Function fxCacheUnicodeToUTF8Offset

xs/sources/xsString.c:207–264

}

txSize fxCacheUnicodeToUTF8Offset(txMachine* the, txString string, txSize offset)
{
	txStringInfo* info;
	if (offset <= 0)
		return offset ? -1 : 0;	
	info = fxCacheStringInfo(the, string);
	if (info) {
		txSize delta, sign, unicodeOffset, utf8Offset;
		txU1* p;
		if ((offset < 0) || (info->unicodeLength < offset))
			return -1;
		if ((info->ascii) || (offset == 0))
			return offset;
		if (offset == info->unicodeLength)
			return info->utf8Length;
		delta = offset - info->unicodeOffset;
		if (delta == 0)
			return info->utf8Offset;
		if (delta > 0) {
			if (delta < info->unicodeLength - offset) {
				sign = 1;
				unicodeOffset = info->unicodeOffset + 1;
				utf8Offset = info->utf8Offset + 1;
			}
			else {
				sign = -1;
				unicodeOffset = info->unicodeLength - 1;
				utf8Offset = info->utf8Length - 1;
			}
		}
		else {
			if (0 - delta < offset) {
				sign = -1;
				unicodeOffset = info->unicodeOffset - 1;
				utf8Offset = info->utf8Offset - 1;
			}
			else {
				sign = 1;
				unicodeOffset = 1;
				utf8Offset = 1;
			}
		}
		p = (txU1*)string + utf8Offset;
		for (;;) {
			if ((*p & 0xC0) != 0x80) {
				if (unicodeOffset == offset)
					break;
				unicodeOffset += sign;
			}
			p += sign;
			utf8Offset += sign;
		}
		info->utf8Offset = utf8Offset;
		info->unicodeOffset = unicodeOffset;
		return utf8Offset;
	}
	return fxUnicodeToUTF8Offset(string, offset);
}