readwritespinlock.cpp

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// The DAGFrameScheduler is a Multi-Threaded lock free and wait free scheduling library.
// © Copyright 2010 - 2016 BlackTopp Studios Inc.
/* This file is part of The DAGFrameScheduler.

    The DAGFrameScheduler is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    The DAGFrameScheduler is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with The DAGFrameScheduler.  If not, see <http://www.gnu.org/licenses/>.
*/
/* The original authors have included a copy of the license specified above in the
   'doc' folder. See 'gpl.txt'
*/
/* We welcome the use of the DAGFrameScheduler to anyone, including companies who wish to
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   However there are some practical restrictions, so if your project involves
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   Joseph Toppi - toppij@gmail.com
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*/
#ifndef _readwritespinlock_cpp
#define _readwritespinlock_cpp

#include "atomicoperations.h"
#include "readwritespinlock.h"
#include "crossplatformincludes.h"
#include <limits>
#include <cassert>

/// @file
/// @brief Contains the implementation for the @ref Mezzanine::Threading::Mutex Mutex synchronization object.

namespace Mezzanine
{
    namespace Threading
    {
        ReadWriteSpinLock::ReadWriteSpinLock() : Locked(0)
        {}

        ReadWriteSpinLock::~ReadWriteSpinLock()
        {}


        void ReadWriteSpinLock::LockForRead()
            { while(!TryLockForRead()){} }

        bool ReadWriteSpinLock::TryLockForRead()
        {
            if(CountGaurd.TryLock())
            {
                if(0<=Locked)
                {
                    assert(0<=Locked); // fail because of timing bug in this lock
                    Locked++;
                    CountGaurd.Unlock();
                    return true;
                }else{
                    CountGaurd.Unlock();
                    return false;
                }
            }else{
                return false;
            }
        }

        void ReadWriteSpinLock::UnlockRead()
        {
            CountGaurd.Lock();
            assert(!(0>Locked));  // fail because of writelock
            assert(!(0==Locked)); // fail because not locked
            Locked--;
            CountGaurd.Unlock();
        }

        void ReadWriteSpinLock::LockForWrite()
            { while(!TryLockForWrite()){} }

        bool ReadWriteSpinLock::TryLockForWrite()
        {
            if(CountGaurd.TryLock())
            {
                if(0==Locked)
                {
                    Locked=std::numeric_limits<Int32>::min();
                    CountGaurd.Unlock();
                    return true;
                }else{
                    CountGaurd.Unlock();
                    return false;
                }
            }else{
                return false;
            }
        }

        void ReadWriteSpinLock::UnlockWrite()
        {
            CountGaurd.Lock();
            assert(!(0<Locked));  // fail because of Readlock
            assert(!(0==Locked)); // fail because not locked
            assert(!(std::numeric_limits<Int32>::min()!=Locked)); // failed because cannot unlocked if already unlocked
            Locked=0;
            CountGaurd.Unlock();
        }



    } // \Threading namespace
} // \Mezzanine namespace
#endif