[PATCH evemu 2/2] python: encode/decode C strings for Python 3

[Benjamin Tissoires]

On Wed, Nov 9, 2016 at 6:03 AM, Peter Hutterer <peter.hutterer at who-t.net> wrote:
> https://bugs.freedesktop.org/show_bug.cgi?id=97458
>
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>  python/evemu/__init__.py | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/python/evemu/__init__.py b/python/evemu/__init__.py
> index 230559f..323bcaf 100644
> --- a/python/evemu/__init__.py
> +++ b/python/evemu/__init__.py
> @@ -50,20 +50,26 @@ def event_get_value(event_type, event_code = None):
>
>      if isinstance(event_type, int):
>          event_type = _libevdev.libevdev_event_type_get_name(event_type)
> -        if event_type == 0: # NULL
> +        if event_type is None:

These changes seemed to be different than the ones mentioned in the commit.
0 and None is rather different and I'd like to be sure we are not
screwing anything before applying this patch (which is why I applied
only 1/2).

>              return None
>
> -    t = _libevdev.libevdev_event_type_from_name(str(event_type))
> +        event_type = event_type.decode("iso8859-1")
> +
> +    event_type = str(event_type).encode("iso8859-1")

I had to run the python CLI to understand what was going on. But I am
still not sure about the end result (the commit message would need to
be extended):

When run under python2, _libevdev.libevdev_event_type_get_name()
returns a plain "str" which can be reused immediately by
_libevdev.libevdev_event_type_from_name().
But when run under python3, _libevdev.libevdev_event_type_get_name()
returns a bytes (b"SOMETHING"). But then
_libevdev.libevdev_event_type_from_name() also requires a bytes string
as argument.

So yes, I understand why there is a need to have the decode/encode
dance (to actually have the type libevdev_event_type_from_name()
expects).

But why do we need to keep around the cast to a str? It looks like the
original str() call was to convert the bytes string into a pure
string. But the call was not working (returns something like
"b'EV_KEY'"), so unless I am missing something, I'd rather drop this.

Also, how about we stick to string only (not bytes) for local
variables (by calling t =
_libevdev.libevdev_event_type_from_name(event_type.encode("iso8859-1")))?

Cheers,
Benjamin

> +    t = _libevdev.libevdev_event_type_from_name(event_type)
>
>      if event_code is None:
>          return None if t < 0 else t
>
>      if isinstance(event_code, int):
>          event_code = _libevdev.libevdev_event_code_get_name(t, event_code)
> -        if event_code == 0: # NULL
> +        if event_code is None: # NULL
>              return None
>
> -    c = _libevdev.libevdev_event_code_from_name(t, str(event_code))
> +        event_code = event_code.decode("iso8859-1")
> +
> +    event_code = str(event_code).encode("iso8859-1")
> +    c = _libevdev.libevdev_event_code_from_name(t, event_code)
>
>      return None if c < 0 else c
>
> @@ -84,7 +90,11 @@ def event_get_name(event_type, event_code = None):
>
>      if event_code is None:
>          type_name = _libevdev.libevdev_event_type_get_name(event_type)
> -        return None if type_name == 0 else type_name
> +
> +        if type_name is None:
> +            return None
> +
> +        return type_name.decode("iso8859-1")
>
>      if not isinstance(event_code, int):
>          event_code = event_get_value(event_type, event_code)
> @@ -93,8 +103,10 @@ def event_get_name(event_type, event_code = None):
>          return None
>
>      code_name = _libevdev.libevdev_event_code_get_name(event_type, event_code)
> +    if code_name is None:
> +        return None
>
> -    return None if code_name == 0 else code_name
> +    return code_name.decode("iso8859-1")
>
>  def input_prop_get_name(prop):
>      """
> @@ -107,7 +119,7 @@ def input_prop_get_name(prop):
>          return None
>
>      prop = _libevdev.libevdev_property_get_name(prop)
> -    return None if prop == 0 else prop
> +    return None if prop is None else prop.decode("iso8859-1")
>
>  def input_prop_get_value(prop):
>      """
> @@ -119,7 +131,8 @@ def input_prop_get_value(prop):
>      if prop is None:
>          return None
>
> -    prop = _libevdev.libevdev_property_from_name(str(prop))
> +    prop = str(prop).encode("iso8859-1")
> +    prop = _libevdev.libevdev_property_from_name(prop)
>      return None if prop < 0 else prop
>
>  class InputEvent(object):
> --
> 2.9.3
>
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