Re: [Boost-users] boost::lexical_cast<> with hex strings?

Subject: Re: [Boost-users] boost::lexical_cast<> with hex strings?
From: boost_at_[hidden]
Date: 2010-07-15 16:11:43

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of anony
Sent: Thursday, July 15, 2010 1:09 AM
To: boost-users_at_[hidden]
Subject: [Boost-users] boost::lexical_cast<> with hex strings?

I'd like to do something like:

boost::uint16_t b(std::lexical_cast<boost::uint16_t>("xa"));

I have no control of the string stream that lexical_cast uses
internally, so how could I implement this?

P.S.: There are a lot of false statements made about this functionality
on the web, some people claim that boost::lexical_cast<> can do the
conversion out of the box, but this is not so in my tests. 

What about doing this

struct hexint
{
   operator unsigned int()
   {
      return value;
   }
   unsigned int value;
};

inline std::istream &operator>>(std::istream &in, hexint &rhs)
{
   std::ios::fmtflags flags=in.flags();

   in.unsetf(std::ios::oct);
   in.unsetf(std::ios::dec);
   in.unsetf(std::ios::hex);
   unsigned int temp=0;
   in >> temp;
   in.setf(flags);
   if(in.bad())
   {
      throw boost::bad_lexical_cast();
   }
   rhs.value=temp;

   return in;
}

//Then you can do
hexint x=boost::lexical_cast<hexint>("0x2a");