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.modifier;
031
032import org.openimaj.util.hash.HashFunction;
033
034/**
035 * Modify the underlying hash function by applying the modulus to the value.
036 * This has the effect of reducing the range of values the hash function can
037 * take.
038 * 
039 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
040 * 
041 * @param <O>
042 */
043public class ModuloModifier<O> extends HashModifier<O> {
044        private int range;
045
046        /**
047         * Construct with the given hash function and range. The output hash values
048         * will be between 0 and range.
049         * 
050         * @param hashFunction
051         *            the hash function
052         * @param range
053         *            the range
054         */
055        public ModuloModifier(HashFunction<O> hashFunction, int range) {
056                super(hashFunction);
057
058                this.range = range;
059        }
060
061        @Override
062        public int computeHashCode(O object) {
063                final long innerHash = hashFunction.computeHashCode(object) & 0x00000000ffffffffL;
064
065                return (int) (innerHash % range);
066        }
067}