1 /* $OpenBSD: strnsubst.c,v 1.4 2005/12/01 05:52:20 cloder Exp $ */
2 /* $FreeBSD: strnsubst.c,v 1.6 2002/06/22 12:58:42 jmallett Exp $ */
3
4 /*
5 * Copyright (c) 2002 J. Mallett. All rights reserved.
6 * You may do whatever you want with this file as long as
7 * the above copyright and this notice remain intact, along
8 * with the following statement:
9 * For the man who taught me vi, and who got too old, too young.
10 */
11
12 #ifndef lint
13 static const char rcsid[] = "$OpenBSD: strnsubst.c,v 1.4 2005/12/01 05:52:20 cloder Exp $";
14 #endif /* not lint */
15
16 #include <err.h>
17 #include <stdio.h>
18 #include <stdlib.h>
19 #include <string.h>
20 #include <unistd.h>
21
22 void strnsubst(char **, const char *, const char *, size_t);
23
24 /*
25 * Replaces str with a string consisting of str with match replaced with
26 * replstr as many times as can be done before the constructed string is
27 * maxsize bytes large. It does not free the string pointed to by str, it
28 * is up to the calling program to be sure that the original contents of
29 * str as well as the new contents are handled in an appropriate manner.
30 * If replstr is NULL, then that internally is changed to a nil-string, so
31 * that we can still pretend to do somewhat meaningful substitution.
32 * No value is returned.
33 */
34 void
strnsubst(char ** str,const char * match,const char * replstr,size_t maxsize)35 strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
36 {
37 char *s1, *s2, *this;
38 size_t matchlen, repllen, s2len;
39 int n;
40
41 if ((s1 = *str) == NULL)
42 return;
43 if ((s2 = malloc(maxsize)) == NULL)
44 err(1, NULL);
45
46 if (replstr == NULL)
47 replstr = "";
48
49 if (match == NULL || *match == '\0' || strlen(s1) >= maxsize) {
50 strlcpy(s2, s1, maxsize);
51 goto done;
52 }
53
54 *s2 = '\0';
55 s2len = 0;
56 matchlen = strlen(match);
57 repllen = strlen(replstr);
58 for (;;) {
59 if ((this = strstr(s1, match)) == NULL)
60 break;
61 n = snprintf(s2 + s2len, maxsize - s2len, "%.*s%s",
62 (int)(this - s1), s1, replstr);
63 if (n == -1 || n + s2len + strlen(this + matchlen) >= maxsize)
64 break; /* out of room */
65 s2len += n;
66 s1 = this + matchlen;
67 }
68 strlcpy(s2 + s2len, s1, maxsize - s2len);
69 done:
70 *str = s2;
71 return;
72 }
73
74 #ifdef TEST
75 #include <stdio.h>
76
77 int
main(void)78 main(void)
79 {
80 char *x, *y, *z, *za;
81
82 x = "{}%$";
83 strnsubst(&x, "%$", "{} enpury!", 255);
84 y = x;
85 strnsubst(&y, "}{}", "ybir", 255);
86 z = y;
87 strnsubst(&z, "{", "v ", 255);
88 za = z;
89 strnsubst(&z, NULL, za, 255);
90 if (strcmp(z, "v ybir enpury!") == 0)
91 printf("strnsubst() seems to work!\n");
92 else
93 printf("strnsubst() is broken.\n");
94 printf("%s\n", z);
95 free(x);
96 free(y);
97 free(z);
98 free(za);
99 return 0;
100 }
101 #endif
102