/*
    * 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.writable.kryo.serializers;
  
  import com.esotericsoftware.kryo.Kryo;
  import com.esotericsoftware.kryo.io.Input;
  import com.esotericsoftware.kryo.serializers.FieldSerializer;
  import com.google.common.base.Preconditions;
  
  /**
   * Serializer used to deserialize data into object, instead of creating a new
   * value readIntoObject needs to be set right before deserialization is called
   * on it.
   *
   * @param <T> Object type
   */
  public class ReusableFieldSerializer<T> extends FieldSerializer<T> {
    /** Current object into which to deserialize */
    private T readIntoObject;
  
    /**
     * Creates new reusable field serializer for a given type.
     * @param kryo HadoopKryo object
     * @param type Type of object
     */
    public ReusableFieldSerializer(Kryo kryo, Class type) {
      super(kryo, type);
    }
  
    public void setReadIntoObject(T value) {
      this.readIntoObject = value;
    }
  
    @Override
    protected T create(Kryo kryo, Input input, Class<T> type) {
      Preconditions.checkNotNull(readIntoObject);
      Preconditions.checkState(readIntoObject.getClass().equals(type));
      T toReturn = readIntoObject;
      readIntoObject = null;
      return toReturn;
    }
  }