
DIRECTORY
MonitoredQueue USING [AddToSet],
NodeProps USING [GetProp, NullCopy, NullRead, NullWrite, PutProp, Register],
Process USING [GetCurrent],
Rope USING [ROPE],
TEditDocument USING [GetViewerForRoot, SpinAndLock, TEditDocumentData, Unlock],
TEditLocks USING [Access, LockRecord, LockRef],
TEditRefresh USING [dirtyDocs],
TextNode USING [Ref],
ViewerClasses USING [Lock, Viewer],
ViewerLocks USING [LockOrder],
ViewerPrivate USING [AcquireWriteLock, ReleaseWriteLock];

TEditLocksImpl: CEDAR MONITOR LOCKS lock USING lock: LockRef
IMPORTS NodeProps, Process, MonitoredQueue, TEditDocument, TEditRefresh, ViewerLocks, ViewerPrivate
EXPORTS TEditLocks = BEGIN OPEN TEditLocks, TEditDocument;

ROPE: TYPE = Rope.ROPE;
Viewer: TYPE = ViewerClasses.Viewer;

locksBothCount: INT м 0;
dubious: INT м 0;
lockRootViewer: BOOL м TRUE;
lockSplitViewer: BOOL м TRUE;

LockBoth: PUBLIC PROC [doc1, doc2: TextNode.Ref, who: Rope.ROPE, access1, access2: Access м write] RETURNS [lock1, lock2: LockRef] = {
locksBothCount м locksBothCount + 1;
IF (doc1=doc2 AND access1=write) OR (doc1 # doc2 AND LockOrder[doc1, doc2])
THEN {
lock1 м Lock[doc1, who, access1];
lock2 м Lock[doc2, who, access2];
}
ELSE {
lock2 м Lock[doc2, who, access2];
lock1 м Lock[doc1, who, access1];
};
};
Lock: PUBLIC PROC [doc: TextNode.Ref, who: Rope.ROPE, access: Access м write] RETURNS [lock: LockRef] = {
IF doc=NIL THEN ERROR;
DO
v: Viewer м TEditDocument.GetViewerForRoot[doc];
root: Viewer м GetRoot[v];
localViewer: Viewer м NIL;
IF (lock м GetLock[doc])=NIL THEN RETURN;
IF root # NIL THEN {
IF lockRootViewer AND root.link = NIL THEN localViewer м root;
IF lockSplitViewer AND root.link # NIL THEN localViewer м root;
IF localViewer # NIL THEN ViewerPrivate.AcquireWriteLock[localViewer];
};
IF root = GetRoot[v] THEN {
IF TEditDocument.GetViewerForRoot[doc] = v THEN {
LockIt[lock, who, access, doc];
IF TEditDocument.GetViewerForRoot[doc] = v THEN {
NodeProps.PutProp[doc, $LockedViewer, localViewer];
EXIT;
};
NodeProps.PutProp[doc, $LockedViewer, NIL];
UnlockIt[lock, doc];
};
};
IF localViewer # NIL THEN ViewerPrivate.ReleaseWriteLock[localViewer];
ENDLOOP;
};

LockIt: ENTRY PROC [lock: LockRef, who: Rope.ROPE, access: Access, doc: TextNode.Ref] = {
ENABLE UNWIND => NULL;
myProcess: PROCESS;
TRUSTED {myProcess м LOOPHOLE[Process.GetCurrent[]]};
IF access=read
THEN {
IF lock.process # myProcess THEN
WHILE lock.process # NIL DO
WAIT lock.unlocked;
ENDLOOP
}
ELSE {
IF lock.process # myProcess THEN {
IF lock.count > 0 THEN {
lock.waitingForWrite м lock.waitingForWrite+1;
WHILE lock.count > 0 DO
WAIT lock.unlocked;
ENDLOOP;
lock.waitingForWrite м lock.waitingForWrite-1 };
lock.process м myProcess
}};
IF lock.count=0 THEN lock.whoFirst м who ELSE lock.whoLast м who;
lock.count м lock.count+1;
lock.maxCount м MAX[lock.maxCount, lock.count];
};

LockOrder: PUBLIC PROC [doc1, doc2: TextNode.Ref] RETURNS [BOOL] = {
v1: Viewer м IF doc1 = NIL THEN NIL ELSE TEditDocument.GetViewerForRoot[doc1];
v2: Viewer м IF doc2 = NIL THEN NIL ELSE TEditDocument.GetViewerForRoot[doc2];
IF v1 # v2 THEN RETURN [ViewerLocks.LockOrder[v1, v2]];
RETURN [LOOPHOLE[doc1, INT] <= LOOPHOLE[doc2, INT]]
};

Unlock: PUBLIC PROC [doc: TextNode.Ref] = {
lock: LockRef;
IF doc=NIL THEN ERROR;
IF (lock м GetLock[doc])=NIL THEN RETURN;
UnlockIt[lock, doc];
};

UnlockIt: ENTRY PROC [lock: LockRef, doc: TextNode.Ref] = {
ENABLE UNWIND => NULL;
v: Viewer м NARROW[NodeProps.GetProp[doc, $LockedViewer]];
IF lock=NIL THEN RETURN;
IF lock.count <= 0 THEN ERROR;
TRUSTED {IF lock.process # NIL AND lock.process # Process.GetCurrent[] THEN ERROR};
SELECT TRUE FROM
(lock.count м lock.count-1) > 0 => {};
ENDCASE => {
SELECT TRUE FROM
lock.process # NIL => {
viewer: ViewerClasses.Viewer м TEditDocument.GetViewerForRoot[doc];
IF viewer # v THEN dubious м dubious + 1;
IF viewer # NIL THEN {
FOR v: ViewerClasses.Viewer м viewer, v.link UNTIL v = NIL DO
WITH v.data SELECT FROM
tdd: TEditDocument.TEditDocumentData => tdd.dirty м TRUE;
ENDCASE;
IF v.link = viewer THEN EXIT;
ENDLOOP;
MonitoredQueue.AddToSet[doc, TEditRefresh.dirtyDocs];
};
lock.process м NIL;
};
ENDCASE;
NodeProps.PutProp[doc, $LockedViewer, NIL];
lock.whoFirst м lock.whoLast м NIL;
lock.maxCount м 0;
BROADCAST lock.unlocked;
};
IF v # NIL THEN ViewerPrivate.ReleaseWriteLock[v];
};

LockDocAndTdd: PUBLIC PROC [tdd: TEditDocument.TEditDocumentData, who: Rope.ROPE, access: Access м write, interrupt, defer: BOOL м FALSE] RETURNS [lock: LockRef] = {
IF ~TEditDocument.SpinAndLock[tdd, "LockDocAndTdd1", interrupt, defer] THEN
RETURN [NIL];
DO
doc: TextNode.Ref м tdd.text;
TEditDocument.Unlock[tdd]; -- must unlock tdd before try to lock the document.
IF doc=NIL THEN RETURN [NIL];
lock м Lock[doc, who, access];
IF ~TEditDocument.SpinAndLock[tdd, "LockDocAndTdd2", interrupt, defer] THEN {
UnlockIt[lock, doc]; RETURN [NIL] };
IF tdd.text = doc THEN RETURN; -- all went well
UnlockIt[lock, doc]; -- document changed during the time we had tdd unlocked
ENDLOOP;
};

UnlockDocAndTdd: PUBLIC PROC [tdd: TEditDocument.TEditDocumentData] = {
IF tdd.text#NIL THEN Unlock[tdd.text];
TEditDocument.Unlock[tdd];
};

WaitingForWrite: PUBLIC PROC [lock: LockRef] RETURNS [BOOL] = {
RETURN [lock.waitingForWrite > 0];
};

GetRoot: PROC [viewer: Viewer] RETURNS [root: Viewer] = {
root м viewer;
IF root # NIL THEN DO
next: Viewer м root.parent;
IF next = NIL THEN EXIT;
root м next;
ENDLOOP;
};

GetLock: PROC [root: TextNode.Ref] RETURNS [lock: LockRef] ~ INLINE --gfi saver-- {
RETURN [LockedGetLock[privateLock, root]]
};

privateLock: LockRef ~ NEW[LockRecord]; -- used only to lock GetLock
lastRoot: TextNode.Ref м NIL;
lastLock: LockRef м NIL;

LockedGetLock: ENTRY PROC [lock: LockRef, root: TextNode.Ref] RETURNS [LockRef] ~ {
ENABLE UNWIND => NULL;
IF root = NIL THEN RETURN [NIL];
IF root = lastRoot THEN RETURN [lastLock];
lastRoot м root;
lastLock м NARROW[NodeProps.GetProp[root, $DocumentLock]];
IF lastLock # NIL THEN RETURN [lastLock];
lastLock м NEW[LockRecord];
NodeProps.PutProp[root, $DocumentLock, lastLock];
RETURN [lastLock]
};

NodeProps.Register[$DocumentLock, NodeProps.NullRead, NodeProps.NullWrite, NodeProps.NullCopy];

END.
  :  
TEditLocksImpl.mesa
Copyright ╙ 1985, 1987, 1991 by Xerox Corporation.  All rights reserved.
Michael Plass, October 16, 1987 5:00:29 pm PDT
Russ Atkinson (RRA) June 18, 1985 4:01:34 pm PDT
Governs the locking of the root viewer for non-split viewers
Governs the locking of the root viewer for split viewers
Like two calls on Lock, but orders the calls according to LockOrder.
RRA: this is not used, I think!

Be prepared for v = NIL
At this point we have a lock on the correct viewer (if asked to do so)
The viewer is still the right one, so try to lock the document itself
Success!  So note the current association for unlocking.
Rats! The viewer changed while we were trying for the lock, so let's undo everything.
At this point we have a viewer lock, but on the wrong viewer!
wait for write lock to clear
want write access
I don't have a write lock on it already
doc is locked
wait for all locks to clear
had write lock
must lock before read tdd.text
Returns true iff some process is waiting to get a write lock for the document.
Don't copy document lock or big trouble.
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