date.c

   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 *tm)
 201 {
 202         if (month > 0 && month < 13 && day > 0 && day < 32) {
 203                 if (year == -1) {
 204                         tm->tm_mon = month-1;
 205                         tm->tm_mday = day;
 206                         return 1;
 207                 }
 208                 if (year >= 1970 && year < 2100) {
 209                         year -= 1900;
 210                 } else if (year > 70 && year < 100) {
 211                         /* ok */
 212                 } else if (year < 38) {
 213                         year += 100;
 214                 } else
 215                         return 0;
 216
 217                 tm->tm_mon = month-1;
 218                 tm->tm_mday = day;
 219                 tm->tm_year = year;
 220                 return 1;
 221         }
 222         return 0;
 223 }
 224
 225 static int match_multi_number(unsigned long num, char c, const char *date, char *end, struct tm *tm)
 226 {
 227         long num2, num3;
 228
 229         num2 = strtol(end+1, &end, 10);
 230         num3 = -1;
 231         if (*end == c && isdigit(end[1]))
 232                 num3 = strtol(end+1, &end, 10);
 233
 234         /* Time? Date? */
 235         switch (c) {
 236         case ':':
 237                 if (num3 < 0)
 238                         num3 = 0;
 239                 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
 240                         tm->tm_hour = num;
 241                         tm->tm_min = num2;
 242                         tm->tm_sec = num3;
 243                         break;
 244                 }
 245                 return 0;
 246
 247         case '-':
 248         case '/':
 249                 if (num > 70) {
 250                         /* yyyy-mm-dd? */
 251                         if (is_date(num, num2, num3, tm))
 252                                 break;
 253                         /* yyyy-dd-mm? */
 254                         if (is_date(num, num3, num2, tm))
 255                                 break;
 256                 }
 257                 /* mm/dd/yy ? */
 258                 if (is_date(num3, num, num2, tm))
 259                         break;
 260                 /* dd/mm/yy ? */
 261                 if (is_date(num3, num2, num, tm))
 262                         break;
 263                 return 0;
 264         }
 265         return end - date;
 266 }
 267
 268 /*
 269  * We've seen a digit. Time? Year? Date?
 270  */
 271 static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt)
 272 {
 273         int n;
 274         char *end;
 275         unsigned long num;
 276
 277         num = strtoul(date, &end, 10);
 278
 279         /*
 280          * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
 281          */
 282         if (num > 946684800) {
 283                 time_t time = num;
 284                 if (gmtime_r(&time, tm)) {
 285                         *tm_gmt = 1;
 286                         return end - date;
 287                 }
 288         }
 289
 290         /*
 291          * Check for special formats: num[:-/]num[same]num
 292          */
 293         switch (*end) {
 294         case ':':
 295         case '/':
 296         case '-':
 297                 if (isdigit(end[1])) {
 298                         int match = match_multi_number(num, *end, date, end, tm);
 299                         if (match)
 300                                 return match;
 301                 }
 302         }
 303
 304         /*
 305          * None of the special formats? Try to guess what
 306          * the number meant. We use the number of digits
 307          * to make a more educated guess..
 308          */
 309         n = 0;
 310         do {
 311                 n++;
 312         } while (isdigit(date[n]));
 313
 314         /* Four-digit year or a timezone? */
 315         if (n == 4) {
 316                 if (num <= 1200 && *offset == -1) {
 317                         unsigned int minutes = num % 100;
 318                         unsigned int hours = num / 100;
 319                         *offset = hours*60 + minutes;
 320                 } else if (num > 1900 && num < 2100)
 321                         tm->tm_year = num - 1900;
 322                 return n;
 323         }
 324
 325         /*
 326          * NOTE! We will give precedence to day-of-month over month or
 327          * year numbers in the 1-12 range. So 05 is always "mday 5",
 328          * unless we already have a mday..
 329          *
 330          * IOW, 01 Apr 05 parses as "April 1st, 2005".
 331          */
 332         if (num > 0 && num < 32 && tm->tm_mday < 0) {
 333                 tm->tm_mday = num;
 334                 return n;
 335         }
 336
 337         /* Two-digit year? */
 338         if (n == 2 && tm->tm_year < 0) {
 339                 if (num < 10 && tm->tm_mday >= 0) {
 340                         tm->tm_year = num + 100;
 341                         return n;
 342                 }
 343                 if (num >= 70) {
 344                         tm->tm_year = num;
 345                         return n;
 346                 }
 347         }
 348
 349         if (num > 0 && num < 32) {
 350                 tm->tm_mday = num;
 351         } else if (num > 1900) {
 352                 tm->tm_year = num - 1900;
 353         } else if (num > 70) {
 354                 tm->tm_year = num;
 355         } else if (num > 0 && num < 13) {
 356                 tm->tm_mon = num-1;
 357         }
 358
 359         return n;
 360 }
 361
 362 static int match_tz(const char *date, int *offp)
 363 {
 364         char *end;
 365         int offset = strtoul(date+1, &end, 10);
 366         int min, hour;
 367         int n = end - date - 1;
 368
 369         min = offset % 100;
 370         hour = offset / 100;
 371
 372         /*
 373          * Don't accept any random crap.. At least 3 digits, and
 374          * a valid minute. We might want to check that the minutes
 375          * are divisible by 30 or something too.
 376          */
 377         if (min < 60 && n > 2) {
 378                 offset = hour*60+min;
 379                 if (*date == '-')
 380                         offset = -offset;
 381
 382                 *offp = offset;
 383         }
 384         return end - date;
 385 }
 386
 387 static int date_string(unsigned long date, int offset, char *buf, int len)
 388 {
 389         int sign = '+';
 390
 391         if (offset < 0) {
 392                 offset = -offset;
 393                 sign = '-';
 394         }
 395         return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
 396 }
 397
 398 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 399    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 400 int parse_date(const char *date, char *result, int maxlen)
 401 {
 402         struct tm tm;
 403         int offset, tm_gmt;
 404         time_t then;
 405
 406         memset(&tm, 0, sizeof(tm));
 407         tm.tm_year = -1;
 408         tm.tm_mon = -1;
 409         tm.tm_mday = -1;
 410         tm.tm_isdst = -1;
 411         offset = -1;
 412         tm_gmt = 0;
 413
 414         for (;;) {
 415                 int match = 0;
 416                 unsigned char c = *date;
 417
 418                 /* Stop at end of string or newline */
 419                 if (!c || c == '\n')
 420                         break;
 421
 422                 if (isalpha(c))
 423                         match = match_alpha(date, &tm, &offset);
 424                 else if (isdigit(c))
 425                         match = match_digit(date, &tm, &offset, &tm_gmt);
 426                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 427                         match = match_tz(date, &offset);
 428
 429                 if (!match) {
 430                         /* BAD CRAP */
 431                         match = 1;
 432                 }
 433
 434                 date += match;
 435         }
 436
 437         /* mktime uses local timezone */
 438         then = my_mktime(&tm);
 439         if (offset == -1)
 440                 offset = (then - mktime(&tm)) / 60;
 441
 442         if (then == -1)
 443                 return -1;
 444
 445         if (!tm_gmt)
 446                 then -= offset * 60;
 447         return date_string(then, offset, result, maxlen);
 448 }
 449
 450 void datestamp(char *buf, int bufsize)
 451 {
 452         time_t now;
 453         int offset;
 454
 455         time(&now);
 456
 457         offset = my_mktime(localtime(&now)) - now;
 458         offset /= 60;
 459
 460         date_string(now, offset, buf, bufsize);
 461 }
 462
 463 static void update_tm(struct tm *tm, unsigned long sec)
 464 {
 465         time_t n = mktime(tm) - sec;
 466         localtime_r(&n, tm);
 467 }
 468
 469 static void date_yesterday(struct tm *tm, int *num)
 470 {
 471         update_tm(tm, 24*60*60);
 472 }
 473
 474 static void date_time(struct tm *tm, int hour)
 475 {
 476         if (tm->tm_hour < hour)
 477                 date_yesterday(tm, NULL);
 478         tm->tm_hour = hour;
 479         tm->tm_min = 0;
 480         tm->tm_sec = 0;
 481 }
 482
 483 static void date_midnight(struct tm *tm, int *num)
 484 {
 485         date_time(tm, 0);
 486 }
 487
 488 static void date_noon(struct tm *tm, int *num)
 489 {
 490         date_time(tm, 12);
 491 }
 492
 493 static void date_tea(struct tm *tm, int *num)
 494 {
 495         date_time(tm, 17);
 496 }
 497
 498 static const struct special {
 499         const char *name;
 500         void (*fn)(struct tm *, int *);
 501 } special[] = {
 502         { "yesterday", date_yesterday },
 503         { "noon", date_noon },
 504         { "midnight", date_midnight },
 505         { "tea", date_tea },
 506         { NULL }
 507 };
 508
 509 static const char *number_name[] = {
 510         "zero", "one", "two", "three", "four",
 511         "five", "six", "seven", "eight", "nine", "ten",
 512 };
 513
 514 static const struct typelen {
 515         const char *type;
 516         int length;
 517 } typelen[] = {
 518         { "seconds", 1 },
 519         { "minutes", 60 },
 520         { "hours", 60*60 },
 521         { "days", 24*60*60 },
 522         { "weeks", 7*24*60*60 },
 523         { NULL }
 524 };
 525
 526 static const char *approxidate_alpha(const char *date, struct tm *tm, int *num)
 527 {
 528         const struct typelen *tl;
 529         const struct special *s;
 530         const char *end = date;
 531         int n = 1, i;
 532
 533         while (isalpha(*++end))
 534                 n++;
 535
 536         for (i = 0; i < 12; i++) {
 537                 int match = match_string(date, month_names[i]);
 538                 if (match >= 3) {
 539                         tm->tm_mon = i;
 540                         return end;
 541                 }
 542         }
 543
 544         for (s = special; s->name; s++) {
 545                 int len = strlen(s->name);
 546                 if (match_string(date, s->name) == len) {
 547                         s->fn(tm, num);
 548                         return end;
 549                 }
 550         }
 551
 552         if (!*num) {
 553                 for (i = 1; i < 11; i++) {
 554                         int len = strlen(number_name[i]);
 555                         if (match_string(date, number_name[i]) == len) {
 556                                 *num = i;
 557                                 return end;
 558                         }
 559                 }
 560                 if (match_string(date, "last") == 4)
 561                         *num = 1;
 562                 return end;
 563         }
 564
 565         tl = typelen;
 566         while (tl->type) {
 567                 int len = strlen(tl->type);
 568                 if (match_string(date, tl->type) >= len-1) {
 569                         update_tm(tm, tl->length * *num);
 570                         *num = 0;
 571                         return end;
 572                 }
 573                 tl++;
 574         }
 575
 576         for (i = 0; i < 7; i++) {
 577                 int match = match_string(date, weekday_names[i]);
 578                 if (match >= 3) {
 579                         int diff, n = *num -1;
 580                         *num = 0;
 581
 582                         diff = tm->tm_wday - i;
 583                         if (diff <= 0)
 584                                 n++;
 585                         diff += 7*n;
 586
 587                         update_tm(tm, diff * 24 * 60 * 60);
 588                         return end;
 589                 }
 590         }
 591
 592         if (match_string(date, "months") >= 5) {
 593                 int n = tm->tm_mon - *num;
 594                 *num = 0;
 595                 while (n < 0) {
 596                         n += 12;
 597                         tm->tm_year--;
 598                 }
 599                 tm->tm_mon = n;
 600                 return end;
 601         }
 602
 603         if (match_string(date, "years") >= 4) {
 604                 tm->tm_year -= *num;
 605                 *num = 0;
 606                 return end;
 607         }
 608
 609         return end;
 610 }
 611
 612 unsigned long approxidate(const char *date)
 613 {
 614         int number = 0;
 615         struct tm tm, now;
 616         struct timeval tv;
 617         char buffer[50];
 618
 619         if (parse_date(date, buffer, sizeof(buffer)) > 0)
 620                 return strtoul(buffer, NULL, 10);
 621
 622         gettimeofday(&tv, NULL);
 623         localtime_r(&tv.tv_sec, &tm);
 624         now = tm;
 625         for (;;) {
 626                 unsigned char c = *date;
 627                 if (!c)
 628                         break;
 629                 date++;
 630                 if (isdigit(c)) {
 631                         char *end;
 632                         number = strtoul(date-1, &end, 10);
 633                         date = end;
 634                         continue;
 635                 }
 636                 if (isalpha(c))
 637                         date = approxidate_alpha(date-1, &tm, &number);
 638         }
 639         if (number > 0 && number < 32)
 640                 tm.tm_mday = number;
 641         if (tm.tm_mon > now.tm_mon && tm.tm_year == now.tm_year)
 642                 tm.tm_year--;
 643         return mktime(&tm);
 644 }