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.Closeable;
  import java.io.IOException;
  import java.util.ArrayList;
  import org.apache.beam.runners.core.metrics.ExecutionStateTracker;
  import org.apache.beam.runners.core.metrics.ExecutionStateTracker.ExecutionState;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ByteArrayShufflePosition;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ShuffleBatchReader;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ShuffleEntry;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.ShufflePosition;
  import org.apache.beam.vendor.grpc.v1p69p0.com.google.protobuf.ByteString;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** ChunkingShuffleBatchReader reads data from a shuffle dataset using a ShuffleReader. */
  final class ChunkingShuffleBatchReader implements ShuffleBatchReader {
    private ShuffleReader reader;
    private ExecutionStateTracker tracker;
    private ExecutionState readState;
  
    public ChunkingShuffleBatchReader(
        BatchModeExecutionContext executionContext,
        DataflowOperationContext operationContext,
        ShuffleReader reader) {
      this.reader = reader;
      this.readState = operationContext.newExecutionState("read-shuffle");
      this.tracker = executionContext.getExecutionStateTracker();
    }
  
    @Override
    public ShuffleBatchReader.Batch read(
        @Nullable ShufflePosition startShufflePosition, @Nullable ShufflePosition endShufflePosition)
        throws IOException {
      byte @Nullable [] startPosition = ByteArrayShufflePosition.getPosition(startShufflePosition);
      byte @Nullable [] endPosition = ByteArrayShufflePosition.getPosition(endShufflePosition);
  
      ShuffleReader.ReadChunkResult result;
      try (Closeable trackedReadState = tracker.enterState(readState)) {
        result = reader.readIncludingPosition(startPosition, endPosition);
      }
      ByteArrayReader input = new ByteArrayReader(result.chunk);
      ArrayList<ShuffleEntry> entries = new ArrayList<>();
  
      while (input.available() > 0) {
        entries.add(getShuffleEntry(input));
      }
  
      return new Batch(
          entries,
          result.nextStartPosition == null
              ? null
              : ByteArrayShufflePosition.of(result.nextStartPosition));
    }
  
    /**
     * Extracts a ShuffleEntry by parsing bytes from a given InputStream.
     *
     * @param chunk chunk to read from
     * @return parsed ShuffleEntry
     */
    private ShuffleEntry getShuffleEntry(ByteArrayReader chunk) throws IOException {
      ByteString position = getFixedLengthPrefixedByteArray(chunk);
      ByteString key = getFixedLengthPrefixedByteArray(chunk);
      ByteString skey = getFixedLengthPrefixedByteArray(chunk);
      ByteString value = getFixedLengthPrefixedByteArray(chunk);
  
      return new ShuffleEntry(ByteArrayShufflePosition.of(position), key, skey, value);
    }
  
    /**
     * Extracts a length-prefix-encoded byte array from a given InputStream.
     *
     * @param chunk chunk to read from
     * @return parsed byte array
     */
    private static ByteString getFixedLengthPrefixedByteArray(ByteArrayReader chunk)
        throws IOException {
      int length = chunk.readInt();
      if (length < 0) {
        throw new IOException("invalid length: " + length);
      }
      return chunk.read(length);
    }
  }
  