LazyAsyncResult.cs

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using System.Threading;
using System.Threading.Tasks;
 
namespace System.Net;
 
internal class LazyAsyncResult : IAsyncResult
{
    private class ThreadContext
    {
        internal int _nestedIOCount;
    }
 
    [ThreadStatic]
    private static ThreadContext t_threadContext;
 
    private readonly object _asyncObject;
 
    private readonly object _asyncState;
 
    private AsyncCallback _asyncCallback;
 
    private object _result;
 
    private int _intCompleted;
 
    private bool _endCalled;
 
    private bool _userEvent;
 
    private object _event;
 
    private static ThreadContext CurrentThreadContext
    {
        get
        {
            ThreadContext threadContext = t_threadContext;
            if (threadContext == null)
            {
                threadContext = (t_threadContext = new ThreadContext());
            }
            return threadContext;
        }
    }
 
    public object AsyncState => _asyncState;
 
    protected AsyncCallback AsyncCallback => _asyncCallback;
 
    public WaitHandle AsyncWaitHandle
    {
        get
        {
            _userEvent = true;
            if (_intCompleted == 0)
            {
                Interlocked.CompareExchange(ref _intCompleted, int.MinValue, 0);
            }
            ManualResetEvent waitHandle = (ManualResetEvent)_event;
            while (waitHandle == null)
            {
                LazilyCreateEvent(out waitHandle);
            }
            return waitHandle;
        }
    }
 
    public bool CompletedSynchronously
    {
        get
        {
            int num = _intCompleted;
            if (num == 0)
            {
                num = Interlocked.CompareExchange(ref _intCompleted, int.MinValue, 0);
            }
            return num > 0;
        }
    }
 
    public bool IsCompleted
    {
        get
        {
            int num = _intCompleted;
            if (num == 0)
            {
                num = Interlocked.CompareExchange(ref _intCompleted, int.MinValue, 0);
            }
            return (num & 0x7FFFFFFF) != 0;
        }
    }
 
    internal bool InternalPeekCompleted => (_intCompleted & 0x7FFFFFFF) != 0;
 
    internal bool EndCalled
    {
        get
        {
            return _endCalled;
        }
        set
        {
            _endCalled = value;
        }
    }
 
    internal LazyAsyncResult(object myObject, object myState, AsyncCallback myCallBack)
    {
        _asyncObject = myObject;
        _asyncState = myState;
        _asyncCallback = myCallBack;
        _result = DBNull.Value;
        if (System.Net.NetEventSource.Log.IsEnabled())
        {
            System.Net.NetEventSource.Info(this, null, ".ctor");
        }
    }
 
    private bool LazilyCreateEvent(out ManualResetEvent waitHandle)
    {
        waitHandle = new ManualResetEvent(initialState: false);
        try
        {
            if (Interlocked.CompareExchange(ref _event, waitHandle, null) == null)
            {
                if (InternalPeekCompleted)
                {
                    waitHandle.Set();
                }
                return true;
            }
            waitHandle.Dispose();
            waitHandle = (ManualResetEvent)_event;
            return false;
        }
        catch
        {
            _event = null;
            waitHandle?.Dispose();
            throw;
        }
    }
 
    protected void ProtectedInvokeCallback(object result, IntPtr userToken)
    {
        if (result == DBNull.Value)
        {
            throw new ArgumentNullException("result");
        }
        if (((uint)_intCompleted & 0x7FFFFFFFu) != 0 || (Interlocked.Increment(ref _intCompleted) & 0x7FFFFFFF) != 1)
        {
            return;
        }
        if (_result == DBNull.Value)
        {
            _result = result;
        }
        ManualResetEvent manualResetEvent = (ManualResetEvent)_event;
        if (manualResetEvent != null)
        {
            try
            {
                manualResetEvent.Set();
            }
            catch (ObjectDisposedException)
            {
            }
        }
        Complete(userToken);
    }
 
    internal void InvokeCallback(object result)
    {
        ProtectedInvokeCallback(result, IntPtr.Zero);
    }
 
    internal void InvokeCallback()
    {
        ProtectedInvokeCallback(null, IntPtr.Zero);
    }
 
    protected virtual void Complete(IntPtr userToken)
    {
        bool flag = false;
        ThreadContext currentThreadContext = CurrentThreadContext;
        try
        {
            currentThreadContext._nestedIOCount++;
            if (_asyncCallback != null)
            {
                if (System.Net.NetEventSource.Log.IsEnabled())
                {
                    System.Net.NetEventSource.Info(this, "Invoking callback", "Complete");
                }
                if (currentThreadContext._nestedIOCount >= 50)
                {
                    if (System.Net.NetEventSource.Log.IsEnabled())
                    {
                        System.Net.NetEventSource.Info(this, "*** OFFLOADED the user callback ****", "Complete");
                    }
                    Task.Factory.StartNew(delegate(object s)
                    {
                        WorkerThreadComplete(s);
                    }, this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
                    flag = true;
                }
                else
                {
                    _asyncCallback(this);
                }
            }
            else if (System.Net.NetEventSource.Log.IsEnabled())
            {
                System.Net.NetEventSource.Info(this, "No callback to invoke", "Complete");
            }
        }
        finally
        {
            currentThreadContext._nestedIOCount--;
            if (!flag)
            {
                Cleanup();
            }
        }
    }
 
    private static void WorkerThreadComplete(object state)
    {
        LazyAsyncResult lazyAsyncResult = (LazyAsyncResult)state;
        try
        {
            lazyAsyncResult._asyncCallback(lazyAsyncResult);
        }
        finally
        {
            lazyAsyncResult.Cleanup();
        }
    }
 
    protected virtual void Cleanup()
    {
    }
 
    internal object InternalWaitForCompletion()
    {
        return WaitForCompletion(snap: true);
    }
 
    private object WaitForCompletion(bool snap)
    {
        ManualResetEvent waitHandle = null;
        bool flag = false;
        if (!(snap ? IsCompleted : InternalPeekCompleted))
        {
            waitHandle = (ManualResetEvent)_event;
            if (waitHandle == null)
            {
                flag = LazilyCreateEvent(out waitHandle);
            }
        }
        if (waitHandle != null)
        {
            try
            {
                if (System.Net.NetEventSource.Log.IsEnabled())
                {
                    System.Net.NetEventSource.Info(this, $"Waiting for completion event {waitHandle}", "WaitForCompletion");
                }
                waitHandle.WaitOne(-1);
            }
            catch (ObjectDisposedException)
            {
            }
            finally
            {
                if (flag && !_userEvent)
                {
                    ManualResetEvent manualResetEvent = (ManualResetEvent)_event;
                    _event = null;
                    if (!_userEvent)
                    {
                        manualResetEvent?.Dispose();
                    }
                }
            }
        }
        SpinWait spinWait = default(SpinWait);
        while (_result == DBNull.Value)
        {
            spinWait.SpinOnce();
        }
        return _result;
    }
}