ContextAwareResult.cs

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using System.Security.Principal;
using System.Threading;
 
namespace System.Net;
 
internal class ContextAwareResult : LazyAsyncResult
{
    [Flags]
    private enum StateFlags : byte
    {
        None = 0,
        CaptureIdentity = 1,
        CaptureContext = 2,
        ThreadSafeContextCopy = 4,
        PostBlockStarted = 8,
        PostBlockFinished = 0x10
    }
 
    private volatile ExecutionContext _context;
 
    private object _lock;
 
    private StateFlags _flags;
 
    private WindowsIdentity _windowsIdentity;
 
    internal ContextAwareResult(object myObject, object myState, AsyncCallback myCallBack)
        : this(captureIdentity: false, forceCaptureContext: false, myObject, myState, myCallBack)
    {
    }
 
    internal ContextAwareResult(bool captureIdentity, bool forceCaptureContext, object myObject, object myState, AsyncCallback myCallBack)
        : this(captureIdentity, forceCaptureContext, threadSafeContextCopy: false, myObject, myState, myCallBack)
    {
    }
 
    internal ContextAwareResult(bool captureIdentity, bool forceCaptureContext, bool threadSafeContextCopy, object myObject, object myState, AsyncCallback myCallBack)
        : base(myObject, myState, myCallBack)
    {
        if (forceCaptureContext)
        {
            _flags = StateFlags.CaptureContext;
        }
        if (captureIdentity)
        {
            _flags |= StateFlags.CaptureIdentity;
        }
        if (threadSafeContextCopy)
        {
            _flags |= StateFlags.ThreadSafeContextCopy;
        }
    }
 
    internal object StartPostingAsyncOp()
    {
        return StartPostingAsyncOp(lockCapture: true);
    }
 
    internal object StartPostingAsyncOp(bool lockCapture)
    {
        _lock = (lockCapture ? new object() : null);
        _flags |= StateFlags.PostBlockStarted;
        return _lock;
    }
 
    internal bool FinishPostingAsyncOp()
    {
        if ((_flags & (StateFlags.PostBlockStarted | StateFlags.PostBlockFinished)) != StateFlags.PostBlockStarted)
        {
            return false;
        }
        _flags |= StateFlags.PostBlockFinished;
        ExecutionContext cachedContext = null;
        return CaptureOrComplete(ref cachedContext, returnContext: false);
    }
 
    protected override void Cleanup()
    {
        base.Cleanup();
        if (System.Net.NetEventSource.Log.IsEnabled())
        {
            System.Net.NetEventSource.Info(this, null, "Cleanup");
        }
        CleanupInternal();
    }
 
    private bool CaptureOrComplete(ref ExecutionContext cachedContext, bool returnContext)
    {
        bool flag = base.AsyncCallback != null || (_flags & StateFlags.CaptureContext) != 0;
        if ((_flags & StateFlags.CaptureIdentity) != 0 && !base.InternalPeekCompleted && !flag)
        {
            if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, "starting identity capture", "CaptureOrComplete");
            }
            SafeCaptureIdentity();
        }
        if (flag && !base.InternalPeekCompleted)
        {
            if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, "starting capture", "CaptureOrComplete");
            }
            if (cachedContext == null)
            {
                cachedContext = ExecutionContext.Capture();
            }
            if (cachedContext != null)
            {
                if (!returnContext)
                {
                    _context = cachedContext;
                    cachedContext = null;
                }
                else
                {
                    _context = cachedContext;
                }
            }
            if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, $"_context:{_context}", "CaptureOrComplete");
            }
        }
        else
        {
            if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, "Skipping capture", "CaptureOrComplete");
            }
            cachedContext = null;
        }
        if (base.CompletedSynchronously)
        {
            if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, "Completing synchronously", "CaptureOrComplete");
            }
            base.Complete(IntPtr.Zero);
            return true;
        }
        return false;
    }
 
    protected override void Complete(IntPtr userToken)
    {
        if (System.Net.NetEventSource.Log.IsEnabled())
        {
            System.Net.NetEventSource.Info(this, $"_context(set):{_context != null} userToken:{userToken}", "Complete");
        }
        if ((_flags & StateFlags.PostBlockStarted) == 0)
        {
            base.Complete(userToken);
        }
        else
        {
            if (base.CompletedSynchronously)
            {
                return;
            }
            ExecutionContext context = _context;
            if (userToken != IntPtr.Zero || context == null)
            {
                base.Complete(userToken);
                return;
            }
            ExecutionContext.Run(context, delegate(object s)
            {
                ((ContextAwareResult)s).CompleteCallback();
            }, this);
        }
    }
 
    private void CompleteCallback()
    {
        if (System.Net.NetEventSource.Log.IsEnabled())
        {
            System.Net.NetEventSource.Info(this, "Context set, calling callback.", "CompleteCallback");
        }
        base.Complete(IntPtr.Zero);
    }
 
    private void SafeCaptureIdentity()
    {
        _windowsIdentity = WindowsIdentity.GetCurrent();
    }
 
    private void CleanupInternal()
    {
        if (_windowsIdentity != null)
        {
            _windowsIdentity.Dispose();
            _windowsIdentity = null;
        }
    }
}