Function testFcsMatchesLibmodem

tests/hdlc_codec_test.cpp:103–135

}

void testFcsMatchesLibmodem()
{
    lm::packet pkt("K5PTB", "BEACON", {"WIDE1-1"}, ">CRC cross-check");
    auto nrzi = makeNrziBitstream(pkt);

    // Break immediately when the frame closes so complete()/fcsValid() are
    // still true (they are reset at the start of the *next* processBit call).
    HdlcCodec codec;
    bool gotFrame = false;
    for (uint8_t bit : nrzi) {
        if (codec.processBit(bit)) {
            gotFrame = true;
            break;
        }
    }

    if (!gotFrame || !codec.fcsValid()) {
        report("FCS cross-check: codec decoded frame", false);
        return;
    }
    report("FCS cross-check: codec decoded frame", true);

    // libmodem's compute_crc over the frame body (excluding last 2 FCS bytes)
    auto span = std::span<const uint8_t>(codec.frameData(), codec.frameSize() - 2);
    auto libmodemFcs = lm::ax25::compute_crc(span.begin(), span.end());

    report("FCS cross-check: CRC low byte matches libmodem",
           codec.expectedFcs()[0] == libmodemFcs[0]);
    report("FCS cross-check: CRC high byte matches libmodem",
           codec.expectedFcs()[1] == libmodemFcs[1]);
    report("FCS cross-check: actual FCS == expected FCS",
           codec.actualFcs() == codec.expectedFcs());
}

void testBadFcs()
{