boost/date_time/int_adapter.hpp

#ifndef _DATE_TIME_INT_ADAPTER_HPP__
#define _DATE_TIME_INT_ADAPTER_HPP__

/* Copyright (c) 2002,2003 CrystalClear Software, Inc.
 * Use, modification and distribution is subject to the
 * Boost Software License, Version 1.0. (See accompanying
 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
 * Author: Jeff Garland, Bart Garst
 * $Date$
 */


#include "boost/config.hpp"
#include "boost/limits.hpp" //work around compilers without limits
#include "boost/date_time/special_defs.hpp"
#include "boost/date_time/locale_config.hpp"
#ifndef BOOST_DATE_TIME_NO_LOCALE
#  include <ostream>
#endif

#if defined(BOOST_MSVC)
#pragma warning(push)
// conditional expression is constant
#pragma warning(disable: 4127)
#endif

namespace boost {
namespace date_time {


//! Adapter to create integer types with +-infinity, and not a value
/*! This class is used internally in counted date/time representations.
 *  It adds the floating point like features of infinities and
 *  not a number. It also provides mathmatical operations with
 *  consideration to special values following these rules:
 *@code
 *  +infinity  -  infinity  == Not A Number (NAN)
 *   infinity  *  non-zero  == infinity
 *   infinity  *  zero      == NAN
 *  +infinity  * -integer   == -infinity
 *   infinity  /  infinity  == NAN
 *   infinity  *  infinity  == infinity
 *@endcode
 */
template<typename int_type_>
class int_adapter {
public:
  typedef int_type_ int_type;
  int_adapter(int_type v) :
    value_(v)
  {}
  static bool has_infinity()
  {
    return  true;
  }
  static const int_adapter  pos_infinity()
  {
    return (::std::numeric_limits<int_type>::max)();
  }
  static const int_adapter  neg_infinity()
  {
    return (::std::numeric_limits<int_type>::min)();
  }
  static const int_adapter  not_a_number()
  {
    return (::std::numeric_limits<int_type>::max)()-1;
  }
  static  int_adapter max BOOST_PREVENT_MACRO_SUBSTITUTION ()
  {
    return (::std::numeric_limits<int_type>::max)()-2;
  }
  static  int_adapter min BOOST_PREVENT_MACRO_SUBSTITUTION ()
  {
    return (::std::numeric_limits<int_type>::min)()+1;
  }
  static int_adapter from_special(special_values sv)
  {
    switch (sv) {
    case not_a_date_time: return not_a_number();
    case neg_infin:       return neg_infinity();
    case pos_infin:       return pos_infinity();
    case max_date_time:   return (max)();
    case min_date_time:   return (min)();
    default:              return not_a_number();
    }
  }
  static bool is_inf(int_type v)
  {
    return (v == neg_infinity().as_number() ||
            v == pos_infinity().as_number());
  }
  static bool is_neg_inf(int_type v)
  {
    return (v == neg_infinity().as_number());
  }
  static bool is_pos_inf(int_type v)
  {
    return (v == pos_infinity().as_number());
  }
  static bool is_not_a_number(int_type v)
  {
    return (v == not_a_number().as_number());
  }
  //! Returns either special value type or is_not_special
  static special_values to_special(int_type v)
  {
    if (is_not_a_number(v)) return not_a_date_time;
    if (is_neg_inf(v)) return neg_infin;
    if (is_pos_inf(v)) return pos_infin;
    return not_special;
  }

  //-3 leaves room for representations of infinity and not a date
  static  int_type maxcount()
  {
    return (::std::numeric_limits<int_type>::max)()-3;
  }
  bool is_infinity() const
  {
    return (value_ == neg_infinity().as_number() ||
            value_ == pos_infinity().as_number());
  }
  bool is_pos_infinity()const
  {
    return(value_ == pos_infinity().as_number());
  }
  bool is_neg_infinity()const
  {
    return(value_ == neg_infinity().as_number());
  }
  bool is_nan() const
  {
    return (value_ == not_a_number().as_number());
  }
  bool is_special() const
  {
    return(is_infinity() || is_nan());
  }
  bool operator==(const int_adapter& rhs) const
  {
    return (compare(rhs) == 0);
  }
  bool operator==(const int& rhs) const
  {
    if(!std::numeric_limits<int_type>::is_signed)
    {
      if(is_neg_inf(value_) && rhs == 0)
      {
        return false;
      }
    }
    return (compare(rhs) == 0);
  }
  bool operator!=(const int_adapter& rhs) const
  {
    return (compare(rhs) != 0);
  }
  bool operator!=(const int& rhs) const
  {
    if(!std::numeric_limits<int_type>::is_signed)
    {
      if(is_neg_inf(value_) && rhs == 0)
      {
        return true;
      }
    }
    return (compare(rhs) != 0);
  }
  bool operator<(const int_adapter& rhs) const
  {
    return (compare(rhs) == -1);
  }
  bool operator<(const int& rhs) const
  {
    // quiets compiler warnings
    if(!std::numeric_limits<int_type>::is_signed)
    {
      if(is_neg_inf(value_) && rhs == 0)
      {
        return true;
      }
    }
    return (compare(rhs) == -1);
  }
  bool operator>(const int_adapter& rhs) const
  {
    return (compare(rhs) == 1);
  }
  int_type as_number() const
  {
    return value_;
  }
  //! Returns either special value type or is_not_special
  special_values as_special() const
  {
    return int_adapter::to_special(value_);
  }
  //creates nasty ambiguities
//   operator int_type() const
//   {
//     return value_;
//   }

  /*! Operator allows for adding dissimilar int_adapter types.
   * The return type will match that of the the calling object's type */
  template<class rhs_type>
  inline
  int_adapter operator+(const int_adapter<rhs_type>& rhs) const
  {
    if(is_special() || rhs.is_special())
    {
      if (is_nan() || rhs.is_nan())
      {
        return int_adapter::not_a_number();
      }
      if((is_pos_inf(value_) && rhs.is_neg_inf(rhs.as_number())) ||
      (is_neg_inf(value_) && rhs.is_pos_inf(rhs.as_number())) )
      {
        return int_adapter::not_a_number();
      }
      if (is_infinity())
      {
        return *this;
      }
      if (rhs.is_pos_inf(rhs.as_number()))
      {
        return int_adapter::pos_infinity();
      }
      if (rhs.is_neg_inf(rhs.as_number()))
      {
        return int_adapter::neg_infinity();
      }
    }
    return int_adapter<int_type>(value_ + static_cast<int_type>(rhs.as_number()));
  }

  int_adapter operator+(const int_type rhs) const
  {
    if(is_special())
    {
      if (is_nan())
      {
        return int_adapter<int_type>(not_a_number());
      }
      if (is_infinity())
      {
        return *this;
      }
    }
    return int_adapter<int_type>(value_ + rhs);
  }

  /*! Operator allows for subtracting dissimilar int_adapter types.
   * The return type will match that of the the calling object's type */
  template<class rhs_type>
  inline
  int_adapter operator-(const int_adapter<rhs_type>& rhs)const
  {
    if(is_special() || rhs.is_special())
    {
      if (is_nan() || rhs.is_nan())
      {
        return int_adapter::not_a_number();
      }
      if((is_pos_inf(value_) && rhs.is_pos_inf(rhs.as_number())) ||
         (is_neg_inf(value_) && rhs.is_neg_inf(rhs.as_number())) )
      {
        return int_adapter::not_a_number();
      }
      if (is_infinity())
      {
        return *this;
      }
      if (rhs.is_pos_inf(rhs.as_number()))
      {
        return int_adapter::neg_infinity();
      }
      if (rhs.is_neg_inf(rhs.as_number()))
      {
        return int_adapter::pos_infinity();
      }
    }
    return int_adapter<int_type>(value_ - static_cast<int_type>(rhs.as_number()));
  }
  int_adapter operator-(const int_type rhs) const
  {
    if(is_special())
    {
      if (is_nan())
      {
        return int_adapter<int_type>(not_a_number());
      }
      if (is_infinity())
      {
        return *this;
      }
    }
    return int_adapter<int_type>(value_ - rhs);
  }

  // should templatize this to be consistant with op +-
  int_adapter operator*(const int_adapter& rhs)const
  {
    if(this->is_special() || rhs.is_special())
    {
      return mult_div_specials(rhs);
    }
    return int_adapter<int_type>(value_ * rhs.value_);
  }
  /*! Provided for cases when automatic conversion from
   * 'int' to 'int_adapter' causes incorrect results. */
  int_adapter operator*(const int rhs) const
  {
    if(is_special())
    {
      return mult_div_specials(rhs);
    }
    return int_adapter<int_type>(value_ * rhs);
  }

  // should templatize this to be consistant with op +-
  int_adapter operator/(const int_adapter& rhs)const
  {
    if(this->is_special() || rhs.is_special())
    {
      if(is_infinity() && rhs.is_infinity())
      {
        return int_adapter<int_type>(not_a_number());
      }
      if(rhs != 0)
      {
        return mult_div_specials(rhs);
      }
      else { // let divide by zero blow itself up
        return int_adapter<int_type>(value_ / rhs.value_);
      }
    }
    return int_adapter<int_type>(value_ / rhs.value_);
  }
  /*! Provided for cases when automatic conversion from
   * 'int' to 'int_adapter' causes incorrect results. */
  int_adapter operator/(const int rhs) const
  {
    if(is_special() && rhs != 0)
    {
      return mult_div_specials(rhs);
    }
    return int_adapter<int_type>(value_ / rhs);
  }

  // should templatize this to be consistant with op +-
  int_adapter operator%(const int_adapter& rhs)const
  {
    if(this->is_special() || rhs.is_special())
    {
      if(is_infinity() && rhs.is_infinity())
      {
        return int_adapter<int_type>(not_a_number());
      }
      if(rhs != 0)
      {
        return mult_div_specials(rhs);
      }
      else { // let divide by zero blow itself up
        return int_adapter<int_type>(value_ % rhs.value_);
      }
    }
    return int_adapter<int_type>(value_ % rhs.value_);
  }
  /*! Provided for cases when automatic conversion from
   * 'int' to 'int_adapter' causes incorrect results. */
  int_adapter operator%(const int rhs) const
  {
    if(is_special() && rhs != 0)
    {
      return mult_div_specials(rhs);
    }
    return int_adapter<int_type>(value_ % rhs);
  }
private:
  int_type value_;

  //! returns -1, 0, 1, or 2 if 'this' is <, ==, >, or 'nan comparison' rhs
  int compare(const int_adapter& rhs)const
  {
    if(this->is_special() || rhs.is_special())
    {
      if(this->is_nan() || rhs.is_nan()) {
        if(this->is_nan() && rhs.is_nan()) {
          return 0; // equal
        }
        else {
          return 2; // nan
        }
      }
      if((is_neg_inf(value_) && !is_neg_inf(rhs.value_)) ||
         (is_pos_inf(rhs.value_) && !is_pos_inf(value_)) )
        {
          return -1; // less than
        }
      if((is_pos_inf(value_) && !is_pos_inf(rhs.value_)) ||
         (is_neg_inf(rhs.value_) && !is_neg_inf(value_)) ) {
        return 1; // greater than
      }
    }
    if(value_ < rhs.value_) return -1;
    if(value_ > rhs.value_) return 1;
    // implied-> if(value_ == rhs.value_)
    return 0;
  }
  /* When multiplying and dividing with at least 1 special value
   * very simmilar rules apply. In those cases where the rules
   * are different, they are handled in the respective operator
   * function. */
  //! Assumes at least 'this' or 'rhs' is a special value
  int_adapter mult_div_specials(const int_adapter& rhs)const
  {
    if(this->is_nan() || rhs.is_nan()) {
      return int_adapter<int_type>(not_a_number());
    }
    BOOST_CONSTEXPR_OR_CONST int min_value = std::numeric_limits<int_type>::is_signed ? 0 : 1;
    if((*this > 0 && rhs > 0) || (*this < min_value && rhs < min_value)) {
        return int_adapter<int_type>(pos_infinity());
    }
    if((*this > 0 && rhs < min_value) || (*this < min_value && rhs > 0)) {
        return int_adapter<int_type>(neg_infinity());
    }
    //implied -> if(this->value_ == 0 || rhs.value_ == 0)
    return int_adapter<int_type>(not_a_number());
  }
  /* Overloaded function necessary because of special
   * situation where int_adapter is instantiated with
   * 'unsigned' and func is called with negative int.
   * It would produce incorrect results since 'unsigned'
   * wraps around when initialized with a negative value */
  //! Assumes 'this' is a special value
  int_adapter mult_div_specials(const int& rhs) const
  {
    if(this->is_nan()) {
      return int_adapter<int_type>(not_a_number());
    }
    BOOST_CONSTEXPR_OR_CONST int min_value = std::numeric_limits<int_type>::is_signed ? 0 : 1;
    if((*this > 0 && rhs > 0) || (*this < min_value && rhs < 0)) {
        return int_adapter<int_type>(pos_infinity());
    }
    if((*this > 0 && rhs < 0) || (*this < min_value && rhs > 0)) {
        return int_adapter<int_type>(neg_infinity());
    }
    //implied -> if(this->value_ == 0 || rhs.value_ == 0)
    return int_adapter<int_type>(not_a_number());
  }

};

#ifndef BOOST_DATE_TIME_NO_LOCALE
  /*! Expected output is either a numeric representation
   * or a special values representation.<BR>
   * Ex. "12", "+infinity", "not-a-number", etc. */
  //template<class charT = char, class traits = std::traits<charT>, typename int_type>
  template<class charT, class traits, typename int_type>
  inline
  std::basic_ostream<charT, traits>&
  operator<<(std::basic_ostream<charT, traits>& os, const int_adapter<int_type>& ia)
  {
    if(ia.is_special()) {
      // switch copied from date_names_put.hpp
      switch(ia.as_special())
        {
      case not_a_date_time:
        os << "not-a-number";
        break;
      case pos_infin:
        os << "+infinity";
        break;
      case neg_infin:
        os << "-infinity";
        break;
      default:
        os << "";
      }
    }
    else {
      os << ia.as_number();
    }
    return os;
  }
#endif


} } //namespace date_time

#if defined(BOOST_MSVC)
#pragma warning(pop)
#endif

#endif