date.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6
   7 #include <ctype.h>
   8 #include <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         "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
  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 #define NR_TZ (sizeof(timezone_names) / sizeof(timezone_names[0]))
 127
 128 static int match_string(const char *date, const char *str)
 129 {
 130         int i = 0;
 131
 132         for (i = 0; *date; date++, str++, i++) {
 133                 if (*date == *str)
 134                         continue;
 135                 if (toupper(*date) == toupper(*str))
 136                         continue;
 137                 if (!isalnum(*date))
 138                         break;
 139                 return 0;
 140         }
 141         return i;
 142 }
 143
 144 static int skip_alpha(const char *date)
 145 {
 146         int i = 0;
 147         do {
 148                 i++;
 149         } while (isalpha(date[i]));
 150         return i;
 151 }
 152
 153 /*
 154 * Parse month, weekday, or timezone name
 155 */
 156 static int match_alpha(const char *date, struct tm *tm, int *offset)
 157 {
 158         int i;
 159
 160         for (i = 0; i < 12; i++) {
 161                 int match = match_string(date, month_names[i]);
 162                 if (match >= 3) {
 163                         tm->tm_mon = i;
 164                         return match;
 165                 }
 166         }
 167
 168         for (i = 0; i < 7; i++) {
 169                 int match = match_string(date, weekday_names[i]);
 170                 if (match >= 3) {
 171                         tm->tm_wday = i;
 172                         return match;
 173                 }
 174         }
 175
 176         for (i = 0; i < NR_TZ; i++) {
 177                 int match = match_string(date, timezone_names[i].name);
 178                 if (match >= 3) {
 179                         int off = timezone_names[i].offset;
 180
 181                         /* This is bogus, but we like summer */
 182                         off += timezone_names[i].dst;
 183
 184                         /* Only use the tz name offset if we don't have anything better */
 185                         if (*offset == -1)
 186                                 *offset = 60*off;
 187
 188                         return match;
 189                 }
 190         }
 191
 192         if (match_string(date, "PM") == 2) {
 193                 if (tm->tm_hour > 0 && tm->tm_hour < 12)
 194                         tm->tm_hour += 12;
 195                 return 2;
 196         }
 197
 198         /* BAD CRAP */
 199         return skip_alpha(date);
 200 }
 201
 202 static int is_date(int year, int month, int day, struct tm *tm)
 203 {
 204         if (month > 0 && month < 13 && day > 0 && day < 32) {
 205                 if (year == -1) {
 206                         tm->tm_mon = month-1;
 207                         tm->tm_mday = day;
 208                         return 1;
 209                 }
 210                 if (year >= 1970 && year < 2100) {
 211                         year -= 1900;
 212                 } else if (year > 70 && year < 100) {
 213                         /* ok */
 214                 } else if (year < 38) {
 215                         year += 100;
 216                 } else
 217                         return 0;
 218
 219                 tm->tm_mon = month-1;
 220                 tm->tm_mday = day;
 221                 tm->tm_year = year;
 222                 return 1;
 223         }
 224         return 0;
 225 }
 226
 227 static int match_multi_number(unsigned long num, char c, const char *date, char *end, struct tm *tm)
 228 {
 229         long num2, num3;
 230
 231         num2 = strtol(end+1, &end, 10);
 232         num3 = -1;
 233         if (*end == c && isdigit(end[1]))
 234                 num3 = strtol(end+1, &end, 10);
 235
 236         /* Time? Date? */
 237         switch (c) {
 238         case ':':
 239                 if (num3 < 0)
 240                         num3 = 0;
 241                 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
 242                         tm->tm_hour = num;
 243                         tm->tm_min = num2;
 244                         tm->tm_sec = num3;
 245                         break;
 246                 }
 247                 return 0;
 248
 249         case '-':
 250         case '/':
 251                 if (num > 70) {
 252                         /* yyyy-mm-dd? */
 253                         if (is_date(num, num2, num3, tm))
 254                                 break;
 255                         /* yyyy-dd-mm? */
 256                         if (is_date(num, num3, num2, tm))
 257                                 break;
 258                 }
 259                 /* mm/dd/yy ? */
 260                 if (is_date(num3, num2, num, tm))
 261                         break;
 262                 /* dd/mm/yy ? */
 263                 if (is_date(num3, num, num2, tm))
 264                         break;
 265                 return 0;
 266         }
 267         return end - date;
 268 }
 269
 270 /*
 271  * We've seen a digit. Time? Year? Date?
 272  */
 273 static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt)
 274 {
 275         int n;
 276         char *end;
 277         unsigned long num;
 278
 279         num = strtoul(date, &end, 10);
 280
 281         /*
 282          * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
 283          */
 284         if (num > 946684800) {
 285                 time_t time = num;
 286                 if (gmtime_r(&time, tm)) {
 287                         *tm_gmt = 1;
 288                         return end - date;
 289                 }
 290         }
 291
 292         /*
 293          * Check for special formats: num[:-/]num[same]num
 294          */
 295         switch (*end) {
 296         case ':':
 297         case '/':
 298         case '-':
 299                 if (isdigit(end[1])) {
 300                         int match = match_multi_number(num, *end, date, end, tm);
 301                         if (match)
 302                                 return match;
 303                 }
 304         }
 305
 306         /*
 307          * None of the special formats? Try to guess what
 308          * the number meant. We use the number of digits
 309          * to make a more educated guess..
 310          */
 311         n = 0;
 312         do {
 313                 n++;
 314         } while (isdigit(date[n]));
 315
 316         /* Four-digit year or a timezone? */
 317         if (n == 4) {
 318                 if (num <= 1200 && *offset == -1) {
 319                         unsigned int minutes = num % 100;
 320                         unsigned int hours = num / 100;
 321                         *offset = hours*60 + minutes;
 322                 } else if (num > 1900 && num < 2100)
 323                         tm->tm_year = num - 1900;
 324                 return n;
 325         }
 326
 327         /*
 328          * NOTE! We will give precedence to day-of-month over month or
 329          * year numebers in the 1-12 range. So 05 is always "mday 5",
 330          * unless we already have a mday..
 331          *
 332          * IOW, 01 Apr 05 parses as "April 1st, 2005".
 333          */
 334         if (num > 0 && num < 32 && tm->tm_mday < 0) {
 335                 tm->tm_mday = num;
 336                 return n;
 337         }
 338
 339         /* Two-digit year? */
 340         if (n == 2 && tm->tm_year < 0) {
 341                 if (num < 10 && tm->tm_mday >= 0) {
 342                         tm->tm_year = num + 100;
 343                         return n;
 344                 }
 345                 if (num >= 70) {
 346                         tm->tm_year = num;
 347                         return n;
 348                 }
 349         }
 350
 351         if (num > 0 && num < 32) {
 352                 tm->tm_mday = num;
 353         } else if (num > 1900) {
 354                 tm->tm_year = num - 1900;
 355         } else if (num > 70) {
 356                 tm->tm_year = num;
 357         } else if (num > 0 && num < 13) {
 358                 tm->tm_mon = num-1;
 359         }
 360
 361         return n;
 362 }
 363
 364 static int match_tz(const char *date, int *offp)
 365 {
 366         char *end;
 367         int offset = strtoul(date+1, &end, 10);
 368         int min, hour;
 369         int n = end - date - 1;
 370
 371         min = offset % 100;
 372         hour = offset / 100;
 373
 374         /*
 375          * Don't accept any random crap.. At least 3 digits, and
 376          * a valid minute. We might want to check that the minutes
 377          * are divisible by 30 or something too.
 378          */
 379         if (min < 60 && n > 2) {
 380                 offset = hour*60+min;
 381                 if (*date == '-')
 382                         offset = -offset;
 383
 384                 *offp = offset;
 385         }
 386         return end - date;
 387 }
 388
 389 static int date_string(unsigned long date, int offset, char *buf, int len)
 390 {
 391         int sign = '+';
 392
 393         if (offset < 0) {
 394                 offset = -offset;
 395                 sign = '-';
 396         }
 397         return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
 398 }
 399
 400 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 401    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 402 int parse_date(const char *date, char *result, int maxlen)
 403 {
 404         struct tm tm;
 405         int offset, tm_gmt;
 406         time_t then;
 407
 408         memset(&tm, 0, sizeof(tm));
 409         tm.tm_year = -1;
 410         tm.tm_mon = -1;
 411         tm.tm_mday = -1;
 412         tm.tm_isdst = -1;
 413         offset = -1;
 414         tm_gmt = 0;
 415
 416         for (;;) {
 417                 int match = 0;
 418                 unsigned char c = *date;
 419
 420                 /* Stop at end of string or newline */
 421                 if (!c || c == '\n')
 422                         break;
 423
 424                 if (isalpha(c))
 425                         match = match_alpha(date, &tm, &offset);
 426                 else if (isdigit(c))
 427                         match = match_digit(date, &tm, &offset, &tm_gmt);
 428                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 429                         match = match_tz(date, &offset);
 430
 431                 if (!match) {
 432                         /* BAD CRAP */
 433                         match = 1;
 434                 }
 435
 436                 date += match;
 437         }
 438
 439         /* mktime uses local timezone */
 440         then = my_mktime(&tm);
 441         if (offset == -1)
 442                 offset = (then - mktime(&tm)) / 60;
 443
 444         if (then == -1)
 445                 return -1;
 446
 447         if (!tm_gmt)
 448                 then -= offset * 60;
 449         return date_string(then, offset, result, maxlen);
 450 }
 451
 452 void datestamp(char *buf, int bufsize)
 453 {
 454         time_t now;
 455         int offset;
 456
 457         time(&now);
 458
 459         offset = my_mktime(localtime(&now)) - now;
 460         offset /= 60;
 461
 462         date_string(now, offset, buf, bufsize);
 463 }