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cc65/libsrc/common/ctypemask.s

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; ctypemask.s
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;
; This file is part of
; cc65 - a freeware C compiler for 6502 based systems
;
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; https://cc65.github.io
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;
; See "LICENSE" file for legal information.
;
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; ctypemask(int c)
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;
; converts a character to test via the is*-functions to the matching ctype-masks
; If c is out of the 8-bit range, the function returns with carry set and accu cleared.
; Return value is in accu and x has to be always clear when returning
; (makes calling code shorter)!
;
; IMPORTANT: stricmp, strlower, strnicmp, strupper and atoi rely that Y is not changed
; while calling this function!
;
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.export ctypemask
.export ctypemaskdirect
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.import __ctype
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.import __ctypeidx
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ctypemask:
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cpx #$00 ; char range ok?
bne SC ; branch if not
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ctypemaskdirect:
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lsr a
tax
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lda __ctypeidx,x
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bcc @lowerNibble
@upperNibble:
lsr a
lsr a
lsr a
lsr a
clc ; remove out of bounds flag
@lowerNibble:
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and #%00001111
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tax
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lda __ctype,x
ldx #$00
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rts
SC: sec
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lda #$00
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tax
rts