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.dataflow.worker.util.common.worker;
  
  import java.io.Closeable;
  import javax.annotation.concurrent.NotThreadSafe;
  import org.apache.beam.sdk.util.common.Reiterator;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * ShuffleEntryReader provides an interface for reading key/value entries from a shuffle dataset.
   */
  @NotThreadSafe
  public interface ShuffleEntryReader extends Closeable {
    /**
     * Returns an iterator that reads a range of entries from a shuffle dataset.
     *
     * @param startPosition encodes the initial key from where to read. This parameter may be null,
     *     indicating that the read should start with the first key in the dataset.
     * @param endPosition encodes the key "just past" the end of the range to be read; keys up to
     *     endPosition will be returned, but keys equal to or greater than endPosition will not. This
     *     parameter may be null, indicating that the read should end just past the last key in the
     *     dataset (that is, the last key in the dataset will be included in the read, as long as that
     *     key is greater than or equal to startPosition).
     * @return a {@link Reiterator} over the requested range of entries.
     */
    Reiterator<ShuffleEntry> read(
        @Nullable ShufflePosition startPosition, @Nullable ShufflePosition endPosition);
  }
  