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Catching prodos commands

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From	BLuRry <brendan.robert@gmail.com>
Newsgroups	comp.sys.apple2.programmer
Subject	Catching prodos commands
Date	Sat, 4 Feb 2012 23:00:55 -0800 (PST)
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Found a fun thing to do: Re-route calls to $a685 to a custom parser in prodos.  This is the prodos syntax check routine, so if you replace the contents of the keyboard buffer with something else before resuming the command, you can essentially extend the recognized commands almost indefinitely.

Here's my proof of concept stub in the JACE code to do this, though right now I just print out the intercepted command it can be used for much more interesting things later:

new RAMListener(RAMEvent.TYPE.READ, RAMEvent.SCOPE.ADDRESS, RAMEvent.VALUE.ANY) {
                @Override
                protected void doConfig() {setScopeStart(0x0a685);}

                @Override
                protected void doEvent(RAMEvent e) {
                    if (getCpu().getProgramCounter() != getScopeStart()) return;
                    String in = "";
                    for (int i=0x0200; i < 0x0300; i++) {
                        char c = (char) (getMemory().read(i, false) & 0x07f);
                        if (c == 0x0d) break;
                        in += c;
                    }
                    System.err.println("Intercepted command: "+in);
                }

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Thread

Catching prodos commands BLuRry <brendan.robert@gmail.com> - 2012-02-04 23:00 -0800
  Re: Catching prodos commands Antoine Vignau <antoine.vignau@laposte.net> - 2012-02-05 05:51 -0800
    Re: Catching prodos commands BLuRry <brendan.robert@gmail.com> - 2012-02-05 06:42 -0800
      Re: Catching prodos commands "Michael J. Mahon" <mjmahon@aol.com> - 2012-02-08 11:25 -0800
        Re: Catching prodos commands BLuRry <brendan.robert@gmail.com> - 2012-02-08 21:49 -0800

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