[Boost-users] [iostreams][serialization] compressed UTF-8 XML archive

Subject: [Boost-users] [iostreams][serialization] compressed UTF-8 XML archive
From: Paul (elegant_dice_at_[hidden])
Date: 2010-03-16 23:29:55

(Was: Re: [Boost-users] Filesystem, serialization, character encoding and
portable software)

On 14 August 2008 00:44, Robert Ramey <ramey_at_[hidden]> wrote:

> Daniel Krügler wrote:
> > Robert Ramey wrote:
> >> the wide character xml archives use UTF8.
> >>
> >> the narrow character xml archives use the currently set locale.
> >>
> >> Robert Ramey
> >
> > Sorry for asking offhand:
> >
> > What is the reasoning behind this different behaviour?
>
> I assumed that most programs built with narrow characters used
> the locale concept to deal with this.
>
> Wide character systems lend themselves to UTF coding so I
> used that for wide char archives.  In order to do this, I used
> Ron Garcia's UTF code conversion facet for streams.
>
> It would be quite easy to generate UTF coding for narrow
> character archives.  Just do the following:
>
> a) Build the UTF code conversion facet for narrow character
> input (its templated on character type).
>
> b) When the stream is opened, attach this facet to the stream.
>
> Note the the output char format is not really a property of the
> serialization
> library, but rather an artifact of the way it has been used.  That is, the
> serialization library depends on the standard stream library for this
> property.
>
>
I understand that to get a UTF-8 XML file, I need to use a wide-character
stream, but I can't seem to understand how I can compress a serialized UTF-8
xml archive...  it seems I can either do:

namespace bio = boost::iostreams;
namespace fs = boost::filesystem;

fs::wofstream ofs(path,ios::binary);
bio::filtering_stream<bio::output,wchar_t> out;
out.push(bio::gzip_compressor());   // PROBLEM: gzip_compressor only accepts
char
out.push(ofs);
boost::archive::xml_woarchive oa(out);

--- OR ---

fs::ofstream ofs(path,ios::binary);
bio::filtering_stream<bio::output> out;
out.push(bio::gzip_compressor());
out.push(ofs);
boost::archive::xml_woarchive oa(out);  // PROBLEM: only accepts wostream

I've googled but haven't found anything relevant... either people use an
ifstream with gzip_compressor, or they don't use gzip_compressor at all.

thanks,
Paul