code: def _GetDecryptedStreamSize(self):
      
      self._file_object.seek(0, os.SEEK_SET)
  
      self._decrypter = self._GetDecrypter()
      self._decrypted_data = b''
  
      encrypted_data_offset = 0
      encrypted_data_size = self._file_object.get_size()
      decrypted_stream_size = 0
  
      while encrypted_data_offset < encrypted_data_size:
        read_count = self._ReadEncryptedData(self._ENCRYPTED_DATA_BUFFER_SIZE)
        if read_count == 0:
          break
  
        encrypted_data_offset += read_count
        decrypted_stream_size += self._decrypted_data_size
  
      return decrypted_stream_size
docs: Retrieves the decrypted stream size.
  
      Returns:
        int: decrypted stream size.