aboutsummaryrefslogtreecommitdiffstats
path: root/calendar/cal-util/timeutil.c
blob: f66d851399f218ea84f0e87cbc0b54694f6e9504 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
/* Miscellaneous time-related utilities
 *
 * Copyright (C) 1998 The Free Software Foundation
 * Copyright (C) 2000 Ximian, Inc.
 *
 * Authors: Federico Mena <federico@ximian.com>
 *          Miguel de Icaza <miguel@ximian.com>
 *          Damon Chaplin <damon@ximian.com>
 */

#include <string.h>
#include <ctype.h>
#include <glib.h>
#include <ical.h>
#include "timeutil.h"



#define REFORMATION_DAY 639787  /* First day of the reformation, counted from 1 Jan 1 */
#define MISSING_DAYS 11     /* They corrected out 11 days */
#define THURSDAY 4      /* First day of reformation */
#define SATURDAY 6      /* Offset value; 1 Jan 1 was a Saturday */


/* Number of days in a month, using 0 (Jan) to 11 (Dec). For leap years,
   add 1 to February (month 1). */
static const int days_in_month[12] = {
    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};



/**************************************************************************
 * time_t manipulation functions.
 *
 * NOTE: these use the Unix timezone functions like mktime() and localtime()
 * and so should not be used in Evolution. New Evolution code should use
 * icaltimetype values rather than time_t values wherever possible.
 **************************************************************************/

static void
print_time_t (time_t t)
{
    struct tm *tm = localtime (&t);
    
    printf ("%d/%02d/%02d %02d:%02d:%02d",
        1900 + tm->tm_year, tm->tm_mon+1, tm->tm_mday,
        tm->tm_hour, tm->tm_min, tm->tm_sec);
}

/* Adds a day onto the time, using local time.
   Note that if clocks go forward due to daylight savings time, there are
   some non-existent local times, so the hour may be changed to make it a
   valid time. This also means that it may not be wise to keep calling
   time_add_day() to step through a certain period - if the hour gets changed
   to make it valid time, any further calls to time_add_day() will also return
   this hour, which may not be what you want. */
time_t
time_add_day (time_t time, int days)
{
    struct tm *tm = localtime (&time);
    time_t new_time;

    tm->tm_mday += days;
    tm->tm_isdst = -1;

    if ((new_time = mktime (tm)) == -1) {
        g_message ("time_add_day(): mktime() could not handling adding %d days with\n",
               days);
        print_time_t (time);
        printf ("\n");
        return time;
    }

    return new_time;
}

time_t
time_add_week (time_t time, int weeks)
{
    return time_add_day (time, weeks * 7);
}

time_t
time_add_month (time_t time, int months)
{
    struct tm *tm = localtime (&time);
    time_t new_time;
    int mday;

    mday = tm->tm_mday;
    
    tm->tm_mon += months;
    tm->tm_isdst = -1;
    if ((new_time = mktime (tm)) == -1) {
        g_message ("time_add_month(): mktime() could not handling adding %d months with\n",
               months);
        print_time_t (time);
        printf ("\n");
        return time;
    }
    tm = localtime (&new_time);
    if (tm->tm_mday < mday) {
        tm->tm_mon--;
        tm->tm_mday = time_days_in_month (tm->tm_year+1900, tm->tm_mon);
        return new_time = mktime (tm);
    }
    else
        return new_time;
}

time_t
time_year_begin (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mon  = 0;
    tm.tm_mday = 1;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

time_t
time_month_begin (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday = 1;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

/* Returns the start of the week. week_start_day should use the same values
   as mktime(), i.e. 0 (Sun) to 6 (Sat). */
time_t
time_week_begin (time_t t, int week_start_day)
{
    struct tm tm;
    int offset;

    tm = *localtime (&t);

    /* Calculate the current offset from the week start day. */
    offset = (tm.tm_wday + 7 - week_start_day) % 7;

    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_mday -= offset;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

/* Returns the start of the day, according to the local time. */
time_t
time_day_begin (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_isdst = -1;

    return mktime (&tm);
}

/* Returns the end of the day, according to the local time. */
time_t
time_day_end (time_t t)
{
    struct tm tm;

    tm = *localtime (&t);
    tm.tm_mday++;
    tm.tm_hour = 0;
    tm.tm_min  = 0;
    tm.tm_sec  = 0;
    tm.tm_isdst = -1;

    return mktime (&tm);
}


/**************************************************************************
 * time_t manipulation functions, using timezones in libical.
 *
 * NOTE: these are only here to make the transition to the timezone
 * functions easier. New code should use icaltimetype values rather than
 * time_t values wherever possible.
 **************************************************************************/


/* Adds or subtracts a number of days to/from the given time_t value, using
   the given timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_add_day_with_zone (time_t time, int days, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Add/subtract the number of days. */
    icaltime_adjust (&tt, days, 0, 0, 0);

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Adds or subtracts a number of weeks to/from the given time_t value, using
   the given timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_add_week_with_zone (time_t time, int weeks, icaltimezone *zone)
{
    return time_add_day_with_zone (time, weeks * 7, zone);
}


/* Adds or subtracts a number of months to/from the given time_t value, using
   the given timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_add_month_with_zone (time_t time, int months, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Add on the number of months. */
    tt.month += months;

    /* Normalize it, fixing any overflow. */
    tt = icaltime_normalize (tt);

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Returns the start of the year containing the given time_t, using the given
   timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_year_begin_with_zone (time_t time, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Set it to the start of the year. */
    tt.month  = 1;
    tt.day    = 1;
    tt.hour   = 0;
    tt.minute = 0;
    tt.second = 0;

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Returns the start of the month containing the given time_t, using the given
   timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_month_begin_with_zone (time_t time, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Set it to the start of the month. */
    tt.day    = 1;
    tt.hour   = 0;
    tt.minute = 0;
    tt.second = 0;

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Returns the start of the week containing the given time_t, using the given
   timezone. week_start_day should use the same values as mktime(),
   i.e. 0 (Sun) to 6 (Sat).
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_week_begin_with_zone (time_t time, int week_start_day, icaltimezone *zone)
{
    struct icaltimetype tt;
    int weekday, offset;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Get the weekday. */
    weekday = time_day_of_week (tt.day, tt.month - 1, tt.year);

    /* Calculate the current offset from the week start day. */
    offset = (weekday + 7 - week_start_day) % 7;

    /* Set it to the start of the month. */
    tt.day -= offset;
    tt.hour   = 0;
    tt.minute = 0;
    tt.second = 0;

    /* Normalize it, to fix any overflow. */
    tt = icaltime_normalize (tt);

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Returns the start of the day containing the given time_t, using the given
   timezone.
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_day_begin_with_zone (time_t time, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Set it to the start of the day. */
    tt.hour   = 0;
    tt.minute = 0;
    tt.second = 0;

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}


/* Returns the end of the day containing the given time_t, using the given
   timezone. (The end of the day is the start of the next day.)
   NOTE: this function is only here to make the transition to the timezone
   functions easier. New code should use icaltimetype values and
   icaltime_adjust() to add or subtract days, hours, minutes & seconds. */
time_t
time_day_end_with_zone (time_t time, icaltimezone *zone)
{
    struct icaltimetype tt;

    /* Convert to an icaltimetype. */
    tt = icaltime_from_timet_with_zone (time, FALSE, zone);

    /* Set it to the start of the next day. */
    tt.day++;
    tt.hour   = 0;
    tt.minute = 0;
    tt.second = 0;

    /* Normalize it, to fix any overflow. */
    tt = icaltime_normalize (tt);

    /* Convert back to a time_t. */
    return icaltime_as_timet_with_zone (tt, zone);
}

/**
 * time_to_gdate_with_zone:
 * @date: Destination #GDate value.
 * @time: A time value.
 * @zone: Desired timezone for destination @date, or NULL if the UTC timezone
 * is desired.
 * 
 * Converts a time_t value to a #GDate structure using the specified timezone.
 * This is analogous to g_date_set_time() but takes the timezone into account.
 **/
void
time_to_gdate_with_zone (GDate *date, time_t time, icaltimezone *zone)
{
    struct icaltimetype tt;

    g_return_if_fail (date != NULL);
    g_return_if_fail (time != -1);

    tt = icaltime_from_timet_with_zone (time, FALSE,
                        zone ? zone : icaltimezone_get_utc_timezone ());

    g_date_set_dmy (date, tt.day, tt.month, tt.year);
}


/**************************************************************************
 * General time functions.
 **************************************************************************/


/* Returns the number of days in the month. Year is the normal year, e.g. 2001.
   Month is 0 (Jan) to 11 (Dec). */
int
time_days_in_month (int year, int month)
{
    int days;

    g_return_val_if_fail (year >= 1900, 0);
    g_return_val_if_fail ((month >= 0) && (month < 12), 0);

    days = days_in_month[month];
    if (month == 1 && time_is_leap_year (year))
        days++;

    return days;
}


/* Returns the 1-based day number within the year of the specified date.
   Year is the normal year, e.g. 2001. Month is 0 to 11. */
int
time_day_of_year (int day, int month, int year)
{
    int i;

    for (i = 0; i < month; i++) {
        day += days_in_month[i];

        if (month == 1 && time_is_leap_year (year))
            day++;
    }

    return day;
}


/* Returns the day of the week for the specified date, 0 (Sun) to 6 (Sat).
   For the days that were removed on the Gregorian reformation, it returns
   Thursday. Year is the normal year, e.g. 2001. Month is 0 to 11. */
int
time_day_of_week (int day, int month, int year)
{
    int n;

    n = (year - 1) * 365 + time_leap_years_up_to (year - 1)
      + time_day_of_year (day, month, year);

    if (n < REFORMATION_DAY)
        return (n - 1 + SATURDAY) % 7;

    if (n >= (REFORMATION_DAY + MISSING_DAYS))
        return (n - 1 + SATURDAY - MISSING_DAYS) % 7;

    return THURSDAY;
}


/* Returns whether the specified year is a leap year. Year is the normal year,
   e.g. 2001. */
gboolean
time_is_leap_year (int year)
{
    if (year <= 1752)
        return !(year % 4);
    else
        return (!(year % 4) && (year % 100)) || !(year % 400);
}


/* Returns the number of leap years since year 1 up to (but not including) the
   specified year. Year is the normal year, e.g. 2001. */
int
time_leap_years_up_to (int year)
{
  /* There is normally a leap year every 4 years, except at the turn of
     centuries since 1700. But there is a leap year on centuries since 1700
     which are divisible by 400. */
  return (year / 4
      - ((year > 1700) ? (year / 100 - 17) : 0)
      + ((year > 1600) ? ((year - 1600) / 400) : 0));
}


/**
 * isodate_from_time_t:
 * @t: A time value.
 * 
 * Creates an ISO 8601 UTC representation from a time value.
 * 
 * Return value: String with the ISO 8601 representation of the UTC time.
 **/
char *
isodate_from_time_t (time_t t)
{
    struct tm *tm;
    char isotime[40];

    tm = gmtime (&t);
    strftime (isotime, sizeof (isotime)-1, "%Y%m%dT%H%M%SZ", tm);
    return g_strdup (isotime);
}

/**
 * time_from_isodate:
 * @str: Date/time value in ISO 8601 format.
 * 
 * Converts an ISO 8601 UTC time string into a time_t value.
 * 
 * Return value: Time_t corresponding to the specified ISO string.
 * Note that we only allow UTC times at present.
 **/
time_t
time_from_isodate (const char *str)
{
    struct icaltimetype tt = icaltime_null_time ();
    icaltimezone *utc_zone;
    int len, i;

    g_return_val_if_fail (str != NULL, -1);

    /* yyyymmdd[Thhmmss[Z]] */

    len = strlen (str);

    if (!(len == 8 || len == 15 || len == 16))
        return -1;

    for (i = 0; i < len; i++)
        if (!((i != 8 && i != 15 && isdigit (str[i]))
              || (i == 8 && str[i] == 'T')
              || (i == 15 && str[i] == 'Z')))
            return -1;

#define digit_at(x,y) (x[y] - '0')

    tt.year = digit_at (str, 0) * 1000
        + digit_at (str, 1) * 100
        + digit_at (str, 2) * 10
        + digit_at (str, 3);

    tt.month = digit_at (str, 4) * 10
         + digit_at (str, 5);

    tt.day = digit_at (str, 6) * 10
           + digit_at (str, 7);

    if (len > 8) {
        tt.hour = digit_at (str, 9) * 10
            + digit_at (str, 10);
        tt.minute  = digit_at (str, 11) * 10
               + digit_at (str, 12);
        tt.second  = digit_at (str, 13) * 10
               + digit_at (str, 14);
    }

    utc_zone = icaltimezone_get_utc_timezone ();

    return icaltime_as_timet_with_zone (tt, utc_zone);
}