Coroutine implementation based on Java Threads.

src/addon/java/lua/addon/luacompat/CoroutinesLib.java

@@ -10,14 +10,21 @@ import lua.value.LThread;
 
 public class CoroutinesLib extends LFunction {
 
+	private static final String[] NAMES = {
+		"loadlib",
+		"create",
+		"resume",
+		"running",
+		"status",
+		"wrap",
+		"yield",
+		"wrapped"
+	};
+	
 	public static void install() {
 		LTable lib = new LTable(0,6);
-		lib.put("create", new CoroutinesLib(1));
-		lib.put("resume", new CoroutinesLib(2));
-		lib.put("running", new CoroutinesLib(3));
-		lib.put("status", new CoroutinesLib(4));
-		lib.put("wrap", new CoroutinesLib(5));
-		lib.put("yield", new CoroutinesLib(6));
+		for ( int i=1; i<=6; i++ )
+			lib.put(NAMES[i], new CoroutinesLib(i));
 		GlobalState.getGlobalsTable().put("coroutine",lib);
 	}
 	
@@ -34,6 +41,10 @@ public class CoroutinesLib extends LFunction {
 		this.thread = null;
 	}
 	
+	public String toJavaString() {
+		return "coroutine."+NAMES[id];
+	}
+	
 	private CoroutinesLib( int id, LThread thread ) {
 		this.id = id;
 		this.thread = thread;

src/main/java/lua/value/LThread.java

@@ -5,7 +5,10 @@ import lua.StackState;
 import lua.VM;
 import lua.io.Closure;
 
-public class LThread extends LValue {
+/** 
+ * Implementation of lua coroutines using Java Threads
+ */
+public class LThread extends LValue implements Runnable {
 
 	private static final int STATUS_SUSPENDED     = 0;
 	private static final int STATUS_RUNNING       = 1;
@@ -20,6 +23,7 @@ public class LThread extends LValue {
 	private int status = STATUS_SUSPENDED;
 	
 	private StackState threadVm;
+	private Thread thread;
 	
 	private static LThread running;
 	
@@ -46,6 +50,34 @@ public class LThread extends LValue {
 		return running;
 	}
 	
+	public void run() {
+		synchronized ( this ) {
+			try {
+				threadVm.execute();
+			} finally {
+				status = STATUS_DEAD;
+				this.notify();
+			}
+		}
+	}
+	
+	public boolean yield() {
+		synchronized ( this ) {
+			if ( status != STATUS_RUNNING )
+				throw new RuntimeException(this+" not running");
+			status = STATUS_SUSPENDED;
+			this.notify();
+			try {
+				this.wait();
+				status = STATUS_RUNNING;
+			} catch ( InterruptedException e ) {
+				status = STATUS_DEAD;
+				throw new RuntimeException(this+" "+e);
+			}
+			return false;
+		}
+	}
+	
 	/** This needs to leave any values returned by yield in the coroutine 
 	 * on the calling vm stack
 	 * @param vm
@@ -53,6 +85,7 @@ public class LThread extends LValue {
 	 */
 	public void resumeFrom(VM vm, int nargs) {
 
+		synchronized ( this ) {
  			if ( status == STATUS_DEAD ) {
 				vm.settop(0);
 				vm.pushboolean(false);
@@ -60,27 +93,29 @@ public class LThread extends LValue {
 				return;
 			}
 			
-		// set prior thread to normal status while t
+			// set prior thread to normal status while we are running
 			LThread prior = running;
 			try {
 				// set our status to running
-			running = this;
 				if ( prior != null  )
 					prior.status = STATUS_NORMAL;
+				running = this;
 				status = STATUS_RUNNING;
 				
 				// copy args in
-			if ( threadVm.cc < 0 ) {
+				if ( thread == null ) {
 					vm.xmove(threadVm, nargs);
 					threadVm.prepStackCall();
+					thread = new Thread(this);
+					thread.start();
 				} else {
 					threadVm.settop(0);
 					vm.xmove(threadVm, nargs);
 				}
 	
 				// run this vm until it yields
-			while ( threadVm.cc >= 0 && status == STATUS_RUNNING )
-				threadVm.exec();
+				this.notify();
+				this.wait();
 				
 				// copy return values from yielding stack state
 				vm.settop(0);
@@ -97,24 +132,14 @@ public class LThread extends LValue {
 				vm.settop(0);
 				vm.pushboolean(false);
 				vm.pushstring("thread: "+t);
+				this.notify();
 				
 			} finally {
-			// previous thread is now running
+				// previous thread is now running again
 				running = prior;
-			if ( running != null  )
-				running.status = STATUS_RUNNING;
-
-			// check if thread is actually dead
-			if ( threadVm.cc < 0 )
-				status = STATUS_DEAD;
-		
+			}
 		}
 		
 	}
 
-	public boolean yield() {
-		if ( status == STATUS_RUNNING )
-			status = STATUS_SUSPENDED;
-		return true;
-	}
 }

src/test/res/coroutines.lua

@@ -46,7 +46,7 @@ exercise();
 
 co = coroutine.create(function (a,b)
 	print("co-body", a, b)
-	local statis,r = pcall( foo, a+1 )
+	local status,r = pcall( foo, a+1 )
 	print("co-body", status,r)
 	local r, s = coroutine.yield(a+b, a-b)
 	print("co-body", r, s)
@@ -55,6 +55,7 @@ end)
 
 exercise();
 
+
 -- wrap test 
 local g = coroutine.wrap(function (a,b)
 	print("co-body", a, b)