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Document git-clone --reference
[git/gitweb.git] / date.c
blob034d7228bfefff9ba94ed3fd19fe751f924d7a55
1 /*
2 * GIT - The information manager from hell
3 *
4 * Copyright (C) Linus Torvalds, 2005
5 */
6
7 #include <time.h>
8 #include <sys/time.h>
9
10 #include "cache.h"
11
12 static time_t my_mktime(struct tm *tm)
13 {
14 static const int mdays[] = {
15 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
16 };
17 int year = tm->tm_year - 70;
18 int month = tm->tm_mon;
19 int day = tm->tm_mday;
20
21 if (year < 0 || year > 129) /* algo only works for 1970-2099 */
22 return -1;
23 if (month < 0 || month > 11) /* array bounds */
24 return -1;
25 if (month < 2 || (year + 2) % 4)
26 day--;
27 return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24*60*60UL +
28 tm->tm_hour * 60*60 + tm->tm_min * 60 + tm->tm_sec;
29 }
30
31 static const char *month_names[] = {
32 "January", "February", "March", "April", "May", "June",
33 "July", "August", "September", "October", "November", "December"
34 };
35
36 static const char *weekday_names[] = {
37 "Sundays", "Mondays", "Tuesdays", "Wednesdays", "Thursdays", "Fridays", "Saturdays"
38 };
39
40 /*
41 * The "tz" thing is passed in as this strange "decimal parse of tz"
42 * thing, which means that tz -0100 is passed in as the integer -100,
43 * even though it means "sixty minutes off"
44 */
45 const char *show_date(unsigned long time, int tz)
46 {
47 struct tm *tm;
48 time_t t;
49 static char timebuf[200];
50 int minutes;
51
52 minutes = tz < 0 ? -tz : tz;
53 minutes = (minutes / 100)*60 + (minutes % 100);
54 minutes = tz < 0 ? -minutes : minutes;
55 t = time + minutes * 60;
56 tm = gmtime(&t);
57 if (!tm)
58 return NULL;
59 sprintf(timebuf, "%.3s %.3s %d %02d:%02d:%02d %d %+05d",
60 weekday_names[tm->tm_wday],
61 month_names[tm->tm_mon],
62 tm->tm_mday,
63 tm->tm_hour, tm->tm_min, tm->tm_sec,
64 tm->tm_year + 1900, tz);
65 return timebuf;
66 }
67
68 /*
69 * Check these. And note how it doesn't do the summer-time conversion.
70 *
71 * In my world, it's always summer, and things are probably a bit off
72 * in other ways too.
73 */
74 static const struct {
75 const char *name;
76 int offset;
77 int dst;
78 } timezone_names[] = {
79 { "IDLW", -12, 0, }, /* International Date Line West */
80 { "NT", -11, 0, }, /* Nome */
81 { "CAT", -10, 0, }, /* Central Alaska */
82 { "HST", -10, 0, }, /* Hawaii Standard */
83 { "HDT", -10, 1, }, /* Hawaii Daylight */
84 { "YST", -9, 0, }, /* Yukon Standard */
85 { "YDT", -9, 1, }, /* Yukon Daylight */
86 { "PST", -8, 0, }, /* Pacific Standard */
87 { "PDT", -8, 1, }, /* Pacific Daylight */
88 { "MST", -7, 0, }, /* Mountain Standard */
89 { "MDT", -7, 1, }, /* Mountain Daylight */
90 { "CST", -6, 0, }, /* Central Standard */
91 { "CDT", -6, 1, }, /* Central Daylight */
92 { "EST", -5, 0, }, /* Eastern Standard */
93 { "EDT", -5, 1, }, /* Eastern Daylight */
94 { "AST", -3, 0, }, /* Atlantic Standard */
95 { "ADT", -3, 1, }, /* Atlantic Daylight */
96 { "WAT", -1, 0, }, /* West Africa */
97
98 { "GMT", 0, 0, }, /* Greenwich Mean */
99 { "UTC", 0, 0, }, /* Universal (Coordinated) */
100
101 { "WET", 0, 0, }, /* Western European */
102 { "BST", 0, 1, }, /* British Summer */
103 { "CET", +1, 0, }, /* Central European */
104 { "MET", +1, 0, }, /* Middle European */
105 { "MEWT", +1, 0, }, /* Middle European Winter */
106 { "MEST", +1, 1, }, /* Middle European Summer */
107 { "CEST", +1, 1, }, /* Central European Summer */
108 { "MESZ", +1, 1, }, /* Middle European Summer */
109 { "FWT", +1, 0, }, /* French Winter */
110 { "FST", +1, 1, }, /* French Summer */
111 { "EET", +2, 0, }, /* Eastern Europe, USSR Zone 1 */
112 { "EEST", +2, 1, }, /* Eastern European Daylight */
113 { "WAST", +7, 0, }, /* West Australian Standard */
114 { "WADT", +7, 1, }, /* West Australian Daylight */
115 { "CCT", +8, 0, }, /* China Coast, USSR Zone 7 */
116 { "JST", +9, 0, }, /* Japan Standard, USSR Zone 8 */
117 { "EAST", +10, 0, }, /* Eastern Australian Standard */
118 { "EADT", +10, 1, }, /* Eastern Australian Daylight */
119 { "GST", +10, 0, }, /* Guam Standard, USSR Zone 9 */
120 { "NZT", +11, 0, }, /* New Zealand */
121 { "NZST", +11, 0, }, /* New Zealand Standard */
122 { "NZDT", +11, 1, }, /* New Zealand Daylight */
123 { "IDLE", +12, 0, }, /* International Date Line East */
124 };
125
126 static int match_string(const char *date, const char *str)
127 {
128 int i = 0;
129
130 for (i = 0; *date; date++, str++, i++) {
131 if (*date == *str)
132 continue;
133 if (toupper(*date) == toupper(*str))
134 continue;
135 if (!isalnum(*date))
136 break;
137 return 0;
138 }
139 return i;
140 }
141
142 static int skip_alpha(const char *date)
143 {
144 int i = 0;
145 do {
146 i++;
147 } while (isalpha(date[i]));
148 return i;
149 }
150
151 /*
152 * Parse month, weekday, or timezone name
153 */
154 static int match_alpha(const char *date, struct tm *tm, int *offset)
155 {
156 int i;
157
158 for (i = 0; i < 12; i++) {
159 int match = match_string(date, month_names[i]);
160 if (match >= 3) {
161 tm->tm_mon = i;
162 return match;
163 }
164 }
165
166 for (i = 0; i < 7; i++) {
167 int match = match_string(date, weekday_names[i]);
168 if (match >= 3) {
169 tm->tm_wday = i;
170 return match;
171 }
172 }
173
174 for (i = 0; i < ARRAY_SIZE(timezone_names); i++) {
175 int match = match_string(date, timezone_names[i].name);
176 if (match >= 3) {
177 int off = timezone_names[i].offset;
178
179 /* This is bogus, but we like summer */
180 off += timezone_names[i].dst;
181
182 /* Only use the tz name offset if we don't have anything better */
183 if (*offset == -1)
184 *offset = 60*off;
185
186 return match;
187 }
188 }
189
190 if (match_string(date, "PM") == 2) {
191 if (tm->tm_hour > 0 && tm->tm_hour < 12)
192 tm->tm_hour += 12;
193 return 2;
194 }
195
196 /* BAD CRAP */
197 return skip_alpha(date);
198 }
199
200 static int is_date(int year, int month, int day, struct tm *now_tm, time_t now, struct tm *tm)
201 {
202 if (month > 0 && month < 13 && day > 0 && day < 32) {
203 struct tm check = *tm;
204 struct tm *r = (now_tm ? &check : tm);
205 time_t specified;
206
207 r->tm_mon = month - 1;
208 r->tm_mday = day;
209 if (year == -1) {
210 if (!now_tm)
211 return 1;
212 r->tm_year = now_tm->tm_year;
213 }
214 else if (year >= 1970 && year < 2100)
215 r->tm_year = year - 1900;
216 else if (year > 70 && year < 100)
217 r->tm_year = year;
218 else if (year < 38)
219 r->tm_year = year + 100;
220 else
221 return 0;
222 if (!now_tm)
223 return 1;
224
225 specified = my_mktime(r);
226
227 /* Be it commit time or author time, it does not make
228 * sense to specify timestamp way into the future. Make
229 * sure it is not later than ten days from now...
230 */
231 if (now + 10*24*3600 < specified)
232 return 0;
233 tm->tm_mon = r->tm_mon;
234 tm->tm_mday = r->tm_mday;
235 if (year != -1)
236 tm->tm_year = r->tm_year;
237 return 1;
238 }
239 return 0;
240 }
241
242 static int match_multi_number(unsigned long num, char c, const char *date, char *end, struct tm *tm)
243 {
244 time_t now;
245 struct tm now_tm;
246 struct tm *refuse_future;
247 long num2, num3;
248
249 num2 = strtol(end+1, &end, 10);
250 num3 = -1;
251 if (*end == c && isdigit(end[1]))
252 num3 = strtol(end+1, &end, 10);
253
254 /* Time? Date? */
255 switch (c) {
256 case ':':
257 if (num3 < 0)
258 num3 = 0;
259 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
260 tm->tm_hour = num;
261 tm->tm_min = num2;
262 tm->tm_sec = num3;
263 break;
264 }
265 return 0;
266
267 case '-':
268 case '/':
269 case '.':
270 now = time(NULL);
271 refuse_future = NULL;
272 if (gmtime_r(&now, &now_tm))
273 refuse_future = &now_tm;
274
275 if (num > 70) {
276 /* yyyy-mm-dd? */
277 if (is_date(num, num2, num3, refuse_future, now, tm))
278 break;
279 /* yyyy-dd-mm? */
280 if (is_date(num, num3, num2, refuse_future, now, tm))
281 break;
282 }
283 /* Our eastern European friends say dd.mm.yy[yy]
284 * is the norm there, so giving precedence to
285 * mm/dd/yy[yy] form only when separator is not '.'
286 */
287 if (c != '.' &&
288 is_date(num3, num, num2, refuse_future, now, tm))
289 break;
290 /* European dd.mm.yy[yy] or funny US dd/mm/yy[yy] */
291 if (is_date(num3, num2, num, refuse_future, now, tm))
292 break;
293 /* Funny European mm.dd.yy */
294 if (c == '.' &&
295 is_date(num3, num, num2, refuse_future, now, tm))
296 break;
297 return 0;
298 }
299 return end - date;
300 }
301
302 /*
303 * We've seen a digit. Time? Year? Date?
304 */
305 static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt)
306 {
307 int n;
308 char *end;
309 unsigned long num;
310
311 num = strtoul(date, &end, 10);
312
313 /*
314 * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
315 */
316 if (num > 946684800) {
317 time_t time = num;
318 if (gmtime_r(&time, tm)) {
319 *tm_gmt = 1;
320 return end - date;
321 }
322 }
323
324 /*
325 * Check for special formats: num[-.:/]num[same]num
326 */
327 switch (*end) {
328 case ':':
329 case '.':
330 case '/':
331 case '-':
332 if (isdigit(end[1])) {
333 int match = match_multi_number(num, *end, date, end, tm);
334 if (match)
335 return match;
336 }
337 }
338
339 /*
340 * None of the special formats? Try to guess what
341 * the number meant. We use the number of digits
342 * to make a more educated guess..
343 */
344 n = 0;
345 do {
346 n++;
347 } while (isdigit(date[n]));
348
349 /* Four-digit year or a timezone? */
350 if (n == 4) {
351 if (num <= 1200 && *offset == -1) {
352 unsigned int minutes = num % 100;
353 unsigned int hours = num / 100;
354 *offset = hours*60 + minutes;
355 } else if (num > 1900 && num < 2100)
356 tm->tm_year = num - 1900;
357 return n;
358 }
359
360 /*
361 * NOTE! We will give precedence to day-of-month over month or
362 * year numbers in the 1-12 range. So 05 is always "mday 5",
363 * unless we already have a mday..
364 *
365 * IOW, 01 Apr 05 parses as "April 1st, 2005".
366 */
367 if (num > 0 && num < 32 && tm->tm_mday < 0) {
368 tm->tm_mday = num;
369 return n;
370 }
371
372 /* Two-digit year? */
373 if (n == 2 && tm->tm_year < 0) {
374 if (num < 10 && tm->tm_mday >= 0) {
375 tm->tm_year = num + 100;
376 return n;
377 }
378 if (num >= 70) {
379 tm->tm_year = num;
380 return n;
381 }
382 }
383
384 if (num > 0 && num < 32) {
385 tm->tm_mday = num;
386 } else if (num > 1900) {
387 tm->tm_year = num - 1900;
388 } else if (num > 70) {
389 tm->tm_year = num;
390 } else if (num > 0 && num < 13) {
391 tm->tm_mon = num-1;
392 }
393
394 return n;
395 }
396
397 static int match_tz(const char *date, int *offp)
398 {
399 char *end;
400 int offset = strtoul(date+1, &end, 10);
401 int min, hour;
402 int n = end - date - 1;
403
404 min = offset % 100;
405 hour = offset / 100;
406
407 /*
408 * Don't accept any random crap.. At least 3 digits, and
409 * a valid minute. We might want to check that the minutes
410 * are divisible by 30 or something too.
411 */
412 if (min < 60 && n > 2) {
413 offset = hour*60+min;
414 if (*date == '-')
415 offset = -offset;
416
417 *offp = offset;
418 }
419 return end - date;
420 }
421
422 static int date_string(unsigned long date, int offset, char *buf, int len)
423 {
424 int sign = '+';
425
426 if (offset < 0) {
427 offset = -offset;
428 sign = '-';
429 }
430 return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
431 }
432
433 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
434 (i.e. English) day/month names, and it doesn't work correctly with %z. */
435 int parse_date(const char *date, char *result, int maxlen)
436 {
437 struct tm tm;
438 int offset, tm_gmt;
439 time_t then;
440
441 memset(&tm, 0, sizeof(tm));
442 tm.tm_year = -1;
443 tm.tm_mon = -1;
444 tm.tm_mday = -1;
445 tm.tm_isdst = -1;
446 offset = -1;
447 tm_gmt = 0;
448
449 for (;;) {
450 int match = 0;
451 unsigned char c = *date;
452
453 /* Stop at end of string or newline */
454 if (!c || c == '\n')
455 break;
456
457 if (isalpha(c))
458 match = match_alpha(date, &tm, &offset);
459 else if (isdigit(c))
460 match = match_digit(date, &tm, &offset, &tm_gmt);
461 else if ((c == '-' || c == '+') && isdigit(date[1]))
462 match = match_tz(date, &offset);
463
464 if (!match) {
465 /* BAD CRAP */
466 match = 1;
467 }
468
469 date += match;
470 }
471
472 /* mktime uses local timezone */
473 then = my_mktime(&tm);
474 if (offset == -1)
475 offset = (then - mktime(&tm)) / 60;
476
477 if (then == -1)
478 return -1;
479
480 if (!tm_gmt)
481 then -= offset * 60;
482 return date_string(then, offset, result, maxlen);
483 }
484
485 void datestamp(char *buf, int bufsize)
486 {
487 time_t now;
488 int offset;
489
490 time(&now);
491
492 offset = my_mktime(localtime(&now)) - now;
493 offset /= 60;
494
495 date_string(now, offset, buf, bufsize);
496 }
497
498 static void update_tm(struct tm *tm, unsigned long sec)
499 {
500 time_t n = mktime(tm) - sec;
501 localtime_r(&n, tm);
502 }
503
504 static void date_yesterday(struct tm *tm, int *num)
505 {
506 update_tm(tm, 24*60*60);
507 }
508
509 static void date_time(struct tm *tm, int hour)
510 {
511 if (tm->tm_hour < hour)
512 date_yesterday(tm, NULL);
513 tm->tm_hour = hour;
514 tm->tm_min = 0;
515 tm->tm_sec = 0;
516 }
517
518 static void date_midnight(struct tm *tm, int *num)
519 {
520 date_time(tm, 0);
521 }
522
523 static void date_noon(struct tm *tm, int *num)
524 {
525 date_time(tm, 12);
526 }
527
528 static void date_tea(struct tm *tm, int *num)
529 {
530 date_time(tm, 17);
531 }
532
533 static const struct special {
534 const char *name;
535 void (*fn)(struct tm *, int *);
536 } special[] = {
537 { "yesterday", date_yesterday },
538 { "noon", date_noon },
539 { "midnight", date_midnight },
540 { "tea", date_tea },
541 { NULL }
542 };
543
544 static const char *number_name[] = {
545 "zero", "one", "two", "three", "four",
546 "five", "six", "seven", "eight", "nine", "ten",
547 };
548
549 static const struct typelen {
550 const char *type;
551 int length;
552 } typelen[] = {
553 { "seconds", 1 },
554 { "minutes", 60 },
555 { "hours", 60*60 },
556 { "days", 24*60*60 },
557 { "weeks", 7*24*60*60 },
558 { NULL }
559 };
560
561 static const char *approxidate_alpha(const char *date, struct tm *tm, int *num)
562 {
563 const struct typelen *tl;
564 const struct special *s;
565 const char *end = date;
566 int n = 1, i;
567
568 while (isalpha(*++end))
569 n++;
570
571 for (i = 0; i < 12; i++) {
572 int match = match_string(date, month_names[i]);
573 if (match >= 3) {
574 tm->tm_mon = i;
575 return end;
576 }
577 }
578
579 for (s = special; s->name; s++) {
580 int len = strlen(s->name);
581 if (match_string(date, s->name) == len) {
582 s->fn(tm, num);
583 return end;
584 }
585 }
586
587 if (!*num) {
588 for (i = 1; i < 11; i++) {
589 int len = strlen(number_name[i]);
590 if (match_string(date, number_name[i]) == len) {
591 *num = i;
592 return end;
593 }
594 }
595 if (match_string(date, "last") == 4)
596 *num = 1;
597 return end;
598 }
599
600 tl = typelen;
601 while (tl->type) {
602 int len = strlen(tl->type);
603 if (match_string(date, tl->type) >= len-1) {
604 update_tm(tm, tl->length * *num);
605 *num = 0;
606 return end;
607 }
608 tl++;
609 }
610
611 for (i = 0; i < 7; i++) {
612 int match = match_string(date, weekday_names[i]);
613 if (match >= 3) {
614 int diff, n = *num -1;
615 *num = 0;
616
617 diff = tm->tm_wday - i;
618 if (diff <= 0)
619 n++;
620 diff += 7*n;
621
622 update_tm(tm, diff * 24 * 60 * 60);
623 return end;
624 }
625 }
626
627 if (match_string(date, "months") >= 5) {
628 int n = tm->tm_mon - *num;
629 *num = 0;
630 while (n < 0) {
631 n += 12;
632 tm->tm_year--;
633 }
634 tm->tm_mon = n;
635 return end;
636 }
637
638 if (match_string(date, "years") >= 4) {
639 tm->tm_year -= *num;
640 *num = 0;
641 return end;
642 }
643
644 return end;
645 }
646
647 unsigned long approxidate(const char *date)
648 {
649 int number = 0;
650 struct tm tm, now;
651 struct timeval tv;
652 char buffer[50];
653
654 if (parse_date(date, buffer, sizeof(buffer)) > 0)
655 return strtoul(buffer, NULL, 10);
656
657 gettimeofday(&tv, NULL);
658 localtime_r(&tv.tv_sec, &tm);
659 now = tm;
660 for (;;) {
661 unsigned char c = *date;
662 if (!c)
663 break;
664 date++;
665 if (isdigit(c)) {
666 char *end;
667 number = strtoul(date-1, &end, 10);
668 date = end;
669 continue;
670 }
671 if (isalpha(c))
672 date = approxidate_alpha(date-1, &tm, &number);
673 }
674 if (number > 0 && number < 32)
675 tm.tm_mday = number;
676 if (tm.tm_mon > now.tm_mon && tm.tm_year == now.tm_year)
677 tm.tm_year--;
678 return mktime(&tm);
679 }
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