From: Einar Karttunen <ekarttun@...>
Date: 2003-07-16T18:37:21+09:00
Subject: Passing ruby objects to other applications

Hello

I am wondering what is the most elegant way of passing ruby objects to a
non-ruby application as e.g. callbacks. As the only references to the
objects may live inside the non-ruby application, some kind of reference
counting is needed in order to make it possible for the Ruby GC to know
when the objects can be deleted.

The first solution that came to my mind was to add a hash table, which
would contain a object -> ref_count mapping. When an object would be
passed to the C side it would be inserted to the hash / it's reference
count would be increased. When the C struct would be destroyed the
reference count would be decremented and if it would have reached 0,
the key would be removed.

This would work because the GC would see the objects and correctly
mark them. This also avoids potential problems with the C program
using things like realloc.

class RefCount < Hash
	def inc(k)
		v = self[k.id]
		if v
			v[0] += 1
		else
			self[k.id] = [1, k] 
		end
	end
	def dec(k)
		v = self[k.id]
		if v
			if v[0] <= 1
				delete k.id
			else
				v[0] -= 1
			end
		end
	end
end

Is this the way to go, or is there a better one?

- Einar Karttunen