ParallelLoopStateFlags.cs

Go to the documentation of this file.

namespace System.Threading.Tasks;
 
internal class ParallelLoopStateFlags
{
    private volatile int _loopStateFlags;
 
    internal int LoopStateFlags => _loopStateFlags;
 
    internal bool AtomicLoopStateUpdate(int newState, int illegalStates)
    {
        int oldState = 0;
        return AtomicLoopStateUpdate(newState, illegalStates, ref oldState);
    }
 
    internal bool AtomicLoopStateUpdate(int newState, int illegalStates, ref int oldState)
    {
        SpinWait spinWait = default(SpinWait);
        while (true)
        {
            oldState = _loopStateFlags;
            if ((oldState & illegalStates) != 0)
            {
                return false;
            }
            if (Interlocked.CompareExchange(ref _loopStateFlags, oldState | newState, oldState) == oldState)
            {
                break;
            }
            spinWait.SpinOnce();
        }
        return true;
    }
 
    internal void SetExceptional()
    {
        AtomicLoopStateUpdate(1, 0);
    }
 
    internal void Stop()
    {
        if (!AtomicLoopStateUpdate(4, 2))
        {
            throw new InvalidOperationException(System.SR.ParallelState_Stop_InvalidOperationException_StopAfterBreak);
        }
    }
 
    internal bool Cancel()
    {
        return AtomicLoopStateUpdate(8, 0);
    }
}