🚀 go-pugleaf

Ivan Van den Bossche wrote:
> Hi,
>
> Ik gebruik in de programmeertaal C de Windows functie CreateFile om
> een file te openen en op een bepaald punt moet ik de huidige positie
> opvragen in bytes ten opzichte van het begin van deze file (offset).
> Weet er iemand hoe ik die positie in bytes kan opvragen?
>
> Alvast bedankt.
> Ivan

Met SetFilePointer kun je zowel de file pointer zetten als uitlezen:


*Retrieving a File Pointer*

The SetFilePointer function can be used to query the current file pointer
position, by specifying a move method of FILE_CURRENT and a distance of
zero.

HANDLE hFile;

DWORD dwCurrentFilePosition;

dwCurrentFilePosition = SetFilePointer(
    hFile, // must have GENERIC_READ and/or GENERIC_WRITE
    0,     // do not move pointer
    NULL,  // hFile is not large enough to need this pointer
    FILE_CURRENT);  // provides offset from current position

The following macro can be used to obtain the current file pointer position
for files smaller than 2 gigabytes in size:

#define GetFilePointer(hFile) SetFilePointer(hFile, 0, NULL, FILE_CURRENT)

To get the current file positions on larger files, use the following:

#define GetVLFilePointer(hFile, lpPositionHigh) \
        (*lpPositionHigh = 0, \
        SetFilePointer(hFile, 0, lpPositionHigh, FILE_CURRENT))

where lpPositionHigh is a value of type PLONG. The high order long word of
the current file position will be returned in lpPositionHigh.




--
www.zenobits.com

"Ivan Van den Bossche" <ivan.van.den.bossche@pandora.be> wrote in message
news:TSraa.2409$Vq.380@afrodite.telenet-ops.be...
> Weet er iemand hoe
> ik die positie in bytes kan opvragen?

Je kan dat doen via SetFilePointer(). Wat je doet is die methode aanroepen
met dwMoveMethod = FILE_CURRENT, lDistanceToMove = 0 en lpDistanceToMoveHigh
= 0 [je kan hier ook NULL specifieren, maar dan kan je nooit de positie
opvragen van files > 4.2Gb].
Nadat je die methode hebt aangeroepen geeft die je de huidige positie terug:
"If the SetFilePointer function succeeds and lpDistanceToMoveHigh is NULL,
the return value is the low-order DWORD of the new file pointer. If
lpDistanceToMoveHigh is not NULL, the function returns the low order DWORD
of the new file pointer, and puts the high-order DWORD of the new file
pointer into the LONG pointed to by that parameter."

Mvg,
Pieter Philippaerts