Function decode_payload

common/codex32.c:212–253

Helper to fetch data from payload as a valid hex buffer */

/* Helper to fetch data from payload as a valid hex buffer */
static const u8 *decode_payload(const tal_t *ctx, const char *payload, size_t payload_len)
{
	u8 *ret = tal_arr(ctx, u8, (payload_len * 5 + 7) / 8);
	uint8_t next_byte = 0;
	uint8_t rem = 0;
	size_t j = 0;

	/* We have already checked this is a valid bech32 string! */
	for (size_t i = 0; i < payload_len; i++) {
		int ch = payload[i];
		uint8_t fe = bech32_charset_rev[ch];

		if (rem < 3) {
			// If we are within 3 bits of the start we can fit the whole next char in
			next_byte |= fe << (3 - rem);
		}
		else if (rem == 3) {
			// If we are exactly 3 bits from the start then this char fills in the byte
			ret[j++] = next_byte | fe;
			next_byte = 0;
		}
		else { // rem > 3
			// Otherwise we have to break it in two
			u8 overshoot = rem - 3;
			assert(overshoot > 0);
			ret[j++] = next_byte | (fe >> overshoot);
			next_byte = fe << (8 - overshoot);
		}

		rem = (rem + 5) % 8;
	}

	/* BIP-93:
	 * Any incomplete group at the end MUST be 4 bits or less, and is discarded.
	 */
	if (rem > 4)
		return tal_free(ret);

	/* As a result, we often don't use the final byte */
	tal_resize(&ret, j);
	return ret;
}

/* Checks case inconsistency, and for non-bech32 chars. */
static const char *bech32_case_fixup(const tal_t *ctx,