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List:       koffice-devel
Subject:    Re: KTarGz and streams
From:       David Faure <david () mandrakesoft ! com>
Date:       2001-07-29 23:23:42
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On Monday 30 July 2001 00:52, David Faure wrote:
> Done. The one thing this brings forward is that we need to know the
> size of the data before hand, it's needed in the TAR header. Well, otherwise
> we have to implement "going back in the stream and writing the size", a bit
> of a problem with a compressed stream...

It's actually more than problematic, it appears to be impossible....

ZEXTERN z_off_t ZEXPORT    gzseek OF((gzFile file,
                                      z_off_t offset, int whence));
/*
[....]
   If the file is opened for reading, this function is emulated but can be
   extremely slow. If the file is opened for writing, only forward seeks are
   supported; gzseek then compresses a sequence of zeroes up to the new
   starting position.
*/

What we want here is a backward seek when writing :(
I'm afraid we have to buffer the data when we don't know its size.
At least with this new change we can write big known files by
small chunks.

-- 
David FAURE, david@mandrakesoft.com, faure@kde.org
http://perso.mandrakesoft.com/~david/, http://www.konqueror.org/
KDE, Making The Future of Computing Available Today
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