Function GetTransaction

src/validation.cpp:1035–1072

* Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock. * If blockIndex is provided, the transaction is fetched from the corresponding block. */

 * If blockIndex is provided, the transaction is fetched from the corresponding block.
 */
bool GetTransaction(const uint256& hash, CTransactionRef& txOut, const Consensus::Params& consensusParams, uint256& hashBlock, bool fAllowSlow, CBlockIndex* blockIndex)
{
    CBlockIndex* pindexSlow = blockIndex;

    LOCK(cs_main);

    if (!blockIndex) {
        CTransactionRef ptx = mempool.get(hash);
        if (ptx) {
            txOut = ptx;
            return true;
        }

        if (g_txindex) {
            return g_txindex->FindTx(hash, hashBlock, txOut);
        }

        if (fAllowSlow) { // use coin database to locate block that contains transaction, and scan it
            const Coin& coin = AccessByTxid(*pcoinsTip, hash);
            if (!coin.IsSpent()) pindexSlow = chainActive[coin.nHeight];
        }
    }

    if (pindexSlow) {
        CBlock block;
        if (ReadBlockFromDisk(block, pindexSlow, consensusParams)) {
            for (const auto& tx : block.vtx) {
                if (tx->GetHash() == hash) {
                    txOut = tx;
                    hashBlock = pindexSlow->GetBlockHash();
                    return true;
                }
            }
        }
    }

    return false;
}