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 
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.shinkev...@virtuozzo.com>
> >
> > Signed-off-by: Andrey Shinkevich 
> > Reported-by: Kevin Wolf 
> > ---
> >  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
>
>

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

[Andrey Shinkevich]

On 26/02/2019 04:42, Nir Soffer wrote:
> On Mon, Feb 25, 2019 at 10:36 PM Eduardo Habkost  > 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.shinkev...@virtuozzo.com
> 
> >
>  >
>  > Signed-off-by: Andrey Shinkevich  >
>  > Reported-by: Kevin Wolf mailto:kw...@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

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

[Eduardo Habkost]

On Tue, Feb 26, 2019 at 03:42:11AM +0200, Nir Soffer wrote:
> On Mon, Feb 25, 2019 at 10:36 PM Eduardo Habkost 
[...]
> > -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))

That's perfect.  Thanks for the suggestion!

-- 
Eduardo

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

[Eric Blake]

On 2/26/19 4:39 AM, Andrey Shinkevich wrote:

>> +++ 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.

That looks better. Peter hasn't applied my pull request yet, so you have
time to submit a formal v3 (making it easier for me to 'git am' it
rather than reconstruct from this email), and then I will update my pull
request to use this improved version.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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

[Andrey Shinkevich]

On 26/02/2019 17:06, Eric Blake wrote:
> On 2/26/19 4:39 AM, Andrey Shinkevich wrote:
> 
>>>  +++ 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.
> 
> That looks better. Peter hasn't applied my pull request yet, so you have
> time to submit a formal v3 (making it easier for me to 'git am' it
> rather than reconstruct from this email), and then I will update my pull
> request to use this improved version.
> 
Noted

-- 
With the best regards,
Andrey Shinkevich