Added multi-threaded progress bar example

include/progress/bar.hpp

@@ -15,7 +15,7 @@ class ProgressBar {
   std::string _remainder{"-"};
   std::string _end{" ]"};
   std::mutex _mutex;
-  bool _completed;
+  std::atomic<bool> _completed;
 
   void _print_progress() {
     std::unique_lock<std::mutex> lock{_mutex};    
@@ -29,6 +29,8 @@ class ProgressBar {
     std::cout << _end << " " << static_cast<int>(_progress) << "%";
     std::cout << " " << _name << "\r";
     std::cout.flush();
+    if (_completed)
+      std::cout << std::endl;    
   }
 
 public:
@@ -64,19 +66,18 @@ public:
   }  
 
   void set_progress(float value) {
+    {
       std::unique_lock<std::mutex> lock{_mutex};
       if (_completed) return;
       _progress = value;
       if (static_cast<int>(_progress) == 100) {
 	_completed = true;
       }
+    }
     _print_progress();
-    if (_completed)
-      std::cout << std::endl;
   }
 
   void tick() {
-    std::unique_lock<std::mutex> lock{_mutex};
     if (_completed) return;
     set_progress(_progress + 1);
   }

test/bar.cpp

@@ -18,10 +18,24 @@ int main() {
   //
   //
 
-  for (size_t i = 0; i < 101; i += 5) {
-    bar.set_progress(i);
-    std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+  std::thread first_job(
+    [&bar]() {
+      for (size_t i = 0; i <= 50; ++i) {
+	bar.tick();
+	std::this_thread::sleep_for(std::chrono::milliseconds(100));
       }
+    });
+
+  std::thread second_job(
+    [&bar]() {
+      for (size_t i = 0; i <= 50; ++i) {
+  	bar.tick();
+  	std::this_thread::sleep_for(std::chrono::milliseconds(100));
+      }
+    });
+
+  first_job.join();
+  second_job.join();
 
   return 0;
 }