From: Kouhei Sutou <kou@...>
Date: 2005-01-29T12:29:27+09:00
Subject: Re: SWIG: ruby proc->c function pointer

Hi,

I'm writing bindings to Subversion by SWIG. This has some
callback codes.

In <1106936665.034711.322390@z14g2000cwz.googlegroups.com>
  "SWIG: ruby proc->c function pointer" on Sat, 29 Jan 2005 03:25:52 +0900,
  "gga" <GGarramuno@aol.com> wrote:

> In the process of doing so, I realize I will need to pass proc objects
> from ruby and turn them into function pointers in C, so as to provide a
> callback mechanism.

Here is an example:

--- callback.h
#ifndef CALLBACK_H
#define CALLBACK_H

typedef void (*callback_t) (void *user_data, const char *other_data);

void invoke(callback_t callback, void *user_data, const char *other_data);

#endif
---

--- callback.c
#include "callback.h"

void
invoke(callback_t callback, void *user_data, const char *other_data)
{
  callback(user_data, other_data);
}
---

--- callback.i
%module callback

%{
void
wrap_callback(void *user_data, const char *other_data)
{
  VALUE proc = (VALUE)user_data;
  rb_funcall(proc, rb_intern("call"), 1, rb_str_new2(other_data));
}
%}

%typemap(in) (callback_t callback, void *user_data)
{
  $1 = wrap_callback;
  $2 = (void *)$input;
}

%include callback.h
%{
#include "callback.h"
%}
---

--- Makefile.swig
# -*- Makefile -*-

MODULE    = callback
FEATURE   = $(MODULE)
INTERFACE = $(MODULE).i

RUBY = ruby
SWIG = swig

SWIGOPT = -I/usr/local/include -I/usr/include -ruby -feature $(FEATURE)
WRAPPER   = $(FEATURE)_wrap.c

swigall: $(WRAPPER) Makefile

$(WRAPPER): $(INTERFACE)
	$(SWIG) $(SWIGOPT) -o $@ $(INTERFACE)

Makefile: extconf.rb
	$(RUBY) extconf.rb
	@if [ -f Makefile ] ; then\
		echo "include Makefile.swig" >> Makefile;\
	fi

swigclean:
	@if [ -f Makefile ] ; then\
		make -f Makefile clean;\
	fi
	rm -f Makefile $(WRAPPER)
---

--- extconf.rb
require 'mkmf'
create_makefile("callback")
---

--- to build
% make -f Makefile.swig
% make
---

--- sample usage
% irb -r callback
irb(main):001:0> Callback.invoke(Proc.new{|str| p str}, "abc")
"abc"
=> nil
---

--
kou