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22 lines
673 B
ArmAsm
22 lines
673 B
ArmAsm
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; Ullrich von Bassewitz, 02.06.1998
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; int tolower (int c);
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.export _tolower
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.import __ctype
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_tolower:
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cpx #$00 ; Outside valid range?
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bne L9 ; If so, return the argument unchanged
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tay ; Get C into Y
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lda __ctype,y ; Get character classification
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lsr a
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lsr a ; Get bit 1 (upper case char) into carry
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tya ; Get char back into A
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bcc L9 ; Jump if no upper case char
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sbc #<('A'-'a') ; Make lower case char (carry already set)
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L9: rts
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