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29 lines
845 B
ArmAsm
29 lines
845 B
ArmAsm
; tolower.s
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;
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; This file is part of
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; cc65 - a freeware C compiler for 6502 based systems
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;
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; https://cc65.github.io
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;
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; See "LICENSE" file for legal information.
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;
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; int tolower (int c);
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;
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.export _tolower
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.include "ctype.inc"
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.import ctypemaskdirect
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_tolower:
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cpx #$00 ; out of range?
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bne @L2 ; if so, return the argument unchanged
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tay ; save char
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jsr ctypemaskdirect ; get character classification
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and #CT_UPPER ; upper case char?
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beq @L1 ; jump if no
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tya ; restore char
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adc #<('a'-'A') ; make lower case char (ctypemaskdirect ensures carry clear)
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rts
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@L1: tya ; restore char
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@L2: rts
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