tsrkey.asm

一个关于内存驻留的汇编源代码

; own code is not re-entered. (The "bellgate" stuff below is an example
; of a measure necessary to keep us from re-entering our own TSR's code).
; What we really want to do by allowing interrupts is to make the CPU avail-
; able to OTHER critical interrupt service routines WITHOUT swarming all over 
; ourselves through multiple detections of our own HotKey.
;               This "gate" technique is a good one to keep in
;               mind whenever you have a code region in an interrupt handler
;               that needs to be protected from re-entry:
;
                cmp     bellgate,0      ;Is it clear to re-enter Hotkey code?
                jne     Exit09          ;Exit if not,
                mov     bellgate,1      ;Else, close gate and proceed.
;
                STI                     ;Allow other interrupts in our TSR.
;
                call    ROUTINE         ;All is clear!, so call routine.
;
                mov     CS:bellgate,0   ;Open gate allowing new HotKey detect.
;
Exit09:
                pop     es              ;Restore all registers
                pop     ds
                ASSUME  DS:NOTHING      ;v0.01
                pop     bp
		pop	di
		pop	si
		pop	dx
		pop	cx
		pop	bx
		pop	ax
;
;
;	Return from this TSR's Keyboard Interrupt 09h handler routine:
		iret
;
NewInt09	ENDP			;v0.01
;
;*************************************************************************
;
;	-END OF TSR's RESIDENT CODE-
;	Only the code above will remain locked in memory
;		after the initialization performed below.
;*************************************************************************
SUBTTL  TSR Initialization Code (Nonresident). The "BOOSTER".
PAGE
;*************************************************************************
;       BEGINNING OF TSR's INITIALIZATION CODE:
;	The following code is protected in RAM *ONLY* during initialization
;		of the TSR that occurs when the TSR name is first entered
;		at the DOS command level. All the following code is abandonned
;		unprotected in RAM after the Terminate-and-Stay-Resident
;		call to Function 31h of DOS Interrupt 21h below. This
;		is allowed to happen because the code's work is complete at
;		that point. The code will be overwritten as the memory which
;		it temporarily occupied is needed by DOS for other purposes.
;		 I have seen this following section of code colorfully called
;		the TSR "Booster". And this is quite appropriate since the code
;		sits here, strapped to the very end of the code. It is of use
;		only during the initialization of the TSR, when it is used to
;		put the TSR into "orbit" (residency), and after which it is
;		"jettisoned" by the DOS TSR call, Int 21h, Fcn 31h.
;                                                                              
TSRinit         PROC    NEAR                            ;v0.11
EndDump         EQU     $       ;From Roy Silvernail. Keeps TASM v.1.0 happy.
;
; TSRKEY requires DOS Version 2 or later. Be sure DOS Version 1 not used:
;
;       Get DOS Version Number:
                mov     ah,30h                  ;Fcn 30h = Get DOS Version
                int     21h                     ;DOS Version = al.ah
;
;       If this is DOS v.1.x, this TSR cannot work, so go print message
;       and exit without installing:
                cmp     al,1         ;Is this DOS Version 1.x?
                ja      DOSverOK     ;If not, DOS version is OK.
;
DOSver1:
;If here, DOS Version 1.x is being run and TSR won't work, so bail out:
;
		mov	dx,OFFSET BailOutMsg	;TBONES needs DOS 2.x or later.
		mov	ah,09h			;Say we're sorry, but NO GO
		int	21h			;via DOS.
                pop     bx                      ;Clear stack.
		int	20h			;Terminate without installing
						;in only way DOS 1.x knows.
;
BailOutMsg:
                db      0Dh,0Ah
                db      'Sorry. TSRBONES needs DOS v.2+. You have v.1.x'
                db      0Dh,0Ah,'$'
;
DOSverOK:
;       If here, DOS version is 2.0 or later. TSR can work, so proceed.
;
;       To conserve RAM usage, release from memory the copy of the DOS 
;	Environment passed to this TSR (this assumes, of course, that
;	your Interrupt handler routine will not need to reference this
;	de-allocated Environment):
;
		mov	ES,envseg		;ES=PSP's environment seg v0.11
		mov	ah,49h			;DOS Fcn 49h = Release Memory
		int	21h			;Release it via DOS interrupt.
;
; In order to make the TSR's command name show under the "owner" column in 
;	the "MAPMEM" command of Kim Kokkonen's excellent TSR Mark/Release 
;       package, allocate a tiny 1-paragraph "Pseudo-Environment" here which
;       contains nothing but the TSR name. This costs only 16 bytes in
;       TSR resident code.
;
; Allocate the memory needed by the tiny 'Pseudo-Environment":
		mov	bx,1			;Allocate one parag. (16bytes)
		mov	ah,48h			;and return allocation
		int	21h			;segment in ax via DOS call.
;
                mov     ES,ax                   ;Pseudo-Env. Segment to ES.
		mov	si,OFFSET PseudoEnv	;si=source string OFFSET.
		mov	di,0			;di=destination string OFFSET.
		mov	cx,ENVLNGTH		;cx=Bytes in Pseudo-Env.string.
		cld				;Forward string move direction.
		rep	movsb	;Move Pseudo-Env. string @ DS:si to ES:di
;
; Set PSP's Environment segment pointer to point to tiny Pseudo-Environment.
		mov	envseg,ES	
;
;*****************************************************************************
; Hook Interrupt 09h vector:
;
;       Get Old Interrupt Vector:
                mov     ax,3500H+HOOK09         ;Get Hooked interrupt vec v0.11
		int	21h			;Int.Vector in ES:BX via DOS.
;
;	Save Old Interrupt Vector:
                mov     Word Ptr oldint09,bx      ;Save Offset of Old Interrupt.
                mov     word ptr oldint09+2,ES    ;save segment           v0.11
;
;       Install New Interrupt Vector to this TSR's "NewInt09:" Label:
                mov     ax,2500H+HOOK09         ;Set Hooked int vector v0.11
                mov     dx,offset NewInt09      ;dx=Offset of New Int Handler.
		int	21h			;Set New Int via DOS.
;
; Announce the TSR's Installation:
		mov	dx,Offset InstallMsg	;DX points to message.
		mov	ah,09h			;DOS Fcn. 09h=Display String.
		int	21h			;Display String via DOS.
;
; Lock resident code in memory via Terminate-and-Stay-Resident (TSR) DOS call:
;
;v0.11	DX requires size of resident code (in 16-byte paragraphs)
;	This awkward construct is required to keep
;	DOS Function 31h happy.  Notice how we first compute
;	the length of the TSR code in bytes [i.e., end of
;	the TSR code (TSRinit) minus start of the TSR code
;	(0, our CodeSeg)], round it up to the next whole paragraph ( + 0Fh),
;	and then divide by 16 (SHR 4) to get the number of resident paragraphs:
;
;       Roy Silvernail discovered that the EndDump and BeginDump constants
;       kept his TASM 1.0 assembler happy on the following statement:
                mov     dx,(EndDump-BeginDump+0FH)/16   ;v0.11
;
		mov	ah,31h			;DOS FCN 31h=TSR Call.
		int	21h			;Go Resident via DOS TSR call.
;
PseudoEnv:      DB      ' ',0,0,1,0,'TSRKEY',0
ENVLNGTH	EQU	$-PseudoEnv
;
InstallMsg:
		db	0Dh,0Ah
		db	'YOUR HOT KEY TSR IS NOW INSTALLED.'
		db	0Dh,0Ah
                db      'HotKey => Ctrl-Alt-K'
		db	0Dh,0Ah
		db	0Dh,0Ah
                db      'TSRKEY Version 0.4'
		db	0Dh,0Ah
                db      'Copyright (C) 1990, 1991 by Robert Curtis Davis'
		db	0Dh,0Ah,'$'
;
TSRinit	ENDP					;v0.11

CodeSeg		ends
		end	Entry
;
;******************************************************************************