solr/contrib/analytics/src/java/org/apache/solr/analytics/stream/reservation/ReductionDataReservation.java

/*
 * 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.solr.analytics.stream.reservation;

import java.io.DataInput;
import java.io.DataOutput;

import org.apache.solr.analytics.function.reduction.data.ReductionDataCollector;
import org.apache.solr.analytics.stream.reservation.read.ReductionDataReader;
import org.apache.solr.analytics.stream.reservation.write.ReductionDataWriter;

/**
 * A reservation allows a {@link ReductionDataCollector} to specify a piece of data it needs to export from the shard.
 */
public abstract class ReductionDataReservation<A, E> {
  protected final A applier;
  protected final E extractor;

  protected ReductionDataReservation(A applier, E extractor) {
    this.applier = applier;
    this.extractor = extractor;
  }

  /**
   * Generate a {@link ReductionDataReader} that merges the set of data this reservation represents.
   *
   * @param input the shard input stream
   * @return a reader from the given input
   */
  public abstract ReductionDataReader<A> createReadStream(DataInput input);

  /**
   * Generate a {@link ReductionDataWriter} that exports the set of data this reservation represents.
   *
   * @param output the shard output stream
   * @return a writer to the given output
   */
  public abstract ReductionDataWriter<E> createWriteStream(DataOutput output);
}