001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (C) Alkacon Software (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.cmis;
029
030import java.math.BigInteger;
031import java.util.Iterator;
032import java.util.List;
033
034/**
035 * Helper class to ease implementation of CMIS service methods which support paging.<p>
036 *
037 * This class works as an iterator for a given list, and limits the number of iterations based on skip/max parameters
038 * which are usually passed to the service methods.<p>
039 *
040 * @param <A> the content type of the list
041 */
042public class CmsObjectListLimiter<A> implements Iterable<A>, Iterator<A> {
043
044    /** The list for which this object acts as an iterator. */
045    private List<A> m_baseList;
046
047    /** The maximum number of objects which can still be returned. */
048    private int m_max;
049
050    /** The index of the next object to return. */
051    private int m_next;
052
053    /**
054     * Creates a new instance.<p>
055     *
056     * @param baseList the list over which we want to iterate
057     * @param maxItems the maximum number of items
058     * @param skipCount the number of items to skip
059     */
060    public CmsObjectListLimiter(List<A> baseList, BigInteger maxItems, BigInteger skipCount) {
061
062        // skip and max
063        m_baseList = baseList;
064        m_next = (skipCount == null ? 0 : skipCount.intValue());
065        if (m_next < 0) {
066            m_next = 0;
067        }
068
069        m_max = (maxItems == null ? Integer.MAX_VALUE : maxItems.intValue());
070        if (m_max < 0) {
071            m_max = Integer.MAX_VALUE;
072        }
073
074    }
075
076    /**
077     * Checks if there are more items left in the base list which were not returned.<p>
078     *
079     * @return true if there are more items left in the base list which were not returned
080     */
081    public boolean hasMore() {
082
083        return m_next < m_baseList.size();
084    }
085
086    /**
087     * @see java.util.Iterator#hasNext()
088     */
089    public boolean hasNext() {
090
091        return (m_next < m_baseList.size()) && (m_max > 0);
092    }
093
094    /**
095     * @see java.lang.Iterable#iterator()
096     */
097    public Iterator<A> iterator() {
098
099        return this;
100    }
101
102    /**
103     * @see java.util.Iterator#next()
104     */
105    public A next() {
106
107        A result = m_baseList.get(m_next);
108        m_next += 1;
109        m_max -= 1;
110        return result;
111    }
112
113    /**
114     * @see java.util.Iterator#remove()
115     */
116    public void remove() {
117
118        throw new UnsupportedOperationException();
119    }
120}