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