source: source/ariba/overlay/modules/chord/detail/distances.hpp@ 12767

// [License]

// The Ariba-Underlay Copyright

//

// Copyright (c) 2008-2009, Institute of Telematics, UniversitÀt Karlsruhe (TH)

//

// Institute of Telematics

// UniversitÀt Karlsruhe (TH)

// Zirkel 2, 76128 Karlsruhe

// Germany

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

// 1. Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// 2. Redistributions in binary form must reproduce the above copyright

// notice, this list of conditions and the following disclaimer in the

// documentation and/or other materials provided with the distribution.

//

// THIS SOFTWARE IS PROVIDED BY THE INSTITUTE OF TELEMATICS ``AS IS'' AND

// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OF TELEMATICS OR

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// The views and conclusions contained in the software and documentation

// are those of the authors and should not be interpreted as representing

// official policies, either expressed or implied, of the Institute of

// Telematics.

// [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_ */