First Commit

externals/openal-soft/common/atomic.h

@@ -0,0 +1,33 @@
+#ifndef AL_ATOMIC_H
+#define AL_ATOMIC_H
+
+#include <atomic>
+
+
+using RefCount = std::atomic<unsigned int>;
+
+inline void InitRef(RefCount &ref, unsigned int value)
+{ ref.store(value, std::memory_order_relaxed); }
+inline unsigned int ReadRef(RefCount &ref)
+{ return ref.load(std::memory_order_acquire); }
+inline unsigned int IncrementRef(RefCount &ref)
+{ return ref.fetch_add(1u, std::memory_order_acq_rel)+1u; }
+inline unsigned int DecrementRef(RefCount &ref)
+{ return ref.fetch_sub(1u, std::memory_order_acq_rel)-1u; }
+
+
+/* WARNING: A livelock is theoretically possible if another thread keeps
+ * changing the head without giving this a chance to actually swap in the new
+ * one (practically impossible with this little code, but...).
+ */
+template<typename T>
+inline void AtomicReplaceHead(std::atomic<T> &head, T newhead)
+{
+    T first_ = head.load(std::memory_order_acquire);
+    do {
+        newhead->next.store(first_, std::memory_order_relaxed);
+    } while(!head.compare_exchange_weak(first_, newhead,
+            std::memory_order_acq_rel, std::memory_order_acquire));
+}
+
+#endif /* AL_ATOMIC_H */