Copyright © 2004 Gene Michael Stover. All rights reserved. Permission to copy, store, & view this document unmodified & in its entirety is granted.
At the different programming contracts I work, I often need a function to replace a substring with another string. Instead of writing one each time, I've written it once. Instead of putting it in some library & forgetting about it, I put it here.
The source code for each of these functions is copyrighted by Gene Michael Stover & is licensed according to the terms of the Gnu Lesser General Public License (LGPL).
This version for C assumes you reserve memory from the dynamic memory pool with function called xmalloc & return the memory to that pool with xfree. xmalloc works like malloc; xfree works like free. If you don't have your own implementations of xmalloc & xfree, you might do this:
/* Easy way to implement xmalloc & xfree as malloc & free */ #define xmalloc malloc #define xfree free
Here is the C source code for StrSubst itself.
/*
* Copyright (c) 2004 Gene Michael Stover. All rights reserved.
*/
/*
* Given a string, a source substring, & a destination substring, return
* a new string in which the first occurrence of the source substring
* has been replaced with the destination substring. If there is no
* occurrence of the source substring, you get a copy of the original
* string with no changes. To replace multiple occurrences, call this
* function multiple times, each time with the last string returned by
* the previous function call.
*
* Caller must free the new string with 'xfree'.
*/
char *
StrSubst (big, src, dst)
char big[];
char src[]
char dst[];
{
char *str = NULL, *p;
p = strstr (big, src);
if (p != NULL) {
str = (char *) xmalloc (strlen (big) - strlen (src) + strlen (dst) + 1);
sprintf (str, ``%*s%s%s'', p - big, big, dst, p + strlen (src));
} else {
/*
* Didn't find the src string at all, so return a copy of the big
* string.
*/
str = xstrdup (big);
}
return str;
}
Guess what: I haven't done the Lisp implementation yet.