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.hash.composition;
031
032import java.util.List;
033
034import org.openimaj.util.hash.HashCodeUtil;
035import org.openimaj.util.hash.HashFunction;
036import org.openimaj.util.hash.HashFunctionFactory;
037
038/**
039 * Simple composition function. Computes the composite hash using the same
040 * method as {@link HashCodeUtil} for int arrays.
041 *
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 *
044 * @param <OBJECT>
045 *            Type of object being hashed
046 */
047public class SimpleComposition<OBJECT> extends HashComposition<OBJECT> {
048        /**
049         * Construct with the given functions.
050         *
051         * @param functions
052         *            the underlying hash functions.
053         */
054        public SimpleComposition(List<HashFunction<OBJECT>> functions) {
055                super(functions);
056        }
057
058        /**
059         * Construct with the given functions.
060         *
061         * @param first
062         *            the first function
063         * @param remainder
064         *            the remainder of the functions
065         */
066        @SafeVarargs
067        public SimpleComposition(HashFunction<OBJECT> first, HashFunction<OBJECT>... remainder) {
068                super(first, remainder);
069        }
070
071        /**
072         * Construct with the factory which is used to produce the required number
073         * of functions.
074         *
075         * @param factory
076         *            the factory to use to produce the underlying hash functions.
077         * @param nFuncs
078         *            the number of functions to create for the composition
079         */
080        public SimpleComposition(HashFunctionFactory<OBJECT> factory, int nFuncs) {
081                super(factory, nFuncs);
082        }
083
084        @Override
085        public int computeHashCode(OBJECT object) {
086                int result = HashCodeUtil.SEED;
087
088                for (int i = 0; i < hashFunctions.size(); i++)
089                        result = HashCodeUtil.hash(result, hashFunctions.get(i).computeHashCode(object));
090
091                return result;
092        }
093}