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https://github.com/hsoft/collapseos.git
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180 lines
3.5 KiB
NASM
180 lines
3.5 KiB
NASM
; run RLA the number of times specified in B
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rlaX:
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; first, see if B == 0 to see if we need to bail out
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inc b
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dec b
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ret z ; Z flag means we had B = 0
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.loop: rla
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djnz .loop
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ret
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callHL:
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jp (hl)
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ret
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; Compare HL with DE and sets Z and C in the same way as a regular cp X where
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; HL is A and DE is X.
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cpHLDE:
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ld a, h
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cp d
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ret nz ; if not equal, flags are correct
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ld a, l
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cp e
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ret ; flags are correct
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; HL - DE -> HL
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subDEFromHL:
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push af
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ld a, l
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sub e
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ld l, a
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ld a, h
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sbc d
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ld h, a
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pop af
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ret
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; Returns length of string at (HL) in A.
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strlen:
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push bc
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push hl
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ld bc, 0
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ld a, 0 ; look for null char
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.loop:
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cpi
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jp z, .found
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jr .loop
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.found:
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; How many char do we have? the (NEG BC)-1, which started at 0 and
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; decreased at each CPI call. In this routine, we stay in the 8-bit
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; realm, so C only.
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ld a, c
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neg
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dec a
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pop hl
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pop bc
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ret
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; Compares strings pointed to by HL and DE up to A count of characters in a
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; case-insensitive manner.
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; If equal, Z is set. If not equal, Z is reset.
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strncmpI:
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push bc
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push hl
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push de
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ld b, a
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.loop:
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ld a, (de)
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call upcase
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ld c, a
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ld a, (hl)
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call upcase
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cp c
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jr nz, .end ; not equal? break early. NZ is carried out
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; to the called
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or a ; cp 0. If our chars are null, stop the cmp
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jr z, .end ; The positive result will be carried to the
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; caller
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inc hl
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inc de
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djnz .loop
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; Success
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; We went through all chars with success. Ensure Z
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cp a
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.end:
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pop de
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pop hl
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pop bc
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; Because we don't call anything else than CP that modify the Z flag,
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; our Z value will be that of the last cp (reset if we broke the loop
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; early, set otherwise)
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ret
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; Compares strings pointed to by HL and DE until one of them hits its null char.
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; If equal, Z is set. If not equal, Z is reset.
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strcmp:
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push hl
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push de
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.loop:
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ld a, (de)
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cp (hl)
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jr nz, .end ; not equal? break early. NZ is carried out
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; to the called
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cp 0 ; If our chars are null, stop the cmp
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jr z, .end ; The positive result will be carried to the
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; caller
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inc hl
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inc de
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jr .loop
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.end:
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pop de
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pop hl
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; Because we don't call anything else than CP that modify the Z flag,
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; our Z value will be that of the last cp (reset if we broke the loop
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; early, set otherwise)
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ret
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; If string at (HL) starts with ( and ends with ), "enter" into the parens
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; (advance HL and put a null char at the end of the string) and set Z.
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; Otherwise, do nothing and reset Z.
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enterParens:
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ld a, (hl)
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cp '('
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ret nz ; nothing to do
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push hl
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ld a, 0 ; look for null char
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; advance until we get null
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.loop:
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cpi
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jp z, .found
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jr .loop
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.found:
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dec hl ; cpi over-advances. go back to null-char
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dec hl ; looking at the last char before null
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ld a, (hl)
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cp ')'
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jr nz, .doNotEnter
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; We have parens. While we're here, let's put a null
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xor a
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ld (hl), a
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pop hl ; back at the beginning. Let's advance.
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inc hl
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cp a ; ensure Z
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ret ; we're good!
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.doNotEnter:
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pop hl
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call unsetZ
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ret
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; Find string (HL) in string list (DE) of size B, in a case-insensitive manner.
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; Each string is C bytes wide.
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; Returns the index of the found string. Sets Z if found, unsets Z if not found.
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findStringInList:
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push de
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push bc
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.loop:
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ld a, c
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call strncmpI
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ld a, c
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call addDE
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jr z, .match
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djnz .loop
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; no match, Z is unset
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pop bc
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pop de
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ret
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.match:
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; Now, we want the index of our string, which is equal to our initial B
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; minus our current B. To get this, we have to play with our registers
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; and stack a bit.
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ld d, b
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pop bc
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ld a, b
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sub d
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pop de
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cp a ; ensure Z
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ret
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