# PrecomputedTransactionData Cached per-transaction data that speeds up repeated script verification — most importantly, the BIP-341 sighash components a taproot spend uses (`hashPrevouts`, `hashAmounts`, `hashScriptPubkeys`, `hashSequences`, `hashOutputs`) that would otherwise be recomputed for every input. ``` final class PrecomputedTransactionData ``` ## Overview Construct once per transaction, then reuse across every [`verify(amount:transaction:precomputedData:inputIndex:flags:)`](/documentation/BitcoinKernel/ScriptPubkey/verify(amount:transaction:precomputedData:inputIndex:flags:)) call for that transaction. For non-taproot verification the `spentOutputs` argument is optional; for taproot it is required. Wraps the opaque `btck_PrecomputedTransactionData` type; `deinit` calls `btck_precomputed_transaction_data_destroy` when the last Swift reference drops.