static lzw_result lzw__block_advance(struct lzw_read_ctx *ctx)
{
	uint64_t block_size;
	uint64_t next_block_pos = ctx->data_sb_next;
	const uint8_t *data_next = ctx->data + next_block_pos;

	if (next_block_pos >= ctx->data_len) {
		return LZW_NO_DATA;
	}

	block_size = *data_next;

	if ((next_block_pos + block_size) >= ctx->data_len) {
		return LZW_NO_DATA;
	}

	ctx->sb_bit = 0;
	ctx->sb_bit_count = block_size * 8;

	if (block_size == 0) {
		ctx->data_sb_next += 1;
		return LZW_OK_EOD;
	}

	ctx->sb_data = data_next + 1;
	ctx->data_sb_next += block_size + 1;

	return LZW_OK;
}