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.crypto;
  
  import android.net.Uri;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.upstream.DataSource;
  import com.google.android.exoplayer2.upstream.DataSpec;
  import java.io.IOException;
  import javax.crypto.Cipher;
  
  /**
   * A {@link DataSource} that decrypts the data read from an upstream source.
   */
  public final class AesCipherDataSource implements DataSource {
  
    private final DataSource upstream;
    private final byte[] secretKey;
  
    private AesFlushingCipher cipher;
  
    public AesCipherDataSource(byte[] secretKey, DataSource upstream) {
      this.upstream = upstream;
      this.secretKey = secretKey;
    }
  
    @Override
    public long open(DataSpec dataSpec) throws IOException {
      long dataLength = upstream.open(dataSpec);
      long nonce = CryptoUtil.getFNV64Hash(dataSpec.key);
      cipher = new AesFlushingCipher(Cipher.DECRYPT_MODE, secretKey, nonce,
          dataSpec.absoluteStreamPosition);
      return dataLength;
    }
  
    @Override
    public int read(byte[] data, int offset, int readLength) throws IOException {
      if (readLength == 0) {
        return 0;
      }
      int read = upstream.read(data, offset, readLength);
      if (read == C.RESULT_END_OF_INPUT) {
        return C.RESULT_END_OF_INPUT;
      }
      cipher.updateInPlace(data, offset, read);
      return read;
    }
  
    @Override
    public void close() throws IOException {
      cipher = null;
      upstream.close();
    }
  
    @Override
    public Uri getUri() {
      return upstream.getUri();
    }
  
  }
  