Now using a std::async and future to do an async popen but I also need the FILE read in read_line to be async, so now I'm at a point where I have to refactor into a better statemachine.

threadtest.cpp

@@ -1,54 +1,37 @@
-#include <condition_variable>
+#include <chrono>
+#include <future>
 #include <iostream>
-#include <mutex>
-#include <string>
 #include <thread>
-
-std::mutex m;
-std::condition_variable cv;
-std::string data;
-bool ready = false;
-bool processed = false;
-
-void worker_thread()
-{
-    // wait until main() sends data
-    std::unique_lock lk(m);
-    cv.wait(lk, []{ return ready; });
-
-    // after the wait, we own the lock
-    std::cout << "Worker thread is processing data\n";
-    data += " after processing";
-
-    // send data back to main()
-    processed = true;
-    std::cout << "Worker thread signals data processing completed\n";
-
-    // manual unlocking is done before notifying, to avoid waking up
-    // the waiting thread only to block again (see notify_one for details)
-    lk.unlock();
-    cv.notify_one();
-}
+using namespace std::chrono_literals;
 
 int main()
 {
-    std::thread worker(worker_thread);
-
-    data = "Example data";
-    // send data to the worker thread
+    std::future<int> future = std::async(std::launch::async, []()
     {
-        std::lock_guard lk(m);
-        ready = true;
-        std::cout << "main() signals data ready for processing\n";
-    }
-    cv.notify_one();
+        std::this_thread::sleep_for(3s);
+        return 8;
+    });
 
-    // wait for the worker
+    std::cout << "waiting...\n";
+    std::future_status status;
+
+    do
     {
-        std::unique_lock lk(m);
-        cv.wait(lk, []{ return processed; });
+        status = future.wait_for(100ms);
+        switch (status)
+        {
+            case std::future_status::deferred:
+                std::cout << "deferred\n";
+                break;
+            case std::future_status::timeout:
+                std::cout << "timeout\n";
+                break;
+            case std::future_status::ready:
+                std::cout << "ready!\n";
+                break;
+        }
     }
-    std::cout << "Back in main(), data = " << data << '\n';
+    while (status != std::future_status::ready);
 
-    worker.join();
+    std::cout << "result is " << future.get() << '\n';
 }