Claudenw commented on a change in pull request #83: Initial bloom filter code contribution URL: https://github.com/apache/commons-collections/pull/83#discussion_r365576800
########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/hasher/DynamicHasher.java ########## @@ -0,0 +1,176 @@ +/* + * 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 java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.List; +import java.util.NoSuchElementException; +import java.util.PrimitiveIterator; + +import org.apache.commons.collections4.bloomfilter.BloomFilter.Shape; +import org.apache.commons.collections4.bloomfilter.Hasher; + +/** + * The class that performs hashing on demand. + * @since 4.5 + */ +public class DynamicHasher implements Hasher { + + /** + * The list of byte arrays that are to be hashed. + */ + private final List<byte[]> buffers; + + /** + * The function to hash the buffers. + */ + private final HashFunction function; + + /** + * Constructs a DynamicHasher. + * + * @param function the function to use. + * @param buffers the byte buffers that will be hashed. + */ + public DynamicHasher(HashFunction function, List<byte[]> buffers) { + this.buffers = new ArrayList<byte[]>(buffers); + this.function = function; + } + + @Override + public HashFunctionIdentity getHashFunctionIdentity() { + return function; + } + + /** + * Return an iterator of integers that are the bits to enable in the Bloom filter + * based on the shape. The iterator may return the same value multiple times. There is + * no guarantee made as to the order of the integers. + * + * @param shape the shape of the desired Bloom filter. + * @return the Iterator of integers; + * @throws IllegalArgumentException if {@code shape.getHasherName()} does not equal + * {@code getName()} + */ + @Override + public PrimitiveIterator.OfInt getBits(Shape shape) { + if (HashFunctionIdentity.COMMON_COMPARATOR.compare(getHashFunctionIdentity(), + shape.getHashFunctionIdentity()) != 0) { + throw new IllegalArgumentException( + String.format("Shape hasher %s is not %s", + HashFunctionIdentity.asCommonString(shape.getHashFunctionIdentity()), + HashFunctionIdentity.asCommonString(getHashFunctionIdentity()))); + } + return new Iterator(shape); + } + + /** + * The iterator of integers. + */ + private class Iterator implements PrimitiveIterator.OfInt { + private int buffer = 0; + private int funcCount = 0; + private final Shape shape; + + /** + * Creates iterator with the specified shape. + * + * @param shape + */ + private Iterator(Shape shape) { + this.shape = shape; + } + + @Override + public boolean hasNext() { + if (buffers.isEmpty()) { + return false; + } + return buffer < buffers.size() - 1 || funcCount < shape.getNumberOfHashFunctions(); + } + + @Override + public int nextInt() { + if (hasNext()) { + if (funcCount >= shape.getNumberOfHashFunctions()) { + funcCount = 0; + buffer++; + } + return (int) Math.floorMod(function.apply(buffers.get(buffer), funcCount++), + (long) shape.getNumberOfBits()); + } + throw new NoSuchElementException(); + } + } + + /** + * The builder for DyanamicHashers. Review comment: fixed ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
