1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
;
; Ullrich von Bassewitz, 07.08.1998
;
; CC65 runtime: division for unsigned ints
;
; Don't use tmp1 here, the signed division tunnels data with it!
.export tosudiva0, tosudivax, udiv16
.import popptr1
.importzp sreg, ptr1, ptr4
tosudiva0:
ldx #$00 ; Clear high byte
tosudivax:
sta ptr4
stx ptr4+1 ; Save right operand
jsr popptr1 ; Get left operand
; Do the division
jsr udiv16
; Result is in ptr1, remainder in sreg
lda ptr1
ldx ptr1+1
rts
;---------------------------------------------------------------------------
; 16by16 division. Divide ptr1 by ptr4. Result is in ptr1, remainder in sreg
; (see mult-div.s from "The Fridge").
; This is also the entry point for the signed division
udiv16: lda #0
sta sreg+1
ldy #16
ldx ptr4+1
beq udiv16by8a
L0: asl ptr1
rol ptr1+1
rol a
rol sreg+1
tax
cmp ptr4
lda sreg+1
sbc ptr4+1
bcc L1
sta sreg+1
txa
sbc ptr4
tax
inc ptr1
L1: txa
dey
bne L0
sta sreg
rts
;---------------------------------------------------------------------------
; 16by8 division
udiv16by8a:
@L0: asl ptr1
rol ptr1+1
rol a
bcs @L1
cmp ptr4
bcc @L2
@L1: sbc ptr4
inc ptr1
@L2: dey
bne @L0
sta sreg
rts
|
