text: #ifndef BOOST_ARCHIVE_ITERATORS_BINARY_FROM_BASE64_HPP
  #define BOOST_ARCHIVE_ITERATORS_BINARY_FROM_BASE64_HPP
  
  // MS compatible compilers support #pragma once
  #if defined(_MSC_VER)
  # pragma once
  #endif
  
  /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
  // binary_from_base64.hpp
  
  // (C) Copyright 2002 Robert Ramey - http://www.rrsd.com . 
  // Use, modification and distribution is subject to the Boost Software
  // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt)
  
  //  See http://www.boost.org for updates, documentation, and revision history.
  
  #include <boost/assert.hpp>
  
  #include <boost/config.hpp> // for BOOST_DEDUCED_TYPENAME
  #include <boost/serialization/throw_exception.hpp>
  #include <boost/serialization/pfto.hpp>
  #include <boost/static_assert.hpp>
  
  #include <boost/iterator/transform_iterator.hpp>
  #include <boost/archive/iterators/dataflow_exception.hpp>
  
  namespace boost { 
  namespace archive {
  namespace iterators {
  
  /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
  // convert base64 characters to binary data
  
  namespace detail {
  
  template<class CharType>
  struct to_6_bit {
      typedef CharType result_type;
      CharType operator()(CharType t) const{
          const signed char lookup_table[] = {
              -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
              -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
              -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,
              52,53,54,55,56,57,58,59,60,61,-1,-1,-1, 0,-1,-1, // render '=' as 0
              -1, 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,-1,-1,-1,-1,-1,
              -1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
              41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1
          };
          // metrowerks trips this assertion - how come?
          #if ! defined(__MWERKS__)
          BOOST_STATIC_ASSERT(128 == sizeof(lookup_table));
          #endif
          signed char value = -1;
          if((unsigned)t <= 127)
              value = lookup_table[(unsigned)t];
          if(-1 == value)
              boost::serialization::throw_exception(
                  dataflow_exception(dataflow_exception::invalid_base64_character)
              );
          return value;
      }
  };
  
  } // namespace detail
  
  // note: what we would like to do is
  // template<class Base, class CharType = BOOST_DEDUCED_TYPENAME Base::value_type>
  //  typedef transform_iterator<
  //      from_6_bit<CharType>,
  //      transform_width<Base, 6, sizeof(Base::value_type) * 8, CharType>
  //  > base64_from_binary;
  // but C++ won't accept this.  Rather than using a "type generator" and
  // using a different syntax, make a derivation which should be equivalent.
  //
  // Another issue addressed here is that the transform_iterator doesn't have
  // a templated constructor.  This makes it incompatible with the dataflow
  // ideal.  This is also addressed here.
  
  template<
      class Base, 
      class CharType = BOOST_DEDUCED_TYPENAME boost::iterator_value<Base>::type
  >
  class binary_from_base64 : public
      transform_iterator<
          detail::to_6_bit<CharType>,
          Base
      >
  {
      friend class boost::iterator_core_access;
      typedef transform_iterator<
          detail::to_6_bit<CharType>,
          Base
      > super_t;
  public:
      // make composible buy using templated constructor
      template<class T>
      binary_from_base64(BOOST_PFTO_WRAPPER(T)  start) :
          super_t(
              Base(BOOST_MAKE_PFTO_WRAPPER(static_cast< T >(start))), 
              detail::to_6_bit<CharType>()
          )
      {}
      // intel 7.1 doesn't like default copy constructor
      binary_from_base64(const binary_from_base64 & rhs) : 
          super_t(
              Base(rhs.base_reference()),
              detail::to_6_bit<CharType>()
          )
      {}
  //    binary_from_base64(){};
  };
  
  } // namespace iterators
  } // namespace archive
  } // namespace boost
  
  #endif // BOOST_ARCHIVE_ITERATORS_BINARY_FROM_BASE64_HPP
  