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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 prod=
os.  This is the prodos syntax check routine, so if you replace the content=
s of the keyboard buffer with something else before resuming the command, y=
ou can essentially extend the recognized commands almost indefinitely.

Here's my proof of concept stub in the JACE code to do this, though right n=
ow I just print out the intercepted command it can be used for much more in=
teresting 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() !=3D getScopeStart()) =
return;
                    String in =3D "";
                    for (int i=3D0x0200; i < 0x0300; i++) {
                        char c =3D (char) (getMemory().read(i, false) & 0x0=
7f);
                        if (c =3D=3D 0x0d) break;
                        in +=3D c;
                    }
                    System.err.println("Intercepted command: "+in);
                }