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Assembly Source File | 1993-05-10 | 49.8 KB | 1,052 lines

; ; Program FView ( Chapter 8 ) ; page 55,132 ;********************************************************************** ; ; The file browsing program. Version 3.3 ; Last update: 16/04/93 10:49 ; ; Author: A.I.Sopin, VSU, Voronezh, Russia ; ; Usage: FVIEW [path]filename ; ; Keys used: ; ; "PgDn" - scroll by one screen down ; ; "PgUp" - scroll by one screen up ; ; "Home" - first screen ; ; "End" - last screen ; ; "" - scroll by one line down ; ; "" - scroll by one line up ; ; "->" - scroll by one position to the right ; ; "<-" - scroll by one position to the left ; ; "Ctrl" + "Home" - to the beginning of the line ; ; "Esc" - finish working and return to MS-DOS ; ; 23 lines of file are shown on the screen ; ; The MS-DOS disk service (Interrupt 21h) is used ; ;********************************************************************** NAME FVIEW ;********************************************************** ; MACRO Definitions ;********************************************************** SetCurs MACRO Row,Column mov ah,2 ; function 02h - set cursor xor bh,bh ; video page 0 mov dh,&Row ; ROW mov dl,&Column ; COLUMN int 10h ; BIOS video service ENDM ; Clear screen and set color SetCol MACRO Row,Column,Leng,Attrib mov al,&Column ; initial position for output SetCurs Row,al ; mov al," " ; AL - character for output mov bl,&Attrib ; BL - attribute mov ah,9 ; output character and attribute xor bh,bh ; video page 0 is used mov cx,&Leng ; number of charcacters to be output int 10h ; BIOS video service ENDM ; Output string onto the screen OutStr MACRO String,Row,Column,Leng SetCurs &Row,&Column ; lea si,&String ; DS:SI - address of string for output mov cx,&Leng ; maximum length of string Call PUTSTR ; output string SetCurs 25,80 ; ENDM ;----------------------------------------------------------------------- STAC SEGMENT STACK DW 16 dup (?) LSTAC EQU $ STAC ENDS ;----------------------------------------------------------------------- DATA SEGMENT PARA PUBLIC 'DATA' ES0 DW 0 ; segment address for PSP ; Characteristic of the block read AMEM LABEL DWORD ; offset + segment address for LDS OFFMEM DW 0 ; buffer start addres (offset) SEGMEM DW 0 ; segment address of memory received SEGSTR DW 0 ; segment address of buffers string HANDLE DW 0 ; handle value for file to be processed DX0 DW 0 ; high part of file length AX0 DW 0 ; low part of file length CXL DW 0 ; offset of last block from file start (high) DXL DW 0 ; offset of last block from file start (low) CXF DW 0 ; offset of screen from file start (high) DXF DW 0 ; offset of screen from file start (low) ABLOK DW 0 ; address of current byte in filke Count DW 0 ; length of block read (rest) DXB DW 0 ; offset of screen beginning in file LENG0 DW 0 ; length of part of previous block ; on current screen LENGF DW 0 ; length of file part on screen NREC DW 0 ; number of records preceeding first shown ; Characteristics of screen buffer ASTR DW 0 ; address of character in string LMOV DW 0 ; length of string in buffer ABUF DW 0 ; address of beginning of string BUF0 NSTR DW 0 ; number of filled strings in buffer DRL0 DW 0 ; value of screen shift to the right ERROP DW 0 ; ERROP > 0 -Error on open ERR0 DW 0 ; error flag (for GetMem); error if not 0 VIDSEG DW 0 ; segment address of video buffer CGA DB 0 ; CGA indicator, is 1 when CGA active NB DB 1 ; number of blocks on screen (1 or 2) EOD DB 0 ; EOD = 1 -EndOfFile indicator W label byte KbdASCII DB 0 KbdScan DB 0 VMODE DB 0 ; Original video mode ; Texts of information lines on screen and error messages STR1 DB " PATH: " PATH DB 64 dup (0) STR25 DB " Use Keys: PgDn, PgUp, Home, End, " DB 24, 44, 32, 25, 44, 32, 26, 44, 32, 27, 44 DB " Ctrl+Home, Esc -Exit", 0 ERR00 DB ' Not enough memory !!! (press Enter) ',0 ERR01 DB ' File not found !!! (press Enter) ',0 ERR02 DB ' Data error !!! (Press Enter) ',0 DATA ENDS ;----------------------------------------------------------------------- _TEXT SEGMENT PARA PUBLIC 'CODE' ASSUME CS:_TEXT, DS:DATA, SS:STAC ;------------------------------------------------------------------- START: mov bx,DS ; PSP segment address mov ax,DATA ; data segment basing mov ds,ax ; DS points to DATA segment mov ax,STAC ; address of STACK segment mov SS,ax ; switch to internal satck mov SP,word ptr LSTAC ; stack size in bytes mov ES0,bx ; PSP segment address ; Determining and save the current video mode mov ah,0Fh ; function 0Fh - get video mode int 10h ; BIOS video service call mov VMODE,al ; save current video mode ; Free memory above the program end mov SEGMEM,0 ; no memory has been allocated mov bx,ZSEG ; program end address mov ax,es ; segment address of the program beginning sub bx,ax ; memory size needed mov ah,4Ah ; DOS function number int 21h ; free memory mov ERR0,ax ; Error Code jnc GetMem ; Memory reallocated! lea dx,ERR00 ; address of error message jmp TypErr ; Allocate the maximum memory area for the buffer GetMem: mov bx,0FFFh ; request memory area of the maximum size mov ah,48h ; DOS function number int 21h ; DOS service call jnc Norm ; jump if successful int 21h ; BX = size of largest available block! jnc Norm ; jump if memory allocated lea dx,ERR00 ; address of error message jmp TypErr ; otherwise output error message ;------------------------------------------------------------------- Norm: mov SEGMEM,ax ; AX:0 -segment address of allocated xor ah,ah ; function 0 - set video mode mov al,03 ; 80x25 Text int 10h ; BIOS video service call ; Parsing the file name in command line mov ERROP,1 ; Error on Open mov es,ES0 ; PSP segment address mov si,81h ; address of command line tail xor ch,ch ; clear high part mov cl,ES:[80h] ; CX - length of command string and cx,cx ; no parameters? jnz GetPath ; parameters specified jmp ErrMsg ; output error message ;------------------------------------------------------------------- ; Skip blanks before file name GetPath:cmp byte ptr ES:[si]," " ; blank? ja M1 ; no, take character inc si ; to next character loop GetPath ; repeat cycle jmp ErrMsg ; Put Error Message ; Checking wheter the root directory or disk letter specified M1: lea di,PATH ; target for full file name cmp word ptr ES:[si]+1,"\:" ; root directory? je M7 ; full path specified! cmp byte ptr ES:[si]+1,":" ; disk letter specified? jne M2 ; create full path ; Pass drive letter and determine current directory on that drive mov dl,ES:[si] ; drive letter from command line and dl,0DFh ; uppercase mov PATH,dl ; put drive letter sub dl,40h ; 0 - current, 1 -A .... add si,2 ; address of file name in command line sub cx,2 ; length of command line tail jmp short M3 ; put current directory and file name ; Create full path (drive letter and direxctory name) M2: mov ah,19h ; Get default Disk Number int 21h ; DOS service call add al,41h ; drive letter mov PATH,al ; store drive letter xor dl,dl ; DL = 0 - default drive ; Determining the current directory M3: mov word ptr PATH+1,'\:' ; push si ; address of file name in command line lea si,PATH+3 ; DS:SI point to path string mov ah,47h ; Get Current Directory int 21h ; DOS service call push cx ; length of name in command line mov cx,64 ; max ength of name ; Determining end of the directory name read M4: cmp byte ptr DS:[si]," " ; end of name(ASCIIZ) ? jna M5 ; inc si ; to next character loop M4 ; ; Insert "\" before file name M5: cmp byte ptr DS:[si]-1,"\" ; backslash already present? je M6 ; yes, do nothing mov byte ptr DS:[si],"\" ; put "\" before file name inc si ; address of file name in PATH M6: mov di,si ; destination pop cx ; length of command line tail pop si ; source (address of command line tail) ; Copy filke name from command line M7: mov ds,ES0 ; PSP segment address mov ax,DATA ; data segment mov es,ax ; ES points to data segment cld ; rigth direction rep movsb ; copy file name from command line mov byte ptr ES:[di],0 ; 0 at end of string ;----------------------------------------------------------------------- ; Open the file required for reading Open: mov ax,DATA ; address of data segment mov ds,ax ; DS points to data segment xor al,al ; Read File lea dx,PATH ; DS:DX - address of path string mov ah,3Dh ; Function 3Dh - Open File int 21h ; DOS service call jnc Fsize ; O'K ! ; Output message "File not found" and exit ErrMsg: mov ax,DATA ; data segment basing mov ds,ax ; lea dx,ERR01 ; address of error message jmp TypErr ; otherwise output error message ; Determining length of file FSize: mov HANDLE,ax ; store value of file handle mov ERROP,0 ; Sucsesful Open mov bx,HANDLE ; mov ax,4202h ; AL = 2 - position to the end of file xor cx,cx ; high part of offset xor dx,dx ; low part of offset int 21h ; DOS service call mov AX0,ax ; low part of file length mov DX0,dx ; high part of file length ; Position for readinfg from the beginning of the file mov bx,HANDLE ; mov ax,4200h ; AL =0 - count from file beginning xor cx,cx ; high part of offset xor dx,dx ; low part of offset int 21h ; DOS service call ; Determining an offset of the last block from the biginning of the file mov cx,32768 ; divisor and multiplier mov ax,AX0 ; mov dx,DX0 ; div cx ; AX - result, DX - remainder xor dx,dx ; clear high part mul cx ; AX - low part, DX - high part mov CXL,dx ; high part of offset mov DXL,ax ; low part of offset mov DRL0,0 ; clear shift counter ;----------------------------------------------------------------------- ; Define screen attributes and output information strings CLRSCR: Call VIDTYP ; determine video adapter type SetCol 0,0,80,30h ; clear line 1 SetCol 1,0,80*23,1Bh ; clear lines 2-24 SetCol 24,0,80,30h ; clear line 25 OutStr STR1,0,0,80 ; output first line (file name) OutStr STR25,24,0,80 ; output last line (Help) ; Preparing parameters for passing file into video buffer INIT0: mov CXF,0 ; high part (screen beginning) mov DXF,0 ; low part (screen end) INIT1: mov NSTR,23 ; maximum number of screen lines mov ABUF,160 ; address of first byte of screen buffer mov ASTR,0 ; address of beginning of buffer string mov LMOV,0 ; length of buffer string created mov KbdScan,0 ; clear value of SCAN code read mov ax,SEGMEM ; add ax,800h ; number of paragraphs in file block mov SEGSTR,ax ; new segment address ;----------------------------------------------------------------------- ; ; Read the records of the input file (32768 bytes) ; ;----------------------------------------------------------------------- READ: Call RDBLOK ; read block of file (up 32768 bytes jnc EOF1 ; End of file? lea dx,ERR02 ; yes - error 2 (data error) jmp TypErr ; output error message ; Check number of blocks on screen EOF1: mov NB,1 ; one block on screen cmp KbdScan,50h ; SCAN -code ? jne M8 ; ordinar processing cmp NSTR,23 ; second record (screen beginning) ? je M9 ; check for screen beginning jl M10 ; not screen beginning - two blocks mov DXB,0 ; if record is skipped, DXB = 0 jmp M11 ; one block on screen !!! ; If one block and screen beginning, DXB=0 M8: cmp ABUF,160 ; screen beginning ? jne M10 ; no !!! M9: cmp ASTR,0 ; beginning of first line? jnz M10 ; no, this isn't screen beginning !!! mov DXB,0 ; offset of screen beginning in block jmp M11 ; M10: mov NB,2 ; two blocks on screen cmp Count,0 ; no bytes have been read? jnz PUTSCR ; mov NB,1 ; one block on screen !!! ; If end of file, EOD =1 M11: cmp Count,0 ; no bytes have been read? jnz PUTSCR ; mov EOD,1 ; set EndOfFile indicator jmp Next ; yes, end of file ;----------------------------------------------------------------------- ; ; Analyse the block read and create the buffer string ; ;----------------------------------------------------------------------- PUTSCR: cmp KbdScan,50h ; SCAN -code ? jne PUT1 ; ordinar processing cmp NSTR,23 ; second record (screen beginning) ? jne CHAR ; ordinar processing cmp ASTR,0 ; line beginning ? jnz CHAR ; no jmp short PUT2 ; set characteristics of screen beginning PUT1: cmp ABUF,160 ; screen beginning ? jne CHAR ; no cmp ASTR,0 ; beginning of first line ? jnz CHAR ; no PUT2: mov ax,Count ; rest of block read mov LENG0,ax ; rest of previopus block on screen mov LENGF,0 ; length of file part for screen ; Take and process the current byte from the file (BX) CHAR: mov es,SEGMEM ; ES -segment address of block read mov di,ABLOK ; source address (offset) mov bx,ES:[DI] ; BL - number of current block read inc ABLOK ; number of next block dec Count ; length of rest of buffer mov es,SEGSTR ; segment address of string buffer cmp KbdScan,50h ; SCAN -code ? jne M12 ; ordinary processing ; Correction of file parameters for "" operation cmp NSTR,1 ; last line ? je M12 ; ordinary processing fur passing into buffer cmp NSTR,24 ; first line not to be sent? jne M13 ; ordinary processing inc DXB ; modify offset of first line add DXF,1 ; offset from file biginning adc CXF,0 ; high part of offset jmp short M14 ; while length of file extent = 0 ; Clear buffer string befor filling the buffer M12: cmp ASTR,0 ; line biginning? jnz M13 ; xor di,di ; ES:[0] -address of line bigiining mov cx,2000 ; Count of words mov ax," " ; Character is the Space cld ; Clear Direction Flag rep stosw ; Clear of Buffer ; Processing control characters (Tab, LF, CR) M13: inc LENGF ; length of file part on screen M14: cmp bl,09h ; Tab ? je HT0 ; cmp bl,0Ah ; Line Feed? je LF0 ; cmp bl,0Dh ; Carriage Return ? je CRR0 ; ; Send text to the buffer string mov di,ASTR ; ES:DI - address of byte in buffer string mov ES:[DI],bl ; byte read (except control characters) inc ASTR ; address of next byte in line inc LMOV ; modify length of screen line jmp Next ; check for line filled ;--- ; Processing of horizontal tabulation (Tab =09h) HT0: mov ax,ASTR ; position of the next character mov cl,3 ; number of shifts for dividing by 8 shr ax,cl ; inc ax ; next position mov cl,3 ; number of shifts for multiplying shl ax,cl ; address of next character mov LMOV,ax ; length of string-position of first char sub ax,ASTR ; shift character to emulate Tab add ASTR,ax ; new position of the character jmp Next ; check for line filled ;--- ; Processing of Line Feed character 0Ah LF0: jmp Next ; check for line filled ;--- ; Processing of Carriage Return character 0Dh CRR0: cmp KbdScan,50h ; SCAN -code ? jne CRR1 ; ordinar processing cmp NSTR,1 ; last line ? jne CRR3 ; don't pass into video buffer! CRR1: mov cx,LMOV ; length of line parsed sub cx,DRL0 ; length for passing (shifted) jg CRR2 ; xor bh,bh ; clear next character ; Pass the string parsed int the video buffer CRR2: mov di,ABUF ; target offset mov si,DRL0 ; take shift into account mov es,VIDSEG ; segment address of video buffer mov ds,SEGSTR ; segment address of buffer string mov cx,80 ; max length of string Call VIDEO ; plase string into video buffer ; Advance cycle parameters mov ax,DATA ; data segment basing mov ds,ax ; restore segment address add ABUF,160 ; address of new line ; Check for the presence of the LF character after CR in last line CRR3: mov LMOV,0 ; length of buffer string mov ASTR,0 ; address of buffer string beginning dec NSTR ; lines left in screen buffer cmp NSTR,23 ; don't pass thi8s line ? jne CRR4 ; ordinar processing ? ; Process next LF character for line not being passed cmp bh,0Ah ; Line Feed ? jne Next ; inc DXB ; modify offset of first line add DXF,1 ; offset from file beginning adc CXF,0 ; high part of offset jmp short CRR5 ; CRR4: cmp NSTR,0 ; all lines processed? jnz Next ; not last line cmp bh,0Ah ; Line Feed? jne Next ; CRR5: inc ABLOK ; address of next byte inc LENGF ; jump over LF character dec Count ; length of block's rest ;----------------------------------------------------------------------- ; Check whether the screen has been buffer villed Next: cmp NSTR,0 ; screen filled ? jz GETKEY ; yes, output cmp EOD,1 ; end of file ? je Next1 ; output full screen cmp Count,0 ; all block processed? jz JMP1 ; yes, read next block jmp PUTSCR ; continue to process current block JMP1: jmp READ ; read next block ; Clear the lower part of the last screen which isn't completely filled Next1: xor dx,dx ; high part of multiplier mov ax,80 ; multiplier mul NSTR ; AX - number of character mov cx,ax ; mov bx,24 ; maximum number of lines sub bx,NSTR ; BL - number of first line SetCol bl,0,cx,1Bh ; clear lower lines SetCurs 25,80 ; hide cursor ;----------------------------------------------------------------------- ; Clear the keyboard buffer and wait for key pressed GETKEY: mov ASTR,0 ; address of buffer string beginning mov LMOV,0 ; length of buffer string created mov NSTR,23 ; max number of lines on screen mov ABUF,160 ; address of first byte of video buffer cli ; disable interrupts xor ax,ax ; mov ES,ax ; ES points to BIOS data segment mov al,ES:[41Ah] ; address of keyboard buffer head mov ES:[41Ch],al ; clear buffer (tail ptr = head ptr) sti ; enable interrupts xor ah,ah ; function 0 - Get Key int 16h ; BIOS keyboard service mov KbdASCII,al ; store ASCII character read mov KbdScan,ah ; store SCAN code ;----------------------------------------------------------------------- ; ; Process the code of a key pressed (Esc -Exit) ; ;----------------------------------------------------------------------- Esc0: cmp KbdScan,1 ; SCAN -code Esc ? jne PgDn ; jmp Exit ; Return to MS-DOS ;----------------------------------------------------------------------- ; PgDn - show the next screen PgDn: cmp KbdScan,51h ; SCAN -code PgDn ? jne PgUp ; cmp EOD,1 ; end of file ? jne PgDn1 ; not, create next screen in buffer jmp GETKEY ; wait for next key stroke PgDn1: Call NEXTSCR ; display next screen jmp Next ; continue processing ;----------------------------------------------------------------------- ; PgUp - show the previous screen PgUp: cmp KbdScan,49h ; SCAN -code PgUp ? je PgUp1 ; jmp Home ; ; Form parameters and display the previous screen PgUp1: mov NREC,23 ; number of lines read backwards Call GOLOW ; back to one screen mov NB,1 ; one block on screen mov EOD,0 ; clear End IOf File indicator jmp PUTSCR ; output screen ;----------------------------------------------------------------------- ; Home - to the beginning of the file Home: cmp KbdScan,47h ; SCAN -code Home ? jne End$ ; mov bx,HANDLE ; value of file handle mov ax,4200h ; AL = 0 - read file from the beginning xor cx,cx ; high part of offset xor dx,dx ; low part of offset int 21h ; DOS service call jmp INIT0 ; to the file beginning ;----------------------------------------------------------------------- ; End - show the last screen End$: cmp KbdScan,4Fh ; SCAN -code End ? jne Right ; mov NB,1 ; one block on screen mov cx,CXL ; high part of offset mov dx,DXL ; low part of offset mov CXF,cx ; high part (screen beginning) mov DXF,dx ; low part (screen beginning) Call POSIT ; read block of file ; Output last lines of the last block mov EOD,0 ; clear EndOfFile indicator mov DI,ax ; DI - address of last byte + 1 mov ES,SEGMEM ; ES - segment address of block mov cx,23 ; number of lines on last screen Call BKREC ; find lines jnc End1 ; lines found! xor dx,dx ; accept address of block beginning ; Set up parameters for processing the last line End1: sub Count,dx ; length of rest of last block mov ABLOK,dx ; address of line for processing mov DXB,dx ; offset from block beginning add DXF,dx ; offset of last line (high) adc CXF,0 ; offset of last line (low) jmp PUTSCR ; output list line ;----------------------------------------------------------------------- ; ---> shift the screen to the right by one position Right: cmp KbdScan,4Dh ; SCAN -code ---> ? jne Left ; inc DRL0 ; increase right shift counter jmp Repeat0 ; repeat screen output ;----------------------------------------------------------------------- ; <--- shift the screen to the left by one position Left: cmp KbdScan,4Bh ; SCAN -code <--- ? jne Low0 ; dec DRL0 ; decrease right shift counter jnl RpLeft ; mov DRL0,0 ; clear shift counter (left position) RpLeft: jmp Repeat0 ; repeat screen output ;----------------------------------------------------------------------- ; - shift the screen content by one position upwards Low0: cmp KbdScan,48h ; SCAN -code ? je Low1 ; jmp short High0 ; ; Prepare parameters and display the previous line (AX = LENGR) Low1: mov NREC,1 ; number of lines processed Call GOLOW ; back by one line mov NB,1 ; one block on screen mov EOD,0 ; clear EndOfFile indicator mov NSTR,1 ; output first line only ; Screen scrolling downwards by one line mov si,3678 ; source offset (end of line 22) mov di,3838 ; target offset (end of line 23) mov ES,VIDSEG ; target segment (video buffer) mov DS,VIDSEG ; source segment (video buffer) mov cx,22*80 ; number of words to be scrolled (22lines) std ; scroll down Call SCROLL ; functional subroutine call cld ; Clear Direction Flag mov ax,DATA ; DS points to data segment mov ds,ax ; restore segment address jmp PUTSCR ; output screen ;----------------------------------------------------------------------- ; - scroll the screen content down by one line High0: cmp KbdScan,50h ; SCAN -code ? jne CtrHom ; cmp EOD,1 ; end of file ? jne High1 ; form next screen jmp GETKEY ; repeat screen output ; Check whether the next screen is out of file (for "") High1: mov dx,CXF ; previous offset (high) mov ax,DXF ; previous offset (low)) add ax,LENGF ; low part of new offset adc dx,0 ; high part of new offset cmp dx,DX0 ; offset > length of file ? ja High2 ; yes, output screen jb High3 ; high part < length cmp ax,AX0 ; offset > length of file ? jb High3 ; High2: jmp GETKEY ; repeat screen output ; Scroll the screen content upward by one line High3: mov NSTR,24 ; number of lines to be processed mov ABUF,23*160 ; output into line 23 mov si,320 ; source offset (beginning of line 2) mov di,160 ; target offset (beginning of line 1) mov ES,VIDSEG ; target segment mov DS,VIDSEG ; source segment mov cx,22*80 ; number of words shifted cld ; Clear Direct Flag Call SCROLL ; screen scrolling subroutine call mov ax,DATA ; data segment basing mov ds,ax ; restore segment address jmp short Repeat0 ; position to screen beginning ;----------------------------------------------------------------------- ; Ctrl + Home - display the left part of lines (beginning) CtrHom: cmp KbdScan,77h ; Ctrl + Home ? jne AnyKey ; mov DRL0,0 ; clear shift counter jmp short Repeat0 ; position to screen beginning AnyKey: jmp GETKEY ; repeat screen ouputting ;----------------------------------------------------------------------- ; Repeating of the active screen outputting Repeat0: mov EOD,0 ; clear EndOfFile indicator cmp NB,2 ; two blocks on screen ? jne REP01 ; no, one block mov cx,CXF ; high part of offset mov dx,DXF ; low part of offset ; Read previous block (high part of screen) mov DXB,0 ; DXB =0 -clear block offset Call POSIT ; read block jmp PUTSCR ; repeat screen outputting ; Return to the screen beginning (block has already been read) REP01: mov ax,DXB ; offset of first line on screen mov ABLOK,ax ; address of first byte on screen mov cx,LENG0 ; full length of block mov Count,cx ; rest of block read jmp PUTSCR ; repeat screen output ;----------------------------------------------------------------------- ; Output file processing error message (error code is in the AX register) TypErr: mov ax,DATA ; address of data segment mov ds,ax ; DX:=data segment address mov si,dx ; DS:SI - message strings SetCurs 3,0 ; cursor to line 3 for outputting message mov cx,80 ; number of characters Call PUTSTR ; output string onto screen SetCurs 25,80 ; hide cursor mov dl,07h ; Bell mov ah,2 ; Put Character int 21h ; DOS service call xor ah,ah ; function 0 - Get Key int 16h ; BIOS keyboard service call ;------------------------------------------------------------------- ; Terminate program and exit to DOS Exit: cmp ERROP,0 ; Sucsesful Open ? jnz Free ; file wasn't open! mov ah,3Eh ; Function 3Eh -Close File mov bx,HANDLE ; BX - value of file handle int 21h ; DOS service call Free: Call FREEMAIN ; free the memory buffer allocate mov al,VMODE ; remember video mode on entry xor ah,ah ; function 0 - set video mode int 10h ; BIOS video service mov ax,0C00h ; Clear Keyboard Buffer int 21h ; DOS service call mov ax,4C00h ; function 4Ch - terminate process int 21h ; DOS service call ;----------------------------------------------------------------------- ; ; Functional subroutines used ; ;----------------------------------------------------------------------- ;*********************************************************** ; ; Subroutine for outputting an ASCIIZ string onto the screen ; ; DS:[SI] - address of string beginning (is output at the cursor position) ; ; CX - length of the string to be output (maximum 80 bytes) ; ; Attention! Before using this subroutine set the cursor location ; ;*********************************************************** PUTSTR PROC NEAR cld ; Clear Direct flag xor bh,bh ; video page 0 mov ah,0Eh ; function 0Eh - output in teletype mode PUTS1: lodsb ; load a byte from the string and al,al ; end of line? jz PUTS2 ; yes, return to caller int 10h ; BIOS video service loop PUTS1 ; next performance of cycle PUTS2: RETN ; Exit PUTSTR ENDP ;*********************************************************** ; ; Free the memory buffer allocated ; ;*********************************************************** FREEMAIN PROC NEAR mov ax,SEGMEM ; memory segment address and ax,ax ; memory allocated ? jnz Fremem ; yes !!! jmp short Freret ; Fremem: mov ERR0,0 ; clear error code mov es,ax ; memory segment address mov ah,49h ; free memory function code int 21h ; DOS service call jnc Freret ; lea dx,ERR00 ; free memory error code jmp TypErr ; error message output Freret: RETN FREEMAIN ENDP ;*********************************************************** ; ; Determining the type of the video adapter ; ; CGA = 1 - the CGA card is used ; ; VIDSEG -segment address of the video buffer ; ;*********************************************************** VIDTYP PROC NEAR mov VIDSEG,0B000h ; address of video buffer for MDA mov CGA,0 ; clear CGA indicator mov ax,40h ; segment address of BIOS data area mov ES,ax ; ES points to BIOS data area mov al,ES:[10h] ; read equipment list and al,30h ; clear unused bits cmp al,30h ; MDA card ? je VIDRET ; yes ! ; Find an active color card: EGA (VGA) mov VIDSEG,0B800h ; address of color adapter buffer mov CGA,1 ; set CGA indicator cmp byte ptr ES:[87h],0 ; EGA present? jz VIDRET ; EGA not installed test byte ptr ES:[87h],08h ; EGA active? jnz VIDRET ; bit 3 = 1 - EGA not active mov CGA,0 ; clear CGA indicator VIDRET: RETN ; Exit VIDTYP ENDP ;*********************************************************** ; ; Subroutine for writing a string into the video buffer ; ; DS:[SI] - address of the string to be output ; ; ES:[DI] - address of the string in the video buffer ; ; CX - max length of the output string (usually 80 bytes) ; ;*********************************************************** VIDEO PROC NEAR cld ; Clear Direct flag cmp CGA,1 ; CGA card? jne Cycle3 ; no, don't check for retrace ; Wait for retrace Cycle0: mov dx,3DAh ; video state register (CGA) Cycle1: in al,dx ; read state register test al,1 ; retrace? jnz Cycle1 ; yes, wait for finish ; Check whether it is possible to write into video buffer Cycle2: in al,dx ; read state register test al,1 ; rerace (writing allowed)? jz Cycle2 ; no, check again lodsb ; take next character from string stosb ; output character into video buffer inc di ; skip attribute in video buffer loop Cycle0 ; next step of outward cycle RETN ; Return to caller ; Non-CGA video card - direct writing always allowed Cycle3: lodsb ; take next character from string stosb ; output character into video buffer inc di ; skip attribute in video buffer loop Cycle3 ; next step of outward cycle RETN ; Return to caller VIDEO ENDP ;*********************************************************** ; ; The procedure for screen scrolling ; ; DS:[SI] - address of string to be output ; ; ES:[DI] - address of the string in the video buffer ; ; CX - number of words to be scrolled ; ; The Direction Flag is used to define the scrolling direction ; ; CLD - scroll upwards ; ; STD - scroll downwards ; ;*********************************************************** SCROLL PROC NEAR mov bl,CGA ; take CGA indicator cmp bl,1 ; CGA card? jne Cycle7 ; no, don't check for retrace ; Wait for retrace Cycle4: mov dx,3DAh ; video state register (CGA) Cycle5: in al,dx ; read state register test al,1 ; retrace? jnz Cycle5 ; yes, wait for finishing ; Check whether it is possible to write into video buffer Cycle6: in al,dx ; read state register test al,1 ; rerace (writing allowed)? jz Cycle6 ; no, check again lodsw ; take character and attribute stosw ; output character and attribute loop Cycle4 ; next step of outward cycle RETN ; return to caller ; Non-CGA video card - direct writing always allowed Cycle7: rep movsw ; output character and attribute RETN ; return to caller SCROLL ENDP ;*********************************************************** ; ; Procedure for reading a block of file (up 32768 bytes) ; ; Length of block read is returned in the AX register ; ; CF = 0 - operation comleted succesfully ; ; CF = 1 - error while reading (error code in AX) ; ;*********************************************************** RDBLOK PROC NEAR mov EOD,0 ; clear EOF flag mov ABLOK,0 ; start address of read buffer mov bx,HANDLE ; load file handle mov cx,32768 ; required length of block read lds dx,AMEM ; load: DX=0, DS is the segment address mov ah,3Fh ; function 3Fh - read file with handle int 21h ; DOS service call mov dx,DATA ; data segment address mov ds,dx ; restore the segment register mov Count,ax ; actual length of block read RETN ; Exit RDBLOK ENDP ;*********************************************************** ; ; Procedure for positionong and reading the block of file ; ; The DX:CX registers - offset from the beginning of the file ; ; The length of the block read is returned in the AX register ; ; CF = 0 - successful finish ; ; CF =1 - error reading file (error code in AX) ; ;*********************************************************** POSIT PROC NEAR mov bx,HANDLE ; load file handle mov ax,4200h ; AL = 0 - read from beginning of file int 21h ; DOS service call Call RDBLOK ; read privious block mov NB,1 ; one block on screen! RETN ; Exit POSIT ENDP ;*********************************************************** ; ; Procedure for calculating parameter for outputting the next screen ; ; CXF, DXF - offset of the current screen from the file beginning ; ; DXB - offset of the screen start from the block beginning ; ; LENGF - length of the file part currently shown ; ; LENG0 - length of the rest of previous block on screen ; ;*********************************************************** NEXTSCR PROC NEAR mov cx,CXF ; previous offset (high) mov dx,DXF ; previous offset (low) add dx,LENGF ; low part of new offset adc cx,0 ; high part of new offset ; Check whether the next screen is out of file cmp cx,DX0 ; offset > length of file ? ja NXT1 ; out of file jb NTX2 ; high part < length cmp dx,AX0 ; offset > length of file ? jb NTX2 ; NXT1: add sp,2 ; adjust stack jmp GETKEY ; display screen ; Check the number of blocks on the screen (1 or 2) NTX2: mov CXF,cx ; new offset (high) mov DXF,dx ; new offset (low) mov ax,LENGF ; length of file part on screen cmp NB,2 ; two blocks ? jne NXT3 ; block has already been read ; Change the screen containing two blocks sub ax,LENG0 ; DXB = LENGF - LENG0 mov DXB,ax ; new offset from block beginning mov ax,COUNT ; length of rest of current block mov LENG0,ax ; length of rest of previous block mov NB,1 ; after screen changed one block is shown RETN ; return to caller ; Change screen with one block present NXT3: add DXB,ax ; DXB = DXB + LENGF mov ax,DXB ; mov ABLOK,ax ; address of first byte on screen RETN ; return to caller NEXTSCR ENDP ;*********************************************************** ; ; Subroutine for reading file backwards ; ; Is used when processing the PgUp and "" keys ; ; NREC - number of lines read backwards ; ; NREC = 1 for "" key ; ; NREC = 23 for PgUp ; ; Returned values: ; ; DX = ABLOK - address of first line to be displayed ; ; CXF, DXF - offset of the first line on the screen from the file beginning ; ; DXB - offset screen beginning from the block beginning ; ; Count - length of rest of file shown on the high part of the screen ; ;*********************************************************** GOLOW PROC NEAR GOL1: cmp DXF,0 ; file beginning? (low part) jnz GOL2 ; cmp CXF,0 ; file beginning? (high part) jg GOL2 ; add sp,2 ; adjust stack jmp GETKEY ; repeat screen outputting ; Check how many blocks are on the screen (1 or 2) GOL2: cmp NB,2 ; two blocks on screen? jne GOL3 ; no, one jmp GOL7 ; yes,two GOL3: xor cx,cx ; clear LENGR + LENGF cmp DXB,0 ; block beginning jz GOL4 ; read previous block ;====== ; One block only is shown on the screen and DXB > 0 mov ES,SEGMEM ; ES -segment address of block mov di,DXB ; ES:DI - address of first line on screen mov cx,NREC ; number of lines processed Call BKREC ; find previous line mov cx,ax ; AX = LRECL - length of line found jc GOL4 ; line not found add cx,LENGF ; CX = LENGR + LENGF add Count,cx ; new length of rest of block jmp GOL8 ; normal return ; line to be displayed is on the juncture of blocks (or DXB = 0) GOL4: sub DXF,cx ; address of block juncture (high) sbb CXF,0 ; address of block juncture (low) mov cx,CXF ; high part of offset mov dx,DXF ; low part of offset sub dx,32768 ; beginning of previous block (high) sbb cx,0 ; beginning of previous block (low) jl GOL5 ; previous block < 32768 bytes ; Find first line to be shown on screen Call POSIT ; read previous block mov ES,SEGMEM ; ES - segment address of block mov di,32767 ; address of last byte in block mov cx,NREC ; number of lines to find Call BKREC ; find previous line sub Count,dx ; length of rest of block jmp short GOL8 ; normal return ; Previous block < 32768. Positioning to the beginning GOL5: xor cx,cx ; high part of offset xor dx,dx ; low part of offset Call POSIT ; read previous block mov ES,SEGMEM ; ES -segment address of block mov di,DXF ; address of first line on screen mov cx,NREC ; number of lines to find Call BKREC ; find previous line jc GOL6 ; line not found sub Count,dx ; length of rest of block jmp short GOL8 ; normal return ; Line to be displayed is located at the start of file GOL6: xor dx,dx ; address of first line mov ABLOK,dx ; offset from block beginning mov DXB,dx ; new offset of line displayed mov DXF,dx ; low part of offset = 0 mov CXF,dx ; high part of offset = 0 RETN ; return to caller ;====== ; Two blocks on screen (NB = 2). Previous block has to be read GOL7: mov cx,CXF ; high part of offset mov dx,DXF ; low part of offset sub dx,DXB ; start of previous block (high) sbb cx,0 ; start of previous (low) Call POSIT ; read previous block ; Find the line in previous block to be shown as the first line on the screen mov ES,SEGMEM ; ES - segment address of block mov di,DXB ; address of screen beginning mov cx,NREC ; number of lines inserted Call BKREC ; find previous line sub Count,dx ; length of rest of block ; Set up parameters for previous block and exit (AX -length of string GOL8: mov ABLOK,dx ; offset from block beginning mov DXB,dx ; new offset of line displayed sub DXF,ax ; low part of offset sbb CXF,0 ; high part of offset RETN ; return to caller GOLOW ENDP ;*********************************************************** ; ; Subroutine for reading the last but one line ; ; The backwards parsing of the block is performed ; ; On entry: ES:DI - address of last line beginning ; CX - the number of lines required ; ; On return: ES:DX - address of line found ; AX - length of lines found ; ; CF =0 - all length found successfully ; ; CF =1 - required nomber of lines not found ; in this case CX - number of lines not processed ; ;*********************************************************** BKREC PROC NEAR xor ax,ax ; record length counter BK0: mov dx,di ; save address dec di ; address of last byte (possibly LF) jl BK4 ; ; Find the end of last line (the CR and LF pair) BK1: cmp byte ptr ES:[DI],0Ah ; LF ? jne BK2 ; dec di ; address of previous byte jl BK4 ; inc ax ; modify length counter BK2: cmp byte ptr ES:[DI],0Dh ; CR ? jne BK3 ; dec di ; address of privious byte jl BK4 ; inc ax ; modify length counter ; Find last line (first LF from the last but one line) BK3: cmp byte ptr ES:[DI],0Ah ; LF ? je BK4 ; dec di ; address of previous byte jl BK4 ; inc ax ; modify length counter jmp short BK3 ; character found, continue cycle ; Modify pthe cycle paramters and analizing rezults BK4: inc di ; address of last line beginning jz BK5 ; beginning of file block loop BK0 ; continue lines detachment mov dx,di ; address of first line on screen clc ; CF = 0 - successful detachment RETN ; return to caller BK5: stc ; CF = 1 - requested lenes not found RETN ; return to caller BKREC ENDP _TEXT ENDS ;----------------------------------------------------------------------- ZSEG SEGMENT 'ZERO' ZSEG ENDS ;----------------------------------------------------------------------- END START