PacketFramingStream.py 文件源码

def seek(self, offset, whence=SEEK_SET):
        "Adjust seek from prefix start and, if present, from prefix"
        if not self._rawStreamSize() >= (self.PREFIX_SIZE + self.SUFFIX_SIZE):
            return
        if whence == SEEK_SET:
            offset += self._prefixStart + self.PREFIX_SIZE
            return self._stream.seek(offset, whence)
        elif whence == SEEK_CUR:
            return self._stream.seek(offset, whence)
        elif whence == SEEK_END:
            # even if the suffix hasn't been received yet, we calculate our offsets as if it had.
            # why? because if it hasn't been received yet, we don't want to finish! The whole packet
            # isn't framed (verified) until the final bytes are received.
            offset = offset - self.SUFFIX_SIZE
            return self._stream.seek(offset, whence)