Use this method to set the data for this blob

def set_data(self, data):
		"Use this method to set the data for this blob"
		if data is None:
			self.data_size = 0
			self.data = None
			return
		self.data_size = len(data)
		# create a string buffer so that null bytes aren't interpreted
		#  as the end of the string
		self.data = ctypes.cast(ctypes.create_string_buffer(data), ctypes.c_void_p)