Method Init

src/script/interpreter.cpp:1413–1462

template <class T>
void PrecomputedTransactionData::Init(const T& txTo, std::vector<CTxOut>&& spent_outputs, bool force)
{
    assert(!m_spent_outputs_ready);

    m_spent_outputs = std::move(spent_outputs);
    if (!m_spent_outputs.empty()) {
        assert(m_spent_outputs.size() == txTo.vin.size());
        m_spent_outputs_ready = true;
    }

    // Determine which precomputation-impacting features this transaction uses.
    bool uses_bip143_segwit = force;
    bool uses_bip341_taproot = force;
    for (size_t inpos = 0; inpos < txTo.vin.size() && !(uses_bip143_segwit && uses_bip341_taproot); ++inpos) {
        if (!txTo.vin[inpos].scriptWitness.IsNull()) {
            if (m_spent_outputs_ready && m_spent_outputs[inpos].scriptPubKey.size() == 2 + WITNESS_V1_TAPROOT_SIZE &&
                m_spent_outputs[inpos].scriptPubKey[0] == OP_1) {
                // Treat every witness-bearing spend with 34-byte scriptPubKey that starts with OP_1 as a Taproot
                // spend. This only works if spent_outputs was provided as well, but if it wasn't, actual validation
                // will fail anyway. Note that this branch may trigger for scriptPubKeys that aren't actually segwit
                // but in that case validation will fail as SCRIPT_ERR_WITNESS_UNEXPECTED anyway.
                uses_bip341_taproot = true;
            } else {
                // Treat every spend that's not known to native witness v1 as a Witness v0 spend. This branch may
                // also be taken for unknown witness versions, but it is harmless, and being precise would require
                // P2SH evaluation to find the redeemScript.
                uses_bip143_segwit = true;
            }
        }
        if (uses_bip341_taproot && uses_bip143_segwit) break; // No need to scan further if we already need all.
    }

    if (uses_bip143_segwit || uses_bip341_taproot) {
        // Computations shared between both sighash schemes.
        m_prevouts_single_hash = GetPrevoutsSHA256(txTo);
        m_sequences_single_hash = GetSequencesSHA256(txTo);
        m_outputs_single_hash = GetOutputsSHA256(txTo);
    }
    if (uses_bip143_segwit) {
        hashPrevouts = SHA256Uint256(m_prevouts_single_hash);
        hashSequence = SHA256Uint256(m_sequences_single_hash);
        hashOutputs = SHA256Uint256(m_outputs_single_hash);
        m_bip143_segwit_ready = true;
    }
    if (uses_bip341_taproot && m_spent_outputs_ready) {
        m_spent_amounts_single_hash = GetSpentAmountsSHA256(m_spent_outputs);
        m_spent_scripts_single_hash = GetSpentScriptsSHA256(m_spent_outputs);
        m_bip341_taproot_ready = true;
    }
}

template <class T>
PrecomputedTransactionData::PrecomputedTransactionData(const T& txTo)