AuroraRuntime/Source/Threading/Primitives/AuConditionVariable.NT.hpp

/***
    Copyright (C) 2021-2024 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: ConditionVariable.Win32.hpp
    Date: 2021-6-12
    Author: Reece
***/
#pragma once

#include "AuConditionVariable.Generic.hpp"
#if !defined(_AURUNTIME_GENERICCV)
#include "AuConditionMutex.NT.hpp"

namespace Aurora::Threading::Primitives
{
    struct ConditionVariableNT final
    {
        ConditionVariableNT();
        
        bool WaitForSignalNsEx(Win32ConditionMutex *pMutex, AuUInt64 timeout, bool bSpin = true);
        void Signal();
        void Broadcast();
        void BroadcastN(AuUInt32 nBroadcast);
        
        auline void AddWaiter();
        auline bool CheckOut();
        auline bool CheckOutNoSpin();

    private:
    #if defined(AURORA_FORCE_SRW_LOCKS)
        CONDITION_VARIABLE winCond_;
    #else
        AuAUInt32 wlist {};
        AuAUInt32 signalCount {};
    #endif
    };

    using ConditionVariableInternal = ConditionVariableNT;

    struct ConditionVariableImpl final : IConditionVariable
    {
        inline ConditionVariableImpl(const AuSPtr<IConditionMutex> &mutex) : 
            mutex(mutex)
        {
        }

        auline AuSPtr<IConditionMutex> GetMutex() override
        {
            return mutex;
        }

        auline bool WaitForSignal(AuUInt32 timeout) override
        {
            return cond.WaitForSignalNsEx(&std::static_pointer_cast<ConditionMutexImpl>(this->mutex)->mutex, AuMSToNS<AuUInt64>(timeout));
        }

        auline bool WaitForSignalNS(AuUInt64 qwTimeout) override
        {
            return cond.WaitForSignalNsEx(&std::static_pointer_cast<ConditionMutexImpl>(this->mutex)->mutex, qwTimeout);
        }

        inline bool WaitForSignalNsEx(const std::shared_ptr<Win32ConditionMutex> &pMutex, AuUInt64 timeout)
        {
            return cond.WaitForSignalNsEx(pMutex.get(), timeout);
        }

        auline void Signal() override
        {
            cond.Signal();
        }

        auline void Broadcast() override
        {
            cond.Broadcast();
        }

        ConditionVariableNT cond;
        std::shared_ptr<IConditionMutex> mutex;
    };

    static const auto kSizeOfDummyCondVar = sizeof(ConditionVariableInternal);

    static const auto kBoolRequiredLateSet = true;

    static const auto kShiftCountByBits = 8u;
    // ...otherwise
    // assume undefined behaviour past:
    //  * bit zero is used for atomic bit test and yield loops 
    //    ( keyed events are an optimization mechanism for Windows XPs spinloop i had accidentally recreated in xenus. )
    //    ( originally, nt yielding sucked with the most barebones spinlock being dumb a hypervisor-unaware, smt-aware, spinner. )
    //    ( keyed events would then go in these spinners to serve as an early futex as early back as the year 2001-3 (?). )
    //  * bit one might be used under some niche versions of windows
    //    (hearsay paranoia)
    // i actually have no reason to believe windows ever implemented lock-awareness into the kernel
    // i think it might be fine to skip the whole bit zero thing, but still, im going to say keep the min=2
    // worst case scenario, we end up using these bits (we did).

}
#endif