[Tutor] Passing nested structures to fcntl.ioctl

[spir]

On Mon, 8 Mar 2010 11:57:35 +0530 (IST)
"Noufal Ibrahim" <noufal at nibrahim.net.in> wrote:

> Hello everyone,
>     I have some code that's calling fcntl.ioctl. I need to pass a nested
> structure as the 3rd argument of the function. Something like this
> 
> typedef struct coordinates{
>   int x;
>   int y;
> } coordinates;
> 
> typedef struct point{
>   int amp;
>   coordinates* coord;
> } point;
> 
>    How would I do this? I need to allocate a point structure and then a
> coordinate structure and link them up together via the coord member of
> point, fill them up with values and pass it to the fcntl.ioctl. The
> actual IOCTL implementation will do the indirection to read out the
> data.
> 
>    I can't use ctypes since I'm working on an embedded system with an ARM
> core that doesn't have ctypes. The struct module doesn't seem to help
> due to the indirection.
> 
>    Any ideas? I'm personally planning to write a small C extension that
> creates the structure based on a specification in memory and then
> passes that to the IOCTL call directly but that looks like some work. I
> was also told to take a look at Cython which basically seems to be an
> easy way of doing what I'm planning. Is there a quicker/easier way?
> 
> Thanks.

If your point is to implement a type (point) in C, for performance certainly, and reuse it from a dynamic language, then I'm not sure python is the best choice (*). Python programmers code in python e basta. C-python bindings are far from beeing simplistic.
http://wiki.cython.org/WrappingCorCpp


Denis


(*) Lua instead is well-known for this kind of stuff; especially on particuliar hardware like ARM. Lua's own implementation is 100% plain ANSI C standard and Lua-C bindings are probably as straightforward as they can be.
http://lua-users.org/wiki/BindingCodeToLua
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