/* 

  * 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 1.3.2.1 2005/04/12 18:28:56 kennykb Exp $

  */

 #include "tcl.h"

 #ifndef NULL

 #define NULL 0

 #endif

 /*

  *----------------------------------------------------------------------

  *

  * 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;

 }