RE: windows "thread" question
> From: Kat <gertie at PELL.NET>
> To: EUforum <EUforum at topica.com>
> Reply-To: EUforum at topica.com
> Subject: windows "thread" question
> Date: 28/09/2001 12:12:41 PM
>
>
> Hi all windows programmers, i have a
> question, and i am not sure i can
> explain it properly, but i'll try...
>
> Lets say i have 3 Eu programs running...
>
> program1 program2, program3
>
> and they each know the others *can* exist,
> and they know how to
> handshake with the other program to verify
> the other program is there. Just
> how they do this would be OS dependant,
> i'll use win95 and either DDE,
> winsock, or win_msgs. Commands they can
> exchange would be, for each
> program:
>
> dothis1a, dothis1b, abort1
> dothis2a, dothis2b, abort2
> dothis3a, dothis3b, abort3
>
> The commands represent functions, which
> return nested sequences. Each
> program knows what is returned in the
> nested sequence. Suppose program1
> is told to insert code before the return()
> line in program2. It cannot change
> the existing returned sequence, but it can
> add another nested sequence to
> that original one, and the calling program
> can ignore that additional sequence
> if it wants to, or not, for whatever
> reason. Program1 would use this additional
> code by doing abort2, and restarting the
> modified program2.
>
> Here is the question:
> How does program3 know what program1 is
> doing to program2 in terms of
> the abort2? Program3 could be calling
> dothis2b while program1 has just
> called abort2. Program3 did a handshake
> with program2 to verify it was
> there, but right after that handshake,
> program1 shut down program2! How do
> i prevent this? Can i make the windows
> program2 ignore the abort2 event
> (from program1) or the dothis2b event
> (from program3)?
>
> What if the OS delivers abort1 from
> program2 while program1 is waiting on a
> result from program2's dothis2a?
>
> How can i be sure of the order of msg
> arrival, and make the order of recieved
> msgs execute in the "right" order? For
> timestamping the msgs, i can't even
> be positive of the time() function in Eu
> if the OS is preemptively timeslicing
> the programs out, can i? What if program1
> gets time(), the OS pages out to
> program3 which does time() *and* then
> sends the msg, i *still* cannot be
> sure of which msg will arrive at program2
> first, can i?,,, because now
> program1 executes and delivers the msg to
> program2's que, right?, before
> the msg from program3 is actually
> delivered to program2. And i just showed
> how the timestamps could be reversed.
>
> Yes, i am considering self-modifying
> programs, and self-cloning programs,
> with Euphoria. Or should i look at another
> language?
If you are sticking with Windows, can I suggest you investigate the
CreateMutex() and related API calls. These enable independant processes to
synchorize with each other to make sure that all data is "current" etc...
------
Derek
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