Function psbt_fixup

wallet/psbt_fixup.c:152–185

I am deeply, deeply unhappy with this code. I initially tried parsing the * entire PSBT, but that turns out not to be possible without decoding the * tranaction. Literally WTF */

 * entire PSBT, but that turns out not to be possible without decoding the
 * tranaction.  Literally WTF */
const u8 *psbt_fixup(const tal_t *ctx, const u8 *psbtblob)
{
	const u8 *prev_cursor, *cursor = psbtblob;
	size_t max = tal_bytelen(psbtblob);
	u8 *ret;
	struct keypair *kp, *changed_kp;

	/* Skip magic */
	fromwire_pad(&cursor, &max, 5);

	/* Skip global map */
	while ((kp = fromwire_keypair(tmpctx, &cursor, &max)) != NULL);

	/* Now input map */
	changed_kp = NULL;
	prev_cursor = cursor;
	while ((kp = fromwire_keypair(tmpctx, &cursor, &max)) != NULL) {
		/* PSBT_IN_PARTIAL_SIG = 0x02 */
		if (kp->keytype == 2 && fixup_sig(kp)) {
			changed_kp = kp;
			break;
		}
		prev_cursor = cursor;
	}

	if (!changed_kp)
		return NULL;

	ret = tal_dup_arr(ctx, u8, psbtblob, prev_cursor - psbtblob, 0);
	towire_keypair(&ret, changed_kp);
	towire_u8_array(&ret, cursor, max);

	return ret;
}