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Assembly Source File | 1998-01-14 | 7.7 KB | 230 lines

TITLE scrn2.asm ; AUTHOR Tim Spencer - Compuserve [73657,1400] ; DATE March 15, 1987 _TEXT SEGMENT BYTE PUBLIC 'CODE' _TEXT ENDS _DATA SEGMENT WORD PUBLIC 'DATA' SCRN STRUC ; screen data structure - defined in video.h off dw 0 ; offset (cursor position) seg dw 0 ; screen buffer address port dw 0 ; status port address attrib dw 0 ; attribute to use cgacrd dw 0 ; retrace checking enabled if not zero SCRN ENDS _DATA ENDS DGROUP GROUP _DATA ASSUME CS:_TEXT, DS:DGROUP, SS:DGROUP, ES:NOTHING _TEXT SEGMENT BYTE PUBLIC 'CODE' ;-----------------------------------------------------------------------; ; scrn_puts - MSC callable routine for printing a string directly to ; ; the screen buffer. ; ; ; ; Usage: scrn_puts(string, attribute, &structure_name); ; ;-----------------------------------------------------------------------; _DATA SEGMENT scrn_puts_args STRUC ; args as pushed by calling program dw 0 ; saved bp value dw 0 ; return address str_ptr dw 0 ; address of string sstruc dw 0 ; pointer to SCRN structure scrn_puts_args ENDS _DATA ENDS PUBLIC _scrn_puts _scrn_puts PROC NEAR push bp ;set up frame pointer mov bp,sp push di push si mov si,[bp].str_ptr ; get the string pointer mov bx,[bp].sstruc ; get pointer to SCRN structure les di,dword ptr[bx].off ; put offset in di, buffer addr in es mov ch,byte ptr[bx].attrib ; put attribute in cx mov dx,[bx].port ; get status port address load_one: lodsb ; load a char and advance str ptr or al,al ; is it null ? jz puts_exit ; yes, lovely chatting. Chow babe. mov cl,al ; no, save in cl for a few millisecs cmp [bx].cgacrd, 0 ; cga card present? jnz swait1 ; yes...go wait mov ax,cx ; no. stosw ; write it jmp short load_one ; as fast as you can! swait1: in al, dx ; wait for end of retrace shr al, 1 ; test horizontal trace bit jc swait1 ; loop if still tracing cli ; disable writus interuptus swait2: in al, dx ; now wait until the very moment shr al, 1 ; when the next retrace begins jnc swait2 ; still waiting... mov al,cl ; load the char into al for stosb stosb ; write it and update pointer sti ; enable interrupts again swait3: in al, dx ; repeat these steps for the attribute shr al, 1 jc swait3 cli swait4: in al, dx shr al, 1 jnc swait4 mov al,ch ; load the attribute stosb sti jmp short load_one ; and get another puts_exit: mov [bx].off,di ; save new offset ( cur pos ) pop si pop di pop bp ret _scrn_puts ENDP ;-----------------------------------------------------------------------; ; scrn_putca - MSC callable function to print a char and attribute ; ; directly to the screen buffer. The logical cursor ; ; position IS UPDATED on return. ; ; ; ; Usage: scrn_putca(char, attribute, &structure_name ; ;-----------------------------------------------------------------------; _DATA SEGMENT scrn_putca_args STRUC ; args as pushed by calling program dw 0 ; saved bp value dw 0 ; return address pchar dw 0 ; char to write pstruc dw 0 ; pointer to SCRN structure scrn_putca_args ENDS _DATA ENDS PUBLIC _scrn_putca _scrn_putca PROC NEAR push bp ; set up frame pointer mov bp,sp push di mov bx,[bp].pstruc ; get pointer to SCRN structure les di,dword ptr[bx].off ; get offset in di, buffer addr in es mov dx,[bx].port ; status port address mov ch,byte ptr[bx].attrib ; get attribute into ch mov cl,byte ptr[bp].pchar ; and char into cl cmp [bx].cgacrd, 0 ; cga card present? jnz cwait1 ; yes...go wait mov ax,cx ; no. stosw ; write it jmp short cexit ; exit. cwait1: in al, dx ; wait for end of retrace shr al, 1 ; test horizontal trace bit jc cwait1 ; loop if still tracing cli ; disable writus interuptus cwait2: in al, dx ; now wait until the very moment shr al, 1 ; when the next retrace begins jnc cwait2 ; still waiting... mov al,cl ; load the char into al for stosb stosb ; write it and update pointer sti ; enable interrupts again cwait3: in al, dx ; repeat these steps for the attribute shr al, 1 jc cwait3 cli cwait4: in al, dx shr al, 1 jnc cwait4 mov al,ch ; load the attribute stosb sti ; whew...all done...enable interrupts cexit: mov [bx].off, di ; update logical cursor position pop di ; (offset) before leaving pop bp ret _scrn_putca ENDP ;-----------------------------------------------------------------------; ; _scrn_getca - get char and attrib from screen ; ; ; ; usage: char = scrn_getca(&attrib,p_scn_data) ; ; ; ;-----------------------------------------------------------------------; _DATA SEGMENT getca_args STRUC ; input arguments dw 0 ; saved BP value dw 0 ; return address gattrib dw 0 ; store attribute here gstruct dw 0 ; pointer to SCRN getca_args ENDS _DATA ENDS PUBLIC _scrn_getca _scrn_getca PROC NEAR push bp ; set up frame pointer mov bp,sp push si mov bx,[bp].gstruct ; get pointer to SCRN structure mov dx,[bx].port ; get status port address push ds ; lds uses ds - must save lds si,dword ptr[bx].off ; get offset and segment address gwait1: in al, dx ; wait for end of retrace shr al, 1 ; test horizontal trace bit jc gwait1 ; loop if still tracing cli ; disable writus interuptus gwait2: in al, dx ; now wait until the very moment shr al, 1 ; when the next retrace begins jnc gwait2 ; still waiting... lodsb ; get the char into al sti ; enable interrupts again mov cl,al ; save the char in cl gwait3: in al, dx ; repeat these steps for the attribute shr al, 1 jc gwait3 cli gwait4: in al, dx shr al, 1 jnc gwait4 lodsb ; get the attribute in al sti pop ds ; restore data segment to norm mov word ptr [bx],si ; update offset (logical cursor) mov si,word ptr[bp].gattrib ; get address to store attrib mov byte ptr [si],al ; store the attribute at "&attrib" mov al,cl ; move the char to al and xor ah,ah ; zero out ah so that ax = char, ; the return value pop si pop bp ret _scrn_getca ENDP _TEXT ENDS END