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How to build an in-memory state engine at runtime

, 28 Oct 2007 CPOL
A C++ template for an efficient in-memory state engine.
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//	Copyright � 2007, solosTec
//  All rights reserved.
//---------------------------------------------------------------------
//	License for redistribution is the GNU General Public License v2.
//	See the included readme.txt for details.
//---------------------------------------------------------------------
//	developed by solosTec
//	http://www.solostec.de
//---------------------------------------------------------------------
//
//	$Author: $
//	$Revision: $
/*	$Log: $
*/
//---------------------------------------------------------------------
/**
 */
#pragma once
#include <string>
#include <mpl/power.h>

namespace turban {
namespace algorithm {

//	+-----------------------------------------------------------------+
//	| hash [declaration]
//	+-----------------------------------------------------------------+
/**
*	Calculates a hash value for a single  sign.
*/
template < typename T >
struct hash
{
	typedef T	String_;
	typedef typename String_::value_type	value_type;

	enum { MAP_SIZE =  mpl::power< unsigned, 2, sizeof( value_type ) >::value };
	size_t operator()( value_type c ) const
	{
		return c % MAP_SIZE;
	}
};

/**
*	Calculates a hash value for a single <code>char</code>.
*/
template <>
struct hash< std::string >
{
	typedef char	value_type;

#ifdef _DEBUG
	enum { MAP_SIZE = 8 };
#else
	enum { MAP_SIZE = 64 };
#endif

	size_t operator()( value_type c ) const
	{
#ifdef _DEBUG
		//std::cout
		//	<< "hash( "
		//	<< c
		//	<< " = "
		//	<< (( c + 0x20 ) % MAP_SIZE)
		//	<< " )"
		//	<< std::endl
		//	;
#endif
		//	0x20 == SPACE
		return ( c + 0x20 ) % MAP_SIZE;
	}
};

/**
*	Calculates a hash value for a single <code>wchar_t</code>.
*/
template <>
struct hash< std::wstring >
{
	typedef wchar_t	value_type;

	enum { MAP_SIZE = 128 };
	size_t operator()( value_type c ) const
	{
		return ( c + L' ' ) % MAP_SIZE;
	}
};

}	//	namespace algorithm
}	//	namespace turban

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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osy
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Switzerland Switzerland
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