Hi,
Is it possible to define a packed C structure in python and pass it to the c
module, or should the wrapper do that ?
Regards,
Philippe
8  1964 
Philippe Martin wrote: Is it possible to define a packed C structure in python and pass it to the c
module, or should the wrapper do that ?
You can create a packed structure using string concatenation, and with
the help of the struct module. However, this gives you a string object
in the end, which you still need to pass into your C library.
It is better to fill the struct in the wrapper.
Regards,
Martin
Thanks,
It's a pretty big structure: painfull to pass each item as a param.
Regards,
Philippe
"Martin v. Löwis" wrote: Philippe Martin wrote: Is it possible to define a packed C structure in python and pass it to
the c module, or should the wrapper do that ?
You can create a packed structure using string concatenation, and with
the help of the struct module. However, this gives you a string object
in the end, which you still need to pass into your C library.
It is better to fill the struct in the wrapper.
Regards,
Martin
Philippe Martin wrote: It's a pretty big structure: painfull to pass each item as a param.
So how else would you like to pass them? Define the API you want,
and then just implement it. It still shouldn't require to define
the layout in Python.
Regards,
Martin
Well,
The call actually is an IOCtl: depending on the control code, the structure
has a different format.
Although the number of control codes/structures is finite, it would make the
wrapper function fairly large.
You seem to think that building the structure from python would be a
mistake: why is that ?
PS: the wrapper also has to work under multiple OSs
Regards,
Philippe
"Martin v. Löwis" wrote: Philippe Martin wrote: It's a pretty big structure: painfull to pass each item as a param.
So how else would you like to pass them? Define the API you want,
and then just implement it. It still shouldn't require to define
the layout in Python.
Regards,
Martin
On Apr 14, 2006, at 9:44 AM, Philippe Martin wrote: Thanks,
It's a pretty big structure: painfull to pass each item as a param.
Regards,
Philippe
Maybe this can do something for you? http://pyconstruct.sourceforge.net/
Jay P.
Philippe Martin wrote: The call actually is an IOCtl: depending on the control code, the structure
has a different format.
Ah. In that case, I recommend to use the ioctl module; you won't need a
C wrapper, then.
Although the number of control codes/structures is finite, it would make the
wrapper function fairly large.
*Some* code to handle this will be very large, regardless of how you
write it.
You seem to think that building the structure from python would be a
mistake: why is that ?
It's very error-prone. You have to match the C structure layout of the
compiler precisely, and you even have to get the alignment right,
something that can't be done reliably in Python.
PS: the wrapper also has to work under multiple OSs
That makes it worse: now you not only have to match the C compiler's
expectation on a single processor, but on different ones.
Perhaps you should be using ctypes.
Regards,
Martin
I misslead you: it is a smart card-style ioctl ...
Philippe
"Martin v. Löwis" wrote: Philippe Martin wrote: The call actually is an IOCtl: depending on the control code, the
structure has a different format.
Ah. In that case, I recommend to use the ioctl module; you won't need a
C wrapper, then.
Although the number of control codes/structures is finite, it would make
the wrapper function fairly large.
*Some* code to handle this will be very large, regardless of how you
write it.
You seem to think that building the structure from python would be a
mistake: why is that ?
It's very error-prone. You have to match the C structure layout of the
compiler precisely, and you even have to get the alignment right,
something that can't be done reliably in Python.
PS: the wrapper also has to work under multiple OSs
That makes it worse: now you not only have to match the C compiler's
expectation on a single processor, but on different ones.
Perhaps you should be using ctypes.
Regards,
Martin
I'll take a look,
thanks.
Jay Parlar wrote:
On Apr 14, 2006, at 9:44 AM, Philippe Martin wrote:
Thanks,
It's a pretty big structure: painfull to pass each item as a param.
Regards,
Philippe
Maybe this can do something for you?
http://pyconstruct.sourceforge.net/
Jay P.
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