AuroraRuntime/Source/Threading/Primitives/Semaphore.NT.cpp

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

    File: Semaphore.Win32.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Semaphore.Generic.hpp"
#include "Semaphore.NT.hpp"

#if !defined(_AURUNTIME_GENERIC_SEMAPHORE)
namespace Aurora::Threading::Primitives
{
    Semaphore::Semaphore(long intialValue)
    {
        value_ = intialValue;
        InitializeSRWLock(&lock_);
        InitializeConditionVariable(&winCond_);
    }
    
    Semaphore::~Semaphore()
    {

    }

    bool Semaphore::HasOSHandle(AuMach &mach)
    {
        return false;
    }
    
    bool Semaphore::HasLockImplementation()
    {
        return true;
    }
    
    bool Semaphore::TryLock()
    {
        auto old = value_;
        return (old != 0 && AuAtomicCompareExchange(&value_, old - 1, old) == old);
    }
    
    bool Semaphore::Lock(AuUInt64 timeout)
    {
        AuUInt64 start = AuTime::CurrentInternalClockMS();
        AuUInt64 end = start + timeout;
        
        AcquireSRWLockShared(&lock_); // we use atomics. using shared is fine, let's not get congested early 
        while (!TryLock())
        {
            AuUInt32 timeoutMs = INFINITE;

            if (timeout != 0)
            {
                start = Time::CurrentClockMS();
                if (start >= end)
                {
                    ReleaseSRWLockShared(&lock_);
                    return false;
                }

                timeoutMs = end - start;
            }

            if (!::SleepConditionVariableSRW(&winCond_, &lock_, AuUInt32(timeoutMs), CONDITION_VARIABLE_LOCKMODE_SHARED))
            {
                ReleaseSRWLockShared(&lock_);
                return false;
            }
        }
        ReleaseSRWLockShared(&lock_);

        return true;
    }
    
    void Semaphore::Lock()
    {
        auto status = Lock(0);
        SysAssert(status, "Couldn't lock semaphore");
    }
    
    void Semaphore::Unlock(long count)
    {
        AcquireSRWLockShared(&lock_);
        AuAtomicAdd<AuInt32>(&value_, count);
        ::WakeAllConditionVariable(&winCond_);
        ReleaseSRWLockShared(&lock_);
    }
    
    void Semaphore::Unlock()
    {
        return Unlock(1);
    }
    
    AUKN_SYM ISemaphore *SemaphoreNew(int initialCount)
    {
        return _new Semaphore(initialCount);
    }

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