new presentation compiler design

1 files changed, 32 insertions, 10 deletions

diff --git a/src/compiler/scala/tools/nsc/util/WorkScheduler.scala b/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
index 7bcd3b7a8e..cd4d805701 100644
--- a/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
+++ b/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
@@ -7,37 +7,59 @@ class WorkScheduler {
   type Action = () => Unit
 
   private var todo = new Queue[Action]
+  private var except: Option[Exception] = None
+  private var working = false
 
-  /** Called from server */
+  /** Called from server: block until todo list is nonempty */
   def waitForMoreWork() = synchronized {
     do { wait() } while (todo.isEmpty)
   }
 
-  /** called from Server */
+  /** called from Server: test whether todo list is nonempty */
   def moreWork(): Boolean = synchronized {
     todo.nonEmpty
   }
 
-  /** Called from server */
+  /** Called from server: get first action in todo list, and pop it off */
   def nextWorkItem(): Option[Action] = synchronized {
-    if (!todo.isEmpty) Some(todo.dequeue()) else None
+    if (!todo.isEmpty) {
+      working = true
+      Some(todo.dequeue())
+    } else None
   }
 
-  /** Called from client */
+  /** Called from server: raise any exception posted by client */
+  def pollException() = synchronized {
+    except match {
+      case Some(exc) => throw exc
+      case None =>
+    }
+  }
+
+  /** Called from server: mark workitem as finished (influences
+   *  meaning of raise)
+   */
+  def doneWorkItem() = synchronized {
+    working = false
+  }
+
+  /** Called from client: have action executed by server */
   def postWorkItem(action: Action) {
     todo enqueue action
     notify()
   }
 
-  /** Called from client */
-  def cancel() = synchronized {
+  /** Called from client: cancel all queued actions */
+  def cancelQueued() = synchronized {
     todo.clear()
   }
 
-  /** Called from client */
+  /** Called from client:
+   *  If work in progress, raise an exception in it next
+   *  time pollException is called.
+   */
   def raise(exc: Exception) = synchronized {
-    todo.clear()
-    todo enqueue (() => throw exc)
+    if (working) except = Some(exc)
   }
 }