206 lines
8.1 KiB
Plaintext
Executable File
206 lines
8.1 KiB
Plaintext
Executable File
.INCLUDE GRAFTYPES.TEXT
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;-----------------------------------------------------------
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;
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; --> PUTLINE.TEXT
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;
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; Decompose a line segment into a list of inversion points.
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;
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;
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.PROC PUTLINE,5
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.REF SETSIZE
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;------------------------------------------------------------------
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;
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; PROCEDURE PutLine(pt1,pt2: Point; dst: Handle; VAR index,bufMax: INTEGER);
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;
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; INVERSION POINTS FOR A LINE SEGMENT
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;
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; SP OFFSETS OF PARAMETERS:
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;
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PARAMSIZE .EQU 20 ;TOTAL SIZE OF PARAMETERS
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PT1 .EQU PARAMSIZE+4-4 ;LONG, POINT (VALUE)
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PT2 .EQU PT1-4 ;LONG, POINT (VALUE)
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BUF .EQU PT2-4 ;LONG, HANDLE
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INDEX .EQU BUF-4 ;LONG, (VAR)
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BUFMAX .EQU INDEX-4 ;LONG, (VAR)
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MOVEM.L D3-D7/A2-A4,-(SP) ;SAVE REGS, 8*4 ==> 32
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;-----------------------------------------------------
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;
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; IF LINE IS VERTICAL, IGNORE IT.
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;
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MOVE PT1+H+32(SP),D2 ;GET 1ST POINT'S HORIZ
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MOVE PT2+H+32(SP),D4 ;GET 2ND POINT'S HORIZ
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CMP D2,D4 ;IS THIS A VERTICAL LINE ?
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BEQ GOHOME ;YES, IGNORE IT
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;------------------------------------------------------
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;
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; CALC BYTESNEEDED = 8 * ( Min(ABS(dh),ABS(dv)) + 1)
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;
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MOVE D2,D0 ;GET H1
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SUB D4,D0 ;SUBTRACT H2
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BPL.S DHPOS ;BR IF DH POS
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NEG D0 ;ELSE TAKE ABSOLUTE VALUE
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DHPOS MOVE PT1+V+32(SP),D1 ;GET V1
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SUB PT2+V+32(SP),D1 ;SUBTRACT V2
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BPL.S DVPOS ;BR IF DV POS
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NEG D1 ;ELSE TAKE ABSOLUTE VALUE
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DVPOS CMP D1,D0 ;IS DH <= DV ?
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BLE.S DHLESS ;YES, CONTINUE
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MOVE D1,D0 ;NO, PUT MIN(DH,DV) INTO D0
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DHLESS ADD #1,D0 ;CALC MIN(DH,DV)+1
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LSL #3,D0 ;TIMES EIGHT FOR BYTESNEEDED
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MOVE.L BUF+32(SP),A3 ;GET DSTHANDLE
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MOVE.L INDEX+32(SP),A4 ;POINT TO CURRENT INDEX
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;-----------------------------------------------------
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;
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; GROW POINT BUFFER AS NECESSARY TO HOLD BYTESNEEDED
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;
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ADD (A4),D0 ;NEWSIZE := INDEX + BYTESNEEDED
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MOVE.L BUFMAX+32(SP),A0 ;POINT TO BUFMAX
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CMP (A0),D0 ;DO WE HAVE TO GROW DSTBUF ?
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BLE.S NOGROW ;NO, CONTINUE
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ADD #512,D0 ;GROW IN CHUNKS
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MOVE D0,(A0) ;UPDATE NEW BUFMAX
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MOVE.L A3,-(SP) ;PUSH DSTBUF HANDLE
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MOVE D0,-(SP) ;PUSH NEW BUFMAX
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JSR SETSIZE ;MAKE THE BUFFER BIGGER
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MOVE PT1+H+32(SP),D2 ;RESTORE CLOBBERED REG
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NOGROW
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MOVE.L (A3),A3 ;DE-REFERENCE DSTHANDLE
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ADD (A4),A3 ;ADD INDEX TO BUFPTR
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;-----------------------------------------------------
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;
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; IF LINE IS HORIZONTAL, PUT ITS TWO ENDPOINTS
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;
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MOVE PT1+V+32(SP),D1 ;GET 1ST POINT'S VERT
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MOVE PT2+V+32(SP),D3 ;GET 2ND POINT'S VERT
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CMP D1,D3 ;IS THIS A HORIZONTAL LINE ?
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BNE.S SLANTED ;NO, BRANCH
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MOVE D1,(A3)+ ;PUT V1 VERT COORD
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MOVE D2,(A3)+ ;PUT H1 HORIZ COORD
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MOVE D3,(A3)+ ;PUT V2 VERT COORD
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MOVE D4,(A3)+ ;PUT H2 HORIZ COORD
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BRA.S DONE ;UPDATE INDEX AND QUIT
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;------------------------------------------------------
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;
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; LINE IS SLANTED. DIVIDE IT INTO HORIZONTAL SLABS
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; AND PUT THE TWO ENDPOINTS OF EACH SLAB.
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;
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; START BY SORTING POINTS VERTICALLY.
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;
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SLANTED BGT.S NOSWAP ;SKIP IF ALREADY IN ORDER
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EXG D1,D3 ;SORT POINTS BY VERTICAL
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EXG D2,D4 ;SWAP HORIZ TO MATCH
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NOSWAP MOVE D1,D6 ;INIT V TO TOPV
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;------------------------------------------------------------
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;
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; CALCULATE FIXED POINT SLOPE = FixRatio(dh,dv);
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;
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CLR.L -(SP) ;MAKE ROOM FOR FCN RESULT
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MOVE D4,-(SP) ;PUSH BOTTOM HORIZ
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SUB D2,(SP) ;CALC DH
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MOVE D3,-(SP) ;PUSH BOTTOM VERT
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SUB D1,(SP) ;CALC DV
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_FixRatio ;CALC FIXED POINT SLOPE
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MOVE.L (SP)+,D7 ;POP RESULT
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;---------------------------------------------------------
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;
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; SET UP STARTING HORIZ FIXED POINT.
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;
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MOVE.W D2,D1
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SWAP D1 ;HORIZ.INT := TOP HORIZ
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MOVE.W #$8000,D1 ;HORIZ.FRACT := 1/2
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;
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; ADJUST HORIZ DEPENDING ON SIGN AND MAGNITUDE OF SLOPE
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;
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MOVE.L D7,D0 ;COPY SLOPE
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ASR.L #1,D0 ;CALC SLOPE/2
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ADD.L D0,D1 ;HORIZ := HORIZ + SLOPE/2
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MOVE.L #$00010000,D0
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TST.L D7 ;IS SLOPE NEG ?
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BMI.S NEGSLOPE ;YES, CONTINUE
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CMP.L D0,D7 ;IS SLOPE < ONE ?
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BGE.S SLOPEOK ;NO, CONTINUE
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ADD.L D7,D1 ;ADD SLOPE TO LEFTEDGE
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BRA.S SLOPEOK ;CONTINUE
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NEGSLOPE CMP.L #$FFFF0000,D7 ;IS SLOPE > -ONE ?
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BGE.S SLOPEOK ;YES, CONTINUE
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ADD.L D0,D1 ;YES, HORIZ := HORIZ + 1
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SLOPEOK
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;------------------------------------------------------
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;
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; FOR VERT:=TOPV TO BOTV-1 ADD SLOPE TO HORIZ AND PUT SLABS
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;
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MOVE D2,D5 ;H:=TOPH
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LOOP SWAP D1 ;GET HORIZ.INT INTO D1 LOWER
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CMP D1,D5 ;HAS HORIZ.INT CHANGED ?
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BEQ.S NOCHNG ;NO, CONTINUE
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MOVE D6,(A3)+ ;YES, PUT VERT COORD
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MOVE D5,(A3)+ ;PUT OLD HORIZ COORD
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MOVE.W D1,D5 ;OLDH := HORIZ.INT
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MOVE D6,(A3)+ ;PUT VERT COORD
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MOVE D5,(A3)+ ;PUT NEW HORIZ COORD
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NOCHNG SWAP D1 ;PUTBACK HORIZ.INT INTO D1 UPPER
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ADD #1,D6 ;VERT:=VERT+1
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ADD.L D7,D1 ;ADD SLOPE TO HORIZ
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CMP D6,D3 ;IS VERT AT BOTTOM VERT YET ?
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BNE LOOP ;NO, GO FOR MORE
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;-------------------------------------------------
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;
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; FINISH UP LAST SLAB
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;
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CMP D4,D5 ;IS OLDH = BOTTOM H ?
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BEQ.S DONE ;YES, CONTINUE
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MOVE D6,(A3)+ ;NO, PUT VERT COORD
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MOVE D5,(A3)+ ;PUT HORIZ COORD
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MOVE D6,(A3)+ ;PUT VERT COORD
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MOVE D4,(A3)+ ;PUT BOTTOM H COORD
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;---------------------------------------------------
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;
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; UPDATE INDEX TO REFLECT POINTS ADDED.
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;
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DONE MOVE.L BUF+32(SP),A0 ;GET DSTHANDLE
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SUB.L (A0),A3 ;INDEX := BUFPTR-BUFSTART
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MOVE A3,(A4) ;UPDATE INDEX
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GOHOME MOVEM.L (SP)+,D3-D7/A2-A4 ;RESTORE REGS
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MOVE.L (SP)+,A0
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ADD.W #PARAMSIZE,A7
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JMP (A0)
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.END
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