private long _result; // Using long since this needs to be used in Interlocked APIs
// Using RunContinuationsAsynchronously for compat reasons (old API used Task.Factory.StartNew for continuations)
internal FileStreamCompletionSource(IFileStreamCompletionSourceStrategy strategy, PreAllocatedOverlapped?preallocatedOverlapped,
int numBufferedBytes, byte[]?bytes) : base(TaskCreationOptions.RunContinuationsAsynchronously)
{
_numBufferedBytes = numBufferedBytes;
_strategy = strategy;
_result = NoResult;
// The _preallocatedOverlapped is null if the internal buffer was never created, so we check for
// a non-null bytes before using the stream's _preallocatedOverlapped
_overlapped = bytes != null && strategy.CompareExchangeCurrentOverlappedOwner(this, null) == null ?
strategy.FileHandle.ThreadPoolBinding !.AllocateNativeOverlapped(preallocatedOverlapped !) : // allocated when buffer was created, and buffer is non-null
strategy.FileHandle.ThreadPoolBinding !.AllocateNativeOverlapped(s_ioCallback, this, bytes);
Debug.Assert(_overlapped != null, "AllocateNativeOverlapped returned null");
}
internal virtual void ReleaseNativeResource()
{
// Ensure that cancellation has been completed and cleaned up.
_cancellationRegistration.Dispose();
// Free the overlapped.
// NOTE: The cancellation must *NOT* be running at this point, or it may observe freed memory
// (this is why we disposed the registration above).
if (_overlapped != null)
{
_strategy.FileHandle.ThreadPoolBinding !.FreeNativeOverlapped(_overlapped);
_overlapped = null;
}
// Ensure we're no longer set as the current completion source (we may not have been to begin with).
// Only one operation at a time is eligible to use the preallocated overlapped,
_strategy.CompareExchangeCurrentOverlappedOwner(null, this);
}