/*

  * 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.giraph.graph;

 import org.apache.giraph.edge.Edge;

 import org.apache.giraph.utils.UnsafeByteArrayInputStream;

 import org.apache.giraph.utils.UnsafeByteArrayOutputStream;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import java.io.DataInput;

 import java.io.IOException;

 /**

  * Special version of vertex that holds the value in raw byte form to save

  * memory.

  *

  * @param <I> Vertex id

  * @param <V> Vertex data

  * @param <E> Edge data

  */

 public class ByteValueVertex<I extends WritableComparable,

         V extends Writable, E extends Writable>

         extends DefaultVertex<I, V, E> {

   /** Vertex value stored as raw bytes */

   private byte[] valueBytes;

   /** Value as an cached object that is only valid during the vertex update */

   private V cachedValue = null;

   @Override

   public V getValue() {

     if (cachedValue != null) {

       return cachedValue; // Return always same instance

     }

     DataInput dis = new UnsafeByteArrayInputStream(valueBytes);

     cachedValue = getConf().createVertexValue();

     try {

       cachedValue.readFields(dis);

     } catch (IOException ioe) {

       throw new RuntimeException("Could not deserialize vertex value", ioe);

     }

     // Forget the serialized data, because we have cached the object

     valueBytes = null;

     return cachedValue;

   }

   /**

    * Serializes the value to bytes, stored in field valueBytes

    * @param value new vertex value

    */

   private void setSerializedValue(V value) {

     UnsafeByteArrayOutputStream bos = new UnsafeByteArrayOutputStream();

     try {

       value.write(bos);

       bos.close();

     } catch (IOException ioe) {

       throw new RuntimeException("Could not serialize vertex value", ioe);

     }

     this.valueBytes = bos.toByteArray();

     cachedValue = null;

   }

   @Override

   public void setValue(V value) {

     if (cachedValue != null) {

       cachedValue = value;

     } else {

       setSerializedValue(value);

     }

   }

   @Override

   public void initialize(I id, V value, Iterable<Edge<I, E>> edges) {

     // Set the parent's value to null, and instead use our own setter

     super.initialize(id, null, edges);

     setValue(value);

   }

   @Override

   public void initialize(I id, V value) {

     super.initialize(id, null);

     setValue(value);

   }

   @Override

   public void unwrapMutableEdges() {

     // This method is called always after compute(vertex), so

     // we use this to commit the vertex value.

     if (cachedValue != null) {

       // This means the value has been requested from vertex

       // and possible mutated -- so we need to update the byte array

       setSerializedValue(cachedValue);

       cachedValue = null;  // Uncache the value

     }

     super.unwrapMutableEdges();

   }

 }