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.C;
  import java.io.IOException;
  
  /**
   * A component from which streams of data can be read.
   */
  public interface DataSource {
  
    /**
     * A factory for {@link DataSource} instances.
     */
    interface Factory {
  
      /**
       * Creates a {@link DataSource} instance.
       */
      DataSource createDataSource();
  
    }
  
    /**
     * Opens the source to read the specified data.
     * <p>
     * Note: If an {@link IOException} is thrown, callers must still call {@link #close()} to ensure
     * that any partial effects of the invocation are cleaned up.
     *
     * @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;
  
    /**
     * Reads up to {@code length} bytes of data and stores them into {@code buffer}, starting at
     * index {@code offset}.
     * <p>
     * If {@code length} is zero then 0 is returned. Otherwise, if no data is available because the
     * end of the opened range has been reached, then {@link C#RESULT_END_OF_INPUT} is returned.
     * Otherwise, the call will block until at least one byte of data has been read and the number of
     * bytes read is returned.
     *
     * @param buffer The buffer into which the read data should be stored.
     * @param offset The start offset into {@code buffer} at which data should be written.
     * @param readLength The maximum number of bytes to read.
     * @return The number of bytes read, or {@link C#RESULT_END_OF_INPUT} if no data is available
     *     because the end of the opened range has been reached.
     * @throws IOException If an error occurs reading from the source.
     */
    int read(byte[] buffer, int offset, int readLength) 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.
     */
    Uri getUri();
  
    /**
     * Closes the source.
     * <p>
     * Note: This method must be called even if the corresponding call to {@link #open(DataSpec)}
     * threw an {@link IOException}. See {@link #open(DataSpec)} for more details.
     *
     * @throws IOException If an error occurs closing the source.
     */
    void close() throws IOException;
  
  }
  