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 static int skip_alpha(const char *date)
 118 {
 119         int i = 0;
 120         do {
 121                 i++;
 122         } while (isalpha(date[i]));
 123         return i;
 124 }
 125
 126 /*
 127 * Parse month, weekday, or timezone name
 128 */
 129 static int match_alpha(const char *date, struct tm *tm, int *offset)
 130 {
 131         int i;
 132
 133         for (i = 0; i < 12; i++) {
 134                 int match = match_string(date, month_names[i]);
 135                 if (match >= 3) {
 136                         tm->tm_mon = i;
 137                         return match;
 138                 }
 139         }
 140
 141         for (i = 0; i < 7; i++) {
 142                 int match = match_string(date, weekday_names[i]);
 143                 if (match >= 3) {
 144                         tm->tm_wday = i;
 145                         return match;
 146                 }
 147         }
 148
 149         for (i = 0; i < NR_TZ; i++) {
 150                 int match = match_string(date, timezone_names[i].name);
 151                 if (match >= 3) {
 152                         int off = timezone_names[i].offset;
 153
 154                         /* This is bogus, but we like summer */
 155                         off += timezone_names[i].dst;
 156
 157                         /* Only use the tz name offset if we don't have anything better */
 158                         if (*offset == -1)
 159                                 *offset = 60*off;
 160
 161                         return match;
 162                 }
 163         }
 164
 165         if (match_string(date, "PM") == 2) {
 166                 if (tm->tm_hour > 0 && tm->tm_hour < 12)
 167                         tm->tm_hour += 12;
 168                 return 2;
 169         }
 170
 171         /* BAD CRAP */
 172         return skip_alpha(date);
 173 }
 174
 175 static int is_date(int year, int month, int day, struct tm *tm)
 176 {
 177         if (month > 0 && month < 13 && day > 0 && day < 32) {
 178                 if (year == -1) {
 179                         tm->tm_mon = month-1;
 180                         tm->tm_mday = day;
 181                         return 1;
 182                 }
 183                 if (year >= 1970 && year < 2100) {
 184                         year -= 1900;
 185                 } else if (year > 70 && year < 100) {
 186                         /* ok */
 187                 } else if (year < 38) {
 188                         year += 100;
 189                 } else
 190                         return 0;
 191
 192                 tm->tm_mon = month-1;
 193                 tm->tm_mday = day;
 194                 tm->tm_year = year;
 195                 return 1;
 196         }
 197         return 0;
 198 }
 199
 200 static int match_multi_number(unsigned long num, char c, char *date, char *end, struct tm *tm)
 201 {
 202         long num2, num3;
 203
 204         num2 = strtol(end+1, &end, 10);
 205         num3 = -1;
 206         if (*end == c && isdigit(end[1]))
 207                 num3 = strtol(end+1, &end, 10);
 208
 209         /* Time? Date? */
 210         switch (c) {
 211         case ':':
 212                 if (num3 < 0)
 213                         num3 = 0;
 214                 if (num < 25 && num2 >= 0 && num2 < 60 && num3 >= 0 && num3 <= 60) {
 215                         tm->tm_hour = num;
 216                         tm->tm_min = num2;
 217                         tm->tm_sec = num3;
 218                         break;
 219                 }
 220                 return 0;
 221
 222         case '-':
 223         case '/':
 224                 if (num > 70) {
 225                         /* yyyy-mm-dd? */
 226                         if (is_date(num, num2, num3, tm))
 227                                 break;
 228                         /* yyyy-dd-mm? */
 229                         if (is_date(num, num3, num2, tm))
 230                                 break;
 231                 }
 232                 /* mm/dd/yy ? */
 233                 if (is_date(num3, num2, num, tm))
 234                         break;
 235                 /* dd/mm/yy ? */
 236                 if (is_date(num3, num, num2, tm))
 237                         break;
 238                 return 0;
 239         }
 240         return end - date;
 241 }
 242
 243 /*
 244  * We've seen a digit. Time? Year? Date?
 245  */
 246 static int match_digit(char *date, struct tm *tm, int *offset)
 247 {
 248         int n;
 249         char *end;
 250         unsigned long num;
 251
 252         num = strtoul(date, &end, 10);
 253
 254         /*
 255          * Seconds since 1970? We trigger on that for anything after Jan 1, 2000
 256          */
 257         if (num > 946684800) {
 258                 time_t time = num;
 259                 if (gmtime_r(&time, tm))
 260                         return end - date;
 261         }
 262
 263         /*
 264          * Check for special formats: num[:-/]num[same]num
 265          */
 266         switch (*end) {
 267         case ':':
 268         case '/':
 269         case '-':
 270                 if (isdigit(end[1])) {
 271                         int match = match_multi_number(num, *end, date, end, tm);
 272                         if (match)
 273                                 return match;
 274                 }
 275         }
 276
 277         /*
 278          * None of the special formats? Try to guess what
 279          * the number meant. We use the number of digits
 280          * to make a more educated guess..
 281          */
 282         n = 0;
 283         do {
 284                 n++;
 285         } while (isdigit(date[n]));
 286
 287         /* Four-digit year or a timezone? */
 288         if (n == 4) {
 289                 if (num <= 1200 && *offset == -1) {
 290                         unsigned int minutes = num % 100;
 291                         unsigned int hours = num / 100;
 292                         *offset = hours*60 + minutes;
 293                 } else if (num > 1900 && num < 2100)
 294                         tm->tm_year = num - 1900;
 295                 return n;
 296         }
 297
 298         /*
 299          * NOTE! We will give precedence to day-of-month over month or
 300          * year numebers in the 1-12 range. So 05 is always "mday 5",
 301          * unless we already have a mday..
 302          *
 303          * IOW, 01 Apr 05 parses as "April 1st, 2005".
 304          */
 305         if (num > 0 && num < 32 && tm->tm_mday < 0) {
 306                 tm->tm_mday = num;
 307                 return n;
 308         }
 309
 310         /* Two-digit year? */
 311         if (n == 2 && tm->tm_year < 0) {
 312                 if (num < 10 && tm->tm_mday >= 0) {
 313                         tm->tm_year = num + 100;
 314                         return n;
 315                 }
 316                 if (num >= 70) {
 317                         tm->tm_year = num;
 318                         return n;
 319                 }
 320         }
 321
 322         if (num > 0 && num < 32) {
 323                 tm->tm_mday = num;
 324         } else if (num > 1900) {
 325                 tm->tm_year = num - 1900;
 326         } else if (num > 70) {
 327                 tm->tm_year = num;
 328         } else if (num > 0 && num < 13) {
 329                 tm->tm_mon = num-1;
 330         }
 331
 332         return n;
 333 }
 334
 335 static int match_tz(char *date, int *offp)
 336 {
 337         char *end;
 338         int offset = strtoul(date+1, &end, 10);
 339         int min, hour;
 340         int n = end - date - 1;
 341
 342         min = offset % 100;
 343         hour = offset / 100;
 344
 345         /*
 346          * Don't accept any random crap.. At least 3 digits, and
 347          * a valid minute. We might want to check that the minutes
 348          * are divisible by 30 or something too.
 349          */
 350         if (min < 60 && n > 2) {
 351                 offset = hour*60+min;
 352                 if (*date == '-')
 353                         offset = -offset;
 354
 355                 *offp = offset;
 356         }
 357         return end - date;
 358 }
 359
 360 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 361    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 362 void parse_date(char *date, char *result, int maxlen)
 363 {
 364         struct tm tm;
 365         int offset, sign;
 366         time_t then;
 367
 368         memset(&tm, 0, sizeof(tm));
 369         tm.tm_year = -1;
 370         tm.tm_mon = -1;
 371         tm.tm_mday = -1;
 372         tm.tm_isdst = -1;
 373         offset = -1;
 374
 375         for (;;) {
 376                 int match = 0;
 377                 unsigned char c = *date;
 378
 379                 /* Stop at end of string or newline */
 380                 if (!c || c == '\n')
 381                         break;
 382
 383                 if (isalpha(c))
 384                         match = match_alpha(date, &tm, &offset);
 385                 else if (isdigit(c))
 386                         match = match_digit(date, &tm, &offset);
 387                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 388                         match = match_tz(date, &offset);
 389
 390                 if (!match) {
 391                         /* BAD CRAP */
 392                         match = 1;
 393                 }
 394
 395                 date += match;
 396         }
 397
 398         /* mktime uses local timezone */
 399         then = my_mktime(&tm);
 400         if (offset == -1)
 401                 offset = (then - mktime(&tm)) / 60;
 402
 403         if (then == -1)
 404                 return;
 405
 406         then -= offset * 60;
 407
 408         sign = '+';
 409         if (offset < 0) {
 410                 offset = -offset;
 411                 sign = '-';
 412         }
 413
 414         snprintf(result, maxlen, "%lu %c%02d%02d", then, sign, offset/60, offset % 60);
 415 }
 416
 417 void datestamp(char *buf, int bufsize)
 418 {
 419         time_t now;
 420         int offset;
 421
 422         time(&now);
 423
 424         offset = my_mktime(localtime(&now)) - now;
 425         offset /= 60;
 426
 427         snprintf(buf, bufsize, "%lu %+05d", now, offset/60*100 + offset%60);
 428 }