1 #ifndef DATE_TIME_PERIOD_HPP___
2 #define DATE_TIME_PERIOD_HPP___
3 
4 /* Copyright (c) 2002,2003 CrystalClear Software, Inc.
5  * Use, modification and distribution is subject to the
6  * Boost Software License, Version 1.0. (See accompanying
7  * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
8  * Author: Jeff Garland, Bart Garst
9  * $Date$
10  */
11 
12 /*! \file period.hpp
13   This file contain the implementation of the period abstraction. This is
14   basically the same idea as a range.  Although this class is intended for
15   use in the time library, it is pretty close to general enough for other
16   numeric uses.
17 
18 */
19 
20 #include "boost/operators.hpp"
21 
22 
23 namespace boost {
24 namespace date_time {
25   //!Provides generalized period type useful in date-time systems
26   /*!This template uses a class to represent a time point within the period
27     and another class to represent a duration.  As a result, this class is
28     not appropriate for use when the number and duration representation
29     are the same (eg: in the regular number domain).
30 
31     A period can be specified by providing either the begining point and
32     a duration or the begining point and the end point( end is NOT part
33     of the period but 1 unit past it. A period will be "invalid" if either
34     end_point <= begin_point or the given duration is <= 0. Any valid period
35     will return false for is_null().
36 
37     Zero length periods are also considered invalid. Zero length periods are
38     periods where the begining and end points are the same, or, the given
39     duration is zero. For a zero length period, the last point will be one
40     unit less than the begining point.
41 
42     In the case that the begin and last are the same, the period has a
43     length of one unit.
44 
45     The best way to handle periods is usually to provide a begining point and
46     a duration.  So, day1 + 7 days is a week period which includes all of the
47     first day and 6 more days (eg: Sun to Sat).
48 
49    */
50   template<class point_rep, class duration_rep>
51   class period : private
52       boost::less_than_comparable<period<point_rep, duration_rep>
53     , boost::equality_comparable< period<point_rep, duration_rep>
54     > >
55   {
56   public:
57     typedef point_rep point_type;
58     typedef duration_rep duration_type;
59 
60     period(point_rep first_point, point_rep end_point);
61     period(point_rep first_point, duration_rep len);
62     point_rep begin() const;
63     point_rep end() const;
64     point_rep last() const;
65     duration_rep length() const;
66     bool is_null() const;
67     bool operator==(const period& rhs) const;
68     bool operator<(const period& rhs) const;
69     void shift(const duration_rep& d);
70     void expand(const duration_rep& d);
71     bool contains(const point_rep& point) const;
72     bool contains(const period& other) const;
73     bool intersects(const period& other) const;
74     bool is_adjacent(const period& other) const;
75     bool is_before(const point_rep& point) const;
76     bool is_after(const point_rep& point) const;
77     period intersection(const period& other) const;
78     period merge(const period& other) const;
79     period span(const period& other) const;
80   private:
81     point_rep begin_;
82     point_rep last_;
83   };
84 
85   //! create a period from begin to last eg: [begin,end)
86   /*! If end <= begin then the period will be invalid
87    */
88   template<class point_rep, class duration_rep>
89   inline
period(point_rep first_point,point_rep end_point)90   period<point_rep,duration_rep>::period(point_rep first_point,
91                                          point_rep end_point) :
92     begin_(first_point),
93     last_(end_point - duration_rep::unit())
94   {}
95 
96   //! create a period as [begin, begin+len)
97   /*! If len is <= 0 then the period will be invalid
98    */
99   template<class point_rep, class duration_rep>
100   inline
period(point_rep first_point,duration_rep len)101   period<point_rep,duration_rep>::period(point_rep first_point, duration_rep len) :
102     begin_(first_point),
103     last_(first_point + len-duration_rep::unit())
104   { }
105 
106 
107   //! Return the first element in the period
108   template<class point_rep, class duration_rep>
109   inline
begin() const110   point_rep period<point_rep,duration_rep>::begin() const
111   {
112     return begin_;
113   }
114 
115   //! Return one past the last element
116   template<class point_rep, class duration_rep>
117   inline
end() const118   point_rep period<point_rep,duration_rep>::end() const
119   {
120     return last_ + duration_rep::unit();
121   }
122 
123   //! Return the last item in the period
124   template<class point_rep, class duration_rep>
125   inline
last() const126   point_rep period<point_rep,duration_rep>::last() const
127   {
128     return last_;
129   }
130 
131   //! True if period is ill formed (length is zero or less)
132   template<class point_rep, class duration_rep>
133   inline
is_null() const134   bool period<point_rep,duration_rep>::is_null() const
135   {
136     return end() <= begin_;
137   }
138 
139   //! Return the length of the period
140   template<class point_rep, class duration_rep>
141   inline
length() const142   duration_rep period<point_rep,duration_rep>::length() const
143   {
144     if(last_ < begin_){ // invalid period
145       return last_+duration_rep::unit() - begin_;
146     }
147     else{
148       return end() - begin_; // normal case
149     }
150   }
151 
152   //! Equality operator
153   template<class point_rep, class duration_rep>
154   inline
operator ==(const period & rhs) const155   bool period<point_rep,duration_rep>::operator==(const period& rhs) const
156   {
157     return  ((begin_ == rhs.begin_) &&
158              (last_ == rhs.last_));
159   }
160 
161   //! Strict as defined by rhs.last <= lhs.last
162   template<class point_rep, class duration_rep>
163   inline
operator <(const period & rhs) const164   bool period<point_rep,duration_rep>::operator<(const period& rhs) const
165   {
166     return (last_ < rhs.begin_);
167   }
168 
169 
170   //! Shift the start and end by the specified amount
171   template<class point_rep, class duration_rep>
172   inline
shift(const duration_rep & d)173   void period<point_rep,duration_rep>::shift(const duration_rep& d)
174   {
175     begin_ = begin_ + d;
176     last_  = last_  + d;
177   }
178 
179   /** Expands the size of the period by the duration on both ends.
180    *
181    *So before expand
182    *@code
183    *
184    *         [-------]
185    * ^   ^   ^   ^   ^   ^  ^
186    * 1   2   3   4   5   6  7
187    *
188    *@endcode
189    * After expand(2)
190    *@code
191    *
192    * [----------------------]
193    * ^   ^   ^   ^   ^   ^  ^
194    * 1   2   3   4   5   6  7
195    *
196    *@endcode
197    */
198   template<class point_rep, class duration_rep>
199   inline
expand(const duration_rep & d)200   void period<point_rep,duration_rep>::expand(const duration_rep& d)
201   {
202     begin_ = begin_ - d;
203     last_  = last_  + d;
204   }
205 
206   //! True if the point is inside the period, zero length periods contain no points
207   template<class point_rep, class duration_rep>
208   inline
contains(const point_rep & point) const209   bool period<point_rep,duration_rep>::contains(const point_rep& point) const
210   {
211     return ((point >= begin_) &&
212             (point <= last_));
213   }
214 
215 
216   //! True if this period fully contains (or equals) the other period
217   template<class point_rep, class duration_rep>
218   inline
contains(const period<point_rep,duration_rep> & other) const219   bool period<point_rep,duration_rep>::contains(const period<point_rep,duration_rep>& other) const
220   {
221     return ((begin_ <= other.begin_) && (last_ >= other.last_));
222   }
223 
224 
225   //! True if periods are next to each other without a gap.
226   /* In the example below, p1 and p2 are adjacent, but p3 is not adjacent
227    * with either of p1 or p2.
228    *@code
229    *   [-p1-)
230    *        [-p2-)
231    *          [-p3-)
232    *@endcode
233    */
234   template<class point_rep, class duration_rep>
235   inline
236   bool
is_adjacent(const period<point_rep,duration_rep> & other) const237   period<point_rep,duration_rep>::is_adjacent(const period<point_rep,duration_rep>& other) const
238   {
239     return (other.begin() == end() ||
240             begin_ == other.end());
241   }
242 
243 
244   //! True if all of the period is prior or t < start
245   /* In the example below only point 1 would evaluate to true.
246    *@code
247    *     [---------])
248    * ^   ^    ^     ^   ^
249    * 1   2    3     4   5
250    *
251    *@endcode
252    */
253   template<class point_rep, class duration_rep>
254   inline
255   bool
is_after(const point_rep & t) const256   period<point_rep,duration_rep>::is_after(const point_rep& t) const
257   {
258     if (is_null())
259     {
260       return false; //null period isn't after
261     }
262 
263     return t < begin_;
264   }
265 
266   //! True if all of the period is prior to the passed point or end <= t
267   /* In the example below points 4 and 5 return true.
268    *@code
269    *     [---------])
270    * ^   ^    ^     ^   ^
271    * 1   2    3     4   5
272    *
273    *@endcode
274    */
275   template<class point_rep, class duration_rep>
276   inline
277   bool
is_before(const point_rep & t) const278   period<point_rep,duration_rep>::is_before(const point_rep& t) const
279   {
280     if (is_null())
281     {
282       return false;  //null period isn't before anything
283     }
284 
285     return last_ < t;
286   }
287 
288 
289   //! True if the periods overlap in any way
290   /* In the example below p1 intersects with p2, p4, and p6.
291    *@code
292    *       [---p1---)
293    *             [---p2---)
294    *                [---p3---)
295    *  [---p4---)
296    * [-p5-)
297    *         [-p6-)
298    *@endcode
299    */
300   template<class point_rep, class duration_rep>
301   inline
intersects(const period<point_rep,duration_rep> & other) const302   bool period<point_rep,duration_rep>::intersects(const period<point_rep,duration_rep>& other) const
303   {
304     return ( contains(other.begin_) ||
305              other.contains(begin_) ||
306              ((other.begin_ < begin_) && (other.last_ >= begin_)));
307   }
308 
309   //! Returns the period of intersection or invalid range no intersection
310   template<class point_rep, class duration_rep>
311   inline
312   period<point_rep,duration_rep>
intersection(const period<point_rep,duration_rep> & other) const313   period<point_rep,duration_rep>::intersection(const period<point_rep,duration_rep>& other) const
314   {
315     if (begin_ > other.begin_) {
316       if (last_ <= other.last_) { //case2
317         return *this;
318       }
319       //case 1
320       return period<point_rep,duration_rep>(begin_, other.end());
321     }
322     else {
323       if (last_ <= other.last_) { //case3
324         return period<point_rep,duration_rep>(other.begin_, this->end());
325       }
326       //case4
327       return other;
328     }
329     //unreachable
330   }
331 
332   //! Returns the union of intersecting periods -- or null period
333   /*!
334    */
335   template<class point_rep, class duration_rep>
336   inline
337   period<point_rep,duration_rep>
merge(const period<point_rep,duration_rep> & other) const338   period<point_rep,duration_rep>::merge(const period<point_rep,duration_rep>& other) const
339   {
340     if (this->intersects(other)) {
341       if (begin_ < other.begin_) {
342         return period<point_rep,duration_rep>(begin_, last_ > other.last_ ? this->end() : other.end());
343       }
344 
345       return period<point_rep,duration_rep>(other.begin_, last_ > other.last_ ? this->end() : other.end());
346 
347     }
348     return period<point_rep,duration_rep>(begin_,begin_); // no intersect return null
349   }
350 
351   //! Combine two periods with earliest start and latest end.
352   /*! Combines two periods and any gap between them such that
353    *  start = min(p1.start, p2.start)
354    *  end   = max(p1.end  , p2.end)
355    *@code
356    *        [---p1---)
357    *                       [---p2---)
358    * result:
359    *        [-----------p3----------)
360    *@endcode
361    */
362   template<class point_rep, class duration_rep>
363   inline
364   period<point_rep,duration_rep>
span(const period<point_rep,duration_rep> & other) const365   period<point_rep,duration_rep>::span(const period<point_rep,duration_rep>& other) const
366   {
367     point_rep start((begin_ < other.begin_) ? begin() : other.begin());
368     point_rep newend((last_  < other.last_)  ? other.end() : this->end());
369     return period<point_rep,duration_rep>(start, newend);
370   }
371 
372 
373 } } //namespace date_time
374 
375 
376 
377 #endif
378