;
.export _toupper
- .import __ctype, __cdiff
+ .import __ctype
_toupper:
+ cpx #$00 ; Outside valid range?
+ bne L9 ; If so, return the argument unchanged
tay ; Get c into Y
lda __ctype,y ; Get character classification
- and #$01 ; Mask lower char bit
- beq L1 ; Jump if not lower char
+ lsr a ; Get bit 0 (lower char) into carry
tya ; Get C back into A
+ bcc L9 ; Jump if not lower char
clc
- adc __cdiff ; make upper case char
- rts ; CC are set
-
-L1: tya ; Get C back
- rts ; CC are set
+ adc #<('A'-'a') ; make upper case char
+L9: rts ; CC are set