001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.io;
019
020import java.io.DataInput;
021import java.io.DataOutput;
022import java.io.IOException;
023import java.util.Collection;
024import java.util.HashMap;
025import java.util.Map;
026import java.util.Set;
027
028import org.apache.hadoop.classification.InterfaceAudience;
029import org.apache.hadoop.classification.InterfaceStability;
030import org.apache.hadoop.util.ReflectionUtils;
031
032/**
033 * A Writable Map.
034 */
035@InterfaceAudience.Public
036@InterfaceStability.Stable
037public class MapWritable extends AbstractMapWritable
038  implements Map<Writable, Writable> {
039
040  private Map<Writable, Writable> instance;
041  
042  /** Default constructor. */
043  public MapWritable() {
044    super();
045    this.instance = new HashMap<Writable, Writable>();
046  }
047  
048  /**
049   * Copy constructor.
050   * 
051   * @param other the map to copy from
052   */
053  public MapWritable(MapWritable other) {
054    this();
055    copy(other);
056  }
057  
058  /** {@inheritDoc} */
059  public void clear() {
060    instance.clear();
061  }
062
063  /** {@inheritDoc} */
064  public boolean containsKey(Object key) {
065    return instance.containsKey(key);
066  }
067
068  /** {@inheritDoc} */
069  public boolean containsValue(Object value) {
070    return instance.containsValue(value);
071  }
072
073  /** {@inheritDoc} */
074  public Set<Map.Entry<Writable, Writable>> entrySet() {
075    return instance.entrySet();
076  }
077
078  /** {@inheritDoc} */
079  public boolean equals(Object obj) {
080    if (this == obj) {
081      return true;
082    }
083
084    if (obj instanceof MapWritable) {
085      Map map = (Map) obj;
086      if (size() != map.size()) {
087        return false;
088      }
089
090      return entrySet().equals(map.entrySet());
091    }
092
093    return false;
094  }
095
096  /** {@inheritDoc} */
097  public Writable get(Object key) {
098    return instance.get(key);
099  }
100  
101  /** {@inheritDoc} */
102  public int hashCode() {
103    return 1 + this.instance.hashCode();
104  }
105
106  /** {@inheritDoc} */
107  public boolean isEmpty() {
108    return instance.isEmpty();
109  }
110
111  /** {@inheritDoc} */
112  public Set<Writable> keySet() {
113    return instance.keySet();
114  }
115
116  /** {@inheritDoc} */
117  @SuppressWarnings("unchecked")
118  public Writable put(Writable key, Writable value) {
119    addToMap(key.getClass());
120    addToMap(value.getClass());
121    return instance.put(key, value);
122  }
123
124  /** {@inheritDoc} */
125  public void putAll(Map<? extends Writable, ? extends Writable> t) {
126    for (Map.Entry<? extends Writable, ? extends Writable> e: t.entrySet()) {
127      put(e.getKey(), e.getValue());
128    }
129  }
130
131  /** {@inheritDoc} */
132  public Writable remove(Object key) {
133    return instance.remove(key);
134  }
135
136  /** {@inheritDoc} */
137  public int size() {
138    return instance.size();
139  }
140
141  /** {@inheritDoc} */
142  public Collection<Writable> values() {
143    return instance.values();
144  }
145  
146  // Writable
147  
148  /** {@inheritDoc} */
149  @Override
150  public void write(DataOutput out) throws IOException {
151    super.write(out);
152    
153    // Write out the number of entries in the map
154    
155    out.writeInt(instance.size());
156
157    // Then write out each key/value pair
158    
159    for (Map.Entry<Writable, Writable> e: instance.entrySet()) {
160      out.writeByte(getId(e.getKey().getClass()));
161      e.getKey().write(out);
162      out.writeByte(getId(e.getValue().getClass()));
163      e.getValue().write(out);
164    }
165  }
166
167  /** {@inheritDoc} */
168  @SuppressWarnings("unchecked")
169  @Override
170  public void readFields(DataInput in) throws IOException {
171    super.readFields(in);
172    
173    // First clear the map.  Otherwise we will just accumulate
174    // entries every time this method is called.
175    this.instance.clear();
176    
177    // Read the number of entries in the map
178    
179    int entries = in.readInt();
180    
181    // Then read each key/value pair
182    
183    for (int i = 0; i < entries; i++) {
184      Writable key = (Writable) ReflectionUtils.newInstance(getClass(
185          in.readByte()), getConf());
186      
187      key.readFields(in);
188      
189      Writable value = (Writable) ReflectionUtils.newInstance(getClass(
190          in.readByte()), getConf());
191      
192      value.readFields(in);
193      instance.put(key, value);
194    }
195  }
196}