add original source

source/listing_4.11.cpp

@@ -0,0 +1,18 @@
+#include <condition_variable>
+#include <mutex>
+#include <chrono>
+std::condition_variable cv;
+bool done;
+std::mutex m;
+bool wait_loop()
+{
+    auto const timeout= std::chrono::steady_clock::now()+
+        std::chrono::milliseconds(500);
+    std::unique_lock<std::mutex> lk(m);
+    while(!done)
+    {
+        if(cv.wait_until(lk,timeout)==std::cv_status::timeout)
+            break;
+    }
+    return done;
+}