irpSp->Parameters.Read(Write).ByteOffset.QuadPart vs. FileObject->CurrentByteOffset.QuadPart

NTFSD
1

But see also uses of (from ntifs.h)
#define FILE_WRITE_TO_END_OF_FILE 0xffffffff
in the fastfat source. I imagine this may only be a Posix subsystem sort of
thing…?

There is also (in ntifs.h)
#define FILE_USE_FILE_POINTER_POSITION 0xfffffffe
but since fastfat never uses this symbol, it must be for input to
NtReadFile/NtWriteFile and the i/o manager must translate it for you…?

…Jay

-----Original Message-----

Subject: NT File system driver
From: dubi@il.ibm.com
Date: Sun, 21 Jan 2001 21:04:47 +0200
X-Message-Number: 2

Hi there,
A question concerning NT file system driver :

As it is not totally clear to me from the IFS :

For Read or Write , synchronous or Non synchronous IO cases , what sould be
used as the offset (start point) for reading from the file :
FileObject->CurrentByteOffset.QuadPart or
irpSp->Parameters.Read(Write).ByteOffset.QuadPart (which one to use in
every case )

thanks,
Zvi

Subject: RE: NT File system driver
From: =?US-ASCII?Q?Abel_Munoz_Alcaraz?=
>Date: Sun, 21 Jan 2001 23:32:02 +0100
>X-Message-Number: 3
>
>Hi Zvi,
>
>You must use irpSp->Parameters.Read(Write).ByteOffset.QuadPart in both
>cases.
>
>-Abel.

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2

> There is also (in ntifs.h)

#define FILE_USE_FILE_POINTER_POSITION 0xfffffffe
but since fastfat never uses this symbol, it must be for input to
NtReadFile/NtWriteFile and the i/o manager must translate it for you…?

Generally, this is distinguished by whether the OVERLAPPED structure was
specified to ReadFile or not. If it was specified - than the IO manager
ignores the current byte offset and uses the offset from the OVERLAPPED
structure - it is one of the parameters to ZwReadFile.

Max

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