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collapseos/apps/lib/ari.asm
2019-11-22 14:45:12 -05:00

45 lines
705 B
NASM

; Borrowed from Tasty Basic by Dimitri Theulings (GPL).
; Divide HL by DE, placing the result in BC and the remainder in HL.
divide:
push hl ; --> lvl 1
ld l, h ; divide h by de
ld h, 0
call .dv1
ld b, c ; save result in b
ld a, l ; (remainder + l) / de
pop hl ; <-- lvl 1
ld h, a
.dv1:
ld c, 0xff ; result in c
.dv2:
inc c ; dumb routine
call .subde ; divide using subtract and count
jr nc, .dv2
add hl, de
ret
.subde:
ld a, l
sub e ; subtract de from hl
ld l, a
ld a, h
sbc a, d
ld h, a
ret
; DE * BC -> DE (high) and HL (low)
multDEBC:
ld hl, 0
ld a, 0x10
.loop:
add hl, hl
rl e
rl d
jr nc, .noinc
add hl, bc
jr nc, .noinc
inc de
.noinc:
dec a
jr nz, .loop
ret