From: ts <decoux@...>
Date: 2007-04-09T18:39:51+09:00
Subject: Re: rb_yield(), break, and C extensions

>>>>> "N" == Noah Easterly <noah.easterly@gmail.com> writes:

N> So the original definition of func (which allocated memory, used the
N> callback, freed memory, and didn't use ruby.h) won't work, I need to
N> divide that into 3 parts (one to alloc, one that uses the callback,
N> and one to free), and do something like:

 Well, the best is to let ruby manage the memory (with its GC), but if you
 have an original C function that you *can't* modify and you need to give
 it a callback, you can still write *something* like this


moulon% cat a.c 
#include <ruby.h>

void func( int n,  int (*callback)(void) )
{
    int i;

    for (i = 0; i < n; i++) { if (callback() < 0) { goto cleanup; } }
    rb_warn("normal exit");
 cleanup:
    rb_warn("cleanup");
    return;
}

static int
meth_callback(void)
{
    int state;

    rb_protect(rb_yield, 0, &state);
    if (state) {
	rb_thread_local_aset(rb_thread_current(), rb_intern("_test"),
			     INT2NUM(state));
	return -1;
    }
    return 0;
}

static VALUE
yyy_meth(VALUE self, VALUE count)
{
    VALUE res;

    rb_thread_local_aset(rb_thread_current(), rb_intern("_test"), INT2NUM(0));
    func(FIX2INT(count), meth_callback);
    res = rb_thread_local_aref(rb_thread_current(), rb_intern("_test"));
    if (FIXNUM_P(res) && NUM2INT(res) != 0) {
	rb_thread_local_aset(rb_thread_current(), rb_intern("_test"), INT2NUM(0));
	rb_warn("rb_jump_tag");
	rb_jump_tag(NUM2INT(res));
    }
    return Qnil;
}


void Init_a()
{
    VALUE a_cM;

    a_cM = rb_define_class("YYY", rb_cObject);
    rb_define_method(a_cM, "meth", yyy_meth, 1);
}
moulon% 

moulon% cat b.rb
#!/usr/bin/ruby
require 'a'

def m(a)
   puts "before"
   a.meth(6) { return }
   puts "after"
end

puts "before m"
m(YYY.new)
puts "after m"
moulon% 

moulon% ./b.rb
before m
before
./b.rb:6: warning: cleanup
./b.rb:6: warning: rb_jump_tag
after m
moulon% 


Guy Decoux