ref: 0e0e474915d2dcf8193f27c5491cd6c1502fc23b
dir: /3rd/utf/utfnlen.c/
#include "platform.h" int utfnlen(const char *s, long m) { int c; long n; Rune rune; const 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; }