library/src/main/java/com/datatorrent/lib/stream/Counter.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.lib.stream;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Operator;
import com.datatorrent.api.Operator.Unifier;

/**
 * An implementation of Operator and Unifier that counts the number of tuples delivered to it in each window and emits the count.
 * <p>
 * This is a pass through operator<br>
 * <br>
 * <b>StateFull : Yes</b>, tuples are counted over application window. <br>
 * <b>Partitions : Yes</b>, count is unified at output port. <br>
 * <b>Ports</b>:<br>
 * <b>input</b>: expects Object<br>
 * <b>output</b>: emits Integer<br>
 * <br>
 * @displayName: Counter
 * @category: stream
 * @tag: integer, object, count
 * @since 0.3.3
 */
public class Counter implements Operator, Unifier<Integer>
{
        /**
	 * Input port that takes objects to be counted in each window.
	 */
	public final transient DefaultInputPort<Object> input = new DefaultInputPort<Object>()
	{
		@Override
		public void process(Object tuple)
		{
			count++;
		}

	};
        
          /**
	 * Output port that takes emits count in each window.
	 */
	public final transient DefaultOutputPort<Integer> output = new DefaultOutputPort<Integer>()
	{
		@Override
		public Unifier<Integer> getUnifier()
		{
			return Counter.this;
		}

	};

	@Override
	public void beginWindow(long windowId)
	{
		count = 0;
	}

	@Override
	public void process(Integer tuple)
	{
		count += tuple;
	}

	@Override
	public void endWindow()
	{
		output.emit(count);
	}

	@Override
	public void setup(OperatorContext context)
	{
	}

	@Override
	public void teardown()
	{
	}

	private transient int count;
}