#include <locale>
#include <iostream>

class rot13codecvt : public std::codecvt<char, char, std::mbstate_t>
{
protected:
  virtual ~rot13codecvt() { }

  virtual result do_out(std::mbstate_t& /* state */,
                        const char* from,
                        const char* from_end,
                        const char*& from_next,
                        char* to,
                        char* to_limit,
                        char*& to_next) const 
      { return rot13(from, from_end, from_next, to, to_limit, to_next); }

  virtual result do_in(std::mbstate_t& /* state */,
                       const char* from,
                       const char* from_end,
                       const char*& from_next,
                       char* to,
                       char* to_limit,
                       char*& to_next) const
      { return rot13(from, from_end, from_next, to, to_limit, to_next); }

  virtual result do_unshift(std::mbstate_t& state,
                       char* to,
                       char* to_limit,
                       char*& to_next) const;

  virtual int do_encoding() const throw() { return 1; }

  virtual bool do_always_noconv() const throw() { return false; }

  virtual int do_length(const std::mbstate_t&,
                        const char* from,
                        const char* end,
                        size_t max) const;

  virtual int do_max_length() const throw() { return 1; }

private:
  result rot13(const char* from,
               const char* from_end,
               const char*& from_next,
               char* to,
               char* to_limit,
               char*& to_next) const;
}; // class rot13codecvt

static const unsigned char table[]={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,78,79,80,81,82,83,84,85,86,87,88,89,90,65,66,67,68,69,70,71,72,73,74,75,76,77,91,92,93,94,95,96,110,111,112,113,114,115,116,117,118,119,120,121,122,97,98,99,100,101,102,103,104,105,106,107,108,109,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255};

std::codecvt_base::result rot13codecvt::rot13(const char* from,
               const char* from_end,
               const char*& from_next,
               char* to,
               char* to_limit,
               char*& to_next) const
{
  from_next = from;
  to_next = to;

  while((to_next != to_limit) && (from_next != from_end) )
    *to_next++ = table[static_cast<unsigned char>(*from_next++)];

  return (from_next == from_end) ? std::codecvt_base::ok : std::codecvt_base::partial; 
} // rot13

std::codecvt_base::result rot13codecvt::do_unshift(std::mbstate_t& /* state */,
                            char* to,
                            char* /* to_limit */,
                            char*& to_next) const
{
  to_next = to;
  return std::codecvt_base::ok;
} // do_unshift

int rot13codecvt::do_length(const std::mbstate_t&,
                        const char* from,
                        const char* end,
                        size_t max) const
{
  return std::max<int>(end - from, max);
} // do_length


int main ()
{
  std::cout.imbue(std::locale(std::locale("C"), new rot13codecvt()));
  std::cout << "The quick brown fox ran over the lazy dog" << std::endl;
}