barrier.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
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*/
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*/
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#ifndef _barrier_cpp
#define _barrier_cpp

#include "barrier.h"

#include <cassert>

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

namespace Mezzanine
{
    namespace Threading
    {
        Barrier::Barrier (const Int32& SynchThreadCount)
                        : ThreadGoal (SynchThreadCount),
                          IsBlocking(1),
                          ThreadCurrent (0)
        {}

        bool Barrier::Wait()
        {
            if(0==AtomicAdd(&IsBlocking,0)) // is a barrier breaking right now
                { return false; }

            if (AtomicAdd(&ThreadCurrent,1) >= ThreadGoal-1) //
            {
                while(0!=AtomicCompareAndSwap32(&ThreadGoal,ThreadGoal,0));
                AtomicAdd(&IsBlocking,-1);
                assert(IsBlocking==0);
                return true;
            }
            else
            {
                while(AtomicAdd(&IsBlocking,0)); // intentionally spinning

                if(1==AtomicAdd(&ThreadCurrent,-1))
                    { AtomicAdd(&IsBlocking,1); }

                return false;
            }
        }

        void Barrier::SetThreadSyncCount(Int32 NewCount)
            { while(ThreadGoal!=AtomicCompareAndSwap32(&ThreadGoal,ThreadGoal,NewCount)); }

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