git: 9front

ref: c1f1d93079af2f3f06bd1ce06dc07b6ea33dfd62
dir: /sys/src/libc/port/utfnlen.c/

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#include <u.h>
#include <libc.h>

int
utfnlen(char *s, long m)
{
	int c;
	long n;
	Rune rune;
	char *es;

	es = s + m;
	for(n = 0; s < es; n++) {
		c = *(uchar*)s;
		if(c < Runeself){
			if(c == '\0')
				break;
			s++;
			continue;
		}
		if(!fullrune(s, es-s))
			break;
		s += chartorune(&rune, s);
	}
	return n;
}