source: source/ariba/overlay/modules/chord/detail/distances.hpp@ 7521

// [License]
// The Ariba-Underlay Copyright
//
// Copyright (c) 2008-2009, Institute of Telematics, UniversitÀt Karlsruhe (TH)
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// UniversitÀt Karlsruhe (TH)
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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_ */