GRASS GIS 8 Programmer's Manual  8.5.0dev(2024)-d6dec75dd4
local.c
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1 /*
2  * Copyright (C) 1995. Bill Brown <brown@gis.uiuc.edu> & Michael Shapiro
3  *
4  * This program is free software under the GPL (>=v2)
5  * Read the file GPL.TXT coming with GRASS for details.
6  */
7 #include <time.h>
8 #include <grass/datetime.h>
9 
10 /*
11  ** NOTE: the extern variable "timezone" seems to be treated
12  ** differently by different OS, and the tm_zone element of struct tm
13  ** is missing in some OS (IRIX), so we're converting localtime() and
14  ** gmtime() structures to datetimes, then doing a difference to get the
15  ** timezone offset. -Bill Brown 5/31/95
16  */
17 
18 /*!
19  * \brief
20  *
21  * Returns:
22  * 0 OK
23  * -1 local timezone info not available
24  *
25  * \param minutes
26  * \return int
27  */
28 
29 int datetime_get_local_timezone(int *minutes)
30 {
31  struct tm *local, *gm;
32  time_t clock;
33  DateTime dtl, dtg, dtdiff;
34 
35  time(&clock);
36 
37  local = localtime(&clock);
38 
39  datetime_set_type(&dtl, DATETIME_ABSOLUTE, DATETIME_YEAR, DATETIME_SECOND,
40  0);
41 
42  /* now put current {year,month,day,hour,minute,second} into local */
43  datetime_set_year(&dtl, (int)local->tm_year + 1900);
44  datetime_set_month(&dtl, (int)local->tm_mon + 1);
45  datetime_set_day(&dtl, (int)local->tm_mday);
46  datetime_set_hour(&dtl, (int)local->tm_hour);
47  datetime_set_minute(&dtl, (int)local->tm_min);
48  datetime_set_second(&dtl, (double)local->tm_sec);
49 
50  gm = gmtime(&clock);
51 
52  datetime_set_type(&dtg, DATETIME_ABSOLUTE, DATETIME_YEAR, DATETIME_SECOND,
53  0);
54 
55  /* now put current {year,month,day,hour,minute,second} into gmt */
56  datetime_set_year(&dtg, (int)gm->tm_year + 1900);
57  datetime_set_month(&dtg, (int)gm->tm_mon + 1);
58  datetime_set_day(&dtg, (int)gm->tm_mday);
59  datetime_set_hour(&dtg, (int)gm->tm_hour);
60  datetime_set_minute(&dtg, (int)gm->tm_min);
61  datetime_set_second(&dtg, (double)gm->tm_sec);
62 
63  datetime_set_type(&dtdiff, DATETIME_RELATIVE, DATETIME_DAY, DATETIME_SECOND,
64  0);
65  datetime_difference(&dtl, &dtg, &dtdiff);
66  datetime_change_from_to(&dtdiff, DATETIME_MINUTE, DATETIME_MINUTE, 0);
67 
68  *minutes = dtdiff.positive ? dtdiff.minute : -dtdiff.minute;
69  return 0;
70 }
71 
72 /*!
73  * \brief
74  *
75  * set mode/from/to ABSOLUTE/YEAR/SECOND
76  * set the local time into 'dt' does not set timezone.
77  *
78  * \param dt
79  * \return void
80  */
81 
82 void datetime_get_local_time(DateTime *dt)
83 {
84  time_t clock;
85  struct tm *local;
86 
87  /* first set dt to absolute full date */
88  datetime_set_type(dt, DATETIME_ABSOLUTE, DATETIME_YEAR, DATETIME_SECOND, 0);
89 
90  /* get the current date/time */
91  time(&clock);
92  local = localtime(&clock);
93 
94  /* now put current {year,month,day,hour,minute,second} into dt */
95  datetime_set_year(dt, (int)local->tm_year + 1900);
96  datetime_set_month(dt, (int)local->tm_mon + 1);
97  datetime_set_day(dt, (int)local->tm_mday);
98  datetime_set_hour(dt, (int)local->tm_hour);
99  datetime_set_minute(dt, (int)local->tm_min);
100  datetime_set_second(dt, (double)local->tm_sec);
101 }
DATETIME_ABSOLUTE
#define DATETIME_ABSOLUTE
Definition: datetime.h:4
DATETIME_DAY
#define DATETIME_DAY
Definition: datetime.h:12
DATETIME_SECOND
#define DATETIME_SECOND
Definition: datetime.h:15
DATETIME_MINUTE
#define DATETIME_MINUTE
Definition: datetime.h:14
DATETIME_RELATIVE
#define DATETIME_RELATIVE
Definition: datetime.h:5
DATETIME_YEAR
#define DATETIME_YEAR
Definition: datetime.h:10
datetime_difference
int datetime_difference(const DateTime *a, const DateTime *b, DateTime *result)
This performs the formula: result = a - b;.
Definition: diff.c:79
datetime_set_day
int datetime_set_day(DateTime *dt, int day)
if dt.mode = ABSOLUTE, then the dt.year, dt.month:
Definition: values.c:340
datetime_set_month
int datetime_set_month(DateTime *dt, int month)
if dt.mode = ABSOLUTE, this also sets dt.day = 0
Definition: values.c:288
datetime_set_type
int datetime_set_type(DateTime *dt, int mode, int from, int to, int fracsec)
Definition: datetime/type.c:36
datetime_set_hour
int datetime_set_hour(DateTime *dt, int hour)
returns 0 on success or negative value on error
Definition: values.c:382
datetime_set_year
int datetime_set_year(DateTime *dt, int year)
if dt.mode = ABSOLUTE, this also sets dt.day = 0
Definition: values.c:241
datetime_set_second
int datetime_set_second(DateTime *dt, double second)
returns 0 on success or negative value on error
Definition: values.c:466
datetime_change_from_to
int datetime_change_from_to(DateTime *dt, int from, int to, int round)
Changes the from/to of the type for dt. The 'from/to' must be legal values for the mode of dt; (if th...
Definition: change.c:54
datetime_set_minute
int datetime_set_minute(DateTime *dt, int minute)
returns 0 on success or negative value on error
Definition: values.c:424
datetime_get_local_time
void datetime_get_local_time(DateTime *dt)
set mode/from/to ABSOLUTE/YEAR/SECOND set the local time into 'dt' does not set timezone.
Definition: local.c:82
datetime_get_local_timezone
int datetime_get_local_timezone(int *minutes)
Returns: 0 OK -1 local timezone info not available.
Definition: local.c:29
DateTime::positive
int positive
Definition: datetime.h:24
DateTime::minute
int minute
Definition: datetime.h:22