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expandm.c revision 1.2 
      1 /*	$NetBSD: expandm.c,v 1.2 2019/01/12 19:08:24 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2018 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Christos Zoulas.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 #include <sys/cdefs.h>
     32 __RCSID("$NetBSD: expandm.c,v 1.2 2019/01/12 19:08:24 christos Exp $");
     33 
     34 #include <stdio.h>
     35 #include <string.h>
     36 #include <stdlib.h>
     37 #include <errno.h>
     38 
     39 #include "expandm.h"
     40 
     41 char * __attribute__((__format_arg__(1)))
     42 expandm(const char *fmt, const char *sf, char **rbuf)
     43 {
     44 	const char *e = strerror(errno);
     45 	char *buf, *m, *nbuf;
     46 	const char *ptr;
     47 
     48 	for (ptr = fmt, buf = NULL; (m = strstr(ptr, "%m")) != NULL;
     49 	    ptr = m + 2)
     50 	{
     51 		size_t cnt = 0;
     52 		for (char *p = m; p >= ptr && *p == '%'; p--)
     53 			cnt++;
     54 		if (asprintf(&nbuf, "%s%.*s%s", buf ? buf : "",
     55 		    (int)(m - ptr), ptr, (cnt & 1) ? e : "%%m") == -1)
     56 			goto out;
     57 		free(buf);
     58 		buf = nbuf;
     59 	}
     60 
     61 	if (asprintf(&nbuf, "%s%s%s", buf ? buf : "", ptr, sf ? sf : "") == -1)
     62 		goto out;
     63 
     64 	free(buf);
     65 	if (rbuf)
     66 		*rbuf = buf;
     67 	return nbuf;
     68 out:
     69 	free(buf);
     70 	if (rbuf)
     71 		*rbuf = NULL;
     72 	return __UNCONST(fmt);
     73 }
     74 
     75 #ifdef TEST
     76 int
     77 main(int argc, char *argv[])
     78 {
     79 	errno = ERANGE;
     80 	printf("%s\n", expandm(argv[1], "", NULL));
     81 	return 0;
     82 }
     83 #endif
     84