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
23namespace boost {
24namespace 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
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
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
110 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
118 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
126 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
134 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
142 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
155 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
164 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
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
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
209 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
219 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
237 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
256 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
278 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
302 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>
313 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>
338 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>
365 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