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;
031
032import java.util.Date;
033
034
035import cern.jet.random.engine.MersenneTwister;
036
037/**
038 * A {@link HashFunctionFactory} for producing {@link StringMurmurHashFunction}s
039 * with randomly assigned seeds.
040 * 
041 * @see StringMurmurHashFunction#StringMurmurHashFunction(int)
042 * 
043 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
044 * 
045 */
046public class StringMurmurHashFunctionFactory implements HashFunctionFactory<String> {
047        private MersenneTwister rng;
048
049        /**
050         * Construct the factory with a newly constructed {@link MersenneTwister}
051         * seeded with the current time.
052         */
053        public StringMurmurHashFunctionFactory() {
054                this.rng = new MersenneTwister(new Date());
055        }
056
057        /**
058         * Construct the factory with the given random generator
059         * 
060         * @param rng
061         *            the random generator
062         */
063        public StringMurmurHashFunctionFactory(MersenneTwister rng) {
064                this.rng = rng;
065        }
066
067        @Override
068        public StringMurmurHashFunction create() {
069                return new StringMurmurHashFunction(rng.nextInt());
070        }
071}