Simtel MSDOS - Coast to Coast/simteldosarchivecoasttocoast2.iso/ka9q/nan24hyc.zip/NANSI_P.ASM

Assembly Source File | 1990-10-31 | 10KB | 307 lines

    page    66, 132
;----- nansi_p.asm --------------------------------------------------------
; A state machine implementation of the mechanics of ANSI terminal control
; string parsing.
; (C) 1986 Daniel Kegel, Pasadena, CA
; May be distributed for educational and personal use only
;
; 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.
;
; Revision history:
; 7 July 85: created by DRK
;------------------------------------------------------------------------

    ; From nansi.asm
    extrn    f_not_ANSI:near        ; exit: abort bad ANSI cmd
    extrn    f_ANSI_exit:near    ; exit: good cmd done
    extrn    f_loopdone:near        ; exit: ran out of chars. State saved.
    extrn    escvector:word        ; saved state: where to jump
    extrn    cur_parm_ptr:word    ; saved state: where to put next param
    extrn    string_term:byte    ; saved state: what ends string
    extrn    cur_x:byte, max_x:byte    ; 0 <= cur_x <= max_x
    extrn    cur_attrib:byte        ; current color/attribute
    extrn    xlate_tab_ptr:word

    ; from nansi_f.asm
    extrn    ansi_fn_table:word    ; ANSI subroutine table

    ; Used in nansi.asm
    public    f_escape        ; entry: found an escape
    public    f_in_escape        ; entry: restore state, keep parsing

    ; Used in nansi_i.asm and nansi_f.asm
    public    param_buffer, param_end, redef_end


code    segment byte public 'CODE'
    assume    cs:code

; More saved state
in_num        db    ?    ; true if between a digit and a semi in parse

param_buffer    dw    3000h    ; address of first byte free for new params
param_end    dw    3030h    ; address of end of free area
redef_end    dw    3030h    ; address of end of redefinition area
        ; These initialized values are only for debugging

;----- 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

;----- 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_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

;----- 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
    mov    byte ptr cs:[bx], 0
    mov    cs:in_num, 0
    next_is f_get_args

;----- f_get_args ---------------------------------------------------
; Last char was a [.  If the current char is a '=' or a '?', eat it.
; In any case, proceed to f_get_param.
; This is only here to strip off the strange chars that follow [ in
; the SET/RESET MODE escape sequence.
f_get_args:
    lodsb
    cmp    al, '='
    jz    fga_ignore
    cmp    al, '?'
    jz    fga_ignore
        dec    si        ; let f_get_param fetch al again
        jmp    short f_get_param
fga_ignore:
    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
    cmp    al, '0'
    jb    fgp_may_quote
    cmp    al, '9'
    ja    fgp_may_quote
        ; It's the first digit.     Initialize current parameter with it.
        sub    al, '0'
        mov    byte ptr cs:[bx], al
        mov    cs:in_num, 1    ; set flag for sensing at cmd exec
        next_is f_in_param
fgp_may_quote:
    cmp    al, '"'
    jz    fgp_isquote
    cmp    al, "'"
    jnz    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

;----- 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
    jz    fgs_init_next_param
    mov    byte ptr cs:[bx], al
    cmp    bx, cs:param_end
    adc    bx, 0            ; if bx<param_end bx++;
    next_is f_get_string
; Ending quote was found.
fgs_init_next_param:
    mov    byte ptr cs:[bx], 0    ; initialize new parameter
    ; | Eat following semicolon, if any.
    next_is f_eat_semi

;----- f_eat_semi -------------------------------------
; Last character was an ending quote.
; If this char is a semi, eat it; else unget it.
; Next state is always f_get_param.
f_eat_semi:
    lodsb
    cmp    al, ';'
    jz    fes_eaten
        inc    cx
        dec    si
fes_eaten:
    next_is f_get_param

;----- 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
    mov    bx, cs:xlate_tab_ptr
    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_semi_or_cmd
    cmp    al, '9'
    ja    fgp_semi_or_cmd
        ; 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
    ; Code common to states get_param and in_param.
    ; Accepts a semicolon or a command letter.
fgp_semi_or_cmd:
    cmp    al, ';'
    jnz    fgp_not_semi
        cmp    bx, cs:param_end    ; prepare for next param-
        adc    bx, 0            ; if bp<param_end bp++;
        ; Set new param to zero, enter state f_get_param.
        mov    cs:in_num, 0        ; no longer inside number
        jmp    fgs_init_next_param    ; spaghetti code attack!
fgp_not_semi:
    ; 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

    sub    al, '@'            ; first command is @: insert chars
    cbw
    add    ax, ax
    add    ax, offset ansi_fn_table
    ; ax is now pointer to command routine address in table

    mov    cx, bx
    mov    si, param_buffer    ; si is now pointer to parameters
    sub    cx, si            ;
    test    in_num, 1
    jz    fip_out_num
        inc    cx
fip_out_num:                ; 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.
    mov    ah, 0
    lodsb
    or    al, al
    jnz    fgp_callem
        inc    ax
        or    ah, ah    ; save Zflag for eid  -- hyc 10-30-90
fgp_callem:
    ; Finally, call the command subroutine.
    call    word ptr [bx]

    pop    ds
    pop    cx
    pop    si

    mov    ah, cs:cur_attrib    ; Prepare for STOSW.
    mov    bx, cs:xlate_tab_ptr    ; Prepare for translation.
    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


code    ends
    end                ; of nansi_p.asm