Java tutorial
/* * 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 com.uber.hoodie.common; import com.uber.hoodie.exception.HoodieIndexException; import java.io.ByteArrayInputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import java.nio.charset.StandardCharsets; import javax.xml.bind.DatatypeConverter; import org.apache.commons.io.output.ByteArrayOutputStream; import org.apache.hadoop.util.bloom.Key; import org.apache.hadoop.util.hash.Hash; /** * A Bloom filter implementation built on top of {@link org.apache.hadoop.util.bloom.BloomFilter}. */ public class BloomFilter { /** * Used in computing the optimal Bloom filter size. This approximately equals 0.480453. */ public static final double LOG2_SQUARED = Math.log(2) * Math.log(2); private org.apache.hadoop.util.bloom.BloomFilter filter = null; public BloomFilter(int numEntries, double errorRate) { this(numEntries, errorRate, Hash.MURMUR_HASH); } /** * Create a new Bloom filter with the given configurations. */ public BloomFilter(int numEntries, double errorRate, int hashType) { // Bit size int bitSize = (int) Math.ceil(numEntries * (-Math.log(errorRate) / LOG2_SQUARED)); // Number of the hash functions int numHashs = (int) Math.ceil(Math.log(2) * bitSize / numEntries); // The filter this.filter = new org.apache.hadoop.util.bloom.BloomFilter(bitSize, numHashs, hashType); } /** * Create the bloom filter from serialized string. */ public BloomFilter(String filterStr) { this.filter = new org.apache.hadoop.util.bloom.BloomFilter(); byte[] bytes = DatatypeConverter.parseBase64Binary(filterStr); DataInputStream dis = new DataInputStream(new ByteArrayInputStream(bytes)); try { this.filter.readFields(dis); dis.close(); } catch (IOException e) { throw new HoodieIndexException("Could not deserialize BloomFilter instance", e); } } public void add(String key) { if (key == null) { throw new NullPointerException("Key cannot by null"); } filter.add(new Key(key.getBytes(StandardCharsets.UTF_8))); } public boolean mightContain(String key) { if (key == null) { throw new NullPointerException("Key cannot by null"); } return filter.membershipTest(new Key(key.getBytes(StandardCharsets.UTF_8))); } /** * Serialize the bloom filter as a string. */ public String serializeToString() { ByteArrayOutputStream baos = new ByteArrayOutputStream(); DataOutputStream dos = new DataOutputStream(baos); try { filter.write(dos); byte[] bytes = baos.toByteArray(); dos.close(); return DatatypeConverter.printBase64Binary(bytes); } catch (IOException e) { throw new HoodieIndexException("Could not serialize BloomFilter instance", e); } } }