None):
        fileobj.seek(offset)
        total_size = cls._Header.unpack(fileobj.read(cls._Header.size))[0]
        map_start = offset - offset % mmap.ALLOCATIONGRANULARITY
        buf = mmap.mmap(fileobj.fileno(), total_size + offset - map_start, 
            access = mmap.ACCESS_READ, offset = map_start)
        rv = cls(buffer(buf, offset - map_start))
        rv._file = fileobj
        rv._mmap = buf
        return rv