1 files changed, 37 insertions, 3 deletions
diff --git a/core/os/semaphore.h b/core/os/semaphore.h
index 9f3c0f549c..f16a15a6db 100644
--- a/core/os/semaphore.h
+++ b/core/os/semaphore.h
@@ -32,19 +32,53 @@
 #define SEMAPHORE_H
 
 #include "core/error_list.h"
+#include "core/typedefs.h"
+
+#include <condition_variable>
+#include <mutex>
 
 class Semaphore {
+private:
+	std::mutex mutex_;
+	std::condition_variable condition_;
+	unsigned long count_ = 0; // Initialized as locked.
+
+public:
+	_ALWAYS_INLINE_ void post() {
+		std::lock_guard<decltype(mutex_)> lock(mutex_);
+		++count_;
+		condition_.notify_one();
+	}
+
+	_ALWAYS_INLINE_ void wait() {
+		std::unique_lock<decltype(mutex_)> lock(mutex_);
+		while (!count_) // Handle spurious wake-ups.
+			condition_.wait(lock);
+		--count_;
+	}
+
+	_ALWAYS_INLINE_ bool try_wait() {
+		std::lock_guard<decltype(mutex_)> lock(mutex_);
+		if (count_) {
+			--count_;
+			return true;
+		}
+		return false;
+	}
+};
+
+class SemaphoreOld {
 protected:
-	static Semaphore *(*create_func)();
+	static SemaphoreOld *(*create_func)();
 
 public:
 	virtual Error wait() = 0; ///< wait until semaphore has positive value, then decrement and pass
 	virtual Error post() = 0; ///< unlock the semaphore, incrementing the    value
 	virtual int get() const = 0; ///< get semaphore value
 
-	static Semaphore *create(); ///< Create a mutex
+	static SemaphoreOld *create(); ///< Create a mutex
 
-	virtual ~Semaphore();
+	virtual ~SemaphoreOld();
 };
 
 #endif