001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.util.list;
031
032import java.util.AbstractList;
033import java.util.Arrays;
034import java.util.List;
035
036/**
037 * A read-only view on a list with a set of indices from the
038 * underlying list that must be skipped. The view is
039 * continuous, and presents itself without any gaps.
040 * The size  of the view is equal to the length of 
041 * the underlying list minus the number of skipped elements. 
042 * 
043 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
044 *
045 * @param <T> The type of element in the list
046 */
047public class SkippingListView<T> extends AbstractList<T> {
048        private List<T> list;
049        private int[] skips;
050        private int size;
051
052        /**
053         * Construct with the underlying list and a set of
054         * indices to skip. 
055         * 
056         * @param list the backing list
057         * @param skips the indices to skip
058         */
059        public SkippingListView(List<T> list, int... skips) {
060                if (skips == null)
061                        skips = new int[0];
062                
063                this.list = list;
064                this.size = list.size() - skips.length;
065                
066                this.skips = skips.clone();
067                Arrays.sort(this.skips);
068                
069                for (int i=0; i<skips.length; i++)
070                        this.skips[i] -= i;
071        }
072        
073        @Override
074        public T get(int index) {
075                int shift = Arrays.binarySearch(skips, index);
076                                
077                if (shift < 0) {
078                        shift = -1 * (shift + 1);
079                } else {
080                        while ((shift < skips.length - 1) && (skips[shift] == skips[shift + 1])) {
081                                shift++;
082                        }
083                        
084                        shift++;
085                        
086                }
087                
088                return list.get(index + shift);
089        }
090
091        @Override
092        public int size() {
093                return size;
094        }
095}