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

[Nir Soffer]

On Mon, Feb 25, 2019 at 10:36 PM Eduardo Habkost <address@hidden>
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:
> > <address@hidden>
> >
> > Signed-off-by: Andrey Shinkevich <address@hidden>
> > Reported-by: Kevin Wolf <address@hidden>
> > ---
> >  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


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