Function DecodeTx

src/core_io.cpp:154–223

}

static bool DecodeTx(CMutableTransaction& tx, const std::vector<unsigned char>& tx_data, bool try_no_witness, bool try_witness)
{
    // General strategy:
    // - Decode both with extended serialization (which interprets the 0x0001 tag as a marker for
    //   the presence of witnesses) and with legacy serialization (which interprets the tag as a
    //   0-input 1-output incomplete transaction).
    //   - Restricted by try_no_witness (which disables legacy if false) and try_witness (which
    //     disables extended if false).
    //   - Ignore serializations that do not fully consume the hex string.
    // - If neither succeeds, fail.
    // - If only one succeeds, return that one.
    // - If both decode attempts succeed:
    //   - If only one passes the CheckTxScriptsSanity check, return that one.
    //   - If neither or both pass CheckTxScriptsSanity, return the extended one.

    CMutableTransaction tx_extended, tx_legacy;
    bool ok_extended = false, ok_legacy = false;

    // Try decoding with extended serialization support, and remember if the result successfully
    // consumes the entire input.
    if (try_witness) {
        SpanReader ssData{tx_data};
        try {
            ssData >> TX_WITH_WITNESS(tx_extended);
            if (ssData.empty()) ok_extended = true;
        } catch (const std::exception&) {
            // Fall through.
        }
    }

    // Optimization: if extended decoding succeeded and the result passes CheckTxScriptsSanity,
    // don't bother decoding the other way.
    if (ok_extended && CheckTxScriptsSanity(tx_extended)) {
        tx = std::move(tx_extended);
        return true;
    }

    // Try decoding with legacy serialization, and remember if the result successfully consumes the entire input.
    if (try_no_witness) {
        SpanReader ssData{tx_data};
        try {
            ssData >> TX_NO_WITNESS(tx_legacy);
            if (ssData.empty()) ok_legacy = true;
        } catch (const std::exception&) {
            // Fall through.
        }
    }

    // If legacy decoding succeeded and passes CheckTxScriptsSanity, that's our answer, as we know
    // at this point that extended decoding either failed or doesn't pass the sanity check.
    if (ok_legacy && CheckTxScriptsSanity(tx_legacy)) {
        tx = std::move(tx_legacy);
        return true;
    }

    // If extended decoding succeeded, and neither decoding passes sanity, return the extended one.
    if (ok_extended) {
        tx = std::move(tx_extended);