file pointer reset of CArchive

[leejwen]

Hello, I used below MFC code to read a file, but I need do that several times, how can I move the pointer to the beginning of file once again. Thank you!

CFile f;
CArchive ar(&f, CArchive::load) ;
...
while(ar.ReadSt ring(ptr))
{
...
}

//here should reset to the beginning of file

//re-read the file again
while(ar.ReadSt ring(ptr))
{
...
}

[arnaudk]

See CFile reference, in particular take a look at the various functions affecting the position within the file.

[leejwen]

See CFile reference, in particular take a look at the various functions affecting the position within the file.

Thank you! That's helpful

[leejwen]

Thank you! That's helpful

But why second "while" doesnt work? see below. (It seems the pointer is still at the end of file)

CFile f;
CArchive ar(&f, CArchive::load) ;
...
while(ar.ReadSt ring(ptr))
{
//work well
}

ar.Flush();
ar.GetFile()->SeekToBegin( );
ar.Flush();
while(ar.ReadSt ring(ptr))
{
//
}

[arnaudk]

The thing is you're reading from a CArchive, not the file directly. Try to close and reopen the CArchive it before the second loop. Check the CArchive reference.

[leejwen]

play a small trick to finish that,

CFile f;
{
CArchive ar(&f, CArchive::load) ;
while(ar.ReadSt ring())
{
//
}
}
f.SeekToBegin() ;
{
CArchive ar(&f, CArchive::load) ;
while(ar.ReadSt ring())
{
//
}
}

Thank you!