sl@0: #ifndef DATE_TIME_PERIOD_HPP___
sl@0: #define DATE_TIME_PERIOD_HPP___
sl@0: 
sl@0: /*    Copyright (c) 2002,2003 CrystalClear Software, Inc.
sl@0:  *
sl@0:  * Distributed under the Boost Software License, Version 1.0.
sl@0:  *     (See accompanying file LICENSE_1_0.txt or copy at
sl@0:  *           http://www.boost.org/LICENSE_1_0.txt)
sl@0:  *
sl@0:  *
sl@0:  * Author: Jeff Garland, Bart Garst 
sl@0:  * $Date: 2006/07/17 03:56:05 $
sl@0:  */
sl@0: 
sl@0: /*! \file period.hpp
sl@0:   This file contain the implementation of the period abstraction. This is
sl@0:   basically the same idea as a range.  Although this class is intended for
sl@0:   use in the time library, it is pretty close to general enough for other
sl@0:   numeric uses.
sl@0: 
sl@0: */
sl@0: 
sl@0: #include "boost/operators.hpp"
sl@0: 
sl@0: 
sl@0: namespace boost {
sl@0: namespace date_time {
sl@0:   //!Provides generalized period type useful in date-time systems
sl@0:   /*!This template uses a class to represent a time point within the period
sl@0:     and another class to represent a duration.  As a result, this class is
sl@0:     not appropriate for use when the number and duration representation 
sl@0:     are the same (eg: in the regular number domain).
sl@0:     
sl@0:     A period can be specified by providing either the begining point and 
sl@0:     a duration or the begining point and the end point( end is NOT part 
sl@0:     of the period but 1 unit past it. A period will be "invalid" if either
sl@0:     end_point <= begin_point or the given duration is <= 0. Any valid period 
sl@0:     will return false for is_null().
sl@0:     
sl@0:     Zero length periods are also considered invalid. Zero length periods are
sl@0:     periods where the begining and end points are the same, or, the given 
sl@0:     duration is zero. For a zero length period, the last point will be one 
sl@0:     unit less than the begining point.
sl@0: 
sl@0:     In the case that the begin and last are the same, the period has a 
sl@0:     length of one unit.
sl@0:     
sl@0:     The best way to handle periods is usually to provide a begining point and
sl@0:     a duration.  So, day1 + 7 days is a week period which includes all of the
sl@0:     first day and 6 more days (eg: Sun to Sat).
sl@0: 
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   class period : private
sl@0:       boost::less_than_comparable<period<point_rep, duration_rep> 
sl@0:     , boost::equality_comparable< period<point_rep, duration_rep> 
sl@0:     > >
sl@0:   {
sl@0:   public:
sl@0:     typedef point_rep point_type;
sl@0:     typedef duration_rep duration_type;
sl@0: 
sl@0:     period(point_rep first_point, point_rep end_point);
sl@0:     period(point_rep first_point, duration_rep len);
sl@0:     point_rep begin() const;
sl@0:     point_rep end() const;
sl@0:     point_rep last() const;
sl@0:     duration_rep length() const;
sl@0:     bool is_null() const;
sl@0:     bool operator==(const period& rhs) const;
sl@0:     bool operator<(const period& rhs) const;
sl@0:     void shift(const duration_rep& d);
sl@0:     bool contains(const point_rep& point) const;
sl@0:     bool contains(const period& other) const;
sl@0:     bool intersects(const period& other) const;
sl@0:     bool is_adjacent(const period& other) const;
sl@0:     bool is_before(const point_rep& point) const;
sl@0:     bool is_after(const point_rep& point) const;
sl@0:     period intersection(const period& other) const;
sl@0:     period merge(const period& other) const;
sl@0:     period span(const period& other) const;
sl@0:   private:
sl@0:     point_rep begin_;
sl@0:     point_rep last_;
sl@0:   };
sl@0: 
sl@0:   //! create a period from begin to last eg: [begin,end)
sl@0:   /*! If end <= begin then the period will be invalid
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   period<point_rep,duration_rep>::period(point_rep first_point, 
sl@0:                                          point_rep end_point) : 
sl@0:     begin_(first_point), 
sl@0:     last_(end_point - duration_rep::unit())
sl@0:   {}
sl@0: 
sl@0:   //! create a period as [begin, begin+len)
sl@0:   /*! If len is <= 0 then the period will be invalid
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   period<point_rep,duration_rep>::period(point_rep first_point, duration_rep len) :
sl@0:     begin_(first_point), 
sl@0:     last_(first_point + len-duration_rep::unit())
sl@0:   { }
sl@0: 
sl@0: 
sl@0:   //! Return the first element in the period
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   point_rep period<point_rep,duration_rep>::begin() const 
sl@0:   {
sl@0:     return begin_;
sl@0:   }
sl@0: 
sl@0:   //! Return one past the last element 
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   point_rep period<point_rep,duration_rep>::end() const 
sl@0:   {
sl@0:     return last_ + duration_rep::unit();
sl@0:   }
sl@0: 
sl@0:   //! Return the last item in the period
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   point_rep period<point_rep,duration_rep>::last() const 
sl@0:   {
sl@0:     return last_;
sl@0:   }
sl@0: 
sl@0:   //! True if period is ill formed (length is zero or less)
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::is_null() const 
sl@0:   {
sl@0:     return end() <= begin_;
sl@0:   }
sl@0: 
sl@0:   //! Return the length of the period
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   duration_rep period<point_rep,duration_rep>::length() const
sl@0:   {
sl@0:     if(last_ < begin_){ // invalid period
sl@0:       return last_+duration_rep::unit() - begin_;
sl@0:     }
sl@0:     else{
sl@0:       return end() - begin_; // normal case
sl@0:     }
sl@0:   }
sl@0: 
sl@0:   //! Equality operator
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::operator==(const period& rhs) const 
sl@0:   {
sl@0:     return  ((begin_ == rhs.begin_) && 
sl@0:              (last_ == rhs.last_));
sl@0:   }
sl@0: 
sl@0:   //! Strict as defined by rhs.last <= lhs.last
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::operator<(const period& rhs) const 
sl@0:   {
sl@0:     return (last_ < rhs.begin_);
sl@0:   } 
sl@0: 
sl@0: 
sl@0:   //! Shift the start and end by the specified amount
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   void period<point_rep,duration_rep>::shift(const duration_rep& d)
sl@0:   {
sl@0:     begin_ = begin_ + d;
sl@0:     last_  = last_  + d;
sl@0:   }
sl@0: 
sl@0:   //! True if the point is inside the period, zero length periods contain no points
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::contains(const point_rep& point) const 
sl@0:   {
sl@0:     return ((point >= begin_) &&
sl@0:             (point <= last_));
sl@0:   }
sl@0: 
sl@0: 
sl@0:   //! True if this period fully contains (or equals) the other period
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::contains(const period<point_rep,duration_rep>& other) const
sl@0:   {
sl@0:     return ((begin_ <= other.begin_) && (last_ >= other.last_));
sl@0:   }
sl@0: 
sl@0: 
sl@0:   //! True if periods are next to each other without a gap.
sl@0:   /* In the example below, p1 and p2 are adjacent, but p3 is not adjacent
sl@0:    * with either of p1 or p2.
sl@0:    *@code
sl@0:    *   [-p1-)
sl@0:    *        [-p2-)
sl@0:    *          [-p3-) 
sl@0:    *@endcode
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool 
sl@0:   period<point_rep,duration_rep>::is_adjacent(const period<point_rep,duration_rep>& other) const 
sl@0:   {
sl@0:     return (other.begin() == end() ||
sl@0:             begin_ == other.end());
sl@0:   }
sl@0: 
sl@0: 
sl@0:   //! True if all of the period is prior or t < start
sl@0:   /* In the example below only point 1 would evaluate to true.
sl@0:    *@code
sl@0:    *     [---------])
sl@0:    * ^   ^    ^     ^   ^
sl@0:    * 1   2    3     4   5
sl@0:    * 
sl@0:    *@endcode
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool 
sl@0:   period<point_rep,duration_rep>::is_after(const point_rep& t) const 
sl@0:   { 
sl@0:     if (is_null()) 
sl@0:     {
sl@0:       return false; //null period isn't after
sl@0:     }
sl@0:     
sl@0:     return t < begin_;
sl@0:   }
sl@0: 
sl@0:   //! True if all of the period is prior to the passed point or end <= t
sl@0:   /* In the example below points 4 and 5 return true.
sl@0:    *@code
sl@0:    *     [---------])
sl@0:    * ^   ^    ^     ^   ^
sl@0:    * 1   2    3     4   5
sl@0:    * 
sl@0:    *@endcode
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool 
sl@0:   period<point_rep,duration_rep>::is_before(const point_rep& t) const 
sl@0:   { 
sl@0:     if (is_null()) 
sl@0:     {
sl@0:       return false;  //null period isn't before anything
sl@0:     }
sl@0:     
sl@0:     return last_ < t;
sl@0:   }
sl@0: 
sl@0: 
sl@0:   //! True if the periods overlap in any way
sl@0:   /* In the example below p1 intersects with p2, p4, and p6.
sl@0:    *@code
sl@0:    *       [---p1---)
sl@0:    *             [---p2---)
sl@0:    *                [---p3---) 
sl@0:    *  [---p4---) 
sl@0:    * [-p5-) 
sl@0:    *         [-p6-) 
sl@0:    *@endcode
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   bool period<point_rep,duration_rep>::intersects(const period<point_rep,duration_rep>& other) const 
sl@0:   { 
sl@0:     return ( contains(other.begin_) ||
sl@0:              other.contains(begin_) ||
sl@0:              ((other.begin_ < begin_) && (other.last_ >= begin_)));
sl@0:   }
sl@0: 
sl@0:   //! Returns the period of intersection or invalid range no intersection
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   period<point_rep,duration_rep>
sl@0:   period<point_rep,duration_rep>::intersection(const period<point_rep,duration_rep>& other) const 
sl@0:   {
sl@0:     if (begin_ > other.begin_) {
sl@0:       if (last_ <= other.last_) { //case2
sl@0:         return *this;  
sl@0:       }
sl@0:       //case 1
sl@0:       return period<point_rep,duration_rep>(begin_, other.end());
sl@0:     }
sl@0:     else {
sl@0:       if (last_ <= other.last_) { //case3
sl@0:         return period<point_rep,duration_rep>(other.begin_, this->end());
sl@0:       }
sl@0:       //case4
sl@0:       return other;
sl@0:     }
sl@0:     //unreachable
sl@0:   }
sl@0: 
sl@0:   //! Returns the union of intersecting periods -- or null period
sl@0:   /*! 
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   period<point_rep,duration_rep>
sl@0:   period<point_rep,duration_rep>::merge(const period<point_rep,duration_rep>& other) const 
sl@0:   {
sl@0:     if (this->intersects(other)) {      
sl@0:       if (begin_ < other.begin_) {
sl@0:         return period<point_rep,duration_rep>(begin_, last_ > other.last_ ? this->end() : other.end());
sl@0:       }
sl@0:       
sl@0:       return period<point_rep,duration_rep>(other.begin_, last_ > other.last_ ? this->end() : other.end());
sl@0:       
sl@0:     }
sl@0:     return period<point_rep,duration_rep>(begin_,begin_); // no intersect return null
sl@0:   }
sl@0: 
sl@0:   //! Combine two periods with earliest start and latest end.
sl@0:   /*! Combines two periods and any gap between them such that 
sl@0:    *  start = minimum(p1.start, p2.start)
sl@0:    *  end   = maximum(p1.end  , p2.end)
sl@0:    *@code
sl@0:    *        [---p1---)
sl@0:    *                       [---p2---)
sl@0:    * result:
sl@0:    *        [-----------p3----------) 
sl@0:    *@endcode
sl@0:    */
sl@0:   template<class point_rep, class duration_rep>
sl@0:   inline
sl@0:   period<point_rep,duration_rep>
sl@0:   period<point_rep,duration_rep>::span(const period<point_rep,duration_rep>& other) const 
sl@0:   {
sl@0:     point_rep start((begin_ < other.begin_) ? begin() : other.begin());
sl@0:     point_rep newend((last_  < other.last_)  ? other.end() : this->end());
sl@0:     return period<point_rep,duration_rep>(start, newend);
sl@0:   }
sl@0: 
sl@0: 
sl@0: } } //namespace date_time
sl@0: 
sl@0: 
sl@0: 
sl@0: #endif