The World of Computer Software/World_Of_Computer_Software-02-387-Vol-3of3.iso/n/nnansi93.zip/NNANSI.ASM

Assembly Source File | 1993-01-15 | 92KB | 3,711 lines

%title    "NNANSI Terminal Driver Version 1/93"
%pagesize    60, 132
%noconds
JUMPS    ; clarify branches -- TASM V2.0 recommended
; With MASM, delete the preceeding four lines.
;--- nnansi.asm ----------------------------------------------------------
; New, New ANSI terminal driver.
; Optimized for speed in the case of multi-character write requests.
; Original NANSI terminal driver (C) 1986 Daniel Kegel
; Modifications by Tom Almy without restrictions.

; May be distributed for educational and personal use only

; See file NNANSI.DOC for licensing information.

; Daniel Kegel, Bellevue, Washington & Pasadena, California
; Revision history:
; 5  july 85: brought up non-ANSI portion except forgot backspace
; 6  july 85: split off ANSI stuff into other files, added backspace
; 11 july 85: fixed horrible bug in getchar; changed dosfns to subroutines
; 12 july 85: fixed some scrolling bugs, began adding compaq flag
; 9  aug 85:  added cursor position reporting
; 10 aug 85:  added output character translation
; 11 aug 85:  added keyboard redefinition, some EGA 80x43 support
; 19 Aug 85:  Fixed horrible bug in insert/delete line.
; 26 Aug 85:  Fixed simple limit-to-one-too-few-lines bug in ins/del line;
;  anyway, it inserts 24 lines when on line 2 now.  Whether it's fixed...
; 4 Sept 85:  Fixed bug created on 26 Aug 85; when limiting ins/del line
;  count, we are clearing, not scrolling; fixed BIOS call to reflect this.
; 10 sept 85: Tandy 2000 support via compaq flag (finding refresh buffer)
; 30 Jan 86:  removed Tandy 2000 stuff, added graphics mode support
; 12 feb 86:  added int 29h handler, added PUSHA/POPA, added direct beep,
;          direct cursor positioning, takeover of BIOS write_tty,
;          noticed & squashed 2 related bugs in tab expansion
; 30 Jan 86:  Added EGA cursor patch
; 31 Jan 86:  Disabled insert/delete char in graphics modes
;          Implemented keyboard redefinition reset
;  1 Feb 86:  added video_mode and max_x test after mode set
; 13 feb 86:  Squashed them again, harder
; 24 feb 86:  There is a bug in the timing code used by the BEEP routine.
;          If the addition of the beep period to the
;          BIOS low timer word results in an overflow, the beep will be
;          supressed. Also made code compatible eith earlier versions
;          of assembler.

; Tom Almy, Tualatin, Oregon ([e-mail]) modified the NANSI
;  version ; 2.2 code for use in EGA/VGA environments only:
; 8 Jan 89:   Additional compilation options
;             Scrolling via reprogramming display start (*MUCH* faster)
;          INT29 updates display directly if not control character.
;          Various cleanups
; Nov 89:     Some bug fixes, customization for various cards enhanced
;             display modes, better handling of graphic cursor, graphic
;             characters in 16 color modes are drawn by NNANSI rather
;             than BIOS (much faster).
; Sept 90:    Color backgrounds and XOR mode (as BLINK) in 16 color graphic
;          modes. VGA has 43 or 50 line modes (instead of producing 50
;          (when 43 selected). FAST mode can be toggled via escape
;          sequences. Lots of code clean up. Some old options incorporated
;          (extra ANSI sequences) or deleted (output conversion).
;             The fast graphic draw routine has been speeded up, since it
;          was slower than some BIOSes (!). The BIOS TTY call has been
;             redirected to the INT29 routine which has some efficiency
;          speedups; this also saved code space.
; May 1991:   Restored CGA and MDA support. MDA is optional. Added
;          DOS 4.x compatibility. Added 40x43 and 40x50 text mode support.
;          Added VESA support. Fixed bug allowing either = or ? or nothing
;          in all set mode commands. Added enable/disable for bios
;          write_tty takeover. Added drivers for new cards and changed
;          some defaults. Merged source code into one file.
;           Card id printout idea by Arend van den Brug.
; Sept 1991:  Now installable as TSR (which can be removed) or device driver
;          with the same binary! Installation code now uses proper
;          system calls to set interrupt vectors
;             Added Desqview compatability
;             Removed changing modes without clearing screen -- it seems
;           to cause later crashing with some programs, particularly
;           Zortech ZWB and Doorway.
;    ****Credit and thanks to Ralf Brown and is interrupt list, without
;           which most of the recent changes would have been impossible****
; Sept 1992:  Minor bug fixes. Changes as noted below

; Nov  1992   Support DOS/V by Akira Kikuchi ([e-mail])

; Jan  1993   Added extended keyboard support, reworked ANSI state machine
;             Changed config.inc to use "=" rather than "EQU"

page
TRUE    equ    1
FALSE    equ    0

    INCLUDE CONFIG.INC
page
; Option dependent definitions
if VGA
if EGA
card_id macro
    db    'Generic EGA/VGA'
endm
else
card_id macro
    db    'Generic VGA'
endm
endif
else
if EGA
card_id macro
    db    'Generic EGA'
endm
else
card_id macro
    db    'Generic NANSI Clone'
endm
endif
endif

IF key_redef
buf_size    equ    init_buf_size    ; size of parameter/redef buffer
ELSE
buf_size    equ    20        ; size of parameter/redef buffer
ENDIF


IF    cheap_pc
    .8086
ELSE
    .286c
ENDIF

page
    INCLUDE DRIVERS.INC
page
; Some Useful Macros

IF    cheap_pc
push_all    macro
    push    ax
    push    bx
    push    cx
    push    dx
    push    bp
    push    si
    push    di
    endm
ELSE
push_all    macro
    pusha
    endm
ENDIF

IF    cheap_pc
pop_all macro
    pop    di
    pop    si
    pop    bp
    pop    dx
    pop    cx
    pop    bx
    pop    ax
    endm
ELSE
pop_all macro
    popa
    endm
ENDIF

call_video macro
            ; call original video interrupt by
            ; faking a SWI
    pushf        ; push flags
    call    dword ptr old_vid_bios
endm

draw_gcursor macro        ; draw graphic cursor
if quick_char
    mov    ax, 8f16h
    call    quick_graph
else
    mov    ax, 0916h        ; draw cursor at location
    mov    bx, 8fh
    mov    cx, 1
    call_video
endif
endm
    page

keybuf    struc                ; Used in getchar
len    dw    ?
adr    dw    ?
keybuf    ends


ABS40    segment at 40h
    org    1ah
buffer_head    dw    ?    ; Used in 'flush input buffer' dos call.
buffer_tail    dw    ?

    org    49h
crt_mode    db    ?
crt_cols    dw    ?
crt_len        dw    ?
crt_start    dw    ?
cursor_posn    dw    8 dup (?)
cursor_mode    dw    ?
active_page    db    ?
addr_6845    dw    ?
crt_mode_set    db    ?    ; = 7 only if monochrome display adaptor
crt_palette    db    ?
    org    6ch
timer_low    dw    ?    ; low word of time-of-day counter (18.2 hz)
    org    84h
ega_rows    db    ?    ; #rows-1 on display
ega_points    dw    ?    ; bytes per character

ABS40    ends

    page

CODE    segment word public 'CODE'
assume    cs:CODE, ds:CODE

    ; Device Driver Header

    org    0
start:
if TSR
nextdev    label    dword
    jmp    realstart
    db    0
else
nextdev dd    -1            ; next device
endif
if dos4
    dw    8053h            ; attributes
else
    dw    8013h            ; attributes
endif
    dw    strategy        ; request header pointer entry
    dw    interrupt        ; request entry point
    db    'CON'            ; device name (8 char)
    db    5 dup (20h)        ;  ... and 5 blanks)

    ; Identification- in case somebody TYPEs the assembled driver
    db    27,'[2J'
IDLOC:    db    "NNANSI.SYS 1/93 for "
    card_id
    ife    cheap_pc
    db    "(80286)"
    else
    db    "(80x86)"
    endif
    db    13, 10
    db    'by Tom Almy based on code (C) 1986 Daniel Kegel.'
if DOSV
    db    13, 10
    db    'Modified for DOS/V by Akira Kikuchi.'
endif
    db    13, 10, 26

    even
;----- variable area --------------------
    org    $-34        ; overlay id string with uninitialized data
if key_redef
    org    $-2
endif
if MONO
    org    $-2
endif
if TSR
    org    $-14
endif
req_ptr label    dword
req_off dw    ?
req_seg dw    ?
f_cptr_seg    dw    ?    ; part of fastout write buffer pointer
cur_parm_ptr    dw    ?    ; last byte of parm area now used
saved_coords    dw    ?    ; holds XY after a SCP escape sequence
temp_val    dw    ?    ; just a temporary
param_buffer    dw    ?    ; address of first byte free for new params
param_end    dw    ?    ; address of end of free area
if key_redef
redef_end    dw    ?    ; address of end of redefinition area
endif
if TSR
old_brk        dd    ?    ; original break handler
old_int29    dd    ?    ; original int29 handler
savecon        dd    ?    ; original console driver
parsize        dw    ?    ; size of TSR in segments
endif
if MONO
our_6845    dw    ?
endif
no_c_flag    db    ?    ; there is no graphic cursor on the screen.
max_y        db    ?    ; lines-1
max_cur_x    label    word    ; used to get both max & cur at once
max_x        db    ?    ; line width (79 for 80x25 modes)
cur_coords    label    word
cur_x        db    ?    ; cursor position (0 = left edge)
cur_y        db    ?    ;          (0 = top edge)
video_mode    db    ?    ; ROM BIOS video mode (2=BW, 3=color, etc)
string_term    db    ?    ; either escape or double quote
int_29_buf    db    ?    ; character buffer for int 29 calls
fnkeybuf    db    ?    ; holds second byte of fn key codes
eat_key        db    ?    ; Eaten key (bug fix)
cpr_buf        db    8 dup (?), '['
cpr_esc        db    1bh    ; descending buffer for cpr function

    even    ; this should be redundant, if I did it right

; following four keybufs hold information about input
; Storage order determines priority- since the characters making up a function
; key code must never be separated (say, by a Control-Break), they have the
; highest priority, and so on.    Keyboard keys (except ctrl-break) have the
; lowest priority.

fnkey    keybuf    <0, fnkeybuf>    ; fn key string (0 followed by scan code)
cprseq    keybuf    <0>        ; CPR string (ESC [ y;x R)
brkkey    keybuf    <0, brkkeybuf>    ; ^C
if key_redef
xlatseq keybuf    <0>        ; keyboard reassignment string
endif

escvector    dw    0    ; state vector of ESCape sequencor
if DESQVIEW
disppage    dw    0b800h    ; address of display page
if DOSV
dvactive    db    1    ; to put NNANSI on its good behavior
else
dvactive    db    0    ; is desqview active?
endif
endif
brkkeybuf    db    3    ; control C
wrap_flag    db    1    ; 0 = no wrap past line end
cur_attrib    db    7    ; current char attributes
gmode_flag    db    0    ; true if in graphics mode
                ; <0 for mono card
gcursor        db    initgc    ; true if graphic cursor enabled
fmode        db    initfast    ; in fast mode?
bmode        db    initbiosw    ; ANSI write_tty BIOS command?
atr_flag    db    0    ; 80h - blink, 8 - bright
                ; 4 - invisible 2 - reverse 1 underline
color_flag    db    7h    ; fg and bg colors

if TSR
fulldvr        db    1    ; Full driver installation
endif
port_6845    equ    3d4h
page
;------ xy_to_regs --------------------------------------------
; on entry: x in cur_x, y in cur_y
; on exit:  dx = chars left on line, di = address
; Alters ax, bx.
xy_to_regs    proc    near
    ; Find number of chars 'till end of line, keep in DX
    mov    ax, max_cur_x
    mov    bx, ax            ; save max_x & cur_x for next block
    xor    ah, ah            ; ax = max_x
    xchg    dx, ax
    mov    al, bh
    xor    ah, ah            ; ax = cur_x
    sub    dx, ax
    inc    dx            ; dx is # of chars till EOL
    ; Calculate DI = current address in text buffer
    mov    al, bl            ; al = max_x
    inc    al
    mul    cur_y
    add    al, bh            ; al += cur_x
    adc    ah, 0            ; AX is # of chars into buffer
    add    ax, ax
    xchg    di, ax            ; DI is now offset of cursor.

    push    ds
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40
    add    di, crt_start        ; crt offset
                    ; the offset could be non-zero because
                    ; of video pages or fast scrolling.
    pop    ds
    assume    ds:nothing
    ret
xy_to_regs    endp

page
;------- dos_fn_tab -------------
; This table is used in "interrupt" to call the routine that handles
; the requested function.

if dos4
max_cmd equ    24
dos_fn_tab:
    dw    dosfn0, nopcmd, nopcmd, badcmd, dosfn4, dosfn5, dosfn6
    dw    dosfn7, dosfn8, dosfn8, nopcmd, nopcmd
    dw    badcmd, badcmd, badcmd, nopcmd, badcmd ; 12-16
    dw    badcmd, badcmd    ; 17-18 unassigned
    dw    dosfn19
    dw    badcmd, badcmd, badcmd    ; 20-22 unassigned
    dw    nopcmd, nopcmd
else
max_cmd equ    12
dos_fn_tab:
    dw    dosfn0, nopcmd, nopcmd, badcmd, dosfn4, dosfn5, dosfn6
    dw    dosfn7, dosfn8, dosfn8, nopcmd, nopcmd
endif
;------- strategy ----------------------------------------------------
; DOS calls strategy with a request which is to be executed later.
; Strategy just saves the request.

strategy    proc    far
    mov    cs:req_off,BX
    mov    cs:req_seg,ES
    ret
strategy    endp

;------ interrupt -----------------------------------------------------
; This is where the request handed us during "strategy" is
; actually carried out.
; Calls one of 12 subroutines depending on the function requested.
; Each subroutine returns with exit status in AX.

interrupt    proc    far

    sti
    push_all            ; preserve caller's registers
    push    ds
    push    es


    ; Read requested function information into registers
    lds    bx,cs:req_ptr
    xor    ah,ah            ; clear upper part of ax
    mov    al,ds:[BX+02h]        ; al = function code
;
; The next instruction blows up MASM 1.0 but who cares!!
;
    les    si,[BX+0Eh]        ; ES:SI = input/output buffer addr
    mov    cx,[BX+12h]        ; cx = input/output byte count

    cmp    al, max_cmd
    ja    unk_command        ; too big, exit with error code

    xchg    bx, ax
    shl    bx, 1            ; form index to table of words
    mov    ax, cs
    mov    ds, ax
    call    word ptr dos_fn_tab[bx]
int_done:
    lds    bx,cs:req_ptr        ; report status
    or    ax, 100h        ; (always set done bit upon exit)
    mov    [bx+03],ax

    pop    ES            ; restore caller's registers
    pop    DS
    pop_all
    ret                ; return to DOS.

unk_command:
    call    badcmd
    jmp    int_done

interrupt    endp
    page
;----- BIOS break handler -----------------------------------------
; Called by BIOS when Control-Break is hit (vector was set up in Init).
; Simply notes that a break was hit.  Flag is checked during input calls.

break_handler    proc
    mov    cs:brkkey.len, 1
    iret
break_handler    endp

    page

;------ badcmd -------------------------------------------------------
; Invalid function request by DOS.
badcmd    proc    near
    mov    ax, 813h        ; return "Error: invalid cmd"
    ret
badcmd    endp


;------ nopcmd -------------------------------------------------------
; Unimplemented or dummy function request by DOS.
nopcmd    proc    near
    xor    ax, ax            ; No error, not busy.
    ret
nopcmd    endp
    page
;------- dos function #4 ----------------------------------------
; Reads CX characters from the keyboard, places them in buffer at
; ES:SI.
dosfn4    proc    near
    jcxz    dos4done
    mov    di, si
dos4lp: push    cx
    call    getchar
    pop    cx
    stosb
    loop    dos4lp
dos4done:
    xor    ax, ax            ; No error, not busy.
    ret
dosfn4    endp
    page
;-------- dos function #5: non-destructive input, no wait ------
; One-character lookahead into the keyboard buffer.
; If no characters in buffer, return BUSY; otherwise, get value of first
; character of buffer, stuff into request header, return DONE.
dosfn5    proc    near
    call    peekchar
    jz    dos5_busy

    lds    bx,req_ptr
    mov    [bx+0Dh], al
    xor    ax, ax            ; No error, not busy.
    jmp    short dos5_exit
dos5_busy:
    MOV    ax, 200h        ; No error, busy.
dos5_exit:
    ret

dosfn5    endp
    page
;-------- dos function #6: input status --------------------------
; Returns "busy" if no characters waiting to be read.
dosfn6    proc    near
    call    peekchar
    mov    ax, 200h        ; No error, busy.
    jz    dos6_exit
    xor    ax, ax            ; No error, not busy.
dos6_exit:
    ret
dosfn6    endp
    page
;-------- dos function #7: flush input buffer --------------------
; Clears the IBM keyboard input buffer.     Since it is a circular
; queue, we can do this without knowing the beginning and end
; of the buffer; all we need to do is set the tail of the queue
; equal to the head (as if we had read the entire queue contents).
; Also resets all the device driver's stuffahead buffers.
dosfn7    proc    near
    xor    ax, ax
    mov    fnkey.len, ax        ; Reset the stuffahead buffers.
    mov    cprseq.len, ax
    mov    brkkey.len, ax
if key_redef
    mov    xlatseq.len, ax
endif

    mov    ax, ABS40
    mov    es, ax
    mov    ax, es:buffer_head    ; clear queue by making the tail
    mov    es:buffer_tail, ax    ; equal to the head

    xor    ax, ax            ; no error, not busy.
    ret
dosfn7    endp
    page
IF dos4
;------- dos function #19: Generic IOCTL
; DOS4 way of setting display size using MODE command.
; We will do more than necessary.
;
dosfn19    proc    near
    les    bx, req_ptr    ; get request block
    mov    ax, es:[BX+13]    ; get function code
    cmp    ax, 5f03h    ; is it set information?
    jz    setinfo
    cmp    ax, 7f03h    ; is it get information?
    jz    getinfo
    mov    ax, 8003h    ; return bad command
    ret
getinfo:
    les    bx, es:[bx+19]    ; data packet to set
    push    ds
    mov    ax, ABS40    ; address ABS40 area
    mov    ds, ax
    assume ds:ABS40
    mov    word ptr es:[bx+0], 0    ; level and reserved fields
    mov    word ptr es:[bx+2], 14    ; length field
    mov    word ptr es:[bx+4], 0    ; flags
    mov    al, crt_mode
    call    set_gmode
    mov    ax, 1
    cmp    cs:gmode_flag, 0    ; see if graphics mode
    jz    fn19txt
    inc    ax
if MONO
    cmp    cs:gmode_flag, -7    ; check for mono mode
    jne    fn19txt
    dec    ax
    mov    word ptr es:[bx+8], 0    ; monochrome
    jmp    short fn19mono
endif
fn19txt:
    mov    word ptr es:[bx+8], 4    ; say 16 colors
fn19mono:
    mov    word ptr es:[bx+6], ax    ; store mode
    mov    ax, crt_cols
    mov    word ptr es:[bx+0eh], ax    ; character columns
    mov    dx, 8            ; all characters are 8 pixels wide
    mul    dx
    mov    word ptr es:[bx+0ah], ax    ; pixel columns
    xor    ax, ax
    mov    al, ega_rows
    inc    ax
    mov    word ptr es:[bx+10h], ax    ; character rows
    mov    dx, ega_points
    mul    dx
    mov    word ptr es:[bx+0ch], ax    ; pixel rows
    pop    ds
    assume ds:CODE
    xor    ax, ax
    ret
fn19fail:
    mov    ax, 8003h    ; unknown mode, failure
    ret
setinfo:
    les    bx, es:[bx+19]    ; data packet to read
;    mov    dx, 80h        ; monochrome, don't clear screen
    xor    dx, dx        ; monochrome
    cmp    word ptr es:[bx+8], 0    ; set to monochrome?
    je    setismono
    inc    dx
setismono:
    mov    ax, es:[bx+0eh]    ; character columns
    cmp    ax, 40        ; 40 columns?
    je    fn1940col
    cmp    ax, 80
    jne    fn19fail
    add    dx, 2        ; mode 2 or 3
fn1940col:
    mov    ax, es:[bx+10h]    ; character rows
    cmp    ax, 25
    je    fn1925lin
IF VGA
    cmp    ax, 50
    je    fn1950lin
ENDIF
    cmp    ax, 43
    jne    fn19fail

IF VGA
    mov    ax, 1201h    ; 350 lines
    jmp    short ln50join
fn1950lin:
    mov    ax, 1202h    ; 400 lines
ln50join:
    push    dx
    mov    bl, 30h        ; set scan lines
    int     10h
    pop    ax        ; the mode
ELSE
    mov    ax, dx
ENDIF
    int    10h        ; set video mode

    mov    ax, 1112h    ; set 8x8 font
    mov    bl, 0
    int     10h

    mov    ax, 1200h    ; load new printscreen
    mov    bl, 20h
    int     10h
IF EGA    ; set the EGA cursor
    mov    dx, port_6845    ; '6845' command reg
    mov    ax, 070ah    ; start on line 7
    out    dx, ax
    mov    al, 0bh        ; end on line 7
    out    dx, ax
ENDIF
    jmp     short clrs

fn1925lin:
IF VGA
    push    dx
    mov    ax, 1202h    ; select 400 scan lines
    mov    bl,30h        ; this call ignored on EGA
    int    10h
    pop    ax
ELSE
    mov    ax, dx
ENDIF
    int    10h        ; set video mode

clrs:    push    ds        ; address abs40 area
    mov    ax, ABS40
    mov    ds, ax
    ASSUME    ds:ABS40
    mov    ax, 600h        ; clear display area
    xor    cx, cx            ; upper left corner
    mov    dx, crt_cols
    dec    dl            ; right column
    mov    dh, ega_rows        ; lower row
    mov    bh, cs:cur_attrib    ; character attribute
    int    10h
    pop    ds
    ASSUME    ds:CODE
    xor    ax, ax            ; return success
    ret

dosfn19    endp
ENDIF
    page
if dos4
;--- new_mpx ------------------------------------------------
; This routine acknoledges that an ansi driver is installed.
;

new_mpx    proc
    cmp    ax, 1a00h    ; is this for us?
    jz    ackansi        ;
    db    0eah        ; if not, jump (far) to old_mpx
old_mpx dd    0
ackansi:
    mov    al, 0ffh    ; say we are installed
    iret
new_mpx endp
endif
    page
;--- new_vid_bios -------------------------------------------
; new_vid_bios takes the set cursor, get display mode, change mode, and
; get mode calls.

; If bios_write_tty defined, new_vid_bios replaces the write_tty call.
; This gives BIOS ANSI capability.
; However, it takes away the escape character.
; If this is not desired, just tell init to not take over the vector.
;
; All other calls get sent to the old video bios.

new_vid_bios    proc
    STI
IF bios_write_tty
    cmp    ah, 0Eh
    je    nvb_write_tty
ENDIF
    cmp    Ah, 02h     ; set cursor position command?
    je    nvb_setcursor
    cmp    Ah,0        ; change mode command?
    je    nvb_smode
    cmp    cs:fmode,0    ; slow mode?
    je    new_vid_pass    ; then pass it on
    cmp    Ah, 0Fh     ; get display mode command?
    je    nvb_display
    cmp    Ah, 06h        ; clear screen command?
    je    nvb_scroll
    cmp    Ah, 07h        ; alternative cls command?
    je    nvb_scroll
IF VESA
    cmp    AX, 4f02h    ; set extended display mode?
    je    nvb_smode
    cmp    AX, 4f03h    ; get extended display mode?
    je    nvb_display
ENDIF
    jmp    new_vid_pass    ; everything else

IF bios_write_tty
; WRITE TTY SUBCOMMAND
nvb_write_tty:
    cmp    cs:bmode, 0    ; don't write with our driver?
    jz    new_vid_pass
    push    cx        ; save register
    mov    cl, cs:cur_attrib
    ; If in graphics mode, BL is new color
    cmp    cs:gmode_flag, 0
    jle    nvb_wt_text
    mov    cs:cur_attrib, bl    ; ja?
nvb_wt_text:
    int    29h
    mov    cs:cur_attrib, cl
    pop    cx
    iret
ENDIF

; GET DISPLAY MODE SUBCOMMAND
nvb_display:
    cmp    cs:gmode_flag,0    ; Graphic mode? Mono?
    jnz    new_vid_pass
    push    ds
    push    ax
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40
    cmp    crt_start,0    ; At start of mem?
    jz    nvb_pass
if BAD_ERASE
nvb_clean:
    call    move_back
else
    call    move_back
nvb_clean:
endif
nvb_pass:
    pop    ax        ; restore registers
    pop    ds
    assume    ds:nothing
new_vid_pass:
    db    0eah        ; jump (far) to old video bios routine
old_vid_bios    dd    ?    ; pointer to old video bios routine

; SCROLL DISPLAY SUBCOMMAND
nvb_scroll:
    push    ds
    push    ax
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40
    mov    cs:no_c_flag, 1    ; if graphic, don't draw cursor afterwards
    cmp    cs:gmode_flag,0    ; graphic mode?
    jnz    nvb_pass
    cmp    crt_start,0    ; not at start of mem
    jz    nvb_pass
    pop    ax        ; restore ax
    push    ax
    cmp    al, 0        ; scroll, not erase
    jnz    nvb_clean
    or    cx, cx        ; not entire screen?
    jnz    nvb_clean
    push    dx        ; (logic fixed 9/92)
    inc    dl
    cmp    dl, byte ptr crt_cols    ; same question, max columns
    pop    dx
    jb    nvb_clean        ; >size is full screen, though
    cmp    dh, ega_rows        ; same question, max rows
    jb    nvb_clean        ; >size is full screen, though
    xor    ax,ax        ; erase is easier since we don't move screen
    mov    crt_start,0    ; reset offsets
    push    dx
    mov    dx,port_6845
    mov    al,0ch
    out    dx,ax
    inc    al
    out    dx,ax
    pop    dx
    jmp    nvb_pass

; SET CURSOR SUBCOMMAND
nvb_setcursor:
    cmp    cs:gmode_flag,0    ; Alpha mode?, Mono mode?
    jle    new_vid_pass
    cmp    cs:no_c_flag, 0    ; inhibited cursor?
    jnz    new_vid_pass    ; then keep inhibited
    cmp    cs:gcursor, 0    ; no cursor?
    jz    new_vid_pass    ; then don't want one now!
    push_all
    draw_gcursor
    pop_all
    call_video            ; original int 10h
    push_all
    draw_gcursor            ; redraw the cursor
    pop_all
    iret                ; return from interrupt

; SET DISPLAY MODE SUBCOMMAND
nvb_smode:
    call_video
    push    ds
    push    ax
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40
    mov    al, crt_mode    ; get mode and check for being graphic
    call    set_gmode
    mov    cs:no_c_flag, al ; if graphic, then no cursor is on screen.
    pop    ax
    pop    ds
    assume    ds:nothing
    iret
new_vid_bios    endp

    page
;------ int_29 ----------------------------------------------
; Int 29 handles DOS quick-access putchar.
; Last device loaded with attribute bit 4 set gets accessed for
; single-character writes via int 29h instead of via interrupt.
; Must preserve all registers.
; Installed as int 29h by dosfn0 (init).

int_29    proc    near
    sti
    push    ds
    push    es
    push_all
if fast29
    cmp    al, 20h            ; control char?
    jb    slow_way
    cmp    cs:escvector, 0        ; middle of an escape sequence?
    jnz    slow_way
    mov    dx, ABS40
    mov    ds, dx            ; set addressability
    assume    ds:ABS40
    mov    cx, word ptr crt_mode    ; mode in cl, columns in ch
    push    ax
    mov    al, cl
    call    set_gmode        ; check for graphics mode
    pop    ax
    cmp    cs:gmode_flag, 0    ; slow if graphics
    jg    slow_way
;    cmp    cl, 3            ; graphics mode?
;    ja    slow_way
    xor    bx, bx            ; get cursor position
    mov    bl, active_page
    add    bx, bx
    mov    dx, cursor_posn[bx]        ; dh has y, dl has x
    inc    dl            ; point to next location
    cmp    dl, ch            ; at edge?
    jnb    slow_way
                    ; we can go with it!
    mov    cursor_posn[bx], dx    ; update pointer
    xchg    ax, bx
    mov    al, dh
    mul    ch            ; ax has line offset
    add    al, dl
    adc    ah, 0            ; total offset
    mov    cx, bx
    mov    bx, ax            ; cl has character, bx offset

if DESQVIEW
    cmp    dvactive, 0        ; Desqview running?
    jz    dv_not_on            ; if not, update cursor directly
    push    bx            ; if  so, update via BIOS call
    xor    bx, bx
    mov    ah, 2
    call_video
    pop    bx
    jmp    dv_was_on
dv_not_on:
endif

    mov    ax, crt_start
    shr    ax, 1
    add    bx, ax            ; corrected cursor offset, either
                    ; because of fast scroll or
                    ; page<>0

if MONO
    mov    dx, addr_6845        ; update cursor location
else
    mov    dx, port_6845        ; update cursor location
endif
    mov    al,0eh        ; more effective to write two bytes at a time
    mov    ah,bh
    out    dx,ax
    inc    al
    mov    ah,bl
    out    dx,ax

dv_was_on:
    mov    al, cl            ; get back character

    dec    bx
    add    bx, bx            ; byte offset
if DESQVIEW
    mov    dx, disppage
else
    mov    dx, 0b800h        ; address screen
endif
if MONO
    cmp    crt_mode, 7
    jne    int29_not_mono
    mov    dh, 0b0h
int29_not_mono:
endif
    mov    ds, dx
    assume    ds:nothing
    mov    ah, cs:cur_attrib
    mov    ds:[bx], ax        ; write character
    jmp    short int_fin
endif
slow_way:
    mov    cx, 1
    mov    bx, cs
    mov    es, bx
    mov    si, offset int_29_buf
    mov    byte ptr es:[si], al
    call    dosfn8
int_fin:
    pop_all
    pop    es
    pop    ds
    iret
int_29    endp

    page
;------ dosfn8 -------------------------------------------------------
; Handles writes to the device (with or without verify).
; Called with
;  CX     = number of bytes to write
;  ES:SI = transfer buffer
;  DS     = CS, so we can access local variables.  NOT ANY MORE

dosfn8    proc    near

    mov    cs:f_cptr_seg, es    ; save segment of char ptr

    ; Read the BIOS buffer address/cursor position variables.
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40

    ; Find current video mode and screen size.
    mov    ax,word ptr crt_mode    ; al = crt mode; ah = # of columns
    mov    cs:video_mode, al
    dec    ah            ; ah = max column
    mov    cs:max_x, ah

    ; Save graphics mode flag
    call    set_gmode

    mov    al, ega_rows        ; number of display rows
    mov    cs:max_y, al        ; set maxy value

    ; Find current cursor coordinates.

    mov    al, active_page
    cbw
    add    ax, ax
    xchg    bx, ax
    mov    ax, cursor_posn[bx]
    mov    cs:cur_coords, ax

if MONO
    mov    ax, addr_6845        ; get the right 6845
    mov    cs:our_6845, ax
endif

    ; Find video buffer segment address; adjust it
    ; so the offset is zero; return in AX.

if DESQVIEW
    mov    ax, cs:disppage
else
    mov    ax, 0B800H        ; this gets corrected in xy_to_regs
                    ; if we are not screen 0
endif
if MONO
    cmp    crt_mode, 7
    jne    not_mono_mode
    mov    ah, 0b0h
not_mono_mode:
endif
    push    cs
    pop    ds
    assume    ds:CODE
    mov    es, ax
    call    xy_to_regs        ; Set DX, DI according to cur_coords.

    ; | If in graphics mode, clear old pseudocursor

    cmp    gmode_flag, 0
    jle    d8_no_cp
    cmp    no_c_flag, 0    ; cursor not previously drawn?
    mov    no_c_flag, 0    ; (reset flag, will be drawn from now on)
    jnz    d8_no_cp    ; not drawn -- don't clear
    cmp    gcursor, 0    ; don't clear if cursor is off, either
    jz    d8_no_cp
    push    cx
    push    dx
    push    di
    draw_gcursor
    pop    di
    pop    dx
    pop    cx

d8_no_cp:

    mov    ah, cur_attrib
    mov    ds, f_cptr_seg        ; get segment of char ptr
    assume    ds:nothing
    cld                ; make sure we'll increment

    ; The Inner Loop: 12+4+4+11+14+2+19= 66 cycles/loop
    ; on 8088; at 4.77 MHz, that gives 16.1 microseconds/loop.
    ; At that speed, it takes 32 milliseconds to fill a screen.

    ; Get a character, put it on the screen, repeat 'til end of line
    ; or no more characters.
    jcxz    f_loopdone        ; if count = 0, we're already done.
    cmp    cs:escvector, 0        ; If in middle of an escape sequence,
    jz    f_tloop
    jmp    f_in_escape        ; jump to escape sequence handler.

f_tloop:; | If in graphics mode, jump to alternate loop
    ; | What a massive kludge!  A better approach would have been
    ; | to collect characters for a "write n chars" routine
    ; | which would handle both text and graphics modes.
    cmp    cs:gmode_flag,0
    jle    f_t_cloop
    jmp    f_g_cloop

    even                ; tiny performance boost
f_t_cloop:
    LODSB                ; get char! (al = ds:[si++])
    cmp    al, 28            ; is it a control char?
    jb    f_control        ;  maybe...
f_t_nctl:
if DOSV
    call    putchar
else
    STOSW                ; Put Char! (es:[di++] = ax)
endif
    dec    dx            ; count down to end of line
    loopnz    f_t_cloop        ; and go back for more.
    jnz    f_loopdone        ; finished execution
f_t_at_eol:
    jmp    f_at_eol        ; at end of line, maybe do a crlf.


f_looploop:
f_ansi_exit:                ; in case we switched into
    loopnz    f_tloop            ; a graphics mode
    jz    f_t_at_eol
;    jmp    f_loopdone

f_loopdone:

    ;--------- All done with write request -----------
    ; DI is cursor address, cursor position in cur_y, dl

    assume    ds:ABS40
    mov    ax, ABS40
    mov    ds, ax

    ; Set cursor position in low memory.

    mov    al, active_page
    cbw
    add    ax, ax
    xchg    bx, ax
    mov    al, max_x
    inc    al
    sub    al, dl
    mov    ah, cur_y
    mov    cursor_posn[bx],ax

    cmp    gmode_flag,0
    jg    pseudocursor        ; In graphics mode, there is
                    ; a pseudo cursor to draw.

if DESQVIEW
    cmp    dvactive,0        ; Desqview running?
    jz    dv_off
    mov    dx, ax            ; call bios to set position
    xor    bx, bx
    mov    ah, 2
    call_video
    xor    ax, ax            ; finished
    ret
dv_off:
endif
    ; Write directly to 6845 cursor address register.
    mov    bx, di
    shr    bx, 1            ; convert word index to byte index

if MONO
    mov    dx, our_6845    ; either mono or color card
else
    mov    dx, port_6845    ; color card
endif
    mov    al,0eh        ; more effective to write two bytes at a time
    mov    ah,bh
    out    dx,ax
    inc    al
    mov    ah,bl
    out    dx,ax


    ; Return to DOS.
    xor    ax, ax            ; No error, not busy.
    ret

pseudocursor:
    cmp    gcursor, 0    ; graphics cursor off?
    jz    nopseudo
    mov    no_c_flag,0    ; there is a cursor now!
    draw_gcursor
nopseudo:
    xor    ax, ax
    ret

    ;---- handle control characters ----
    ; Note: cur_x is not kept updated in memory, but can be
    ; computed from max_x and dx.
    ; Cur_y is kept updated in memory.
f_escapex:                ; far jump
    jmp    f_escape

f_control:
    cmp    al, 27            ; Is it an escape?
    jz    f_escapex
    cmp    al, 13            ; carriage return?
    jz    f_cr
    cmp    al, 10            ; line feed?
    jz    f_lf
    cmp    al, 8            ; backspace?
    jz    f_bs
    cmp    al, 9            ; tab?
    jz    f_tab
    cmp    al, 7            ; bell
    jz    f_bell
    jmp    f_nctl            ; then it is not a control char.

f_bell: ;----- Handle bell ----------------------
    ; Use BIOS to do the beep.  DX is not changed, as bell is nonprinting.
    call    beep
    or    al, al            ; clear z
    jmp    f_looploop        ; Let main loop decrement cx.

f_bs:    ;----- Handle backspace -----------------
    ; Moves cursor back one space without erasing.    No wraparound.
    cmp    dl, cs:max_x        ; wrap around to previous line?
    ja    fbs_wrap        ; yep; disallow it.
    dec    di            ; back up one char & attrib,
    dec    di
    inc    dx            ; and note one more char left on line.
fbs_wrap:
    jmp    f_looploop

f_cr:    ;----- Handle carriage return -----------
    ; di -= cur_x<<1;        set di= address of start of line
    ; dx=max_x+1;            set bx= chars left in line
    mov    al, cs:max_x
    inc    al
    sub    al, dl            ; Get cur_x into ax.
    mov    ah, 0
    sub    di, ax
    sub    di, ax
    mov    dl, cs:max_x        ; Full line ahead of us.
    inc    dx
    mov    ah, cs:cur_attrib    ; restore current attribute
    or    al, 1            ; clear z
    jmp    f_looploop        ; and let main loop decrement cx

f_at_eol:
    ;----- Handle overrunning right end of screen -------
    ; cx++;                compensate for double loop
    ; if (!wrap_flag) { dx++; di-=2; }
    ; else do_crlf;
    inc    cx
    test    cs:wrap_flag, 1
    jnz    feol_wrap
        dec    di
        dec    di
        inc    dx
        jmp    f_looploop
feol_wrap:
    ; dx=max_x+1;            set bx= chars left in line
    ; di -= 2*(max_x+1);
    ; do_lf
    mov    dl, cs:max_x
    inc    dx
    sub    di, dx
    sub    di, dx
    ; fall thru to line feed routine

f_lf:    ;----- Handle line feed -----------------
    ; if (cur_y >= max_y) scroll;        scroll screen up if needed
    ; else { cur_y++; di += max_x<<1;    else increment Y

    mov    al, cs:max_y
    cmp    cs:cur_y, al
    jb    flf_noscroll
        call    scroll_up        ; preserves bx,cx,dx,si,di
        jmp    short flf_done
flf_noscroll:
    inc    cs:cur_y
    mov    al, cs:max_x
    mov    ah, 0
    inc    ax
    add    ax, ax
    add    di, ax
flf_done:
    mov    ah, cs:cur_attrib        ; restore current attribute
    or    al, 1            ; clear z
    jmp    f_looploop        ; and let main loop decrement cx

f_tab:    ;----- Handle tab expansion -------------
    ; Get cur_x into al.
    mov    al, cs:max_x
    inc    al
    sub    al, dl
    ; Calculate number of spaces to output.
    push    cx            ; save cx
    mov    ch, 0
    mov    cl, al            ; get zero based x coordinate
    and    cl, 7
    neg    cl
    add    cl, 8            ; 0 -> 8, 1 -> 8, ... 7 -> 1
    sub    dx, cx            ; update chars-to-eol, maybe set z
    pushf                ; || save Z for main loop
    ; ah is still current attribute.  Move CX spaces to the screen.
    mov    al, ' '
    cmp    cs:gmode_flag,0
    jg    f_tab_putc

    REP    STOSW
    popf                ; || restore Z flag for main loop test
    pop    cx            ; restore cx
    jmp    f_looploop        ; Let main loop decrement cx.

;--------------- graphics mode support -----------------------

;---- Alternate main loop for graphics mode ----
f_g_cloop:
    LODSB                ; get char! (al = ds:[si++])
    cmp    al, 28            ; is it a control char?
    jb    f_g_control        ;  maybe...
f_g_nctl:
    call    putchar
    dec    dx            ; count down to end of line
    loopnz    f_g_cloop        ; and go back for more.
    jz    f_at_eol        ; at end of line; maybe do a crlf.
    jmp    f_loopdone

f_g_control:    jmp    f_control

; Tabs in graphic mode
f_tab_putc:    ; graphics mode- call putc to put the char
    add    dx, cx            ; move back to start of tab
f_tp_lp:
    call    putchar
    dec    dx            ; go to next cursor position
    loop    f_tp_lp
    popf                ; Z set if wrapped around EOL
    pop    cx
    jmp    f_looploop

;---- Where to go when a character turns out not to be special
f_nctl:
f_not_ansi:
    cmp    cs:gmode_flag,0
    jg    f_g_nctl
    jmp    f_t_nctl        ; text mode

page
;---- putchar ------------------------------------------------
; Writes char AL, attribute AH to screen at (max_x+1-dl), cur_y.
; On entry, registers set up as per xy_to_regs.
; Preserves all registers.
putchar proc    near
    push    dx
    push    cx
    push    bx
    push    ax
    ; 1. Set cursor position.
    mov    al, cs:max_x
    inc    al
    sub    al, dl
    mov    cs:cur_x, al
    mov    dx, cs:cur_coords    ; get X & Y into DX
    push    ds
    mov    ax, 40h
    mov    ds, ax
    assume    ds:ABS40
    mov    cursor_posn,dx
    pop    ds
    assume    ds:nothing
    xor    bx, bx            ; choose dpy page 0
    mov    ah, 2            ; chose "Set Cursor Position"
    call_video
    ; 2. Write char & attribute.
IF quick_char
    pop    ax
    push    ax            ; character and attribute
    call    quick_graph
ELSE
    mov    cx, 1
    pop    ax            ; get char in AL
    push    ax
    mov    bl, ah            ; attribute in BL
    mov    bh, 0
    mov    ah, 9
    call_video
ENDIF
    pop    ax
    pop    bx
    pop    cx
    pop    dx
    ret
putchar endp
page
IF quick_char
quick_graph    proc    near
; this code has been reworked for much greater speed.

; ah= mode, al= char, ax,bx,cx,dx destroyed
    gmode_test yesQuick

    mov    bl,ah
    xor    bh,bh
    mov    cx, 1
    mov    ah, 9
    call_video        ; do it the old way
    ret

yesQuick:
    push    ds
    mov    bx, 40h
    mov    ds, bx
    assume    ds:ABS40        ; address abs segment
    push    es
    push    bp
    push    si
    push    di            ; save some registers
    push    ax            ; save char and mode

    mov    ax, crt_cols
    mov    cx, ega_points        ; pixel rows in character
    mov    bp, ax            ; save number of columns=#bytes
    mul    byte ptr (cursor_posn+1)
    mul    cx            ; (ignore upper product in DX)
    add    al, byte ptr (cursor_posn)    ; y*#cols*#rows + x
    adc    ah, 0            ; take care of carry
    mov    si, ax            ; save address in si
    xor    ax, ax
    mov    es, ax            ; absolute zero
    les    di, es: dword ptr (43h * 4)    ; contents of vector 43h
    pop    ax
    push    ax            ; get char and mode
    mul    cl            ; offset to character in table
    add    di,ax            ; di has character bit pattern start
    mov    ax, 0a000h        ; address of display segment
    mov    ds, ax
    assume    ds:nothing

; to recap: cx=#rows, bp=#columns, ds:si=display address, es:di=character addr
    mov    dx, 3ceh
    mov    ax, 0a05h
    out    dx,ax            ; set write mode 2, read mode 1

    mov    ax, 7            ; set color dontcare register to zero
    out    dx,ax

    pop    bx            ; character mode in bh
IF gbackground
    mov    bl,bh            ; extract background color
IF cheap_pc
    shr    bl,1
    shr    bl,1
    shr    bl,1
    shr    bl,1
ELSE
    shr    bl,4
ENDIF
    or    bh, bh
    jns    overMode
    mov    ax, 1803h        ; exor mode
    out    dx,ax

    and    bx, 0f07h        ; xor=blink bit
ELSE
    or    bh, bh
    jns    overMode
    mov    ax, 1803h        ; exor mode
    out    dx,ax

    and    bx, 7f00h        ; mask off xor bit
ENDIF
    mov    al, 8            ; bit mask register
    out    dx, al
    inc    dx
chLoop:
    mov    al, es:[di]        ; get pixel pattern
    out    dx, al
    and    [si],bh            ; update foreground
    not    al
    out    dx, al                 ; and background
    and    [si],bl
    inc    di
    add    si, bp            ; go to next character byte and line
    loop    chLoop

joinret:
    dec    dx
    mov    ax, 0ff08h        ; bit mask
    out    dx, ax
    mov    ax, 5            ; mode register
    out    dx, ax
    mov    al, 3            ; (ah is zero)
    out    dx, ax
    mov    ax, 0f07h
    out    dx, ax

    pop    di
    pop    si
    pop    bp
    pop    es
    pop    ds
    ret

overMode:
IF gbackground
    and    bx, 0f07h        ; xor=blink bit
ELSE
    and    bx, 7f00h        ; mask off xor bit
ENDIF
    mov    al, 8            ; bit mask register
    out    dx, al
    inc    dx
    ; we need to load the internal buffer with a solid
    ; background. By writing a solid background and then
    ; reading it back, we can do the job.
    mov    al, 0ffh        ; force set background
    out    dx, al
    mov    [si], bl
    mov    al, [si]        ; read reset pattern
chLoop2:
    mov    al, es:[di]        ; get pixel pattern
    out    dx, al
    mov    [si],bh            ; update foreground
    inc    di
    add    si, bp            ; go to next character byte and line
    loop    chLoop2
    jmp    joinret

quick_graph endp
ENDIF


;--------------- end of graphics mode support --------------------

dosfn8    endp
page
;--- get_blank_attrib ------------------------------------------------
; Determine new attribute and character for a new blank region.
; Use current attribute, just disallow blink and underline.
; Returns result in AH, preserves all other registers.
get_blank_attrib    proc    near
IF gbackground
    cmp    cs:gmode_flag,0
    jle    get_attrib        ; if alpha mode
    gmode_test get_attribg        ; or good graphic mode, get attrib
    xor    ah,ah
    ret
get_attribg:
    mov    ah, cs:cur_attrib    ; must do different technique
IF cheap_pc
    shr    ah,1            ; color must be shifted into position
    shr    ah,1
    shr    ah,1
    shr    ah,1
ELSE
    shr    ah,4
ENDIF
    and    ah,07
    ret
get_attrib:
    mov    ah, cs:cur_attrib    ; the attribute
;    and    ah, 7fh            ;  but disallowing blink
IF MONO
    cmp    cs:video_mode, 7    ; monochrome?
    jne    gb_aok
    cmp    ah, 7            ; underline?
    jnz    gb_aok
    mov    ah, 7
gb_aok:
ENDIF
    ret
ELSE
    mov    ah, 0            ; 0 is background if graphics mode
    cmp    cs:gmode_flag,0
    jg    gb_aok

    mov    ah, cs:cur_attrib
;    and    ah, 7fh            ; disallow blink
IF MONO
    cmp    cs:video_mode, 7    ; monochrome?
    jne    gb_aok
    cmp    ah, 7            ; underline?
    jnz    gb_aok
    mov    ah, 7
ENDIF
gb_aok: ret
ENDIF
get_blank_attrib    endp

page
;---- scroll_up ---------------------------------------------------
; Scroll screen up- preserves ax, bx, cx, dx, si, di, ds, es.
; Moves screen up 1 line, fills the last line with blanks.
; Attribute of blanks is the current attribute sans blink and underline.

if DOSV
scroll_up    proc    near
        push_all
        push    ds

        mov    ax, ABS40    ; address low mem via ds
        mov    ds, ax
        assume    ds:ABS40

        mov    bh, cs:cur_attrib
        mov    dh, byte ptr ega_rows
                    ; Get max rows of display
        mov    dl, byte ptr crt_cols
        dec    dl        ; lower right in dx

        xor    cx, cx        ; upper left of the screen
        mov    al, 1        ; 1 line scroll
        mov    ah, 06h        ; Scroll up

        call_video

        assume    ds:nothing
        pop    ds
        pop_all
        ret
scroll_up    endp

else                    ; DOSV
scroll_up    proc    near
    push_all

    cmp    cs:gmode_flag,0
    jz    scroll_char
if MONO
    jl    mono_scroll
endif
    jmp    scroll_graphic
scroll_char:
    push    es
    push    ds            ; save all!
    mov    ax, ABS40        ; address low mem via ds
    mov    ds, ax
if DESQVIEW
    mov    ax, cs:disppage
else
    mov    ax, 0b800h        ; address display via es
endif
    mov    es, ax
    assume    ds:ABS40
    cmp    cs:fmode,0        ; see if in fast mode
    jz    slow_scroll_up
    xor    ax,ax            ; calc addresses
    mov    al, cs:max_x
    inc    ax
    mov    cx, ax            ; save (word) count for fill
    mov    bx, ax            ; and save byte count
    shl    bx, 1            ; byte count
    mov    cs:temp_val, bx
    mul    cs:max_y        ; address offset of last line (words)
    shl    ax, 1            ; address offset in bytes
    mov    di, ax

    mov    ax, crt_start        ; start of display
    add    ax, bx            ; add line size in bytes
    add    di, ax            ; di is now address of new last line
    cmp    di, 7fffh - 264        ; is there room here?
    ja    no_room_here

    mov    crt_start, ax
    shr    ax, 1            ; make into word offset
    mov    bx, ax            ; and put into 6845
    mov    dx, port_6845
    mov    al, 0ch
    out    dx, ax
    inc    al
    mov    ah, bl
    out    dx, ax

    mov    ah, cs:cur_attrib
;    and    ah, 7fh            ; disallow blink
    mov    al, 20h            ; blank
    rep stosw            ; clear line

    assume    ds:nothing
    pop    ds
    pop    es
    pop_all

    add    di, cs:temp_val
    ret

no_room_here:
    pop    ds            ; restore registers
    pop    es
    pop_all
    call    move_back        ; go to buffer start
    sub    di, cs:temp_val
    jmp    scroll_up        ; try again

if MONO
mono_scroll:
    push    es
    push    ds            ; save all!
    mov    ax, ABS40        ; address low mem via ds
    mov    ds, ax
    mov    ax, 0b000h        ; address display via es
    mov    es, ax
endif
slow_scroll_up:
    assume    ds:ABS40
    mov    di, crt_start        ; offset of display (because of
                    ;   different page)
    mov    ds, ax            ; ds is now display
    assume    ds:nothing
    xor    ax,ax            ; calc addresses
    mov    al, cs:max_x
    inc    ax
    mov    bx, ax            ; save (word) count
    shl    ax, 1            ; byte count
    mov    si, ax            ; start address is second line
    add    si, di            ; adjust start address by any offset
    mov    ax, bx
    mul    cs:max_y        ; number of words to move
    mov    cx, ax
    rep movsw            ; move them!
    mov    cx, bx            ; words to clear
          mov    ah, cs:cur_attrib
;    and    ah, 7fh            ; disallow blink
    mov    al, 20h            ; blank
    rep stosw            ; clear line
    pop    ds
    pop    es
    pop_all
    ret

scroll_graphic:

    gmode_test scrOurself
    mov    bh, 0
    mov    al, 1            ; AL is number of lines to scroll.
    mov    ah, 6            ; BIOS: scroll up
    xor    cx, cx
    mov    dl, cs:max_x        ; lower-rite-x
    mov    dh, cs:max_y        ; lower-rite-y (zero based)
    call_video            ; call BIOS to scroll a rectangle.

scrret:
    pop_all
    ret

scrOurself:    ; try scrolling screen ourself!
    push    es
    push    ds

    mov    dx, 3ceh        ; set write mode 1
    mov    ax, 105h
    out    dx, ax

    mov    ax, 40h            ; address abs40 segment
    mov    ds, ax
    assume    ds:ABS40
    mov    ax, crt_cols        ; calculate length of line in bytes
    mul    byte ptr ega_points
    mov    si, ax            ; source of move
    xor    dx,dx
    mov    dl, ega_rows
    mul    dx            ; number of bytes to move
    mov    cx, ax
    mov    ax, si            ; save bytes in line for later

    mov    bx, 0a000h        ; address display
    mov    ds, bx
    mov    es, bx

    xor    di, di            ; destination of move
    rep movsb            ; scroll

    mov    cx, ax            ; bytes in line = bytes to clear

    mov    dx, 3ceh
    mov    ax, 05h            ; return to write mode 0
    out    dx, ax

IF gbackground
    mov    ah, cs:cur_attrib
IF cheap_pc
    shr    ah,1
    shr    ah,1
    shr    ah,1
    shr    ah,1
ELSE
    shr    ah,4
ENDIF
    and    ah,07            ; background color
    mov    al,0
    out    dx,ax            ; set color to write

    mov    ax,0f01h        ; set mask
    out    dx,ax

    rep    stosb            ; clear the line

    mov    ax,0001            ; reset mask
    out    dx,ax
ELSE
    xor    ax, ax
    rep stosb            ; clear the line
ENDIF

    pop    ds            ; restore registers and return
    pop    es
    jmp    scrret

scroll_up    endp
endif

page
;-----move_back --------------------------------------------
; This routine moves the display to offset zero.
; alters:
; cs:temp_val = original crt_start value
; crt_start = 0
; controller reset properly
move_back proc near
    push    ds
    push    es
    push_all
    mov    ax, ABS40
    mov    ds, ax

    assume    ds:ABS40
    mov    al, ega_rows
    inc    al
    mul    byte ptr crt_cols    ; words to move
    mov    cx, ax
    mov    si, crt_start
    mov    cs:temp_val, si        ; save this value
    xor    di, di
    mov    crt_start, di
    mov    bx, cursor_posn        ; y in bh, x in bl
    mov    al, byte ptr crt_cols
    mul    bh
    add    al, bl
    adc    ah, 0
    xchg    bx, ax            ; save cursor position in bx

if DESQVIEW
    mov    ax, cs:disppage
else
    mov    ax, 0B800h
endif
    mov    es, ax
    mov    ds, ax

    mov    dx, cx
    add    dx, cx            ; see if overlapping
    cmp    dx, si
    ja    slow_move
join_move:
    cld
    rep movsw            ; move data

    mov    dx, port_6845
    mov    al, 0ch            ; reset offset
    xor    ah,ah
    out    dx, ax
    inc    al
    out    dx, ax
    inc    al
    mov    ah, bh
    out    dx, ax
    inc    al
    mov    ah, bl
    out    dx, ax
    assume    ds:nothing
    pop_all
    pop    es
    pop    ds
    ret

slow_move:    ; we gotta move to another spot first
    push    cx        ; save length
    dec    dx        ; length-2
    dec    dx
    add    si, dx        ; point to end
    mov    di, 7FFEh    ; safe location -- as safe as we can get
    std
    rep movsw        ; move from far end in case of overlap
                ; (may happen on large displays)
    mov    dx, port_6845
    mov    si, di        ; source becomes destination
    inc    si        ; take care of last decrement
    inc    si
    mov    cx, si
    shr    cx, 1        ; word offset to start of new area
    mov    al, 0Ch        ; display at this new location
    mov    ah, ch
    out    dx, ax
    inc    al
    mov    ah, cl
    out    dx, ax
    pop    cx        ; reset all registers
    xor    di, di        ; destination is zero
; The following four lines contributed by Bruce L. Hicks
    add    dx, 6
slow_wait:
    in    al, dx        ; wait for retrace
    test    al, 08h
    jz    slow_wait
    jmp    join_move    ; NOW move to destination

move_back    endp
page
if key_redef
;---- lookup -----------------------------------------------
; Called by getchar, peekchar, and key to see if a given key has
; been redefined.
; Sets AH to zero if AL is not zero (i.e. if AX is not a function key).
; Returns with Z cleared if no redefinition; otherwise,
; Z is set, SI points to redefinition string, CX is its length.
; Preseves AL, all but CX and SI.
; Redefinition table organization:
;  Strings are stored in reversed order, first char last.
;  The word following the string is the character to be replaced;
;  the next word is the length of the string sans header.
; param_end points to the last byte used by the parameter buffer;
; redef_end points to the last word used by the redef table.

lookup    proc    near
    mov    si, redef_end        ; Start at end of table, move down.
    or    al, al
    jz    lu_lp
if ext_keybd
    cmp    ax, 224            ; keyboard code (Alt 224)?
    jz     lu_224
    cmp    al, 224            ; extended code?
    jz    lu_lp
lu_224:
endif
    mov    ah, 0            ; clear extraneous scan code
lu_lp:    cmp    si, param_end
    jbe    lu_notfound        ; If below redef table, exit.
    mov    cx, [si]
    cmp    ax, [si-2]        ; are you my mommy?
    jz    lu_gotit
    sub    si, 4
    sub    si, cx            ; point to next header
    jmp    lu_lp
lu_notfound:
    or    si, si            ; clear Z
    jmp    short lu_exit
lu_gotit:
    sub    si, 2
    sub    si, cx            ; point to lowest char in memory
    cmp    al, al            ; set Z
lu_exit:
    ret
lookup    endp
endif
page
;---- searchbuf --------------------------------------------
; Called by getchar and peekchar to see if any characters are
; waiting to be gotten from sources other than BIOS.
; Returns with Z set if no chars found, BX=keybuf & SI=keybuf.len otherwise.
searchbuf    proc    near
    ; Search the stuffahead buffers.
if key_redef
    mov    cx, 4            ; number of buffers to check for chars
else
    mov    cx, 3
endif
    mov    bx, offset fnkey - 4
sbloop: add    bx, 4            ; point to next buffer record
    mov    si, [bx].len
    or    si, si            ; empty?
    loopz    sbloop            ; if so, loop.
    ret
searchbuf    endp
page
;---- getchar -----------------------------------------------
; Returns AL = next char.
; Trashes AX, BX, CX, BP, SI.
getchar proc    near
gc_searchbuf:
    ; See if any chars are waiting in stuffahead buffers.
    call    searchbuf
    jz    gc_trykbd        ; No chars?  Try the keyboard.
    ; A nonempty buffer was found.
    dec    [bx].len
    dec    si
    mov    bp, [bx].adr        ; get pointer to string
    mov    al, byte ptr ds:[bp][si]; get the char
    ; Recognize function key sequences, move them to highest priority
    ; queue.
    sub    si, 1            ; set carry if si=0
    jc    gc_nofnkey        ; no chars left -> nothing to protect.
    cmp    bx, offset fnkey
    jz    gc_nofnkey        ; already highest priority -> done.
    or    al, al
    jnz    gc_nofnkey        ; nonzero first byte -> not fnkey.
    ; Found a function key; move it to highest priority queue.
    dec    [bx].len
    mov    ah, byte ptr ds:[bp][si]; gec      [bx].len
    mov    ah, byte ptr ds:[bp][si]; get the second byte of fn key code
gc_fnkey:
    mov    fnkey.len, 1
    mov    fnkeybuf, ah        ; save it.
gc_nofnkey:
    ; Valid char in AL.  Return with it.
    jmp    short gcdone

gc_trykbd:
    ; Actually get a character from the keyboard.
if ext_keybd
    mov    ah, 10h
else
    mov    ah, 0
endif
    int    16h            ; BIOS returns with char in AX
    ; If it's Ctrl-break, it has already been taken care of.
    or    ax, ax
    jz    gc_trykbd

if key_redef
    ; Look in the reassignment table to see if it needs translation.
    call    lookup            ; Z=found; CX=length; SI=ptr
    jnz    gc_noredef
    ; Okay; set up the reassignment, and run thru the translation code.
    mov    xlatseq.len, cx
    mov    xlatseq.adr, si
    jmp    gc_searchbuf
endif
gc_noredef:
    ; Is it a function key?
    cmp    al, 0
    jz    gc_fnkey        ; yep- special treatment.
if ext_keybd
    cmp    al, 224            ; check for extended special
    jnz    gcdone
    cmp    ax, 224            ; alt-224?
    jz    gcdone
    xor    al, al            ; if so, make it normal special
    jmp    gc_fnkey
gcdone: ret    ; with character in AL.
endif
getchar endp
page
;---- peekchar -----------------------------------------------
; Returns Z if no character ready, AL=char otherwise.
; Trashes AX, BX, CX, BP, SI.
peekchar    proc    near
    call    searchbuf
    jz    pc_trykbd        ; No chars?  Try the keyboard.
    ; A nonempty buffer was found.
    dec    si
    mov    bp, [bx].adr        ; get pointer to string
    mov    al, byte ptr ds:[bp][si]; get the char
    ; Valid char from buffer in AL.     Return with it.
    jmp    short pcdone
pc_trykbd:
    ; Actually peek at the keyboard.
if ext_keybd
    mov    ah, 11h
else
    mov    ah, 1
endif
    int    16h            ; BIOS returns with char in AX
    jz    pcexit
    ; If it's control-break, it's already been taken care of.
    or    ax, ax
    jnz    pc_notbrk
if ext_keybd
    mov    ah, 10h
else
    mov    ah, 0
endif
    int    16h            ; so get rid of it!
    jmp    short pc_trykbd
pc_notbrk:
if key_redef
    ; Look in the reassignment table to see if it needs translation.
    call    lookup            ; Z=found; CX=length; SI=ptr
    jnz    pcdone            ; Nope; just return the char.
    ; Okay; get the first code to be returned.
    add    si, cx
    mov    al, [si-1]
endif
pcdone: or    ah, 1            ; NZ; char ready!
pcexit: ret    ; with character in AL, Z true if no char waiting.
peekchar    endp
page
;----- set_gmode ------------------------------------------------
; Set gmode_flag based on mode byte in register al
set_gmode proc  near
if MONO
    cmp    al, 7            ; mono?
    je    gmode_mono
    gmode_code
    ret
gmode_mono:
    neg    al
    mov    cs:gmode_flag, al    ; set gmode_flag to neg value
    ret
else
    gmode_code            ; a macro in nnansi_d.asm
    ret
endif
set_gmode    endp


;---- beep ------------------------------------------------------
; Beep speaker; period given by beep_div, duration by beep_len.
; Preserves all registers.

beep_div    equ    1300        ; fairly close to IBM beep
beep_len    equ    3        ; 3/18 sec- shorter than IBM

beep    proc    near
    push_all

    mov    al, 10110110b        ; select 8253
    mov    dx, 43h            ; control port address
    out    dx, al
    dec    dx            ; timer 2 address
    mov    ax, beep_div
    jmp    $+2
    out    dx, al            ; low byte of divisor
    xchg    ah, al
    jmp    $+2
    out    dx, al            ; high byte of divisor
    mov    dx, 61h
    jmp    $+2
    in    al, dx            ; get current value of control bits
    push    ax
    or    al, 3
    jmp    $+2
    out    dx, al            ; turn speaker on

    ; Wait for desired duration by monitoring time-of-day 18 Hz clock
    push    es
    mov    ax, ABS40
    mov    es, ax
    assume    es:ABS40
    mov    bx, timer_low
    mov    cx, -1
beeplp: mov    ax, timer_low
    sub    ax, bx
    cmp    ax,     beep_len
    jg    beepover
    loop    beeplp
beepover:
    pop    es
    assume    es:CODE

    ; Turn off speaker
    pop    ax
    and    al, not 3        ; turn speaker off
    out    dx, al
    pop_all
    ret
    assume    es:nothing
beep    endp

    page
; A state machine implementation of the mechanics of ANSI terminal control
; string parsing.
;
; Entered with a jump to f_escape when driver finds an escape, or
; to f_in_escape when the last string written to this device ended in the
; middle of an escape sequence.
;
; Exits by jumping to f_ANSI_exit when an escape sequence ends, or
; to f_not_ANSI when a bad escape sequence is found, or (after saving state)
; to f_loopdone when the write ends in the middle of an escape sequence.
;
; Parameters are stored as bytes in param_buffer.  If a parameter is
; omitted, it is stored as zero.  Each character in a keyboard reassignment
; command counts as one parameter.
;
; When a complete escape sequence has been parsed, the address of the
; ANSI routine to call is found in ansi_fn_table.
;
; Register usage during parsing:
;  DS:SI points to the incoming string.
;  CX holds the length remaining in the incoming string.
;  ES:DI points to the current location on the memory-mapped screen.
;  DX is number of characters remaining on the current screen line.
;  BX points to the current paramter byte being assembled from the incoming
;  string.  (Stored in cur_parm_ptr between device driver calls, if needed.)
;
; The registers are set as follows before calling the ANSI subroutine:
;  AX = max(1, value of first parameter)
;  CX = number of paramters
;  SI = offset of second parameter from CS
;  DS = CS
;  ES:DI points to the current location on the memory-mapped screen.
;  DX is number of characters remaining on the current screen line.
; The subroutine is free to trash AX, BX, CX, SI, and DS.
; It must preserve ES, and can alter DX and DI if it wants to move the
; cursor.
;
;------------------------------------------------------------------------

    assume    cs:code, ds:code

;----- next_is -------------------------------------------------------
; Next_is is used to advance to the next state.     If there are characters
; left in the input string, we jump immediately to the new state;
; otherwise, we shut down the recognizer, and wait for the next call
; to the device driver.
next_is macro    statename
    loop    statename
    mov    ax, offset statename
    jmp    sleep
    endm

;----- f_in_escape ---------------------------------------------------
; Main loop noticed that escvector was not zero.
; Recall value of BX saved when sleep was jumped to, and jump into parser.
f_in_escape:
    mov    bx, cs:cur_parm_ptr
    jmp    word ptr cs:escvector

fbr_syntax_error_gate:        ; jumped to from inside f_bracket
    jmp    syntax_error

;----- sleep --------------------------------------------------------
; Remember bx and next state, then jump to device driver exit routine.
; Device driver will re-enter at f_in_escape upon next invocation
; because escvector is nonzero; parsing will then be resumed.
sleep:    mov    cs:cur_parm_ptr, bx
    mov    cs:escvector, ax
    jmp    f_loopdone

;----- f_escape ------------------------------------------------------
; We found an escape.  Next character should be a left bracket.
f_escape:
    next_is f_bracket

;----- f_bracket -----------------------------------------------------
; Last char was an escape.  This one should be a [; if not, print it.
; Next char should begin a parameter string.
f_bracket:
    lodsb
    cmp    al, '['
    jnz    fbr_syntax_error_gate
    ; Set up for getting a parameter string.
    mov    bx, cs:param_buffer
    xor    al,al            ; zero
    mov    byte ptr cs:[bx], al    ; default first char
    dec    bx            ; point buffer before start
    mov    cs:eat_key, al        ; no eaten key
    next_is f_get_args

;----- f_get_args ---------------------------------------------------
; Last char was a [.  If the current char is a '=' or a '?', save
; it for SET/RESET MODE, and then proceed to f_get_param.
f_get_args:
    lodsb
    cmp    al, '='
    je    fga_ignore
    cmp    al, '?'
    jne    f_get_param2
fga_ignore:
    mov    cs:eat_key, al        ; save = or ?
    next_is f_get_param

;----- f_get_param ---------------------------------------------------
; Last char was one of the four characters "]?=;".
; We are getting the first digit of a parameter, a quoted string,
; a ;, or a command.
f_get_param:
    lodsb
f_get_param2:    ; jump to here if no fetch of character
    cmp    al, '0'
    jb    fgp_may_quote
    cmp    al, '9'
    ja    fgp_may_quote
        cmp    bx, cs:param_end    ; if bx <param_end bx++
        adc    bx, 0
        ; It's the first digit.     Initialize parameter with it.
        sub    al, '0'
        mov    byte ptr cs:[bx], al
        next_is f_in_param
fgp_may_quote:
    cmp    al, '"'
    je    fgp_isquote
    cmp    al, "'"
    jne    fgp_semi_or_cmd        ; jump to code shared with f_in_param
fgp_isquote:
    mov    cs:string_term, al    ; save it for end of string
    next_is f_get_string        ; and read string into param_buffer

fgp_semi_or_cmd:
    cmp    al, ';'            ; is it a semi?
    jnz    fgp_cmd            ; no, then it's a command
    xor    ax, ax            ; zero
    cmp    bx, cs:param_end    ; if bx < param_end bx++
    adc    bx, ax
    mov    byte ptr cs:[bx], al    ; it is a zero parameter
f_goto_next:
    next_is    f_get_param

;----- f_get_string -------------------------------------
; Last character was a quote or a string element.
; Get characters until ending quote found.
f_get_string:
    lodsb
    cmp    al, cs:string_term
    je    fgs_init_next_param
    cmp    bx, cs:param_end
    adc    bx, 0            ; if bx<param_end bx++;
    mov    byte ptr cs:[bx], al
    next_is f_get_string
; Ending quote was found.
fgs_init_next_param:
    next_is f_eat_semi

;----- f_eat_semi -------------------------------------
; Last character was an ending quote.
; If this char is a semi, eat it
; Then goto f_get_param
f_eat_semi:
    lodsb
    cmp    al, ';'
    jnz    f_get_param2
    jmp    f_goto_next

;----- syntax_error ---------------------------------------
; A character was rejected by the state machine.  Exit to
; main loop, and print offending character.  Let main loop
; decrement CX (length of input string).
syntax_error:
    mov    cs:escvector, 0
    mov    ah, cs:cur_attrib
    jmp    f_not_ANSI    ; exit, print offending char

;------ f_in_param -------------------------------------
; Last character was a digit.
; Looking for more digits, a semicolon, or a command character.
f_in_param:
    lodsb
    cmp    al, '0'
    jb    fgp_not_digit
    cmp    al, '9'
    ja    fgp_not_digit
        ; It's another digit.  Add into current parameter.
        sub    al, '0'
        xchg    byte ptr cs:[bx], al
        push    dx
        mov    dl, 10
        mul    dl
        pop    dx
        add    byte ptr cs:[bx], al
        next_is f_in_param
fgp_not_digit:
    cmp    al, ';'
    je    f_goto_next
fgp_cmd:
    ; It must be a command letter.
    cmp    al, '@'
    jb    syntax_error
    cmp    al, 'z'
    ja    syntax_error
    cmp    al, 'Z'
    jbe    fgp_is_cmd
    cmp    al, 'a'
    jb    syntax_error
        ; It's a lower-case command letter.
        ; Remove hole between Z and a to save space in table.
        sub    al, 'a'-'['
fgp_is_cmd:
    ; It's a command letter.  Save registers, convert letter
    ; into address of routine, set up new register usage, call routine.
    push    si            ; These three registers hold info
    push    cx            ; having to do with the input string,
    push    ds            ; which has no interest at all to the
                    ; control routine.

    push    cs
    pop    ds            ; ds is now cs

    cbw
    add    ax, ax            ; table offset

    mov    cx, bx
    mov    si, param_buffer    ; si is now pointer to parameters
    sub    cx, si
    inc    cx            ; cx is now # of parameters
    xchg    ax, bx            ; save pointer to routine in bx

    ; Calculate cur_x from DX.
    mov    al, max_x
    inc    ax
    sub    al, dl
    mov    cur_x, al

    ; Get first parameter into AX; if defaulted, set it to 1.
    xor    ax, ax
    lodsb
    cmp    cx, 1        ; no args?
    adc    al, ah        ; if cx=0, then ax=1
    ; Finally, call the command subroutine.
    call    word ptr (ansi_fn_table-2*'@') [bx]

    pop    ds
    pop    cx
    pop    si

    mov    ah, cs:cur_attrib    ; Prepare for STOSW.
    mov    cs:escvector, 0        ; No longer parsing escape sequence.
    ; Set flags for reentry at loopnz
    or    dx, dx            ; "Any columns left on line?"
    ; Re-enter at bottom of main loop.
    jmp    f_ANSI_exit

    page
; The ANSI control subroutines.

; Each routine is called with the following register usage:
;  AX = max(1, value of first parameter)
;  Z flag is set if first parameter is zero.
;  CX = number of paramters
;  SI = offset of second parameter from CS
;  DS = CS
;  ES:DI points to the current location on the memory-mapped screen.
;  DX is number of characters remaining on the current screen line.
; The control routine is free to trash AX, BX, CX, SI, and DS.
; It must preserve ES, and can alter DX and DI if it wants to move the
; cursor.

;----------------------------------------------------------------

    assume    cs:code, ds:code

;----- byteout ---------------------------------------------------
; Converts al to a decimal ASCII string (in 0..99),
; stores it at ES:DI++.     Returns DI pointing at byte after last digit.
; Destroys DL.

byteout proc    near
    cmp    al, 100        ; check for >99 case -- TAA mod
    jb    goodbyteout
    push    ax
    mov    al, '1'        ; assume value <200!
    stosb
    pop    ax
    sub    ax, 100
goodbyteout:
    aam
    add    ax, 3030h
    xchg    ah, al
    stosb
    xchg    ah, al
    stosb
    ret
byteout endp

;----- ansi_fn_table -----------------------------------
; Table of offsets of terminal control subroutines in order of
; the character that invokes them, @..Z, a..z.    Exactly 53 entries.
; All the subroutines are defined below in this module.
ansi_fn_table    label    word
    dw    ic,  cup, cdn, cfw, cbk        ; @, A, B, C, D
    dw    nul, nul, nul, hvp, nul        ; E, F, G, H, I
    dw    eid, eil, il,  d_l, nul        ; J, K, L, M, N
    dw    nul, dc,  nul, nul, nul        ; O, P, Q, R, S
    dw    nul, nul, nul, nul, nul        ; T, U, V, W, X
    dw    nul, nul            ; Y, Z
    dw    nul, nul, nul, nul, nul        ; a, b, c, d, e
    dw    hvp, nul, sm,  nul, nul        ; f, g, h, i, j
    dw    nul, rm,  sgr, dsr, nul        ; k, l, m, n, o
if key_redef
    dw    key, nul, nul, scp, nul        ; p, q, r, s, t
else
    dw    nul, nul, nul, scp, nul        ; p, q, r, s, t
endif
    dw    rcp, nul, nul, nul, nul        ; u, v, w, x, y
    dw    nul                ; z

ansi_functions    proc    near        ; set return type to NEAR


;----- Cursor Motion -----------------------------------------------

;-- cursor to y,x
hvp:    dec    ax        ; Convert Y to zero-based coordinates.
    mov    cur_y, al
    ; Get second parameter, if it is there, and set X with it.
    xor    ax, ax
    cmp    cx, 2        ; was there a second parameter?
    jb    hvp_xok
    lodsb            ; yes.
    or    al, al
    jz    hvp_xok
    dec    ax        ; convert to zero-based coordinates.
hvp_xok:mov    cur_x, al

    ; Clip to maximum coordinates.
hvp_set:
    mov    ax, cur_coords        ; al = x, ah = y
    cmp    al, max_x
    jbe    hvp_sxok
    mov    al, max_x
    mov    cur_x, al
hvp_sxok:
    cmp    ah, max_y
    jbe    hvp_syok
    mov    al, max_y
    mov    cur_y, al
hvp_syok:
    ; Set values of DX and DI accordingly.
    call    xy_to_regs
    ret

;-- cursor forward --
cfw:    add    cur_x, al
    jmp    hvp_set

;-- cursor back -----
cbk:    sub    cur_x, al
    jae    hvp_set
    mov    cur_x, 0
    jmp    hvp_set

;-- cursor down -----
cdn:    add    cur_y, al
    jmp    hvp_set

;-- cursor up -------
cup:    sub    cur_y, al
    jae    hvp_set
    mov    cur_y, 0
    jmp    hvp_set

;-- save cursor position --------------------------------------
scp:    mov    ax, cur_coords
    mov    saved_coords, ax
    ret

;-- restore cursor position -----------------------------------
rcp:    mov    ax, saved_coords
    mov    cur_coords, ax
    jmp    hvp_set        ; Clip in case we have switched video modes.

;-- set graphics rendition ------------------------------------
; Modifies the color in which new characters are written.


sgr:    dec    si        ; get back pointer to first parameter
    or    cx, cx        ; Did he give any parameters?
    jnz    sgr_loop
    mov    byte ptr [si], 0    ; no parameters, so fake
    inc    cx            ; one with the default value.
    ; For each parameter
sgr_loop:
    lodsb                ; al = next parameter
    ; Search color table
    push    cx

    cmp    al, 0            ; not reset?
    jnz    sgr_continue
    mov    color_flag, 7        ; finish up normally
sgr_continue:
    mov    cx, colors
    mov    bx, offset color_table-3
sgr_search:
    add    bx, 3
    cmp    al, byte ptr [bx]
    loopnz    sgr_search    ; until match found or done
    jnz    sgr_loopx

    ; If parameter named a known color, set the current
    ; color variable.
    cmp    al, 30
    jge    sgr_color
    mov    ax, [bx+1]
    and    atr_flag, al
    or    atr_flag, ah
    jmp    short sgr_loopx
sgr_color:
    mov    ax, [bx+1]
    and    color_flag, al
    or    color_flag, ah
sgr_loopx:
    pop    cx
    loop    sgr_loop        ; until no more parameters.

    mov    al, color_flag
    mov    ah, atr_flag
    test    ah, 4            ; invisible
    jz    sgr_notinv
    mov    ah, al            ; then fade to background
if cheap_pc
    ror    al,1            ; swap nibbles
    ror    al,1
    ror    al,1
    ror    al,1
else
    ror    al,4
endif
    and    ax, 7007h
    or    al, ah
    jmp    short sgr_done
sgr_notinv:
    test    ah, 2            ; reverse?
    jz    sgr_notrev
if cheap_pc
    ror    al,1            ; swap nibbles
    ror    al,1
    ror    al,1
    ror    al,1
else
    ror    al,4
endif
sgr_notrev:
    test    ah, 1            ; underline?
    jz    sgr_notund
    cmp    gmode_flag, 0        ; monochrome display?
    jl    sgr_mono_und
    and    al, 0f0h
    or    al, 1            ; blue chars on color display
    jmp    short sgr_notund

sgr_mono_und:
    cmp    al, 7            ; can only underline if white on black
    jne    sgr_notund
    mov    al, 1
sgr_notund:
    and    ah, 88h            ; get bold and blink attributes
    or    al, ah            ; and  merge them in
sgr_done:
    mov    cur_attrib, al        ; save the new attribute
;    ret

;----- nul ---------------------------------------------
; No-action ansi sequence; called when unknown command given.
nul:    ret


;-- erase in line ----------------------------------------
; Uses BIOS to scroll away a one-line rectangle
eil:    push    dx
    mov    cx, cur_coords
    mov    dh, ch
    jmp    short scrollem

;-- erase in display -------------------------------------
; Uses BIOS to scroll away all of display
eid:
    or    cx,cx        ; no args?
    jz    eid_toend    ;  then erase to end
    cmp    byte ptr -1[si], 0
    je    eid_toend    ; first parms=0 -- erase to end
    cmp    al, 1        ; erase to beginning?
    je    eid_tostart
    cmp    al, 2
    jne    eid_ignore    ; param must be two
    mov    cur_coords, 0
    call    xy_to_regs
    cmp    fmode,0        ; see if running in fast mode
    je    eid_slow
    xor    di, di        ; reset pointer to start
eid_slow:
    push    dx
    xor    cx, cx
    mov    dh, max_y
scrollem:
    call    get_blank_attrib
    mov    bh, ah
    mov    dl, max_x
eid_process:
    mov    ax, 600h
    int    10h        ; don't do call-video here
eid_done:
    pop    dx
eid_ignore:
    ret

eid_toend:    ; erase following lines then go back and erase in line
    push    dx
    call    get_blank_attrib
    mov    bh,ah
    mov    ax, 600h
    mov    dh, max_y
    mov    dl, max_x
    mov    ch, cur_y
    inc    ch
    cmp    ch, dh            ; don't erase if no following
    ja    eid_nopost
    xor    cl,cl
if BAD_ERASE
    int     10h
else
    call_video
endif
eid_nopost:
    mov    cx, cur_coords
    mov    dh, ch
    jmp    short scrollem


eid_tostart:    ; erase preceeding lines then go back and erase in line
    push    dx
    call    get_blank_attrib
    mov    bh,ah
    mov    dh, cur_y
    dec    dh
    js    eid_nopre        ; don't erase if no preceeding
    mov    ax,600h
    xor    cx,cx
    mov    dl, max_x
if BAD_ERASE
    int    10h
else
    call_video
endif
eid_nopre:
    mov    dx, cur_coords
    dec    dl
    js    eid_done
    mov    ch, dh
    xor    cl, cl
    jmp    eid_process

;-- device status report --------------------------------
; Stuffs an escape, a left bracket, current Y, semicolon, current X,
; a capital R, and a carriage return into input stream.
; The coordinates are 1 to 3 decimal digits each.

dsr:    push    di
    push    dx
    push    es
    mov    ax, cs
    mov    es, ax
    std            ; Store string in reversed order for fun
    mov    di, offset cpr_esc - 2
    mov    al, cur_y
    inc    al        ; convert to one-based coords
    call    byteout        ; row
    mov    al, ';'        ; ;
    stosb
    mov    al, cur_x
    inc    al        ; convert to one-based coords
    call    byteout        ; column
    mov    al, 'R'        ; R ANSI function 'Cursor Position Report'
    stosb
    mov    al, 13
    mov    word ptr cprseq.adr, di ; save pointer to last char in string
    stosb                ; send a carriage return, too
    mov    ax, offset cpr_esc
    sub    ax, di            ; ax is # of characters in string
    mov    word ptr cprseq.len, ax ; pass info to the getchar routine
    cld
    pop    es
    pop    dx
    pop    di
    ret
if key_redef
;-- keyboard reassignment -------------------------------
; Key reassignment buffer is between param_end and redef_end+2, exclusive.
; When it shrinks or grows, param_end is moved.
; Format of an entry is as follows:
;   highest address -> length:word (may be 0)
;               key to replace:word     (either hi or low byte is zero)
;               .
;               .    new key value, "length" bytes long
;               .
;   lowest address  -> next entry, or free space.
; If no arguments are given, keyboard is reset to default condition.
; Otherwise, first parameter (or first two, if first is 0 or 224) defines
; the key whose value is to be changed, and the following parameters
; define the key's new, possibly zero-length, value.

key:
    ; Is this a reset?
    or    cx, cx
    jz    key_init
    ; Get the first (or first two) parameters
    cld
    dec    si    ; point to first param
    dec    cx    ; Assume it's a fn key, get two params
    dec    cx
    lodsw
    or    al, al    ; Is it a function key?
    jz    key_fnkey
if ext_keybd
    cmp    al, 224    ; check for extended key
    je    key_fnkey    ; yes -- extended function key
; Note -- ALT 224 cannot be redefined since it would cause ambiguities.
endif
        ; It's not a function key- put second param back
        inc    cx
        dec    si
key_fnkey:
    ; Key to redefine now in AX.  If it's already redefined,
    ; lookup will set Z, point SI to redef string, set CX to its length.
    push    di
    push    es
    push    cx
    push    si

    std            ; moving up, must move from top down
    push    ds
    pop    es        ; string move must have ES=DS
    call    lookup        ; rets Z if redefined...
    jnz    key_newkey
    ; It's already defined.     Erase its old definition- i.e., move
    ; region param_end+1..SI-1 upwards CX+4 bytes, add CX+4 to param_end.
    add    cx, 4
    mov    bp, param_end    ; save old value in bp...
    add    param_end, cx
    dec    si        ; start at (SI-1)
    mov    di, si
    add    di, cx        ; move to (start + CX+4)
    mov    cx, si
    sub    cx, bp        ; length of region old_param_end+1..start
    rep    movsb
key_newkey:
    ; Key not redefined.  See if there's enough room to redefine it.
    pop    si        ; get back pointer to redef string
    pop    cx        ; get back number of bytes in redef string
; The following four lines represent a bug fix provided by Chaim Frenkel,
; [e-mail]
;    cmp    cx,1
;    jle    key_noadjust
;    dec    cx
;key_noadjust:
    mov    di, param_end    ; hi byte of new redef record, hi byte of len
    sub    di, 4        ; hi byte of new data field
    mov    bx, di
    sub    bx, cx        ; hi byte of remaining buffer space
    sub    bx, 16        ; better be at least 16 bytes room
    cmp    bx, param_buffer
    jb    key_popem    ; nope- forget it.
    ; Nothing in the way now!
    mov    [di+3], cx    ; save length field
    mov    [di+1], ax    ; save name field
    jcxz    key_nullstring
key_saveloop:            ; save data field
    movsb
    add    si, 2        ; input string ascending, output descending
    loop    key_saveloop
key_nullstring:
    mov    param_end, di    ; save adr of new hi byte of free area
key_popem:
    pop    es
    pop    di

key_exit:
    cld
    ret

key_init:
    ; Build the default redefinition table:
    ;    control-printscreen -> control-P
    push    es
    push    ds
    pop    es
    cld            ; rewritten routine courtesy of
                ; [e-mail]
    mov    di, param_buffer
    add    di, buf_size
    mov    param_end, di
    inc    di
    mov    al, 16        ; control p
    stosb
    mov    ax, 7200h    ; control-printscreen
    stosw
    mov    ax, 1
    mov    redef_end, di
    stosw
    pop    es
    jmp    key_exit
endif


;---- Delete/Insert Lines -------------------------------
; AL is number of lines to delete/insert.
; Preserves DX, DI; does not move cursor.

d_l:    ; Delete lines.
    mov    ah, 6            ; BIOS: scroll up
    jmp    short il_open

il:    ; Insert lines.
    mov    ah, 7            ; BIOS: scroll down

il_open:
    ; Whether inserting or deleting, limit him to (max_y - cur_y) lines;
    ; if above that, we're just clearing; set AL=0 so BIOS doesn't burp.
    mov    bh, max_y
    sub    bh, cur_y
    cmp    al, bh
    jbe    il_ok            ; DRK 9/4...
        mov    al, 0        ; he tried to move too far
il_ok:
    push    ax
    call    get_blank_attrib
    mov    bh, ah            ; color to use on new blank areas
    pop    ax            ; AL is number of lines to scroll.

    mov    cl, 0            ; upper-left-x of data to scroll
    mov    ch, cur_y        ; upper-left-y of data to scroll
    push    dx
    mov    dl, max_x        ; lower-rite-x
    mov    dh, max_y        ; lower-rite-y (zero based)
if BAD_ERASE
    int    10h
else
    call_video            ; call BIOS to scroll a rectangle.
endif
    pop    dx
    ret                ; done.

;-- Insert / Delete Characters ----------------------------
; AL is number of characters to insert or delete.
; Preserves DX, DI; does not move cursor.

ic:    mov    ch, 1            ; 1 => swap dest & source below
    jmp    short dc_ch

dc:    mov    ch, 0

dc_ch:
    cmp    cs:gmode_flag,0
    jg    dc_ret            ; | if in graphics mode, ignore.


    ; AL = number of chars to ins or del (guarenteed nonzero).
    ; Limit him to # of chars left on line.
    cmp    al, dl
    jbe    dc_cok
        mov    al, dl
dc_cok:
    push    di            ; DI is current address of cursor
    xchg    ax, cx            ; CX gets # of chars to ins/del
    mov    bp, cx            ; BP gets # of columns to clear.

    ; Set up source = destination + cx*2, count = dx - cx
    mov    ch, 0            ; make it a word
    mov    si, di
    add    si, cx
    add    si, cx
    neg    cl
    add    cl, dl
    mov    ch, 0            ; CX = # of words to transfer
    cld                ; REP increments si & di

    ; If this is an insert, then flip transfer around in both ways.
    test    ah, 1
    jz    dc_noswap
        xchg    di, si        ; source <-> dest
        std            ; up <-> down
        mov    ax, cx        ; make move over same range
        dec    ax
        add    ax, ax        ; AX=dist from 1st to last byte.
        add    di, ax        ; Start transfer at high end of block
        add    si, ax        ;  instead of low end.
dc_noswap:
    ; Move those characters.
    push    es
    pop    ds
    rep    movsw
    mov    cx, bp
    ; Figure out what color to make the new blanks.
    call    get_blank_attrib
    mov    al, ' '
    ; Blank out vacated region.
    rep    stosw

    ; All done.
    cld                ; restore normal REP state and
    pop    di            ;  cursor address.
dc_ret: ret


;---- set / reset mode ---------------------------------------
; Sets graphics/text mode; also sets/resets "no wrap at eol" mode.
; also set/reset graphic cursor mode
rm:    mov    cl, 0        ; reset
    jmp    short sm_rs

sm:    mov    cl, 0ffh    ; set
sm_rs:
    ; Is it "wrap at eol" ?
    cmp    al, 7
    jnz    sm_notwrap
    mov    wrap_flag, cl    ; true = wrap at EOL
    ret
sm_notwrap:
; We will make this smarter by requiring the correct lead character,
; except for wrap at eol, which has been badly documented in the MSDOS
; manuals.
    cmp    eat_key, '='    ; set mode -- display mode
    jz    sm_notbios
    cmp    eat_key, '?'    ; set mode of togglable attribute?
    jnz    sm_done
    ; Is it set/reset graphic cursor mode?
    cmp    al,99
    jnz    sm_notgcursor
    mov    gcursor, cl
    ret
sm_notgcursor:
    ; Is it set/reset fast mode?
    cmp    al,98
    jnz    sm_notspeedy
if DESQVIEW
    cmp    dvactive, 0    ; desqview active?
    jne    sm_done        ; then do nothing
endif
    mov    fmode, cl
    or    cl,cl        ; mode now fast?    (was cmp cl,0)
    jnz    sm_done
    call    move_back
sm_done:    ret
sm_notspeedy:
    ; Is it set/reset bios write?
    cmp    al,97
    jnz    sm_done
if bios_write_tty
        mov    bmode, cl
endif
        ret
sm_notbios:
    ; we can now do 43 lines on a VGA display, if desired, as well as 50.
    ; of course an EGA display will only do 43.
IF MONO
    cmp    video_mode, 7        ; mono mode?
    je    sm_done
ENDIF
IF VGA
    cmp    al, 43
    je    is43or50
    cmp    al, 50
    jne    sm_video        ; set to whatever it happens to be
is43or50:
    dec    al
    cmp    al, max_y
    je    sm_done            ; no change in # lines
    cmp    video_mode, 3        ; display mode > 3?
    ja    sm_done
    cmp    al, 49            ; 50 line mode?
    mov    ax, 1201H        ; set 350 lines on EGA
    jne    sm_is43
    mov    ax, 1202h        ; select 400 scan lines
sm_is43:
    mov    bl,30h            ; this call ignored on EGA
    call_video

ELSE
    cmp    al, 43
    jne    sm_video        ; set to whatever it happens to be

    cmp    max_y, 42        ; no change in # lines?
    je    sm_done
    cmp    video_mode, 3        ; must be currently mode <= 3
    ja    sm_done
ENDIF
    mov    ah,0
    mov    al, video_mode        ; select the video mode.
    call_video

    mov    ax,1112h        ; Load 8x8 font
    mov    bl,0            ; (instead of 8x14 or 8x16)
    call_video

    mov    ax, 1200h        ; Load new printscreen
    mov    bl, 20h
    call_video

IF EGA    ; set the EGA cursor
    mov    dx, port_6845        ; '6845' command reg
    mov    ax, 070ah        ; start on line 7
    out    dx, ax
    mov    al, 0bh            ; end on line 7
    out    dx, ax
ENDIF
    jmp    short sm_home


sm_video:
    ; It must be a video mode.  Call BIOS.
    ; Save graphics mode flag
IF VGA
    cmp    al, 3        ; On VGA, modes 0-3, set 400 scan lines
    ja    no_scan_change
    push    ax
    mov    ax, 1202h        ; select 400 scan lines
    mov    bl,30h            ; this call ignored on EGA
    call_video
    pop    ax
no_scan_change:
ENDIF
IF VESA
    cmp    al, 80h        ; not a vesa mode?
    jb    normal_mode
    xor    bx, bx
    mov    bl, al
    add    bx, 8080h    ; set msb and put mode in range
    mov    ax, 4f02h
    int    10h        ; can't use call_video, because often
                ; VESA compatibility driver is used and
                ; loaded after us.
    jmp    short sm_home
normal_mode:
ENDIF
    mov    ah, 0        ; "set video mode"
;    or    al, 80h        ;  but don't erase screen, since colors wrong.
    call_video
sm_home:
    ; Read the BIOS buffer address/cursor position variables.
    mov    ax, ABS40
    push    ds
    mov    ds, ax
    assume    ds:ABS40

    ; Find current video mode and screen size.
    mov    ax,word ptr crt_mode    ; al = crt mode; ah = # of columns
    mov    cl, ega_rows        ; cl = max row
    pop    ds
    assume    ds:code
    call    set_gmode        ; set gmode based on video mode
    mov    video_mode, al
    dec    ah            ; ah = max column
    mov    max_x, ah
    mov    max_y, cl

    ; Since cursor may end up in illegal position, it's best to
    ; just go home after switching video modes.
    mov    cur_coords, 0
    call    xy_to_regs

    jmp    eid_slow        ; then clear the screen

ansi_functions    endp    ; end dummy procedure block



;-------- Color table -----------------------------------------
; Used in "set graphics rendition"

colors    equ    28            ; number of colors in table

color_table:
; The first set attributes rather than colors
    db    0, 000h,00h        ; all attribs off; normal.
    db    1, 0ffh,08h        ; bold
    db    2, 0f7h,00h        ; dim (not bold)
    db    4, 0ffh,01h        ; underline
    db    5, 0ffh,80h        ; blink
    db    7, 0ffh,02h        ; reverse
    db    8, 0ffh,04h        ; invisible

    db    22,0f7h,00h        ; un-bold, un-dim
    db    24,0feh,00h        ; un-underline
    db    25,07fh,00h        ; un-blink
    db    27,0fdh,00h        ; unreverse
    db    28,0fbh,00h        ; un-invisible

; These set the colors
    db    30,0f8h,00h        ; black foreground
    db    31,0f8h,04h        ; red
    db    32,0f8h,02h        ; green
    db    33,0f8h,06h        ; yellow
    db    34,0f8h,01h        ; blue
    db    35,0f8h,05h        ; magenta
    db    36,0f8h,03h        ; cyan
    db    37,0f8h,07h        ; white

    db    40,08fh,00h        ; black background
    db    41,08fh,40h        ; red
    db    42,08fh,20h        ; green
    db    43,08fh,60h        ; yellow
    db    44,08fh,10h        ; blue
    db    45,08fh,50h        ; magenta
    db    46,08fh,30h        ; cyan
    db    47,08fh,70h        ; white

    page
;-------- dos function # 0 : init driver ---------------------
; Initializes device driver interrupts and buffers, then
; passes ending address of the device driver to DOS.
; Since this code is only used once, the buffer can be set up on top
; of it to save RAM. Placed at end so that any excess can be deleted
; after running

dosfn0    proc    near
    assume    cs:code, ds:code
if TSR
    mov    word ptr nextdev, -1    ; fix up next device pointer
    mov    word ptr nextdev+2, -1
joindosfn0:
endif
    mov    byte ptr cs:IDLOC+10, '*' ; make us look different

; The following check for MDA/CGA courtesy of Arend van den Brug
                    ; initialise ega_rows to normal value
                    ; to enable MDA/CGA support
    mov    ax, ABS40
    mov    ds, ax
    assume    ds:ABS40
    mov    al, ega_rows
    or    al, al            ; not already filled in ?
    jnz    set_kb
    mov    ega_rows, 24        ; then set it to the normal 25 lines

set_kb:
if 0
    ; this is old, ugly code that DOS manuals say would be necessary
    ; but I've found not to be the case. But if I'm wrong, and the system
    ; hangs during boot, then here is the ugly alternative.

    ; Install BIOS keyboard break handler.
    xor    ax, ax
    mov    ds, ax
    assume    ds:NOTHING
    mov    bx, 1bh * 4
if TSR
    cmp    cs:fulldvr, 0
    je    nosetbrk
    mov    ax, [bx]
    mov    word ptr cs:old_brk, ax
    mov    ax, [bx+2]
    mov    word ptr cs:old_brk[2], ax
endif
    mov    word ptr [BX],offset break_handler
    mov    [BX+02], cs
nosetbrk:

    ; Install INT 29 quick putchar.
    mov    bx, 029h * 4
if TSR
    mov    ax, [bx]            ; save in case of unload
    mov    word ptr cs:old_int29, ax
    mov    ax, [bx+2]
    mov    word ptr cs:old_int29[2], ax
endif
    mov    word ptr [bx], offset int_29
    mov    [bx+2], cs
IF dos4
    ; Install INT 2Fh multiplex interrupt, saving old vector.
    mov    bx, 02fh * 4
    mov    ax, [bx]
    mov    word ptr cs:old_mpx, ax
    mov    ax, [bx+2]
    mov    word ptr cs:old_mpx[2], ax
    mov    word ptr [bx], offset new_mpx
    mov    word ptr [bx+2],  cs
ENDIF

    ; Install INT 10h video bios replacement, saving old vector.
    mov    bx, 10h * 4
    mov    ax, [bx]
    mov    word ptr cs:old_vid_bios, ax
    mov    ax, [bx+2]
    mov    word ptr cs:old_vid_bios[2], ax
    mov    word ptr [bx], offset new_vid_bios
    mov    word ptr [bx+2], cs

    push    cs
    pop    ds
else
    ; use INT 21 function 35 and 25 to read and set interrupt handlers.
    ; Technically this doesn't work for device driver initialization.
    ; but practice shows otherwise.

    ; Install BIOS keyboard break handler.
    push    cs
    pop    ds            ; get addressability
    assume    ds:code
if TSR
    cmp    fulldvr, 0        ; partial driver?
    je    nosetbrk
    mov    ax, 351bh        ; save old handler first
    int    21h
    mov    word ptr old_brk, bx
    mov    word ptr old_brk+2, es
endif
    mov    ax, 251bh
    mov    dx,offset break_handler
    int    21h
nosetbrk:

    ; Install INT 29 quick putchar.
if TSR
    mov    ax, 3529h        ; save old handler first
    int    21h
    mov    word ptr old_int29, bx
    mov    word ptr old_int29+2, es
endif
    mov    ax, 2529h
    mov    dx,offset int_29
    int    21h
IF dos4
    ; Install INT 2Fh multiplex interrupt, saving old vector.
    mov    ax, 352fh
    int    21h
    mov    word ptr old_mpx, bx
    mov    word ptr old_mpx+2, es
    mov    ax, 252fh
    mov    dx,offset new_mpx
    int    21h
ENDIF

    ; Install INT 10h video bios replacement, saving old vector.
    mov    ax, 3510h
    int    21h
    mov    word ptr old_vid_bios, bx
    mov    word ptr old_vid_bios+2, es
    mov    ax, 2510h
    mov    dx,offset new_vid_bios
    int    21h

endif
    push    cs
    pop    es            ; es=cs so we can use stosb

    cld                ; make sure stosb increments di

    ; Calculate addresses of start and end of parameter/redef buffer.
    ; The buffer occupies the same area of memory as this code!
    ; ANSI parameters are accumulated at the lower end, and
    ; keyboard redefinitions are stored at the upper end; the variable
    ; param_end is the last byte used by params (changes as redefs added);
    ; redef_end is the last word used by redefinitions.
    mov    di, offset dosfn0
    mov    param_buffer, di
    add    di, buf_size
    mov    param_end, di    ; addr of last byte in free area
    inc    di

    ; Announce our presence
    mov    ax,cs
    mov    bx,offset Ident1
    call hexcnv

    mov    si, offset welcome
msg_loop:
    lodsb
    cmp    al,0
    je    msg_done
    int    29h
    jmp    msg_loop

msg_done:

IF key_redef
    ; Build the default redefinition table:
    ;    control-printscreen -> control-P
    ; (Must be careful not to write over ourselves here!)
    mov    al, 16        ; control P
    stosb
    mov    ax, 7200h    ; control-printscreen
    stosw
    mov    ax, 1        ; length field
    mov    redef_end, di    ; address of last used word in table
    stosw
endif

    ; Return ending address of this device driver.
    ; Status is in AX.
    lds    si, req_ptr
    mov    word ptr [si+0Eh], di
    mov    [si+10h], cs

    xor    ax, ax
    ; Return exit status in ax.
    ret

welcome:
    db    27,'[33;1m'
    db    "NNANSI.SYS for "
    card_id
    if    cheap_pc
    db    " (XT class processor)"
    else
    db    " (AT class processor)"
    endif
    db    13, 10
    db    'By Tom Almy, version 1/93'
    db    13,10,10
    db    'Based on NANSI.SYS V2.2'
    db    13,10
    db    'Copyright 1986, Daniel Kegel.'
    db    13,10
    db    'License NANSI.SYS by sending $10.00(US) to Daniel Kegel,'
    db    13,10
    db    '535 E. Mendocino St, Altadena, CA 91001, USA.'
    db    13, 10, 13, 10
if DOSV
    db    'Modified for DOS/V by Akira Kikuchi.'
    db    13, 10, 13, 10
endif
    db    'NNANSI driver loaded at '
Ident1    db    'XXXX:0000'
    db    13, 10, 27, '[0m'
if DESQVIEW
dvset    db    0
    db    13, 10, 27, '[36mDESQVIEW DETECTED!'
    db    13, 10, 27, '[0m'
endif
    db    0
dosfn0    endp

hexcnv    proc    near
; AX= value
; BX= pointer to destination string
; AX, BX destroyed, all other registers intact.
    push    cx
    push    dx
    mov    cx, 4
hexcnv_loop:
if cheap_pc
    rol    ax, 1
    rol    ax, 1
    rol    ax, 1
    rol    ax, 1
else
    rol    ax, 4
endif
    mov    dl, al
    and    dl, 0fh
    add    dl, '0'
    cmp    dl, '9'
    jbe    hexcnv_isdigit
    add    dl, 'A'-'9'-1
hexcnv_isdigit:
    mov    [bx], dl
    inc    bx
    loop    hexcnv_loop
    pop    dx
    pop    cx
    ret

hexcnv    endp

if TSR
realstart    proc    near
; Startup code when run as a COM file rather than a device driver
    assume    cs:code, ds:nothing
    mov    ax, cs        ; correct CS  value
    add    ax, 10h
    push    ax
    mov    ax, offset cs:jumploc
    push    ax
    retf
;    db    0cbh    ; MASM doesn't define retf
jumploc:
    mov    byte ptr cs:IDLOC+10, '*' ; make us look different
    mov    bx, 81h        ; check the command line for argument
argloop:
    mov    al, ds:[bx]    ; get a character
    inc    bx
    cmp    al, 0dh        ; carriage return means "install"
    je    install
    cmp    al, 'd'        ; d or D is full installation
    je    finstall
    cmp    al, 'D'
    je    finstall
    cmp    al, 'U'        ; U or u is uninstall
    je    uninstall
    cmp    al, 'u'
    je    uninstall
    cmp    al, ' '        ; blanks ok
    je    argloop
    mov    dx, offset cs:oopsmsg    ; quit with help message
    push    cs        ; print message
    pop    ds
abortdeath:
    mov    ah, 09h
    int    21h
    mov    ax, 4c01h    ; terminate with error return code 1
    int    21h

uninstall:
; The uninstall process is somewhat different than what I've seen in
; other TSRs. It ok's an uninstall based on the TSR being directly
; below in memory the current program. Other programs check for
; the interrupt vectors being correct. Both techniques are generally
; reliable, and both can be fooled.


    push    word ptr ds:2ch    ; Environment pointer, saved in PSP
    call    findus        ; find a clone of ourself
    pop    cx        ; get back envp
    mov    ax, es
    or    ax, ax
    jnz    foundus
    mov    dx, offset cs:nocpymsg
    jmp    abortdeath
foundus:
    add    ax, word ptr es:parsize    ; get original paragraph size
    inc    ax        ; memory block header is another paragraph
    mov    bx, cs        ; and compare with this cs
    cmp    ax, bx
    jz    goodloc
                ; When unloading from a batch file using
                ; COMMAND.COM, or with 4DOS.COM if the
                ; environment has been enlarged,
                ; our environment copy will be in the way,
                ; so compensate and compare again
    add    cx, 10h        ; compensate for PSP size
    cmp    ax, cx
    jz    goodloc
    mov    dx, offset cs:badlocmsg
    jmp    abortdeath
goodloc:
    mov    al, 27        ; clear the screen
    int    29h
    mov    al, '['
    int    29h
    mov    al, '2'
    int    29h
    mov    al, 'J'
    int    29h
    mov    ax, 2529h    ; restore int29 handler
    lds    dx, es:old_int29    ; from original image's saved copy
    int    21h

if dos4
    mov    ax, 252fh    ; restore mpx handler
    lds    dx, es:old_mpx
    int    21h
endif
    mov    ax, 2510h    ; restore video bios handler
    lds    dx, es:old_vid_bios
    int    21h

    cmp    es:fulldvr, 0    ; full driver installation?
    jz    nounlink    ; no -- skip following

    mov    ax, 251bh    ; restore keyboard break handler
    lds    dx, es:old_brk
    int    21h

    push    es        ; unlink us from device driver list
    pop    ds
    assume    ds:code        ; actually code of other copy!
    mov    ah, 52h        ; get "list of lists" into es:bx
    int    21h
    mov    ax, word ptr savecon
    mov    word ptr es:0ch[bx], ax    ; direct pointer to CON driver
    mov    ax, word ptr savecon+2
    mov    word ptr es:0eh[bx], ax
    push    bx
    mov    ah, 30h        ; get DOS version
    int    21h
    pop    bx
    add    bx, 17h        ; offset of 17h to NULL in DOS 2.x
    cmp    al, 2
    je    got_nullp
    add    bx, 28h-17h    ; offset of 28h in DOS 3.0
    cmp    ax, 3
    je    got_nullp
    add    bx, 22h-28h    ; offset of 22h in DOS 3.1 and later
got_nullp:
    ; We are making the assumption that no other drivers have
    ; been linked in. This should be reasonable since I know of no
    ; other drivers that link themselves in as a TSR, and if one did
    ; it would have to have been loaded "high" after NNANSI was loaded
    ; "low", a very unlikely situation.

    mov    ax, word ptr nextdev
    mov    word ptr es:[bx], ax    ; restore pointer to next in chain
    mov    ax, word ptr nextdev+2
    mov    word ptr es:2[bx], ax
    push    ds
    pop    es

nounlink:
    mov    byte ptr es:IDLOC+10, ' '    ; unmark old image
                ; If old image is not unmarked, it can
                ; appear as a ghost, preventing nnansi
                ; from being reloaded.
    mov    ax, es        ; point at old psp
    sub    ax, 10h
    mov    es, ax
    mov    ah, 49h        ; release old memory block
    int    21h
    push    cs
    pop    ds
    mov    dx, offset cs:failedmsg
    jc    abortdeath
    mov    dx, offset cs:successmsg
    mov    ah, 9
    int    21h
    mov    ax, 4c00h    ; finished!
    int    21h

install:
    mov    cs:fulldvr, 0    ; driver is partial
finstall:
    push    word ptr ds:2ch    ; Environment pointer, saved in PSP
    push    cs        ; establish addressability
    pop    ds
    assume    ds:code
if dos4                ; use mpx vector for dos4 con driver check
    mov    ax, 1a00h
    int    2fh
    cmp    al, 0ffh    ; is an ansi driver installed?
    je    yesansidvr
endif
    mov    ax, 3529h    ; check int29 vector in either case
    int    21h
    cmp    word ptr es:10, "OC"    ; see if hooked to an ANSI driver
    jne    noansidvr
    cmp    byte ptr es:12, 'N'
    je    yesansidvr
noansidvr:
if DESQVIEW
    mov    ax, 0b800h    ; check for Desqview being present
    mov    es, ax
    xor    di, di
    mov    cx, "DE"
    mov    dx, "SQ"
    mov    ax, 2b01h
    int    21h
    cmp    al, 0ffh
    je    no_desqview    ; not loaded
    mov    dvactive, bh    ; say we are running Desqview
    mov    dvset, 13    ; change message
    mov    fmode, 0    ; disable fast mode -- would be a disaster!
    mov    ah, 0feh    ; get display page
    int    10h
    mov    disppage, es    ; es is display page to use
no_desqview:
endif
    cmp    fulldvr, 0    ; partial driver?
    je    nolink
    mov    ah, 52h        ; get "list of lists"
    int    21h
    mov    ax, word ptr es:0ch[bx]     ; save existing CON driver
    mov    word ptr savecon, ax
    mov    ax, word ptr es:0eh[bx]
    mov    word ptr savecon+2, ax
    mov    word ptr es:0ch[bx], 0    ; new con driver header
    mov    word ptr es:0eh[bx], cs
    push    bx
    mov    ah, 30h        ; get DOS version
    int    21h
    pop    bx
    add    bx, 17h        ; offset of 17h to NULL in DOS 2.x
    cmp    al, 2
    je    got_null
    add    bx, 28h-17h    ; offset of 28h in DOS 3.0
    cmp    ax, 3
    je    got_null
    add    bx, 22h-28h    ; offset of 22h in DOS 3.1 and later
got_null:
    mov    ax, word ptr es:[bx]    ; our driver points to what NULL was
    mov    word ptr nextdev, ax
    mov    ax, word ptr es:2[bx]    ; next driver
    mov    word ptr nextdev+2, ax
    mov    word ptr es:[bx], 0    ; point NULL to us
    mov    word ptr es:2[bx], cs
nolink:
    mov    word ptr req_seg, cs     ; set dummy request pointer
    mov    word ptr req_off, 020h
    call    joindosfn0    ; original initialization
    pop    es        ; get back Environment pointer
    mov    ah, 49h
    int    21h        ; and free it since we don't need it

    mov    bx, 4        ; close handles 0-4
closeloop:
    mov    ah, 3eh
    int    21h
    dec    bx
    jns    closeloop    ; loop while >= 0

    mov    dx, di    ; offset to end of resident code
    add    dx, 15+256    ; page align plus size of PSP
    shr    dx, 1    ; shift right to get # pages
    shr    dx, 1
    shr    dx, 1
    shr    dx, 1
    mov    cs:parsize, dx    ; save this size
    mov    ax, 3100h    ; Terminate and stay resident
    int    21h
abortinst:
    mov    dx, offset cs:abortmsg
    jmp    abortdeath
yesansidvr:
    mov    dx, offset cs:dvrmsg
    jmp    abortdeath
oopsmsg db "NNANSI -- no arguments mean 'install',"
    db 13,10,"          'D' means install as full driver,"
    db 13,10,"          'U' means 'uninstall'$"
abortmsg db "NNANSI -- already loaded. 'NNANSI U' to uninstall$"
dvrmsg    db "NNANSI -- another ANSI driver is already loaded$"
nocpymsg db "NNANSI -- NNANSI not loaded$"
badlocmsg db "NNANSI -- cannot unload -- not last loaded TSR$"
failedmsg db "NNANSI -- cannot unload -- memory error$"
successmsg db "NNANSI -- unloaded!$"
realstart    endp


findus    proc    near
    assume  cs:code,ds:code
    push    cs        ; make us addressable
    pop    ds
    xor    dx, dx        ; set es to 0 for search
fulup:
    mov    es, dx
    mov    cx, 6        ; compare for 12 bytes, 6 words
    mov    si, offset cs:IDLOC
    mov    di, si
    repe cmpsw
    jz    fulfound    ; found if result equal
fulnext:
    inc    dx        ; try next segment
    cmp    dx, 0fff0h    ; reached end?
    jne    fulup        ; no--try again
    xor    ax, ax        ; return 0 in es
    mov    es, ax
    ret
fulfound:            ; check for seeing ourself
    mov    ax, cs
    cmp    ax, dx
    je    fulnext        ; yep--increment and try again
    ret            ; return with segment in es
findus    endp
endif
code    ends
    end    start