Re: [boost] [serialization] text archives, strings and embedded nulls

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2006-03-17 02:59:24

Robert Ramey ha escrito:

> Hmmm - a worthy suggestion.  I suppose it would need some adjustment
> for wstring as well.  While you're at it, consider xml text which doesn't
> permit null in it at all.  Another pain to be addressed. But if one is
> concerned about NULL's, why stop there - consider all control
> characters - then one has to think about codecvt facet. etc.

Yep, I acknowledge my suggestion deals with just a tiny bit of a much bigger
problem, but at least it is a step in the right direction, IMHO.

Joaquín M López Muñoz
Telefónica, Inevstigación y Desarrollo

>
>
> Robert Ramey
>
> Joaquín Mª López Muñoz wrote:
> > Hello,
> >
> > Currently, output text archives implement string saving like this:
> >
> > template<class Archive>
> > BOOST_ARCHIVE_DECL(void)
> > text_oarchive_impl<Archive>::save(const std::string &s)
> > {
> >     const std::size_t size = s.size();
> >     *this->This() << size;
> >     this->This()->newtoken();
> >     os << s;
> > }
> >
> > which looks fine, except that some stdlib implementations don't
> > do the "os<<s" right when s contains embedded nulls --basically,
> > output stops at the first embedded null. Such a defective
> > stdlib implementation is for instance, that of MSVC 6.5, and I
> > have had conversations with Linux users leading me to
> > suspect some libstdc++ implementations as well. Besides,
> > the std requirements on operator<<(ostream,string) mandate
> > that this function does a lot more things than simply dump the
> > characters of the string, as
> > text_iarchive_impl<Archive>::load(std::string &)
> > assumes implicitly (reading is done through istream::read.)
> >
> > The attached example shows the problem. It crashes in MSVC 6.5,
> > my hunch is that it'll fail in some other environments as well, though
> > not in every one. Using intermediate buffers of type vector<char>
> > fixes the problem.
> >
> > My suggestion is that text_oarchive_impl<Archive>::save(const
> > std::string &s)
> > be changed so as to dump the string as follows:
> >
> > template<class Archive>
> > BOOST_ARCHIVE_DECL(void)
> > text_oarchive_impl<Archive>::save(const std::string &s)
> > {
> >     const std::size_t size = s.size();
> >     *this->This() << size;
> >     this->This()->newtoken();
> >     os.write(s.data(),s.size());
> > }
> >
> > so as to avoid problems with embedded nulls.
> >
> > Joaquín M López Muñoz
> > Telefónica, Investigación y Desarrollo
> >
> >
> >
> >
> >
> >
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