From: ara.t.howard@...
Date: 2006-06-02T12:14:42+09:00
Subject: Re: How to pass const char *vect[] to C via Ruby/DL?

On Fri, 2 Jun 2006, Andreas Haas wrote:

> but I get a SEGV and it is not complete anyways. Instead of
>
>   ids[DL.sizeof('S')*i] = s.to_ptr
>
> I already tried
>
>  ids[DL.sizeof('S')*i] = s
>
> and other variations I could think of ...
>
> You know: I can imagine there were better means for
> passing string vectors to C, yet the C function interface
> as such is given.
>
> So any help or hint is greatly appreciated!

i'm no dl expert, but:

   harp:~ > cat a.rb
   #
   # generate the lib
   #
   unless test(?e, 'a.so')
     open('a.c','w') do |f|
       f.write <<-'code'
         int setv(const char *ids[]){
           while(*ids){ printf("setv: %s\n", ids[0]); ids++; }
           printf("setv: %s\n", ids[0]);
         }
       code
     end
     system "gcc -shared a.c -o a.so"
   end


   require 'dl/import'

   def setv(ary)
     setv = $lib['setv', 'IP']
     ids = ary.map{|s| s.to_ptr}
     ids << DL::PtrData.new(0)
     r,r1 = setv.call ids.to_ptr
   end

   $lib = DL.dlopen('./a.so')

   setv %w( 1 2 3 )


   harp:~ > ruby a.rb
   setv: 1
   setv: 2
   setv: 3
   setv: (null)


regards.

-a
-- 
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama