1 #ifndef READR_DATE_TIME_H_
2 #define READR_DATE_TIME_H_
3
4 #include "cpp11/R.hpp"
5
6 #include <stdlib.h>
7 #include <string>
8 #include <tzdb/tzdb.h>
9
10 // Much of this code is adapted from R's src/main/datetime.c.
11 // Author: The R Core Team.
12 // License: GPL >= 2
13
14 static const int month_length[12] = {
15 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
16 static const int month_start[12] = {
17 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
18
19 // Leap days occur in a 400 year cycle: this records the cumulative number
20 // of leap days in per cycle. Generated with:
21 // is_leap <- function(y) (y %% 4) == 0 & ((y %% 100) != 0 | (y %% 400) == 0)
22 // cumsum(is_leap(0:399))
23 static const int leap_days[400] = {
24 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5,
25 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10,
26 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14,
27 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19,
28 19, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23, 24, 24,
29 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 27, 28,
30 28, 28, 28, 29, 29, 29, 29, 30, 30, 30, 30, 31, 31, 31, 31, 32, 32, 32, 32,
31 33, 33, 33, 33, 34, 34, 34, 34, 35, 35, 35, 35, 36, 36, 36, 36, 37, 37, 37,
32 37, 38, 38, 38, 38, 39, 39, 39, 39, 40, 40, 40, 40, 41, 41, 41, 41, 42, 42,
33 42, 42, 43, 43, 43, 43, 44, 44, 44, 44, 45, 45, 45, 45, 46, 46, 46, 46, 47,
34 47, 47, 47, 48, 48, 48, 48, 49, 49, 49, 49, 49, 49, 49, 49, 50, 50, 50, 50,
35 51, 51, 51, 51, 52, 52, 52, 52, 53, 53, 53, 53, 54, 54, 54, 54, 55, 55, 55,
36 55, 56, 56, 56, 56, 57, 57, 57, 57, 58, 58, 58, 58, 59, 59, 59, 59, 60, 60,
37 60, 60, 61, 61, 61, 61, 62, 62, 62, 62, 63, 63, 63, 63, 64, 64, 64, 64, 65,
38 65, 65, 65, 66, 66, 66, 66, 67, 67, 67, 67, 68, 68, 68, 68, 69, 69, 69, 69,
39 70, 70, 70, 70, 71, 71, 71, 71, 72, 72, 72, 72, 73, 73, 73, 73, 73, 73, 73,
40 73, 74, 74, 74, 74, 75, 75, 75, 75, 76, 76, 76, 76, 77, 77, 77, 77, 78, 78,
41 78, 78, 79, 79, 79, 79, 80, 80, 80, 80, 81, 81, 81, 81, 82, 82, 82, 82, 83,
42 83, 83, 83, 84, 84, 84, 84, 85, 85, 85, 85, 86, 86, 86, 86, 87, 87, 87, 87,
43 88, 88, 88, 88, 89, 89, 89, 89, 90, 90, 90, 90, 91, 91, 91, 91, 92, 92, 92,
44 92, 93, 93, 93, 93, 94, 94, 94, 94, 95, 95, 95, 95, 96, 96, 96, 96, 97, 97,
45 97};
46
47 static const int cycle_days = 400 * 365 + 97;
48
is_leap(unsigned y)49 inline int is_leap(unsigned y) {
50 return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0);
51 }
52
53 class DateTime {
54 int year_, mon_, day_, hour_, min_, sec_, offset_;
55 double psec_;
56 std::string tz_;
57
58 public:
59 DateTime(
60 int year,
61 int mon,
62 int day,
63 int hour = 0,
64 int min = 0,
65 int sec = 0,
66 double psec = 0,
67 const std::string& tz = "UTC")
year_(year)68 : year_(year),
69 mon_(mon),
70 day_(day),
71 hour_(hour),
72 min_(min),
73 sec_(sec),
74 offset_(0),
75 psec_(psec),
76 tz_(tz) {}
77
78 // Used to add time zone offsets which can only be easily applied once
79 // we've converted into seconds since epoch.
setOffset(int offset)80 void setOffset(int offset) { offset_ = offset; }
81
82 // Is this a valid date time?
validDateTime()83 bool validDateTime() const { return validDate() && validTime(); }
84
validDate()85 bool validDate() const {
86 if (year_ < 0)
87 return false;
88
89 return (date::year{year_} / mon_ / day_).ok();
90 }
91
validTime()92 bool validTime() const {
93 if (sec_ < 0 || sec_ > 60)
94 return false;
95 if (min_ < 0 || min_ > 59)
96 return false;
97 if (hour_ < 0 || hour_ > 23)
98 return false;
99
100 return true;
101 }
102
validDuration()103 bool validDuration() const {
104 if (sec_ < -59 || sec_ > 59)
105 return false;
106 if (min_ < -59 || min_ > 59)
107 return false;
108
109 return true;
110 }
111
datetime()112 double datetime() const { return (tz_ == "UTC") ? utctime() : localtime(); }
113
date()114 int date() const { return utcdate(); }
115
time()116 double time() const {
117 return psec_ + sec_ + (min_ * 60.0) + (hour_ * 3600.0);
118 }
119
120 private:
121 // Number of number of seconds since 1970-01-01T00:00:00Z.
122 // Compared to usual implementations this returns a double, and supports
123 // a wider range of dates. Invalid dates have undefined behaviour.
utctime()124 double utctime() const { return utcdate() * 86400.0 + time() + offset_; }
125
126 // Find number of days since 1970-01-01.
127 // Invalid dates have undefined behaviour.
utcdate()128 int utcdate() const {
129 if (!validDate())
130 return NA_REAL;
131
132 const date::year_month_day ymd{date::year(year_) / mon_ / day_};
133 const date::sys_days st{ymd};
134 return st.time_since_epoch().count();
135 }
136
localtime()137 double localtime() const {
138 if (!validDateTime())
139 return NA_REAL;
140
141 const date::time_zone* p_time_zone;
142
143 if (!tzdb::locate_zone(tz_, p_time_zone)) {
144 throw std::runtime_error(
145 "'" + tz_ + "' not found in the time zone database.");
146 }
147
148 const date::local_seconds lt =
149 std::chrono::seconds{sec_} + std::chrono::minutes{min_} +
150 std::chrono::hours{hour_} +
151 date::local_days{date::year{year_} / mon_ / day_};
152
153 date::local_info info;
154
155 if (!tzdb::get_local_info(lt, p_time_zone, info)) {
156 throw std::runtime_error(
157 "Can't lookup local time info for the supplied time zone.");
158 }
159
160 switch (info.result) {
161 case date::local_info::unique:
162 return (lt.time_since_epoch() - info.first.offset).count() + psec_ +
163 offset_;
164 case date::local_info::ambiguous:
165 // Choose `earliest` of the two ambiguous times
166 return (lt.time_since_epoch() - info.first.offset).count() + psec_ +
167 offset_;
168 case date::local_info::nonexistent:
169 return NA_REAL;
170 }
171
172 throw std::runtime_error("should never happen");
173 }
174 };
175
176 #endif
177