/*
    * 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.comm.aggregators;
  
  import java.io.IOException;
  
  import org.apache.giraph.comm.GlobalCommType;
  import org.apache.giraph.utils.WritableUtils;
  import org.apache.hadoop.io.Writable;
  
  /**
   * Implementation of {@link CountingOutputStream} which allows writing of
   * reduced values in the form of pair (name, type, value)
   *
   * There are two modes:
   * - when class of the value is written into the stream.
   * - when it isn't, and reader needs to know Class of the value in order
   *   to read it.
   */
  public class GlobalCommValueOutputStream extends CountingOutputStream {
    /** whether to write Class object for values into the stream */
    private final boolean writeClass;
  
    /**
     * Constructor
     *
     * @param writeClass boolean whether to write Class object for values
     */
    public GlobalCommValueOutputStream(boolean writeClass) {
      this.writeClass = writeClass;
    }
  
    /**
     * Write global communication object to the stream
     * and increment internal counter
     *
     * @param name Name
     * @param type Global communication type
     * @param value Object value
     * @return Number of bytes occupied by the stream
     * @throws IOException
     */
    public int addValue(String name, GlobalCommType type,
        Writable value) throws IOException {
      incrementCounter();
      dataOutput.writeUTF(name);
      dataOutput.writeByte(type.ordinal());
      if (writeClass) {
        WritableUtils.writeWritableObject(value, dataOutput);
      } else {
        value.write(dataOutput);
      }
      return getSize();
    }
  }