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 */
018
019package org.apache.hadoop.io;
020
021import java.io.*;
022import java.lang.reflect.Array;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026
027/** A Writable for 2D arrays containing a matrix of instances of a class. */
028@InterfaceAudience.Public
029@InterfaceStability.Stable
030public class TwoDArrayWritable implements Writable {
031  private Class valueClass;
032  private Writable[][] values;
033
034  public TwoDArrayWritable(Class valueClass) {
035    this.valueClass = valueClass;
036  }
037
038  public TwoDArrayWritable(Class valueClass, Writable[][] values) {
039    this(valueClass);
040    this.values = values;
041  }
042
043  public Object toArray() {
044    int dimensions[] = {values.length, 0};
045    Object result = Array.newInstance(valueClass, dimensions);
046    for (int i = 0; i < values.length; i++) {
047      Object resultRow = Array.newInstance(valueClass, values[i].length);
048      Array.set(result, i, resultRow);
049      for (int j = 0; j < values[i].length; j++) {
050        Array.set(resultRow, j, values[i][j]);
051      }
052    }
053    return result;
054  }
055
056  public void set(Writable[][] values) { this.values = values; }
057
058  public Writable[][] get() { return values; }
059
060  @Override
061  public void readFields(DataInput in) throws IOException {
062    // construct matrix
063    values = new Writable[in.readInt()][];          
064    for (int i = 0; i < values.length; i++) {
065      values[i] = new Writable[in.readInt()];
066    }
067
068    // construct values
069    for (int i = 0; i < values.length; i++) {
070      for (int j = 0; j < values[i].length; j++) {
071        Writable value;                             // construct value
072        try {
073          value = (Writable)valueClass.newInstance();
074        } catch (InstantiationException e) {
075          throw new RuntimeException(e.toString());
076        } catch (IllegalAccessException e) {
077          throw new RuntimeException(e.toString());
078        }
079        value.readFields(in);                       // read a value
080        values[i][j] = value;                       // store it in values
081      }
082    }
083  }
084
085  @Override
086  public void write(DataOutput out) throws IOException {
087    out.writeInt(values.length);                 // write values
088    for (int i = 0; i < values.length; i++) {
089      out.writeInt(values[i].length);
090    }
091    for (int i = 0; i < values.length; i++) {
092      for (int j = 0; j < values[i].length; j++) {
093        values[i][j].write(out);
094      }
095    }
096  }
097}
098