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.C;
  import java.io.IOException;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  /** Reads data from URI-identified resources. */
  public interface DataSource extends DataReader {
  
    /** A factory for {@link DataSource} instances. */
    interface Factory {
  
      /** Creates a {@link DataSource} instance. */
      DataSource createDataSource();
    }
  
    /**
     * Adds a {@link TransferListener} to listen to data transfers. This method is not thread-safe.
     *
     * @param transferListener A {@link TransferListener}.
     */
    void addTransferListener(TransferListener transferListener);
  
    /**
     * Opens the source to read the specified data. If an {@link IOException} is thrown, callers must
     * still call {@link #close()} to ensure that any partial effects of the invocation are cleaned
     * up.
     *
     * <p>The following edge case behaviors apply:
     *
     * <ul>
     *   <li>If the {@link DataSpec#position requested position} is within the resource, but the
     *       {@link DataSpec#length requested length} extends beyond the end of the resource, then
     *       {@link #open} will succeed and data from the requested position to the end of the
     *       resource will be made available through {@link #read}.
     *   <li>If the {@link DataSpec#position requested position} is equal to the length of the
     *       resource, then {@link #open} will succeed, and {@link #read} will immediately return
     *       {@link C#RESULT_END_OF_INPUT}.
     *   <li>If the {@link DataSpec#position requested position} is greater than the length of the
     *       resource, then {@link #open} will throw an {@link IOException} for which {@link
     *       DataSourceException#isCausedByPositionOutOfRange} will be {@code true}.
     * </ul>
     *
     * @param dataSpec Defines the data to be read.
     * @throws IOException If an error occurs opening the source. {@link DataSourceException} can be
     *     thrown or used as a cause of the thrown exception to specify the reason of the error.
     * @return The number of bytes that can be read from the opened source. For unbounded requests
     *     (i.e., requests where {@link DataSpec#length} equals {@link C#LENGTH_UNSET}) this value is
     *     the resolved length of the request, or {@link C#LENGTH_UNSET} if the length is still
     *     unresolved. For all other requests, the value returned will be equal to the request's
     *     {@link DataSpec#length}.
     */
    long open(DataSpec dataSpec) throws IOException;
  
    /**
     * When the source is open, returns the {@link Uri} from which data is being read. The returned
     * {@link Uri} will be identical to the one passed {@link #open(DataSpec)} in the {@link DataSpec}
     * unless redirection has occurred. If redirection has occurred, the {@link Uri} after redirection
     * is returned.
     *
     * @return The {@link Uri} from which data is being read, or null if the source is not open.
     */
    @Nullable
    Uri getUri();
  
    /**
     * When the source is open, returns the response headers associated with the last {@link #open}
     * call. Otherwise, returns an empty map.
     *
     * <p>Key look-up in the returned map is case-insensitive.
     */
    default Map<String, List<String>> getResponseHeaders() {
      return Collections.emptyMap();
    }
  
    /**
     * Closes the source. This method must be called even if the corresponding call to {@link
     * #open(DataSpec)} threw an {@link IOException}.
     *
     * @throws IOException If an error occurs closing the source.
     */
    void close() throws IOException;
  }
  