find_first_of: A performance pitfall among the STL algorithms

/*
 *  Copyright (c) 2007
 *  Jim Xochellis
 *
 *  Permission to use, copy, modify, distribute and sell this software for any purpose
 *  is hereby granted without fee, provided that the above copyright notice appears in
 *  all copies and that both that copyright notice and this permission notice appear in
 *  supporting documentation. Jim Xochellis makes no representations about the suitability
 *  of this software for any purpose. It is provided "as is" without express or implied
 *  warranty.
 *
 */

#ifndef __DPX_DPX_FIND_FIRST_OF_H__
#define __DPX_DPX_FIND_FIRST_OF_H__

#include <memory.h>

namespace dpx
{

template<typename _InputIterator, typename _ForwardIterator>
_InputIterator find_first_of(_InputIterator __first1, _InputIterator __last1,
					_ForwardIterator __first2, _ForwardIterator __last2)
{
	unsigned char __MapArray[256];
	memset(__MapArray, 0, 256);

	for (_ForwardIterator __iter = __first2; __iter != __last2; ++__iter)
		__MapArray[(unsigned char) *__iter] = 1;

	for ( ; __first1 != __last1; ++__first1)
	{
		if (__MapArray[(unsigned char) *__first1] != 0)
			return __first1;
	}

	return __last1;
}

} //namespace dpx

#endif //__DPX_DPX_FIND_FIRST_OF_H__