ref: 6c2f8fd5e4f0e0be44495a5526930fa3760cd87e
dir: /libkern/utfnlen.c/
#include "lib9.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;
}