Add utilities and sample code to load luaj in custom class loader for strong sandboxing, and use of orphaned threads.

examples/jse/CollectingOrphanedCoroutines.java

@@ -0,0 +1,53 @@
+import org.luaj.vm2.Globals;
+import org.luaj.vm2.LuaThread;
+import org.luaj.vm2.LuaValue;
+import org.luaj.vm2.lib.jse.JsePlatform;
+
+/** Example that continually launches coroutines, and illustrates how to make 
+* sure the orphaned coroutines are cleaned up properly.
+* 
+* Main points:
+* <ul><li>Each coroutine consumes one Java Thread while active or reference anywhere</li>
+* <li>All references to a coroutine must be dropped for the coroutine to be collected</li>
+* <li>Garbage collection must be run regularly to remove weak references to lua threads</li>
+* <li>LuaThread.thread_orphan_check_interval must be short enough to find orphaned references quickly</li>
+* </ul>
+*/
+public class CollectingOrphanedCoroutines {
+
+	// Script that launches coroutines over and over in a loop. 
+	// Garbage collection is done periodically to find and remove orphaned threads.
+	// Coroutines yield out when they are done.
+	static String script = 
+			"i,n = 0,0\n print(i)\n"
+			+ "f = function() n=n+1; coroutine.yield(false) end\n"
+			+ "while true do\n"
+			+ "  local cor = coroutine.wrap(f)\n"
+			+ "  cor()\n"
+			+ "  i = i + 1\n"
+			+ "  if i % 1000 == 0 then\n"
+			+ "    collectgarbage()\n" 
+			+ "    print('threads:', i, 'executions:', n, collectgarbage('count'))\n"
+			+ "  end\n"
+			+ "end\n";
+
+	public static void main(String[] args) throws InterruptedException {
+		// This timer controls how often each Java thread wakes up and checks if
+		// it has been orhaned or not. A large number here will produce a long
+		// delay between orphaning and colleciton, and a small number here will
+		// consumer resources polling for orphaned status if there are many threads.
+		LuaThread.thread_orphan_check_interval = 500;
+
+		// Should work with standard or debug globals.
+		Globals globals = JsePlatform.standardGlobals();
+		// Globals globals = JsePlatform.debugGlobals();
+		
+		// Should work with plain compiler or lua-to-Java compiler.
+		// org.luaj.vm2.luajc.LuaJC.install(globals);;
+
+		// Load and run the script, which launches coroutines over and over forever.
+		LuaValue chunk = globals.load(script, "main");
+		chunk.call();
+	}
+
+}