Introducing Slammer!

[Ivan Drucker <ivan@ivanx.com>]

KansasFest was very exciting for me this year -- in addition to all the fun,
I was pleased to introduce two new tools for Applesoft programmers.
(Attendees received a KansasFest 2010 limited edition 5.25" floppy disk!)
Both tools are available (for free, of course) at
http://www.ivanx.com/appleii/.

SLAMMER!

Slammer, lets you embed machine language routines (or other data) within
100% legal, typeable Applesoft programs. Unlike other methods, Slammer has
no performance, stability, or dependency issues.

It's extremely simple to use; you just CALL 2107, and all subsequent REM
statements are interpreted as though you typed them in at the monitor
prompt. Usually, you'd want to enter bytes, but you can also move memory, do
hex dumps, etc. Slammer keeps interpreting REM statements until it hits a
blank REM, a non-REM statement, or the end of the program. You can call
Slammer as often as you like.

To enable Slammer, all you need is for lines 0-9 to contain REM statements
containing specific ASCII characters, provided on the disk. The disk also
includes SLAMINATOR, which will convert a routine on disk or in memory to
Applesoft REM statements so you don't have to do it yourself; it also
contains documentation.

Slammer also has a bonus feature: for byte entry, you can use **** in place
of an address, and the bytes will be placed between program end and variable
space start. (This moves LOMEM, so it will erase any variables already set.)
Entry can be continued on subsequent lines by omitting the address and
starting them with a colon. With this feature, you don't need to pick any
defined spot in memory for a relocatable routine such as NuInput; it just
automatically gets tucked away in a safe spot.

The inspiration for creating Slammer arose last year when I asked c.s.a2.p
about the best method for providing a machine language routine for an
Applesoft program. After many responses, I found all of the established
methods to be flawed. BLOAD requires one or more accompanying files;
DATA/READ is very slow and difficult to maintain; binary code in program
lines or before the end-of-program marker is brittle (if a user changes a
line, forget it). I found the best self-contained solution to be the S.H.
Lam technique (after which Slammer was named), as it is more versatile and
easily maintained than DATA/READ (plus, it's insanely clever), but it is
still quite slow.

I wanted the Lam technique, but at machine language speed. So I tried to do
something that I figured was probably impossible, and in any event crazy:
write a routine consisting exclusively of bytes in the range $21-$5A, so
that they could appear in REM lines that could be typed on every Apple II.
This meant the only useful memory I could address was $0021-$005A, the only
operands I could use were #$21-#$5A, and the only instructions I had
available were AND BIT BMI BVC CLI EOR JMPa LSR PHA PLP ROL RTI. (I used all
but one of them.) It took nearly a year to complete, and I gave up at least
once along the way, but now you have it, and it works! (If anyone is
curious, I can detail how I managed this on my web page or on c.s.a2.p.)

I hope you enjoy Slammer!


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