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Assembly Source File | 1987-07-31 | 10.9 KB | 434 lines

PAGE 60,132 .MODEL small .DATA EXTRN statatr:BYTE,scrnatr:BYTE,sbuffer:WORD,pbuffer:WORD EXTRN fsize:WORD,cell:WORD,statline:BYTE,linenum:WORD EXTRN rows:WORD,vidadr:WORD,cga:BYTE .CODE PUBLIC Pager,isEGA ; Procedure Pager ; Purpose Displays status and text lines ; Input Stack variable: lines to scroll (negative up, positive down) ; Global variables: "sbuffer", "pbuffer", "linenum" ; Output To screen Pager PROC push bp mov bp,sp mov es,sbuffer ; Initialize buffer position mov di,pbuffer mov cx,[bp+4] ; Get count argument mov ax,10 ; Search for linefeed or cx,cx ; Argument 0? jg forward ; If above, forward jl backward ; If below, backward jmp SHORT show ; If equal, done backward: call GoBack ; Adjust backward jmp SHORT show ; Show screen forward: call GoForwd ; Adjust forward ; Write line number to status line show: cld ; Go forward push di push es push ds ; Load DS to ES pop es ; BinToStr (linenum,OFFSET statline[7]) push linenum ; Arg 1 mov ax,OFFSET statline[7] push ax ; Arg 2 call BinToStr ; Convert to string ; Fill in status line mov cx,7 ; Seven spaces to fill sub cx,ax ; Subtract those already done mov al," " ; Fill with space rep stosb pop es mov bl,statatr ; Load status attribute mov BYTE PTR cell[1],bl ; CellWrt (DS,OFFSET statline,0,cell) push ds ; Arg 1 mov ax,OFFSET statline ; Arg 2 push ax sub ax,ax ; Arg 3 push ax push cell ; Arg 4 call CellWrt ; Write status line pop di mov bl,scrnatr ; Load screen attribute mov BYTE PTR cell[1],bl mov si,di ; Update position mov cx,rows ; Lines per screen show1: mov bx,rows ; Lines of text inc bx ; Adjust for 0 sub bx,cx ; Calculate current row push cx ; Save line number ; CellWrt (sbuffer,position,line,cell) push sbuffer ; Arg 1 push si ; Arg 2 push bx ; Arg 3 push cell ; Arg 4 call cellwrt ; Write line push ss ; Restore DS from SS pop ds pop cx ; Restore line number mov si,ax ; Get returned position cmp ax,fsize ; Beyond end of file? jae fillout ; Yes? Fill screen with spaces loop show1 ; else next line jmp SHORT pagedone ; Get out if done ; Fill the rest with spaces fillout: dec cx ; Adjust jcxz pagedone mov al,80 ; Columns times remaining lines mul cl ; CellFil (sbuffer,count,cell) push sbuffer ; Arg 1 push ax ; Arg 2 push cell ; Arg 3 call CellFil ; Fill screen with spaces push ss ; Restore DS from SS pop ds pagedone: pop bp ret 2 Pager ENDP ; Procedure CellWrt (segment,offset,line,cell) ; Purpose Writes a line to screen buffer ; Input Stack variables: 1 - segment of line ; 2 - offset ; 3 - line number ; 4 - attribute ; Output Line to screen buffer CellWrt PROC push bp mov bp,sp sub dx,dx ; Clear as flag for scan cmp cga,1 ; CGA? jne noscan mov dx,03DAh ; Load port # noscan: mov es,vidadr ; Load screen buffer segment mov ds,[bp+10] ; Buffer segment mov si,[bp+8] ; Buffer position mov cx,80 ; Cells per row mov ax,[bp+6] ; Starting row mov bx,80*2 ; Bytes per row mul bl ; Figure columns per row mov di,ax ; Load as destination mov bx,di ; Save start for tab calculation mov ax,[bp+4] ; Attribute movechar: lodsb ; Get character cmp al,13 ; CR? je fillspc cmp al,9 ; Tab? jne notab call filltab ; Yes? fill with spaces jcxz nextline ; If beyond limit done jmp SHORT movechar notab: or dx,dx ; CGA? je notab2 call Retrace ; Yes? Write during retrace loop movechar jmp SHORT nextline notab2: stosw ; Write loop movechar jmp SHORT nextline ; Done fillspc: mov al," " ; Fill with space or dx,dx ; CGA? je space2 space1: call Retrace ; Yes? Write during retrace loop space1 inc si ; Adjust jmp SHORT exit ; Done space2: rep stosw ; Write inc si ; Adjust for LF jmp SHORT exit ; Done nextline: mov ah,10 ; Search for next line feed chklf: lodsb ; Load and compare cmp al,ah loopne chklf exit: mov ax,si ; Return position pop bp ret 8 CellWrt ENDP ; Procedure CellFil (segment,count,cell) ; Purpose Fills screen with character ; Input Stack variables: 1 - segment of text (offset 0) ; 2 - number of characters ; 3 - attribute and character ; Output Characters to screen buffer CellFil PROC push bp mov bp,sp sub dx,dx ; Clear as flag for scan cmp cga,1 ; CGA? jne noscan2 mov dx,03DAh ; Load port # noscan2: mov es,vidadr ; Load screen buffer segment mov ds,[bp+8] ; Buffer segment (position 0) mov cx,[bp+6] ; Characters to fill mov ax,[bp+4] ; Attribute or dx,dx ; CGA? je fillem2 fillem1: call Retrace ; Yes? Write during retrace loop fillem1 jmp SHORT filled ; Done fillem2: rep stosw ; Write filled: pop bp ret 6 CellFil ENDP ; Procedure FillTab ; Purpose Writes spaces for tab to screen ; Input BX points to start of line, DI points to current position ; Output Spaces to screen buffer FillTab PROC push bx push cx sub bx,di ; Get current position in line neg bx shr bx,1 ; Divide by 2 bytes per character mov cx,8 ; Default count 8 and bx,7 ; Get modulus sub cx,bx ; Subtract mov bx,cx ; Save modulus mov al," " ; Spaces or dx,dx ; CGA? je tabem2 tabem1: call Retrace ; Yes? Write during retrace loop tabem1 jmp SHORT tabbed tabem2: rep stosw ; Write tabbed: pop cx sub cx,bx ; Adjust count jns nomore ; Make negative count 0 sub cx,cx nomore: pop bx ret FillTab ENDP ; Procedure GoBack ; Purpose Searches backward through buffer ; Input CX has number of lines; ES:DI has buffer position ; Output Updates "linenum" and "pbuffer" GoBack PROC std ; Go backward neg cx ; Make count positive mov dx,cx ; Save a copy inc cx ; One extra to go up one or di,di ; Start of file? je exback ; If so, ignore findb: push cx ; else save count mov cx,0FFh ; Load maximum character count cmp cx,di ; Near start of buffer? jl notnear ; No? Continue mov cx,di ; else search only to start notnear: repne scasb ; Find last previous LF jcxz atstart ; If not found, must be at start pop cx loop findb cmp linenum,0FFFFh ; End of file flag? jne notend ; No? Continue add di,2 ; Adjust for cr/lf mov pbuffer,di ; Save position call EndCount ; Count back to get line number ret notend: sub linenum,dx ; Calculate line number jg positive mov linenum,1 ; Set to 1 if negative positive: add di,2 ; Adjust for cr/lf mov pbuffer,di ; Save position ret atstart: pop cx sub di,di ; Load start of file mov linenum,1 ; Line 1 mov pbuffer,di ; Save position exback: ret GoBack ENDP ; Procedure GoForwd ; Purpose Searches forward through a buffer ; Input CX has number of lines; ES:DI has buffer position ; Output Updates "linenum" and "pbuffer" GoForwd PROC cld ; Go forward mov dx,cx ; Copy count findf: push cx ; Save count mov cx,0FFh ; Load maximum character count repne scasb ; Find next LF jcxz atend ; If not found, must be at end cmp di,fsize ; Beyond end? jae atend pop cx loop findf add linenum,dx ; Calulate line number mov pbuffer,di ; Save position ret atend: pop cx mov di,pbuffer ; Restore position ret GoForwd ENDP ; Procedure EndCount ; Purpose Counts backward to count lines in file ; Input ES:DI has buffer position ; Output Modifies "linenum" EndCount PROC push di mov al,13 ; Search for CR mov linenum,0 ; Initialize findstrt: inc linenum ; Adjust count mov cx,0FFh ; Load maximum character count cmp cx,di ; Near start of buffer? jl notnear2 ; No? Continue mov cx,di ; else search only to start notnear2: repne scasb ; Find last previous cr jcxz found ; If not found, must be at start jmp SHORT findstrt found: pop di ret EndCount ENDP ; Procedure isEGA ; Purpose Determines if an EGA is active ; Input None ; Output 0 if no; lines per screen if yes isEGA PROC push bp push es mov ah,12h ; Call EGA status function mov bl,10h sub cx,cx ; Clear status bits int 10h sub ax,ax ; Segment 0 and assume no EGA jcxz noega ; If status still clear, no EGA mov es,ax ; ES=0 test BYTE PTR es:[487h],1000b ; Test active bit jnz noega ; If set, not active mov ax,1130h ; Get EGA information int 10h mov al,dl ; Return lines per screen cbw noega: pop es pop bp ret isEGA ENDP ; Procedure BinToStr (number,address) ; Purpose Converts integer to string ; Input Stack arguments: 1 - Number to convert; 2 - Near address for write ; Output AX has characters written BinToStr PROC push bp mov bp,sp mov ax,[bp+6] ; Arg 1 mov di,[bp+4] ; Arg 2 sub cx,cx ; Clear counter mov bx,10 ; Divide by 10 ; Convert and save on stack backwards getdigit: sub dx,dx ; Clear top div bx ; Divide to get last digit as remainder add dl,"0" ; Convert to ASCII push dx ; Save on stack or ax,ax ; Quotient 0? loopnz getdigit ; No? Get another ; Take off the stack and store forward neg cx ; Negate and save count mov dx,cx putdigit: pop ax ; Get character stosb ; Store it loop putdigit mov ax,dx ; Return digit count pop bp ret 4 BinToStr ENDP ; Procedure Retrace ; Purpose Writes cell during horizontal retrace (CGA) ; Input ES:DI has screen buffer position, AX has cell ; Output Character to screen buffer Retrace PROC push bx mov bx,ax ; Save character lscan2: in al,dx ; Look in the port shr al,1 ; until it goes low jc lscan2 cli hscan2: in al,dx ; Look in the port shr al,1 ; until it goes high jnc hscan2 mov ax,bx ; Restore and write it stosw sti pop bx ret Retrace ENDP END