boost/date_time/date.hpp
#ifndef DATE_TIME_DATE_HPP___ #define DATE_TIME_DATE_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: 2010-01-10 11:17:23 -0800 (Sun, 10 Jan 2010) $ */ #include <boost/operators.hpp> #include <boost/date_time/year_month_day.hpp> #include <boost/date_time/special_defs.hpp> namespace boost { namespace date_time { //!Representation of timepoint at the one day level resolution. /*! The date template represents an interface shell for a date class that is based on a year-month-day system such as the gregorian or iso systems. It provides basic operations to enable calculation and comparisons. <b>Theory</b> This date representation fundamentally departs from the C tm struct approach. The goal for this type is to provide efficient date operations (add, subtract) and storage (minimize space to represent) in a concrete class. Thus, the date uses a count internally to represent a particular date. The calendar parameter defines the policies for converting the the year-month-day and internal counted form here. Applications that need to perform heavy formatting of the same date repeatedly will perform better by using the year-month-day representation. Internally the date uses a day number to represent the date. This is a monotonic time representation. This representation allows for fast comparison as well as simplifying the creation of writing numeric operations. Essentially, the internal day number is like adjusted julian day. The adjustment is determined by the Epoch date which is represented as day 1 of the calendar. Day 0 is reserved for negative infinity so that any actual date is automatically greater than negative infinity. When a date is constructed from a date or formatted for output, the appropriate conversions are applied to create the year, month, day representations. */ template<class T, class calendar, class duration_type_> class date : private boost::less_than_comparable<T , boost::equality_comparable<T > > { public: typedef T date_type; typedef calendar calendar_type; typedef typename calendar::date_traits_type traits_type; typedef duration_type_ duration_type; typedef typename calendar::year_type year_type; typedef typename calendar::month_type month_type; typedef typename calendar::day_type day_type; typedef typename calendar::ymd_type ymd_type; typedef typename calendar::date_rep_type date_rep_type; typedef typename calendar::date_int_type date_int_type; typedef typename calendar::day_of_week_type day_of_week_type; date(year_type y, month_type m, day_type d) : days_(calendar::day_number(ymd_type(y, m, d))) {} date(const ymd_type& ymd) : days_(calendar::day_number(ymd)) {} //let the compiler write copy, assignment, and destructor year_type year() const { ymd_type ymd = calendar::from_day_number(days_); return ymd.year; } month_type month() const { ymd_type ymd = calendar::from_day_number(days_); return ymd.month; } day_type day() const { ymd_type ymd = calendar::from_day_number(days_); return ymd.day; } day_of_week_type day_of_week() const { ymd_type ymd = calendar::from_day_number(days_); return calendar::day_of_week(ymd); } ymd_type year_month_day() const { return calendar::from_day_number(days_); } bool operator<(const date_type& rhs) const { return days_ < rhs.days_; } bool operator==(const date_type& rhs) const { return days_ == rhs.days_; } //! check to see if date is a special value bool is_special()const { return(is_not_a_date() || is_infinity()); } //! check to see if date is not a value bool is_not_a_date() const { return traits_type::is_not_a_number(days_); } //! check to see if date is one of the infinity values bool is_infinity() const { return traits_type::is_inf(days_); } //! check to see if date is greater than all possible dates bool is_pos_infinity() const { return traits_type::is_pos_inf(days_); } //! check to see if date is greater than all possible dates bool is_neg_infinity() const { return traits_type::is_neg_inf(days_); } //! return as a special value or a not_special if a normal date special_values as_special() const { return traits_type::to_special(days_); } duration_type operator-(const date_type& d) const { if (!this->is_special() && !d.is_special()) { // The duration underlying type may be wider than the date underlying type. // Thus we calculate the difference in terms of two durations from some common fixed base date. typedef typename duration_type::duration_rep_type duration_rep_type; return duration_type(static_cast< duration_rep_type >(days_) - static_cast< duration_rep_type >(d.days_)); } else { // In this case the difference will be a special value, too date_rep_type val = date_rep_type(days_) - date_rep_type(d.days_); return duration_type(val.as_special()); } } date_type operator-(const duration_type& dd) const { if(dd.is_special()) { return date_type(date_rep_type(days_) - dd.get_rep()); } return date_type(date_rep_type(days_) - dd.days()); } date_type operator-=(const duration_type& dd) { *this = *this - dd; return date_type(days_); } date_rep_type day_count() const { return days_; } //allow internal access from operators date_type operator+(const duration_type& dd) const { if(dd.is_special()) { return date_type(date_rep_type(days_) + dd.get_rep()); } return date_type(date_rep_type(days_) + dd.days()); } date_type operator+=(const duration_type& dd) { *this = *this + dd; return date_type(days_); } //see reference protected: /*! This is a private constructor which allows for the creation of new dates. It is not exposed to users since that would require class users to understand the inner workings of the date class. */ explicit date(date_int_type days) : days_(days) {}; explicit date(date_rep_type days) : days_(days.as_number()) {}; date_int_type days_; }; } } // namespace date_time #endif