Re: how to write a wrapper?
Jules wrote:
>
> most of the Euphoria "heavyweights" (as opposed to the "lightweights", like
> me) devote much of their time and effort into wrapping libraries to extend
> Eu's
> functionality. I understand the basic mechanics of this:
>
> There are actually 3 steps to go through.
>
> 1/ Your wrapper must open a shared file (.dll on Windows, .so on Linux/BSD)
>
> using open_dll() (be sure to include machine.e). This function will return
> some atom I'll call entry_point.
>
> 2/ For each routine you need to wrap, define a constant representing that
> routine using defie_c_func (or _proc):
>
> constant
> the_func=define_c_func(entry_point,func_name,arg_type_list,return_type)
>
> You can also access public variables using define_c_var().
>
> 3/ Then, in any program using the routines, including your own wrapper,
> you use c_func() or c_proc() to call the routine, using the identifiers
> defined in stage 2 as routine ids.
>
> And that should be all, unless you have to fiddle with calling convention.
> If the doc for your dll talks about cdecl, then there is a specific syntax
> to use in define_c_func.
>
> (thanks to CChris for this post). I'd like to have a go at writing a simple
> wrapper but am unsure where to start. I assume I don't need much knowledge of
> C, but surely I need some? and if so, what, particularly? I don't (hopefully)
> need spoon-feeding, but if someone could point me in the right direction, that
> would be great. I'm sure there are many other Eu coders who would like to see
> a tutorial on this subject. I'd be happy to write one myself, once I've
> learned
> the basics.
I am in the same boat, a couple of years ago I bought a Velleman usb interface
board
and it came with a DLL, I managed to hack a wrapper by looking at code writen by
others and used it as a template, I was really pleased when it worked and
suprised that
I had managed to do it, the DLL was well documented and only had a few
functions.
if I were good at writing wrappers I could use dll's written by far better
programmers
than me,(just about everyone) and perhaps give me access to code written for
specialised
tasks.
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