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- Subject: Re: Pushing a UserData pointer?
- From: Mark Hamburg <mhamburg@...>
- Date: Mon, 16 May 2005 14:20:33 -0700
This is more or less the way I ended up doing object pushes from
Objective-C. The one enhancement I came up with was to use a light userdata
instead of a pointer to get to the table.
// kObjectsTableKey just needs to be a unique pointer
Still not exactly cheap.
on 5/16/05 11:53 AM, Chris Marrin at email@example.com wrote:
> But such a thing does not exist. I can understand why. You don't want to
> go pushing some random pointer and then expect Lua to try to access its
> metatable and then crash! To solve this, I created a global table called
> __objects, with weak values. The key to this table is the this pointer,
> as a lightuserdata, and the value is the userdata. Making the values
> weak will allow these objects to get collected even if they are in this
> table. So now I can simply do this:
> lua_pushstring(L, "__objects");
> lua_gettable(L, LUA_GLOBALSINDEX);
> lua_pushlightuserdata(L, this);
> and voila' I have the userdata on the stack. The problem is this is very
> slow, requiring two table accesses and stack fiddling every time.
> Am I missing something in the public API, or is there really no more
> efficient way to move between C++ and Lua?