Re: fcb's

 BBS: Inland Empire Archive
Date: 12-27-92 (12:27)             Number: 384
From: DIK COATES                   Refer#: NONE
  To: CHRIS HOLTEN                  Recvd: NO  
Subj: Re: fcb's                      Conf: (2) Quik_Bas
>>>> QUOTING Chris Holten to Francois Roy <<<<

 CH> In a message of <18 Dec 92  13:56:32>, Francois Roy (1:163/506.2)
 >FR : SP> This is probably a dumb question, but here it goes. I need to
 >FR :get the
 >FR : SP> size of a file.

 CH> Gotta do something more exotic so's yer basic code will
 CH> look more like some highly structured language with some
 CH> Ax's, Dx's, Ah's and such whatnot's in it <chuckle>. Gotta
 CH> keep that spaghettie level down you see.

Was feeling kinda silly, so came up with the following... and added it
to my library... Feel free to use it in your programs...

; Copyright (C) 1992 by R.A. Coates, All Rights Reserved
; DECLARE FUNCTION FLENGTH& (filename$, errval%)

.Model Medium, Basic

Extrn StringAddress:Proc    ;part of PDS


oldint      dw  ?
buff80      db    80 dup(?)     ;80 byte buffer to hold string values

; Returns the length of a file as a Long Integer, if the function
; is successful, otherwise, it returns a zero value.  The DOS
; Critical Error Value is returned as errval%, if the Function
; fails.  The procedure works by opening a file, setting an offset
; from the end of the file, and reading back the new file pointer
; location.  The file is then closed.
; The function declaration is as follows:
;   DECLARE FUNCTION FLENGTH& (filename$, errval%)
; The Arguments are:
;   filename$ - name of file to determine length of
;   errval%   - DOS Critical Error Value
; REV:  92-12-26

FLENGTH     proc  uses bx cx ds es si di, dsrptr:word, errval:word

            mov   ax, 3524h       ;DOS get int 24h vector
            int   21h
            mov   ax, es:[bx]
            mov   cs:oldint, ax   ;save old vector to oldint
            mov   word ptr es:[bx], 00CFh   ;replace it with IRET call

            mov   ax, dsrptr
            push  ax              ;load ax on stack for call to StringAddress
            call  StringAddress
            mov   ds, dx          ;set up the source in ds:si
            mov   si, ax
            push  cs
            pop   es              ;set up the destination in es:di
            lea   ax, buff80
            mov   di, ax
            shr   cx, 1           ;divide by 2 to move words
       rep  movsw                 ;until cx is 0
            jnc   FLen1           ;if odd num of bytes in
string, carry flag set
            movsb                 ;move last byte if odd number
FLen1:      mov   es:[di], cl     ;add terminating NUL es:ax points to buff80
            mov   dx, ax
            push  es
            pop   ds              ;ds:dx pointer to buff80

            mov   ax, 3D00h       ;DOS open file
            int   21h
            jc    FLenError       ;if cf clear, handle in ax

            mov   bx, ax          ;put handle in bx
            mov   ax, 4202h
            xor   dx, dx          ;dx(lsb), cx(msb) offset set to 0
            int   21h             ;Function 42h, ax = 02-from eof
            jc    FLenError       ;if cf clear, dx(msb),
ax(lsb) length of file

            mov   cx, ax          ;save ax in cx
            mov   ax, 3E00h       ;handle still in bx
            int   21h             ;Function 3Eh, close file
            jc    FLenError
            jmp   FLenExit        ;exit with file length in dx, ax

FLenError:  mov   bx, errval      ;carry flag not clear, ret crit err
            mov   ss:[bx], ax     ;ss and DGROUP are one and the same

            xor   cx, cx          ;make cx=0 and swap with ax on exit
            xor   dx, dx          ;return 0 as Function value

FLenExit:   mov   ax, 3524h       ;DOS get int 24h vector
            int   21h
            mov   ax, cs:oldint
            mov   es:[bx], ax     ;restore old value
            mov   ax, cx          ;restore ax

FLENGTH     Endp


It even handles accessing a file on drive a: when the gate's left
open... had to write an interrupt handler to cover that... goes
great with pasta...

Regards Dik, Oshawa, Canada

... Bad command or filename.  Go stand in the corner.
___ Blue Wave/QWK v2.10

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