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
   *
   *     https://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.avro.mapred;
  
  import java.io.IOException;
  import java.util.Iterator;
  
  import org.apache.hadoop.mapred.JobConf;
  import org.apache.hadoop.mapred.MapReduceBase;
  import org.apache.hadoop.mapred.OutputCollector;
  import org.apache.hadoop.mapred.Reporter;
  import org.apache.hadoop.mapred.Reducer;
  
  abstract class HadoopReducerBase<K, V, OUT, KO, VO> extends MapReduceBase
      implements Reducer<AvroKey<K>, AvroValue<V>, KO, VO> {
  
    private AvroReducer<K, V, OUT> reducer;
    private AvroCollector<OUT> collector;
  
    protected abstract AvroReducer<K, V, OUT> getReducer(JobConf conf);
  
    protected abstract AvroCollector<OUT> getCollector(OutputCollector<KO, VO> c);
  
    @Override
    public void configure(JobConf conf) {
      this.reducer = getReducer(conf);
    }
  
    class ReduceIterable implements Iterable<V>, Iterator<V> {
      private Iterator<AvroValue<V>> values;
  
      @Override
      public boolean hasNext() {
        return values.hasNext();
      }
  
      @Override
      public V next() {
        return values.next().datum();
      }
  
      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }
  
      @Override
      public Iterator<V> iterator() {
        return this;
      }
    }
  
    private ReduceIterable reduceIterable = new ReduceIterable();
  
    @Override
    public final void reduce(AvroKey<K> key, Iterator<AvroValue<V>> values, OutputCollector<KO, VO> out,
        Reporter reporter) throws IOException {
      if (this.collector == null)
        this.collector = getCollector(out);
      reduceIterable.values = values;
      reducer.reduce(key.datum(), reduceIterable, collector, reporter);
    }
  
    @Override
    public void close() throws IOException {
      this.reducer.close();
    }
  }
  