container.py 文件源码

def render(self, ctx=None):
        '''
        :param ctx: rendering context in which the method was called
        :rtype: `Bits`
        :return: rendered value of the container
        '''
        self._initialize()
        render_count = 1
        if ctx is None:
            ctx = RenderContext()
            if self._need_second_pass:
                render_count = 2
        ctx.push(self)
        if self.is_default():
            self._current_rendered = self._default_rendered
        else:
            if self.offset is None:
                self.offset = 0
            for i in range(render_count):
                offset = self.offset
                rendered = BitArray()
                for field in self._fields:
                    field.set_offset(offset)
                    frendered = field.render(ctx)
                    if not isinstance(frendered, Bits):
                        raise KittyException('the field %s:%s was rendered to type %s, you should probably wrap it with appropriate encoder' % (
                            field.get_name(), type(field), type(frendered)))
                    rendered.append(frendered)
                    offset += len(frendered)
                self.set_current_value(rendered)
        ctx.pop()
        return self._current_rendered