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// Copyright 2021 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.
#include "pw_hdlc/wire_packet_parser.h"
#include "pw_bytes/endian.h"
#include "pw_checksum/crc32.h"
#include "pw_hdlc/decoder.h"
#include "pw_hdlc/internal/protocol.h"
namespace pw::hdlc {
bool WirePacketParser::Parse(ConstByteSpan packet) {
if (packet.size_bytes() < Frame::kMinContentSizeBytes) {
return false;
}
if (packet.front() != kFlag || packet.back() != kFlag) {
return false;
}
// Partially decode into a buffer with space only for the address and control
// fields of the frame. The decoder will verify the frame's FCS field.
std::array<std::byte, 16> buffer = {};
Decoder decoder(buffer);
Status status = Status::Unknown();
decoder.Process(packet, [&status](const Result<Frame>& result) {
status = result.status();
});
Result<Frame> result = Frame::Parse(buffer);
if (!result.ok()) {
return false;
}
address_ = result.value().address();
// RESOURCE_EXHAUSTED is expected as the buffer is too small for the packet.
return status.ok() || status.IsResourceExhausted();
}
} // namespace pw::hdlc
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