transport.py 文件源码

def read(self, timeout):
        if self.tty is not None:
            self.tty.timeout = max(timeout / 1000.0, 0.05)
            frame = bytearray(self.tty.read(6))
            if frame is None or len(frame) == 0:
                raise IOError(errno.ETIMEDOUT, os.strerror(errno.ETIMEDOUT))
            if frame.startswith("\x00\x00\xff\x00\xff\x00"):
                return frame
            LEN = frame[3]
            if LEN == 0xFF:
                frame += self.tty.read(3)
                LEN = frame[5]<<8 | frame[6]
            frame += self.tty.read(LEN + 1)
            log.debug("<<< " + str(frame).encode("hex"))
            return frame