/**************************************************************************/
/*  semaphore.h                                                           */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
/*                        https://godotengine.org                         */
/**************************************************************************/
/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
/*                                                                        */
/* Permission is hereby granted, free of charge, to any person obtaining  */
/* a copy of this software and associated documentation files (the        */
/* "Software"), to deal in the Software without restriction, including    */
/* without limitation the rights to use, copy, modify, merge, publish,    */
/* distribute, sublicense, and/or sell copies of the Software, and to     */
/* permit persons to whom the Software is furnished to do so, subject to  */
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/* included in all copies or substantial portions of the Software.        */
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/**************************************************************************/

#ifndef SEMAPHORE_H
#define SEMAPHORE_H

#include "core/error_list.h"
#include "core/typedefs.h"

#if !defined(NO_THREADS)

#include <condition_variable>
#include <mutex>

class Semaphore {
private:
	mutable std::mutex mutex_;
	mutable std::condition_variable condition_;
	mutable unsigned long count_ = 0; // Initialized as locked.

public:
	_ALWAYS_INLINE_ void post() const {
		std::lock_guard<decltype(mutex_)> lock(mutex_);
		++count_;
		condition_.notify_one();
	}

	_ALWAYS_INLINE_ void wait() const {
		std::unique_lock<decltype(mutex_)> lock(mutex_);
		while (!count_) { // Handle spurious wake-ups.
			condition_.wait(lock);
		}
		--count_;
	}

	_ALWAYS_INLINE_ bool try_wait() const {
		std::lock_guard<decltype(mutex_)> lock(mutex_);
		if (count_) {
			--count_;
			return true;
		}
		return false;
	}

	_ALWAYS_INLINE_ int get() const {
		std::lock_guard<decltype(mutex_)> lock(mutex_);
		return count_;
	}
};

#else

class Semaphore {
public:
	_ALWAYS_INLINE_ void post() const {}
	_ALWAYS_INLINE_ void wait() const {}
	_ALWAYS_INLINE_ bool try_wait() const { return true; }
	_ALWAYS_INLINE_ int get() const { return 1; }
};

#endif

#endif // SEMAPHORE_H