Added support for PacketInterceptors. SMACK-104

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@3020 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/PacketWriter.java

@@ -43,6 +43,16 @@ class PacketWriter {
     private boolean listenersDeleted = false;
     private Thread listenerThread;
     private LinkedList sentPackets = new LinkedList();
+    /**
+     * List of PacketInterceptor that will be notified when a new packet is about to be
+     * sent to the server. These interceptors may modify the packet before it is being
+     * actually sent to the server.
+     */
+    private List interceptors = new ArrayList();
+    /**
+     * Flag that indicates if an interceptor was deleted. This is an optimization flag.
+     */
+    private boolean interceptorDeleted = false;
 
     /**
      * Creates a new packet writer with the specified connection.
@@ -87,6 +97,10 @@ class PacketWriter {
      */
     public void sendPacket(Packet packet) {
         if (!done) {
+            // Invoke interceptors for the new packet that is about to be sent. Interceptors
+            // may modify the content of the packet.
+            processInterceptors(packet);
+
             synchronized(queue) {
                 queue.addFirst(packet);
                 queue.notifyAll();
@@ -144,6 +158,40 @@ class PacketWriter {
         }
     }
 
+    /**
+     * Registers a packet interceptor with this writer. The interceptor will be
+     * notified of every packet that this writer is about to send. Interceptors
+     * may modify the packet to be sent. A packet filter determines which packets
+     * will be delivered to the interceptor.
+     *
+     * @param packetInterceptor the packet interceptor to notify of packets about to be sent.
+     * @param packetFilter the packet filter to use.
+     */
+    public void addPacketInterceptor(PacketInterceptor packetInterceptor, PacketFilter packetFilter) {
+        synchronized (interceptors) {
+            interceptors.add(new InterceptorWrapper(packetInterceptor, packetFilter));
+        }
+    }
+
+    /**
+     * Removes a packet interceptor.
+     *
+     * @param packetInterceptor the packet interceptor to remove.
+     */
+    public void removePacketInterceptor(PacketInterceptor packetInterceptor) {
+        synchronized (interceptors) {
+            for (int i=0; i<interceptors.size(); i++) {
+                InterceptorWrapper wrapper = (InterceptorWrapper)interceptors.get(i);
+                if (wrapper != null && wrapper.packetInterceptor.equals(packetInterceptor)) {
+                    interceptors.set(i, null);
+                    // Set the flag to indicate that the interceptor list needs
+                    // to be cleaned up.
+                    interceptorDeleted = true;
+                }
+            }
+        }
+    }
+
     /**
      * Starts the packet writer thread and opens a connection to the server. The
      * packet writer will continue writing packets until {@link #shutdown} or an
@@ -270,6 +318,40 @@ class PacketWriter {
         }
     }
 
+    /**
+     * Process interceptors. Interceptors may modify the packet that is about to be sent.
+     * Since the thread that requested to send the packet will invoke all interceptors, it
+     * is important that interceptors perform their work as soon as possible so that the
+     * thread does not remain blocked for a long period.
+     *
+     * @param packet the packet that is going to be sent to the server
+     */
+    private void processInterceptors(Packet packet) {
+        if (packet != null) {
+            // Clean up null entries in the interceptors list if the flag is set. List
+            // removes are done seperately so that the main notification process doesn't
+            // need to synchronize on the list.
+            synchronized (interceptors) {
+                if (interceptorDeleted) {
+                    for (int i=interceptors.size()-1; i>=0; i--) {
+                        if (interceptors.get(i) == null) {
+                            interceptors.remove(i);
+                        }
+                    }
+                    interceptorDeleted = false;
+                }
+            }
+            // Notify the interceptors of the new packet to be sent
+            int size = interceptors.size();
+            for (int i=0; i<size; i++) {
+                InterceptorWrapper interceptorWrapper = (InterceptorWrapper)interceptors.get(i);
+                if (interceptorWrapper != null) {
+                    interceptorWrapper.notifyListener(packet);
+                }
+            }
+        }
+    }
+
     /**
      * Sends to the server a new stream element. This operation may be requested several times
      * so we need to encapsulate the logic in one place. This message will be sent while doing
@@ -329,6 +411,41 @@ class PacketWriter {
         }
     }
 
+    /**
+     * A wrapper class to associate a packet filter with an interceptor.
+     */
+    private static class InterceptorWrapper {
+
+        private PacketInterceptor packetInterceptor;
+        private PacketFilter packetFilter;
+
+        public InterceptorWrapper(PacketInterceptor packetInterceptor, PacketFilter packetFilter)
+        {
+            this.packetInterceptor = packetInterceptor;
+            this.packetFilter = packetFilter;
+        }
+
+        public boolean equals(Object object) {
+            if (object == null) {
+                return false;
+            }
+            if (object instanceof InterceptorWrapper) {
+                return ((InterceptorWrapper) object).packetInterceptor
+                        .equals(this.packetInterceptor);
+            }
+            else if (object instanceof PacketInterceptor) {
+                return object.equals(this.packetInterceptor);
+            }
+            return false;
+        }
+
+        public void notifyListener(Packet packet) {
+            if (packetFilter == null || packetFilter.accept(packet)) {
+                packetInterceptor.interceptPacket(packet);
+            }
+        }
+    }
+
     /**
      * A TimerTask that keeps connections to the server alive by sending a space
      * character on an interval.

source/org/jivesoftware/smack/XMPPConnection.java

@@ -724,6 +724,32 @@ public class XMPPConnection {
         packetWriter.removePacketListener(packetListener);
     }
 
+    /**
+     * Registers a packet interceptor with this connection. The interceptor will be
+     * invoked every time a packet is about to be sent by this connection. Interceptors
+     * may modify the packet to be sent. A packet filter determines which packets
+     * will be delivered to the interceptor.
+     *
+     * @param packetInterceptor the packet interceptor to notify of packets about to be sent.
+     * @param packetFilter the packet filter to use.
+     */
+    public void addPacketWriterInterceptor(PacketInterceptor packetInterceptor,
+                                           PacketFilter packetFilter) {
+        if (!isConnected()) {
+            throw new IllegalStateException("Not connected to server.");
+        }
+        packetWriter.addPacketInterceptor(packetInterceptor, packetFilter);
+    }
+
+    /**
+     * Removes a packet interceptor.
+     *
+     * @param packetInterceptor the packet interceptor to remove.
+     */
+    public void removePacketWriterInterceptor(PacketInterceptor packetInterceptor) {
+        packetWriter.removePacketInterceptor(packetInterceptor);
+    }
+
     /**
      * Creates a new packet collector for this connection. A packet filter determines
      * which packets will be accumulated by the collector.