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$");
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
25void	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 */
37void
38strnsubst(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);
83done:
84	*str = s2;
85	return;
86}
87
88#ifdef TEST
89#include <stdio.h>
90
91int
92main(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