utfnlen.c - 9base - revived minimalist port of Plan 9 userland to Unix
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       utfnlen.c (1111B)
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            1 /*
            2  * The authors of this software are Rob Pike and Ken Thompson.
            3  *              Copyright (c) 2002 by Lucent Technologies.
            4  * Permission to use, copy, modify, and distribute this software for any
            5  * purpose without fee is hereby granted, provided that this entire notice
            6  * is included in all copies of any software which is or includes a copy
            7  * or modification of this software and in all copies of the supporting
            8  * documentation for such software.
            9  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
           10  * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
           11  * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
           12  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
           13  */
           14 #include <stdarg.h>
           15 #include <string.h>
           16 #include "plan9.h"
           17 #include "utf.h"
           18 
           19 int
           20 utfnlen(char *s, long m)
           21 {
           22         int c;
           23         long n;
           24         Rune rune;
           25         char *es;
           26 
           27         es = s + m;
           28         for(n = 0; s < es; n++) {
           29                 c = *(uchar*)s;
           30                 if(c < Runeself){
           31                         if(c == '\0')
           32                                 break;
           33                         s++;
           34                         continue;
           35                 }
           36                 if(!fullrune(s, es-s))
           37                         break;
           38                 s += chartorune(&rune, s);
           39         }
           40         return n;
           41 }