usr.bin/xargs/strnsubst.c

   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  * $FreeBSD: src/usr.bin/xargs/strnsubst.c,v 1.5.2.1 2002/06/17 04:44:46 jmallett Exp $
  11  * $DragonFly: src/usr.bin/xargs/strnsubst.c,v 1.2 2003/06/17 04:29:34 dillon Exp $
  12  */
  13
  14 #include <err.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18
  19 void    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  */
  31 void
  32 strnsubst(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) + ((uintptr_t)this - (uintptr_t)s1) +
  56                     (strlen(replstr) - 1)) > maxsize && *replstr != '\0') {
  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);
  65 done:
  66         *str = s2;
  67         return;
  68 }
  69
  70 #ifdef TEST
  71 #include <stdio.h>
  72
  73 int
  74 main(void)
  75 {
  76         char *x, *y;
  77
  78         y = x = "{}{}{}";
  79         strnsubst(&x, "{}", "v ybir whyv! ", 12);
  80         if (strcmp(x, "v ybir whyv! ") == 0)
  81                 printf("strnsubst() seems to work as expected.\n");
  82         printf("x: %s\ny: %s\n", x, y);
  83         free(x);
  84         return 0;
  85 }
  86 #endif