
<<TiogaLocksPrivateImpl.mesa Edited by Paxton on October 11, 1982 10:27 am>>

DIRECTORY
TiogaLocks,
TiogaLocksPrivate,
TiogaNode,
NodeProps;

TiogaLocksPrivateImpl: CEDAR MONITOR
IMPORTS NodeProps
EXPORTS TiogaLocksPrivate = BEGIN OPEN TiogaLocks, TiogaLocksPrivate;

lastRoot: TiogaNode.RefBranchNode;
lastLock: LockRef;

GetLock: PUBLIC ENTRY PROC [root: TiogaNode.RefBranchNode] RETURNS [lock: LockRef] = {
ENABLE UNWIND => NULL;
IF root = NIL THEN RETURN [NIL];
IF root = lastRoot THEN RETURN [lastLock];
lastRoot _ root;
lock _  lastLock _ NARROW[NodeProps.GetProp[root, $DocumentLock]];
IF lastLock # NIL THEN RETURN;
lock _ lastLock _ NEW[LockRecord];
NodeProps.PutProp[root, $DocumentLock, lock];
};

NodeProps.Register[$DocumentLock, NodeProps.NullRead, NodeProps.NullWrite, NodeProps.NullCopy];
<<Don't copy document lock or big trouble.>>

END..