Queue

- Added an `exitReason` and an `alive` (set to `true` on construction)
- Calling `shutdownQueue(ErrorType)` will set the exit reason, will also set the aliveness to `false` and wake up ALL `dequeue()`'s blocking
- `dequeue()` first check in wakeup routine duty cycle is to check if we are alive

source/tristanable/queue/queue.d

@@ -62,6 +62,13 @@ public class Queue
      */
     private Duration wakeInterval;
 
+    /** 
+     * Reason for a `dequeue()`
+     * to have failed
+     */
+    private ErrorType exitReason;
+    private bool alive;
+
     /** 
      * Constructs a new Queue and immediately sets up the notification
      * sub-system for the calling thread (the thread constructing this
@@ -85,6 +92,9 @@ public class Queue
 
         /* Set the slumber interval */
         this.wakeInterval = dur!("msecs")(50); // TODO: Decide on value
+
+        /* Set status to alive */
+        this.alive = true;
     }
 
     /** 
@@ -157,6 +167,25 @@ public class Queue
         }
     }
 
+
+    public void shutdownQueue(ErrorType reason)
+    {
+        // Set running state and reason
+        this.alive = false;
+        this.exitReason = reason;
+
+        // Wakeup sleeping dequeue()
+
+        // Lock the mutex
+        this.mutex.lock();
+
+        // Awake all condition variable sleepers
+        this.signal.notifyAll();
+
+        // Unlock the mutex
+        this.mutex.unlock();
+    }
+
     // TODO: Make a version of this which can time out
 
     /** 
@@ -188,6 +217,13 @@ public class Queue
         /* Block till we dequeue a message successfully */
         while(dequeuedMessage is null)
         {
+            /* Check if this queue is still alive */
+            if(!this.alive)
+            {
+                // Throw an exception to unblock the calling `dequeue()`
+                throw new TristanableException(this.exitReason);
+            }
+
             scope(exit)
             {
                 // Unlock the mutex
@@ -207,7 +243,6 @@ public class Queue
                 throw new TristanableException(ErrorType.DEQUEUE_FAILED);
             }
 
-
             /* Lock the item queue */
             queueLock.lock();