Source Code 1992 March

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Assembly Source File | 1987-09-24 | 24.1 KB | 731 lines

;from VOL6N21.ARC, SEMPER BBS ;---------------------------------------------------------------------- ; PRN2FILE.ASM - A resident program which redirects printer output. ; SYNTAX: PRN2FILE d:path:filename.ext [/Pn] [/Bn] [/U] ; 1) Run PRN2FILE with the desired filename to activate it. ; 2) Run it again with no filename to turn off redirection. ; 3) Run it with a differant filename to change destination file. ; 4) Use /P to designate the printer number (defaults to 1) ; 5) Use /B to enter buffer size in K bytes (defaults to 4) ; 6) Use /U to uninstall the program ;---------------------------------------------------------------------- CSEG SEGMENT ASSUME CS:CSEG,DS:NOTHING ORG 100H ;Beginning for .COM programs START: JMP Initialize ;Initialization code is at end ;---------------------------------------------------------------------- ; Data area used by this program ;---------------------------------------------------------------------- COPYRIGHT DB "PRN2FILE 1.0 (c) 1987 Ziff Communications Co.$",1AH PROGRAMMER DB "Tom Kihlken" REDIRECT_MESS DB "LPT" PRN_NUM DB "1 Redirected to: $" BAD_FILENAME DB "Invalid filename.$" BAD_PARAM DB "Usage: PRN2FILE [path][filename][/Pn][/Bnn][/U]$" BAD_ALLOC DB "Memory Allocation Error.$" BAD_UNINSTALL DB "Cannot Uninstall.$" PRN_TXT DB "PRN$" CRLF DB 13,10,"$" ERR_MESSAGE DB 13,10,"*Buffer Overflow*",13,10 MESS_LENGTH EQU $ - OFFSET ERR_MESSAGE OLDINT08 DD ? ;Old timer tick interrupt vector OLDINT17 DD ? ;Old printer output vector OLDINT21 DD ? ;Old dos function interrupt vector OLDINT28 DD ? ;Old dos waiting interrupt vector DOS_FLAG DD ? ;Dos busy flag SWITCH DB 0 ;On/off switch for redirecting printer TIMEOUT DW 0 ;Holds timeout counter to flush buffer INSTALLED_SEG DW 0 ;Segment location of installed copy WRITE_FLAG DB 0 ;Indicates buffer should be written PRINTER_NUM DW 0 ;Default to first parallel printer BUFF_POINTER DW 0 ;Pointer to next space in buffer BUFF_SIZE DW 4 ;Size of buffer BUFF_SEGMENT DW 0 ;Segment address of buffer TIME_TO_WRITE EQU 400H ;Flush buffer when this full ;----------------------------------------------------------------------- ; Interrupt 17 routine. (BIOS printer output) ; If output is to the selected printer and switch is on then redirect ; the character into a file. ;----------------------------------------------------------------------- NewInt17 PROC FAR ASSUME DS:NOTHING, ES:NOTHING CMP DX,CS:PRINTER_NUM ;Is this the selected printer? JNE Ignore ;If not, let bios handle it CMP CS:SWITCH,1 ;Is redirection turned on? JE Redirect_It ;If on, take jump Ignore: JMP CS:OLDINT17 ;Jump to the bios routine Redirect_It: STI ;Get interrupts back on MOV CS:TIMEOUT,91 ;Reset timeout counter PUSH SI ;Si will be used for a pointer CMP AH,1 ;Initializing the printer? JE Write_Buff ;If yes, then flush the buffer OR AH,AH ;Printing a character? JNZ Print_Ret ;If not, take jump to return MOV SI,CS:BUFF_POINTER ;Get pointer to the buffer CMP SI,CS:BUFF_SIZE ;Is buffer filled up yet? JE Print_Ret ;If full just return. PUSH DS ;Save the data segment MOV DS,CS:BUFF_SEGMENT ;Load DS with the buffer seg MOV DS:[SI],AL ;Store the character in buffer POP DS ;Restore data segment INC SI ;And point to next position MOV CS:BUFF_POINTER,SI ;Save the new pointer CMP SI,TIME_TO_WRITE ;Is buffer filling up yet? JL Print_Ret ;If not, just return Write_Buff: MOV CS:WRITE_FLAG,1 ;Signal buffer needs emptying PUSH DS PUSH BX LDS BX,CS:DOS_FLAG ;Get location of dos flag CMP BYTE PTR [BX],0 ;Is dos busy flag set? POP BX POP DS JNE Print_Ret ;If busy, do nothing CALL Write_To_File ;This empties the buffer Print_Ret: POP SI MOV AH,10010000B ;Return printer status good IRET ;Return from interrupt NewInt17 ENDP ;---------------------------------------------------------------------- ; New interrupt 08h (timer tick) decrement the timeout counter. Set ; the flush flag when counter reaches zero. ;---------------------------------------------------------------------- NewInt08 PROC FAR ASSUME DS:NOTHING, ES:NOTHING PUSHF ;Simulate an interrupt CALL CS:OLDINT08 ;Do normal timer routine DEC CS:TIMEOUT ;Count down the flush time count JNZ Still_Time ;Count until it gets to zero CMP CS:BUFF_POINTER,0 ;Anything in buffer? JE Still_Time ;If not, just continue MOV CS:WRITE_FLAG,1 ;Set flush trigger Still_Time: IRET ;Return from timer interrupt NewInt08 ENDP ;---------------------------------------------------------------------- ; Interrupt 21 routine. (DOS function calls) intercept function 40h ; when it writes to the printer. Also check to see if WRITE_FLAG is ; set to one. If it is then flush the buffer. ;---------------------------------------------------------------------- NewInt21 PROC FAR ASSUME DS:NOTHING, ES:NOTHING PUSHF ;Save the callers flags CMP CS:WRITE_FLAG,1 ;Buffer need to be written? JNE Dont_Write ;If not, then just return PUSH DS PUSH BX LDS BX,CS:DOS_FLAG ;Get location of DOS flag CMP BYTE PTR [BX],0 ;Is DOS busy flag set? POP BX POP DS JNE Dont_Write ;If busy, do nothing CALL Write_To_File ;Empty the buffer now Dont_Write: OR AH,AH ;Doing function zero? JNE Not_Zero MOV AX,4C00H ;If yes, change it to 4Ch Not_Zero: CMP AH,40H ;Writing to a device? JNE Not_Printer ;If not, just continue CMP BX,4 ;Writing to the printer handle? JNE Not_Printer ;If not, just continue CMP CS:SWITCH,1 ;Is redirection on? JE Print_It ;If yes, then redirect it Not_Printer: POPF ;Recover flags from stack CLI JMP CS:OLDINT21 ;Do the DOS function ; Emulate print string function by involking INT 17h Print_It: STI ;Reenable interrupts CLD ;String moves forward PUSH CX ;Save these registers PUSH DX PUSH SI MOV SI,DX ;Get pointer to string MOV DX,PRINTER_NUM ;Selected printer ID in DX JCXZ End_Loop ;Skip loop if count is zero Print_Loop: LODSB ;Load next character from string MOV AH,00 ;Print character function INT 17H ;BIOS print LOOP Print_Loop ;Loop through whole string End_Loop: POP SI POP DX POP CX MOV AX,CX ;All bytes were output POPF ;Restore the callers flags CLC ;Return success status STI ;Reenable interrupts RET 2 ;Return with current flags NewInt21 ENDP ;---------------------------------------------------------------------- ; This copies the buffer contents to a file. It should only be called ; when dos is in a reentrant condition. All registers are preserved ;---------------------------------------------------------------------- Write_To_File PROC NEAR ASSUME DS:NOTHING, ES:NOTHING PUSH AX ;Save registers we need to use PUSH BX PUSH CX PUSH DX PUSH DS PUSH ES PUSH CS POP DS ;Set DS to code segment ASSUME DS:CSEG ;Tell assembler DS is CSEG MOV WRITE_FLAG,0 ;Clear write request flag MOV AX,3524H ;Get dos critical error vector CALL DOS_Function ;Do the dos function PUSH BX ;Save old vector on stack PUSH ES ; Replace the dos severe error interrupt with our own routine. MOV DX,OFFSET NewInt24 MOV AX,2524H ;Setup to change int 24h vector CALL DOS_Function ;Do the dos function ; First try to open the file. If dos returns with the carry flag set, ; the file didn't exist and we must create it. Once the file is opened, ; advance the file pointer to the end of file to append. CMP BUFF_POINTER,0 ;Anything in the buffer? JE Rep_Vector ;If not, no nothing MOV DX,OFFSET FILENAME ;Point to filename MOV AX,3D02H ;Dos function to open file CALL DOS_Function ;Do the dos function JC File_Not_Found ;Set if file doesn't exist. MOV BX,AX ;Keep handle in BX also XOR CX,CX ;Move dos file pointer to the XOR DX,DX ;End of the file. this lets us MOV AX,4202H ;Append this to an existing file CALL DOS_Function ;Do the dos function JC Close_File ;On any error, take jump JMP SHORT Write_File File_Not_Found: CMP AX,2 ;Was it file not found error? JNE Rep_Vector ;If not, just quit MOV CX,0020H ;Attribute for new file MOV AH,3CH ;Create file for writing CALL DOS_Function ;Do the dos function JC Close_File ;On any error, take jump MOV BX,AX ;Save handle in BX also Write_File: xor dx,dx ;MOV DX,0 ;Point to buffer MOV CX,BUFF_POINTER ;Number of chars in buffer MOV AH,40H ;Dos write to a device function PUSH DS MOV DS,BUFF_SEGMENT ;Point to buffer segment CALL DOS_Function ;Do the dos function POP DS JC Close_File ;On any error, take jump CMP CX,AX ;Was everything written JNE Close_File ;If not, it was an error CMP CX,BUFF_SIZE ;Was buffer full? JNE Close_File ;If not everything is OK MOV DX,OFFSET ERR_MESSAGE ;Insert the error message MOV CX,MESS_LENGTH MOV AH,40H ;Dos write to file function CALL DOS_Function ;Do the dos function Close_File: MOV AH,3EH ;Dos function to close the file CALL DOS_Function ;Do the dos function Rep_Vector: MOV BUFF_POINTER,0 ;Indicate buffer is empty POP DS ;Recover int 24h vector from stack POP DX MOV AX,2524H ;Restore critical error vector CALL DOS_Function ;Do the dos function ASSUME DS:NOTHING POP ES ;Restore all registers POP DS POP DX POP CX POP BX POP AX RET ;Finished with writing to disk Write_To_File ENDP ;---------------------------------------------------------------------- ; This routine emulates an INT 21 by calling the dos interrupt address ;---------------------------------------------------------------------- DOS_Function PROC NEAR ASSUME DS:NOTHING, ES:NOTHING PUSHF ;Save the processor flags CLI ;Clear interrupt enable bit CALL CS:OLDINT21 ;Execute the interupt procedure STI ;Enable further interrupts RET ;And return to calling routine DOS_Function ENDP ;---------------------------------------------------------------------- ; New interrupt 24h (critical dos error). This interrupt is only in ; effect when writing to the disk. It is required to suppress the ; 'Abort, Retry, Ignore' message. All fatal disk errors are ignored. ;---------------------------------------------------------------------- NewInt24 PROC FAR ASSUME DS:NOTHING, ES:NOTHING STI ;Turn interrupts back on XOR AL,AL ;Tells dos to ignore the error MOV CS:SWITCH,AL ;Turn off logging of output IRET ;And return to dos NewInt24 ENDP ;---------------------------------------------------------------------- ; New interrupt 28h (DOS idle). Check to see if write_flag is set to ; one. If it is, then flush the buffer ;---------------------------------------------------------------------- NewInt28 PROC FAR ASSUME DS:NOTHING, ES:NOTHING STI CMP CS:WRITE_FLAG,0 ;Buffer need to be written? JE Do_Nothing ;If not, just continue CALL Write_To_File ;Empty the buffer Do_Nothing: JMP CS:OLDINT28 ;Continue with old interrupt NewInt28 ENDP ;---------------------------------------------------------------------- ; Here is the code used to initialize prn2file.com. First determine ; if prn2file is already installed. If it is, just copy new parameters ; into the resident programs data area, otherwise save old vectors ; and replace with new ones. The output buffer will later overlay ; this code to conserve memory. ;---------------------------------------------------------------------- ASSUME CS:CSEG, DS:CSEG, ES:NOTHING Initialize: MOV DX,OFFSET COPYRIGHT CALL String_CrLf ;Display the string ; Search for a previously installed copy of prn2file NOT WORD PTR START ;Modify to avoid false match XOR BX,BX ;Start search at segment zero MOV AX,CS ;Compare to this code segment Next_Segment: INC BX ;Look at next segment CMP AX,BX ;Until reaching this code seg MOV ES,BX JE Not_Installed MOV SI,OFFSET START ;Setup to compare strings MOV DI,SI MOV CX,16 ;16 bytes must match REP CMPSB ;Compare DS:SI to ES:DI OR CX,CX JNZ Next_Segment ;If no match, try next segment MOV ES:SWITCH,1 ;Turn redirection on MOV DX,ES:PRINTER_NUM ;Retrieve old printer number MOV DS:PRINTER_NUM,DX ;Save it here MOV AH,1 ;Initialize the resident copy INT 17H ;To flush it's buffer ADD DL,31H ;Convert printer num to ascii MOV PRN_NUM,DL ;Put it into the message area Not_Installed: MOV INSTALLED_SEG,ES PUSH CS POP ES ;Set ES to this segment ASSUME ES:CSEG CMP BYTE PTR DS:[0080],0 ;Anything entered? JE No_Params ;If not, take jump Parse: MOV AL,"/" ;Look for a slash CALL Load_Params REPNE SCASB ;Scan for slashes JCXZ Parse_Done ;Quit when no more slashes MOV AL,[DI] ;Get the parameter MOV WORD PTR [DI-1],2020H;Erase the slash and letter OR AL,32 ;Convert to lower case CMP AL,"p" ;Is it the "p" parameter JE Slash_P CMP AL,"b" ;Is it the "b" parameter JE Slash_B CMP AL,"u" ;Is it the "u" parameter JE Slash_U Invalid_Param: MOV DX,OFFSET BAD_PARAM ;Point to error message JMP Err_Exit Slash_U: JMP UnInstall ;Slash "u" means uninstall it Slash_B: MOV BUFF_SIZE,0 ;Zero buff size for accumulator Next_Digit: MOV AX,BUFF_SIZE ;Get current buff size MOV BL,10 MUL BL ;Times 10 for next digit INC DI ;Point to next digit MOV BL,[DI] ;And get the next one SUB BL,30H ;Convert it to binary JC Parse ;If not a digit, keep parsing CMP BL,9 JA Parse ;If not a digit, keep parsing MOV BYTE PTR [DI]," ";Erase character from command XOR BH,BH ADD AX,BX ;Add in this digit MOV BUFF_SIZE,AX ;And save the new total JMP short Next_Digit Slash_P: INC DI ;Point to the printer number MOV AL,[DI] MOV BYTE PTR [DI]," ";Erase this char from command MOV PRN_NUM,AL ;Put it in the message area SUB AL,31H ;Convert it to printer number XOR AH,AH ;Make it a word CMP AL,3 ;Printer id must be less than 3 JAE Invalid_Param ;If it isn't, take jump MOV PRINTER_NUM,AX ;Store the parameter JMP short Parse ;Look for more parameters No_Params: MOV DX,OFFSET REDIRECT_MESS ;Point to message MOV AH,9 ;Display the string of text INT 21H ;Using DOS display function MOV DX,OFFSET PRN_TXT ;Point to "PRN" CALL String_CrLf ;Display the string MOV AL,0 ;Turn off redirection switch JMP Check_For_Install Parse_Done: CMP BUFF_SIZE,1 ;Buff must be at least 1K JB Invalid_Param ;If not, exit with error CMP BUFF_SIZE,64 ;Check for maximum buff size JA Invalid_Param ;If above, exit with error MOV AL," " ;Look for spaces CALL Load_Params REPE SCASB ;Scan for non-space character JCXZ No_Params ;Any letters found? CMP BYTE PTR [DI],":" ;Was a drive specified? JNE Get_Def_Drive ;If not, get the default drive DEC DI ;Now DI points to first letter MOV AL,[DI] ;Get drive letter in AL MOV WORD PTR [DI],2020H;Erase the drive and colon JMP short Store_Drive Get_Def_Drive: MOV AH,19H ;Get default drive INT 21H ADD AL,65 ;Convert integer drive to ascii Store_Drive: MOV AH,":" ;AL has drive, AH has colon MOV WORD PTR FILENAME,AX ;Store drive and colon MOV AL,"\" ;Look for a backslash MOV FILENAME+2,AL ;Add a backslash to filename CALL Load_Params REPNE SCASB ;Scan for a backslash JCXZ Get_Def_Path ;If no path, use current path MOV DI,OFFSET FILENAME+2 ;Location to store path JMP short Store_Path Get_Def_Path: MOV DL,FILENAME ;Selected drive letter AND DL,11011111B ;Convert it to upper case SUB DL,64 ;Convert it to integer MOV SI,OFFSET FILENAME + 3 ;Put current path at SI MOV DI,SI ;Save this for search later MOV AH,47H ;DOS get current directory INT 21H JC Bad_Name_Exit ;Exit if invalid drive MOV AL,0 ;Look for end of path CMP [DI],AL ;Was there any path? JE Store_Path ;If not, don't scan it MOV CX,64 ;Maximum number of bytes in path REPNE SCASB ;Scan for end of path string MOV BYTE PTR [DI-1],"\" ;Add the trailing backslash Store_Path: PUSH DI ;Save location to append path MOV AL," " ;Look for blank spaces CALL Load_Params REPE SCASB ;Scan for non-blank character MOV SI,DI DEC SI ;This is first letter of path POP DI ;Get back location to append Copy_Path: LODSB ;Get next char of path CMP AL," " ;Is it a blank? JE Verify_Name ;If yes, its the last char CMP AL,13 ;Is it a carriage return? JE Verify_Name ;If yes, its the last char STOSB ;Store this letter JMP short Copy_Path ;Copy until end of path found Verify_Name: PUSH DI ;Save end of string location MOV BYTE PTR [DI],"$" ;Mark eos for dos display MOV DX,OFFSET REDIRECT_MESS ;Point to message MOV AH,9 ;Display the string of text INT 21H ;Using dos display function MOV DX,OFFSET FILENAME ;Point to filename for display CALL String_CrLf ;Display the string POP DI MOV BYTE PTR [DI],0 ;Now make it an ascii string MOV DX,OFFSET FILENAME ;Dx points to the filename MOV AX,3D00H ;Open this file for reading INT 21H JC Open_Err ;Error may indicate not found Close_It: MOV BX,AX ;Get the handle into BX MOV AH,3EH ;Close the file INT 21H JMP short Filename_Ok Open_Err: MOV CX,0020H ;Attribute for new file MOV AH,3CH ;Create file for writing INT 21H ;Dos function to create file JNC Close_It ;If no error, just close it Bad_Name_Exit: MOV DX,OFFSET BAD_FILENAME Err_Exit: CALL String_CrLf ;Display the string INT 20H ;Just exit to dos Filename_Ok: MOV ES,INSTALLED_SEG;Point to installed program PUSH DS:PRINTER_NUM ;This moves the new printer POP ES:PRINTER_NUM ;number to the resident copy MOV DI,OFFSET FILENAME ;Setup to copy the filename MOV SI,DI MOV CX,128 ;Copy entire file specification REP MOVSB ;String move instruction MOV AL,1 ;Turn redirection on Check_For_Install: MOV CX,CS CMP CX,INSTALLED_SEG MOV ES,INSTALLED_SEG MOV ES:SWITCH,AL ;Store the new on/off switch JE Install ;If not installed yet, do it now INT 20H ;Otherwise terminate ;---------------------------------------------------------------------- ; This subroutine displays a string followed by a CR and LF ;---------------------------------------------------------------------- String_CrLf PROC NEAR MOV AH,9 ;Display the string of text INT 21H ;Using dos display function MOV DX,OFFSET CRLF ;Now point to CR/LF characters MOV AH,9 ;Send the CR and LF INT 21H RET String_CrLf ENDP ;---------------------------------------------------------------------- ; This subroutine sets DI to the command line and CX to the byte count ;---------------------------------------------------------------------- Load_Params PROC NEAR MOV DI,80H ;Point to parameter area MOV CL,CS:[DI] ;Get number of chars into CL XOR CH,CH ;Make it a word INC DI ;Point to first character CLD ;String search forward RET Load_Params ENDP ;---------------------------------------------------------------------- ; This code does the actual installation by storing the existing ; interrupt vectors and replacing them with the new ones. ; Then allocate memory for the buffer. Exit and remain resident. ;---------------------------------------------------------------------- ASSUME DS:CSEG, ES:CSEG Install: MOV BX,OFFSET END_OF_CODE ;Get end of resident code ADD BX,15 MOV CL,4 ;Shift by 4 to divide by 16 SHR BX,CL ;This converts to paragraphs MOV AH,4AH ;Modify memory block INT 21H ;Dos setblock function call JNC Allocate_Buffer ;If it worked ok, then continue Alloc_Error: MOV DX,OFFSET BAD_ALLOC ;Err message for bad allocation JMP Err_Exit ;Display message and exit Allocate_Buffer: MOV BX,BUFF_SIZE ;Buffer size in K bytes MOV CL,6 ;Shift by 6 to get paragraphs SHL BX,CL ;Buffersize is in paragraphs MOV AH,48H INT 21H ;Dos allocate memory JC Alloc_Error ;If allocation error, take jump MOV BUFF_SEGMENT,AX ;Save the segment for the buffer MOV AX,BUFF_SIZE ;Buffer size in K bytes MOV CL,10 ;Shift by 10 to get bytes SHL AX,CL OR AX,AX ;Is buff_size=0 (64K)? JNZ Size_Ok DEC AX ;If yes, make it FFFFh Size_Ok: MOV BUFF_SIZE,AX ;Now buff_size is in bytes ASSUME ES:NOTHING MOV AH,34H ;Get dos busy flag location INT 21H MOV WORD PTR [DOS_FLAG] ,BX ;Store flag address MOV WORD PTR [DOS_FLAG+2],ES MOV AX,3508H ;Get timer interrupt vector INT 21H MOV WORD PTR [OLDINT08] ,BX MOV WORD PTR [OLDINT08+2],ES MOV DX, OFFSET NewInt08 MOV AX, 2508H INT 21H ;Dos function to change vector MOV AX,3517H ;Get printer interrupt vector INT 21H MOV WORD PTR [OLDINT17] ,BX MOV WORD PTR [OLDINT17+2],ES MOV DX, OFFSET NewInt17 MOV AX, 2517H INT 21H ;Dos function to change vector MOV AX,3521H ;Get dos function vector INT 21H MOV WORD PTR [OLDINT21] ,BX MOV WORD PTR [OLDINT21+2],ES MOV DX, OFFSET NewInt21 MOV AX, 2521H INT 21H ;Dos function to change vector MOV AX,3528H ;Get dos waiting vector INT 21H MOV WORD PTR [OLDINT28] ,BX MOV WORD PTR [OLDINT28+2],ES MOV DX, OFFSET NewInt28 MOV AX, 2528H INT 21H ;Dos function to change vector ;---------------------------------------------------------------------- ; Deallocate our copy of the enviornment. Exit using interrupt 27h ; (TSR). This leaves code and space for buffer resident. ;---------------------------------------------------------------------- MOV AX,DS:[002CH] ;Get segment of enviornment MOV ES,AX ;Put it into ES MOV AH,49H ;Release allocated memory INT 21H MOV DX,(OFFSET END_OF_CODE - OFFSET CSEG + 15)SHR 4 MOV AX,3100H INT 21H ;Terminate and stay resident ;---------------------------------------------------------------------- ; This procedure removes PRN2FILE from memory by replacing the vectors ; and releasing the memory used for the code and buffer. ;---------------------------------------------------------------------- ASSUME DS:CSEG, ES:NOTHING UnInstall: MOV AL,08H ;Check the timer interrupt CALL Check_Seg ;If changed, can't uninstall JNE Cant_UnInstall MOV AL,17H ;Check the printer interrupt CALL Check_Seg ;If changed, can't uninstall JNE Cant_UnInstall MOV AL,21H ;Check dos interrupt CALL Check_Seg ;If changed, can't uninstall JNE Cant_UnInstall MOV AL,28H ;Check dos idle interrupt CALL Check_Seg ;If changed, can't uninstall JNE Cant_UnInstall MOV ES,INSTALLED_SEG ASSUME DS:NOTHING, ES:NOTHING LDS DX,ES:OLDINT08 ;Get original vector MOV AX,2508H INT 21H ;Dos function to change vector LDS DX,ES:OLDINT17 ;Get original vector MOV AX,2517H INT 21H ;Dos function to change vector LDS DX,ES:OLDINT21 ;Get original vector MOV AX,2521H INT 21H ;Dos function to change vector LDS DX,ES:OLDINT28 ;Get original vector MOV AX,2528H INT 21H ;Dos function to change vector MOV ES,ES:BUFF_SEGMENT;Get segment of buffer MOV AH,49H ;Free its allocated memory INT 21H JC Release_Err ;If error, take jump MOV ES,INSTALLED_SEG;The resident program segment NOT WORD PTR ES:START MOV AH,49H ;Free its allocated memory INT 21H JC Release_Err ;If error, take jump MOV AX,4C00H INT 21H ;Exit to dos Release_Err: MOV DX,OFFSET BAD_ALLOC ;Memory allocation error JMP Err_Exit ;Exit with error message Cant_UnInstall: MOV DX,OFFSET BAD_UNINSTALL ;Point to error message JMP Err_Exit ;Exit with error message ;---------------------------------------------------------------------- ; This subroutine checks to see if an interrupt vector points to the ; installed program segment. Returns with ZF=1 if it does. ;---------------------------------------------------------------------- Check_Seg PROC NEAR MOV AH,35H ;Get the vector INT 21H ;Dos function to get the vector MOV AX,ES CMP AX,INSTALLED_SEG;Is it the installed segment? RET Check_Seg ENDP ;---------------------------------------------------------------------- FILENAME LABEL BYTE ;File name will go here END_OF_CODE = $ + 128 ;Allow 128 bytes for it CSEG ENDS END START