Re: [Qemu-devel] [Qemu-block] [PATCH v2] iotests: handle TypeError for Python3 in test 242

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

On 26/02/2019 04:42, Nir Soffer wrote:
> On Mon, Feb 25, 2019 at 10:36 PM Eduardo Habkost <ehabkost@redhat.com 
> <mailto:ehabkost@redhat.com>> wrote:
> 
>     On Fri, Feb 22, 2019 at 02:26:13PM +0300, Andrey Shinkevich wrote:
>      > The data type for bytes in Python3 differs from the one in Python2.
>      > Those cases should be managed separately.
>      >
>      > v1:
>      > In the first version, the TypeError in Python3 was handled as the
>      > exception.
>      > Discussed in the e-mail thread with the Message ID:
>      >
>     <1550519997-253534-1-git-send-email-andrey.shinkevich@virtuozzo.com
>     <mailto:1550519997-253534-1-git-send-email-andrey.shinkevich@virtuozzo.com>>
>      >
>      > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com
>     <mailto:andrey.shinkevich@virtuozzo.com>>
>      > Reported-by: Kevin Wolf <kwolf@redhat.com <mailto:kwolf@redhat.com>>
>      > ---
>      >  tests/qemu-iotests/242 | 8 ++++++--
>      >  1 file changed, 6 insertions(+), 2 deletions(-)
>      >
>      > diff --git a/tests/qemu-iotests/242 b/tests/qemu-iotests/242
>      > index 16c65ed..446fbf8 100755
>      > --- a/tests/qemu-iotests/242
>      > +++ b/tests/qemu-iotests/242
>      > @@ -20,6 +20,7 @@
>      >
>      >  import iotests
>      >  import json
>      > +import sys
>      >  from iotests import qemu_img_create, qemu_io, qemu_img_pipe, \
>      >      file_path, img_info_log, log, filter_qemu_io
>      >
>      > @@ -65,9 +66,12 @@ def toggle_flag(offset):
>      >      with open(disk, "r+b") as f:
>      >          f.seek(offset, 0)
>      >          c = f.read(1)
>      > -        toggled = chr(ord(c) ^ bitmap_flag_unknown)
>      > +        toggled = ord(c) ^ bitmap_flag_unknown
>      >          f.seek(-1, 1)
>      > -        f.write(toggled)
>      > +        if sys.version_info.major >= 3:
>      > +            f.write(bytes([toggled]))
>      > +        else:
>      > +            f.write(chr(toggled))
> 
>     Pretending we are dealing with text strings and using str/ord is
>     a python2-specific quirk.  I think it would be nice to get rid of
>     it.
> 
>     Python 2 has bytearray(), which behaves more similarly to the
>     bytes type from Python 3.  If we use it, we can make the code
>     more python3-like:
> 
>     diff --git a/tests/qemu-iotests/242 b/tests/qemu-iotests/242
>     index 16c65edcd7..7794fd4a70 100755
>     --- a/tests/qemu-iotests/242
>     +++ b/tests/qemu-iotests/242
>     @@ -64,10 +64,12 @@ def write_to_disk(offset, size):
>       def toggle_flag(offset):
>           with open(disk, "r+b") as f:
>               f.seek(offset, 0)
>     -        c = f.read(1)
>     -        toggled = chr(ord(c) ^ bitmap_flag_unknown)
>     +        # The casts to bytearray() below are only necessary
>     +        # for Python 2 compatibility
>     +        c = bytearray(f.read(1))[0]
> 
> 
> This is simpler and makes the intent of the code more clear:
> 
>      flag, = struct.unpack("B", f.read(1))
> 
>     +        toggled = c ^ bitmap_flag_unknown
>               f.seek(-1, 1)
>     -        f.write(toggled)
>     +        f.write(bytearray([toggled]))
> 
> 
> For consistency, we can use struct.pack here:
> 
>      f.write(struct.pack("B", toggled))
> 
> Nir
> 

Thank you all. I am OK with this approach.
Will wait for Eric's response.

> 
> 
>       qemu_img_create('-f', iotests.imgfmt, disk, '1M')
> 
>     -- 
>     Eduardo
> 

-- 
With the best regards,
Andrey Shinkevich