xref: /plan9/sys/src/ape/lib/utf/utfrune.c (revision b85a83648eec38fe82b6f00adfd7828ceec5ee8d)
1*40ef9009SDavid du Colombier /*
2*40ef9009SDavid du Colombier  * The authors of this software are Rob Pike and Ken Thompson.
3*40ef9009SDavid du Colombier  *              Copyright (c) 2002 by Lucent Technologies.
4*40ef9009SDavid du Colombier  * Permission to use, copy, modify, and distribute this software for any
5*40ef9009SDavid du Colombier  * purpose without fee is hereby granted, provided that this entire notice
6*40ef9009SDavid du Colombier  * is included in all copies of any software which is or includes a copy
7*40ef9009SDavid du Colombier  * or modification of this software and in all copies of the supporting
8*40ef9009SDavid du Colombier  * documentation for such software.
9*40ef9009SDavid du Colombier  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
10*40ef9009SDavid du Colombier  * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
11*40ef9009SDavid du Colombier  * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
12*40ef9009SDavid du Colombier  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
13*40ef9009SDavid du Colombier  */
14*40ef9009SDavid du Colombier #include <stdarg.h>
15*40ef9009SDavid du Colombier #include <string.h>
16*40ef9009SDavid du Colombier #include "utf.h"
17*40ef9009SDavid du Colombier #include "utfdef.h"
18*40ef9009SDavid du Colombier 
19*40ef9009SDavid du Colombier char*
utfrune(char * s,long c)20*40ef9009SDavid du Colombier utfrune(char *s, long c)
21*40ef9009SDavid du Colombier {
22*40ef9009SDavid du Colombier 	long c1;
23*40ef9009SDavid du Colombier 	Rune r;
24*40ef9009SDavid du Colombier 	int n;
25*40ef9009SDavid du Colombier 
26*40ef9009SDavid du Colombier 	if(c < Runesync)		/* not part of utf sequence */
27*40ef9009SDavid du Colombier 		return strchr(s, c);
28*40ef9009SDavid du Colombier 
29*40ef9009SDavid du Colombier 	for(;;) {
30*40ef9009SDavid du Colombier 		c1 = *(uchar*)s;
31*40ef9009SDavid du Colombier 		if(c1 < Runeself) {	/* one byte rune */
32*40ef9009SDavid du Colombier 			if(c1 == 0)
33*40ef9009SDavid du Colombier 				return 0;
34*40ef9009SDavid du Colombier 			if(c1 == c)
35*40ef9009SDavid du Colombier 				return s;
36*40ef9009SDavid du Colombier 			s++;
37*40ef9009SDavid du Colombier 			continue;
38*40ef9009SDavid du Colombier 		}
39*40ef9009SDavid du Colombier 		n = chartorune(&r, s);
40*40ef9009SDavid du Colombier 		if(r == c)
41*40ef9009SDavid du Colombier 			return s;
42*40ef9009SDavid du Colombier 		s += n;
43*40ef9009SDavid du Colombier 	}
44*40ef9009SDavid du Colombier }
45