POINT Software Programming

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Assembly Source File | 1993-03-31 | 13.8 KB | 298 lines

;**************************************************************************** ; INSTALL inserts a bookmark in memory that allows TSRs installed above it ; to be removed from memory. Its syntax is: ; ; INSTALL [bookmark] ; ; where "bookmark" is the name of the bookmark. The bookmark name can be ; passed to REMOVE when a bookmark is removed. Only the first 32 characters ; of the name are used. ;**************************************************************************** code segment assume cs:code org 100h begin: jmp init nextblock dw 0FFFFh ;Pointer to next block bookmark db "(No Name)",24 dup (0Dh);Default bookmark name signature db 0,1,2,"INSTALL",2,1,0 ;Program signature vectors dw 512 dup (?) ;Interrupt vectors prog_id db ? ;Multiplex ID number int2Fh dd ? ;Interrupt 2FH vector ;**************************************************************************** ; MPLEX_INT handles interrupt 2FH. If, on entry, AH is set to INSTALL's ; multiplex ID number, MPLEX_INT uses the value in AL as a function code. ; The functions supported are: ; ; 00H Returns FFH in AL to indicate the program is installed ; and returns the address of its signature in ES:DI. ;**************************************************************************** mplex_int proc far pushf ;Save FLAGS register cmp ah,cs:[prog_id] ;Branch if AH holds the je mplex2 ;multiplex ID popf ;Restore FLAGS jmp cs:[int2Fh] ;Pass the interrupt on ; ; Function 00H verifies that the program is installed. ; mplex2: popf ;Restore FLAGS or al,al ;Branch if function code jnz mplex3 ;is other than 00H mov al,0FFh ;Set AL to FFH push cs ;Point ES:DI to the program pop es ;signature mov di,offset signature mplex3: iret ;Return from interrupt mplex_int endp ;**************************************************************************** ; Data that will be discarded when the program becomes memory-resident. ;**************************************************************************** helpmsg db "Places a bookmark in memory that marks TSRs for " db "unloading.",13,10,13,10 db "INSTALL [bookmark]",13,10,13,10 db " bookmark Name of the bookmark being installed." db 13,10,13,10 db "Bookmarks can be removed with INSTALL's companion " db "program, REMOVE. When a",13,10 db "bookmark is removed, all the TSRs installed after " db "it are removed, too.",13,10,"$" errmsg1 db "Requires DOS 3.0 or higher",13,10,"$" errmsg2 db "INSTALL cannot be loaded high",13,10,"$" errmsg3 db "Program could not be installed",13,10,"$" msg1 db "INSTALL 1.3 Copyright (c) 1993 Jeff Prosise",13,10 db "From: PC Magazine DOS 6 Memory Management " db "with Utilities",13,10,13,10 db "Bookmark created. Use REMOVE to remove it." db 13,10,"$" ;**************************************************************************** ; INIT makes the program resident in memory. ;**************************************************************************** assume cs:code,ds:code init proc near cld ;Clear direction flag mov si,81h ;Point SI to command line call scanhelp ;Scan for "/?" switch jnc checkver ;Branch if not found mov ah,09h ;Display help text and exit mov dx,offset helpmsg ;with ERRORLEVEL=0 int 21h mov ax,4C00h int 21h ; ; Check the DOS version and make sure the program isn't loaded high. ; checkver: mov dx,offset errmsg1 ;Exit if DOS version mov ah,30h ;is less than 3.0 int 21h cmp al,3 jae checkaddr error: mov ah,09h ;Display error message and int 21h ;exit with ERRORLEVEL=1 mov ax,4C01h int 21h checkaddr: mov dx,offset errmsg2 ;Error if program is loaded mov ax,cs ;at segment address A000H or cmp ax,0A000h ;higher jae error ; ; Parse the command line. ; call findchar ;Advance to first character jc copy ;Branch if no parameters mov di,offset bookmark ;Point DI to buffer mov cx,32 ;Initialize counter parse1: lodsb ;Get a character cmp al,"a" ;Capitalize it if it's jb parse2 ;between "a" and "z" cmp al,"z" ja parse2 and al,0DFh parse2: stosb ;Store it cmp al,0Dh ;Branch if was a carriage je copy ;return loop parse1 ;Loop back for more ; ; Copy the interrupt vector table from low memory. ; copy: push ds ;Save DS sub si,si ;Point DS:SI to 0000:0000 mov ds,si assume ds:nothing mov di,offset vectors ;Point DI to storage area mov cx,512 ;Initialize counter cli ;Disable interrupts rep movsw ;Copy the vector table sti ;Enable interrupts pop ds ;Restore DS assume ds:code ; ; Install the program. ; call check_install ;Branch if a copy of INSTALL jnc install_full ;is not already installed mov di,offset nextblock ;Point DI to NEXTBLOCK install1: cmp word ptr es:[di],0FFFFh ;Branch if this is not the jne install2 ;last block in the chain mov word ptr es:[di],cs ;Record the address of this jmp short install_part ;block if it is install2: mov es,es:[di] ;Point ES to next block in jmp install1 ;the chain and loop back install_full: call mplex_id ;Find a multiplex ID number mov dx,offset errmsg3 ;Error if none available jc error mov prog_id,ah ;Save the ID number mov ax,352Fh ;Hook interrupt 2FH int 21h mov word ptr int2Fh,bx mov word ptr int2Fh[2],es mov ax,252Fh mov dx,offset mplex_int int 21h install_part: mov ah,49h ;Get the segment address of mov es,ds:[2Ch] ;the environment block int 21h ;and free the segment mov ah,09h ;Display message verifying mov dx,offset msg1 ;the installation int 21h mov ax,3100h ;Terminate with function 31H mov dx,(offset helpmsg - offset code + 15) shr 4 int 21h init endp ;**************************************************************************** ; FINDCHAR advances SI to the next non-white-space character. On return, ; carry set indicates EOL was encountered. ;**************************************************************************** findchar proc near lodsb ;Get the next character cmp al,09h ;Loop if tab je findchar cmp al,20h ;Loop if space je findchar cmp al,2Ch ;Loop if comma je findchar dec si ;Point SI to the character cmp al,0Dh ;Exit with carry set if end je eol ;of line is reached clc ;Clear carry and exit ret eol: stc ;Set carry and exit ret findchar endp ;**************************************************************************** ; SCANHELP scans the command line for a /? switch. If found, carry returns ; set and SI contains its offset. If not found, carry returns clear. ;**************************************************************************** scanhelp proc near push si ;Save SI scanloop: lodsb ;Get a character cmp al,0Dh ;Exit if end of line je scan_exit cmp al,"?" ;Loop if not "?" jne scanloop cmp byte ptr [si-2],"/" ;Loop if not "/" jne scanloop add sp,2 ;Clear the stack sub si,2 ;Adjust SI stc ;Set carry and exit ret scan_exit: pop si ;Restore SI clc ;Clear carry and exit ret scanhelp endp ;**************************************************************************** ; CHECK_INSTALL returns carry set if the program is already installed, ; carry clear if it's not. If carry returns set, AH holds the program's ; multiplex ID number. ;**************************************************************************** check_install proc near mov ax,0C000h ;Initialize AH and AL mov cx,40h ;Initialize count chinst1: push ax ;Save AX and CX push cx sub di,di ;Set ES and DI to 0 mov es,di int 2Fh ;Interrupt 2Fh cmp al,0FFh ;Nothing here if AL isn't jne chinst2 ;equal to FFH mov si,offset signature ;See if program signature mov cx,13 ;appears at the address repe cmpsb ;returned in ES:DI jne chinst2 ;Branch if it does not pop cx ;Clear the stack and exit pop ax ;with carry set stc ret chinst2: pop cx ;Retrieve AX and CX pop ax inc ah ;Next multiplex ID loop chinst1 ;Loop until done clc ;Exit with carry clear ret check_install endp ;**************************************************************************** ; MPLEX_ID searches for an unused multiplex ID number. If one is found, ; it is returned in AH with carry clear. Carry set means no multiplex ; ID numbers are currently available. ;**************************************************************************** mplex_id proc near mov ax,0C000h ;Initialize AH and AL mov cx,40h ;Initialize count mxid1: push ax ;Save AX and CX push cx int 2Fh ;Interrupt 2Fh or al,al ;Branch if AL=0 jz mxid2 pop cx ;Retrieve AX and CX pop ax inc ah ;Increment ID number loop mxid1 ;Loop until done stc ;Exit with carry set ret mxid2: pop cx ;Clear the stack and exit pop ax ;with carry clear clc ret mplex_id endp code ends end begin