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 __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
  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         /*
  40          * If maxsize is 0 then set it to the length of s1, because we have
  41          * to duplicate s1.  XXX we maybe should double-check whether the match
  42          * appears in s1.  If it doesn't, then we also have to set the length
  43          * to the length of s1, to avoid modifying the argument.  It may make
  44          * sense to check if maxsize is <= strlen(s1), because in that case we
  45          * want to return the unmodified string, too.
  46          */
  47         if (maxsize == 0) {
  48                 match = NULL;
  49                 maxsize = strlen(s1) + 1;
  50         }
  51         s2 = calloc(1, maxsize);
  52         if (s2 == NULL)
  53                 err(1, "calloc");
  54
  55         if (replstr == NULL)
  56                 replstr = "";
  57
  58         if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
  59                 strlcpy(s2, s1, maxsize);
  60                 goto done;
  61         }
  62
  63         for (;;) {
  64                 this = strstr(s1, match);
  65                 if (this == NULL)
  66                         break;
  67                 if ((strlen(s2) + strlen(s1) + strlen(replstr) -
  68                     strlen(match) + 1) > maxsize) {
  69                         strlcat(s2, s1, maxsize);
  70                         goto done;
  71                 }
  72                 strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
  73                 strcat(s2, replstr);
  74                 s1 = this + strlen(match);
  75         }
  76         strcat(s2, s1);
  77 done:
  78         *str = s2;
  79         return;
  80 }
  81
  82 #ifdef TEST
  83 #include <stdio.h>
  84
  85 int
  86 main(void)
  87 {
  88         char *x, *y, *z, *za;
  89
  90         x = "{}%$";
  91         strnsubst(&x, "%$", "{} enpury!", 255);
  92         y = x;
  93         strnsubst(&y, "}{}", "ybir", 255);
  94         z = y;
  95         strnsubst(&z, "{", "v ", 255);
  96         za = z;
  97         strnsubst(&z, NULL, za, 255);
  98         if (strcmp(z, "v ybir enpury!") == 0)
  99                 printf("strnsubst() seems to work!\n");
 100         else
 101                 printf("strnsubst() is broken.\n");
 102         printf("%s\n", z);
 103         free(x);
 104         free(y);
 105         free(z);
 106         free(za);
 107         return 0;
 108 }
 109 #endif