Track datagrams received out of order and missed datagrams.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@6047 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/util/DatagramSequencer.java

@@ -102,6 +102,7 @@ public class DatagramSequencer
         if (number <= _lastReceived) {
             return null;
         }
+        _missedCount = number - _lastReceived - 1;
         _lastReceived = number;
 
         // read the acknowledge number and process all send records up to that one
@@ -132,6 +133,14 @@ public class DatagramSequencer
         return datagram;
     }
 
+    /**
+     * Returns the number of datagrams missed between the last and the one before it.
+     */
+    public int getMissedCount ()
+    {
+        return _missedCount;
+    }
+
     /**
      * A record of a sent datagram.
      */
@@ -168,6 +177,9 @@ public class DatagramSequencer
     /** The most recent sequence number received. */
     protected int _lastReceived;
 
+    /** The number of datagrams missed between the last and the one before it. */
+    protected int _missedCount;
+
     /** Records of datagrams sent. */
     protected ArrayList<SendRecord> _sendrecs = Lists.newArrayList();
 }