source: source/ariba/overlay/modules/chord/detail/distances.hpp@ 9633

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// [License]

#ifndef DISTANCES_HPP_

#define DISTANCES_HPP_



/**

 * TODO: Doc

 *

 * @author Sebastian Mies <mies@tm.uka.de>

 */

namespace distances {



/// returns the maximum value of a type

template<class T>

T max_value() {

        return ~(T)0;

}



/// returns the maximum value of a type

template<class T>

T min_value() {

        return 0;

}



/// euclidean distance between two points (metric)

struct default_distance {

        template<typename T>

        T operator ()(const T& x, const T& y) {

                return abs(x - y);

        }

};



/// xor distance (metric)

struct xor_distance {

        template<typename T>

        T operator()(const T& x, const T& y) {

                return x ^ y;

        }

};



/// distance between two points on a ring (metric)

struct ring_distance {

        template<typename T>

        T operator()(const T& x, const T& y) {

                const T m = max_value<T>();

                T d_nor = (x >= y) ? (x-y) : (y-x);

                T d_inv = m - d_nor;

                return d_nor < d_inv ? d_nor : d_inv;

        }

};



/// distance from x to a predecessor y on a ring (not a metric!)

struct ring_pred_distance {

        template<typename T>

        T operator ()(const T& x, const T& y) {

                const T m = max_value<T>();

                if (x >= y) return x - y;

                else return m - y + x;

        }

};



/// distance from x to a successor y on a ring (not a metric!)

struct ring_succ_distance {

        template<typename T>

        T operator ()(const T& y, const T& x) {

                const T m = max_value<T>();

                if (x >= y) return x - y;

                else return m - y + x;

        }

};



}



#endif /* DISTANCES_HPP_ */