Partially implement nqp::timer.

Missing cancellation-related bits so far.

src/vm/jvm/runtime/org/perl6/nqp/runtime/GlobalContext.java

@@ -5,6 +5,7 @@
 import java.lang.ref.WeakReference;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Timer;
 import java.util.WeakHashMap;
 
 import org.perl6.nqp.sixmodel.CodePairContainerConfigurer;
@@ -122,6 +123,11 @@ public class GlobalContext {
      */
     public ThreadContext mainThread;
 
+    /**
+     * Timer object, used by nqp::timer.
+     */
+    public Timer timer;
+
     /**
      * Active HLL configuration (maps HLL name to the configuration).
      */
@@ -231,6 +237,7 @@ public GlobalContext()
         allThreads = new WeakHashMap< >();
 
         mainThread = getCurrentThreadContext();
+        timer = new Timer(true);
         KnowHOWBootstrapper.bootstrap(mainThread);
         bootInterop = new BootJavaInterop(this);
 

src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java

@@ -31,6 +31,7 @@
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
+import java.util.TimerTask;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.net.InetAddress;
@@ -4388,6 +4389,34 @@ public static SixModelObject queuepoll(SixModelObject queue, ThreadContext tc) {
             throw ExceptionHandling.dieInternal(tc, "queuepoll requires an operand with REPR ConcBlockingQueue");
     }
 
+    /* Asynchronousy operations. */
+
+    private static class AddToQueueTimerTask extends TimerTask {
+        private LinkedBlockingQueue<SixModelObject> queue;
+        private SixModelObject schedulee;
+
+        public AddToQueueTimerTask(LinkedBlockingQueue<SixModelObject> queue, SixModelObject schedulee) {
+            this.queue = queue;
+            this.schedulee = schedulee;
+        }
+
+        public void run() {
+            queue.add(schedulee);
+        }
+    }
+    public static SixModelObject timer(SixModelObject queue, SixModelObject schedulee,
+            long timeout, long repeat, SixModelObject handle_type, ThreadContext tc) {
+        if (!(queue instanceof ConcBlockingQueueInstance))
+            throw ExceptionHandling.dieInternal(tc, "timer's first argument should have REPR ConcBlockingQueue");
+        AddToQueueTimerTask tt = new AddToQueueTimerTask(((ConcBlockingQueueInstance)queue).queue, schedulee);
+        if (repeat > 0)
+            tc.gc.timer.scheduleAtFixedRate(tt, timeout, repeat);
+        else
+            tc.gc.timer.schedule(tt, timeout);
+        /* XXX TODO: cancellation handle. */
+        return null;
+    }
+
     /* Exception related. */
     public static void die_s_c(String msg, ThreadContext tc) {
         // Construct exception object.