From 65e258488ac502549467e4fc1e5af8c381b3c1ea Mon Sep 17 00:00:00 2001
From: marcobaye <marcobaye@4df02467-bbd4-4a76-a152-e7ce94205b78>
Date: Sat, 26 Dec 2020 23:13:11 +0000
Subject: [PATCH] added file to library (unfinished, do not use!)

git-svn-id: https://svn.code.sf.net/p/acme-crossass/code-0/trunk@311 4df02467-bbd4-4a76-a152-e7ce94205b78
---
 ACME_Lib/6502/rc4.a          | 123 +++++++++++++++++++++++++++++++++++
 ACME_Lib/cbm/c128/zeropage.a |   4 +-
 2 files changed, 125 insertions(+), 2 deletions(-)
 create mode 100644 ACME_Lib/6502/rc4.a

diff --git a/ACME_Lib/6502/rc4.a b/ACME_Lib/6502/rc4.a
new file mode 100644
index 0000000..ed20f3d
--- /dev/null
+++ b/ACME_Lib/6502/rc4.a
@@ -0,0 +1,123 @@
+;ACME 0.97
+
+; this is an implementation of the stream cipher algorithm known as RC4.
+; UNFINISHED - DO NOT USE!
+
+; you need to define these symbols in your code:
+;	rc4_length	a single byte to hold key/chunk lengths
+;	rc4_count	a single byte (iteration counter)
+;	rc4_ii		a single byte to hold state
+;	rc4_jj		a single byte to hold state
+;	rc4_state	a full page of memory (256 bytes)
+;	rc4_in		input buffer
+;	rc4_out		output buffer
+; the size of the buffers limits how much data you can pass to the functions.
+; the two buffer addresses may be identical, in that case the output will
+; overwrite the input.
+; functions you can then call:
+;	rc4_init	initialise state
+;	rc4_key_X	use key (in input buffer, length in X) to change state
+;	rc4_reset	reset ii and jj (call between keying and processing)
+;	rc4_process_X	de/encrypt a chunk of data buffer-to-buffer (length in X)
+
+!zone rc4 {
+	; create shorter names
+	.length	= rc4_length
+	.count	= rc4_count
+	.ii	= rc4_ii
+	.jj	= rc4_jj
+	.state	= rc4_state
+	.inbuf	= rc4_in
+	.outbuf	= rc4_out
+
+; fill state vector with initial values (00..ff) and init both counters
+rc4_init
+		ldx #0
+-			txa
+			sta .state, x
+			inx
+			bne -
+		;FALLTHROUGH
+; reset state counters to zero (actually, only really needed for jj)
+rc4_reset	ldx #0
+		stx .ii
+		stx .jj
+		rts
+
+; use key (in input buffer, length in X) to change permutation in state array
+rc4_key_X
+; X holds .ii (but we count from 0 to 255 and so do not use the real .ii at all)
+; Y holds .jj or .count (.jj is then in A)
+		stx .length
+		ldx #0
+		stx .count
+		; do 256 mixing operations
+		;.ii = 0
+		;ldx #0			;do {
+		ldy .jj
+---						;jj += state[ii] + key[count];
+			tya;lda .jj
+			clc
+			adc .state, x
+			ldy .count
+			clc
+			adc .inbuf, y
+			;sta .jj
+						;if (++count == length)
+						;	count = 0;
+			iny
+			cpy .length
+			bne +
+				ldy #0
++			sty .count
+			tay	; now Y holds .jj
+			lda .state, x		;tmp = state[ii]
+			pha
+			lda .state, y		;state[ii] = state[jj]
+			sta .state, x
+			pla			;state[jj] = tmp
+			sta .state, y
+			inx		;} while (++ii);
+			bne ---
+		sty .jj	; writeback
+		rts
+
+; de/encrypt first X bytes of input buffer to output buffer
+; X==0 means 256!
+rc4_process_X
+		stx .limit
+		ldx #0
+		stx .offset
+-			; ++ii
+			inc .ii
+			; jj += state[ii]
+			ldx .ii
+			lda .jj
+			clc
+			adc .state, x
+			sta .jj
+			tay
+			; tmp = state[ii];
+			; state[ii] = state[jj];
+			; state[jj] = tmp;
+			lda .state, x
+			pha
+			lda .state, y
+			sta .state, x
+			pla
+			sta .state, y
+			; nn = state[ii] + state[jj];
+			clc
+			adc .state, x
+			; buf[aktueller_offset] ^= state[nn]
+			tax
+			lda .state, x
+			ldx #MODIFIED8	: .offset = * - 1
+			eor .inbuf, x
+			sta .outbuf, x
+			; all done?
+			inx
+			cpx #MODIFIED8	: .limit = * - 1
+			bne -
+		rts
+}
diff --git a/ACME_Lib/cbm/c128/zeropage.a b/ACME_Lib/cbm/c128/zeropage.a
index f78a120..02d1e4f 100644
--- a/ACME_Lib/cbm/c128/zeropage.a
+++ b/ACME_Lib/cbm/c128/zeropage.a
@@ -260,8 +260,8 @@ lib_cbm_c128_zeropage_a = 1
 	;z_frekzp	= $fa	; ROM does not use this, but it does get swapped out when screen changes!
 ;}
 	; $fb/$fc/$fd/$fe are unused
-	z_lofbuf	= $ff
-	z_fbuffr	= $0100
+	z_lofbuf	= $ff	; overwritten when outputting line numbers or ti$
+	z_fbuffr	= $0100	; buffer for number strings
 	z_xcnt		= $0110
 	z_dosf1l	= $0111
 	z_dosds1	= $0112