[Nut-upsdev] upsclient high level API and Java wrapping

Charles Lepple clepple at gmail.com
Fri Jul 8 12:29:17 UTC 2011

On Jul 7, 2011, at 10:06 AM, <EmilienKia at Eaton.com> wrote:

> This mail is a reply to mails from Charles Lepple and Petr Kubánek  
> dated from july 7 with the same topic.
>> From: Charles Lepple
>> "One thing with SWIG (and other binding systems) is that it is not
>> easy to handle errors gracefully. I can't count how many times I got
>> segmentation violation errors calling well-tested C code from Python
>> via SWIG.
>> I tried using ctypes, which doesn't require any recompilation of the
>> target library, but it has similar problems.
> I am surprised. I follow wxWidgets open source project for a while,  
> their python wrapping is done with SWIG and they do not have so many  
> problems with that.
> Note I have not used SWIG for python (nor python itself)  
> personnally, so perhaps I missed something.

The difference here is that wxWidgets is a much more complex library  
than upsclient.

>> The big advantage to SWIG is supposed to be that you can generate
>> bindings to many languages once you set things up, but in reality,
>> each language has its nuances for passing things by
>> reference, and so
>> each set of bindings has slightly different semantics.
> I never say that SWIG will generate all bindings magically without  
> any specific code.
> The experience I had with SWIG was with Java and Lua on separated  
> projects. In theses cases, once some specific code was set (mostly  
> typemapping), adding methods and objects was not so problematic.

Granted, there will be language-specific code. What I meant by "each  
set of bindings has slightly different semantics" is that the way to  
call a "get variables" method in Python might look different than in  
Java if Python has to return things in the return arguments, and Java  
simply allows the programmer to pass a reference to a list that gets  
filled in.

So in addition to differences "under the hood", you would end up with  
API differences. It's not a show-stopper, but it means additional  
documentation to point out how to use each language binding.

Charles Lepple

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