content: /*
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.cassandra.db.commitlog;
  
  import java.io.DataInput;
  import java.nio.ByteBuffer;
  
  import org.apache.cassandra.io.util.DataPosition;
  import org.apache.cassandra.io.util.FileDataInput;
  import org.apache.cassandra.io.util.FileSegmentInputStream;
  
  /**
   * Each segment of an encrypted file may contain many encrypted chunks, and each chunk needs to be individually decrypted
   * to reconstruct the full segment.
   */
  public class EncryptedFileSegmentInputStream extends FileSegmentInputStream implements FileDataInput, DataInput
  {
      private final long segmentOffset;
      private final int expectedLength;
      private final ChunkProvider chunkProvider;
  
      /**
       * Offset representing the decrypted chunks already processed in this segment.
       */
      private int totalChunkOffset;
  
      public EncryptedFileSegmentInputStream(String filePath, long segmentOffset, int position, int expectedLength, ChunkProvider chunkProvider)
      {
          super(chunkProvider.nextChunk(), filePath, position);
          this.segmentOffset = segmentOffset;
          this.expectedLength = expectedLength;
          this.chunkProvider = chunkProvider;
      }
  
      public interface ChunkProvider
      {
          /**
           * Get the next chunk from the backing provider, if any chunks remain.
           * @return Next chunk, else null if no more chunks remain.
           */
          ByteBuffer nextChunk();
      }
  
      public long getFilePointer()
      {
          return segmentOffset + totalChunkOffset + buffer.position();
      }
  
      public boolean isEOF()
      {
          return totalChunkOffset + buffer.position() >= expectedLength;
      }
  
      public long bytesRemaining()
      {
          return expectedLength - (totalChunkOffset + buffer.position());
      }
  
      public void seek(long position)
      {
          long bufferPos = position - totalChunkOffset - segmentOffset;
          while (buffer != null && bufferPos > buffer.capacity())
          {
              // rebuffer repeatedly until we have reached desired position
              buffer.position(buffer.limit());
  
              // increases totalChunkOffset
              reBuffer();
              bufferPos = position - totalChunkOffset - segmentOffset;
          }
          if (buffer == null || bufferPos < 0 || bufferPos > buffer.capacity())
              throw new IllegalArgumentException(
                      String.format("Unable to seek to position %d in %s (%d bytes) in partial mode",
                              position,
                              getPath(),
                              segmentOffset + expectedLength));
          buffer.position((int) bufferPos);
      }
  
      public long bytesPastMark(DataPosition mark)
      {
          throw new UnsupportedOperationException();
      }
  
      public void reBuffer()
      {
          totalChunkOffset += buffer.position();
          buffer = chunkProvider.nextChunk();
      }
  }
  