Re: [Dev-C++] how to update data constantly?

[Chris M. <lor...@gm...>]

On Dec 5, 2007 1:10 PM, Jessica Chen <jes...@gm...> wrote:
> My whole projects have two thread.
> one thread is reading RS-232 communication port.
> another thread is Win32 GUI to display the data got from RS-232
> communication port.
>
> The design I had is:
> Buttons on Win32 GUI.
> So when the button is clicked, the corresponding data is read from RS232
> thread, and display in the GUI thread.
>
> BUT I want to have a constantly updated display.  That is, there is NO
> button to trigger the data update.
> When the data of RS232 thread is updated, my display of GUI thread need to
> be updated.
> What should I design?
>
> My consideration for the design is:
> add a constant interval timer to trigger the data update.
>  but how to implement it?
> and do you have any other good idea?

A commonly used technique is to have the GUI thread check the reader
thread every X miliseconds.  This requires that you use a mutex to
lock the data while it's being read, otherwise you might incur the
wrath of undefined behavior when reading memory that's currently being
written to.

What if you had a dual-core CPU, and you managed to send a read
request exactly when you sent a write request?  Something tells me
that's not possible because of the mutexes in the lower-level
implementation, but it would be interesting to see which request the
memory controller disregards.


I'm not sure how to implement a mutex in a Win32 thread, however,
pthreads is only a wrapper on top of Win32, so it can be done (I
didn't notice any special code in the pthreads sources when I glossed
over them).

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