[pclasses-devel] adding zlib/bzip streams support

[stephan b. <st...@s1...>]

Hi, Christian!

i'm looking over the IOD/IOS code, and i would like to port in 2 LGPL 
classes a couple other guys wrote (don't remember their names) which 
provide transparent gzip/bzip2 support.  Would you mind if i add an 
optional dependency on zlib/bzip2 to port these classes in?

i'm not yet certain how to fit them best into the architecture. They are 
implemented as i/stream[buffer] implementations and only support files 
(not, zB, stringstream). There is no FileStream class any longer - only 
a File device which gets passed to an IOStream. That means i can't 
extend/modify FileStream. Perhaps a (FileStream : public IOStream) 
convenience type would be a solution? We could then add member funcs to 
it like:

setCompressionPolicy( None|Gzip|Bzip );
CompressionPolicy getCompressionPolicy() const;

For reading files we can auto-determine the decompression technique 
based on the first few bytes (i don't yet know how to dispatch this 
type of logic via a factory, though).

The problem with this approach is that FileStream would need to proxy 
all IOS-related API calls to the appropriate de/compressor stream. 
That's possible to implement, i guess, but tedious.

So, i guess my question is: if you were going to add GZip file support, 
where would you put it?

PS: i think the IOS/IOD architecture will easily support the addition of 
Zip archive support, since we can treat a zip as a virtual filesystem. 
With s11n support on top of that we've got some really flexible object 
persistency options. :)


-- 
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