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Assembly Source File | 1993-03-31 | 17.9 KB | 368 lines

;**************************************************************************** ; REMOVE removes a bookmark placed in memory by INSTALL. Its syntax is: ; ; REMOVE [bookmark] [/L] ; ; where "bookmark" is the name of the bookmark to be removed from memory, ; and /L lists the bookmarks that are currently resident in memory. When ; a bookmark is removed, all the TSRs installed above it are removed also. ; Run with no command line parameters, REMOVE removes the highest bookmark ; in memory. ;**************************************************************************** nextblock equ 0103h ;Offset of NEXTBLOCK field bm_addr equ 0105h ;Offset of bookmark field vectors equ 0133h ;Offset of vector field code segment assume cs:code,ds:code org 100h begin: jmp main helpmsg db "Removes a bookmark created with INSTALL." db 13,10,13,10 db "REMOVE [bookmark] [/L]",13,10,13,10 db " bookmark Name of the bookmark to remove.",13,10 db " /L List the bookmarks currently " db "installed.",13,10,13,10 db "Run with no parameters, REMOVE removes the most " db "recently installed bookmark.",13,10 db "When a bookmark is removed, all the TSRs installed " db "after it are removed, too.",13,10,"$" errmsg1 db "Syntax: REMOVE [bookmark] [/L]",13,10,"$" errmsg2 db "Requires DOS 3.0 or higher",13,10,"$" errmsg3 db "There are no bookmarks installed",13,10,"$" errmsg4 db "There is no bookmark by that name",13,10,"$" errmsg5 db "Memory deallocation failed",13,10,"$" msg1 db "REMOVE 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 $" msg2 db " removed" crlf db 13,10,"$" lastblock dw ? ;Segment of last block bookmark db 33 dup (0Dh) ;Bookmark name signature db 0,1,2,"INSTALL",2,1,0 ;INSTALL signature ;**************************************************************************** ; Procedure MAIN ;**************************************************************************** main 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. ; checkver: mov dx,offset errmsg2 ;Exit if DOS version mov ah,30h ;is less than 3.0 int 21h cmp al,3 jae checkins error: mov ah,09h ;Display error message and int 21h ;exit with ERRORLEVEL=1 mov ax,4C01h int 21h checkins: call check_install ;See if INSTALL is installed mov dx,offset errmsg3 jnc error ;Exit if it's not ; ; Parse the command line. ; mov lastblock,cs ;Initialize LASTBLOCK mov si,81h ;Reset SI call findchar ;Find the first parameter jc search1 ;Branch if there are none cmp byte ptr [si],"/" ;Branch if the character jne parse ;is not a "/" ; ; Process a /L switch. ; list: inc si ;Skip the "/" character lodsb ;Get the next character and al,0DFh ;Capitalize it mov dx,offset errmsg1 ;Initialize error pointer cmp al,"L" ;Error if the character is jne error ;not an "L" nextname: mov di,bm_addr ;Point DI to bookmark name call dos_out ;Display bookmark name mov ah,09h ;Move the cursor to the mov dx,offset crlf ;next line int 21h cmp word ptr es:[nextblock],0FFFFh ;Exit if this is the je list_exit ;last block mov es,es:[nextblock] ;Get segment of next block jmp nextname ;Go back and output its name list_exit: mov ax,4C00h ;Exit with ERRORLEVEL=0 int 21h ; ; Read the bookmark name from the command line. ; parse: 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: mov [di],al ;Store it inc di ;Increment DI cmp al,0Dh ;Branch if it was a carriage je search ;return loop parse1 ;Loop back for more ; ; Search out a bookmark. ; search: mov si,offset bookmark ;Point SI to local name mov di,bm_addr ;Point DI to remote name call compare_names ;Compare the two je endchain ;Branch if they're equal mov dx,offset errmsg4 cmp word ptr es:[nextblock],0FFFFh je error ;Error if last block mov lastblock,es ;Save last block address mov es,es:[nextblock] ;Get address of next block jmp search ;Return to search loop search1: cmp word ptr es:[nextblock],0FFFFh je endchain ;Branch if last block mov lastblock,es ;Save last block address mov es,es:[nextblock] ;Get address of next block jmp search1 ;Continue the search ; ; Terminate the chain of INSTALLed blocks and restore interrupt vectors. ; endchain: push es ;Save ES mov es,lastblock ;Retrieve last block address mov word ptr es:[nextblock],0FFFFh ;Terminate the chain pop es ;Restore ES mov lastblock,es ;Save ES in LASTBLOCK push ds ;Save DS and ES push es mov ax,es ;Point DS:SI to copy of mov ds,ax ;interrupt vectors in assume ds:nothing ;INSTALLed block mov si,vectors sub di,di ;Point ES:DI to 0000:0000 mov es,di mov cx,512 ;Initialize counter cli ;Disable interrupts rep movsw ;Restore interrupt vectors sti ;Enable interrupts pop es ;Restore DS and ES pop ds assume ds:code ; ; Search out every PSP block above INSTALL and deallocate the memory that ; belongs to it. ; mov bx,es ;Transfer ES to BX mov ah,49h ;Deallocate the memory used int 21h ;by INSTALL mov dx,offset errmsg5 ;Initialize error pointer jc error1 ;Error if call failed remove: dec bx ;Point BX to MCB mov es,bx ;Transfer BX to ES add bx,es:[03h] ;Compute next MCB address inc bx mov es,bx ;Transfer segment to ES inc bx ;Point BX to segment beyond cmp bx,es:[01h] ;Does the segment own itself? jne remove ;No, then continue searching mov ax,cs ;Record current segment in AX cmp bx,ax ;Have we reached our own PSP? je done ;Yes, then we're done push bx ;Save PSP segment address call freemem ;Free all memory it owns pop bx ;Retrieve the address mov dx,offset errmsg5 ;Loop back if no error jnc remove ;occurred error1: jmp error ;Exit on error ; ; Announce that REMOVE succeeded and terminate. ; done: mov ah,09h ;Display message verifying mov dx,offset msg1 ;that the book mark was int 21h ;removed mov es,lastblock mov di,bm_addr call dos_out mov ah,09h mov dx,offset msg2 int 21h mov ax,4C00h ;Exit with ERRORLEVEL=0 int 21h main 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 a copy of INSTALL is installed, ; carry clear if it's not. If carry returns set, AH holds INSTALL's ; multiplex ID number and ES holds its segment address. ;**************************************************************************** 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 ;**************************************************************************** ; FREEMEM frees all the memory blocks owned by the process whose PSP ; address is passed in BX. Carry is set on return if a call to release ; a block of memory failed. ;**************************************************************************** freemem proc near push bx ;Save BX mov ah,52h ;Get address of the first int 21h ;MCB with DOS function 52H mov dx,es:[bx-2] ;Copy the address to DX mov es,dx ;Also copy it to ES pop bx ;Restore BX free1: cmp bx,es:[01h] ;Branch if the ownership jne free2 ;word does not match inc dx ;Increment DX mov es,dx ;Point ES to segment mov ah,49h ;Deallocate the segment int 21h jc free_exit ;Exit if called failed dec dx ;Decrement DX mov es,dx ;Point ES back to the MCB free2: add dx,es:[03h] ;Compute the address of the inc dx ;next MCB mov es,dx ;Transfer address to ES cmp byte ptr es:[00h],"Z" ;End of the MCB chain? jne free1 ;No, then continue the search clc ;Clear carry and exit free_exit: ret freemem endp ;**************************************************************************** ; COMPARE_NAMES compares the two ASCII strings addressed by DS:SI and ES:DI. ; On return, the Z flag indicates whether or not the two are equal. ;**************************************************************************** compare_names proc near lodsb ;Get a character cmp al,0Dh ;Exit if it's a carriage je compare_exit ;return scasb ;Compare it ES:[DI] je compare_names ;Loop back if they're euqal compare_exit: ret ;Return to caller compare_names endp ;**************************************************************************** ; DOS_OUT displays the ASCII string pointed to by ES:DI. ;**************************************************************************** dos_out proc near mov dl,es:[di] ;Get a character cmp dl,0Dh ;Exit if it's a carriage je dos_exit ;return mov ah,02h ;Output it using DOS int 21h ;function 02H inc di ;Advance DI to next one jmp dos_out ;Loop until done dos_exit: ret dos_out endp code ends end begin