ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

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Assembly Source File | 1991-03-07 | 12.4 KB | 458 lines

; hercline.asm: line-drawing routine for the Hercules monochrome ; graphics card. ; Copyright (C) 1990 by Nicholas Wilt. All rights reserved. .MODEL COMPACT PAGE ,132 .CODE ASSUME cs:_TEXT,ds:_TEXT PUBLIC _hercline BytesPerRow EQU 90 ; Change to 80 for 640x400 mode BytesPerBank EQU 7830 ; Change to 8000 for 640x400 mode ; BytesPerBank is (YRes/4)*BytesPerRow. ; The IncY and DecY macros update the offset-mask pair in DI and AH to ; point to the above or below pixel. They do not depend on whether ; the routine is drawing or erasing. IncY MACRO LOCAL ExitIncY add di,bp ;; 8192 in BP jno ExitIncY ;; Leave if done ;; Undo and compensate sub di,24576+BytesPerBank-BytesPerRow+8192 jge ExitIncY ;; Leave if done add di,BytesPerBank ;; Undo and compensate ExitIncY: ENDM DecY MACRO LOCAL ExitDecY sub di,bp ;; 8192 in BP jns ExitDecY ;; Leave if done sub di,BytesPerRow-8192-24576 ;; Undo and compensate jge ExitDecY ;; Leave if done add di,BytesPerBank ;; Undo and compensate ExitDecY: ENDM ; ****************************************************************** ; void hercline(int x1, int y1, int x2, int y2, int color); ; C-callable in tiny, small, compact memory models. ; To use medium, large, or huge, just add 2 to the indices when ; loading the parameters. ; Color is nonzero to draw the line, 0 to erase the line (set to 0). ; ****************************************************************** _hercline PROC push bp ; Enter mov bp,sp ; Set up stack frame push ds ; Save regs push di ; push si ; ; Add two to each of the indices below to use a large code model. mov ax,[bp+4] ; Load x1 mov bx,[bp+6] ; Load y1 mov cx,[bp+8] ; Load x2 mov dx,[bp+10] ; Load y2 mov bp,[bp+12] ; Load color into BP. Dangerous. cld ; String ops go forward push cs ; Copy CS to DS for table lookup pop ds ; sub dx,bx ; DX <- diffy sub cx,ax ; CX <- diffx jge CheckForNull ; Jump if x2 >= x1 add ax,cx ; Make ax contain x2 add bx,dx ; Make bx contain y2 neg dx ; Negate diffx and diffy neg cx ; CheckForNull: ; Make sure the line's start and end ; points are different jnz DrawLine ; If diffx nonzero, draw the line or dx,dx ; Check diffy against 0 jnz DrawLine ; If not zero, draw the line jmp LeaveLine ; Do not try to draw line if ; x1==x2 && y1==y2 DrawLine: mov di,ax ; Load X into DI shr di,1 ; Divide by 8 for initial offset shr di,1 ; shr di,1 ; push cx ; Save DIFFX and DIFFY on stack push dx ; xchg ax,cx ; CX <- X; AX <- DIFFX mov ax,bx ; AX <- Y and bx,3 ; Add bank into offset shl bx,1 ; add di,Banks[BX] ; Lookup table located after routine shr ax,1 ; Divide Y by 4 shr ax,1 ; mov dx,BytesPerRow ; Load factor to multiply by mul dx ; Perform multiply add di,ax ; Add to offset and cl,7 ; x &= 7 mov ah,80h ; AH <- Initial mask shr ah,cl ; mov cx,0B000H ; Point DS and ES at video memory mov ds,cx ; mov es,cx ; mov al,[di] ; Pick up initial value pop dx ; Restore DIFFX and DIFFY pop bx ; or dx,dx ; If DIFFY 0, draw span jnz CheckDrawing call hercspan ; Call span routine jmp LeaveLine ; Leave CheckDrawing: or bp,bp ; Are we drawing? jnz CheckDIFFY ; Yes, don't take one's comp of mask not ah ; AH <- ~AH CheckDIFFY: or dx,dx ; Compare DIFFY to 0 jl DIFFYNegative ; Jump if less than jmp DIFFYPositive DIFFYNegative: mov cx,dx ; Copy DIFFY to CX for compare neg cx ; Negate for compare cmp cx,bx ; Compare to DIFFX jle LineXYM ; Jump if -diffy <= diffx LineYMX: ; Decrement Y before incrementing X ; (count is already in cx) mov si,dx ; Initialize error sar si,1 ; or bp,bp ; Are we drawing? mov bp,8192 ; Set up for changes in Y jne DrawYMX ; Jump if yes ; ************************************* ; Loop: Erase, decrement Y, and increment X if appropriate. ; ************************************* EraseYMX: and byte ptr [di],ah ; Erase sub di,bp ; Decrement Y js FixupEraseYMX ; Jump if we need to fixup ContinueEraseYMX: add si,bx ; Add DIFFX to error jns ELoopYMX ; Jump if positive loop EraseYMX ; Loop until done jmp short DoneEYMX ; Leave if done FixupEraseYMX: sub di,BytesPerRow-8192-24576 ; Undo and compensate jge ContinueEraseYMX ; Leave if done add di,BytesPerBank ; Undo and compensate jmp short ContinueEraseYMX ELoopYMX: ror ah,1 ; Increment X sbb di,-1 ; add si,dx ; Add DIFFY to error loop EraseYMX ; Loop until done DoneEYMX: and byte ptr [di],ah ; Last plot jmp LeaveLine ; Jump to exit code ; ************************************* ; Loop: Draw, decrement Y, and increment X if appropriate. ; ************************************* DrawYMX: or byte ptr [di],ah ; Plot sub di,bp ; Decrement Y js FixupDrawYMX ; Jump if fixup needed ContinueDrawYMX: add si,bx ; Add DIFFX to err jns DLoopYMX ; Jump if positive loop DrawYMX ; Loop until done jmp short DoneDYMX ; Jump if done FixupDrawYMX: sub di,BytesPerRow-8192-24576 ; Undo and compensate jge ContinueDrawYMX ; Leave if done add di,BytesPerBank ; Undo and compensate jmp short ContinueDrawYMX DLoopYMX: ror ah,1 ; Increment X adc di,0 ; add si,dx ; Add DIFFY loop DrawYMX ; Loop until done DoneDYMX: or byte ptr [di],ah ; Last plot jmp LeaveLine ; Jump to exit code LineXYM: mov cx,bx ; Get count mov si,bx ; Initialize error neg si ; sar si,1 ; or bp,bp ; Are we drawing? mov bp,8192 ; Set up for changes in Y jne DrawXYM ; Jump if drawing ; ************************************* ; Loop: Erase, increment X, and decrement Y if appropriate. ; ************************************* EraseXYM: and al,ah ; Erase ror ah,1 ; Rotate mask right jnc GetNextEraseXYM ; Jump if we need another byte ContinueEraseXYM: sub si,dx ; Subtract DIFFY from err jns ELoopXYM ; Jump if positive loop EraseXYM ; Loop until done jmp short DoneEXYM ; Jump if done GetNextEraseXYM: stosb ; Store and increment DI mov al,[di] ; Get next byte jmp short ContinueEraseXYM ELoopXYM: mov [di],al ; Save to video memory DecY ; Decrement Y mov al,[di] ; Load from video memory sub si,bx ; Subtract DIFFX from err loop EraseXYM ; Loop until done DoneEXYM: and al,ah ; Last plot jmp WriteLastByte ; Jump to exit code ; ************************************* ; Loop: Draw, increment X, and decrement Y if appropriate. ; ************************************* DrawXYM: or al,ah ; Plot ror ah,1 ; Rotate mask right jc GetNextDrawXYM ; Jump if we need another byte DrawContinueXYM: sub si,dx ; Subtract DIFFY from err jns DLoopXYM ; Jump if positive loop DrawXYM ; Loop until done jmp short DoneDXYM ; Jump if done GetNextDrawXYM: stosb ; Store and increment DI mov al,[di] ; jmp short DrawContinueXYM DLoopXYM: mov [di],al ; Save to video memory DecY ; Decrement Y mov al,[di] ; Load from video memory sub si,bx ; Subtract DIFFX loop DrawXYM ; Loop until done DoneDXYM: or al,ah ; Plot last jmp WriteLastByte ; Jump to exit code DIFFYPositive: cmp dx,bx ; Compare DIFFY to DIFFX jle LineXYP ; Jump if less than or equal to LineYPX: mov cx,dx ; Load count mov si,dx ; Initialize error neg si ; sar si,1 ; or bp,bp ; Are we drawing? mov bp,8192 ; Set up for changes in Y jne DrawYPX ; Jump if yes ; ************************************* ; Loop: Erase, increment Y, and increment X if appropriate. ; ************************************* EraseYPX: and byte ptr [di],ah ; Erase add di,bp ; Increment Y jo FixupEraseYPX ; Jump if fixup needed ContinueEraseYPX: add si,bx ; Add DIFFX to err jns ELoopYPX ; Jump if positive loop EraseYPX ; Loop until done jmp short DoneEYPX ; Jump if done FixupEraseYPX: sub di,24576+BytesPerBank-BytesPerRow+8192 jge ContinueEraseYPX ; Leave if done add di,BytesPerBank ; Undo and compensate jmp short ContinueEraseYPX ELoopYPX: ror ah,1 ; Increment X sbb di,-1 ; sub si,dx ; Subtract DIFFY from err loop EraseYPX ; Loop until done DoneEYPX: and byte ptr [di],ah ; Erase last jmp LeaveLine ; Jump to exit code ; ************************************* ; Loop: Draw, increment Y, and increment X if appropriate. ; ************************************* DrawYPX: or byte ptr [di],ah ; Plot add di,bp ; Increment Y jo FixupDrawYPX ; Jump if fixup needed ContinueDrawYPX: add si,bx ; Add DIFFX to err jns DLoopYPX ; Jump if positive loop DrawYPX ; Loop until done jmp short DoneDYPX ; Jump if done FixupDrawYPX: sub di,24576+BytesPerBank-BytesPerRow+8192 jge ContinueDrawYPX ; Leave if done add di,BytesPerBank ; Undo and compensate jmp short ContinueDrawYPX DLoopYPX: ror ah,1 ; Increment X adc di,0 ; sub si,dx ; Subtract DIFFY from err loop DrawYPX ; Loop until done DoneDYPX: or byte ptr [di],ah ; Plot last jmp short LeaveLine ; Jump to exit code LineXYP: mov cx,bx ; Load count mov si,cx ; Initialize error neg si ; sar si,1 ; or bp,bp ; Are we drawing? mov bp,8192 ; Set up for changes in Y jne DrawXYP ; Jump if yes ; ************************************* ; Loop: Erase, increment X, and increment Y if appropriate. ; ************************************* EraseXYP: and al,ah ; Erase ror ah,1 ; Rotate mask right jnc GetNextEraseXYP ; Jump if we need another byte ContinueEraseXYP: add si,dx ; Add DIFFY to err jns ELoopXYP ; Jump if positive loop EraseXYP ; Loop until done jmp short DoneEXYP ; Jump to end GetNextEraseXYP: stosb ; Store and increment DI mov al,[di] ; Get next byte jmp short ContinueEraseXYP ELoopXYP: mov [di],al ; Save to video memory IncY ; Increment Y mov al,[di] ; Load from video memory sub si,bx ; Add DIFFX to err loop EraseXYP ; Loop until done DoneEXYP: and al,ah ; Erase last jmp short WriteLastByte ; ************************************* ; Loop: Draw, increment X, and increment Y if appropriate. ; ************************************* DrawXYP: or al,ah ; Plot ror ah,1 ; Rotate mask right jc GetNextDrawXYP ; Jump if we need another byte DrawContinueXYP: add si,dx ; Add DIFFY to err jns DLoopXYP ; Jump if positive loop DrawXYP ; Loop until done jmp short DoneDXYP ; Jump if done GetNextDrawXYP: stosb ; Store byte and increment mov al,[di] ; Get next byte jmp short DrawContinueXYP DLoopXYP: mov [di],al ; Save to video memory IncY ; Increment Y mov al,[di] ; Load from video memory sub si,bx ; Subtract DIFFX from err loop DrawXYP ; Loop until done DoneDXYP: or al,ah ; Plot last WriteLastByte: ; Write the last byte before exiting mov [di],al ; Save final byte LeaveLine: pop si ; Restore registers pop di ; pop ds ; pop bp ; Restore stack frame ret ; Exit routine Banks DW 0,8192,16384,24576 _hercline ENDP ; hercspan called from _hercline if line is horizontal. ; Input register states as follows: ; DS,ES 0B000H ; BX DIFFX ; DX 0 (DIFFY) ; BP 0 if erasing, nonzero if drawing ; AL initial value ; AH initial mask hercspan PROC mov cx,bx ; Get count into CX or bp,bp ; Are we drawing? jnz DrawFirstLoop ; Yes not ah ; AH <- ~AH EraseFirstLoop: and al,ah ; Write pixel dec cx ; Decrement CX ror ah,1 ; Rotate mask right jnc DoneEraseFirstLoop jcxz DoneEraseFirstLoop jmp short EraseFirstLoop DoneEraseFirstLoop: stosb ; Store byte mov dx,cx ; Copy count remaining shr cx,1 ; Divide by 8 shr cx,1 ; shr cx,1 ; sub dx,cx ; Find remainder xor al,al ; Write 0's rep stosb ; mov cx,dx ; Copy remainder to CX jcxz LeaveSpan ; Leave if done mov al,[di] ; mov ah,7fh ; Set mask EraseSecondLoop: and al,ah ; Write pixel ror ah,1 ; Rotate mask right loop EraseSecondLoop ; stosb ; Store byte jmp short LeaveSpan ; Leave DrawFirstLoop: or al,ah ; Write pixel dec cx ; Decrement CX ror ah,1 ; Rotate mask right jc DoneDrawFirstLoop jcxz DoneDrawFirstLoop jmp short DrawFirstLoop DoneDrawFirstLoop: stosb ; Store byte mov dx,cx ; Copy count remaining shr cx,1 ; Divide by 8 shr cx,1 ; shr cx,1 ; sub dx,cx ; Find remainder mov al,0FFh ; Write FF's rep stosb ; mov cx,dx ; Copy remainder to CX jcxz LeaveSpan ; Leave if done mov al,[di] ; mov ah,80h ; Set mask DrawSecondLoop: or al,ah ; Write pixel ror ah,1 ; Rotate mask right loop DrawSecondLoop ; stosb ; Store byte LeaveSpan: ret hercspan ENDP END