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97 lines
1.4 KiB
ArmAsm
97 lines
1.4 KiB
ArmAsm
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; utility
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; Helper routines
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;
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; Created by Quinn Dunki on 8/14/17
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;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; intToString
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;
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; PARAML0 = Number to convert
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; Returns result as pascal string in intToStringResult
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;
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intToString:
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SAVE_AXY
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; Convert value to BCD digits
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; This section courtesy of John Brooks
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sep #9
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tdc
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rol PARAML0
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intToStringLoop:
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sta SCRATCHL
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adc SCRATCHL
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rol intToStringBCD
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asl PARAML0
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bne intToStringLoop
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cld
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xba
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sta intToStringBCD+1
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; Convert digits to characters
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BITS8
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; Skip leading double zeros
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ldx #0
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ldy #1
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intToStringSkipLoop:
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lda intToStringBCD,x
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bne intToStringSkipSingle
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inx
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cpx #3
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bne intToStringSkipLoop
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; Special case for full zero
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sty intToStringResult
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lda #'0'
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sta intToStringResult+1
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bra intToStringDone
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intToStringSkipSingle:
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; Process transition from leading-zero nibble
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lda intToStringBCD,x
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and #$f0
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bne intToStringFullDigitsLoop
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lda intToStringBCD,x
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clc
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adc #'0'
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sta intToStringResult,y
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iny
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inx
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intToStringFullDigitsLoop:
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; Remaining bytes all contain two digits
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lda intToStringBCD,x
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lsr
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lsr
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lsr
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lsr
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clc
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adc #'0'
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sta intToStringResult,y
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iny
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lda intToStringBCD,x
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and #$0f
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clc
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adc #'0'
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sta intToStringResult,y
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iny
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inx
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cpx #3
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bne intToStringFullDigitsLoop
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; Store final length and we're done
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dey
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sty intToStringResult
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intToStringDone:
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BITS16
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RESTORE_AXY
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rts
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intToStringBCD: .byte 0,0,0
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intToStringResult: .byte 0,0,0,0,0,0
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