content: /*
   * 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 tech.mlsql.common;
  
  import org.apache.hadoop.util.bloom.Key;
  import org.apache.hadoop.util.hash.Hash;
  
  import javax.xml.bind.DatatypeConverter;
  import java.io.*;
  import java.nio.charset.StandardCharsets;
  
  /**
   * 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);
      }
  
      public int size() {
          return this.filter.getVectorSize();
      }
  
      /**
       * 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 RuntimeException("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 RuntimeException("Could not serialize BloomFilter instance", e);
          }
      }
  }
  