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__FBSDID("$FreeBSD: src/usr.bin/xargs/strnsubst.c,v 1.7 2004/10/18 15:40:47 cperciva Exp $");
13
14#include <err.h>
15#include <stdlib.h>
16#include <string.h>
17#include <unistd.h>
18
19void	strnsubst(char **, const char *, const char *, size_t);
20
21/*
22 * Replaces str with a string consisting of str with match replaced with
23 * replstr as many times as can be done before the constructed string is
24 * maxsize bytes large.  It does not free the string pointed to by str, it
25 * is up to the calling program to be sure that the original contents of
26 * str as well as the new contents are handled in an appropriate manner.
27 * If replstr is NULL, then that internally is changed to a nil-string, so
28 * that we can still pretend to do somewhat meaningful substitution.
29 * No value is returned.
30 */
31void
32strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
33{
34	char *s1, *s2, *this;
35
36	s1 = *str;
37	if (s1 == NULL)
38		return;
39	s2 = calloc(maxsize, 1);
40	if (s2 == NULL)
41		err(1, "calloc");
42
43	if (replstr == NULL)
44		replstr = "";
45
46	if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
47		strlcpy(s2, s1, maxsize);
48		goto done;
49	}
50
51	for (;;) {
52		this = strstr(s1, match);
53		if (this == NULL)
54			break;
55		if ((strlen(s2) + strlen(s1) + strlen(replstr) -
56		    strlen(match) + 1) > maxsize) {
57			strlcat(s2, s1, maxsize);
58			goto done;
59		}
60		strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
61		strcat(s2, replstr);
62		s1 = this + strlen(match);
63	}
64	strcat(s2, s1);
65done:
66	*str = s2;
67	return;
68}
69
70#ifdef TEST
71#include <stdio.h>
72
73int
74main(void)
75{
76	char *x, *y, *z, *za;
77
78	x = "{}%$";
79	strnsubst(&x, "%$", "{} enpury!", 255);
80	y = x;
81	strnsubst(&y, "}{}", "ybir", 255);
82	z = y;
83	strnsubst(&z, "{", "v ", 255);
84	za = z;
85	strnsubst(&z, NULL, za, 255);
86	if (strcmp(z, "v ybir enpury!") == 0)
87		printf("strnsubst() seems to work!\n");
88	else
89		printf("strnsubst() is broken.\n");
90	printf("%s\n", z);
91	free(x);
92	free(y);
93	free(z);
94	free(za);
95	return 0;
96}
97#endif
98