AuroraRuntime/Source/Threading/Primitives/RWLock.cpp

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

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

namespace Aurora::Threading::Primitives
{
    RWLockImpl::RWLockImpl() : read_(*this), write_(*this)
    {

    }

    RWLockImpl::~RWLockImpl()
    {
        mutex_.reset();
        condition_.reset();
    }

    bool RWLockImpl::Init()
    {
        mutex_ = ConditionMutexUnique();
        if (!mutex_)
        {
            return false;
        }

        condition_ = ConditionVariableUnique(mutex_.get());
        if (!condition_)
        {
            return false;
        }
        return true;
    }
        
    bool RWLockImpl::LockRead(AuUInt64 timeout)
    {
        AU_LOCK_GUARD(mutex_);

        while (state_ < 0)
        {
            if (!condition_->WaitForSignal(timeout))
            {
                return false;
            }
        }

        state_++;
        return true;
    }

    bool RWLockImpl::LockWrite(AuUInt64 timeout)
    {
        AU_LOCK_GUARD(mutex_);
    
        while (state_ != 0)
        {
            if (!condition_->WaitForSignal(timeout))
            {
                return false;
            }
        }

        state_ = -1;
        return true;
    }
    
    bool RWLockImpl::TryLockRead()
    {
        AU_LOCK_GUARD(mutex_);
    
        if (state_ == -1)
        {
            return false;
        }

        state_++;
        return true;
    }

    bool RWLockImpl::TryLockWrite()
    {
        AU_LOCK_GUARD(mutex_);
    
        if (state_ > 0)
        {
            return false;
        }

        state_ = -1;
        return true;
    }
    
    void RWLockImpl::UnlockRead()
    {
        AU_LOCK_GUARD(mutex_);

        auto val = --state_;
        
        if ((val == 1) && (elevaterPending_))
        {
            condition_->Signal();
        }

        if (val == 0)
        {
            condition_->Signal();
        }
    }

    void RWLockImpl::UnlockWrite()
    {
        AU_LOCK_GUARD(mutex_);
        state_ = 0;
        condition_->Broadcast();
    }
    
    bool RWLockImpl::UpgradeReadToWrite(AuUInt64 timeout)
    {
        AU_LOCK_GUARD(mutex_);
    
        while (state_ != 1)
        {
            elevaterPending_.store(true);

            if (!condition_->WaitForSignal(timeout))
            {
                return false;
            }
        }
        
        elevaterPending_.store(false);
        
        state_ = -1;
        return true;
    }

    IWaitable *RWLockImpl::AsReadable()
    {
        return &read_;
    }

    IWaitable *RWLockImpl::AsWritable()
    {
        return &write_;
    }
    
    AUKN_SYM RWLock *RWLockNew()
    {
        auto ret = _new RWLockImpl();
        if (!ret)
        {
            return nullptr;
        }

        if (!ret->Init())
        {
            delete ret;
            return nullptr;
        }

        return ret;
    }

    AUKN_SYM void RWLockRelease(RWLock *waitable)
    {
        SafeDelete<RWLockImpl *>(waitable);
    }
}