AuroraRuntime/Source/Threading/AuWakeOnAddress.hpp

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

    File: AuWakeOnAddress.hpp
    Date: 2023-3-10
    Author: Reece
***/
#pragma once

#include "Primitives/AuWoASemaphore.hpp"

#include "Primitives/AuConditionMutex.Generic.hpp"
#include "Primitives/AuConditionVariable.Generic.hpp"
#include "Primitives/AuSemaphore.Generic.hpp"

#if defined(AURORA_COMPILER_MSVC)
    #define WOAFAST __declspec(safebuffers) auline
    #define WOAFASTPUB AUKN_SYM __declspec(safebuffers) auline
#else
    #define WOAFAST auline
    #define WOAFASTPUB AUKN_SYM
#endif

namespace Aurora::Threading
{
    static const auto kDefaultWaitPerProcess = 128;
    static const auto kMax64 = 0xFFFFFFFFFFFFFFFFull;
    static const auto kPlatformFutexNoForcedAlignedU32 = AuBuild::kIsNTDerived;

    struct WaitState;

    struct WaitBuffer
    {
        char buffer[32];
        AuUInt8 uSize;

        WOAFAST static WaitBuffer From(const void *pBuf, AuUInt8 uSize);

        WOAFAST static bool Compare(const void *pHotAddress, AuUInt8 uSize, WaitState &state);
        WOAFAST static bool Compare(const void *pHotAddress, AuUInt8 uSize, const void *pCompare, AuUInt64 uMask, EWaitMethod eMethod);

        // returns false when valid
        template <EWaitMethod eMethod, bool bFast = false>
        WOAFAST static bool Compare2(const void *pHotAddress, AuUInt8 uSize, const void *pReference, AuUInt64 uMask = 0xFFFFFFFFFFFFFFFF);

        template <EWaitMethod eMethod, bool bFast = false>
        WOAFAST static bool Compare2(const volatile void *pHotAddress, AuUInt8 uSize, const void *pReference, AuUInt64 uMask = 0xFFFFFFFFFFFFFFFF);
    };

    struct WaitState
    {
        WaitBuffer compare;
        //AuOptionalEx<AuUInt64> qwNanoseconds;
        AuOptionalEx<AuUInt64> qwNanosecondsAbs;
        AuUInt64  uDownsizeMask { 0xFFFFFFFFFFFFFFFF };
        AuUInt32 uWordSize {};
        const void *pCompare2 {};
        EWaitMethod eWaitMethod { EWaitMethod::eNotEqual };
    };

    struct WaitEntry
    {
        WaitEntry();
        ~WaitEntry();

        WaitEntry * volatile pNext {};
        WaitEntry * volatile pBefore {};

        // synch
    #if defined(WOA_SEMAPHORE_MODE)
    
        #if !defined(WOA_SEMAPHORE_SEMAPHORE)
            Primitives::Semaphore semaphore;
        #else
            // Recommended for XNU targets:
            WOA_SEMAPHORE_SEMAPHORE semaphore;
        #endif

    #else
        // Recommended (we can better filter spurious wakes for the cost of a barrier on signal):
        // !!! we also prefer to block the containers mutex while we signal each thread individually !!!
        // !!! for the sake of optimizing for windows xp - 7, its far nicer to optimize the entire signaling and wait operations under a container lock, than it is to buffer shared pointers or externally managed memory out of the lock scope !!!
        // !!! also note: container spinlocks =/= WaitEntry::mutex !! 

        #if !defined(WOA_CONDVAR_MUTEX)
            Primitives::ConditionMutexInternal mutex;       // mutex ctor must come before var
            Primitives::ConditionVariableInternal variable; // ...and something all 2007+ micro and monolithic kernels should have; an event or semaphore primitive on which we can form a crude condvar
        #else
            WOA_CONDVAR_MUTEX mutex;
            WOA_CONDVAR_VARIABLE variable;
        #endif

    #endif

        // state
        const void *pAddress {};
        AuUInt8 uSize {};
        const void *pCompareAddress {};
        EWaitMethod eWaitMethod { EWaitMethod::eNotEqual };

        // bookkeeping (parent container)
        volatile AuUInt8 bAlive {}; // wait entry validity. must be rechecked for each spurious or expected wake, if the comparison doesn't break the yield loop.
                                    // if false, and we're still yielding under pCompare == pAddress, we must reschedule with inverse order (as to steal the next signal, as opposed to waiting last)
        void Release();

        template <EWaitMethod eMethod>
        bool SleepOn(WaitState &state);
        bool TrySignalAddress(const void *pAddress);
    };

    struct ProcessListWait
    {
        WaitEntry *pHead {};
        WaitEntry *pTail {};
    };

    struct ProcessWaitNodeContainer
    {
        AuUInt32 uAtomic {};
        ProcessListWait waitList;

        WaitEntry *WaitBufferFrom(const void *pAddress, AuUInt8 uSize, bool bScheduleFirst, const void *pAddressCompare, EWaitMethod eWaitMethod);

        template <typename T>
        bool IterateWake(T callback);

        void RemoveSelf(WaitEntry *pSelf);
        void RemoveEntry(WaitEntry *pSelf, bool bAllUnderLock);

        void Lock();

        void Unlock();
    };

    struct ProcessWaitContainer
    {
        ProcessWaitNodeContainer list[kDefaultWaitPerProcess];

        WaitEntry *WaitBufferFrom(const void *pAddress, AuUInt8 uSize, bool bScheduleFirst, const void *pAddressCompare, EWaitMethod eWaitMethod);

        template <typename T>
        bool IterateWake(const void *pAddress, T callback);

        void RemoveSelf(const void *pAddress, WaitEntry *pSelf);
    };

    inline ProcessWaitContainer gProcessWaitables;
}