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112 lines
2.8 KiB
NASM
112 lines
2.8 KiB
NASM
; *** Requirements ***
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; lib/parse
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;
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; *** Consts ***
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; maximum number of bytes to receive as args in all commands. Determines the
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; size of the args variable.
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.equ PARSE_ARG_MAXCOUNT 3
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; *** Code ***
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; Parse arguments at (HL) with specifiers at (DE) into (IX).
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;
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; Args specifiers are a series of flag for each arg:
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; Bit 0 - arg present: if unset, we stop parsing there
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; Bit 1 - is word: this arg is a word rather than a byte. Because our
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; destination are bytes anyway, this doesn't change much except
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; for whether we expect a space between the hex pairs. If set,
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; you still need to have a specifier for the second part of
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; the multibyte.
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; Bit 2 - optional: If set and not present during parsing, we don't error out
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; and write zero
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;
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; Bit 3 - String argument: If set, this argument is a string. A pointer to the
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; read string, null terminated (max 0x20 chars) will
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; be placed in the next two bytes. This has to be the
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; last argument of the list and it stops parsing.
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; Sets A to nonzero if there was an error during parsing, zero otherwise.
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parseArgs:
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push bc
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push de
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push hl
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push ix
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; init the arg value to a default 0
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xor a
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ld (ix), a
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ld (ix+1), a
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ld (ix+2), a
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ld b, PARSE_ARG_MAXCOUNT
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.loop:
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ld a, (hl)
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; is this the end of the line?
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or a ; cp 0
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jr z, .endofargs
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; Get the specs
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ld a, (de)
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bit 0, a ; do we have an arg?
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jr z, .error ; not set? then we have too many args
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ld c, a ; save the specs for multibyte check later
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bit 3, a ; is our arg a string?
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jr z, .notAString
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; our arg is a string. Let's place HL in our next two bytes and call
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; it a day. Little endian, remember
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ld (ix), l
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ld (ix+1), h
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jr .success ; directly to success: skip endofargs checks
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.notAString:
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call parseHexPair
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jr c, .error
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; we have a good arg and we need to write A in (IX).
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ld (ix), a
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; Good! increase counters
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inc de
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inc ix
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inc hl ; get to following char (generally a space)
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; Our arg is parsed, our pointers are increased. Normally, HL should
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; point to a space *unless* our argspec indicates a multibyte arg.
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bit 1, c
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jr nz, .nospacecheck ; bit set? no space check
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; do we have a proper space char (or null char)?
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ld a, (hl)
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or a
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jr z, .endofargs
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cp ' '
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jr nz, .error
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inc hl
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.nospacecheck:
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djnz .loop
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; If we get here, it means that our next char *has* to be a null char
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ld a, (hl)
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or a ; cp 0
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jr z, .success ; zero? great!
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jr .error
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.endofargs:
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; We encountered our null char. Let's verify that we either have no
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; more args or that they are optional
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ld a, (de)
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or a
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jr z, .success ; no arg? success
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bit 2, a
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jr z, .error ; if unset, arg is not optional. error
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; success
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.success:
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xor a
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jr .end
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.error:
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inc a
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.end:
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pop ix
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pop hl
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pop de
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pop bc
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ret
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