GRASS GIS 8 Programmer's Manual 8.3.2(2024)-exported
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tz2.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 <grass/datetime.h>
8
9/*!
10 * \brief
11 *
12 * if dt has a timezone, increment dt by minutes-dt.tz MINUTES and set dt.tz =
13 * minutes Returns: 0 OK <b>datetime_check_timezone</b> (dt) if not -4 if
14 * minutes invalid
15 *
16 * \param dt
17 * \param minutes
18 * \return int
19 */
20
21int datetime_change_timezone(DateTime *dt, int minutes)
22{ /* new timezone in minutes */
23 int stat;
24 int old_minutes, diff_minutes;
25 DateTime incr;
26
27 stat = datetime_get_timezone(dt, &old_minutes);
28 if (stat != 0)
29 return stat;
30 if (!datetime_is_valid_timezone(minutes))
31 return datetime_error(-4, "invalid datetime timezone");
32
33 /* create a relative minute increment */
34 datetime_set_type(&incr, DATETIME_RELATIVE, DATETIME_MINUTE,
35 DATETIME_MINUTE, 0);
36
37 /* BB - needed to set SIGN here */
38 diff_minutes = minutes - old_minutes;
39 if (diff_minutes >= 0) {
40 datetime_set_minute(&incr, diff_minutes);
41 }
42 else {
44 datetime_set_minute(&incr, -diff_minutes);
45 }
46
47 return datetime_increment(dt, &incr);
48}
49
50/*!
51 * \brief
52 *
53 * Return <b>datetime_change_timezone</b> (dt, 0);
54 *
55 * \param dt
56 * \return int
57 */
58
59int datetime_change_to_utc(DateTime *dt)
60{
61 return datetime_change_timezone(dt, 0);
62}
63
64/*!
65 * \brief
66 *
67 * tz = abs(tz)
68 * *hour = tz/60
69 * *minute = tz%60
70 * Note: hour,minute are non-negative. Must look at sign of tz itself to see if
71 * the tz is negative offset or not. This routine would be used to format tz for
72 * output. For example if tz=-350 this would be hour=5 minute=50, but negative.
73 * Output might encode this as -0550: printf ("%s%02d%02d", tz<0?"-":"",
74 * hour, minute)
75 *
76 * \param tz
77 * \param hours
78 * \param minutes
79 * \return void
80 */
81
82void datetime_decompose_timezone(int tz, int *hours, int *minutes)
83{
84 if (tz < 0)
85 tz = -tz;
86
87 *hours = tz / 60;
88 *minutes = tz % 60;
89}
int datetime_error(int code, char *msg)
record 'code' and 'msg' as error code/msg (in static variables) code==0 will clear the error (ie set ...
int datetime_increment(DateTime *src, DateTime *incr)
This function changes the 'src' date/time data based on the 'incr' The type (mode/from/to) of the 'sr...
Definition incr1.c:68
void datetime_invert_sign(DateTime *dt)
Definition sign.c:76
int datetime_set_type(DateTime *dt, int mode, int from, int to, int fracsec)
Definition type.c:36
int datetime_is_valid_timezone(int minutes)
Returns: 1 OK: -720 <= minutes <= 780 (720 = 12 hours; 780 = 13 hours) 0 NOT OK.
Definition tz1.c:106
int datetime_get_timezone(const DateTime *dt, int *minutes)
returns 0 on success
Definition tz1.c:46
int datetime_change_to_utc(DateTime *dt)
Return datetime_change_timezone (dt, 0);.
Definition tz2.c:59
int datetime_change_timezone(DateTime *dt, int minutes)
if dt has a timezone, increment dt by minutes-dt.tz MINUTES and set dt.tz = minutes Returns: 0 OK dat...
Definition tz2.c:21
void datetime_decompose_timezone(int tz, int *hours, int *minutes)
tz = abs(tz) *hour = tz/60 *minute = tz%60 Note: hour,minute are non-negative. Must look at sign of t...
Definition tz2.c:82
int datetime_set_minute(DateTime *dt, int minute)
returns 0 on success or negative value on error
Definition values.c:424