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

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/ ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng) / ProfitPress-MegaCDROM2.B6I / MAGAZINE / MISC / PJ_9_6.ZIP / VIDSAVE.ASM < prev next >

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Assembly Source File | 1991-10-01 | 12.5 KB | 312 lines

; VIDSAVE.COM -- Wrapper for ill-behaved programs that wipe out ; your 50- or 43-line video display mode ; ; To use this program, copy it to the directory where the .EXE for ; the target application lives. Rename this .COM file to have the ; same filename (but still a .COM extension). ; ; Copyright (c) 1991 by Walter Oney of Rational Systems, Inc. ; All rights reserved ; pushall macro push ax push bx push cx push dx push si push di push bp endm popall macro pop bp pop di pop si pop dx pop cx pop bx pop ax endm name vidsave vidsave segment byte public 'code' assume cs:vidsave, ds:vidsave org 100h ; required for .COM file usage ; Initialization. Establish reasonably sized stack and shrink ; memory block down. begin: lea sp, topsp ; set new stack top lea bx, topsp+15 ; compute # para's in shrunk block mov cl,4 shr bx, cl ; .. mov ah, 4Ah ; resize memory block int 21h ; .. mov seg1, ds ; set segment address where needed mov seg2, ds ; .. mov seg3, ds ; .. mov ah,30h ; test for DOS 3.3 or greater int 21h xchg ah,al cmp ax,0303h jae dos_ok lea dx,old_dos_msg ; indicate that we need DOS 3.3 mov ah,9 int 21h mov ax,4c01h ; terminate with error int 21h ; Locate full pathname of executed command at the end of the ; environment block. Replace the .COM extension with .EXE instead. dos_ok: cld ; forward direction mov es, word ptr ds:[2Ch] ; point ES:DI to start of environment xor di, di ; .. xor al, al ; get zero to compare against xor cx, cx ; set practically infinite count dec cx ; .. skipvar: repne scasb ; find end of environment variable scasb ; compare next byte jne skipvar ; if not another null, do it again add di, 2 ; skip word count mov execpath, di ; save ptr to start of program name repne scasb ; find end of name mov byte ptr es:[di-4], 'E' ; change extension to "EXE" mov byte ptr es:[di-3], 'X' ; .. mov byte ptr es:[di-2], 'E' ; .. mov execpath+2, es ; complete ptr to program name. push ds ; set ES back to our code/data segment pop es ; .. ; Determine the current video characteristics (mode, page, font size) mov ah, 0Fh ; get video mode int 10h ; .. mov vidmode, al ; save original mode mov vidpage, bh ; save original display page mov ah, 03h ; get cursor pos'n & shape int 10h ; .. mov vidcurs, cx ; save shape for later restore mov ax, 1130h ; get font information xor bh, bh ; for current font int 10h ; .. mov ax, 1112h ; assume we're using small font cmp cx, 8 ; using 8 * 8 font? je setfont ; if yes, good mov ax, 1114h ; no. try for the 8 * 16 font cmp cx, 16 ; .. je setfont ; .. mov ax, 1111h ; no. must be the 8 * 14 font setfont: mov vidfont, ax ; save function code to restore this font ; If we're running on a VGA, we can determine the border color by reading ; the palette register. With any sort of display, we can get the ; attribute byte for any random location on the screen. mov ah, 08h ; fcn 8: read char & attr at cursor mov bh, vidpage ; (for the current page) int 10h ; .. mov charattr, ah ; save attribute byte for later restore mov cl,4 shr ah, cl ; assume border color is same as mov border, ah ; background color of attribute mov ax, 1A00h ; issue fcn 1A (read configuration) int 10h ; .. cmp al, 1Ah ; if AL comes back != 1A, not a VGA jne notvga ; .. cmp bl, 8 ; is primary display a VGA with color? jne notvga ; if not, don't try to read border color. mov ax, 1008h ; read border color int 10h ; .. mov border, bh ; save border color for later restore notvga: ; Hook INT 10 so we can prevent the cursor from getting screwed up. ; Hook INT 21 so we can monitor for EXEC calls and run them with ; the original video mode. mov ax, 3510h ; get current INT 10 & 21 vectors int 21h ; .. mov word ptr org10, bx ; .. mov word ptr org10+2, es ; .. mov ax, 3521h ; .. int 21h ; .. mov word ptr org21, bx ; .. mov word ptr org21+2, es ; .. push ds ; restore ES pop es ; .. lea dx, int10 ; hook INT 10 mov ax, 2510h ; .. int 21h ; .. lea dx, int21 ; hook INT 21 also mov ax, 2521h ; .. int 21h ; .. ; Execute the application whose filename is the same as our own filename. lea bx, execparm ; es:bs -> parameter block lds dx, dword ptr execpath ; ds:dx -> pathname assume ds:nothing mov ax, 4B00h ; load & execute program pushf ; don't go through our EXEC trap! call dword ptr cs:[org21]; .. mov ax, cs ; reset segment registers mov ds, ax ; .. mov es, ax ; .. assume ds:vidsave ; .. ; Restore the environment and terminate push ds ; save DS across unhook lds dx, org10 ; unhook INT 10 mov ax, 2510h ; .. pushf ; .. call dword ptr cs:[org21] ; .. pop ds ; .. push ds ; unhook INT 21 too lds dx, org21 ; .. mov ax, 2521h ; .. pushf ; .. call dword ptr cs:[org21] ; .. pop ds ; .. call near ptr vidrest ; restore video environment mov ax, 4C00h ; terminate process int 21h ; .. ; INT 10 handler (needed to prevent cursor from disappearing on ; my home machine due to probable video BIOS bug): assume nothing, cs:vidsave int10: cmp ah, 01h ; look for Set Cursor Type call je setcur ; stay here if so chain10: jmp dword ptr cs:[org10]; chain to original 6D handler setcur: cmp cx, 0600h ; check for start 6, end 0 je fixcur ; .. cmp cx, 0200h ; also for start 2, end 0 jne chain10 ; ignore all other cursor sets mov cx, 0207h ; set end row 7 jmp chain10 ; .. fixcur: mov cx, 0507h ; set end row 7 jmp chain10 ; chain to original handler ; INT 21 handler (needed to restore video during EXEC from application): int21: cmp ah, 4Bh ; EXEC function? je exec ; if yes, stay here to deal with it jmp dword ptr cs:[org21]; no. chain to original handler exec: pushall ; save everything push ds ; .. push es ; .. lds dx, cs:org21 ; unhook ourselves during EXEC mov ax, 2521h ; .. pushf ; .. call dword ptr cs:[org21]; .. mov ax, cs ; get DS addressability for VIDREST mov ds, ax ; .. call near ptr vidrest ; restore video to original pop es ; restore everything pop ds ; .. popall ; .. int 21h ; do EXEC from here pushall ; save registers again push ds ; .. push es ; .. mov ax, cs ; rehook INT 21 mov ds, ax ; .. mov dx, offset int21 ; .. mov ax, 2521h ; .. pushf ; .. call dword ptr cs:[org21]; .. pop es ; restore registers pop ds ; .. popall ; .. iret ; return to application ; Internal procedure to restore the video environment: assume ds:vidsave vidrest proc near mov al, vidmode ; restore original video mode xor ah, ah ; .. int 10h ; .. mov ax, 0500h ; force display page 0 int 10h ; .. mov ax, vidfont ; restore original font xor bl, bl ; character block = 0 int 10h ; .. mov ah, 03h ; get cursor to reset MCGA xor bh, bh ; .. int 10h ; .. mov al, vidpage ; restore original display page mov ah, 5 ; .. int 10h ; .. mov cx, vidcurs ; restore cursor shape mov ah, 01h ; .. int 10h ; .. mov ax, 1001h ; fcn 10, subfcn 01: set border color mov bh, border ; .. int 10h ; .. mov ax, 0600h ; fcn 06: scroll up, al=0: clear window mov bh, charattr ; attribute to fill window with xor cx, cx ; ch/cl = top/left mov dx, 40h ; address BIOS data area at 40: mov es, dx ; .. mov dx, es:4Ah ; set DL = right column dec dx ; .. mov dh, es:84h ; set DH = bottom row int 10h ; go clear the whole screen ret ; return to local caller vidrest endp ; Data: execpath dw 0 ; offset to name of program to execute execparm dw 0 ; seg # of environment (also part of ptr) dw 80h ; segment:offset of command tail seg1 dw ? ; .. dw 5Ch ; segment:offset of 1st FCB seg2 dw ? ; .. dw 6Ch ; segment:offset of 2d FCB seg3 dw ? ; .. vidfont dw ? ; INT 10 fcn to restore font vidpage db ? ; video page number vidmode db ? ; video mode vidcurs dw ? ; original cursor shape border db ? ; border color charattr db ? ; character attribute to restore org10 dd 0 ; original INT 10 vector org21 dd 0 ; original INT 21 vector db 128 dup (0) ; presumably enough stack . . . topsp label byte old_dos_msg db 'This program requires DOS 3.3 or greater',0dh,0ah,'$' vidsave ends end begin