collapseos/apps/zasm/util.asm

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2019-04-30 15:51:39 -04:00
; run RLA the number of times specified in B
rlaX:
; first, see if B == 0 to see if we need to bail out
inc b
dec b
ret z ; Z flag means we had B = 0
.loop: rla
djnz .loop
ret
; Copy BC bytes from (HL) to (DE).
copy:
; first, let's see if BC is zero. if it is, we have nothing to do.
; remember: 16-bit inc/dec don't modify flags. that's why we check B
; and C separately.
inc b
dec b
jr nz, .proceed
inc c
dec c
ret z ; zero? nothing to do
.proceed:
push bc
push de
push hl
ldir
pop hl
pop de
pop bc
ret
callHL:
jp (hl)
ret
; If string at (HL) starts with ( and ends with ), "enter" into the parens
; (advance HL and put a null char at the end of the string) and set Z.
; Otherwise, do nothing and reset Z.
enterParens:
ld a, (hl)
cp '('
ret nz ; nothing to do
push hl
ld a, 0 ; look for null char
; advance until we get null
.loop:
cpi
jp z, .found
jr .loop
.found:
dec hl ; cpi over-advances. go back to null-char
dec hl ; looking at the last char before null
ld a, (hl)
cp ')'
jr nz, .doNotEnter
; We have parens. While we're here, let's put a null
xor a
ld (hl), a
pop hl ; back at the beginning. Let's advance.
inc hl
cp a ; ensure Z
ret ; we're good!
.doNotEnter:
pop hl
call JUMP_UNSETZ
ret