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repl_str.c
Go to the documentation of this file.
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/*
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* An implementation of replacing substrings in a string.
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*
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* Source: http://creativeandcritical.net/str-replace-c
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* Author: Laird Shaw
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* License: Public domain
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*
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* Brought on 2016-02-24
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*/
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#include <string.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include "
repl_str.h
"
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/* An optimised string replacement function that caches string positions so that
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* strstr() doesn't need to be called twice for each position.
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*
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* This code is entirely by me, and released into the public domain, so have no
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* doubts about your right to use it.
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*/
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char
*
replace_substr
(
const
char
*
str
,
const
char
*
old
,
const
char
*
new
) {
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/* Adjust each of the below values to suit your needs. */
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/* Increment positions cache size initially by this number. */
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size_t
cache_sz_inc
= 16;
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/* Thereafter, each time capacity needs to be increased,
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* multiply the increment by this factor. */
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const
size_t
cache_sz_inc_factor
= 3;
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/* But never increment capacity by more than this number. */
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const
size_t
cache_sz_inc_max
= 1048576;
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char
*
pret
, *
ret
=
NULL
;
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const
char
*
pstr2
, *
pstr
=
str
;
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size_t
i, count = 0;
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ptrdiff_t
*
pos_cache
=
NULL
;
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size_t
cache_sz
= 0;
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size_t
cpylen
,
orglen
,
retlen
,
newlen
,
oldlen
= strlen(
old
);
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/* Find all matches and cache their positions. */
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while
((
pstr2
=
strstr
(
pstr
,
old
)) !=
NULL
) {
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count++;
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/* Increase the cache size when necessary. */
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if
(
cache_sz
< count) {
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cache_sz
+=
cache_sz_inc
;
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pos_cache
=
realloc
(
pos_cache
,
sizeof
(*
pos_cache
) *
cache_sz
);
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if
(
pos_cache
==
NULL
) {
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goto
end_repl_str
;
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}
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cache_sz_inc
*=
cache_sz_inc_factor
;
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if
(
cache_sz_inc
>
cache_sz_inc_max
) {
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cache_sz_inc
=
cache_sz_inc_max
;
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}
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}
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pos_cache
[count-1] =
pstr2
-
str
;
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pstr
=
pstr2
+
oldlen
;
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}
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orglen
=
pstr
-
str
+ strlen(
pstr
);
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/* Allocate memory for the post-replacement string. */
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if
(count > 0) {
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newlen
= strlen(
new
);
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retlen
=
orglen
+ (
newlen
-
oldlen
) * count;
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}
else
retlen
=
orglen
;
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ret
=
malloc
(
retlen
+ 1);
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if
(
ret
==
NULL
) {
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goto
end_repl_str
;
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}
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if
(count == 0) {
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/* If no matches, then just duplicate the string. */
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strcpy
(
ret
,
str
);
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}
else
{
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/* Otherwise, duplicate the string whilst performing
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* the replacements using the position cache. */
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pret
=
ret
;
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memcpy
(
pret
,
str
,
pos_cache
[0]);
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pret
+=
pos_cache
[0];
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for
(i = 0; i < count; i++) {
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memcpy
(
pret
,
new
,
newlen
);
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pret
+=
newlen
;
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pstr
=
str
+
pos_cache
[i] +
oldlen
;
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cpylen
= (i == count-1 ?
orglen
:
pos_cache
[i+1]) -
pos_cache
[i] -
oldlen
;
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memcpy
(
pret
,
pstr
,
cpylen
);
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pret
+=
cpylen
;
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}
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ret
[
retlen
] =
'\0'
;
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}
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end_repl_str
:
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/* Free the cache and return the post-replacement string,
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* which will be NULL in the event of an error. */
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free
(
pos_cache
);
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return
ret
;
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}
PlaceX
static int PlaceX
Definition
add_window.c:82
replace_substr
char * replace_substr(const char *str, const char *old, const char *new)
Definition
repl_str.c:24
repl_str.h
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