collapseos/apps/lib/util.asm

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NASM
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2019-11-20 20:58:26 -05:00
; Sets Z is A is ' ' or '\t' (whitespace)
isWS:
cp ' '
ret z
cp 0x09
ret
; Advance HL to next WS.
; Set Z if WS found, unset if end-of-string.
toWS:
ld a, (hl)
call isWS
ret z
or a
jp z, unsetZ
inc hl
jr toWS
; Consume following whitespaces in HL until a non-WS is hit.
; Set Z if non-WS found, unset if end-of-string.
rdWS:
ld a, (hl)
call isWS
jr nz, .ok
or a
jp z, unsetZ
inc hl
jr rdWS
.ok:
cp a ; ensure Z
ret
2019-07-14 17:29:00 -04:00
; Copy string from (HL) in (DE), that is, copy bytes until a null char is
; encountered. The null char is also copied.
; HL and DE point to the char right after the null char.
strcpyM:
ld a, (hl)
ld (de), a
inc hl
inc de
or a
jr nz, strcpyM
ret
; Like strcpyM, but preserve HL and DE
strcpy:
push hl
push de
call strcpyM
pop de
pop hl
ret
; Compares strings pointed to by HL and DE until one of them hits its null char.
; If equal, Z is set. If not equal, Z is reset.
strcmp:
push hl
push de
.loop:
ld a, (de)
cp (hl)
jr nz, .end ; not equal? break early. NZ is carried out
; to the called
or a ; If our chars are null, stop the cmp
jr z, .end ; The positive result will be carried to the
; caller
inc hl
inc de
jr .loop
.end:
pop de
pop hl
; Because we don't call anything else than CP that modify the Z flag,
; our Z value will be that of the last cp (reset if we broke the loop
; early, set otherwise)
ret
; Given a string at (HL), move HL until it points to the end of that string.
strskip:
push af
xor a ; look for null char
.loop:
cp (hl)
jp z, .found
inc hl
jr .loop
.found:
pop af
ret
; Returns length of string at (HL) in A.
; Doesn't include null termination.
strlen:
push bc
push hl
ld bc, 0
xor a ; look for null char
.loop:
cpi
jp z, .found
jr .loop
.found:
; How many char do we have? the (NEG BC)-1, which started at 0 and
; decreased at each CPI call. In this routine, we stay in the 8-bit
; realm, so C only.
ld a, c
neg
dec a
pop hl
pop bc
ret