mapped_struct.py 文件源码

def get_packer(self, obj):
        has_bitmap, none_bitmap, present_bitmap = self._get_bitmaps(obj)
        rv = self.packer_cache.get(present_bitmap)
        if rv is None:
            packer = struct.Struct("".join([
                self.bitmap_packer.format,
            ] + [
                self.slot_struct_types[slot]
                for i,slot in enumerate(self.slot_keys)
                if present_bitmap & (cython.cast(cython.ulonglong, 1) << i)
            ]))
            alignment = self.alignment
            size = packer.size
            padding = (size + alignment - 1) / alignment * alignment - size
            self.packer_cache[present_bitmap] = rv = (packer, padding)
        return rv