rpcs3/Utilities/cond.h

#pragma once

#include "types.h"
#include "Atomic.h"

// Lightweight condition variable
class cond_variable
{
	// Internal waiter counter
	atomic_t<u32> m_value{0};

protected:
	// Internal waiting function
	bool imp_wait(u32 _old, u64 _timeout) noexcept;

	// Try to notify up to _count threads
	void imp_wake(u32 _count) noexcept;

public:
	constexpr cond_variable() = default;

	// Intrusive wait algorithm for lockable objects
	template <typename T>
	explicit_bool_t wait(T& object, u64 usec_timeout = -1)
	{
		const u32 _old = m_value.fetch_add(1); // Increment waiter counter
		object.unlock();
		const bool res = imp_wait(_old, usec_timeout);
		object.lock();
		return res;
	}

	// Wake one thread
	void notify_one() noexcept
	{
		if (m_value)
		{
			imp_wake(1);
		}
	}

	// Wake all threads
	void notify_all() noexcept
	{
		if (m_value)
		{
			imp_wake(-1);
		}
	}

	static constexpr u64 max_timeout = u64{UINT32_MAX} / 1000 * 1000000;
};