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;
  
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ByteArrayShufflePosition;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.NativeReader;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ShuffleEntry;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ShuffleEntryReader;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.util.CoderUtils;
  import org.apache.beam.vendor.grpc.v1p69p0.com.google.protobuf.ByteString;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A source that reads from a shuffled dataset, without any key grouping. Returns just the values.
   * (This reader is for an UNGROUPED shuffle session.)
   *
   * @param <T> the type of the elements read from the source
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class UngroupedShuffleReader<T> extends NativeReader<T> {
    final byte[] shuffleReaderConfig;
    final String startShufflePosition;
    final String stopShufflePosition;
    final Coder<T> coder;
    private final BatchModeExecutionContext executionContext;
    private final DataflowOperationContext operationContext;
  
    public UngroupedShuffleReader(
        @SuppressWarnings("unused") PipelineOptions options,
        byte[] shuffleReaderConfig,
        @Nullable String startShufflePosition,
        @Nullable String stopShufflePosition,
        Coder<T> coder,
        BatchModeExecutionContext executionContext,
        DataflowOperationContext operationContext) {
      this.shuffleReaderConfig = shuffleReaderConfig;
      this.startShufflePosition = startShufflePosition;
      this.stopShufflePosition = stopShufflePosition;
      this.coder = coder;
      this.executionContext = executionContext;
      this.operationContext = operationContext;
    }
  
    @Override
    public NativeReaderIterator<T> iterator() throws IOException {
      return iterator(
          new ApplianceShuffleEntryReader(
              shuffleReaderConfig, executionContext, operationContext, false /* no caching */));
    }
  
    /**
     * Creates an iterator on top of the given entry reader.
     *
     * <p>Takes "ownership" of the reader: closes the reader once the iterator is closed.
     */
    UngroupedShuffleReaderIterator<T> iterator(ShuffleEntryReader reader) {
      return new UngroupedShuffleReaderIterator<>(this, reader);
    }
  
    /** A ReaderIterator that reads from a ShuffleEntryReader and extracts just the values. */
    @VisibleForTesting
    static class UngroupedShuffleReaderIterator<T> extends NativeReaderIterator<T> {
      private Iterator<ShuffleEntry> iterator;
      private T current;
      private UngroupedShuffleReader<T> shuffleReader;
      private final ShuffleEntryReader entryReader;
  
      UngroupedShuffleReaderIterator(
          UngroupedShuffleReader<T> shuffleReader, ShuffleEntryReader entryReader) {
        this.iterator =
            entryReader.read(
                shuffleReader.startShufflePosition == null
                    ? null
                    : ByteArrayShufflePosition.fromBase64(shuffleReader.startShufflePosition),
                shuffleReader.stopShufflePosition == null
                    ? null
                    : ByteArrayShufflePosition.fromBase64(shuffleReader.stopShufflePosition));
        this.shuffleReader = shuffleReader;
        this.entryReader = entryReader;
      }
  
      @Override
      public boolean start() throws IOException {
        return advance();
      }
  
      @Override
      public boolean advance() throws IOException {
        if (!iterator.hasNext()) {
          current = null;
          return false;
        }
        ShuffleEntry record = iterator.next();
        // Throw away the primary and the secondary keys.
        ByteString value = record.getValue();
        shuffleReader.notifyElementRead(record.length());
        current = CoderUtils.decodeFromByteString(shuffleReader.coder, value);
        return true;
      }
  
      @Override
      public T getCurrent() throws NoSuchElementException {
        if (current == null) {
          throw new NoSuchElementException();
        }
        return current;
      }
  
      @Override
      public void close() throws IOException {
        entryReader.close();
      }
    }
  }
  