--- a/SharedQueue.st	Fri May 18 00:29:23 2001 +0200
+++ b/SharedQueue.st	Wed Jun 13 10:17:35 2001 +0200
@@ -128,6 +128,26 @@
     ^ value.
 !
 
+nextIfEmpty:exceptionValue
+    "return the next value in the queue; if it its empty do not wait, but return
+     the value of exceptionValue.
+     When a datum has been removed, signal space-availability to writers"
+
+    |value anyRemoved|
+
+    accessLock critical:[
+        self isEmpty ifTrue:[
+            value := exceptionValue value
+        ] ifFalse:[
+            value := super next.
+            anyRemoved := true.
+        ]
+    ].
+    anyRemoved == true ifTrue:[spaceAvailable signal].
+
+    ^ value.
+!
+
 nextPut:anObject
     "enter anObject into the queue; wait for available space, if
      the queue is full. After the put, signal availablity of a datum
@@ -219,5 +239,5 @@
 !SharedQueue class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic2/SharedQueue.st,v 1.24 2000-12-01 17:15:49 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic2/SharedQueue.st,v 1.25 2001-06-13 08:17:35 cg Exp $'
 ! !