--- projects/cms/source/util/uk/org/iscream/cms/util/Queue.java	2001/01/02 03:24:51	1.2
+++ projects/cms/source/util/uk/org/iscream/cms/util/Queue.java	2001/02/25 23:23:43	1.12
@@ -13,7 +13,7 @@ import uk.ac.ukc.iscream.util.*;
  * actually contains some elements.
  *
  * @author  $Author: tdb $
- * @version $Id: Queue.java,v 1.2 2001/01/02 03:24:51 tdb Exp $
+ * @version $Id: Queue.java,v 1.12 2001/02/25 23:23:43 tdb Exp $
  */
 public class Queue {
 
@@ -22,7 +22,7 @@ public class Queue {
     /**
      * The current CVS revision of this class
      */
-    public static final String REVISION = "$Revision: 1.2 $";
+    public static final String REVISION = "$Revision: 1.12 $";
     
 //---STATIC METHODS---
 
@@ -62,6 +62,7 @@ public class Queue {
      * This method returns an object from the front of a given queue.
      * It will block until data exists in the queue if required.
      *
+     * @param The queue to retrieve data from.
      * @return The object from the front of the queue.
      * @throws InvalidQueueException if the queue does not exist.
      */
@@ -88,34 +89,86 @@ public class Queue {
         }
         return o;
     }
-       
+    
     /**
-     * This method returns a textual status of the queues. It
-     * is merely for observation, and would most likely be used
-     * by a larger "monitoring" component. Information returned
-     * includes the current size of each queue, and the total
-     * items passed through.
+     * This method releases a get() method that's currently
+     * waiting on an empty queue. This was designed for
+     * shutdown() type methods that may have problems closing
+     * if the thread of control is waiting on a queue.
      *
-     * @return A String message containing status information.
+     * @param queue the queue to release.
      */
-    public String status() {
-        String status = "";
+    public void releaseQueue(int queue) {
+        synchronized(((LinkedList) _lists.get(queue))) {
+                ((LinkedList) _lists.get(queue)).notifyAll();
+        }
+    }
+
+    /**
+     * This method erases the contents of a given queue. This
+     * method should be used with care. It can only empty one
+     * internal queue, not all of them. This must be called
+     * multiple times to empty all queues.
+     *
+     * @param queue the queue to empty.
+     */
+    public void clearQueue(int queue) {
+        synchronized(this) {
+            ((LinkedList) _lists.get(queue)).clear();
+        }
+    }
+    
+    /**
+     * This method returns an XML textual status of the queues.
+     * It is merely for observation, and would most likely be
+     * used by a larger "monitoring" component. Information
+     * returned includes the current size of each queue, and
+     * the total items passed through.
+     *
+     * @return A String message containing status information in XML format
+     */
+    public String xmlStatus() {
+        String status = "<queue ";
         for(int i=0; i < _lists.size(); i++) {
             // check for null entries
             if(_lists.get(i) != null) {
-                status += "Queue number "+i+" contains "+((LinkedList) _lists.get(i)).size()+" elements";
-                status += "\n";
+                status += "queue"+i+"=\""+((LinkedList) _lists.get(i)).size()+"\" ";
             }
             else {
-                status += "Slot number "+i+" is currently empty";
-                status += "\n";
+                status += "queue"+i+"=\"\\<deleted\\>\" ";
             }
         }
-        status += "A total of "+_count+" elements have been added to the queues";
+        status += "total=\""+_count+"\"></queue>";
         return status;
     }
     
     /**
+     * Returns the size of a given queue. A consumer can use
+     * this to see how big their queue is at any given time.
+     * they should use their queue number as the parameter.
+     *
+     * @param queue The queue number to query.
+     * @return the current size of the queue.
+     * @throws InvalidQueueException if the queue does not exist.
+     */
+    public int queueSize(int queue) throws InvalidQueueException {
+        if (queue >= _lists.size() || _lists.get(queue) == null) {
+            throw new InvalidQueueException("Requested queue "+queue+" does not exist");
+        }
+        return ((LinkedList) _lists.get(queue)).size();
+    }
+    
+    /**
+     * Returns the total numer of elements to have passed
+     * through this queue (ie. a counter on the add method).
+     *
+     * @return the element-ometer.
+     */
+    public int elementCount() {
+        return _count;
+    }
+    
+    /**
      * This method assigns a queue to a consumer. The idea behind
      * this is to ensure that only 1 consumer can be associated with
      * a given queue, otherwise the whole "blocking" thing fails
@@ -155,20 +208,73 @@ public class Queue {
     }
     
     /**
+     * Start a monitor on our own Queue. This will log XML
+     * statistics about our Queue to a given Queue (could be
+     * the one being monitored).
+     *
+     * @param interval The long interval, in milliseconds, at which to take samples
+     * @param destQueue The queue to monitor to
+     * @param name A name to identify this Queue with
+     * @return whether we succeeded
+     */
+    public boolean startMonitor(long interval, Queue destQueue, String name) {
+        if(_queueMon == null) {
+            // start a monitor
+            _queueMon = new QueueMonitor(this, destQueue, interval, name);
+            _queueMon.start();
+            return true;
+        }
+        else {
+            // already have a monitor running
+            return false;
+        }
+    }
+    
+    /**
+     * Start a monitor on our own Queue. This will log XML
+     * statistics about our Queue to this Queue.
+     *
+     * @param interval The long interval, in milliseconds, at which to take samples
+     * @param name A name to identify this Queue with
+     * @return whether we succeeded
+     */
+    public boolean startMonitor(long interval, String name) {
+        return startMonitor(interval, this, name);
+    }
+    
+    /**
+     * Stop a monitor on our Queue if we have on running.
+     *
+     * @return whether we succeeded
+     */
+    public boolean stopMonitor() {
+        if(_queueMon != null) {
+            // stop a monitor
+            _queueMon.shutdown();
+            _queueMon = null;
+            return true;
+        }
+        else {
+            // no monitor running
+            return false;
+        }
+    }
+    
+    /**
      * Overrides the {@link java.lang.Object#toString() Object.toString()}
      * method to provide clean logging (every class should have this).
      *
      * This uses the uk.ac.ukc.iscream.util.FormatName class
      * to format the toString()
      *
-     * @return the name of this class and its CVS revision
+     * @return the name of this class and its CVS revision.
      */
-    /*public String toString() {
+    public String toString() {
         return FormatName.getName(
             _name,
             getClass().getName(),
             REVISION);
-    }*/
+    }
 
 //---PRIVATE METHODS---
 
@@ -188,6 +294,11 @@ public class Queue {
     private int _count = 0;
     
     /**
+     * A reference to our QueueMonitor, if we have one.
+     */
+    private QueueMonitor _queueMon = null;
+    
+    /**
      * This is the friendly identifier of the
      * component this class is running in.
      * eg, a Filter may be called "filter1",
@@ -196,13 +307,7 @@ public class Queue {
      * can be placed here.  This name could also
      * be changed to null for utility classes.
      */
-    //private String _name = <!THIS SHOULD CALL A STATIC NAME IN THE COMPONENT CLASS FOR THIS OBJECT!>;
-
-    /**
-     * This holds a reference to the
-     * system logger that is being used.
-     */
-    //private Logger _logger = ReferenceManager.getInstance().getLogger();
+    private String _name = null;
 
 //---STATIC ATTRIBUTES---