Re: [PATCH v10 08/10] qcow2.py: Introduce '-j' key to dump in JSON format

[Vladimir Sementsov-Ogievskiy]

14.07.2020 00:36, Andrey Shinkevich wrote:
> Add the command key to the qcow2.py arguments list to dump QCOW2
> metadata in JSON format. Here is the suggested way to do that. The
> implementation of the dump in JSON format is in the patch that follows.
>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   tests/qemu-iotests/qcow2.py        | 19 +++++++++++++++----
>   tests/qemu-iotests/qcow2_format.py | 16 ++++++++--------
>   2 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/tests/qemu-iotests/qcow2.py b/tests/qemu-iotests/qcow2.py
> index 0910e6a..7402279 100755
> --- a/tests/qemu-iotests/qcow2.py
> +++ b/tests/qemu-iotests/qcow2.py
> @@ -26,16 +26,19 @@ from qcow2_format import (
>   )
>   
>   
> +dump_json = False
> +
> +
>   def cmd_dump_header(fd):
>       h = QcowHeader(fd)
> -    h.dump()
> +    h.dump(dump_json)
>       print()
> -    h.dump_extensions()
> +    h.dump_extensions(dump_json)
>   
>   
>   def cmd_dump_header_exts(fd):
>       h = QcowHeader(fd)
> -    h.dump_extensions()
> +    h.dump_extensions(dump_json)
>   
>   
>   def cmd_set_header(fd, name, value):
> @@ -134,6 +137,11 @@ cmds = [
>   
>   
>   def main(filename, cmd, args):
> +    global dump_json
> +    dump_json = '-j' in sys.argv
> +    if dump_json:
> +        sys.argv.remove('-j')
> +        args.remove('-j')

I'd prefer to access sys.argv in one place (in "if __name__ ...").

>       fd = open(filename, "r+b")
>       try:
>           for name, handler, num_args, desc in cmds:
> @@ -151,11 +159,14 @@ def main(filename, cmd, args):
>   
>   
>   def usage():
> -    print("Usage: %s <file> <cmd> [<arg>, ...]" % sys.argv[0])
> +    print("Usage: %s <file> <cmd> [<arg>, ...] [<key>, ...]" % sys.argv[0])
>       print("")
>       print("Supported commands:")
>       for name, handler, num_args, desc in cmds:
>           print("    %-20s - %s" % (name, desc))
> +    print("")
> +    print("Supported keys:")
> +    print("    %-20s - %s" % ('-j', 'Dump in JSON format'))
>   
>   
>   if __name__ == '__main__':
> diff --git a/tests/qemu-iotests/qcow2_format.py 
> b/tests/qemu-iotests/qcow2_format.py
> index 2c78d46..e0e14b5 100644
> --- a/tests/qemu-iotests/qcow2_format.py
> +++ b/tests/qemu-iotests/qcow2_format.py
> @@ -109,7 +109,7 @@ class Qcow2Struct(metaclass=Qcow2StructMeta):
>           self.__dict__ = dict((field[2], values[i])
>                                for i, field in enumerate(self.fields))
>   
> -    def dump(self):
> +    def dump(self, dump_json=None):
>           for f in self.fields:
>               value = self.__dict__[f[2]]
>               if isinstance(f[1], str):
> @@ -145,8 +145,8 @@ class Qcow2BitmapExt(Qcow2Struct):
>               [Qcow2BitmapDirEntry(fd, cluster_size=self.cluster_size)
>                for _ in range(self.nb_bitmaps)]
>   
> -    def dump(self):
> -        super().dump()
> +    def dump(self, dump_json=None):

strange to make None the default value for boolean. Why not just False?

Also, why not call it just "json"? We are already in "dump" context, no needs 
to add prefix to the name.

> +        super().dump(dump_json)
>           for entry in self.bitmap_directory:
>               print()
>               entry.dump()

How will it work? You are interleaving json dump and non-json?

Looking at this, I think that json and non-json dumps has more differences than 
similarities, and it probably simpler to make a separate function dump_json.. 
But I'm absolutely against an option, if it will be done consistently.

> @@ -190,7 +190,7 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
>           self.bitmap_table = Qcow2BitmapTable(raw_table=table,
>                                                cluster_size=self.cluster_size)
>   
> -    def dump(self):
> +    def dump(self, dump_json=None):
>           print(f'{"Bitmap name":<25} {self.name}')
>           super(Qcow2BitmapDirEntry, self).dump()
>           self.bitmap_table.dump()

Here the new option just not passed to the nested dump() calls..

> @@ -291,13 +291,13 @@ class QcowHeaderExtension(Qcow2Struct):
>                       data_str = '<binary>'
>                   self.data_str = data_str
>   
> -    def dump(self):
> +    def dump(self, dump_json=None):
>           super().dump()
>   
>           if self.obj is None:
>               print(f'{"data":<25} {self.data_str}')
>           else:
> -            self.obj.dump()
> +            self.obj.dump(dump_json)
>   
>       @classmethod
>       def create(cls, magic, data):
> @@ -396,8 +396,8 @@ class QcowHeader(Qcow2Struct):
>           buf = buf[0:header_bytes-1]
>           fd.write(buf)
>   
> -    def dump_extensions(self):
> +    def dump_extensions(self, dump_json=None):
>           for ex in self.extensions:
>               print('Header extension:')
> -            ex.dump()
> +            ex.dump(dump_json)
>               print()


--
Best regards,
Vladimir