Re: [PATCH v12 09/11] qcow2_format.py: collect fields to dump in JSON format

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

06.08.2020 12:08, Andrey Shinkevich wrote:
> On 05.08.2020 19:58, Vladimir Sementsov-Ogievskiy wrote:
>> 30.07.2020 17:15, Andrey Shinkevich wrote:
>>> As __dict__ is being extended with class members we do not want to
>>> print, add the to_dict() method to classes that returns a dictionary
>>> with desired fields and their values. Extend it in subclass when
>>> necessary to print the final dictionary in the JSON output which
>>> follows.
>>>
>>> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>>> ---
>>>   tests/qemu-iotests/qcow2_format.py | 34 ++++++++++++++++++++++++++++++++++
>>>   1 file changed, 34 insertions(+)
>>>
>>> diff --git a/tests/qemu-iotests/qcow2_format.py b/tests/qemu-iotests/qcow2_format.py
>>> index 2000de3..a4114cb 100644
>>> --- a/tests/qemu-iotests/qcow2_format.py
>>> +++ b/tests/qemu-iotests/qcow2_format.py
>>> @@ -119,6 +119,9 @@ class Qcow2Struct(metaclass=Qcow2StructMeta):
>>>                 print('{:<25} {}'.format(f[2], value_str))
>>>   +    def to_dict(self):
>>> +        return dict((f[2], self.__dict__[f[2]]) for f in self.fields)
>>> +
>>>     class Qcow2BitmapExt(Qcow2Struct):
>>>   @@ -151,6 +154,11 @@ class Qcow2BitmapExt(Qcow2Struct):
>>>               print()
>>>               entry.dump()
>>>   +    def to_dict(self):
>>> +        fields_dict = super().to_dict()
>>> +        fields_dict['bitmap_directory'] = self.bitmap_directory
>>> +        return fields_dict
>>> +
>>>     class Qcow2BitmapDirEntry(Qcow2Struct):
>>>   @@ -189,6 +197,14 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
>>>           super(Qcow2BitmapDirEntry, self).dump()
>>>           self.bitmap_table.dump()
>>>   +    def to_dict(self):
>>> +        fields_dict = super().to_dict()
>>> +        fields_dict['bitmap_table'] = self.bitmap_table.entries
>>
>> the fact that we have to access internals of bitmap_table is not nice, but let's refactor it later.
>>
>>> +        bmp_name = dict(name=self.name)
>>> +        # Put the name ahead of the dict
>>
>> Aha. I don't think that ordering is necessary for json, but why not to order it a bit.
>>
>>> +        bme_dict = {**bmp_name, **fields_dict}
>>
>>
>> strange to create bmp_name dict just to unpack it. You may as well do
>>
>> bme_dict = {'name': self.name, **fields_dict}
>>
>>> +        return bme_dict
>>
>> bme_dict is extra variable: it's created just to return it, so, how about just
>>
>> return {'name': self.name, **fields_dict}
>>
>>
>> or, maybe
>>
>> return {
>>            'name': self.name,
>>            **super().to_dict(),
>>            'bitmap_table': self.bitmap_table.entries
>>        }
>>
>>> +
>>>     class Qcow2BitmapTableEntry(Qcow2Struct):
>>>   @@ -214,6 +230,9 @@ class Qcow2BitmapTableEntry(Qcow2Struct):
>>>           else:
>>>               self.type = 'all-zeroes'
>>>   +    def to_dict(self):
>>> +        return dict(type=self.type, offset=self.offset, reserved=self.reserved)
>>> +
>>
>> Python has a special syntax for creating dicts :), let's use:
>>
>> return {'type': self.type, 'offset': self.offset, 'reserved': self.reserved}
>>
>>
>>>     class Qcow2BitmapTable:
>>>   @@ -246,6 +265,9 @@ class QcowHeaderExtension(Qcow2Struct):
>>>               0x44415441: 'Data file'
>>>           }
>>>   +        def to_dict(self):
>>> +            return self.mapping.get(self.value, "<unknown>")
>>
>> aha, so, actually, to_dict() returns not dict, but string. So it should better be named to_json() (and return any json-dumpable object, like string or dict)
>>
>> and then, we can add to_json() method to Qcow2BitmapTable as well, to return list.
> 
> 
> So, should I refactor it now?
> 

Up to you. Better yes if not difficult


> 
> 
>>
>>
>>> +
>>>       fields = (
>>>           ('u32', Magic, 'magic'),
>>>           ('u32', '{}', 'length')
>>> @@ -308,6 +330,18 @@ class QcowHeaderExtension(Qcow2Struct):
>>>           else:
>>>               self.obj.dump()
>>>   +    def to_dict(self):
>>> +        fields_dict = super().to_dict()
>>> +        ext_name = dict(name=self.Magic(self.magic))
>>
>> strange that we have to create Magic object here... Ok, let's refactor it later
>>
>>> +        # Put the name ahead of the dict
>>> +        he_dict = {**ext_name, **fields_dict}
>>> +        if self.obj is not None:
>>> +            he_dict['data'] = self.obj
>>> +        else:
>>> +            he_dict['data_str'] = self.data_str
>>> +
>>> +        return he_dict
>>
>> again, let's avoid extra dict variables:
>>
>> res = {'name': self.Magic(self.magic), **super().to_dict()}
>> if ...
>>
>>
>>> +
>>>       @classmethod
>>>       def create(cls, magic, data):
>>>           return QcowHeaderExtension(magic, len(data), data)
>>>
>>
>>


-- 
Best regards,
Vladimir