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Text File | 1991-03-09 | 50.9 KB | 1,290 lines

.MODEL small, pascal, os_dos ; Prototypes for internal procedures Activate PROTO NEAR CheckRequest PROTO NEAR CheckDos PROTO NEAR CheckHardware PROTO NEAR GetDosFlags PROTO NEAR INCLUDE tsr.inc .CODE ; Stack buffer used by TSR. Size is determined by constant STACK_SIZ, ; declared in TSR.INC file. NewStack points to top of stack. EVEN BYTE STACK_SIZ DUP(?) ; Stack buffer NewStack LABEL BYTE ; Pointer to top of stack ; Structures for interrupt handlers or "interrupt service routines." ; The following handlers are replaced during installation. Such routines ; usually set a flag to indicate they are active, optionally do some ; processing (such as detecting a hot key), call the old system interrupt ; routine, and when finished clear the active flag. HandArray LABEL BYTE ; Array of handler structures ; Num Flag OldHand NewHand intClock INTR < 8h, FALSE, NULL, Clock> intKeybrd INTR < 9h, FALSE, NULL, Keybrd> intVideo INTR <10h, FALSE, NULL, Video> intDiskIO INTR <13h, FALSE, NULL, DiskIO> intMisc INTR <15h, FALSE, NULL, SkipMiscServ> intIdle INTR <28h, FALSE, NULL, Idle> intMultex INTR <2Fh, FALSE, NULL, Multiplex> CHAND EQU ($ - HandArray) / (SIZEOF INTR) ; Number of handlers in array ; Interrupt trap routines. These interrupt routines are set up ; temporarily to trap keyboard break errors and critical errors ; while the TSR is active. When the TSR finishes its tasks, it ; restores the old interrupts before returning. TrapArray LABEL BYTE ; Array of trap structures ; Num Flag OldHand NewHand intCtrlBk INTR <1Bh, FALSE, NULL, CtrlBreak> intCtrlC INTR <23h, FALSE, NULL, CtrlC> intCritEr INTR <24h, FALSE, NULL, CritError> CTRAP EQU ($ - TrapArray) / (SIZEOF INTR) ; Number of traps in array ; Address of application's stack. Before calling the main body of the TSR, ; the Activate procedure stores the application's stack address, then resets ; SS:SP to point to LABEL NewStack (see above). This gives the TSR its own ; stack space without making demands on the current stack. Activate restores ; the application's stack before returning. OldStackAddr FPVOID ? ; SS:SP pointer to application stack ; The TSR must set up its own disk transfer area if it calls DOS functions ; that use the DTA (see Section 19.5.3 of the Programmer's Guide). DTA_SIZ ; is defined in the TSR.INC include file. IFDEF DTA_SIZ OldDtaAddr FPVOID ? ; Address of application's DTA DtaBuff BYTE DTA_SIZ DUP(?) ; DTA buffer ENDIF ; Multiplex data. STR_LEN is defined in the TSR.INC include file IDnumber BYTE 0 ; TSR's identity number IDstring BYTE STR_LEN DUP (0) ; Copy of identifier string IDstrlen WORD ? ; Length of identifier string ShareAddr FPVOID ? ; Address of shared memory ; Miscellaneous data TsrRequestFlag BYTE FALSE ; Flag set when hot key is pressed TsrActiveFlag BYTE FALSE ; Flag set when TSR executes BreakCheckFlag BYTE ? ; Break-checking status of application TsrPspSeg WORD ? ; Segment address of PSP TsrAddr FPVOID ? ; Pointer to main part of TSR CritErrAddr FPVOID ? ; Pointer to MS-DOS critical error flag InDosAddr FPVOID ? ; Pointer to MS-DOS InDos flag ; Scan and shift codes for hot key. Install procedure initializes ; HotScan, HotShift, and HotMask during installation. HotScan BYTE ? ; Scan code hot key HotShift BYTE ? ; Shift value of hot key HotMask BYTE ? ; Mask unwanted shift values Version LABEL WORD ; DOS version number minor BYTE ? major BYTE ? ; Timer data, used when the TSR is activated at a preset time instead ; of activated from the keyboard. The following variables serve the ; same purposes as the counter variables used in the ALARM.ASM program ; presented in Section 19.3 of the Programmer's Guide. Refer to the ; header comments in the Install procedure for an explanation of how ; to set up a time-activated TSR. Tick91 BYTE 91 ; Measures 91 timer ticks (5 seconds) CountDown WORD 0 ; Counts 5-second intervals ;* Clock - Interrupt handler for Interrupt 08 (timer). Executes at each ;* timer interrupt; these occur an average of 18.2 times per second. Clock ;* first allows the original timer service routine to execute. It then ;* checks the flag TsrRequestFlag maintained either by the keyboard handler ;* (if keyboard activated) or by this procedure (if time activated). If ;* TsrRequestFlag = TRUE and system is okay, Clock invokes the TSR by ;* calling the Activate procedure. Uses an active flag to prevent the ;* Clock procedure from being reentered while executing. ;* ;* Uses: intClock, TsrActiveFlag, CountDown ;* ;* Params: None ;* ;* Return: None Clock PROC FAR pushf ; Simulate interrupt by pushing flags, call cs:intClock.OldHand ; far calling orig Int 08 routine .IF cs:intClock.Flag == FALSE ; If not already in this handler: mov cs:intClock.Flag, TRUE ; Set active flag sti ; Interrupts are okay push ds ; Save application's DS push cs pop ds ; Set DS to resident code segment ASSUME ds:@code INVOKE CheckRequest ; Check conditions .IF !carry? ; If TSR requested and safe, mov TsrActiveFlag, TRUE ; activate TSR INVOKE Activate mov TsrActiveFlag, FALSE .ENDIF ; End carry flag check cmp CountDown, 0 ; If CountDown = 0, TSR is not time je ticked ; activated or has already executed dec Tick91 ; Else count down 91 timer ticks jnz ticked ; If 91 ticks have not elapsed, exit mov Tick91, 91 ; Else reset secondary counter and dec CountDown ; subract one 5-second interval ja ticked ; If counter not yet drained, exit mov TsrRequestFlag, TRUE ; Else raise request flag ticked: mov intClock.Flag, FALSE ; Clear active flag pop ds ; Recover application's DS ASSUME ds:NOTHING .ENDIF ; End in-handler check iret Clock ENDP ;* Keybrd - Interrupt handler for Interrupt 09 (keyboard). ;* ;* IBM PC/AT and compatibles: ;* Gets the scan code of the current keystroke from port 60h. Then ;* compares the scan code and shift state to the hot key. If they ;* match, sets TsrRequestFlag to signal the handlers Clock and Idle ;* that the TSR is requested. ;* ;* IBM PS/2 series: ;* Only the instructions at KeybrdMonitor (see below) are installed ;* as Interrupt 09 handler, since above method should not be used to ;* determine current keystroke in IBM PS/2 series. In this case, the ;* Interrupt 15h handler MiscServ takes care of checking the scan codes ;* and setting the request flag when the hot key is pressed. ;* ;* Time-activated TSRs: ;* If the TSR is activated by time instead of by a hotkey, KeybrdMonitor ;* serves as the Interrupt 09 handler for both PC/AT and PS/2 systems. ;* ;* Uses: intKeybrd, TsrRequestFlag ;* ;* Params: None ;* ;* Return: None Keybrd PROC FAR sti ; Interrupts are okay push ax ; Save AX register in al, 60h ; AL = scan code of current key call CheckHotKey ; Check for hot key .IF !carry? ; If not hot key: ; Hot key pressed. Reset the keyboard to throw away keystroke. cli ; Disable interrupts while resetting in al, 61h ; Get current port 61h state or al, 10000000y ; Turn on bit 7 to signal clear keybrd out 61h, al ; Send to port and al, 01111111y ; Turn off bit 7 to signal break out 61h, al ; Send to port mov al, 20h ; Reset interrupt controller out 20h, al sti ; Reenable interrupts pop ax ; Recover AX mov cs:TsrRequestFlag, TRUE ; Raise request flag iret ; Exit interrupt handler .ENDIF ; End hot-key check ; No hot key was pressed, so let normal Int 09 service routine take over pop ax ; Recover AX and fall through cli ; Interrupts cleared for service KeybrdMonitor LABEL FAR ; Installed as Int 09 handler for ; PS/2 or for time-activated TSR mov cs:intKeybrd.Flag, TRUE ; Signal that interrupt is busy pushf ; Simulate interrupt by pushing flags, call cs:intKeybrd.OldHand ; far calling old Int 09 routine mov cs:intKeybrd.Flag, FALSE iret Keybrd ENDP ;* Video - Interrupt handler for Interrupt 10h (video). Allows the original ;* video service routine to execute. Maintains an active flag to prevent ;* the TSR from being called while Interrupt 10h is executing. ;* ;* Uses: intVideo ;* ;* Params: Registers passed to Interrupt 10h ;* ;* Return: Registers returned by Interrupt 10h Video PROC FAR mov cs:intVideo.Flag, TRUE ; Set active flag pushf ; Simulate interrupt by pushing flags, call cs:intVideo.OldHand ; far calling old Int 10h routine mov cs:intVideo.Flag, FALSE ; Clear active flag iret Video ENDP ;* DiskIO - Interrupt handler for Interrupt 13h (disk I/O). Allows the ;* original disk I/O service routine to execute. Maintains an active flag ;* to prevent the TSR from being called while Interrupt 13h is executing. ;* ;* Uses: intDiskIO ;* ;* Params: Registers passed to Interrupt 13h ;* ;* Return: Registers and the carry flag returned by Interrupt 13h DiskIO PROC FAR mov cs:intDiskIO.Flag, TRUE ; Set active flag pushf ; Simulate interrupt by pushing flags, call cs:intDiskIO.OldHand ; far calling old Int 13h routine mov cs:intDiskIO.Flag, FALSE; Clear active flag without ; disturbing flags register sti ; Enable interrupts ret 2 ; Simulate IRET without popping flags ; (since services use carry flag) DiskIO ENDP ;* MiscServ - Interrupt handler for Interrupt 15h (Miscellaneous System ;* Services). ;* ;* IBM PC/AT and compatibles: ;* Stub at SkipMiscServ is used as handler, bypassing all calls to ;* Interrupt 15h. Keypresses are checked by Keybrd (Int 09 handler). ;* ;* IBM PS/2 series: ;* This procedure handles calls to Interrupt 15h, searching for ;* Function 4Fh (Keyboard Intercept Service). When AH = 4Fh, gets ;* scan code of current keystroke in AL register. Then compares the ;* scan code and shift state to the hot key. If they match, sets ;* TsrRequestFlag to signal the handlers Clock and Idle that the ;* TSR is requested. ;* ;* Uses: intMisc, TsrRequestFlag ;* ;* Params: Registers passed to Interrupt 15h ;* ;* Return: Registers returned by Interrupt 15h MiscServ PROC FAR sti ; Interrupts okay .IF ah == 4Fh ; If Keyboard Intercept Service, push ax ; preserve AX, call CheckHotKey ; check for hot key pop ax .IF !carry? ; If hot key, mov cs:TsrRequestFlag, TRUE ; raise request flag, clc ; signal BIOS not to process the key, ret 2 ; simulate IRET without popping flags .ENDIF ; End carry flag check .ENDIF ; End Keyboard Intercept check cli ; Disable interrupts and fall through SkipMiscServ LABEL FAR ; Interrupt 15h handler if PC/AT jmp cs:intMisc.OldHand MiscServ ENDP ;* CtrlBreak - Interrupt trap for Interrupt 1Bh (CTRL+BREAK Handler). ;* Disables CTRL+BREAK processing. ;* ;* Params: None ;* ;* Return: None CtrlBreak PROC FAR iret CtrlBreak ENDP ;* CtrlC - Interrupt trap for Interrupt 23h (CTRL+C Handler). ;* Disables CTRL+C processing. ;* ;* Params: None ;* ;* Return: None CtrlC PROC FAR iret CtrlC ENDP ;* CritError - Interrupt trap for Interrupt 24h (Critical Error Handler). ;* Disables critical error processing. ;* ;* Params: None ;* ;* Return: AL = Stop code 0 or 3 CritError PROC FAR sti sub al, al ; Assume DOS 2.x ; Set AL = 0 for ignore error .IF cs:major != 2 ; If DOS 3.x, set AL = 3 mov al, 3 ; DOS call fails .ENDIF iret CritError ENDP ;* Idle - Interrupt handler for Interrupt 28h (DOS Idle). Allows the ;* original Interrupt 28h service routine to execute. Then checks the ;* request flag TsrRequestFlag maintained either by the keyboard handler ;* (keyboard-activated TSR) or by the timer handler (time-activated TSR). ;* See header comments above for Clock, Keybrd, and MiscServ procedures. ;* ;* If TsrRequestFlag = TRUE and system is in interruptable state, Idle ;* invokes the TSR by calling the Activate procedure. Uses an active flag ;* to prevent the Idle procedure from being reentered while executing. ;* ;* Uses: intIdle and TsrActiveFlag ;* ;* Params: None ;* ;* Return: None Idle PROC FAR pushf ; Simulate interrupt by pushing flags, call cs:intIdle.OldHand ; far-calling old Int 28h routine .IF cs:intIdle.Flag == FALSE; If not already in this handler, mov cs:intIdle.Flag, TRUE ; set active flag sti ; Interrupts are okay push ds ; Save application's DS push cs pop ds ; Set DS to resident code segment ASSUME ds:@code INVOKE CheckRequest ; Check conditions .IF !carry? ; If TSR requested and safe, mov TsrActiveFlag, TRUE ; activate TSR INVOKE Activate mov TsrActiveFlag, FALSE .ENDIF ; End carry flag check mov intIdle.Flag, FALSE ; Clear active flag pop ds ; Recover application's DS .ENDIF ; End in-handler check iret Idle ENDP ;* Multiplex - Handler for Interrupt 2Fh (Multiplex Interrupt). Checks ;* AH for this TSR's identity number. If no match (indicating call is ;* not intended for this TSR), Multiplex passes control to the previous ;* Interrupt 2Fh handler. ;* ;* Params: AH = Handler identity number ;* AL = Function number 0-2 ;* ;* Return: AL = 0FFh (function 0) ;* ES:DI = Pointer to identifier string (function 0) ;* ES:DI = Pointer to resident PSP segment (function 1) ;* ES:DI = Pointer to shared memory (function 2) Multiplex PROC FAR .IF ah != cs:IDnumber ; If this handler not requested, jmp cs:intMultex.OldHand ; pass control to old Int 2Fh .ENDIF ; handler .IF al == 0 ; If function 0 (verify presence), mov al, 0FFh ; AL = 0FFh, push cs ; ES = resident code segment pop es mov di, OFFSET IDstring ; DI = offset of identifier string .ELSEIF al == 1 ; If function 1 (get PSP address), mov es, cs:TsrPspSeg ; ES:DI = far address of resident PSP sub di, di .ELSE les di, cs:ShareAddr ; If function 2 (get shared memory), .ENDIF ; set ES:DI = far address NoMultiplex LABEL FAR ; Secondary entry for null Multiplex iret Multiplex ENDP ;* CheckHotKey - Checks current keystroke for hot key. Called from Keybrd ;* handler if IBM PC/AT or compatible, or from MiscServ handler if PS/2. ;* ;* Uses: HotScan, HotShift, HotMask, and SHFT_STAT ;* ;* Params: AL = Scan code ;* ;* Return: Carry flag set = FALSE; carry flag clear = TRUE CheckHotKey PROC NEAR cmp al, cs:HotScan ; If current scan code isn't code jne e_exit ; for hot key, exit with carry set push es ; Else look into BIOS data area sub ax, ax ; (segment 0) to check shift state mov es, ax mov al, es:[SHFT_STAT] ; Get SHIFT-key flags and al, cs:HotMask ; AND with "don't care" mask cmp al, cs:HotShift ; Compare result with hot SHIFT key pop es je exit ; If match, exit with carry clear e_exit: stc ; Set carry if not hot key exit: ret CheckHotKey ENDP ;* CheckRequest - Checks request flag and system status using the ;* following logic: ;* ;* IF (TsrRequestFlag AND (NOT TsrActiveFlag) ;* AND DosStatus AND HardwareStatus) ;* return TRUE ;* ELSE ;* return FALSE ;* ;* Uses: TsrRequestFlag and TsrActiveFlag ;* ;* Params: DS = Resident code segment ;* ;* Return: Carry flag set = TRUE; carry flag clear = FALSE CheckRequest PROC NEAR rol TsrRequestFlag, 1 ; Rotate high bit into carry - set ; if TRUE (-1), clear if FALSE (0) cmc ; NOT carry .IF !carry? ; If TsrRequestFlag = TRUE: ror TsrActiveFlag, 1 ; Rotate low bit into carry - set ; if TRUE (-1), clear if FALSE (0) .IF !carry? ; If TsrActiveFlag = FALSE: INVOKE CheckDos ; Is DOS in interruptable state? .IF !carry? ; If so, INVOKE CheckHardware ; if hardware or BIOS unstable, .ENDIF ; set carry and exit .ENDIF .ENDIF ret CheckRequest ENDP ;* CheckDos - Checks status of MS-DOS using the following logic: ;* ;* IF (NOT CritErr) AND ((NOT InDos) OR (Idle AND InDos)) ;* return DosStatus = TRUE ;* ELSE ;* return DosStatus = FALSE ;* ;* Uses: CritErrAddr, InDosAddr, and intIdle ;* ;* Params: DS = Resident code segment ;* ;* Return: Carry flag set if MS-DOS is busy CheckDos PROC NEAR USES es bx ax les bx, CritErrAddr mov ah, es:[bx] ; AH = value of CritErr flag les bx, InDosAddr mov al, es:[bx] ; AL = value of InDos flag sub bx, bx ; BH = 0, BL = 0 cmp bl, intIdle.Flag ; Carry flag set if call is from ; Interrupt 28h handler rcl bl, 1 ; Rotate carry into BL: TRUE if Idle cmp bx, ax ; Carry flag clear if CritErr = 0 ; and InDos <= BL ret CheckDos ENDP ;* CheckHardware - Checks status of BIOS and hardware using the ;* following logic: ;* ;* IF HardwareActive OR KeybrdActive OR VideoActive OR DiskIOActive ;* return HardwareStatus = FALSE ;* ELSE ;* return HardwareStatus = TRUE ;* ;* Uses: intKeybrd, intVideo, and intDiskIO ;* ;* Params: DS = Resident code segment ;* ;* Return: Carry flag set if hardware or BIOS is busy CheckHardware PROC NEAR USES ax ; Verify hardware interrupt status by interrogating Intel 8259A ; Programmable Interrupt Controller mov ax, 00001011y ; AL = 0CW3 for Intel 8259A ; (RR = 1, RIS = 1) out 20h, al ; Request 8259A in-service register jmp delay ; Wait a few cycles delay: in al, 20h ; AL = hardware interrupts being cmp ah, al ; serviced (bit = 1 if in service) .IF !carry? ; If no hard interrupts in service, sub al, al ; verify BIOS interrupts not active, cmp al, intKeybrd.Flag ; check Interrupt 09 handler .IF !carry? ; If Int 09 not active, cmp al, intVideo.Flag ; check Interrupt 10h handler .IF !carry? ; If Int 10h not active, cmp al, intDiskIO.Flag ; check Interrupt 13h handler, .ENDIF ; return with carry set if .ENDIF ; Interrupt 09, 10h, or 13h .ENDIF ; is active ret CheckHardware ENDP ;* Activate - Sets up for far call to TSR with the following steps: ;* ;* 1. Stores stack pointer SS:SP and switches to new stack ;* 2. Pushes registers onto new stack ;* 3. Stores vectors for Interrupts 1Bh, 23h, and 23h, and ;* replaces them with addresses of error-trapping handlers ;* 4. Stores DOS CTRL+C checking flag, then turns off checking ;* 5. If required, stores DTA address and switches to new DTA ;* ;* When TSR returns, restores all the above. ;* ;* Uses: Reads or writes the following globals: ;* OldStackAddr, TrapArray, BreakCheckFlag, TsrRequestFlag ;* ;* Params: DS = Resident code segment ;* ;* Return: None Activate PROC NEAR ; Step 1. Set up a new stack mov WORD PTR OldStackAddr[0], sp ; Save current mov WORD PTR OldStackAddr[2], ss ; stack pointer cli ; Turn off interrupts while push cs ; changing stack pop ss ; New stack begins mov sp, OFFSET NewStack ; at LABEL NewStack sti ; Step 2. Preserve registers (DS already saved in Clock or Idle) push ax push bx push cx push dx push si push di push bp push es cld ; Clear direction flag ; Step 3. Set up trapping handlers for keyboard breaks and DOS ; critical errors (Interrupts 1Bh, 23h, and 24h) mov cx, CTRAP ; CX = number of handlers mov si, OFFSET TrapArray ; DS:SI points to trap array .REPEAT mov al, [si] ; AL = interrupt number mov ah, 35h ; Request DOS Function 35h int 21h ; Get interrupt vector (ES:BX) mov WORD PTR [si].INTR.OldHand[0], bx ; Save far address of mov WORD PTR [si].INTR.OldHand[2], es ; application's handler mov dx, WORD PTR [si].INTR.NewHand[0] ; DS:DX points to TSR's hand mov ah, 25h ; Request DOS Function 25h int 21h ; Set interrupt vector add si, SIZEOF INTR ; DS:SI points to next in list .UNTILCXZ ; Step 4. Disable MS-DOS break checking during disk I/O mov ax, 3300h ; Request DOS Function 33h int 21h ; Get CTRL+BREAK flag in DL mov BreakCheckFlag, dl ; Preserve it sub dl, dl ; DL = 0 to disable I/O break checking mov ax, 3301h ; Request DOS Function 33h int 21h ; Set CTRL+BREAK flag from DL ; Step 5. If TSR requires a disk transfer area, store address of current ; DTA and switch buffer address to this segment. See Section 19.5.3 of ; Programmer's Guide for more information about the DTA. IFDEF DTA_SIZ mov ah, 2Fh ; Request DOS Function 2Fh int 21h ; Get DTA Address into ES:BX mov WORD PTR OldDtaAddr[0], bx ; Store address mov WORD PTR OldDtaAddr[2], es mov dx, OFFSET DtaBuff ; DS:DX points to new DTA mov ah, 1Ah ; Request DOS Function 1Ah int 21h ; Set DTA Address ENDIF ; Call main body of TSR. mov ax, @data mov ds, ax ; Initialize DS and ES mov es, ax ; to data segment call cs:TsrAddr ; Call main part of TSR push cs pop ds ; Reset DS to this segment ; Undo step 5. Restore previous DTA (if required) IFDEF DTA_SIZ push ds ; Preserve DS lds dx, OldDtaAddr ; DS:DX points to application's DTA mov ah, 1Ah ; Request DOS Function 1Ah int 21h ; Set DTA Address pop ds ENDIF ; Undo step 4. Restore previous MS-DOS break checking mov dl, BreakCheckFlag ; DL = previous break state mov ax, 3301h ; Request DOS Function 33h int 21h ; Set CTRL+BREAK flag from DL ; Undo step 3. Restore previous vectors for error-trapping handlers mov cx, CTRAP mov di, OFFSET TrapArray push ds ; Preserve DS push ds ; ES = resident code segment pop es .REPEAT mov al, es:[di] ; AL = interrupt number lds dx, es:[di].INTR.OldHand; DS:DX points to application's handler mov ah, 25h ; Request DOS Function 25h int 21h ; Set interrupt vector from DS:DX add di, SIZEOF INTR ; ES:DI points to next in list .UNTILCXZ pop ds ; Undo step 2. Restore registers from stack pop es pop bp pop di pop si pop dx pop cx pop bx pop ax ; Undo step 1. Restore address of original stack to SS:SP cli mov sp, WORD PTR OldStackAddr[0] mov ss, WORD PTR OldStackAddr[2] sti ; Clear request flag and return to caller (Clock or Idle procedure) mov TsrRequestFlag, FALSE ret Activate ENDP ;* INSTALLATION SECTION - The following code is executed only during ;* the TSR's installation phase. When the program terminates through ;* Function 31h, the above code and data remain resident; memory ;* occupied by the following code segment is returned to the operating ;* system. DGROUP GROUP INSTALLCODE INSTALLCODE SEGMENT PARA PUBLIC 'I_CODE' ASSUME ds:@code ;* Install - Prepares for installation of a TSR by chaining interrupt ;* handlers and initializing pointers to DOS flags. Install does not ;* call the Terminate-and-Stay-Resident function. ;* ;* This library of routines accommodates both keyboard-activated and ;* time-activated TSRs. The latter are TSRs that activate at a preset ;* time. If the first parameter (Param1) is a valid scan code, Install ;* assumes the TSR is activated from the keyboard and sets up a keyboard ;* handler to search for the hot key. If Param1 is null, Install assumes ;* the next two parameters (Param2 and Param3) are respectively the hour ;* and minute at which the TSR is to activate. In this case, Install ;* calls GetTimeToElapse to initialize the variable CountDown and sets ;* up KeybrdMonitor as the keyboard handler. CountDown and the secondary ;* counter Tick91 serve here the same functions as they do for the ;* ALARM.ASM program presented in Section 19.3 of the Programmer's Guide. ;* Install is callable from a high-level language. ;* ;* Uses: InDosAddr, CritErrAddr, CHAND, ;* HandArray, CTRAP, TrapArray ;* ;* Keyboard-activated Time-activated ;* ------------------ -------------- ;* Params: Param1 - Scan code for hot key 0 ;* Param2 - Bit value for shift hot key Hour to activate ;* Param3 - Bit mask for shift hot key Minute to activate ;* Param4 - Far address of main TSR procedure (same) ;* ;* Return: AX = 0 if successful, or one of the following codes: ;* IS_INSTALLED FLAGS_NOT_FOUND NO_IDNUM ;* ALREADY_INSTALLED WRONG_DOS Install PROC FAR USES ds si di, Param1:WORD, Param2:WORD, Param3:WORD, Param4:FAR PTR FAR mov ax, @code mov ds, ax ; Point DS to code segment ; Get and store parameters passed from main program module mov al, BYTE PTR Param1 mov HotScan, al ; Store hot-key scan code mov al, BYTE PTR Param2 ; or flag for time activate mov HotShift, al ; Store hot-key shift value mov al, BYTE PTR Param3 ; or hour value mov HotMask, al ; Store hot-key shift mask ; or minute value mov ax, WORD PTR Param4[0] mov bx, WORD PTR Param4[2] mov WORD PTR TsrAddr[0], ax ; Store segment:offset of mov WORD PTR TsrAddr[2], bx ; TSR's main code ; Get addresses of DOS flags, then check for prior installation INVOKE GetDosFlags ; Find DOS service flags or ax, ax jnz exit ; If flags not found, quit sub al, al ; Request multiplex function 0 call CallMultiplex ; Invoke Interrupt 2Fh cmp ax, NOT_INSTALLED ; Check for presence of resident TSR .IF !zero? ; If TSR is installed, cmp ax, IS_INSTALLED ; return with appropriate jne exit ; error code mov ax, ALREADY_INSTALLED jmp exit .ENDIF ; Check if TSR is to activate at the hour:minute specified by Param2:Param3. ; If so, determine the number of 5-second intervals that must elapse before ; activation, then set up the code at the far LABEL KeybrdMonitor to serve ; as the keyboard handler. .IF HotScan == 0 ; If valid scan code given, mov ah, HotShift ; AH = hour to activate mov al, HotMask ; AL = minute to activate call GetTimeToElapse ; Get number of 5-second intervals mov CountDown, ax ; to elapse before activation .ELSE ; Force use of KeybrdMonitor as ; keyboard handler cmp Version, 031Eh ; DOS Version 3.3 or higher? jb setup ; No? Skip next step ; Test for IBM PS/2 series. If not PS/2, use Keybrd and SkipMiscServ as ; handlers for Interrupts 09 and 15h respectively. If PS/2 system, set up ; KeybrdMonitor as the Interrupt 09 handler. Audit keystrokes with MiscServ ; handler, which searches for the hot key by handling calls to Interrupt 15h ; (Miscellaneous System Services). Refer to Section 19.2.1 of the Programmer's ; Guide for more information about keyboard handlers. mov ax, 0C00h ; Function 0Ch (Get System int 15h ; Configuration Parameters) sti ; Compaq ROM may leave interrupts ; disabled jc setup ; If carry set, or ah, ah ; or if AH not 0, jnz setup ; services are not supported test BYTE PTR es:[bx+5], 00010000y ; Test bit 4 to see if jz setup ; intercept is implemented mov ax, OFFSET MiscServ ; If so, set up MiscServ as mov WORD PTR intMisc.NewHand, ax ; Interrupt 15h handler .ENDIF mov ax, OFFSET KeybrdMonitor ; Set up KeybrdMonitor as mov WORD PTR intKeybrd.NewHand, ax ; Interrupt 09 handler ; Interrupt structure is now initialized for either PC/AT or PS/2 system. ; Get existing handler addresses from interrupt vector table, store in ; OldHand member, and replace with addresses of new handlers. setup: mov cx, CHAND ; CX = count of handlers mov si, OFFSET HandArray ; SI = offset of handler structures .REPEAT mov ah, 35h ; Request DOS Function 35h mov al, [si] ; AL = interrupt number int 21h ; Get interrupt vector in ES:BX mov WORD PTR [si].INTR.OldHand[0], bx ; Save far address mov WORD PTR [si].INTR.OldHand[2], es ; of current handler mov dx, WORD PTR [si].INTR.NewHand[0] ; DS:DX points to TSR handler mov ah, 25h ; Request DOS Function 25h int 21h ; Set interrupt vector from DS:DX add si, SIZEOF INTR ; DS:SI points to next in list .UNTILCXZ sub ax, ax ; Clear return code exit: ret ; Return to caller Install ENDP ;* Deinstall - Prepares for deinstallation of a TSR. Deinstall is the ;* complement of the Install procedure. It restores to the vector table ;* the original addresses replaced during installation, thus unhooking ;* the TSR's handlers. Checks to see if another TSR has installed handlers ;* for the interrupts in array HandArray. If so, the procedure fails with ;* an appropriate error code. Callable from a high-level language. ;* ;* Params: None ;* ;* Return: AX = Segment address of resident portion's PSP or ;* one of the following error codes: ;* CANT_DEINSTALL WRONG_DOS Deinstall PROC FAR USES ds si di mov ax, @code mov ds, ax ; Point DS to code segment sub al, al ; Request multiplex function 0 call CallMultiplex ; Get resident code segment in ES cmp ax, IS_INSTALLED ; If not resident, jne exit ; exit with error push es ; Else point DS to pop ds ; resident code segment mov cx, CHAND ; Count of handlers mov si, OFFSET HandArray ; SI points to handler structures ; Read current vectors for TSR's interrupt handlers and compare with far ; addresses. If mismatch, another TSR has installed new handlers and ours ; cannot be safely deinstalled. .REPEAT mov al, [si] ; AL = interrupt number mov ah, 35h ; Request DOS Function 35h int 21h ; Get interrupt vector in ES:BX cmp bx, WORD PTR [si].INTR.NewHand[0] ; If offset different, jne e_exit ; error mov ax, es cmp ax, WORD PTR [si].INTR.NewHand[2] ; If segment different, jne e_exit ; error add si, SIZEOF INTR ; DS:SI points to next in list .UNTILCXZ ; If no interrupts replaced, call TSR's multiplex handler to locate ; address of resident portion's PSP. Although the PSP is not required ; until memory is returned to DOS, the call must be done now before ; unhooking the multiplex handler. mov al, 1 ; Request multiplex function 1 call CallMultiplex ; Get resident code's PSP in ES push es ; Save it ; Unhook all handlers by restoring the original vectors to vector table. mov cx, CHAND ; Count of installed handlers mov si, OFFSET HandArray ; SI points to handler structures .REPEAT mov al, [si] ; AL = interrupt number push ds ; Preserve DS segment lds dx, [si].INTR.OldHand ; Put vector in DS:DX mov ah, 25h ; Request DOS Function 25h int 21h ; Set interrupt vector from DS:DX pop ds add si, SIZEOF INTR ; DS:SI points to next in list .UNTILCXZ pop ax ; Return address of resident PSP jmp exit ; to signal success e_exit: mov ax, CANT_DEINSTALL exit: ret Deinstall ENDP ;* GetVersion - Gets the DOS version and stores it in a global variable as ;* well as returning it in AX. ;* ;* Uses: Version ;* ;* Params: DS = Resident code segment ;* ;* Return: AH = Major version ;* AL = Minor version GetVersion PROC NEAR mov ax, 3000h ; Request DOS Function 30h int 21h ; Get MS-DOS version number .IF al < 2 ; If Version 1.x: mov ax, WRONG_DOS ; Abort with WRONG_DOS as error code .ELSE xchg ah, al ; AH = major, AL = minor version mov Version, ax ; Save in global .ENDIF ret GetVersion ENDP ;* GetDosFlags - Gets pointers to the DOS InDos and Critical Error flags. ;* ;* Params: DS = Resident code segment ;* ;* Return: 0 if successful, or the following error code: ;* FLAGS_NOT_FOUND GetDosFlags PROC NEAR ; Get InDOS address from MS-DOS mov ah, 34h ; Request DOS Function 34h int 21h ; Get Address of InDos flag mov WORD PTR InDosAddr[0], bx ; Store address (ES:BX) mov WORD PTR InDosAddr[2], es ; for later access ; Determine address of Critical Error Flag mov ax, Version ; AX = DOS version number ; If DOS 3.1 or greater and not OS/2 compatibility mode, Critical Error ; flag is in byte preceding InDOS flag .IF (ah < 10) && (ah >= 3) && (al >= 10) dec bx ; BX points to byte before InDos flag .ELSE ; For earlier versions, the only reliable method is to scan through ; DOS to find an INT 28h instruction in a specific context. mov cx, 0FFFFh ; Maximum bytes to scan sub di, di ; ES:DI = start of DOS segment INT_28 EQU 028CDh .REPEAT mov ax, INT_28 ; Load opcode for INT 28h .REPEAT repne scasb ; Scan for first byte of opcode .IF !zero? mov ax, FLAGS_NOT_FOUND ; Return error if not found jmp exit .ENDIF .UNTIL ah == es:[di] ; For each matching first byte, ; check the second byte until match ; See if INT 28h is in this context: ; ; (-7) (-5) ; CMP ss:[CritErrFlag], 0 ; 36, 80, 3E, ?, ?, 0 ; JNE NearLabel ; 75, ? int 28h ; CD, 28 ; ; (0) (1) CMP_SS EQU 3E80h P_CMP_SS EQU 8 P_CMP_OP EQU 6 mov ax, CMP_SS ; Load and compare opcode to CMP .IF ax == es:[di-P_CMP_SS] ; If match: mov bx, es:[di-P_CMP_OP] ; BX = offset of jmp exit ; Critical Error flag .ENDIF ; See if INT 28h is in this context: ; ; (-12) (-10) ; TEST ?s:[CritErr], 0FFh ; ?6 F6, 06, ?, ?, FF ; JNE NearLabel ; 75, ? ; PUSH ss:[CritErrFlag] ; 36, FF, 36, ?, ? int 28h ; CD, 28 ; ; (0) (1) TEST_SS EQU 06F6h P_TEST_SS EQU 13 P_TEST_OP EQU 11 mov ax, TEST_SS ; Load AX = opcode for TEST .UNTIL ax == es:[di-P_TEST_SS] ; If not TEST, continue scan mov bx, es:[di-P_TEST_OP] ; Else load BX with offset of .ENDIF ; Critical Error flag exit: mov WORD PTR CritErrAddr[0], bx ; Store address of mov WORD PTR CritErrAddr[2], es ; Critical Error flag sub ax, ax ; Clear error code ret GetDosFlags ENDP ;* GetTimeToElapse - Determines number of 5-second intervals that ;* must elapse between specified hour:minute and current time. ;* ;* Params: AH = Hour ;* AL = Minute ;* ;* Return: AX = Number of 5-second intervals GetTimeToElapse PROC NEAR push ax ; Save hour:minute mov ah, 2Ch ; Request DOS Function 2Ch int 21h ; Get Time (CH:CL = hour:minute) pop bx ; Recover hour:minute mov dl, dh sub dh, dh push dx ; Save DX = current seconds mov al, 60 ; 60 minutes/hour mul bh ; Multiply by specified hour sub bh, bh add bx, ax ; BX = minutes from midnight ; to activation time mov al, 60 ; 60 minutes/hour mul ch ; Multiply by current hour sub ch, ch add ax, cx ; AX = minutes from midnight ; to current time sub bx, ax ; BX = minutes to elapse before .IF carry? ; If activation is tomorrow, add bx, 24 * 60 ; add number of minutes per day .ENDIF mov ax, 60 mul bx ; DX:AX = minutes-to-elapse-times-60 pop bx ; Recover current seconds sub ax, bx ; DX:AX = seconds to elapse before sbb dx, 0 ; activation .IF carry? ; If negative, mov ax, 5 ; assume 5 seconds cwd .ENDIF mov bx, 5 ; Divide result by 5 seconds div bx ; AX = number of 5-second intervals ret GetTimeToElapse ENDP ;* CallMultiplex - Calls the Multiplex Interrupt (Interrupt 2Fh). ;* ;* Uses: IDstring ;* ;* Params: AL = Function number for multiplex handler ;* ;* Return: AX = One of the following return codes: ;* NOT_INSTALLED IS_INSTALLED NO_IDNUM ;* ES:DI = Resident code segment:identifier string (function 0) ;* ES:DI = Resident PSP segment address (function 1) ;* ES:DI = Far address of shared memory (function 2) CallMultiplex PROC FAR USES ds push ax ; Save function number mov ax, @code mov ds, ax ; Point DS to code segment ; First, check 2Fh vector. DOS Version 2.x may leave the vector null ; if PRINT.COM is not installed. If vector is null, point it to IRET ; instruction at LABEL NoMultiplex. This allows the new multiplex ; handler to pass control, if necessary, to a proper existing routine. mov ax, 352Fh ; Request DOS Function 35h int 21h ; Get interrupt vector in ES:BX mov ax, es or ax, bx .IF zero? ; If Null vector, mov dx, OFFSET NoMultiplex ; set vector to IRET instruction mov ax, 252Fh ; at LABEL NoMultiplex int 21h ; Set interrupt vector .ENDIF ; Second, call Interrupt 2Fh with function 0 (presence request). Cycle ; through allowable identity numbers (192 to 255) until TSR's multiplex ; handler returns ES:DI = IDstring to verify its presence or until call ; returns AL = 0, indicating the TSR is not installed. mov dh, 192 ; Start with identity number = 192 .REPEAT mov ah, dh ; Call Multiplex with AH = trial ID sub al, al ; and AL = function 0 push dx ; Save DH and DS in case call push ds ; destroys them int 2Fh ; Multiplex pop ds ; Recover DS and pop dx ; current ID number in DH or al, al ; Does a handler claim this ID number? jz no ; If not, stop search .IF al == 0FFh ; If handler ready to process calls, mov si, OFFSET IDstring ; point DS:SI to ID string, compare mov cx, IDstrlen ; with string at ES:DI returned repe cmpsb ; by multiplex handler je yes ; If equal, TSR's handler is found .ENDIF inc dh ; This handler is not the one .UNTIL zero? ; Try next identity number up to 255 mov ax, NO_IDNUM ; In the unlikely event that numbers jmp e_exit ; 192-255 are all taken, quit ; Third, assuming handler is found and verified, process the multiplex ; call with the requested function number. yes: pop ax ; AL = original function number mov ah, dh ; AH = identity number int 2Fh ; Multiplex mov ax, IS_INSTALLED ; Signal that handler has been found jmp exit ; and quit ; Reaching this section means multiplex handler (and TSR) not installed. ; Since the value in DH is not claimed by any handler, it will be used as ; the resident TSR's identity number. Save the number in resident code ; segment so multiplex handler can find it. no: mov IDnumber, dh ; Save multiplex identity number mov ax, NOT_INSTALLED ; Signal handler is not installed e_exit: pop bx ; Remove function number from stack exit: ret CallMultiplex ENDP ;* InitTsr - Initializes DOS version variables and multiplex data with ;* following parameters. This procedure must execute before calling ;* either the Install, Deinstall, or CallMultiplex procedures. Callable ;* from a high-level language. ;* ;* Uses: IDstring ;* ;* Params: PspParam - Segment address of PSP ;* StrParam - Far address of TSR's identifier string ;* ShrParam - Far address of shared memory ;* ;* Return: AX = WRONG_DOS if not DOS Version 2.0 or higher InitTsr PROC FAR USES ds es si di, PspParam:WORD, StrParam:FPVOID, ShrParam:FPVOID mov ax, @code mov ds, ax ; Point DS and ES mov es, ax ; to code segment ; Get and store parameters passed from main program module mov ax, PspParam mov TsrPspSeg, ax ; Store PSP segment address mov ax, WORD PTR ShrParam[0] mov bx, WORD PTR ShrParam[2] mov WORD PTR ShareAddr[0], ax ; Store far address of mov WORD PTR ShareAddr[2], bx ; shared memory push ds mov si, WORD PTR StrParam[0] ; DS:SI points to multiplex mov ax, WORD PTR StrParam[2] ; identifier string mov ds, ax mov di, OFFSET IDstring ; Copy string to IDstring mov cx, STR_LEN ; at ES:DI so multiplex ; handler has a copy .REPEAT lodsb ; Copy STR_LEN characters .BREAK .IF al == 0 ; or until null terminator stosb ; found .UNTILCXZ pop ds ; Recover DS = code segment mov ax, STR_LEN sub ax, cx mov IDstrlen, ax ; Store string length INVOKE GetVersion ; Return AX = version number ret ; or WRONG_DOS InitTsr ENDP INSTALLCODE ENDS END