AuroraRuntime/Source/IO/Loop/LSLocalEvent.cpp

/***
    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: LSLocalEvent.cpp
    Date: 2023-10-21
    Author: Reece
***/
#include <RuntimeInternal.hpp>
#include "LSLocalEvent.hpp"
#include <Source/Threading/Primitives/SMTYield.hpp>

namespace Aurora::IO::Loop
{
    LSLocalEvent::LSLocalEvent()
    {

    }

    LSLocalEvent::~LSLocalEvent()
    {

    }

    bool LSLocalEvent::TryInit(bool bTriggered, bool bAtomicRelease, bool bPermitMultipleTriggers)
    {
        if (!LSSemaphore::TryInit(1))
        {
            return false;
        }

        this->bTriggered_ = bTriggered;
        this->bAtomicRelease_ = bAtomicRelease;
        this->bPermitMultipleTriggers_= bPermitMultipleTriggers;
        return true;
    }

    bool LSLocalEvent::OnTrigger(AuUInt handle)
    {
        while (true)
        {
            EventBits bits;
            bits.state = AuAtomicLoad(&this->state_);

            if (bits.bAtomicRelease)
            {
                if (bits.bTriggered)
                {
                    auto next = bits;
                    next.bTriggered = 0;
                    
                    if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) != bits.state)
                    {
                        continue;
                    }

                    return true;
                }
                else
                {
                    (void)LSSemaphore::OnTrigger(0);
                    AuAtomicAdd(&this->uLaterAlwaysOn, 1u);
                    return false;
                }
            }
            else
            {
                if (bits.bTriggered)
                {
                    LSSemaphore::AddOne();
                    return true;
                }
                else
                {
                    (void)LSSemaphore::OnTrigger(0);
                    AuAtomicAdd(&this->uLaterAlwaysOn, 1u);
                    return false;
                }
            }
        }
    }

    bool LSLocalEvent::IsSignaled()
    {
        return this->TryTake();
    }

    bool LSLocalEvent::WaitOn(AuUInt32 timeout)
    {
        return this->TryTakeWaitMS(timeout);
    }

    ELoopSource LSLocalEvent::GetType()
    {
        return ELoopSource::eSourceFastEvent;
    }

    bool LSLocalEvent::Set()
    {
        EventBits bits, next;

        while (true)
        {
            bits.state = AuAtomicLoad(&this->state_);

            if (!bits.bPermitMultipleTriggers)
            {
                if (bits.bTriggered)
                {
                    return false;
                }
            }

            next.state = bits.state;
            next.bTriggered = 1;
            if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state)
            {
                break;
            }
        }

        if (auto count = AuAtomicLoad(&this->uApproxSleepCount))
        {
            if (bits.bAtomicRelease)
            {
                LSSemaphore::AddOne();
            }
            else
            {
                for (AU_ITERATE_N(n, count))
                {
                    LSSemaphore::AddOne();
                }
            }
        }

        return true;
    }

    void LSLocalEvent::OnPresleep()
    {
        AuAtomicAdd(&this->uApproxSleepCount, 1u);

        EventBits bits;
        bits.state = AuAtomicLoad(&this->state_);
        if (!bits.bTriggered)
        {
            return;
        }

        while (true)
        {
            auto uState = AuAtomicLoad(&this->uLaterAlwaysOn);

            if (!uState)
            {
                return;
            }

            if (AuAtomicCompareExchange(&this->uLaterAlwaysOn, uState - 1, uState) == uState)
            {
                break;
            }
        }

        LSSemaphore::AddOne();
    }

    void LSLocalEvent::OnFinishSleep()
    {
        AuAtomicSub(&this->uApproxSleepCount, 1u);
    }

    bool LSLocalEvent::Reset()
    {
        while (true)
        {
            EventBits bits, next;
            bits.state = AuAtomicLoad(&this->state_);

            if (!bits.bTriggered)
            {
                return false;
            }

            next.state = bits.state;
            next.bTriggered = 0;
            if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state)
            {
                break;
            }
        }

        return true;
    }

    bool LSLocalEvent::TryTakeNoSpin()
    {
        EventBits bits;
        bits.state = AuAtomicLoad(&this->state_);
        if (bits.bAtomicRelease)
        {
            if (bits.bTriggered)
            {
                auto next = bits;
                next.bTriggered = 0;
                return AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state;
            }
            else
            {
                return false;
            }
        }
        else
        {
            return bits.bTriggered;
        }
    }

    bool LSLocalEvent::TryTakeSpin()
    {
        return Threading::Primitives::DoTryIfAlderLake([&]
        {
            return this->TryTakeNoSpin();
        }, &this->state_);
    }

    bool LSLocalEvent::IsSignaledNoSpinIfUserland()
    {
        return this->TryTakeNoSpin();
    }

    bool LSLocalEvent::TryTake()
    {
        return this->TryTakeSpin();
    }

    bool LSLocalEvent::TryTakeWaitMS(AuUInt32 timeout)
    {
        auto uEndTime = timeout ?
            AuTime::SteadyClockNS() + AuMSToNS<AuUInt64>(timeout) :
            0;

        if (this->TryTakeSpin())
        {
            return true;
        }

        while (!this->TryTakeNoSpin())
        {
            if (!timeout)
            {
                if (LSSemaphore::WaitOn(0))
                {
                    return true;
                }
            }
            else
            {
                auto uStartTime = Time::SteadyClockNS();
                if (uStartTime >= uEndTime)
                {
                    return false;
                }

                auto uDeltaMs = AuNSToMS<AuInt64>(uEndTime - uStartTime);
                if (uDeltaMs &&
                    LSSemaphore::WaitOn(uDeltaMs))
                {
                    return true;
                }
                else if (!uDeltaMs)
                {
                    if (this->TryTakeSpin())
                    {
                        return true;
                    }
                }
            }
        }

        return true;
    }

    AUKN_SYM AuSPtr<ILSEvent> NewLSEvent(bool bTriggered, bool bAtomicRelease, bool bPermitMultipleTriggers)
    {
        auto pMutex = AuMakeShared<LSLocalEvent>();
        if (!pMutex)
        {
            SysPushErrorGeneric();
            return {};
        }

        if (!pMutex->TryInit(bTriggered, bAtomicRelease, bPermitMultipleTriggers))
        {
            SysPushErrorNested();
            return {};
        }

        return pMutex;
    }
}