Simtel MSDOS 1992 June/SIMTEL_0692.cdr/msdos/screen/drip21.arc/DRIP21.ASM

Assembly Source File | 1988-09-22 | 4.2 KB | 204 lines

TITLE    DRIP    5-26-87    [4-21-88]

;Toad Hall disassy, tweak
;Goes TSR, activate/toggle with Scroll Lock key.
;Characters randomly drip down/off the screen

LF    EQU    0AH
CR    EQU    0DH
;

Cseg    SEGMENT
    ASSUME DS:Cseg, SS:Cseg ,CS:Cseg ,ES:Cseg
    ORG    100H


Drip    proc    near
    JMP    Start

int8Vec    dd    0            ;save old Int 8 vector
saveDI    dw    0
saveSI    dw    0

video    dw    0B000H            ;default mono screen memory

wcntr_13A    dw    40H        ;counter
byte_13C    DB    0FFH
bflag_13D    DB    0
bcntr_13E    DB    0
bflag_13F    DB    0
bcntr_140    DB    0
word_2BE    dw    0
Drip    endp


NewInt8    proc    far
    ASSUME    DS:Nothing

    PUSHF                ;save user's flags
    PUSH    AX            ;and his Int 8 request
    MOV    AH,2            ;get shift status
    INT    16H
    AND    AL,10H            ;mask for Scroll Lock key
    JZ    Continue_Int8        ; continue to Int 8
    CMP    CS:bcntr_13E,0        ;counter zeroed?
    JZ    L01A0            ; yep, time to act
     DEC    CS:bcntr_13E        ;decr counter
     JMP    SHORT    Continue_Int8

L01A0:    CMP    CS:bflag_13D,0        ;flag set?
    JNZ    Continue_Int8        ; yep, just continue to Int 8
     JMP    SHORT    L01B2        ;time to act

Continue_Int8:
    POP    AX            ;restore user's Int 8 svc
    POPF                ;restore user's flags
    JMP    CS:int8Vec        ;jump to old Int 8

L01B2:    PUSHF                ;save flags
    CALL    CS:int8Vec        ;call old Int 8
    PUSH    ES            ;save all his regs
    PUSH    DS
    PUSH    DX
    PUSH    CX
    PUSH    DI
    PUSH    SI
    mov    ax,CS
    mov    DS,ax
    ASSUME    DS:Cseg

    MOV    AX,video
    MOV    ES,AX
    ASSUME    ES:Nothing

    cmp    bflag_13F,0        ;flag clear?
    JZ    L01D9            ; yep
     MOV    DI,saveDI        ;get our screen pointers
     MOV    SI,saveSI
     STI                ;enable ints
     JMP    SHORT    MoveChar    ;go to work

L01D9:    MOV    bflag_13D,0FFH        ;set flag
    STI                ;enable interrupts
    MOV    bcntr_140,64H        ;refresh counter
Lup1E4:    CMP    bcntr_140,0        ;zeroed out?
    JNZ    L01EE            ; nope
     JMP    Pop_Iret        ; return

L01EE:    DEC    bcntr_140        ;count down
    CALL    L02AC
    AND    AX,0FFEH
    MOV    SI,AX
    MOV    AL,ES:[SI]
    CMP    AL,20H            ;just a space?
    JZ    Lup1E4            ; yep, try again
    or    al,al            ;just a zero?
    JZ    Lup1E4            ; yep, try again
    CMP    SI,0FA0H        ;screen bottom?
    JNB    Lup1E4            ; not yet, try again
    MOV    DI,SI            ;point to new char location
    ADD    DI,0A0H            ;move this far each time (1 line)
    CMP    DI,0FA0H        ;screen bottom?
    JNB    L025B            ;not yet, continue
    MOV    AL,ES:[DI]        ;get char at new location
    CMP    AL,20H            ;just a space?
    JZ    Save_Iret        ;yep, save screen ptrs, Iret
    or    al,al            ;just a zero?
    JNZ    Lup1E4            ; yep, continue
Save_Iret:
    MOV    saveDI,DI            ;save screen pointers
    MOV    saveSI,SI
    MOV    bflag_13F,0FFH            ;reset flag
    JMP    SHORT    Pop_Iret        ;return

MoveChar:
    MOV    bflag_13F,0            ;turn flag off
    MOV    AL,ES:[SI]            ;snarf screen char
    MOV    ES:[DI],AL            ;move it here
    MOV    BYTE PTR ES:[SI],20H        ;blank out old char
    MOV    SI,DI
    ADD    DI,0A0H
    CMP    DI,0FA0H            ;screen bottom?
    JNB    L025B                ; not yet
    MOV    AL,ES:[DI]            ;get char
    CMP    AL,20H                ;just a space?
    JZ    Save_Iret            ; yep, save ptrs, Iret
    or    al,al                ; a 0?
    JZ    Save_Iret            ; yep, save ptrs, Iret
    JMP    SHORT    L025F

L025B:    MOV    BYTE PTR ES:[SI],20H        ;stuff space on screen
L025F:    DEC    wcntr_13A            ;decrement counter
    JNZ    L026F
     SHR    byte_13C,1
     MOV    wcntr_13A,40H            ;refresh counter
L026F:    CALL    L02AC
    AND    AL,byte_13C
    MOV    bcntr_13E,AL
Pop_Iret:
    POP    SI
    POP    DI
    POP    CX
    POP    DX
    POP    DS
    POP    ES
    POP    AX
    POPF
    MOV    CS:bflag_13D,0            ;clear flag
    IRET
NewInt8    endp

L02AC    proc    near
    MOV    AX,word_2BE
    PUSH    AX
    AND    AH,0B4H
    POP    AX
    JPE    L02B7
     STC
L02B7:    RCL    AX,1
    MOV    word_2BE,AX
    RET
L02AC    endp


Start    proc    near
    MOV    ax,3508H        ;get Int8 vector
    INT    21H
    mov    word ptr int8Vec,bx    ;save ofs
    mov    word ptr int8Vec+2,ES    ;save seg

    MOV    AH,2CH            ;get DOS system time
    INT    21H
    MOV    word_2BE,DX        ;save seconds, deciseconds
    MOV    bcntr_13E,0FFH        ;refresh counter
    MOV    AH,0FH            ;get current video mode
    INT    10H
    CMP    AL,6            ;?
    JZ    Use_Mono        ; yep
    CMP    AL,7            ;mono?
    JZ    Use_Mono        ;yep
     MOV    video,0B800H        ;use color screen

Use_Mono:
    MOV    DX,OFFSET NewInt8    ;DS:dx = our service
    mov    ax,2508H        ;set new Int 8 vector
    INT    21H

    MOV    DX,offset Start        ;program end
    MOV    CL,4
    SHR    DX,CL            ;compute size in paras
    INC    DX            ;safeside
    MOV    AH,31H            ;advanced TSR
    INT    21H

    DB    'DRIP Version 2.01',0    ;,CR,LF
    DB    'G. Masters 5/25/87',0    ;,CR,LF
    db    'Toad Hall 880421',0
;    DB    1AH
;    DB    90H
Start    endp


Cseg    ENDS
    END    Drip