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 com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.PriorityTaskManager;
  import java.io.IOException;
  
  /**
   * 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 {
  
    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 long open(DataSpec dataSpec) throws IOException {
      priorityTaskManager.proceedOrThrow(priority);
      return upstream.open(dataSpec);
    }
  
    @Override
    public int read(byte[] buffer, int offset, int max) throws IOException {
      priorityTaskManager.proceedOrThrow(priority);
      return upstream.read(buffer, offset, max);
    }
  
    @Override
    public Uri getUri() {
      return upstream.getUri();
    }
  
    @Override
    public void close() throws IOException {
      upstream.close();
    }
  
  }
  