content: /*
   * 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.beam.runners.samza.transforms;
  
  import org.apache.beam.sdk.transforms.Combine;
  
  /**
   * Currently Beam only supports either throw away the accumulation or keep it after firing. This
   * CombineFn allows more flexibility to update the accumulation.
   */
  public abstract class UpdatingCombineFn<InputT, AccumT, OutputT>
      extends Combine.CombineFn<InputT, AccumT, OutputT> {
  
    /**
     * Returns an updated accumulator from the given accumulator after firing a window pane.
     *
     * <p>For efficiency, the input accumulator may be modified and returned.
     */
    public abstract AccumT updateAfterFiring(AccumT accumulator);
  }
  