date.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <ctype.h>
  11 #include <time.h>
  12
  13 static time_t my_mktime(struct tm *tm)
  14 {
  15         static const int mdays[] = {
  16             0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  17         };
  18         int year = tm->tm_year - 70;
  19         int month = tm->tm_mon;
  20         int day = tm->tm_mday;
  21
  22         if (year < 0 || year > 129) /* algo only works for 1970-2099 */
  23                 return -1;
  24         if (month < 0 || month > 11) /* array bounds */
  25                 return -1;
  26         if (month < 2 || (year + 2) % 4)
  27                 day--;
  28         return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24*60*60UL +
  29                 tm->tm_hour * 60*60 + tm->tm_min * 60 + tm->tm_sec;
  30 }
  31
  32 static const char *month_names[] = {
  33         "January", "February", "March", "April", "May", "June",
  34         "July", "August", "September", "October", "November", "December"
  35 };
  36
  37 static const char *weekday_names[] = {
  38         "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
  39 };
  40
  41 /*
  42  * Check these. And note how it doesn't do the summer-time conversion.
  43  *
  44  * In my world, it's always summer, and things are probably a bit off
  45  * in other ways too.
  46  */
  47 static const struct {
  48         const char *name;
  49         int offset;
  50         int dst;
  51 } timezone_names[] = {
  52         { "IDLW", -12, 0, },    /* International Date Line West */
  53         { "NT",   -11, 0, },    /* Nome */
  54         { "CAT",  -10, 0, },    /* Central Alaska */
  55         { "HST",  -10, 0, },    /* Hawaii Standard */
  56         { "HDT",  -10, 1, },    /* Hawaii Daylight */
  57         { "YST",   -9, 0, },    /* Yukon Standard */
  58         { "YDT",   -9, 1, },    /* Yukon Daylight */
  59         { "PST",   -8, 0, },    /* Pacific Standard */
  60         { "PDT",   -8, 1, },    /* Pacific Daylight */
  61         { "MST",   -7, 0, },    /* Mountain Standard */
  62         { "MDT",   -7, 1, },    /* Mountain Daylight */
  63         { "CST",   -6, 0, },    /* Central Standard */
  64         { "CDT",   -6, 1, },    /* Central Daylight */
  65         { "EST",   -5, 0, },    /* Eastern Standard */
  66         { "EDT",   -5, 1, },    /* Eastern Daylight */
  67         { "AST",   -3, 0, },    /* Atlantic Standard */
  68         { "ADT",   -3, 1, },    /* Atlantic Daylight */
  69         { "WAT",   -1, 0, },    /* West Africa */
  70
  71         { "GMT",    0, 0, },    /* Greenwich Mean */
  72         { "UTC",    0, 0, },    /* Universal (Coordinated) */
  73
  74         { "WET",    0, 0, },    /* Western European */
  75         { "BST",    0, 1, },    /* British Summer */
  76         { "CET",   +1, 0, },    /* Central European */
  77         { "MET",   +1, 0, },    /* Middle European */
  78         { "MEWT",  +1, 0, },    /* Middle European Winter */
  79         { "MEST",  +1, 1, },    /* Middle European Summer */
  80         { "CEST",  +1, 1, },    /* Central European Summer */
  81         { "MESZ",  +1, 1, },    /* Middle European Summer */
  82         { "FWT",   +1, 0, },    /* French Winter */
  83         { "FST",   +1, 1, },    /* French Summer */
  84         { "EET",   +2, 0, },    /* Eastern Europe, USSR Zone 1 */
  85         { "EEST",  +2, 1, },    /* Eastern European Daylight */
  86         { "WAST",  +7, 0, },    /* West Australian Standard */
  87         { "WADT",  +7, 1, },    /* West Australian Daylight */
  88         { "CCT",   +8, 0, },    /* China Coast, USSR Zone 7 */
  89         { "JST",   +9, 0, },    /* Japan Standard, USSR Zone 8 */
  90         { "EAST", +10, 0, },    /* Eastern Australian Standard */
  91         { "EADT", +10, 1, },    /* Eastern Australian Daylight */
  92         { "GST",  +10, 0, },    /* Guam Standard, USSR Zone 9 */
  93         { "NZT",  +11, 0, },    /* New Zealand */
  94         { "NZST", +11, 0, },    /* New Zealand Standard */
  95         { "NZDT", +11, 1, },    /* New Zealand Daylight */
  96         { "IDLE", +12, 0, },    /* International Date Line East */
  97 };
  98
  99 #define NR_TZ (sizeof(timezone_names) / sizeof(timezone_names[0]))
 100
 101 static int match_string(const char *date, const char *str)
 102 {
 103         int i = 0;
 104
 105         for (i = 0; *date; date++, str++, i++) {
 106                 if (*date == *str)
 107                         continue;
 108                 if (toupper(*date) == toupper(*str))
 109                         continue;
 110                 if (!isalnum(*date))
 111                         break;
 112                 return 0;
 113         }
 114         return i;
 115 }
 116
 117 /*
 118 * Parse month, weekday, or timezone name
 119 */
 120 static int match_alpha(const char *date, struct tm *tm, int *offset)
 121 {
 122         int i;
 123
 124         for (i = 0; i < 12; i++) {
 125                 int match = match_string(date, month_names[i]);
 126                 if (match >= 3) {
 127                         tm->tm_mon = i;
 128                         return match;
 129                 }
 130         }
 131
 132         for (i = 0; i < 7; i++) {
 133                 int match = match_string(date, weekday_names[i]);
 134                 if (match >= 3) {
 135                         tm->tm_wday = i;
 136                         return match;
 137                 }
 138         }
 139
 140         for (i = 0; i < NR_TZ; i++) {
 141                 int match = match_string(date, timezone_names[i].name);
 142                 if (match >= 3) {
 143                         int off = timezone_names[i].offset;
 144
 145                         /* This is bogus, but we like summer */
 146                         off += timezone_names[i].dst;
 147
 148                         /* Only use the tz name offset if we don't have anything better */
 149                         if (*offset == -1)
 150                                 *offset = 60*off;
 151
 152                         return match;
 153                 }
 154         }
 155
 156         /* BAD CRAP */
 157         return 0;
 158 }
 159
 160 static int is_date(int year, int month, int day, struct tm *tm)
 161 {
 162         if (month > 0 && month < 13 && day > 0 && day < 32) {
 163                 if (year == -1) {
 164                         tm->tm_mon = month-1;
 165                         tm->tm_mday = day;
 166                         return 1;
 167                 }
 168                 if (year >= 1970 && year < 2100) {
 169                         year -= 1900;
 170                 } else if (year > 70 && year < 100) {
 171                         /* ok */
 172                 } else if (year < 38) {
 173                         year += 100;
 174                 } else
 175                         return 0;
 176
 177                 tm->tm_mon = month-1;
 178                 tm->tm_mday = day;
 179                 tm->tm_year = year;
 180                 return 1;
 181         }
 182         return 0;
 183 }
 184
 185 static int match_multi_number(unsigned long num, char c, char *date, char *end, struct tm *tm)
 186 {
 187         long num2, num3;
 188
 189         num2 = strtol(end+1, &end, 10);
 190         num3 = -1;
 191         if (*end == c && isdigit(end[1]))
 192                 num3 = strtol(end+1, &end, 10);
 193
 194         /* Time? Date? */
 195         switch (c) {
 196         case ':':
 197                 if (num3 < 0)
 198                         num3 = 0;
 199                 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
 200                         tm->tm_hour = num;
 201                         tm->tm_min = num2;
 202                         tm->tm_sec = num3;
 203                         break;
 204                 }
 205                 return 0;
 206
 207         case '-':
 208         case '/':
 209                 if (num > 70) {
 210                         /* yyyy-mm-dd? */
 211                         if (is_date(num, num2, num3, tm))
 212                                 break;
 213                         /* yyyy-dd-mm? */
 214                         if (is_date(num, num3, num2, tm))
 215                                 break;
 216                 }
 217                 /* mm/dd/yy ? */
 218                 if (is_date(num3, num2, num, tm))
 219                         break;
 220                 /* dd/mm/yy ? */
 221                 if (is_date(num3, num, num2, tm))
 222                         break;
 223                 return 0;
 224         }
 225         return end - date;
 226 }
 227
 228 /*
 229  * We've seen a digit. Time? Year? Date?
 230  */
 231 static int match_digit(char *date, struct tm *tm, int *offset)
 232 {
 233         int n;
 234         char *end;
 235         unsigned long num;
 236
 237         num = strtoul(date, &end, 10);
 238
 239         /*
 240          * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
 241          */
 242         if (num > 946684800) {
 243                 time_t time = num;
 244                 if (gmtime_r(&time, tm))
 245                         return end - date;
 246         }
 247
 248         /*
 249          * Check for special formats: num[:-/]num[same]num
 250          */
 251         switch (*end) {
 252         case ':':
 253         case '/':
 254         case '-':
 255                 if (isdigit(end[1])) {
 256                         int match = match_multi_number(num, *end, date, end, tm);
 257                         if (match)
 258                                 return match;
 259                 }
 260         }
 261
 262         /*
 263          * None of the special formats? Try to guess what
 264          * the number meant. We use the number of digits
 265          * to make a more educated guess..
 266          */
 267         n = 0;
 268         do {
 269                 n++;
 270         } while (isdigit(date[n]));
 271
 272         /* Four-digit year or a timezone? */
 273         if (n == 4) {
 274                 if (num <= 1200 && *offset == -1) {
 275                         unsigned int minutes = num % 100;
 276                         unsigned int hours = num / 100;
 277                         *offset = hours*60 + minutes;
 278                 } else if (num > 1900 && num < 2100)
 279                         tm->tm_year = num - 1900;
 280                 return n;
 281         }
 282
 283         /*
 284          * NOTE! We will give precedence to day-of-month over month or
 285          * year numebers in the 1-12 range. So 05 is always "mday 5",
 286          * unless we already have a mday..
 287          *
 288          * IOW, 01 Apr 05 parses as "April 1st, 2005".
 289          */
 290         if (num > 0 && num < 32 && tm->tm_mday < 0) {
 291                 tm->tm_mday = num;
 292                 return n;
 293         }
 294
 295         /* Two-digit year? */
 296         if (n == 2 && tm->tm_year < 0) {
 297                 if (num < 10 && tm->tm_mday >= 0) {
 298                         tm->tm_year = num + 100;
 299                         return n;
 300                 }
 301                 if (num >= 70) {
 302                         tm->tm_year = num;
 303                         return n;
 304                 }
 305         }
 306
 307         if (num > 0 && num < 32) {
 308                 tm->tm_mday = num;
 309         } else if (num > 1900) {
 310                 tm->tm_year = num - 1900;
 311         } else if (num > 70) {
 312                 tm->tm_year = num;
 313         } else if (num > 0 && num < 13) {
 314                 tm->tm_mon = num-1;
 315         }
 316
 317         return n;
 318 }
 319
 320 static int match_tz(char *date, int *offp)
 321 {
 322         char *end;
 323         int offset = strtoul(date+1, &end, 10);
 324         int min, hour;
 325         int n = end - date - 1;
 326
 327         min = offset % 100;
 328         hour = offset / 100;
 329
 330         /*
 331          * Don't accept any random crap.. At least 3 digits, and
 332          * a valid minute. We might want to check that the minutes
 333          * are divisible by 30 or something too.
 334          */
 335         if (min >= 60 || n < 3)
 336                 return 0;
 337
 338         offset = hour*60+min;
 339         if (*date == '-')
 340                 offset = -offset;
 341
 342         *offp = offset;
 343         return end - date;
 344 }
 345
 346 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 347    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 348 void parse_date(char *date, char *result, int maxlen)
 349 {
 350         struct tm tm;
 351         int offset, sign;
 352         time_t then;
 353
 354         memset(&tm, 0, sizeof(tm));
 355         tm.tm_year = -1;
 356         tm.tm_mon = -1;
 357         tm.tm_mday = -1;
 358         tm.tm_isdst = -1;
 359         offset = -1;
 360
 361         for (;;) {
 362                 int match = 0;
 363                 unsigned char c = *date;
 364
 365                 /* Stop at end of string or newline */
 366                 if (!c || c == '\n')
 367                         break;
 368
 369                 if (isalpha(c))
 370                         match = match_alpha(date, &tm, &offset);
 371                 else if (isdigit(c))
 372                         match = match_digit(date, &tm, &offset);
 373                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 374                         match = match_tz(date, &offset);
 375
 376                 if (!match) {
 377                         /* BAD CRAP */
 378                         match = 1;
 379                 }
 380
 381                 date += match;
 382         }
 383
 384         /* mktime uses local timezone */
 385         then = my_mktime(&tm);
 386         if (offset == -1)
 387                 offset = (then - mktime(&tm)) / 60;
 388
 389         if (then == -1)
 390                 return;
 391
 392         then -= offset * 60;
 393
 394         sign = '+';
 395         if (offset < 0) {
 396                 offset = -offset;
 397                 sign = '-';
 398         }
 399
 400         snprintf(result, maxlen, "%lu %c%02d%02d", then, sign, offset/60, offset % 60);
 401 }
 402
 403 void datestamp(char *buf, int bufsize)
 404 {
 405         time_t now;
 406         int offset;
 407
 408         time(&now);
 409
 410         offset = my_mktime(localtime(&now)) - now;
 411         offset /= 60;
 412
 413         snprintf(buf, bufsize, "%lu %+05d", now, offset/60*100 + offset%60);
 414 }