common.asm

这是一些例程

        .MODEL  small, pascal
        INCLUDE demo.inc

        .DATA
vconfig VIDCONFIG <>           ; Global video configuration structure

        .CODE

;* GetVidConfig - Determines current video configuration and initializes
;* the vconfig structure.
;*
;* Shows:   BIOS Interrupt - 10h, Function 0 (Set Video Mode)
;*                           10h, Function 0Fh (Get Current Video Mode)
;*                           10h, Function 1Ah (Video Display Combination)
;*
;* Uses:    vconfig - Video configuration structure, declared in the
;*          DEMO.INC include file.
;*
;* Params:  None
;*
;* Return:  None

GetVidConfig PROC

        mov     ax, 1A00h               ; Get video info for VGA
        int     10h
chkVGA:
        cmp     al, 1Ah                 ; Is VGA or MCGA present?
        jne     chkEGA                  ; No?  Then check for EGA

        cmp     bl, 2                   ; If VGA exists as secondary adapter,
        je      isCGA                   ;   check for CGA and mono as primary
        jb      isMONO
        cmp     bl, 5                   ; If EGA is primary, do normal
        jbe     chkEGA                  ;   EGA checking
chkMCGA:
        mov     vconfig.adapter, MCGA   ; Yes?  Assume MCGA
        mov     vconfig.display, COLOR
        cmp     bl, 8                   ; Correct assumption?
        ja      gotmode                 ; Yes?  Continue
isVGA:
        mov     vconfig.adapter, VGA    ; Assume it's VGA color
        je      gotmode                 ; Yes?  Continue
        mov     vconfig.display, MONO   ; No?  Must be VGA mono
        jmp     gotmode                 ; Finished with VGA, so jump
chkEGA:
        mov     ah, 12h                 ; Call EGA status function
        mov     bl, 10h
        sub     cx, cx                  ; Clear status bits
        int     10h
        jcxz    chkCGA                  ; If CX is unchanged, not EGA
isEGA:
        mov     vconfig.adapter, EGA    ; Set structure fields for EGA
        mov     vconfig.display, MONO   ; Assume EGA mono
        or      bh, bh                  ; Correct assumption?
        jnz     gotmode                 ; Yes?  Continue
        mov     vconfig.display, COLOR  ; No?  Must be EGA color
        jmp     gotmode                 ; Finished with EGA, so jump
chkCGA:
        int     11h                     ; Get equipment list
        and     al, 30h                 ; If bits 4-5 set, monochrome
        cmp     al, 30h                 ; Monochrome text mode?
        je      isMONO                  ; Yes?  Continue
isCGA:
        mov     vconfig.adapter, CGA    ; No?  Must be CGA
        mov     vconfig.display, COLOR
        jmp     gotmode
isMONO:
        mov     vconfig.adapter, MDA    ; Set MONO
        mov     vconfig.display, MONO
gotmode:
        mov     ah, 0Fh
        int     10h                     ; Get current mode
        mov     vconfig.mode, al        ; Record mode
        mov     vconfig.dpage, bh       ;   and current page
        mov     al, vconfig.display     ; Multiply display value
        cbw                             ;   (which is either 0 or 1)
        mov     bx, 800h                ;   by 800h, then add to 0B000h
        mul     bx                      ;   for segment address of
        add     ax, 0B000h              ;   video buffer
        add     ah, vconfig.dpage       ; Adding display page gives
        mov     vconfig.sgmnt, ax       ;   address of current page

        sub     ax, ax
        mov     es, ax
        mov     al, es:[44Ah]           ; Get number of display cols
        mov     vconfig.cols, al        ; Store in structure
        mov     vconfig.rows, 24        ; Assume bottom row # = 24
        cmp     vconfig.adapter, EGA    ; EGA or VGA?
        jl      exit                    ; No?  Exit
        mov     ax, 1130h               ; Yes?  Request character info
        sub     bh, bh                  ; Set BH to valid value
        push    bp                      ; BP will change, so save it
        int     10h                     ; Get number of rows/screen
        mov     vconfig.rows, dl        ; Keep in structure
        pop     bp                      ; Restore BP
exit:
        ret

GetVidConfig ENDP


;* GetCurPos - Gets current cursor position.
;*
;* Uses:    vconfig - Video configuration structure (initialized
;*          by calling the GetVidConfig procedure)
;*
;* Params:  None
;*
;* Return:  Short integer with high byte = row, low byte = column

GetCurPos PROC USES bx dx

        mov     ah, 3                   ; Function 3
        mov     bh, vconfig.dpage
        int     10h                     ; Get cursor position
        mov     ax, dx
        ret

GetCurPos ENDP


;* SetCurPos - Sets cursor position.
;*
;* Shows:   BIOS Interrupt - 10h, Function 2 (Set Cursor Position)
;*
;* Uses:    vconfig - Video configuration structure (initialized
;*          by calling the GetVidConfig procedure)
;*
;* Params:  Row - Target row
;*          Col - Target column
;*
;* Return:  None

SetCurPos PROC USES bx dx,
        Row:WORD,
        Col:WORD

        mov     dh, BYTE PTR Row        ; DH = row
        mov     dl, BYTE ptr Col        ; DL = column
        mov     ah, 2                   ; Function 2
        mov     bh, vconfig.dpage       ; Current page
        int     10h                     ; Set cursor position
        ret

SetCurPos ENDP


;* StrWrite - Writes ASCIIZ string to video memory at specified row/column.
;*
;* Shows:   Instructions - lodsb     stosb
;*
;* Uses:    vconfig - Video configuration structure (initialized
;*          by calling the GetVidConfig procedure)
;*
;* Params:  Row - Row coordinate
;*          Col - Column coordinate
;*          Sptr - Pointer to string
;*
;* Return:  None

StrWrite PROC USES ds si di,
        Row:WORD,
        Col:WORD,
        Sptr:PTR BYTE

        GetVidOffset Row, Col           ; Get video offset for these coords
        mov     di, ax                  ; Copy to DI
        LoadPtr ds, si, Sptr            ; DS:SI points to string
        mov     es, vconfig.sgmnt       ; ES:DI points to video RAM
        .WHILE  1                       ; Loop forever (or until break)
        lodsb                           ; Get 1 character from string
        .BREAK .IF al == 0              ; Quit if null terminator

; For CGA systems, StrWrite waits for the video to begin a horizontal
; retrace before writing a character to memory. This avoids the problem
; of video snow inherent with some (though not all) color/graphics adapters.
; It also demonstrates a somewhat different approach to the problem than the
; one taken in the WinOpen and WinClose procedures.

        .IF vconfig.adapter != CGA      ; If not CGA, skip this step
        push    ax                      ; Save character
        mov     dx, 3DAh                ; Address of status register
        cli                             ; Disallow interruptions
        .REPEAT
        in      al, dx                  ; Read current video status
        .UNTIL  !(al & 1)               ; Until horizontal retrace done

        .REPEAT
        in      al, dx                  ; No?  Read status again
        .UNTIL  al & 1                  ; Until retrace starts
        pop     ax                      ; Recover character
        .ENDIF  ; CGA only

        stosb                           ; Write char to video buffer
        sti                             ; Reenable interrupts in case CGA
        inc     di                      ; Skip attribute byte
        .ENDW
        ret

StrWrite ENDP


;* StrInput - Gets input string from keyboard using BIOS. Signals idle
;* state by calling interrupt 28h while polling for keypress, making
;* the procedure useful in TSR programs. Terminates when ENTER or ESC
;* keys pressed.
;*
;* Shows:   DOS interrupt - Interrupt 28h (DOS Idle Interrupt)
;*
;* Params:  Row - Row coordinate
;*          Col - Column coordinate
;*          Max - Maximum allowable string length
;*          Sptr - Pointer to string
;*