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