godot/core/os/mutex.h

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/*  mutex.h                                                              */
/*************************************************************************/
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#ifndef MUTEX_H
#define MUTEX_H

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

#if !defined(NO_THREADS)

#include <mutex>

template <class StdMutexT>
class MutexImpl {
	mutable StdMutexT mutex;
	friend class MutexLock;

public:
	_ALWAYS_INLINE_ void lock() const {
		mutex.lock();
	}

	_ALWAYS_INLINE_ void unlock() const {
		mutex.unlock();
	}

	_ALWAYS_INLINE_ Error try_lock() const {
		return mutex.try_lock() ? OK : ERR_BUSY;
	}
};

// This is written this way instead of being a template to overcome a limitation of C++ pre-17
// that would require MutexLock to be used like this: MutexLock<Mutex> lock;
class MutexLock {
	union {
		std::recursive_mutex *recursive_mutex;
		std::mutex *mutex;
	};
	bool recursive;

public:
	_ALWAYS_INLINE_ explicit MutexLock(const MutexImpl<std::recursive_mutex> &p_mutex) :
			recursive_mutex(&p_mutex.mutex),
			recursive(true) {
		recursive_mutex->lock();
	}
	_ALWAYS_INLINE_ explicit MutexLock(const MutexImpl<std::mutex> &p_mutex) :
			mutex(&p_mutex.mutex),
			recursive(false) {
		mutex->lock();
	}

	_ALWAYS_INLINE_ ~MutexLock() {
		if (recursive) {
			recursive_mutex->unlock();
		} else {
			mutex->unlock();
		}
	}
};

using Mutex = MutexImpl<std::recursive_mutex>; // Recursive, for general use
using BinaryMutex = MutexImpl<std::mutex>; // Non-recursive, handle with care

extern template class MutexImpl<std::recursive_mutex>;
extern template class MutexImpl<std::mutex>;

#else

class FakeMutex {
	FakeMutex() {}
};

template <class MutexT>
class MutexImpl {
public:
	_ALWAYS_INLINE_ void lock() const {}
	_ALWAYS_INLINE_ void unlock() const {}
	_ALWAYS_INLINE_ Error try_lock() const { return OK; }
};

class MutexLock {
public:
	explicit MutexLock(const MutexImpl<FakeMutex> &p_mutex) {}
};

using Mutex = MutexImpl<FakeMutex>;
using BinaryMutex = MutexImpl<FakeMutex>; // Non-recursive, handle with care

#endif // !NO_THREADS

#endif // MUTEX_H