146 lines
2.6 KiB
NASM
146 lines
2.6 KiB
NASM
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; *** Consts ***
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TOK_INSTR .equ 0x01
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TOK_DIRECTIVE .equ 0x02
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TOK_LABEL .equ 0x03
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TOK_EMPTY .equ 0xfe ; not a bad token, just an empty line
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TOK_BAD .equ 0xff
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.equ SCRATCHPAD_SIZE 0x20
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; *** Variables ***
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scratchpad:
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.fill SCRATCHPAD_SIZE
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; *** Code ***
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; Sets Z is A is ';' or null.
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isLineEndOrComment:
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cp ';'
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ret z
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or a ; cp 0
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ret
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; Sets Z is A is ' ' '\t' or ','
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isSep:
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cp ' '
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ret z
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cp 0x09
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ret z
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cp ','
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ret
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; Sets Z is A is ' ', ',', ';', CR, LF, or null.
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isSepOrLineEnd:
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call isSep
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ret z
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call isLineEndOrComment
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ret
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; Checks whether string at (HL) is a label, that is, whether it ends with a ":"
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; Sets Z if yes, unset if no.
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;
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; If it's a label, we change the trailing ':' char with a null char. It's a bit
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; dirty, but it's the easiest way to proceed.
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isLabel:
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push hl
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ld a, ':'
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call JUMP_FINDCHAR
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ld a, (hl)
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cp ':'
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jr nz, .nomatch
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; We also have to check that it's our last char.
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inc hl
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ld a, (hl)
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or a ; cp 0
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jr nz, .nomatch ; not a null char following the :. no match.
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; We have a match!
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; Remove trailing ':'
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xor a ; Z is set
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ld (hl), a
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jr .end
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.nomatch:
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call JUMP_UNSETZ
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.end:
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pop hl
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ret
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; read word in (HL) and put it in (scratchpad), null terminated, for a maximum
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; of SCRATCHPAD_SIZE-1 characters. As a result, A is the read length. HL is
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; advanced to the next separator char.
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readWord:
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push bc
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push de
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ld de, scratchpad
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ld b, SCRATCHPAD_SIZE-1
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.loop:
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ld a, (hl)
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call isSepOrLineEnd
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jr z, .success
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ld (de), a
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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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xor a
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ld (de), a
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ld a, SCRATCHPAD_SIZE-1
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sub a, b
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.end:
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pop de
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pop bc
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ret
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; (HL) being a string, advance it to the next non-sep character.
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; Set Z if we could do it before the line ended, reset Z if we couldn't.
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toWord:
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.loop:
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ld a, (hl)
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call isLineEndOrComment
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jr z, .error
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call isSep
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jr nz, .success
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inc hl
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jr .loop
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.error:
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call JUMP_UNSETZ
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ret
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.success:
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xor a ; ensure Z
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ret
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; Parse line in (HL) and read the next token in BC. The token is written on
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; two bytes (B and C). B is a token type (TOK_* constants) and C is an ID
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; specific to that token type.
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; Advance HL to after the read word.
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; If no token matches, TOK_BAD is written to B
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tokenize:
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call toWord
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jr nz, .emptyline
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call readWord
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push hl ; Save advanced HL for later
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ld hl, scratchpad
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call isLabel
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jr z, .label
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call getInstID
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jr z, .instr
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call getDirectiveID
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jr z, .direc
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; no match
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ld b, TOK_BAD
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jr .end
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.instr:
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ld b, TOK_INSTR
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jr .end
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.direc:
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ld b, TOK_DIRECTIVE
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jr .end
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.label:
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ld b, TOK_LABEL
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.end:
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ld c, a
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pop hl
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ret
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.emptyline:
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ld b, TOK_EMPTY
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; no HL to pop, we jumped before the push
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ret
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