TwoQueueAm.java

/**
 * OrbisGIS is a java GIS application dedicated to research in GIScience.
 * OrbisGIS is developed by the GIS group of the DECIDE team of the 
 * Lab-STICC CNRS laboratory, see <http://www.lab-sticc.fr/>.
 *
 * The GIS group of the DECIDE team is located at :
 *
 * Laboratoire Lab-STICC – CNRS UMR 6285
 * Equipe DECIDE
 * UNIVERSITÉ DE BRETAGNE-SUD
 * Institut Universitaire de Technologie de Vannes
 * 8, Rue Montaigne - BP 561 56017 Vannes Cedex
 * 
 * OrbisGIS is distributed under GPL 3 license.
 *
 * Copyright (C) 2007-2014 CNRS (IRSTV FR CNRS 2488)
 * Copyright (C) 2015-2017 CNRS (Lab-STICC UMR CNRS 6285)
 *
 * This file is part of OrbisGIS.
 *
 * OrbisGIS 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 3 of the License, or (at your option) any later
 * version.
 *
 * OrbisGIS 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
 * OrbisGIS. If not, see <http://www.gnu.org/licenses/>.
 *
 * For more information, please consult: <http://www.orbisgis.org/>
 * or contact directly:
 * info_at_ orbisgis.org
 */
package org.orbisgis.commons.collections.twoqueue;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Special LRU Linked Queue for use by the {@link TwoQueueBuffer}.
 * 
 * @param <I> the key
 * @param <B> the value
 * @since 2.0
 * @author Antoine Gourlay
 */
final class TwoQueueAm<I, B> implements Iterable<Entry<I, DoubleQueueValue<I, B>>> {

        private Map<I, DoubleQueueValue<I, B>> map = new HashMap<I, DoubleQueueValue<I, B>>();
        private DoubleQueueValue<I, B> newest;
        private int maxSize;

        TwoQueueAm(int maxSize) {
                this.maxSize = maxSize;
        }

        int size() {
                return map.size();
        }

        boolean isEmpty() {
                return map.isEmpty();
        }

        boolean containsKey(I key) {
                return map.containsKey(key);
        }

        B get(I key) {
                final DoubleQueueValue<I, B> get = map.get(key);
                if (get != null) {
                        moveUpFront(get);
                        return get.val;
                } else {
                        return null;
                }
        }

        DoubleQueueValue<I, B> put(I key, B b) {
                final DoubleQueueValue<I, B> q = new DoubleQueueValue(key, b);
                map.put(q.key, q);
                return insertAndTrim(q);
        }

        private DoubleQueueValue<I, B> insertAndTrim(DoubleQueueValue<I, B> v) {
                DoubleQueueValue<I, B> removed = trimOldest();
                insertUpFront(v);
                return removed;
        }

        private void insertUpFront(DoubleQueueValue<I, B> v) {
                if (newest != null) {
                        v.previous = newest.previous;
                        v.next = newest;
                        v.previous.next = v;
                        newest.previous = v;
                } else {
                        v.next = v;
                        v.previous = v;

                }

                newest = v;
        }

        private void moveUpFront(DoubleQueueValue<I, B> v) {
                remove(v);
                insertUpFront(v);
        }

        void remove(DoubleQueueValue<I, B> v) {
                if (map.isEmpty()) {
                        newest = null;
                } else {
                        v.next.previous = v.previous;
                        v.previous.next = v.next;
                        if (v == newest) {
                                newest = v.next;
                        }
                }
        }

        private DoubleQueueValue<I, B> trimOldest() {
                if (map.size() == maxSize + 1) {
                        DoubleQueueValue<I, B> v = newest.previous;
                        map.remove(v.key);
                        newest.previous = v.previous;
                        newest.previous.next = newest;
                        return v;
                } else {
                        return null;
                }
        }

        B remove(I key) {
                DoubleQueueValue<I, B> v = map.remove(key);
                if (v != null) {
                        remove(v);
                        return v.val;
                } else {
                        return null;
                }
        }
        
        void clear() {
                map.clear();
                newest = null;
        }

        @Override
        public Iterator<Entry<I, DoubleQueueValue<I, B>>> iterator() {
                return map.entrySet().iterator();
        }
}