content: /*
   * Copyright (C) 2016 The Android Open Source Project
   *
   * Licensed 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 com.google.android.exoplayer2.upstream;
  
  import android.net.Uri;
  import androidx.annotation.Nullable;
  import com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.PriorityTaskManager;
  import java.io.IOException;
  import java.util.List;
  import java.util.Map;
  
  /**
   * A {@link DataSource} that can be used as part of a task registered with a {@link
   * PriorityTaskManager}.
   *
   * <p>Calls to {@link #open(DataSpec)} and {@link #read(byte[], int, int)} are allowed to proceed
   * only if there are no higher priority tasks registered to the {@link PriorityTaskManager}. If
   * there exists a higher priority task then {@link PriorityTaskManager.PriorityTooLowException} is
   * thrown.
   *
   * <p>Instances of this class are intended to be used as parts of (possibly larger) tasks that are
   * registered with the {@link PriorityTaskManager}, and hence do <em>not</em> register as tasks
   * themselves.
   */
  public final class PriorityDataSource implements DataSource {
  
    /** {@link DataSource.Factory} for {@link PriorityDataSource} instances. */
    public static final class Factory implements DataSource.Factory {
  
      private final DataSource.Factory upstreamFactory;
      private final PriorityTaskManager priorityTaskManager;
      private final int priority;
  
      /**
       * Creates an instance.
       *
       * @param upstreamFactory A {@link DataSource.Factory} that provides upstream {@link DataSource
       *     DataSources} for {@link PriorityDataSource} instances created by the factory.
       * @param priorityTaskManager The {@link PriorityTaskManager} to which tasks using {@link
       *     PriorityDataSource} instances created by this factory will be registered.
       * @param priority The priority of the tasks using {@link PriorityDataSource} instances created
       *     by this factory.
       */
      public Factory(
          DataSource.Factory upstreamFactory, PriorityTaskManager priorityTaskManager, int priority) {
        this.upstreamFactory = upstreamFactory;
        this.priorityTaskManager = priorityTaskManager;
        this.priority = priority;
      }
  
      @Override
      public PriorityDataSource createDataSource() {
        return new PriorityDataSource(
            upstreamFactory.createDataSource(), priorityTaskManager, priority);
      }
    }
  
    private final DataSource upstream;
    private final PriorityTaskManager priorityTaskManager;
    private final int priority;
  
    /**
     * @param upstream The upstream {@link DataSource}.
     * @param priorityTaskManager The priority manager to which the task is registered.
     * @param priority The priority of the task.
     */
    public PriorityDataSource(
        DataSource upstream, PriorityTaskManager priorityTaskManager, int priority) {
      this.upstream = Assertions.checkNotNull(upstream);
      this.priorityTaskManager = Assertions.checkNotNull(priorityTaskManager);
      this.priority = priority;
    }
  
    @Override
    public void addTransferListener(TransferListener transferListener) {
      Assertions.checkNotNull(transferListener);
      upstream.addTransferListener(transferListener);
    }
  
    @Override
    public long open(DataSpec dataSpec) throws IOException {
      priorityTaskManager.proceedOrThrow(priority);
      return upstream.open(dataSpec);
    }
  
    @Override
    public int read(byte[] buffer, int offset, int length) throws IOException {
      priorityTaskManager.proceedOrThrow(priority);
      return upstream.read(buffer, offset, length);
    }
  
    @Override
    @Nullable
    public Uri getUri() {
      return upstream.getUri();
    }
  
    @Override
    public Map<String, List<String>> getResponseHeaders() {
      return upstream.getResponseHeaders();
    }
  
    @Override
    public void close() throws IOException {
      upstream.close();
    }
  }
  