Method DisconnectBlock

src/validation.cpp:1901–1960

Undo the effects of this block (with given index) on the UTXO set represented by coins. * When FAILED is returned, view is left in an indeterminate state. */

/** Undo the effects of this block (with given index) on the UTXO set represented by coins.
 *  When FAILED is returned, view is left in an indeterminate state. */
DisconnectResult CChainState::DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)
{
    AssertLockHeld(::cs_main);
    bool fClean = true;

    CBlockUndo blockUndo;
    if (!UndoReadFromDisk(blockUndo, pindex)) {
        error("DisconnectBlock(): failure reading undo data");
        return DISCONNECT_FAILED;
    }

    if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
        error("DisconnectBlock(): block and undo data inconsistent");
        return DISCONNECT_FAILED;
    }

    // undo transactions in reverse order
    for (int i = block.vtx.size() - 1; i >= 0; i--) {
        const CTransaction &tx = *(block.vtx[i]);
        uint256 hash = tx.GetHash();
        bool is_coinbase = tx.IsCoinBase();

        // Check that all outputs are available and match the outputs in the block itself
        // exactly.
        for (size_t o = 0; o < tx.vout.size(); o++) {
            if (!tx.vout[o].scriptPubKey.IsUnspendable()) {
                COutPoint out(hash, o);
                Coin coin;
                bool is_spent = view.SpendCoin(out, &coin);
                if (!is_spent || !TxOutDBEntryIsSame(tx.vout[o], coin.out) || pindex->nHeight != coin.nHeight || is_coinbase != coin.fCoinBase) {
                    fClean = false; // transaction output mismatch
                }
            }
        }

        // restore inputs
        const auto& fedpegscripts = GetValidFedpegScripts(pindex, Params().GetConsensus(), false /* nextblock_validation */);
        if (i > 0) { // not coinbases
            CTxUndo &txundo = blockUndo.vtxundo[i-1];
            if (txundo.vprevout.size() != tx.vin.size()) {
                error("DisconnectBlock(): transaction and undo data inconsistent");
                return DISCONNECT_FAILED;
            }
            for (unsigned int j = tx.vin.size(); j > 0;) {
                --j;
                const COutPoint& out = tx.vin[j].prevout;
                const CScriptWitness& pegin_wit = tx.witness.vtxinwit.size() > j ? tx.witness.vtxinwit[j].m_pegin_witness : CScriptWitness();
                int res = ApplyTxInUndo(std::move(txundo.vprevout[j]), view, out, tx.vin[j], pegin_wit, fedpegscripts);
                if (res == DISCONNECT_FAILED) return DISCONNECT_FAILED;
                fClean = fClean && res != DISCONNECT_UNCLEAN;
            }
            // At this point, all of txundo.vprevout should have been moved out.
        }
    }

    // move best block pointer to prevout block
    view.SetBestBlock(pindex->pprev->GetBlockHash());