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93 lines
1.6 KiB
NASM
93 lines
1.6 KiB
NASM
; Sets Z is A is ' ' or '\t' (whitespace)
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isWS:
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cp ' '
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ret z
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cp 0x09
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ret
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; Copy string from (HL) in (DE), that is, copy bytes until a null char is
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; encountered. The null char is also copied.
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; HL and DE point to the char right after the null char.
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strcpyM:
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ld a, (hl)
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ld (de), a
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inc hl
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inc de
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or a
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jr nz, strcpyM
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ret
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; Like strcpyM, but preserve HL and DE
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strcpy:
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push hl
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push de
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call strcpyM
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pop de
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pop hl
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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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or a ; 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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; Returns length of string at (HL) in A.
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; Doesn't include null termination.
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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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xor a ; 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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; DE * BC -> DE (high) and HL (low)
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multDEBC:
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ld hl, 0
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ld a, 0x10
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.loop:
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add hl, hl
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rl e
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rl d
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jr nc, .noinc
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add hl, bc
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jr nc, .noinc
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inc de
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.noinc:
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dec a
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jr nz, .loop
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ret
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