Merge branch 'async-physics' into 'master'

Async physics

See merge request OpenMW/openmw!248

components/misc/barrier.hpp

@@ -0,0 +1,51 @@
+#ifndef OPENMW_BARRIER_H
+#define OPENMW_BARRIER_H
+
+#include <condition_variable>
+#include <functional>
+#include <mutex>
+
+namespace Misc
+{
+    /// @brief Synchronize several threads
+    class Barrier
+    {
+        public:
+            using BarrierCallback = std::function<void(void)>;
+            /// @param count number of threads to wait on
+            /// @param func callable to be executed once after all threads have met
+            Barrier(int count, BarrierCallback&& func) : mThreadCount(count), mRendezvousCount(0), mGeneration(0)
+                                                       , mFunc(std::forward<BarrierCallback>(func))
+            {}
+
+            /// @brief stop execution of threads until count distinct threads reach this point
+            void wait()
+            {
+                std::unique_lock<std::mutex> lock(mMutex);
+
+                ++mRendezvousCount;
+                const int currentGeneration = mGeneration;
+                if (mRendezvousCount == mThreadCount)
+                {
+                    ++mGeneration;
+                    mRendezvousCount = 0;
+                    mFunc();
+                    mRendezvous.notify_all();
+                }
+                else
+                {
+                    mRendezvous.wait(lock, [&]() { return mGeneration != currentGeneration; });
+                }
+            }
+
+        private:
+            int mThreadCount;
+            int mRendezvousCount;
+            int mGeneration;
+            mutable std::mutex mMutex;
+            std::condition_variable mRendezvous;
+            BarrierCallback mFunc;
+    };
+}
+
+#endif