Asynchronous I/O functions on CE
Hi,
I need to port a Windows desktop communication DLL to a PocketPC target. Unfortunately, it seems that CE doesn't support aynchronous call for the I/O function ReadFile, WriteFile and CreateFile but these functions were esential to my DLL.
So, is there really no support for overlapped I/O methods on CE ?
Is there another way to implement non-blocking read/write operations on serial ports or sockets ?
Thx, Negyoshi.
Negyoshi,
There is no support for overlapped I/O. But Windows CE has non-blocking I/O. You can just use a ReadFile that will wait forever for a read and still use WriteFile. The read will not block the write.
I use it with serial ports and work perfectly. My program run on XP and CE and the CE code is much simpler and easier to implement.
I am starting to implement the socket now, but there is no reason to think that it would not work.
RMJR
Oh, I forgot to tell what is needed.
What I do , and I think everybody that need asynchronos i/o on CE, is to have a thread to read and use another to write.
In my case, I have a thread that sits over there on a readfile forever, and I use writefile on my main thread.
RMJR
Thx, i think I'll have to use this method, even though overlapped operations seemed to be much more efficient. The fact is, my DLL implements a communication protocol, so a lot of read/write operations must be called in a short time.
Do you use message queues ? Using WriteFile in your main thread is not blocking it ?
Could you share your code, i would like to have a look at your architecture, since you said it to work perfectly :)
Thx !
Overlapped is more efficient, and should take some space too. That should be the reason why MS did not implement on CE. But that discussion is not the topic.
>
Do you use message queues ? I do not use message queues in that area of the code.
>Using WriteFile in your main thread is not blocking it ? For example, I have a thread that is waiting on a char to arrive on the serial port. So, I have a read waiting for a byte without time-out. This Readfile blocks this thread, but it does not block the serial port. So, if you use a Writefile, this will block your thread. If you need to do something else, you should do it in another thread.
Unfortunetly, I cannot share the code because it is not mine.
You should read the book Programming Windows CE .NET Third editon. From Douglas Boling. Chapter 12. Very nice book.
RMJR
