// Copyright (C) 2001 Open Source Telecom Corporation.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// As a special exception to the GNU General Public License, permission is
// granted for additional uses of the text contained in its release
// of Common C++.
//
// The exception is that, if you link the Common C++ library with other
// files to produce an executable, this does not by itself cause the
// resulting executable to be covered by the GNU General Public License.
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// linking the Common C++ library code into it.
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// This exception does not however invalidate any other reasons why
// the executable file might be covered by the GNU General Public License.
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// This exception applies only to the code released under the
// name Common C++.  If you copy code from other releases into a copy of
// Common C++, as the General Public License permits, the exception does
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/**
 * @file objmap.h
 * @short Template for creating hash indexed objects.
 **/

#include <cc++/strchar.h>

namespace ost {

/**
 * Used to create and manage a hash index of objects through a common
 * type.  The objects can be examined and a specific instance located
 * by a hash key.
 *
 * @author David Sugar <dyfet@gnutelephony.org>
 * @short hash indexed searchable template chain.
 */
template <class T, class K, unsigned S>
class objMap {
protected:
	static T *objIndex[S];
	T* objNext;
	const K objKey;

	virtual unsigned keyIndex(K k) 
	{
		unsigned idx = 0;
		unsigned char *p = (unsigned char *)&k;
		unsigned len = sizeof(K);

		while(len--) {
			idx ^= (idx << 1) ^ *p;
			++p;
		}
		return idx % S;
	}

	inline unsigned getSize(void) 
		{return S;}

	objMap(const K key) 
	{
		unsigned idx = keyIndex(key);
		objKey = key;
		objNext = objIndex[idx];
		objIndex[idx] = (T *)this;
	}
public:
	static T *getObject(keystring key);
};

template <class T, unsigned S>
class keyMap : public objMap<T, keystring, S>
{
	keyMap(keystring key) : objMap<T, keystring, S>(key) {};

	unsigned keyIndex(keystring k) 
	{
		unsigned idx = 0;
		while(*k) {
			idx = (idx << 1) ^ (unsigned)*k;
			++k;
		}
		return idx % S;
	}
};

template <class T, class K, unsigned S>
T *objMap<T, K, S>::objIndex[S](0);

template <class T, class K, unsigned S>
T *objMap<T, K, S>::getObject(const keystring key)
{
	T *obj = objIndex[keyIndex(key)];
	while(obj) {
		if(key == obj->objKey)
			break;
		obj = obj->objNext;
	}
	return obj;
}

} // namespace
