; PROGRAM VPRINT version 1.0 ; by Dave Whitman ; ; Redirects printer output to a specified disk file, ; providing a virtual printer. Invoked from DOS by ; the command: VPRINT filespec ; ; Changes vector to BIOS printer routine to point ; to VPRINT code. The VPRINT code is grafted onto ; DOS, and will not be overwritten by other programs. ; fcb equ [5CH] ;file control block name equ [5DH] ;name field of fcb name_length equ 11 ;length of name field in fcb cur_block equ [68H] ;current block field current_rec equ [7CH] ;current record field record_size equ [6AH] ;record size field dta_length equ 200H ;length of internal disk buffer param_count equ [80H] ;contains # of chars in param area param_area equ [81H] ;PSP unformated param area dummy_dta equ [80H] ;leave dta set here on return cr equ 0DH ;ascii carriage return lf equ 0AH ;ascii line feed vector_offset equ [005CH] ;offset part of interrupt vector 17H vector_segment equ [005EH] ;segment part of interrupt vector 17H printer_io equ EFD2H ;offset of BIOS routine ; jmp init ;branch around redirection code ; ;------------------------------------------------------ ; This section of code will be grafted onto DOS. ; Calls to PRINTER_IO are redirected here, where ; they are converted to DOS sequential file writes. ; convert sti ;enable interupts or ah,ah ;request to print char? jnz abort ;abort if not ; push dx ;save state push ds push cs pop ds ;and establish addr. mov char,al ;save the char ; cmp al,lf ;is this a line feed? je exit ;exit if so ; call printchar ;print the charactor cmp al,cr ;was that a carriage return? jne exit ;exit if not mov al,lf ;otherwise generate a line feed call printchar ;and send it ; exit mov al,char ;restore state pop ds pop dx ; ;========================================================= ; We have to return a status byte in AH. The way I read ; Tech. Ref., to signal all ok we should send value 50H. ; However, a long DEBUG session showed that Easywriter 1.1 ; expects to get 90H as the OK value. I would interpret this ; as "printer busy", but we'll humor Easywriter. ;========================================================= ; abort mov ah,90H ;move status = ok to AH iret ;and return ; printchar proc near push di mov di,numchars ;position in buffer for char mov offset(dta)[di],al ;mov char into buffer ; inc di ;update number of chars mov numchars,di ;and save it ; cmp di,dta_length ;is the buffer full? jne pc-exit ;exit if not call dumpdta ;otherwise dump it ; pc-exit pop di ret endp ; dumpdta proc near push ax ;save state push dx ; mov ah,0FH ;open file mov dx,offset(fcb) int 21H ; movw record_size,dta_length ;set record size mov ax,block_save ;set fcb current block mov cur_block,ax ; mov dx,offset(dta) ;set disk transfer addr. mov ah,1AH int 21H ; mov dx, offset(fcb) ;write buffer to disk mov ah,15H int 21H ; mov ax, cur_block ;save current block mov block_save,ax ; mov ax,1000H ;close file mov dx,offset(fcb) int 21H ; movw numchars,0000H ;buffer is now empty ; ;====================================================== ; Since we don't know where the DTA was set upon entry, ; we can't really restore the state of the machine. ; What we'll do is set up a dummy DTA for the caller to ; use, so it doesn't clobber our buffered data between calls. ; This is *NOT* foolproof, but seems to work OK with Easywriter. ;====================================================== ; mov dx,offset(dummy_dta) ;set DTA to dummy block mov ah,1AH int 21H pop dx ;restore state pop ax ret ;and return endp ; ;==================================================== ; Data area for resident section ;==================================================== char db 00H ;to save the char. passed numchars db 00H,00H ;word: # of chars in buffer block_save db 00H,00H ;to save current block between calls dta ds dta_length ;internal data buffer ; ;=================================================== ; Initialization section. Does not become resident. ;=================================================== init cmpb name,' ' ;was a file specified? jnz a1 ;skip if so cmpb param_count,00H ;any param chars? jz default ;skip if not xor ch,ch ;set up for scan mov cl,param_count mov di,offset(param_area) mov al,'/' ;look for '/' repnz ;scan to end or 1st match scasb ; jnz default ;skip if not found xorb [di],20H ;guarantees upper case ; cmpb [di],'N' ;is it an N? je p_handler ;if so, jump ; ;if no parameters decoded, just fall through ;and set up print file with default name ; default mov si, offset(default_file_name) mov di, offset(name) mov cx, name_length rep movsb ; a1 mov dx, offset(fcb) ;check if file exists mov ah,11H int 21H ; test al,al ;file found? jnz a2 ;skip if not ; mov dx, offset(err_msg_1) ;otherwise print mov ah,09H ;error message int 21H int 20H ;and return to DOS ; a2 mov ah,16H ;create file int 21H ; test al,al ;file created? jz a3 ;skip if so mov dx, offset(err_msg_2) ;otherwise error mov ah, 09H int 21H int 20H ; a3 movw current_rec, 0 ;fill in fcb ; mov ah,10H ;close file mov dx, offset(fcb) int 21H ; mov ax,2517H ;reset printer vector mov dx, offset(convert) int 21H ; mov dx,offset(init) ;point dx past resident code int 27H ;end but stay resident ;=================================================================== p_handler ; mov ax,0000H ;ext. addr. for vector mov ds,ax ; cmpw vector_offset,printer_io ;already in BIOS? je p_exit ;exit if so ; mov ds,vector_segment ;est. addr. in original vprint seg call dumpdta ;operates on buffer in original vprint ; mov ax,F000H ;reset vector 17H to BIOS routine mov ds,ax ;bios segment mov dx,printer_io ;printer support routine mov ax,2517H int 21H ; p_exit int 20H ;return to DOS ; ;=================================================================== err_msg_1 db 'File already exists!$' err_msg_2 db 'No room for file in directory.$' default_file_name db 'VIRTUAL PRN'