ref: 800334cb8d11b5fe1bd4ef40bdc53fac49a2ee21
dir: /sys/src/libc/port/utfrune.c/
#include <u.h>
#include <libc.h>
char*
utfrune(char *s, long c)
{
Rune r;
char buf[UTFmax + 1] = {0};
if(c < Runesync) /* not part of utf sequence */
return strchr(s, c);
r = c;
runetochar(buf, &r);
return strstr(s, buf);
}