Well, since you don't recomend threads, can you suggest a method to allow the program to send/rescieve the data necessary without locking up? Is it possible to do it with fork? If you have any potential solution, please explain it in detail... I'd like to learn, instead of just have the answer handed to me.
Thanks
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"Weird things happen, get used to it."
Flame ~ Lead Programmer: GMS
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I thought this task would be relatively easy. Basically, you'd fork off a "server" at the beginning of your script
which would have a channel to your script, probably created with
pipe. You'd send URLs to get over a pipe, and the
other end would read them, fetch the URL, and return the
URL over another pipe. (This scheme would basically
be what is done under "Bidirectional Communication with Yourself" in perlipc.)
Unfortunately, Win32::GUI makes watching for the
response difficult. Under Tk, one can watch
for "fileevents" and thus get notified when data is available
on a filehandle (from Tk's main loop.)
Win32::GUI does not have a generic filehandle watching mechanism. One could probably emulate it
using Win32::GUI::Timer and non-blocking I/O:
Basically, you'd periodically poll the pipe going into
your script to see if it has data for you.
So regularly, you'd try to sysread from your
pipe which has been set non-blocking (so your GUI
won't freeze). (update: You'd probably
schedule these read attempts with Win32::GUI::Timer, of course.)
I reccommend sysread, because you're probably going to
need to do your own I/O buffering this case.
You probably want a relatively
short time interval, something to balance use of CPU
with apparent speed.
To enable
non-blocking I/O, you'd use IO::Handle's blocking method with an argument of 0.
To check for data from the socket, you'd read it
(with sysread) and see if you got an error (undef return). If
you got an error and
$! was EAGAIN
(see the Errno module), then
there is no data on the pipe.
If
$! wasn't EAGAIN,
but there was an error, then you'd probably want to
die, because something weird would've happened.
If you don't get an error, you can add that to your cache
of the results (note that you probably won't get all such data at once). (You probably want to have some way
of marking when the end of data is, possibly just prefixing
data you send with the length of the data.)
Personally, I'd prefer a solution where Win32::GUI
was modified to support watching filehandles.
update: I forewarn that this advice
is untested. (Also updated phrasing slightly.)
| [reply]
[d/l]
[select] |
This can make things more interesting... I can loop within another subroutine containing DoEvents() to keep the GUI alive... It could do that while waiting for something to come over the pipe?
I just happened to see the command in the docs just now... I'm not quite sure HOW to do what I just tried to describe though.
Perhaps this can be combined with Tk's monitoring capability?
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"Weird things happen, get used to it."
Flame ~ Lead Programmer: GMS
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Wow... thats a lot to go through, especially since I'm not familiar with many of those commands. *Pulls out Programming Perl R3*
Thanks, this looks promising.
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Flame ~ Lead Programmer: GMS
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Oh, another question... how do I force a forked process to exit when the main program does?
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