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/**
 * 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 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.
 * 

* This is a pass through operator
*
* StateFull : Yes, tuples are counted over application window.
* Partitions : Yes, count is unified at output port.
* Ports:
* input: expects Object
* output: emits Integer
*
* @displayName Counter * @category Stream Manipulators * @tags integer, object, count * @since 0.3.3 */ public class Counter implements Operator, Unifier { /** * Input port that takes objects to be counted in each window. */ public final transient DefaultInputPort input = new DefaultInputPort() { @Override public void process(Object tuple) { count++; } }; /** * Output port that takes emits count in each window. */ public final transient DefaultOutputPort output = new DefaultOutputPort() { @Override public Unifier 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; }