Claudenw commented on a change in pull request #258: URL: https://github.com/apache/commons-collections/pull/258#discussion_r805173454
########## File path: src/test/java/org/apache/commons/collections4/bloomfilter/hasher/AbstractHasherTest.java ########## @@ -0,0 +1,67 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.collections4.bloomfilter.hasher; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import org.apache.commons.collections4.bloomfilter.AbstractIndexProducerTest; +import org.apache.commons.collections4.bloomfilter.IndexProducer; +import org.apache.commons.collections4.bloomfilter.Shape; +import org.junit.Test; + +public abstract class AbstractHasherTest extends AbstractIndexProducerTest { + + protected abstract Hasher createHasher(); + + protected abstract Hasher createEmptyHasher(); + + /** + * The shape of the Hashers filters for testing. + * <ul> + * <li>Hash functions (k) = 17 + * <li>Number of bits (m) = 72 + * </ul> + * @return the testing shape. + */ + protected final Shape getTestShape() { + return Shape.fromKM(17, 72); + } + + @Override + protected IndexProducer createProducer() { + return createHasher().indices(getTestShape()); + } + + @Override + protected IndexProducer createEmptyProducer() { + return createEmptyHasher().indices(getTestShape()); + } + + @Test + public void testSize() { + assertEquals(1, createHasher().size()); + assertEquals(0, createEmptyHasher().size()); + } + + @Test + public void testIsEmpty() { + assertFalse(createHasher().isEmpty()); + assertTrue(createEmptyHasher().isEmpty()); + } +} Review comment: SingleItemHasherCollection dropped and with it the size() and isEmpty() methods on the Hasher as they are not needed. Added `abstract int getHasherSize(Hasher)` method to Abstract testing class as the concrete testing classes can figure out how bit the hashers are. ########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/SimpleHasher.java ########## @@ -0,0 +1,169 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.collections4.bloomfilter; + +import java.util.Objects; +import java.util.function.IntPredicate; + +/** + * A Hasher that implements combinatorial hashing as as described by + * <a href="https://www.eecs.harvard.edu/~michaelm/postscripts/tr-02-05.pdf";>Krisch and Mitzenmacher</a>. + * <p> + * Common use for this hasher is to generate a byte array as the output of a hashing + * or MessageDigest algorithm.</p> + * + * @since 4.5 + */ +public final class SimpleHasher implements Hasher { + /** + * A default increment used when the requested increment is zero. This is the same + * default increment used in Java's SplittableRandom random number generator. It is the + * fractional representation of the golden ratio (0.618...) with a base of 2^64. + */ + public static final long DEFAULT_INCREMENT = 0x9e3779b97f4a7c15L; Review comment: remove it and added a public method called `getDefaultIncrement()` so that this implementation can be dropped into environments where a different default was selected by simply overloading that method. Documented such in method. ########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/SimpleHasher.java ########## @@ -0,0 +1,169 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.collections4.bloomfilter; + +import java.util.Objects; +import java.util.function.IntPredicate; + +/** + * A Hasher that implements combinatorial hashing as as described by + * <a href="https://www.eecs.harvard.edu/~michaelm/postscripts/tr-02-05.pdf";>Krisch and Mitzenmacher</a>. + * <p> + * Common use for this hasher is to generate a byte array as the output of a hashing + * or MessageDigest algorithm.</p> + * + * @since 4.5 + */ +public final class SimpleHasher implements Hasher { + /** + * A default increment used when the requested increment is zero. This is the same + * default increment used in Java's SplittableRandom random number generator. It is the + * fractional representation of the golden ratio (0.618...) with a base of 2^64. + */ + public static final long DEFAULT_INCREMENT = 0x9e3779b97f4a7c15L; + + /** + * The initial hash value. + */ + private final long initial; + + /** + * The value to increment the hash value by. + */ + private final long increment; + + /** + * Convert bytes to long. + * @param byteArray the byte array to extract the values from. + * @param offset the offset to start extraction from. + * @param len the length of the extraction, may be longer than 8. + * @return + */ + private static long toLong(byte[] byteArray, int offset, int len) { + long val = 0; + len = Math.min(len, Long.BYTES); + for (int i = 0; i < len; i++) { + val <<= 8; + val |= (byteArray[offset + i] & 0x00FF); + } + return val; + } + + /** + * Constructs the SimpleHasher from a byte array. + * <p>The byte array is split in 2 and each half is interpreted as a long value. + * Excess bytes are ignored. This simplifies the conversion from a Digest or hasher algorithm output + * to the two values used by the SimpleHasher.</p> + * <p><em>If the second long is zero the DEFAULT_INCREMENT is used instead.</em></p> + * @param buffer the buffer to extract the longs from. + * @throws IllegalArgumentException is buffer length is zero. + */ + public SimpleHasher(byte[] buffer) { + if (buffer.length == 0) { + throw new IllegalArgumentException("buffer length must be greater than 0"); + } + int segment = buffer.length / 2; + this.initial = toLong(buffer, 0, segment); + long possibleIncrement = toLong(buffer, segment, buffer.length - segment); + this.increment = possibleIncrement == 0 ? DEFAULT_INCREMENT : possibleIncrement; + } + + /** + * Constructs the SimpleHasher from 2 longs. The long values will be interpreted as unsigned values. Review comment: updated. -- This is an automated message from the Apache Git Service. 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