Function utf8_encode

ccan/ccan/utf8/utf8.c:136–178

}

size_t utf8_encode(uint32_t point, char dest[UTF8_MAX_LEN])
{
	if ((point >> 7) == 0) {
		if (point == 0) {
			errno = ERANGE;
			return 0;
		}
		/* 0xxxxxxx */
		dest[0] = point;
		return 1;
	}

	if ((point >> 11) == 0) {
		/* 110xxxxx 10xxxxxx */
		dest[1] = 0x80 | (point & 0x3F);
		dest[0] = 0xC0 | (point >> 6);
		return 2;
	}

	if ((point >> 16) == 0) {
		if (point >= 0xD800 && point <= 0xDFFF) {
			errno = ERANGE;
			return 0;
		}
		/* 1110xxxx 10xxxxxx 10xxxxxx */
		dest[2] = 0x80 | (point & 0x3F);
		dest[1] = 0x80 | ((point >> 6) & 0x3F);
		dest[0] = 0xE0 | (point >> 12);
		return 3;
	}

	if (point > 0x10FFFF) {
		errno = ERANGE;
		return 0;
	}

	/* 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
	dest[3] = 0x80 | (point & 0x3F);
	dest[2] = 0x80 | ((point >> 6) & 0x3F);
	dest[1] = 0x80 | ((point >> 12) & 0x3F);
	dest[0] = 0xF0 | (point >> 18);
	return 4;
}