[Qt-interest] Reading/Writing archives

[Stephen Bryant]

Hi,

> >From what I read, zlib works only for single-file archives.
> 
> With gzip or zip libraries, I may have missed something, but it seemed
> to me that it cannot navigate in the archive file without uncompressing
> it on the disk first.

While 'gzip' and 'zip' have very similar names and use the same zlib 
compression routines, the file formats are not at all similar.

A gzip file is not an archive - it is a single compressed file.  The 
compressed data may contain an archive, but you will have to decompress it 
first to get at it.

A zip file, conversely, is an archive with an index at the end.  You do not 
need to decompress it to read the index.  The index also contains the offsets 
is individual compressed files inside the archive, allowing them to be 
accessed directly.

I would think that ZIP should suit you just fine.  Make sure your 
implementation also support the ZIP64 extensions, otherwise you are likely to 
run into the 4GB file size limit.

Steve
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