date.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6
   7 #include <time.h>
   8
   9 #include "cache.h"
  10
  11 static time_t my_mktime(struct tm *tm)
  12 {
  13         static const int mdays[] = {
  14             0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  15         };
  16         int year = tm->tm_year - 70;
  17         int month = tm->tm_mon;
  18         int day = tm->tm_mday;
  19
  20         if (year < 0 || year > 129) /* algo only works for 1970-2099 */
  21                 return -1;
  22         if (month < 0 || month > 11) /* array bounds */
  23                 return -1;
  24         if (month < 2 || (year + 2) % 4)
  25                 day--;
  26         return (year * 365 + (year + 1) / 4 + mdays[month] + day) * 24*60*60UL +
  27                 tm->tm_hour * 60*60 + tm->tm_min * 60 + tm->tm_sec;
  28 }
  29
  30 static const char *month_names[] = {
  31         "January", "February", "March", "April", "May", "June",
  32         "July", "August", "September", "October", "November", "December"
  33 };
  34
  35 static const char *weekday_names[] = {
  36         "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
  37 };
  38
  39 /*
  40  * The "tz" thing is passed in as this strange "decimal parse of tz"
  41  * thing, which means that tz -0100 is passed in as the integer -100,
  42  * even though it means "sixty minutes off"
  43  */
  44 const char *show_date(unsigned long time, int tz)
  45 {
  46         struct tm *tm;
  47         time_t t;
  48         static char timebuf[200];
  49         int minutes;
  50
  51         minutes = tz < 0 ? -tz : tz;
  52         minutes = (minutes / 100)*60 + (minutes % 100);
  53         minutes = tz < 0 ? -minutes : minutes;
  54         t = time + minutes * 60;
  55         tm = gmtime(&t);
  56         if (!tm)
  57                 return NULL;
  58         sprintf(timebuf, "%.3s %.3s %d %02d:%02d:%02d %d %+05d",
  59                 weekday_names[tm->tm_wday],
  60                 month_names[tm->tm_mon],
  61                 tm->tm_mday,
  62                 tm->tm_hour, tm->tm_min, tm->tm_sec,
  63                 tm->tm_year + 1900, tz);
  64         return timebuf;
  65 }
  66
  67 /*
  68  * Check these. And note how it doesn't do the summer-time conversion.
  69  *
  70  * In my world, it's always summer, and things are probably a bit off
  71  * in other ways too.
  72  */
  73 static const struct {
  74         const char *name;
  75         int offset;
  76         int dst;
  77 } timezone_names[] = {
  78         { "IDLW", -12, 0, },    /* International Date Line West */
  79         { "NT",   -11, 0, },    /* Nome */
  80         { "CAT",  -10, 0, },    /* Central Alaska */
  81         { "HST",  -10, 0, },    /* Hawaii Standard */
  82         { "HDT",  -10, 1, },    /* Hawaii Daylight */
  83         { "YST",   -9, 0, },    /* Yukon Standard */
  84         { "YDT",   -9, 1, },    /* Yukon Daylight */
  85         { "PST",   -8, 0, },    /* Pacific Standard */
  86         { "PDT",   -8, 1, },    /* Pacific Daylight */
  87         { "MST",   -7, 0, },    /* Mountain Standard */
  88         { "MDT",   -7, 1, },    /* Mountain Daylight */
  89         { "CST",   -6, 0, },    /* Central Standard */
  90         { "CDT",   -6, 1, },    /* Central Daylight */
  91         { "EST",   -5, 0, },    /* Eastern Standard */
  92         { "EDT",   -5, 1, },    /* Eastern Daylight */
  93         { "AST",   -3, 0, },    /* Atlantic Standard */
  94         { "ADT",   -3, 1, },    /* Atlantic Daylight */
  95         { "WAT",   -1, 0, },    /* West Africa */
  96
  97         { "GMT",    0, 0, },    /* Greenwich Mean */
  98         { "UTC",    0, 0, },    /* Universal (Coordinated) */
  99
 100         { "WET",    0, 0, },    /* Western European */
 101         { "BST",    0, 1, },    /* British Summer */
 102         { "CET",   +1, 0, },    /* Central European */
 103         { "MET",   +1, 0, },    /* Middle European */
 104         { "MEWT",  +1, 0, },    /* Middle European Winter */
 105         { "MEST",  +1, 1, },    /* Middle European Summer */
 106         { "CEST",  +1, 1, },    /* Central European Summer */
 107         { "MESZ",  +1, 1, },    /* Middle European Summer */
 108         { "FWT",   +1, 0, },    /* French Winter */
 109         { "FST",   +1, 1, },    /* French Summer */
 110         { "EET",   +2, 0, },    /* Eastern Europe, USSR Zone 1 */
 111         { "EEST",  +2, 1, },    /* Eastern European Daylight */
 112         { "WAST",  +7, 0, },    /* West Australian Standard */
 113         { "WADT",  +7, 1, },    /* West Australian Daylight */
 114         { "CCT",   +8, 0, },    /* China Coast, USSR Zone 7 */
 115         { "JST",   +9, 0, },    /* Japan Standard, USSR Zone 8 */
 116         { "EAST", +10, 0, },    /* Eastern Australian Standard */
 117         { "EADT", +10, 1, },    /* Eastern Australian Daylight */
 118         { "GST",  +10, 0, },    /* Guam Standard, USSR Zone 9 */
 119         { "NZT",  +11, 0, },    /* New Zealand */
 120         { "NZST", +11, 0, },    /* New Zealand Standard */
 121         { "NZDT", +11, 1, },    /* New Zealand Daylight */
 122         { "IDLE", +12, 0, },    /* International Date Line East */
 123 };
 124
 125 #define NR_TZ (sizeof(timezone_names) / sizeof(timezone_names[0]))
 126
 127 static int match_string(const char *date, const char *str)
 128 {
 129         int i = 0;
 130
 131         for (i = 0; *date; date++, str++, i++) {
 132                 if (*date == *str)
 133                         continue;
 134                 if (toupper(*date) == toupper(*str))
 135                         continue;
 136                 if (!isalnum(*date))
 137                         break;
 138                 return 0;
 139         }
 140         return i;
 141 }
 142
 143 static int skip_alpha(const char *date)
 144 {
 145         int i = 0;
 146         do {
 147                 i++;
 148         } while (isalpha(date[i]));
 149         return i;
 150 }
 151
 152 /*
 153 * Parse month, weekday, or timezone name
 154 */
 155 static int match_alpha(const char *date, struct tm *tm, int *offset)
 156 {
 157         int i;
 158
 159         for (i = 0; i < 12; i++) {
 160                 int match = match_string(date, month_names[i]);
 161                 if (match >= 3) {
 162                         tm->tm_mon = i;
 163                         return match;
 164                 }
 165         }
 166
 167         for (i = 0; i < 7; i++) {
 168                 int match = match_string(date, weekday_names[i]);
 169                 if (match >= 3) {
 170                         tm->tm_wday = i;
 171                         return match;
 172                 }
 173         }
 174
 175         for (i = 0; i < NR_TZ; i++) {
 176                 int match = match_string(date, timezone_names[i].name);
 177                 if (match >= 3) {
 178                         int off = timezone_names[i].offset;
 179
 180                         /* This is bogus, but we like summer */
 181                         off += timezone_names[i].dst;
 182
 183                         /* Only use the tz name offset if we don't have anything better */
 184                         if (*offset == -1)
 185                                 *offset = 60*off;
 186
 187                         return match;
 188                 }
 189         }
 190
 191         if (match_string(date, "PM") == 2) {
 192                 if (tm->tm_hour > 0 && tm->tm_hour < 12)
 193                         tm->tm_hour += 12;
 194                 return 2;
 195         }
 196
 197         /* BAD CRAP */
 198         return skip_alpha(date);
 199 }
 200
 201 static int is_date(int year, int month, int day, struct tm *tm)
 202 {
 203         if (month > 0 && month < 13 && day > 0 && day < 32) {
 204                 if (year == -1) {
 205                         tm->tm_mon = month-1;
 206                         tm->tm_mday = day;
 207                         return 1;
 208                 }
 209                 if (year >= 1970 && year < 2100) {
 210                         year -= 1900;
 211                 } else if (year > 70 && year < 100) {
 212                         /* ok */
 213                 } else if (year < 38) {
 214                         year += 100;
 215                 } else
 216                         return 0;
 217
 218                 tm->tm_mon = month-1;
 219                 tm->tm_mday = day;
 220                 tm->tm_year = year;
 221                 return 1;
 222         }
 223         return 0;
 224 }
 225
 226 static int match_multi_number(unsigned long num, char c, const char *date, char *end, struct tm *tm)
 227 {
 228         long num2, num3;
 229
 230         num2 = strtol(end+1, &end, 10);
 231         num3 = -1;
 232         if (*end == c && isdigit(end[1]))
 233                 num3 = strtol(end+1, &end, 10);
 234
 235         /* Time? Date? */
 236         switch (c) {
 237         case ':':
 238                 if (num3 < 0)
 239                         num3 = 0;
 240                 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
 241                         tm->tm_hour = num;
 242                         tm->tm_min = num2;
 243                         tm->tm_sec = num3;
 244                         break;
 245                 }
 246                 return 0;
 247
 248         case '-':
 249         case '/':
 250                 if (num > 70) {
 251                         /* yyyy-mm-dd? */
 252                         if (is_date(num, num2, num3, tm))
 253                                 break;
 254                         /* yyyy-dd-mm? */
 255                         if (is_date(num, num3, num2, tm))
 256                                 break;
 257                 }
 258                 /* mm/dd/yy ? */
 259                 if (is_date(num3, num2, num, tm))
 260                         break;
 261                 /* dd/mm/yy ? */
 262                 if (is_date(num3, num, num2, tm))
 263                         break;
 264                 return 0;
 265         }
 266         return end - date;
 267 }
 268
 269 /*
 270  * We've seen a digit. Time? Year? Date?
 271  */
 272 static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt)
 273 {
 274         int n;
 275         char *end;
 276         unsigned long num;
 277
 278         num = strtoul(date, &end, 10);
 279
 280         /*
 281          * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
 282          */
 283         if (num > 946684800) {
 284                 time_t time = num;
 285                 if (gmtime_r(&time, tm)) {
 286                         *tm_gmt = 1;
 287                         return end - date;
 288                 }
 289         }
 290
 291         /*
 292          * Check for special formats: num[:-/]num[same]num
 293          */
 294         switch (*end) {
 295         case ':':
 296         case '/':
 297         case '-':
 298                 if (isdigit(end[1])) {
 299                         int match = match_multi_number(num, *end, date, end, tm);
 300                         if (match)
 301                                 return match;
 302                 }
 303         }
 304
 305         /*
 306          * None of the special formats? Try to guess what
 307          * the number meant. We use the number of digits
 308          * to make a more educated guess..
 309          */
 310         n = 0;
 311         do {
 312                 n++;
 313         } while (isdigit(date[n]));
 314
 315         /* Four-digit year or a timezone? */
 316         if (n == 4) {
 317                 if (num <= 1200 && *offset == -1) {
 318                         unsigned int minutes = num % 100;
 319                         unsigned int hours = num / 100;
 320                         *offset = hours*60 + minutes;
 321                 } else if (num > 1900 && num < 2100)
 322                         tm->tm_year = num - 1900;
 323                 return n;
 324         }
 325
 326         /*
 327          * NOTE! We will give precedence to day-of-month over month or
 328          * year numebers in the 1-12 range. So 05 is always "mday 5",
 329          * unless we already have a mday..
 330          *
 331          * IOW, 01 Apr 05 parses as "April 1st, 2005".
 332          */
 333         if (num > 0 && num < 32 && tm->tm_mday < 0) {
 334                 tm->tm_mday = num;
 335                 return n;
 336         }
 337
 338         /* Two-digit year? */
 339         if (n == 2 && tm->tm_year < 0) {
 340                 if (num < 10 && tm->tm_mday >= 0) {
 341                         tm->tm_year = num + 100;
 342                         return n;
 343                 }
 344                 if (num >= 70) {
 345                         tm->tm_year = num;
 346                         return n;
 347                 }
 348         }
 349
 350         if (num > 0 && num < 32) {
 351                 tm->tm_mday = num;
 352         } else if (num > 1900) {
 353                 tm->tm_year = num - 1900;
 354         } else if (num > 70) {
 355                 tm->tm_year = num;
 356         } else if (num > 0 && num < 13) {
 357                 tm->tm_mon = num-1;
 358         }
 359
 360         return n;
 361 }
 362
 363 static int match_tz(const char *date, int *offp)
 364 {
 365         char *end;
 366         int offset = strtoul(date+1, &end, 10);
 367         int min, hour;
 368         int n = end - date - 1;
 369
 370         min = offset % 100;
 371         hour = offset / 100;
 372
 373         /*
 374          * Don't accept any random crap.. At least 3 digits, and
 375          * a valid minute. We might want to check that the minutes
 376          * are divisible by 30 or something too.
 377          */
 378         if (min < 60 && n > 2) {
 379                 offset = hour*60+min;
 380                 if (*date == '-')
 381                         offset = -offset;
 382
 383                 *offp = offset;
 384         }
 385         return end - date;
 386 }
 387
 388 static int date_string(unsigned long date, int offset, char *buf, int len)
 389 {
 390         int sign = '+';
 391
 392         if (offset < 0) {
 393                 offset = -offset;
 394                 sign = '-';
 395         }
 396         return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
 397 }
 398
 399 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 400    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 401 int parse_date(const char *date, char *result, int maxlen)
 402 {
 403         struct tm tm;
 404         int offset, tm_gmt;
 405         time_t then;
 406
 407         memset(&tm, 0, sizeof(tm));
 408         tm.tm_year = -1;
 409         tm.tm_mon = -1;
 410         tm.tm_mday = -1;
 411         tm.tm_isdst = -1;
 412         offset = -1;
 413         tm_gmt = 0;
 414
 415         for (;;) {
 416                 int match = 0;
 417                 unsigned char c = *date;
 418
 419                 /* Stop at end of string or newline */
 420                 if (!c || c == '\n')
 421                         break;
 422
 423                 if (isalpha(c))
 424                         match = match_alpha(date, &tm, &offset);
 425                 else if (isdigit(c))
 426                         match = match_digit(date, &tm, &offset, &tm_gmt);
 427                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 428                         match = match_tz(date, &offset);
 429
 430                 if (!match) {
 431                         /* BAD CRAP */
 432                         match = 1;
 433                 }
 434
 435                 date += match;
 436         }
 437
 438         /* mktime uses local timezone */
 439         then = my_mktime(&tm);
 440         if (offset == -1)
 441                 offset = (then - mktime(&tm)) / 60;
 442
 443         if (then == -1)
 444                 return -1;
 445
 446         if (!tm_gmt)
 447                 then -= offset * 60;
 448         return date_string(then, offset, result, maxlen);
 449 }
 450
 451 void datestamp(char *buf, int bufsize)
 452 {
 453         time_t now;
 454         int offset;
 455
 456         time(&now);
 457
 458         offset = my_mktime(localtime(&now)) - now;
 459         offset /= 60;
 460
 461         date_string(now, offset, buf, bufsize);
 462 }