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
  11 #include <sys/cdefs.h>
  12 __RCSID("$FreeBSD: src/usr.bin/xargs/strnsubst.c,v 1.6 2002/06/22 12:58:42 jmallett Exp $");
  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                 strncpy(s2, s1, maxsize);
  48                 s2[maxsize - 1] = '\0';
  49                 goto done;
  50         }
  51
  52         for (;;) {
  53                 this = strstr(s1, match);
  54                 if (this == NULL)
  55                         break;
  56                 if ((strlen(s2) + ((uintptr_t)this - (uintptr_t)s1) +
  57                     (strlen(replstr) - 1)) > maxsize && *replstr != '\0') {
  58                         strncat(s2, s1, maxsize);
  59                         s2[maxsize - 1] = '\0';
  60                         goto done;
  61                 }
  62                 strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
  63                 strcat(s2, replstr);
  64                 s1 = this + strlen(match);
  65         }
  66         strcat(s2, s1);
  67 done:
  68         *str = s2;
  69         return;
  70 }
  71
  72 #ifdef TEST
  73 #include <stdio.h>
  74
  75 int
  76 main(void)
  77 {
  78         char *x, *y, *z, *za;
  79
  80         x = "{}%$";
  81         strnsubst(&x, "%$", "{} enpury!", 255);
  82         y = x;
  83         strnsubst(&y, "}{}", "ybir", 255);
  84         z = y;
  85         strnsubst(&z, "{", "v ", 255);
  86         za = z;
  87         strnsubst(&z, NULL, za, 255);
  88         if (strcmp(z, "v ybir enpury!") == 0)
  89                 printf("strnsubst() seems to work!\n");
  90         else
  91                 printf("strnsubst() is broken.\n");
  92         printf("%s\n", z);
  93         free(x);
  94         free(y);
  95         free(z);
  96         free(za);
  97         return 0;
  98 }
  99 #endif