Re: [pclasses-devel] sublayer idea: dynamic stream dispatching

[Christian P. <cp...@se...>]

The std::iostreams stuff in pclasses definetly needs a rework.
I like your idea with "output filters". Maybe we can do a complete io stream 
rework together.

Regards,

Christian

Am Samstag 18 Dezember 2004 01:01 schrieb stephan beal:
> Yo again!
>
> i've got a little lib, called zfstream, which adds client-transparent
> support for loading compressed files. For some months i've been
> thinking about making a more generic variant of it which can be
> extended by registering handlers. Looking at your I/O layer, believe
> that code would be a great basis for it.
>
> To give some background/context... consider this code:
>
> std::istream * is = zfstream::get_istream( "some_file" );
> if( ! is ) { file not found or could not be opened }
>
> The input stream might actually be a compressed file, and the stream
> might be of type gzstream or bzstream (for gzip or bzip2,
> respectively). get_istream() examines the file to determine which type
> of decompressor to use, and passes back the appropriate stream type.
>
> The same goes for output files:
>
> Set the framework-wide policy:
>
> zfstream::compression_policy( zfstream::GZipCompression )
>
> Now all calls like these use the requested compression:
>
> std::ostream * os = zfstream::get_ostream( "some_file" );
>
> The ostream is compressed if the lib supports it (if configure script
> finds zlib) and if compression_policy() specifies it. If not, you get
> back an uncompressed stream.
>
> The point is, client code doesn't know if it's using compressed streams
> or not, and doesn't have to know.
>
> By making that more generic and adding handlers for your I/O classes, we
> could do:
>
> SomeIORequestBase * os =
>     get_ostream( "http://s11n.net/s11n/sample.s11n.gz" );
>
> and that might return a gzip-decompressing stream type.
>
> i've tried a couple times to implement custom std::streambuffer classes
> and i've failed miserably. Anyone out there who thinks that it isn't
> too much work to write std-stream wrappers for the P::IO layer?
>
> Take care,