1 // Copyright 2021 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 15 #include "pw_hdlc/wire_packet_parser.h" 16 17 #include "pw_bytes/endian.h" 18 #include "pw_checksum/crc32.h" 19 #include "pw_hdlc/decoder.h" 20 #include "pw_hdlc/internal/protocol.h" 21 22 namespace pw::hdlc { 23 Parse(ConstByteSpan packet)24bool WirePacketParser::Parse(ConstByteSpan packet) { 25 if (packet.size_bytes() < Frame::kMinSizeBytes) { 26 return false; 27 } 28 29 if (packet.front() != kFlag || packet.back() != kFlag) { 30 return false; 31 } 32 33 // Partially decode into a buffer with space only for the address and control 34 // fields of the frame. The decoder will verify the frame's FCS field. 35 std::array<std::byte, 16> buffer = {}; 36 Decoder decoder(buffer); 37 Status status = Status::Unknown(); 38 39 decoder.Process(packet, [&status](const Result<Frame>& result) { 40 status = result.status(); 41 }); 42 43 Result<Frame> result = Frame::Parse(buffer); 44 if (!result.ok()) { 45 return false; 46 } 47 48 address_ = result.value().address(); 49 50 // RESOURCE_EXHAUSTED is expected as the buffer is too small for the packet. 51 return status.ok() || status.IsResourceExhausted(); 52 } 53 54 } // namespace pw::hdlc 55