code: public static long getPosFromBlockOffset(long offsetInBlock, int bytesPerChecksum,
        int checksumSize) {
      // We only support to read full chunks, so offsetInBlock must be the boundary
      // of the chunks.
      assert offsetInBlock % bytesPerChecksum == 0;
      // The position in the file will be the same as the file size for the block
      // size.
      return getFileLengthFromBlockSize(offsetInBlock, bytesPerChecksum, checksumSize);
    }
docs: Translate from block offset to position in file.
  
  @param offsetInBlock
  @param bytesPerChecksum
  @param checksumSize
  @return