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.content.ContentResolver;
  import android.content.Context;
  import android.content.res.AssetFileDescriptor;
  import android.net.Uri;
  import com.google.android.exoplayer2.C;
  import java.io.EOFException;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  
  /**
   * A {@link DataSource} for reading from a content URI.
   */
  public final class ContentDataSource implements DataSource {
  
    /**
     * Thrown when an {@link IOException} is encountered reading from a content URI.
     */
    public static class ContentDataSourceException extends IOException {
  
      public ContentDataSourceException(IOException cause) {
        super(cause);
      }
  
    }
  
    private final ContentResolver resolver;
    private final TransferListener<? super ContentDataSource> listener;
  
    private Uri uri;
    private AssetFileDescriptor assetFileDescriptor;
    private FileInputStream inputStream;
    private long bytesRemaining;
    private boolean opened;
  
    /**
     * @param context A context.
     */
    public ContentDataSource(Context context) {
      this(context, null);
    }
  
    /**
     * @param context A context.
     * @param listener An optional listener.
     */
    public ContentDataSource(Context context, TransferListener<? super ContentDataSource> listener) {
      this.resolver = context.getContentResolver();
      this.listener = listener;
    }
  
    @Override
    public long open(DataSpec dataSpec) throws ContentDataSourceException {
      try {
        uri = dataSpec.uri;
        assetFileDescriptor = resolver.openAssetFileDescriptor(uri, "r");
        if (assetFileDescriptor == null) {
          throw new FileNotFoundException("Could not open file descriptor for: " + uri);
        }
        inputStream = new FileInputStream(assetFileDescriptor.getFileDescriptor());
        long assetStartOffset = assetFileDescriptor.getStartOffset();
        long skipped = inputStream.skip(assetStartOffset + dataSpec.position) - assetStartOffset;
        if (skipped != dataSpec.position) {
          // We expect the skip to be satisfied in full. If it isn't then we're probably trying to
          // skip beyond the end of the data.
          throw new EOFException();
        }
        if (dataSpec.length != C.LENGTH_UNSET) {
          bytesRemaining = dataSpec.length;
        } else {
          long assetFileDescriptorLength = assetFileDescriptor.getLength();
          if (assetFileDescriptorLength == AssetFileDescriptor.UNKNOWN_LENGTH) {
            // The asset must extend to the end of the file. If FileInputStream.getChannel().size()
            // returns 0 then the remaining length cannot be determined.
            FileChannel channel = inputStream.getChannel();
            long channelSize = channel.size();
            bytesRemaining = channelSize == 0 ? C.LENGTH_UNSET : channelSize - channel.position();
          } else {
            bytesRemaining = assetFileDescriptorLength - skipped;
          }
        }
      } catch (IOException e) {
        throw new ContentDataSourceException(e);
      }
  
      opened = true;
      if (listener != null) {
        listener.onTransferStart(this, dataSpec);
      }
  
      return bytesRemaining;
    }
  
    @Override
    public int read(byte[] buffer, int offset, int readLength) throws ContentDataSourceException {
      if (readLength == 0) {
        return 0;
      } else if (bytesRemaining == 0) {
        return C.RESULT_END_OF_INPUT;
      }
  
      int bytesRead;
      try {
        int bytesToRead = bytesRemaining == C.LENGTH_UNSET ? readLength
            : (int) Math.min(bytesRemaining, readLength);
        bytesRead = inputStream.read(buffer, offset, bytesToRead);
      } catch (IOException e) {
        throw new ContentDataSourceException(e);
      }
  
      if (bytesRead == -1) {
        if (bytesRemaining != C.LENGTH_UNSET) {
          // End of stream reached having not read sufficient data.
          throw new ContentDataSourceException(new EOFException());
        }
        return C.RESULT_END_OF_INPUT;
      }
      if (bytesRemaining != C.LENGTH_UNSET) {
        bytesRemaining -= bytesRead;
      }
      if (listener != null) {
        listener.onBytesTransferred(this, bytesRead);
      }
      return bytesRead;
    }
  
    @Override
    public Uri getUri() {
      return uri;
    }
  
    @Override
    public void close() throws ContentDataSourceException {
      uri = null;
      try {
        if (inputStream != null) {
          inputStream.close();
        }
      } catch (IOException e) {
        throw new ContentDataSourceException(e);
      } finally {
        inputStream = null;
        try {
          if (assetFileDescriptor != null) {
            assetFileDescriptor.close();
          }
        } catch (IOException e) {
          throw new ContentDataSourceException(e);
        } finally {
          assetFileDescriptor = null;
          if (opened) {
            opened = false;
            if (listener != null) {
              listener.onTransferEnd(this);
            }
          }
        }
      }
    }
  
  }
  