Checking Win32 file streams for available input

Question

I have a simple tunnel program that needs to simultaneously block on standard input and a socket. I currently have a program that looks like this (error handling and boiler

Answer 1

Use overlapped I/O. Then test the event attached to the I/O operation, instead of the handle.

For CONIN$ specifically, you might also look at the Console Input APIs, such as PeekConsoleInput and GetNumberOfConsoleInputEvents

But I really recommend using OVERLAPPED (background) reads wherever possible and not trying to treat WaitForMultipleObjects like select.

Since the console can't be overlapped in overlapped mode, your simplest options are to wait on the console handle and use ReadConsoleInput (then you have to process control sequences manually), or spawn a dedicated worker thread for synchronous ReadFile. If you choose a worker thread, you may want to then connect a pipe between that worker and the main I/O loop, using overlapped pipe reads.

Another possibility, which I've never tried, would be to wait on the console handle and use PeekConsoleInput to find out whether to call ReadFile or ReadConsoleInput. That way you should be able to get non-blocking along with the cooked terminal processing. OTOH, passing control sequences to ReadConsoleInput might inhibit the buffer-manipulation actions they were supposed to take.

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If the two streams are processed independently, or nearly so, it may make more sense to start a thread for each one. Then you can use a blocking read from standard input.