C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_300/344_01/litebar.asm

Assembly Source File | 1989-10-27 | 6.0 KB | 253 lines

        TITLE   LITEBAR
        PAGE    60,132

        ;LITEBAR.ASM

    COMMENT     @

    This sub-routine inserts the attribute bytes in video ram that
    control colors in text modes. It first checks for Mono text mode,
    then whether a VGA or EGA is currently active. If neither is the
    case it defaults to CGA.  Works only in Text Modes.



    ;extern void far pascal LITEBAR(
        int atr, int row, int col, int page, int len, int dir
        );

    @       Modified    **  10/29/89  **     Michael Kelly


    ;Since we don't mess with a Data Segment this module can
    ;be linked to any memory model except tiny.
    ;I debugged this in Turbo Pascal 4.0, can be used there too.

    VMODE           EQU     BYTE PTR ES:[0049h]
    VCOLS           EQU     WORD PTR ES:[004Ah]
    VPAGE_SIZE      EQU     WORD PTR ES:[004Ch]
    VROWS           EQU     BYTE PTR ES:[0084h]
    INFO_BYTE       EQU     BYTE PTR ES:[0087h]

    BYTES_PER_ROW   EQU     WORD PTR [BP-2]     ;local variables
    IS_CGA_ADAPT    EQU     WORD PTR [BP-4]

    ATR_PARAM       EQU     [BP+16]    ;proc arguments
    ROW_PARAM       EQU     [BP+14]
    COL_PARAM       EQU     [BP+12]
    PAGE_PARAM      EQU     [BP+10]
    LEN_PARAM       EQU     [BP+8]
    DIR_PARAM       EQU     [BP+6]

    CSEG    SEGMENT BYTE    PUBLIC  'CODE'
        ASSUME  CS:CSEG
        PUBLIC  LITEBAR
LITEBAR         PROC    FAR
    START:  PUSH    BP
        MOV     BP,SP
        SUB     SP,4
        PUSH    DS
        PUSH    SI
        PUSH    ES
        PUSH    DI
        PUSHF
        CLD
        XOR     CX,CX               ;check the video hardware
        MOV     IS_CGA_ADAPT,0
        MOV     DX,0B000h           ;assume mono video segment
        XOR     DI,DI               ;and memory ofset of 0 for now.
        MOV     AX,40h
        MOV     ES,AX
        MOV     AL,VMODE            ;check video mode
        CMP     AL,7
        JE      LITE_02
        MOV     DX,0B800h
        CMP     AL,3
        JBE     LITE_01
        JMP     EXIT                    ;exit if not in text mode.

    LITE_01:
        MOV     AX,1A00h                ;Test for Vga Bios support.
        INT     10h
        CMP     AL,1Ah
        JNE     LITE_011
        CMP     BL,2
        JNE     LITE_02
        MOV     IS_CGA_ADAPT,1
        JMP     SHORT LITE_02
    LITE_011:
        MOV     AH,12h                      ;Ega Bios support?
        MOV     BL,10h
        INT     10h
        CMP     BL,10h
        JNE     LITE_012
        MOV     IS_CGA_ADAPT,1              ;Default to Cga.
        JMP     SHORT LITE_02
    LITE_012:
        MOV     AX,40h
        MOV     ES,AX
        TEST    INFO_BYTE,8
        JZ      LITE_02                 ;If bit 3 = 0, Ega is active
        MOV     IS_CGA_ADAPT,1          ;else using Cga.


    LITE_02:    MOV     AX,40h
        MOV     ES,AX
        MOV     AX,VCOLS
        SHL     AX,1
        MOV     BYTES_PER_ROW,AX

        MOV     BX,PAGE_PARAM       ;Calc offset of video page
        CMP     BX,0                ;using shifts and adds.
        JE      LITE_03
        MOV     AX,VPAGE_SIZE
        OR      BX,BX
        JZ      LITE_03
        CMP     BX,7
        JBE     LITE_021
        JMP     EXIT                ;Assume Max page # is 7
    LITE_021:   CMP     BX,1
        JA      LITE_022
        MOV     DI,AX
        JMP     SHORT LITE_03
    LITE_022:   CMP     BX,2
        JA      LITE_023
        SHL     AX,1
        MOV     DI,AX
        JMP     SHORT LITE_03
    LITE_023:   CMP     BX,3
        JA      LITE_024
        MOV     DI,AX
        SHL     AX,1
        ADD     DI,AX
        JMP     SHORT LITE_03
    LITE_024:   CMP     BX,4
        JA      LITE_025
        SHL     AX,1
        SHL     AX,1
        MOV     DI,AX
        JMP     SHORT LITE_03
    LITE_025:   CMP     BX,5
        JA      LITE_026
        MOV     DI,AX
        SHL     AX,1
        SHL     AX,1
        ADD     DI,AX
        JMP     SHORT LITE_03
    LITE_026:   CMP     BX,6
        JA      LITE_027
        SHL     AX,1
        MOV     DI,AX
        SHL     AX,1
        ADD     DI,AX
        JMP     SHORT LITE_03
    LITE_027:   PUSH    AX
        SHL     AX,1
        MOV     DI,AX
        SHL     AX,1
        ADD     DI,AX
        POP     AX
        ADD     DI,AX

    LITE_03:
        MOV     AX,ROW_PARAM        ;get video row param
        DEC     AX                  ;rows numberred from 1 so
        JZ      LITE_04             ;subtract one for mem offset.
        MOV     BX,BYTES_PER_ROW
        MUL     BL

    LITE_04:
        MOV     BX,COL_PARAM        ;do same with video column.
        XOR     BH,BH
        DEC     BX
        SHL     BX,1                ;mult by 2 for char/attr pair.


        ADD     AX,BX
        ADD     DI,AX
        MOV     ES,DX
        MOV     AX,ATR_PARAM        ;get color or attr.
        MOV     CX,LEN_PARAM        ;num of chars to color.
        OR      CX,CX
        JNZ     LITE_05
        JMP     EXIT

    LITE_05:
        CMP     IS_CGA_ADAPT,0  ;jump to hardware hassle if Cga
        JNE     LITE_09         ;otherwise just stuff video memory.

        OR      BYTE PTR DIR_PARAM,0
        JNZ     LITE_07

    LITE_06:    INC     DI                  ;stuff memory horizontally
        STOSB
        LOOP    LITE_06
        JMP     EXIT

                    ;or vertically depending on dir param.
    LITE_07:    INC     DI
    LITE_08:    MOV     BYTE PTR ES:[DI],AL
        ADD     DI,BYTES_PER_ROW
        LOOP    LITE_08
        JMP     EXIT

    LITE_09:    MOV     DX,03DAh             ;Crt status reg for sync timing
        OR      BYTE PTR DIR_PARAM,0    ;to avoid "snow" on screen.
        JNZ     LITE_13

    LITE_10:    INC     DI
        MOV     BX,AX
        CLI                 ;turn off interrupts and wait
    LITE_11:    IN      AL,DX       ;for horiz sync start to avoid snow.
        AND     AL,1
        JNZ     LITE_11

    LITE_12:    IN      AL,DX
        AND     AL,1        ;if bit 0 = 1 sync has begun
        JZ      LITE_12

        XCHG    AX,BX       ;so stuff one word in memory.
        STOSB
        STI
        LOOP    LITE_10     ;repeat until len param satisfied.
        JMP     EXIT

    LITE_13:    ADD     DI,2        ;same as above but in vertacal dir
    LITE_14:    DEC     DI
        DEC     DI
    LITE_15:    MOV     BX,AX
        CLI
    LITE_16:    IN      AL,DX
        AND     AL,1
        JNZ     LITE_16

    LITE_17:    IN      AL,DX
        AND     AL,1
        JZ      LITE_17
        XCHG    AX,BX
        STOSB
        STI
        ADD     DI,BYTES_PER_ROW
        LOOP    LITE_14


    EXIT:
        POPF              ;restore flags & regs
        POP     DI
        POP     ES
        POP     SI
        POP     DS
        MOV     SP,BP
        POP     BP
        RET     12              ;discard params & return
LITEBAR         ENDP

    CSEG    ENDS

        END     START