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/* eurephia_directions.h -- Macro to decide the best search directon on dual-way pointer chains
*
* GPLv2 only - Copyright (C) 2008 - 2010
* David Sommerseth <dazo@users.sourceforge.net>
*
* 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; version 2
* of the License.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
/**
* @file eurephia_directions.h
* @author David Sommerseth <dazo@users.sourceforge.net>
* @date 2008-08-06
*
* @brief Macro to decide the best search directon on dual-way
* ring based pointer chains
*
*/
#ifndef _EUREPHIA_DIRECTIONS_H
#define _EUREPHIA_DIRECTIONS_H
#define DIR_R 'R' /**< "Right" direction, where the ID number increases (next element) */
#define DIR_L 'L' /**< "Left" direction, where the ID number decreases (previous element) */
/**
* This macro finds the quickest way to go from one element to another one in
* a circular dual-way pointer chain, based on a numeric id of the elements.
*
* @param s starting point on the chain
* @param d destination point on the chain
* @param l number of elements in the chain
*
* @return Returns DIR_R or DIR_L, depending on what will be the shortest distance.
*/
#define DIRECTION(s,d,l) (s>d ? ((((l-s)+d) > (s-d)) ? DIR_L : DIR_R) : (((d-s) > ((l-d)+s)) ? DIR_L : DIR_R))
#endif
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