Re: gzipped data files

[David Bateman]

John W. Eaton wrote:

> On 29-Apr-2005, David Bateman wrote:
>
> | Dmitri A. Sergatskov wrote:
> | 
> | > Since we now have all this gzip machinery in place,
> | > would it be easy to add gzip option to fopen()?
> | > That is, I would like to be able to do something like:
> | >
> | > fid = fopen("data.dat.gz","rz")   
> | >
> | > a = fscanf(fid,"%f")
> | >
> | > ...
> | >
> | > Just asking...
> | >
> | > Dmitri.
> | 
> | Something like that is relatively easy, as gzopen just a C file 
> | descriptor.
>
> ?  Does it really work to pass a gzFile object to any of the stdio
> functions that expect a FILE pointer?
>
> Anyway, try the following patch.
>
>  
It works in the opposite sense... A gzFile can act like a normal file 
descriptor if gzOpen was called with a non gzipped file..

I notice that in your patch all of the seek code is disabled... The 
seeking in a read-only file should work find, in a write-only file 
seeking in a forward direction should work, and you can't have a gzipped 
file open for both reading and writing at the same time.. These are 
limitations of zlib and normal ones and the implication of implying 
these features means that a buffer containing all of the data written to 
the file would be needed so that the gzipped file could be searched 
backwards, etc...

Cheers
David