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cc65/libsrc/common/toupper.s

22 lines
668 B
ArmAsm

;
; Ullrich von Bassewitz, 02.06.1998
;
; int toupper (int c);
;
.export _toupper
.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
lsr a ; Get bit 0 (lower char) into carry
tya ; Get C back into A
bcc L9 ; Jump if not lower char
clc
adc #<('A'-'a') ; make upper case char
L9: rts ; CC are set