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collapseos/apps/zasm/util.asm
2019-10-04 20:26:21 -04:00

238 lines
4.4 KiB
NASM

; 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
callHL:
jp (hl)
ret
; HL - DE -> HL
subDEFromHL:
push af
ld a, l
sub e
ld l, a
ld a, h
sbc a, d
ld h, a
pop af
ret
; make Z the opposite of what it is now
toggleZ:
jp z, unsetZ
cp a
ret
; Returns length of string at (HL) in A.
; Doesn't include null termination.
strlen:
push bc
push hl
ld bc, 0
ld a, 0 ; 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
; Sets Z if string at (HL) is one character long
strIs1L:
xor a
cp (hl)
jp z, unsetZ ; empty string
inc hl
cp (hl) ; Z has proper value
dec hl ; doesn't touch Z
ret
; Compares strings pointed to by HL and DE up to A count of characters in a
; case-insensitive manner.
; If equal, Z is set. If not equal, Z is reset.
strncmpI:
push bc
push hl
push de
ld b, a
.loop:
ld a, (de)
call upcase
ld c, a
ld a, (hl)
call upcase
cp c
jr nz, .end ; not equal? break early. NZ is carried out
; to the called
or a ; cp 0. If our chars are null, stop the cmp
jr z, .end ; The positive result will be carried to the
; caller
inc hl
inc de
djnz .loop
; Success
; We went through all chars with success. Ensure Z
cp a
.end:
pop de
pop hl
pop bc
; 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
; 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
cp 0 ; 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
; 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 unsetZ
ret
; Scans (HL) and sets Z according to whether the string is double quoted, that
; is, starts with a " and ends with a ". If it is double quoted, "enter" them,
; that is, advance HL by one and transform the ending quote into a null char.
; If the string isn't double-enquoted, HL isn't changed.
enterDoubleQuotes:
ld a, (hl)
cp '"'
ret nz
push hl
inc hl
ld a, (hl)
or a ; already end of string?
jr z, .nomatch
xor a
call findchar ; go to end of string
dec hl
ld a, (hl)
cp '"'
jr nz, .nomatch
; We have a match, replace ending quote with null char
xor a
ld (hl), a
; Good, let's go back
pop hl
; ... but one char further
inc hl
cp a ; ensure Z
ret
.nomatch:
call unsetZ
pop hl
ret
; Find string (HL) in string list (DE) of size B, in a case-insensitive manner.
; Each string is C bytes wide.
; Returns the index of the found string. Sets Z if found, unsets Z if not found.
findStringInList:
push de
push bc
.loop:
ld a, c
call strncmpI
ld a, c
call addDE
jr z, .match
djnz .loop
; no match, Z is unset
pop bc
pop de
ret
.match:
; Now, we want the index of our string, which is equal to our initial B
; minus our current B. To get this, we have to play with our registers
; and stack a bit.
ld d, b
pop bc
ld a, b
sub d
pop de
cp a ; ensure Z
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