1# Copyright 2020 The Pigweed Authors 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); you may not 4# use this file except in compliance with the License. You may obtain a copy of 5# the License at 6# 7# https://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12# License for the specific language governing permissions and limitations under 13# the License. 14"""The encode module supports encoding HDLC frames.""" 15 16from pw_hdlc import protocol 17 18_ESCAPE_BYTE = bytes([protocol.ESCAPE]) 19_FLAG_BYTE = bytes([protocol.FLAG]) 20 21 22def ui_frame(address: int, data: bytes) -> bytes: 23 """Encodes an HDLC UI-frame with a CRC-32 frame check sequence.""" 24 frame = ( 25 protocol.encode_address(address) 26 + protocol.UFrameControl.unnumbered_information().data 27 + data 28 ) 29 frame += protocol.frame_check_sequence(frame) 30 frame = frame.replace(_ESCAPE_BYTE, b'\x7d\x5d') 31 frame = frame.replace(_FLAG_BYTE, b'\x7d\x5e') 32 return b''.join([_FLAG_BYTE, frame, _FLAG_BYTE]) 33