/* $xMach: strnsubst.c,v 1.3 2002/02/23 02:10:24 jmallett Exp $ */
/*
* Copyright (c) 2002 J. Mallett. All rights reserved.
* You may do whatever you want with this file as long as
* the above copyright and this notice remain intact, along
* with the following statement:
* For the man who taught me vi, and who got too old, too young.
*/
#include <err.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
void strnsubst(char **, const char *, const char *, size_t);
/*
* Replaces str with a string consisting of str with match replaced with
* replstr as many times as can be done before the constructed string is
* maxsize bytes large. It does not free the string pointed to by str, it
* is up to the calling program to be sure that the original contents of
* str as well as the new contents are handled in an appropriate manner.
* If replstr is NULL, then that internally is changed to a nil-string, so
* that we can still pretend to do somewhat meaningful substitution.
* No value is returned.
*/
void
strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
{
char *s1, *s2, *this;
s1 = *str;
if (s1 == NULL)
return;
/*
* If maxsize is 0 then set it to to the length of s1, because we have
* to duplicate s1. XXX we maybe should double-check whether the match
* appears in s1. If it doesn't, then we also have to set the length
* to the length of s1, to avoid modifying the argument. It may make
* sense to check if maxsize is <= strlen(s1), because in that case we
* want to return the unmodified string, too.
*/
if (maxsize == 0) {
match = NULL;
maxsize = strlen(s1) + 1;
}
s2 = calloc(maxsize, 1);
if (s2 == NULL)
err(1, "calloc");
if (replstr == NULL)
replstr = "";
if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
(void)strlcpy(s2, s1, maxsize);
goto done;
}
for (;;) {
this = strstr(s1, match);
if (this == NULL)
break;
if ((strlen(s2) + strlen(s1) + strlen(replstr) -
strlen(match) + 1) > maxsize) {
(void)strlcat(s2, s1, maxsize);
goto done;
}
(void)strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
(void)strcat(s2, replstr);
s1 = this + strlen(match);
}
(void)strcat(s2, s1);
done:
*str = s2;
return;
}
#ifdef TEST
#include <stdio.h>
int
main(void)
{
char *x, *y, *z, *za;
x = "{}%$";
strnsubst(&x, "%$", "{} enpury!", 255);
y = x;
strnsubst(&y, "}{}", "ybir", 255);
z = y;
strnsubst(&z, "{", "v ", 255);
za = z;
strnsubst(&z, NULL, za, 255);
if (strcmp(z, "v ybir enpury!") == 0)
(void)printf("strnsubst() seems to work!\n");
else
(void)printf("strnsubst() is broken.\n");
(void)printf("%s\n", z);
free(x);
free(y);
free(z);
free(za);
return 0;
}
#endif
