code: def _os_buffered_size(self):
          
  
          num_bytes_pointer = new(Security, 'size_t *')
          result = Security.SSLGetBufferedReadSize(
              self._session_context,
              num_bytes_pointer
          )
          handle_sec_error(result)
  
          return deref(num_bytes_pointer)
docs: Returns the number of bytes of decrypted data stored in the Secure
          Transport read buffer. This amount of data can be read from SSLRead()
          without calling self._socket.recv().
  
          :return:
              An integer - the number of available bytes