Function decode_9

common/bolt11.c:559–605

BOLT #11: * * `9` (5): `data_length` variable. One or more 5-bit values containing features * supported or required for receiving this payment. * See [Feature Bits](#feature-bits). */

 *  See [Feature Bits](#feature-bits).
 */
static const char *decode_9(struct bolt11 *b11,
			    const struct feature_set *our_features,
			    struct hash_u5 *hu5,
			    const u5 **data, size_t *field_len,
			    bool *have_9)
{
	size_t flen = (*field_len * 5 + 7) / 8;
	int badf;
	size_t databits = *field_len * 5;
	const char *err;

	assert(!*have_9);

	b11->features = pull_all(b11, hu5, data, field_len, true, &err);
	if (!b11->features)
		return err;

	/* BOLT #11:
	 *   - if a `c`, `x`, or `9` field is provided which has a non-minimal `data_length`
	 *     (i.e. begins with 0 field elements):
	 *   - SHOULD treat the invoice as invalid.
	 */
	if (tal_count(b11->features) > 0 && b11->features[0] == 0)
		return tal_fmt(b11, "9: non-minimal length (begins with 0)");

	/* pull_bits pads with zero bits: we need to remove them. */
	shift_bitmap_down(b11->features,
			  flen * 8 - databits);

	/* BOLT #11:
	 *
	 * - if the `9` field contains unknown _odd_ bits that are non-zero:
	 *   - MUST ignore the bit.
	 * - if the `9` field contains unknown _even_ bits that are non-zero:
	 *   - MUST fail the payment.
	 */
	/* We skip this check for the cli tool, which sets our_features to NULL */
	if (our_features) {
		badf = features_unsupported(our_features,
					    b11->features, BOLT11_FEATURE);
		if (badf != -1)
			return tal_fmt(b11, "9: unknown feature bit %i", badf);
	}

	*have_9 = true;
	return NULL;
}

/* BOLT #11:
 *