/**
*
* Copyright (c) 2005, European Commission project OneLab under contract 034819
* (http://www.one-lab.org)
*
* All rights reserved.
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the distribution.
* - Neither the name of the University Catholique de Louvain - UCL
* nor the names of its contributors may be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/**
* 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.hadoop.util.bloom;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Collection;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.hash.Hash;
/**
* Defines the general behavior of a filter.
* <p>
* A filter is a data structure which aims at offering a lossy summary of a set <code>A</code>. The
* key idea is to map entries of <code>A</code> (also called <i>keys</i>) into several positions
* in a vector through the use of several hash functions.
* <p>
* Typically, a filter will be implemented as a Bloom filter (or a Bloom filter extension).
* <p>
* It must be extended in order to define the real behavior.
*
* @see Key The general behavior of a key
* @see HashFunction A hash function
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public abstract class Filter implements Writable {
private static final int VERSION = -1; // negative to accommodate for old format
/** The vector size of <i>this</i> filter. */
protected int vectorSize;
/** The hash function used to map a key to several positions in the vector. */
protected HashFunction hash;
/** The number of hash function to consider. */
protected int nbHash;
/** Type of hashing function to use. */
protected int hashType;
protected Filter() {}
/**
* Constructor.
* @param vectorSize The vector size of <i>this</i> filter.
* @param nbHash The number of hash functions to consider.
* @param hashType type of the hashing function (see {@link Hash}).
*/
protected Filter(int vectorSize, int nbHash, int hashType) {
this.vectorSize = vectorSize;
this.nbHash = nbHash;
this.hashType = hashType;
this.hash = new HashFunction(this.vectorSize, this.nbHash, this.hashType);
}
/**
* Adds a key to <i>this</i> filter.
* @param key The key to add.
*/
public abstract void add(Key key);
/**
* Determines wether a specified key belongs to <i>this</i> filter.
* @param key The key to test.
* @return boolean True if the specified key belongs to <i>this</i> filter.
* False otherwise.
*/
public abstract boolean membershipTest(Key key);
/**
* Peforms a logical AND between <i>this</i> filter and a specified filter.
* <p>
* <b>Invariant</b>: The result is assigned to <i>this</i> filter.
* @param filter The filter to AND with.
*/
public abstract void and(Filter filter);
/**
* Peforms a logical OR between <i>this</i> filter and a specified filter.
* <p>
* <b>Invariant</b>: The result is assigned to <i>this</i> filter.
* @param filter The filter to OR with.
*/
public abstract void or(Filter filter);
/**
* Peforms a logical XOR between <i>this</i> filter and a specified filter.
* <p>
* <b>Invariant</b>: The result is assigned to <i>this</i> filter.
* @param filter The filter to XOR with.
*/
public abstract void xor(Filter filter);
/**
* Performs a logical NOT on <i>this</i> filter.
* <p>
* The result is assigned to <i>this</i> filter.
*/
public abstract void not();
/**
* Adds a list of keys to <i>this</i> filter.
* @param keys The list of keys.
*/
public void add(List<Key> keys){
if(keys == null) {
throw new IllegalArgumentException("ArrayList<Key> may not be null");
}
for(Key key: keys) {
add(key);
}
}//end add()
/**
* Adds a collection of keys to <i>this</i> filter.
* @param keys The collection of keys.
*/
public void add(Collection<Key> keys){
if(keys == null) {
throw new IllegalArgumentException("Collection<Key> may not be null");
}
for(Key key: keys) {
add(key);
}
}//end add()
/**
* Adds an array of keys to <i>this</i> filter.
* @param keys The array of keys.
*/
public void add(Key[] keys){
if(keys == null) {
throw new IllegalArgumentException("Key[] may not be null");
}
for(int i = 0; i < keys.length; i++) {
add(keys[i]);
}
}//end add()
// Writable interface
public void write(DataOutput out) throws IOException {
out.writeInt(VERSION);
out.writeInt(this.nbHash);
out.writeByte(this.hashType);
out.writeInt(this.vectorSize);
}
public void readFields(DataInput in) throws IOException {
int ver = in.readInt();
if (ver > 0) { // old unversioned format
this.nbHash = ver;
this.hashType = Hash.JENKINS_HASH;
} else if (ver == VERSION) {
this.nbHash = in.readInt();
this.hashType = in.readByte();
} else {
throw new IOException("Unsupported version: " + ver);
}
this.vectorSize = in.readInt();
this.hash = new HashFunction(this.vectorSize, this.nbHash, this.hashType);
}
}//end class