mirror of https://github.com/hsoft/collapseos.git
86 lines
1.8 KiB
NASM
86 lines
1.8 KiB
NASM
; Fill B bytes at (HL) with A
|
|
fill:
|
|
push bc
|
|
push hl
|
|
.loop:
|
|
ld (hl), a
|
|
inc hl
|
|
djnz .loop
|
|
pop hl
|
|
pop bc
|
|
ret
|
|
|
|
; Increase HL until the memory address it points to is equal to A for a maximum
|
|
; of 0xff bytes. Returns the new HL value as well as the number of bytes
|
|
; iterated in A.
|
|
; If a null char is encountered before we find A, processing is stopped in the
|
|
; same way as if we found our char (so, we look for A *or* 0)
|
|
; Set Z if the character is found. Unsets it if not
|
|
findchar:
|
|
push bc
|
|
ld c, a ; let's use C as our cp target
|
|
ld b, 0xff
|
|
|
|
.loop: ld a, (hl)
|
|
cp c
|
|
jr z, .match
|
|
or a ; cp 0
|
|
jr z, .nomatch
|
|
inc hl
|
|
djnz .loop
|
|
.nomatch:
|
|
inc a ; unset Z
|
|
jr .end
|
|
.match:
|
|
; We ran 0xff-B loops. That's the result that goes in A.
|
|
ld a, 0xff
|
|
sub b
|
|
cp a ; ensure Z
|
|
.end:
|
|
pop bc
|
|
ret
|
|
|
|
|
|
; Compares strings pointed to by HL and DE up to A count of characters. If
|
|
; equal, Z is set. If not equal, Z is reset.
|
|
strncmp:
|
|
push bc
|
|
push hl
|
|
push de
|
|
|
|
ld b, a
|
|
.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
|
|
djnz .loop
|
|
; We went through all chars with success, but our current Z flag is
|
|
; unset because of the cp 0. Let's do a dummy CP to set the Z flag.
|
|
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
|
|
|
|
; Transforms the character in A, if it's in the a-z range, into its upcase
|
|
; version.
|
|
upcase:
|
|
cp 'a'
|
|
ret c ; A < 'a'. nothing to do
|
|
cp 'z'+1
|
|
ret nc ; A >= 'z'+1. nothing to do
|
|
; 'a' - 'A' == 0x20
|
|
sub 0x20
|
|
ret
|