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/*
* strstr.c --
*
* Source code for the "strstr" library routine.
*
* Copyright (c) 1988-1993 The Regents of the University of California.
* Copyright (c) 1994 Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: strstr.c,v 1.4 2004/04/06 22:25:48 dgp Exp $
*/
#include "tcl.h"
/*
*----------------------------------------------------------------------
*
* strstr --
*
* Locate the first instance of a substring in a string.
*
* Results:
* If string contains substring, the return value is the
* location of the first matching instance of substring
* in string. If string doesn't contain substring, the
* return value is 0. Matching is done on an exact
* character-for-character basis with no wildcards or special
* characters.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
strstr(string, substring)
register char *string; /* String to search. */
char *substring; /* Substring to try to find in string. */
{
register char *a, *b;
/* First scan quickly through the two strings looking for a
* single-character match. When it's found, then compare the
* rest of the substring.
*/
b = substring;
if (*b == 0) {
return string;
}
for ( ; *string != 0; string += 1) {
if (*string != *b) {
continue;
}
a = string;
while (1) {
if (*b == 0) {
return string;
}
if (*a++ != *b++) {
break;
}
}
b = substring;
}
return NULL;
}
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