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OTABNEXT.ASM
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Assembly Source File
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1989-05-02
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2KB
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80 lines
; FILENAME: OTABNEXT.ASM
; Copyright (c) 1988, 1989 by Borland International, Inc.
;
; Description: This module implements the routine TabNext. TabNext
; returns the number of spaces to the next tab stop.
; This module uses MASM mode syntax and standard segment directives.
;
; ASSEMBLY INSTRUCTIONS: To assemble this module use the following
; TASM command line.
;
; TASM otabnext
include globals.inc
_TEXT segment
TabNext proc
; This function returns the number of spaces to the next tab stop.
; The value passed in cx represents the present column number.
; A tab is represented by the number 1 in the tab table.
; Input
; cx - the present column number
; TabTbl - starting location of the tab table
; TabEnd - ending location of the tab table
; Output
; dx - number of spaces to the next tab stop
; cf - set if initially started at a tab stop
; Registers modified
; dx
push bx
push si
mov bx, cx ;tab column
add bx, TabOff ;add special offset
lea bx, [TabTbl + bx] ;get starting address
sub dx, dx
cmp bx, TabEnd ;check if at or past end
jae tabnex4 ;jump if so
mov si, bx ;save starting location
inc bx ;start at next column
inc dx ;set count
;--- loop until tab stop is found or end of table
tabnex1:
cmp bx, TabEnd ;check if end
jae tabnex2
cmp BYTE PTR [bx], 0 ;check if tab
jne tabnex2
inc bx ;next column
inc dx ;increment count
jmp tabnex1 ;loop back
;--- found tab stop
tabnex2:
cmp BYTE PTR [si], 0 ;check if started at tab stop
jne tabnex3
pop si
pop bx
clc
ret
;--- initial tab stop
tabnex3:
stc
tabnex4:
pop si
pop bx
ret
TabNext endp
_TEXT ends
end