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Assembly Source File | 1988-04-26 | 17.8 KB | 432 lines

PAGE 60,132 ;============================================================================= ; STAYDOWN holds the CTRL, ALT, and SHIFT keys temporarily toggled on, ; allowing keystroke combinations to be entered with sequential rather ; than simultaneous keypresses. Syntax is: ; ; STAYDOWN [/D | /U] ; ; where /D disables the program until it is run again from the ; command line, and /U uninstalls it. ;============================================================================= KBDATA EQU 60H ;Keyboard data port KBCTRL EQU 61H ;Keyboard control port ALT EQU 38H ;Scan code for ALT key CTRL EQU 1DH ;Scan code for CTRL key LSHIFT EQU 2AH ;Scan code for left SHIFT key RSHIFT EQU 36H ;Scan code for right SHIFT key CR EQU 0DH LF EQU 0AH ;============================================================================= ;BIOS Data Area ;============================================================================= BIOS_DATA SEGMENT AT 40H ORG 17H SHIFT_STATE_1 DB ? ;Primary shift state byte SHIFT_STATE_2 DB ? ;Left CTRL/ALT (bits 0, 1) ORG 96H SHIFT_STATE_3 DB ? ;Right CTRL/ALT (bits 2, 3) BIOS_DATA ENDS ;============================================================================= ;Code Segment (code and data) ;============================================================================= CODE SEGMENT PARA PUBLIC 'CODE' ASSUME CS:CODE, DS:CODE, ES:CODE, SS:CODE ORG 100H BEGIN: JMP INITIALIZE PROGRAM DB "STAYDOWN 1.0 (c) 1988 Ziff Communications Co.",CR,LF AUTHOR DB "PC Magazine ",254," Jeff Prosise",CR,LF,"$",1AH CHECKFLAG DB ? ;Enable/disable flag RESTORE_FLAG DB 0 ;Break code ignored flag LAST_SCAN_CODE DB 0 ;Last scan code EO_FLAG DB 0 ;80h = last code was E0h KB_VECTOR DB 15H ;Vector altered to trap keys BIOS_ISR LABEL DWORD OLD_VECTOR DW 2 DUP (?) ;Old interrupt 9/15h vector ;----------------------------------------------------------------------------- ;INT9H handles interrupt 9 on machines that lack interrupt 15h keyboard ;processing facilities. ;----------------------------------------------------------------------------- INT9H PROC FAR ASSUME CS:CODE, DS:NOTHING, ES:NOTHING, SS:NOTHING CMP CS:CHECKFLAG,0 ;Exit to BIOS if program JE PASS_TO_BIOS ; isn't currently enabled STI ;Interrupts on PUSH AX IN AL,KBDATA ;Read scan code from keyboard CALL MAIN ;Perform internal processing JNC RESET_KEYBOARD ;Ignore scan code if CF = 0 POP AX PASS_TO_BIOS: JMP CS:BIOS_ISR ;Jump to BIOS int handler RESET_KEYBOARD: IN AL,KBCTRL ;Reset the keyboard MOV AH,AL OR AL,80H OUT KBCTRL,AL MOV AL,AH OUT KBCTRL,AL CLI MOV AL,20H ;Signal EOI to interrupt OUT 20H,AL ; controller STI POP AX IRET ;Exit without processing INT9H ENDP ;----------------------------------------------------------------------------- ;INT15H handles interrupt 15h on machines with an extended BIOS. ;----------------------------------------------------------------------------- INT15H PROC FAR ASSUME CS:CODE, DS:NOTHING, ES:NOTHING, SS:NOTHING CMP AH,4FH ;Exit to BIOS handler if JNE EXIT_TO_BIOS ; function code <> 4Fh STI ;Interrupt on CMP CS:CHECKFLAG,0 ;Process scan code as normal JE PROCESS_SCAN_CODE ; if program is disabled CMP AL,0E0H ;Set flag and terminate if JNE NOT_EO ; scan code = E0h MOV CS:EO_FLAG,80H JMP SHORT PROCESS_SCAN_CODE NOT_EO: CMP CS:EO_FLAG,0 ;Branch if E0 flag not set JE CHECK_CODE CMP AL,2AH ;If this scan code is part of JE RESET_EO_FLAG ; a 4-code sequence, then CMP AL,0AAH ; reset E0 flag and process JE RESET_EO_FLAG ; the scan code CMP AL,36H JE RESET_EO_FLAG CMP AL,0B6H JNE CHECK_CODE RESET_EO_FLAG: MOV CS:EO_FLAG,0 ;Reset flag JMP SHORT PROCESS_SCAN_CODE ;Process the scan code CHECK_CODE: PUSH AX CALL MAIN ;Perform internal processing MOV CS:EO_FLAG,0 POP AX RET 2 ;Return with flags intact PROCESS_SCAN_CODE: STC ;Set CF for BIOS processing RET 2 ;Return with flags intact EXIT_TO_BIOS: JMP CS:BIOS_ISR ;Pass to BIOS for processing INT15H ENDP ;----------------------------------------------------------------------------- ;MAIN is called by the two interrupt handling routines to process a keystroke. ;Entry: AL - scan code ;----------------------------------------------------------------------------- MAIN PROC NEAR ASSUME CS:CODE, DS:NOTHING, ES:NOTHING, SS:NOTHING TEST AL,80H ;Branch on break code JNZ BREAK_CODE ; ;Process a make code by simply saving the scan code. ; OR AL,CS:EO_FLAG ;Save E0h indicator MOV CS:LAST_SCAN_CODE,AL ;Save make code STC ;Exit with CF = 1 RET ; ;A break code was received. ; BREAK_CODE: CMP CS:RESTORE_FLAG,0 ;Branch if shift bits are JNE RESTORE_SHIFT_BYTES ; out of sync AND AL,7FH ;Strip break bit OR AL,CS:EO_FLAG ;Add E0h indicator CMP AL,CS:LAST_SCAN_CODE ;Branch if the key released JE CHECK_FOR_SHIFT ; was the last one pressed PROCESS_BREAK: MOV LAST_SCAN_CODE,0 ;Process break code as normal STC RET ; ;Ignore the break if the key just released was a shift key. ; CHECK_FOR_SHIFT: CMP AL,ALT ;Check codes for ALT, CTRL, JE IGNORE_BREAK ; and SHIFT keys CMP AL,ALT+80H JE IGNORE_BREAK CMP AL,CTRL JE IGNORE_BREAK CMP AL,CTRL+80H JE IGNORE_BREAK CMP AL,LSHIFT JE IGNORE_BREAK CMP AL,RSHIFT JNE PROCESS_BREAK IGNORE_BREAK: MOV CS:RESTORE_FLAG,AL ;Ignore the break code MOV CS:LAST_SCAN_CODE,0 CLC ;Return with CF = 0 RET ; ;Reset the BIOS shift bit(s) corresponding to the last key release ignored. ; RESTORE_SHIFT_BYTES: MOV AL,CS:RESTORE_FLAG ;Recover ignored scan code MOV CS:RESTORE_FLAG,0 ;Reset flag PUSH ES ;Point ES to BIOS data area PUSH AX MOV AX,40H MOV ES,AX POP AX CMP AL,RSHIFT ;Reset a single bit if JNE NOT_RSHIFT ; right SHIFT key was AND ES:[SHIFT_STATE_1],0FEH ; released JMP SHORT END_RESTORE NOT_RSHIFT: CMP AL,LSHIFT ;Likewise for left SHIFT JNE NOT_LSHIFT AND ES:[SHIFT_STATE_1],0FDH JMP SHORT END_RESTORE NOT_LSHIFT: CMP AL,CTRL+80H ;Reset right CTRL key bit JNE NOT_RCTRL AND ES:[SHIFT_STATE_3],0FBH JMP SHORT FIX_PRIMARY_SHIFT NOT_RCTRL: CMP AL,CTRL ;Reset two left CTRL bits JNE NOT_LCTRL AND ES:[SHIFT_STATE_1],0FBH AND ES:[SHIFT_STATE_2],0FEH TEST ES:[SHIFT_STATE_3],10H ;Branch for further processing JZ END_RESTORE ; if this is a 101-key JMP SHORT FIX_PRIMARY_SHIFT ; keyboard NOT_LCTRL: CMP AL,ALT+80H ;Reset right ALT bit JNE NOT_RALT AND ES:[SHIFT_STATE_3],0F7H JMP SHORT FIX_PRIMARY_SHIFT NOT_RALT: AND ES:[SHIFT_STATE_1],0F7H ;Reset two left ALT bits AND ES:[SHIFT_STATE_2],0FDH TEST ES:[SHIFT_STATE_3],10H ;Test for 101-key keyboard JZ END_RESTORE ;Branch if it's not FIX_PRIMARY_SHIFT: MOV AH,ES:[SHIFT_STATE_2] ;Set CTRL/ALT bits in primary SHL AH,1 ; shift state byte if either SHL AH,1 ; left or right CTRL/ALT is OR AH,ES:[SHIFT_STATE_3] ; pressed AND AH,0CH AND ES:[SHIFT_STATE_1],0F3H OR ES:[SHIFT_STATE_1],AH END_RESTORE: POP ES JMP PROCESS_BREAK ;Process the break code MAIN ENDP ;----------------------------------------------------------------------------- ;INITIALIZE installs the program into memory. ;----------------------------------------------------------------------------- HEADMSG DB CR,LF,"STAYDOWN: $" ERRMSG1 DB "Usage: STAYDOWN [/D][/U]",CR,LF,"$" ERRMSG2 DB "Not Installed",CR,LF,"$" ERRMSG3 DB "Cannot Uninstall",CR,LF,"$" ERRMSG4 DB "Uninstall Error",CR,LF,"$" CONFIRM_MSG1 DB "Disabled",CR,LF,"$" CONFIRM_MSG2 DB "Uninstalled",CR,LF,"$" CONFIRM_MSG3 DB "Activated",CR,LF,"$" INSTALL_FLAG DB 0 INITIALIZE PROC NEAR ASSUME CS:CODE,DS:CODE,ES:CODE,SS:CODE ; ;See if STAYDOWN is already installed. ; CLD ;Clear DF NOT WORD PTR [BEGIN] ;Initialize fingerprint XOR BX,BX ;Initialize segment values MOV AX,CS ASSUME ES:NOTHING INIT1: INC BX ;Advance to next segment MOV ES,BX CMP AX,BX ;End search if we loop back JE PARSE ; to the current segment MOV SI,OFFSET BEGIN ;Check for ASCII fingerprint MOV DI,SI MOV CX,16 REPE CMPSB JNE INIT1 ;Loop if not found MOV INSTALL_FLAG,1 ;Program is already installed ; ;Parse the command line for a /D or /U parameter. ; PARSE: MOV SI,81H ;Point DS:SI to command line PARSE1: CMP BYTE PTR [SI],32 ;Advance to first non-space JNE PARSE2 INC SI JMP SHORT PARSE1 PARSE2: CMP BYTE PTR [SI],CR ;End-of-line? JE INSTALL ;Yes, then install/enable AND BYTE PTR [SI+1],0DFH ;Capitalize entry CMP WORD PTR [SI],442FH ;Qualifier /D? JE DISABLE ;Yes, then disable program CMP WORD PTR [SI],552FH ;Qualifier /U? JE UNINSTALL ;Yes, then uninstall program MOV AL,1 ;Error code MOV DX,OFFSET ERRMSG1 ;Error message address ERROR_EXIT: PUSH AX ;Save registers PUSH DX MOV DX,OFFSET HEADMSG ;Display prologue MOV AH,9 INT 21H POP DX ;Display error MOV AH,9 INT 21H POP AX ;Error code MOV AH,4CH ;Terminate with ERRORLEVEL set INT 21H ; ;Disable STAYDOWN if a copy is present in memory. ; DISABLE: CMP INSTALL_FLAG,1 ;Error if not installed JE DISABLE2 MOV AL,2 MOV DX,OFFSET ERRMSG2 ;Initialize error pointer JMP ERROR_EXIT DISABLE2: MOV ES:[CHECKFLAG],0 ;Clear CHECKFLAG byte MOV DX,OFFSET CONFIRM_MSG1 ;Print confirmation message CONFIRM_AND_EXIT: PUSH DX MOV DX,OFFSET HEADMSG MOV AH,9 INT 21H POP DX MOV AH,9 INT 21H MOV AX,4C00H ;Exit with ERRORLEVEL = 0 INT 21H ; ;Uninstall STAYDOWN if a copy is present in memory. ; UNINSTALL: CMP INSTALL_FLAG,1 ;Error if not installed JE UNINSTALL2 MOV AL,3 MOV DX,OFFSET ERRMSG2 ;Initialize error pointer JMP ERROR_EXIT UNINSTALL2: CALL REMOVE ;Uninstall the program JNC UNINSTALL3 MOV AL,4 JMP ERROR_EXIT UNINSTALL3: MOV DX,OFFSET CONFIRM_MSG2 ;Print confirmation message JMP SHORT CONFIRM_AND_EXIT ;And exit ; ;Install the program if it isn't already installed, or enable it if it is. ; INSTALL: MOV ES:[CHECKFLAG],1 ;Set enable byte CMP INSTALL_FLAG,1 ;Branch if not installed JNE INSTALL1 MOV DX,OFFSET CONFIRM_MSG3 ;Print confirmation message JMP SHORT CONFIRM_AND_EXIT ;And exit INSTALL1: MOV AH,0C0H ;Check for BIOS support of INT 15H ; extended functions MOV DX,OFFSET INT15H JNC INSTALL2 ;Branch if support is there MOV KB_VECTOR,9 ;Use int 9 rather than 15h MOV DX,OFFSET INT9H ;Point DX to int 9 routine INSTALL2: MOV AH,35H ;Save current vector MOV AL,KB_VECTOR INT 21H MOV OLD_VECTOR,BX MOV OLD_VECTOR[2],ES MOV AH,25H ;Then point it to internal MOV AL,KB_VECTOR ; interrupt handler INT 21H MOV AX,DS:[2CH] ;Get environment segment MOV ES,AX ; address from PSP MOV AH,49H ;Then deallocate environment INT 21H ; space reserved by DOS MOV AH,9 ;Print installation message MOV DX,OFFSET PROGRAM INT 21H MOV AX,3100H ;Terminate but remain resident MOV DX,(OFFSET INITIALIZE-OFFSET CODE+15) SHR 4 INT 21H INITIALIZE ENDP ;----------------------------------------------------------------------------- ;REMOVE deallocates the memory block addressed by ES and restores the ;Interrupt vector displaced on installation. ;----------------------------------------------------------------------------- REMOVE PROC NEAR PUSH ES ;Get current interrupt 9/15h MOV AH,35H ; vector and see if STAYDOWN MOV AL,ES:[KB_VECTOR] ; still owns it INT 21H MOV BX,ES POP ES MOV AX,ES CMP BX,AX ;Program cannot be uninstalled JE RESTORE_VECTOR ; if interrupt 9/15h vector MOV DX,OFFSET ERRMSG3 ; has been grabbed away STC ;Return with CF = 1 for error RET RESTORE_VECTOR: PUSH DS ;Restore displaced interrupt ASSUME DS:NOTHING ; vector LDS DX,ES:[BIOS_ISR] MOV AH,25H MOV AL,ES:[KB_VECTOR] INT 21H POP DS ASSUME DS:CODE NOT WORD PTR ES:[BEGIN] ;Remove fingerprint MOV AH,49H ;Free memory given to INT 21H ; original program block MOV DX,OFFSET ERRMSG4 ;Initialize error pointer RET ;Exit with CF intact REMOVE ENDP CODE ENDS END BEGIN