internal FdbFutureSingle([NotNull] FutureHandle handle, [NotNull] Func <FutureHandle, T> selector, CancellationToken ct)
{
Contract.NotNull(handle, nameof(handle));
Contract.NotNull(selector, nameof(selector));
m_handle = handle;
m_resultSelector = selector;
try
{
if (handle.IsInvalid)
{ // it's dead, Jim !
SetFlag(FdbFuture.Flags.COMPLETED);
m_resultSelector = null;
return;
}
if (FdbNative.FutureIsReady(handle))
{ // either got a value or an error
#if DEBUG_FUTURES
Debug.WriteLine("Future<" + typeof(T).Name + "> 0x" + handle.Handle.ToString("x") + " was already ready");
#endif
HandleCompletion(fromCallback: false);
#if DEBUG_FUTURES
Debug.WriteLine("Future<" + typeof(T).Name + "> 0x" + handle.Handle.ToString("x") + " completed inline");
#endif
return;
}
// register for cancellation (if needed)
if (ct.CanBeCanceled)
{
if (ct.IsCancellationRequested)
{ // we have already been cancelled
#if DEBUG_FUTURES
Debug.WriteLine("Future<" + typeof(T).Name + "> 0x" + handle.Handle.ToString("x") + " will complete later");
#endif
// Abort the future and simulate a Canceled task
SetFlag(FdbFuture.Flags.COMPLETED);
// note: we don't need to call fdb_future_cancel because fdb_future_destroy will take care of everything
handle.Dispose();
// also, don't keep a reference on the callback because it won't be needed
m_resultSelector = null;
this.TrySetCanceled();
return;
}
// token still active
RegisterForCancellation(ct);
}
#if DEBUG_FUTURES
Debug.WriteLine("Future<" + typeof(T).Name + "> 0x" + handle.Handle.ToString("x") + " will complete later");
#endif
TrySetFlag(FdbFuture.Flags.READY);
// add this instance to the list of pending futures
var prm = RegisterCallback(this);
// register the callback handler
var err = FdbNative.FutureSetCallback(handle, CallbackHandler, prm);
if (Fdb.Failed(err))
{ // uhoh
#if DEBUG_FUTURES
Debug.WriteLine("Failed to set callback for Future<" + typeof(T).Name + "> 0x" + handle.Handle.ToString("x") + " !!!");
#endif
throw Fdb.MapToException(err);
}
}
catch
{
// this is bad news, since we are in the constructor, we need to clear everything
SetFlag(FdbFuture.Flags.DISPOSED);
UnregisterCancellationRegistration();
UnregisterCallback(this);
// kill the future handle
m_handle.Dispose();
// this is technically not needed, but just to be safe...
this.TrySetCanceled();
throw;
}
GC.KeepAlive(this);
}
protected override void CloseHandles()
{
m_handle?.Dispose();
}