ref: dd16eef8365cb0b9e4805c23291aadcaa596dd87
dir: /lib9/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; }