add original source

source/listing_8.6.cpp

@@ -0,0 +1,50 @@
+std::thread task_thread;
+std::atomic<bool> task_cancelled(false);
+
+void gui_thread()
+{
+    while(true)
+    {
+        event_data event=get_event();
+        if(event.type==quit)
+            break;
+        process(event);
+    }
+}
+
+void task()
+{
+    while(!task_complete() && !task_cancelled)
+    {
+        do_next_operation();
+    }
+    if(task_cancelled)
+    {
+        perform_cleanup();
+    }
+    else
+    {
+        post_gui_event(task_complete);
+    }
+}
+
+void process(event_data const& event)
+{
+    switch(event.type)
+    {
+    case start_task:
+        task_cancelled=false;
+        task_thread=std::thread(task);
+        break;
+    case stop_task:
+        task_cancelled=true;
+        task_thread.join();
+        break;
+    case task_complete:
+        task_thread.join();
+        display_results();
+        break;
+    default:
+        //...
+    }
+}