From: Oliver <fwang2@...>
Date: 2007-07-18T03:15:02+09:00
Subject: Re: C library extension question

Thanks for the suggestions, Ryan and George.
I will explore along those lines.

Oliver

On Jul 16, 10:59 pm, George <george.og...@gmail.com> wrote:
> On 7/17/07, Oliver <fwa...@gmail.com> wrote:
>
>
>
> > Now, from a wrapper stand point of view, I was hoping that the user-
> > provided function func_a(), func_b() etc. can be done by ruby as well
> > - it will be very awkward for a user to use partial c, partial ruby
> > for the same library. I don't see why rb_funcall() can help in this
> > case - in a sense, this case calls for a way to map ruby function into
> > C function, for the sake of using the C library call.
>
> Hi Oliver,
>
> Does the library let you specify an argument to pass to these
> callbacks when you register them somehow?  If so, I'd probably define
> the callbacks as Procs (or anything with #call) on the ruby side, and
> in the C side, register the same function, say run_command(VALUE proc)
> for all the commands, passing the Proc as an argument.  run_command()
> would just use rb_funcall to call the proc's #call.
>
> If not, and you do indeed have to register distinct C functions for
> each command, two ideas come to mind:
>
> 1. Have a hard limit on the number of commands, and define C functions
> func1, func2, ... funcN to call the n-th one.
> 2. Use RubyInline to dynamically define each C function, load it as a
> shared library, and add it to your struct (as Ryan just mentioned).
>
> As for the interface on the ruby side, a few options come to mind.
> The more direct translation of the C API:
>
>   command1 = lambda{|*args| ... }
>   command2 = lambda{|*args| ... }
>   ...
>   register(command1, command2, ...)
>
> (You could have #register have symbols denote method calls on Object
> too, but I think procs would feel the most natural.)
>
> Define by blocks on a method:
>
>   add_command{|*args| ... }
>   add_command{|*args| ... }
>   ...
>   register_commands
>
> Register by block:
>
>   register_commands do |c|
>     c.add{|*args| ... }
>     c.add{|*args| ... }
>   end
>
> Hope this gives you some ideas,
> George.