1 files changed, 29 insertions, 0 deletions
diff --git a/pw_hdlc/py/pw_hdlc/encode.py b/pw_hdlc/py/pw_hdlc/encode.py
new file mode 100644
index 000000000..ceede92da
--- /dev/null
+++ b/pw_hdlc/py/pw_hdlc/encode.py
@@ -0,0 +1,29 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+"""The encode module supports encoding HDLC frames."""
+
+from pw_hdlc import protocol
+
+_ESCAPE_BYTE = bytes([protocol.ESCAPE])
+_FLAG_BYTE = bytes([protocol.FLAG])
+
+
+def ui_frame(address: int, data: bytes) -> bytes:
+    """Encodes an HDLC UI-frame with a CRC-32 frame check sequence."""
+    frame = protocol.encode_address(
+        address) + protocol.UFrameControl.unnumbered_information().data + data
+    frame += protocol.frame_check_sequence(frame)
+    frame = frame.replace(_ESCAPE_BYTE, b'\x7d\x5d')
+    frame = frame.replace(_FLAG_BYTE, b'\x7d\x5e')
+    return b''.join([_FLAG_BYTE, frame, _FLAG_BYTE])