英语翻译，用的PCOMM库，如果读取的数据比定义的长度小，会怎么样

If the length of data in the driver's input buffer is less than the buffer defined for sio_read(), all data in the driver's input buffer will be transferred to that of sio_read(). Otherwise, sio_read() reads specified length bytes from the driver's input buffer.

如果设备输入缓存区比sio_read()中定义的缓存区要小，那么设备输入缓冲区的内容（数据）将要被迁移到sio_read()定义的缓冲区中。否则，sio_read()要从设备缓存区中读取固定长度字节的数据。