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      1 /* $xMach: strnsubst.c,v 1.3 2002/02/23 02:10:24 jmallett Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2002 J. Mallett.  All rights reserved.
      5  * You may do whatever you want with this file as long as
      6  * the above copyright and this notice remain intact, along
      7  * with the following statement:
      8  * 	For the man who taught me vi, and who got too old, too young.
      9  */
     10 
     11 #include <sys/cdefs.h>
     12 #ifndef lint
     13 #if 0
     14 __FBSDID("$FreeBSD: src/usr.bin/xargs/strnsubst.c,v 1.8 2005/12/30 23:22:50 jmallett Exp $");
     15 #endif
     16 __RCSID("$NetBSD: strnsubst.c,v 1.1 2007/04/18 15:56:07 christos Exp $");
     17 #endif /* not lint */
     18 
     19 #include <err.h>
     20 #include <stdlib.h>
     21 #include <string.h>
     22 #include <unistd.h>
     23 #include <stdint.h>
     24 
     25 void	strnsubst(char **, const char *, const char *, size_t);
     26 
     27 /*
     28  * Replaces str with a string consisting of str with match replaced with
     29  * replstr as many times as can be done before the constructed string is
     30  * maxsize bytes large.  It does not free the string pointed to by str, it
     31  * is up to the calling program to be sure that the original contents of
     32  * str as well as the new contents are handled in an appropriate manner.
     33  * If replstr is NULL, then that internally is changed to a nil-string, so
     34  * that we can still pretend to do somewhat meaningful substitution.
     35  * No value is returned.
     36  */
     37 void
     38 strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
     39 {
     40 	char *s1, *s2, *this;
     41 
     42 	s1 = *str;
     43 	if (s1 == NULL)
     44 		return;
     45 	/*
     46 	 * If maxsize is 0 then set it to to the length of s1, because we have
     47 	 * to duplicate s1.  XXX we maybe should double-check whether the match
     48 	 * appears in s1.  If it doesn't, then we also have to set the length
     49 	 * to the length of s1, to avoid modifying the argument.  It may make
     50 	 * sense to check if maxsize is <= strlen(s1), because in that case we
     51 	 * want to return the unmodified string, too.
     52 	 */
     53 	if (maxsize == 0) {
     54 		match = NULL;
     55 		maxsize = strlen(s1) + 1;
     56 	}
     57 	s2 = calloc(maxsize, 1);
     58 	if (s2 == NULL)
     59 		err(1, "calloc");
     60 
     61 	if (replstr == NULL)
     62 		replstr = "";
     63 
     64 	if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
     65 		(void)strlcpy(s2, s1, maxsize);
     66 		goto done;
     67 	}
     68 
     69 	for (;;) {
     70 		this = strstr(s1, match);
     71 		if (this == NULL)
     72 			break;
     73 		if ((strlen(s2) + strlen(s1) + strlen(replstr) -
     74 		    strlen(match) + 1) > maxsize) {
     75 			(void)strlcat(s2, s1, maxsize);
     76 			goto done;
     77 		}
     78 		(void)strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
     79 		(void)strcat(s2, replstr);
     80 		s1 = this + strlen(match);
     81 	}
     82 	(void)strcat(s2, s1);
     83 done:
     84 	*str = s2;
     85 	return;
     86 }
     87 
     88 #ifdef TEST
     89 #include <stdio.h>
     90 
     91 int
     92 main(void)
     93 {
     94 	char *x, *y, *z, *za;
     95 
     96 	x = "{}%$";
     97 	strnsubst(&x, "%$", "{} enpury!", 255);
     98 	y = x;
     99 	strnsubst(&y, "}{}", "ybir", 255);
    100 	z = y;
    101 	strnsubst(&z, "{", "v ", 255);
    102 	za = z;
    103 	strnsubst(&z, NULL, za, 255);
    104 	if (strcmp(z, "v ybir enpury!") == 0)
    105 		(void)printf("strnsubst() seems to work!\n");
    106 	else
    107 		(void)printf("strnsubst() is broken.\n");
    108 	(void)printf("%s\n", z);
    109 	free(x);
    110 	free(y);
    111 	free(z);
    112 	free(za);
    113 	return 0;
    114 }
    115 #endif
    116