/*
 * 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 1.1.1.3 2003/03/06 00:09:04 landonf Exp $
 */

/*
 *----------------------------------------------------------------------
 *
 * 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.
 *
 *----------------------------------------------------------------------
 */

#include <string.h>

char* strstr(const char* string, const char* substring)
{
	const 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 (char*)string;
	}

	for(; *string != 0; string += 1)
	{
		if(*string != *b)
		{
			continue;
		}

		a = string;

		while(1)
		{
			if(*b == 0)
			{
				return (char*)string;
			}
			if(*a++ != *b++)
			{
				break;
			}
		}

		b = substring;
	}

	return NULL;
}