From c66765f2a06c8bada24318a3b908a7ff4baf925a Mon Sep 17 00:00:00 2001
From: kohsuke <kohsuke@71c3de6d-444a-0410-be80-ed276b4c234a>
Date: Wed, 6 May 2009 21:16:26 +0000
Subject: [PATCH] Added a new extension point to contribute fragment to
 UDP-based auto discovery.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@17797 71c3de6d-444a-0410-be80-ed276b4c234a
---
 .../java/hudson/UDPBroadcastFragment.java     | 35 +++++++++++++++++++
 .../main/java/hudson/UDPBroadcastThread.java  |  4 +++
 2 files changed, 39 insertions(+)
 create mode 100644 core/src/main/java/hudson/UDPBroadcastFragment.java

diff --git a/core/src/main/java/hudson/UDPBroadcastFragment.java b/core/src/main/java/hudson/UDPBroadcastFragment.java
new file mode 100644
index 0000000000..2161f10201
--- /dev/null
+++ b/core/src/main/java/hudson/UDPBroadcastFragment.java
@@ -0,0 +1,35 @@
+package hudson;
+
+import hudson.model.Hudson;
+
+import java.net.SocketAddress;
+
+/**
+ * Extension point that contributes an XML fragment to the UDP broadcast.
+ *
+ * <p>
+ * Put {@link Extension} on your implementation class to have it auto-discovered.
+ * 
+ * @author Kohsuke Kawaguchi
+ * @since 1.304
+ */
+public abstract class UDPBroadcastFragment implements ExtensionPoint {
+    /**
+     * Called to build up a response XML.
+     *
+     * @param buf
+     *      This is the buffer to write XML to. The implementation of this method
+     *      should write a complete fragment. Because of the packet length restriction
+     *      in UDP (somewhere around 1500 bytes), you cannot send a large amount of information.
+     * @param sender
+     *      The socket address that sent the discovery packet out.
+     */
+    public abstract void buildFragment(StringBuilder buf, SocketAddress sender);
+
+    /**
+     * Returns all the registered {@link UDPBroadcastFragment}s.
+     */
+    public static ExtensionList<UDPBroadcastFragment> all() {
+        return Hudson.getInstance().getExtensionList(UDPBroadcastFragment.class);
+    }
+}
diff --git a/core/src/main/java/hudson/UDPBroadcastThread.java b/core/src/main/java/hudson/UDPBroadcastThread.java
index 9999d7cf4b..c13dea8189 100644
--- a/core/src/main/java/hudson/UDPBroadcastThread.java
+++ b/core/src/main/java/hudson/UDPBroadcastThread.java
@@ -69,6 +69,10 @@ public class UDPBroadcastThread extends Thread {
                     tag(buf,"version",Hudson.VERSION);
                     tag(buf,"url",hudson.getRootUrl());
                     tag(buf,"slave-port",tal==null?null:tal.getPort());
+
+                    for (UDPBroadcastFragment f : UDPBroadcastFragment.all())
+                        f.buildFragment(buf,sender);
+
                     buf.append("</hudson>");
 
                     b.clear();