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/* $OpenBSD: strnsubst.c,v 1.7 2019/07/03 03:24:02 deraadt Exp $ */
/* $FreeBSD: strnsubst.c,v 1.6 2002/06/22 12:58:42 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.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;
size_t matchlen, s2len;
int n;
if ((s1 = *str) == NULL)
return;
if ((s2 = malloc(maxsize)) == NULL)
err(1, NULL);
if (replstr == NULL)
replstr = "";
if (match == NULL || *match == '\0' || strlen(s1) >= maxsize) {
strlcpy(s2, s1, maxsize);
goto done;
}
*s2 = '\0';
s2len = 0;
matchlen = strlen(match);
for (;;) {
if ((this = strstr(s1, match)) == NULL)
break;
n = snprintf(s2 + s2len, maxsize - s2len, "%.*s%s",
(int)(this - s1), s1, replstr);
if (n < 0 || n + s2len + strlen(this + matchlen) >= maxsize)
break; /* out of room */
s2len += n;
s1 = this + matchlen;
}
strlcpy(s2 + s2len, s1, maxsize - s2len);
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)
printf("strnsubst() seems to work!\n");
else
printf("strnsubst() is broken.\n");
printf("%s\n", z);
free(x);
free(y);
free(z);
free(za);
return 0;
}
#endif
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