Re: [PATCH v10 09/10] qcow2_format.py: collect fields to dump in JSON format

[Andrey Shinkevich]

On 16.07.2020 13:24, Vladimir Sementsov-Ogievskiy wrote:
> 14.07.2020 00:36, Andrey Shinkevich wrote:
> > As __dict__ is being extended with class members we do not want to
> > print, make a light copy of the initial __dict__ and extend the copy
> > by adding lists we have to print in the JSON output.
> >
> > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> > ---
> >   tests/qemu-iotests/qcow2_format.py | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/tests/qemu-iotests/qcow2_format.py 
> > b/tests/qemu-iotests/qcow2_format.py
> > index e0e14b5..83c3482 100644
> > --- a/tests/qemu-iotests/qcow2_format.py
> > +++ b/tests/qemu-iotests/qcow2_format.py
> > @@ -109,6 +109,8 @@ class Qcow2Struct(metaclass=Qcow2StructMeta):
> >           self.__dict__ = dict((field[2], values[i])
> >                                for i, field in enumerate(self.fields))
> >   +        self.fields_dict = self.__dict__.copy()
>
> No, I don't like that. Keeping two copies of all the data is bad idea. 
> If you want to select some fields, add a method (dump_json() ?) Which 
> will collect the fields you want in a dict and return that new dict. 
> But don't store object attributes twice.

Not really. It makes a light copy that stores only references to the 
desired fields.

Andrey


> > +
> >       def dump(self, dump_json=None):
> >           for f in self.fields:
> >               value = self.__dict__[f[2]]
> > @@ -144,6 +146,7 @@ class Qcow2BitmapExt(Qcow2Struct):
> >           self.bitmap_directory = \
> >               [Qcow2BitmapDirEntry(fd, cluster_size=self.cluster_size)
> >                for _ in range(self.nb_bitmaps)]
> > + self.fields_dict.update(bitmap_directory=self.bitmap_directory)
> >         def dump(self, dump_json=None):
> >           super().dump(dump_json)
> > @@ -189,6 +192,7 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
> >           table = [e[0] for e in struct.iter_unpack('>Q', 
> > fd.read(table_size))]
> >           self.bitmap_table = Qcow2BitmapTable(raw_table=table,
> > cluster_size=self.cluster_size)
> > +        self.fields_dict.update(bitmap_table=self.bitmap_table)
> >         def dump(self, dump_json=None):
> >           print(f'{"Bitmap name":<25} {self.name}')