Function elements_tx_add_fee_output

bitcoin/tx.c:157–178

* Add an explicit fee output if necessary. * * An explicit fee output is only necessary if we are using an elements * transaction, and we have a non-zero fee. This method may be called multiple * times. * * Returns the position of the fee output, or -1 in the case of non-elements * transactions. */

 * transactions.
 */
static int elements_tx_add_fee_output(struct bitcoin_tx *tx)
{
	struct amount_sat fee = bitcoin_tx_compute_fee(tx);
	int pos;

	/* If we aren't using elements, we don't add explicit fee outputs */
	if (!chainparams->is_elements)
		return -1;

	/* Try to find any existing fee output */
	for (pos = 0; pos < tx->wtx->num_outputs; pos++) {
		if (elements_tx_output_is_fee(tx, pos))
			break;
	}

	if (pos == tx->wtx->num_outputs)
		return bitcoin_tx_add_output(tx, NULL, NULL, fee);
	else {
		bitcoin_tx_output_set_amount(tx, pos, fee);
		return pos;
	}
}

void bitcoin_tx_set_locktime(struct bitcoin_tx *tx, u32 locktime)
{