c# Named Pipe Asynchronous Peeking
- by KJ Tsanaktsidis
Hey all,
I need to find a way to be notified when a System.IO.Pipe.NamedPipeServerStream opened in asynchronous mode has more data available for reading on it- a WaitHandle would be ideal. I cannot simply use BeginRead() to obtain such a handle because it's possible that i might be signaled by another thread which wants to write to the pipe- so I have to release the lock on the pipe and wait for the write to be complete, and NamedPipeServerStream doesnt have a CancelAsync method. I also tried calling BeginRead(), then calling the win32 function CancelIO on the pipe if the thread gets signaled, but I don't think this is an ideal solution because if CancelIO is called just as data is arriving and being processed, it will be dropped- I still wish to keep this data, but process it at a later time, after the write. I suspect the win32 function PeekNamedPipe might be useful but i'd like to avoid having to continuously poll for new data with it.
In the likley event that the above text is a bit unclear, here's roughly what i'd like to be able to do...
NamedPipeServerStream pipe;
ManualResetEvent WriteFlag;
//initialise pipe
lock (pipe)
{
//I wish this method existed
WaitHandle NewDataHandle = pipe.GetDataAvailableWaithandle();
Waithandle[] BreakConditions = new Waithandle[2];
BreakConditions[0] = NewDataHandle;
BreakConditions[1] = WriteFlag;
int breakcode = WaitHandle.WaitAny(BreakConditions);
switch (breakcode)
{
case 0:
//do a read on the pipe
break;
case 1:
//break so that we release the lock on the pipe
break;
}
}
