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.importzp ptr3, ptr4, sreg
.import popeax, popax
.export _ulong_to_big, _big_to_ulong
.include "atari.inc"
;IFP = $d9aa
fptemp = $a0 ; for now
.rodata
BIG_64K:
.byte $42, $06, $55, $36, $00, $00
;BIG_ULONG_MAX:
;.byte $44, $42, $94, $96, $72, $95
.code
; TODO: replace these *_to_* with OS calls
fr0_to_fptemp:
ldx #5
@l:
lda FR0,x
sta fptemp,x
dex
bpl @l
rts
fr0_to_fr1:
ldx #5
@l:
lda FR0,x
sta FR1,x
dex
bpl @l
rts
fptemp_to_fr0:
ldx #5
@l:
lda fptemp,x
sta FR0,x
dex
bpl @l
rts
fptemp_to_fr1:
ldx #5
@l:
lda fptemp,x
sta FR1,x
dex
bpl @l
rts
fr0_to_ptr3:
ldy #5
@l:
lda FR0,y
sta (ptr3),y
dey
bpl @l
rts
ptr4_to_fr1:
ldy #5
@l:
lda (ptr4),y
sta FR1,y
dey
bpl @l
rts
; truncate FR0 to integer (no rounding: 2.8 -> 2)
trunc_fr0:
lda FR0
and #$7f ; strip sign bit (we only care about exponent magnitude)
sec
sbc #$3f ; A now holds # of base-100 digits in integer part
bcs @ok ; # of int digits > 0?
jmp ZFR0 ; no, zero out FR0 and exit
@ok:
cmp #5 ; are there <= 5 int digits?
bcs @done ; no, the number's already an integer.
tax ; zero out digits: X is first one after decimal point
lda #0
@zloop:
sta FR0+1,x
inx
cpx #5
bne @zloop
@done:
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; void __fastcall__ big_trunc(bignump b);
sta FLPTR
stx FLPTR+1
jsr FLD0P
jsr trunc_fr0
jsr FST0P
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; void __fastcall__ ulong_to_big(const unsigned long l, bignum *b);
_ulong_to_big:
sta ptr3
stx ptr3+1 ; save b (destination)
jsr popeax ; get low 16 bits of l in A/X (hi 16 bits in sreg)
sta FR0
stx FR0+1
jsr IFP ; convert A/X to fp
jsr fr0_to_fptemp ; stash it
lda sreg ; now get high 16 bits of l in A/X
sta FR0
ldx sreg+1
stx FR0+1
jsr IFP ; convert to fp
lda #<BIG_64K ; high value needs to be multiplied by 65536
sta ptr4
lda #>BIG_64K
sta ptr4+1
jsr ptr4_to_fr1
jsr FMUL ; multiply...
jsr fptemp_to_fr1 ; grab low value
jsr FADD ; add to total
jmp fr0_to_ptr3 ; store it in b and we're done.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; char __fastcall__ big_to_ulong(bignump b, unsigned long *l);
;
; This works, but it's not small, fast, or elegant...
_big_to_ulong:
sta ptr3
stx ptr3+1 ; save *l (dest)
jsr popax ; get b
sta FLPTR
sta sreg
stx FLPTR+1
stx sreg+1
jsr FLD0P ; there's a typo in atari.inc, should be FLD1P
ldx #<BIG_64K ; FR1 = 65536
ldy #>BIG_64K
jsr FLD1R
jsr FDIV ; FR0 = FR0 / FR1
jsr trunc_fr0 ; FR0 = INT(FR0)
jsr fr0_to_fptemp ; stash for later...
jsr FPI ; get integer form
bcc @ok ; OS supposed to return with C set if range error
; failed, return 0 to caller
lda #0
tax
rts
@ok:
ldy #2 ; save top 16 bits of result where they belong
lda FR0
sta (ptr3),y
iny
lda FR0+1
sta (ptr3),y
jsr fptemp_to_fr0 ; this is int((*b)/65536) in FR0 now
ldx #<BIG_64K ; FR1 = 65536
ldy #>BIG_64K
jsr FLD1R
jsr FMUL ; FR0 now int((*b)/65536)*65536
jsr FMOVE ; FR1 = FR0
ldx sreg ; reload original *b in FR0
ldy sreg+1
jsr FLD0R
jsr FSUB ; FR0 = FR0 - FR1
jsr FPI
ldy #0 ; store low 16 bits where they belong
lda FR0
sta (ptr3),y
iny
lda FR0+1
sta (ptr3),y
; success. return 1 to caller.
tya
ldx #0
rts
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