{--
JVM-Bridge -- bridge from FP languages and others to the Java VM
Copyright (C) 2001 Ashley Yakeley <ashley@semantic.org>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
--}

module Foreign.JavaVM.VM.Ref where
{
	import Foreign.JavaVM.VM.Types;
	import Foreign.JavaVM.Raw;
	import Foreign hiding (newForeignPtr);
	import Foreign.Concurrent (newForeignPtr);
	import Data.Nothing;

	newtype VMRef = MkVMRef	(ForeignPtr ());
	
	instance MonadHasNothing IO VMRef where
	{
		getNothing = getNothing >>= (return . MkVMRef);	-- null ref, often used in Java
		getIsNothing (MkVMRef a) = getIsNothing a;
	};

	makeVMRefFromGlobal :: RawGlobalRef -> VM VMRef;
	makeVMRefFromGlobal (MkRawGlobalRef rgref) = do
	{
		vm <- rawGetJavaVM ?jvmenv;
		gref <- newForeignPtr rgref (rawDeleteGlobalRefGC vm (MkRawGlobalRef rgref));
		return (MkVMRef gref);
	};

	-- note that this 'eats' rawLocal
	makeVMRefFromLocal :: RawLocalRef -> VM VMRef;
	makeVMRefFromLocal rawLocal = do
	{
		rawGlobal <- rawConvertToGlobalRef ?jvmenv rawLocal;
		makeVMRefFromGlobal rawGlobal;
	};
	
	withVMRefRawGlobal :: VMRef -> (RawGlobalRef -> IO a) -> IO a;
	withVMRefRawGlobal (MkVMRef fp) foo = withForeignPtr fp (\p -> foo (MkRawGlobalRef p));

	type VMClassRef = VMRef;
}