AuroraRuntime/Source/Threading/Primitives/AuSemaphore.Unix.cpp

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

    File: AuSemaphore.Unix.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuSemaphore.Generic.hpp"
#include "SMPYield.hpp"

#if !defined(_AURUNTIME_GENERIC_SEMAPHORE) && !defined(AURORA_IS_LINUX_DERIVED)
#include <Source/Time/Time.hpp>
        
namespace Aurora::Threading::Primitives
{
    Semaphore::Semaphore(long intialValue) : value_(intialValue)
    {
        pthread_condattr_t attr;
        
        ::pthread_condattr_init(&attr);
        ::pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

        SysAssert(::pthread_cond_init(&this->pthreadCv_, &attr) == 0, "couldn't initialize sema/CV");
    }
    
    Semaphore::~Semaphore()
    {
        ::pthread_cond_destroy(&this->pthreadCv_);
    }

    bool Semaphore::HasOSHandle(AuMach &mach)
    {
        return false;
    }
    
    bool Semaphore::HasLockImplementation()
    {
        return true;
    }
    
    bool Semaphore::TryLock()
    {
        // Assume heavyweight pthread_cond_timedwait yield is followed by an instant hit, for now
        auto old = this->value_;
        return (old != 0 && AuAtomicCompareExchange(&this->value_, old - 1, old) == old);
    }

    bool Semaphore::Lock(AuUInt64 uTimeout)
    {
        return LockNS(AuMSToNS<AuUInt64>(uTimeout));
    }

    bool Semaphore::LockNS(AuUInt64 uTimeout)
    {
        if (DoTryIf([=]()
        {
            auto old = this->value_;
            return (old != 0 && AuAtomicCompareExchange(&this->value_, old - 1, old) == old);
        }))
        {
            return true;
        }

        errno = 0;

        AuUInt64 uStart = AuTime::SteadyClockNS();
        AuUInt64 uEnd = uStart + uTimeout;

        AU_LOCK_GUARD(this->mutex_);
        auto mutex = reinterpret_cast<pthread_mutex_t*>(this->mutex_.GetOSHandle());

        struct timespec tspec;
        if (uTimeout != 0)
        {
            Time::auabsns2ts(&tspec, uEnd);
        }

        while (!this->TryLock())
        {
            if (uTimeout != 0)
            {
                uStart = Time::SteadyClockNS();
                if (uStart >= uEnd)
                {
                    return false;
                }

                int ret {};
                do
                {
                    ret = ::pthread_cond_timedwait(&this->pthreadCv_, mutex, &tspec);
                }
                while (ret == EINTR);
            }
            else
            {
                int ret {};
                bool bStatus {};

                do
                {
                    if ((ret = ::pthread_cond_wait(&this->pthreadCv_, mutex)) == 0)
                    {
                        bStatus = true;
                        break;
                    }
                }
                while (ret == EINTR);

                RUNTIME_ASSERT_SHUTDOWN_SAFE(bStatus, "semaphore wait failed: {}", ret)
            }
        }

        return true;
    }
    
    void Semaphore::Lock()
    {
        auto status = Lock(0);
        SysAssert(status, "Couldn't lock semaphore");
    }
    
    void Semaphore::Unlock(long count)
    {
        AuAtomicAdd<AuInt32>(&this->value_, count);
        if (count == 1)
        {
            auto ret = ::pthread_cond_signal(&this->pthreadCv_);
            SysAssert(ret == 0, "Couldn't wake any semaphore waiter");
        }
        else
        {
            auto ret = ::pthread_cond_broadcast(&this->pthreadCv_);
            SysAssert(ret == 0, "Couldn't wake any semaphore waiters");
        }
    }
    
    void Semaphore::Unlock()
    {
        Unlock(0);
    }
    
    AUKN_SYM ISemaphore *SemaphoreNew(int iInitialCount)
    {
        return _new Semaphore(iInitialCount);
    }

    AUKN_SYM void SemaphoreRelease(ISemaphore *pSemaphore)
    {
        AuSafeDelete<Semaphore *>(pSemaphore);
    }
}
#endif