Squeezed out a few bytes

git-svn-id: svn://svn.cc65.org/cc65/trunk@3427 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/libsrc/apple2/revers.s b/libsrc/apple2/revers.s
index 2e79e6c8fc7bb8660e51b7130e3a3ca5b980ad7f..982925b9e078f92a522f3a743acd638027c3c58c 100644 (file)
--- a/libsrc/apple2/revers.s
+++ b/libsrc/apple2/revers.s
@@ -1,5 +1,5 @@
 ;
-; Kevin Ruland
+; Ullrich von Bassewitz, 2005-03-28
 ;
 ; unsigned char __fastcall__ revers (unsigned char onoff)
 ;
@@ -9,15 +9,14 @@
        .include        "apple2.inc"
 
 _revers:
-       ldy     INVFLG          ; Stash old value
-       and     #$FF            ; Test for any bit
-       beq     normal          ; Nothing set
-       lda     #~$3F           ; Not Inverse
-normal:        eor     #$FF            ; Xor Normal
-       sta     INVFLG
-       tya                     ; What was the old value?
-       eor     #$FF            ; Normal = $FF, Inverse = $3F
-       beq     :+
-       lda     #$01
+       tax                     ; Test onoff
+       beq     normal          ; If zero, "normal" must be set
+       ldx     #$3F+1          ; Set "inverse"
+normal: dex                    ; $00->$FF, $40->$3F
+       lda     #$00            ; Preload return code for "normal"
+       ldy     INVFLG          ; Load current flag value
+       stx     INVFLG          ; Save new flag value
+       bmi     :+              ; Jump if current value is $FF (normal)
+       lda     #$01            ; Return "inverse"
 :      ldx     #$00
        rts