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         { "WAST",  +7, 0, },    /* West Australian Standard */
  86         { "WADT",  +7, 1, },    /* West Australian Daylight */
  87         { "CCT",   +8, 0, },    /* China Coast, USSR Zone 7 */
  88         { "JST",   +9, 0, },    /* Japan Standard, USSR Zone 8 */
  89         { "EAST", +10, 0, },    /* Eastern Australian Standard */
  90         { "EADT", +10, 1, },    /* Eastern Australian Daylight */
  91         { "GST",  +10, 0, },    /* Guam Standard, USSR Zone 9 */
  92         { "NZT",  +11, 0, },    /* New Zealand */
  93         { "NZST", +11, 0, },    /* New Zealand Standard */
  94         { "NZDT", +11, 1, },    /* New Zealand Daylight */
  95         { "IDLE", +12, 0, },    /* International Date Line East */
  96 };
  97
  98 #define NR_TZ (sizeof(timezone_names) / sizeof(timezone_names[0]))
  99
 100 static int match_string(const char *date, const char *str)
 101 {
 102         int i = 0;
 103
 104         for (i = 0; *date; date++, str++, i++) {
 105                 if (*date == *str)
 106                         continue;
 107                 if (toupper(*date) == toupper(*str))
 108                         continue;
 109                 if (!isalnum(*date))
 110                         break;
 111                 return 0;
 112         }
 113         return i;
 114 }
 115
 116 /*
 117 * Parse month, weekday, or timezone name
 118 */
 119 static int match_alpha(const char *date, struct tm *tm, int *offset)
 120 {
 121         int i;
 122
 123         for (i = 0; i < 12; i++) {
 124                 int match = match_string(date, month_names[i]);
 125                 if (match >= 3) {
 126                         tm->tm_mon = i;
 127                         return match;
 128                 }
 129         }
 130
 131         for (i = 0; i < 7; i++) {
 132                 int match = match_string(date, weekday_names[i]);
 133                 if (match >= 3) {
 134                         tm->tm_wday = i;
 135                         return match;
 136                 }
 137         }
 138
 139         for (i = 0; i < NR_TZ; i++) {
 140                 int match = match_string(date, timezone_names[i].name);
 141                 if (match >= 3) {
 142                         int off = timezone_names[i].offset;
 143
 144                         /* This is bogus, but we like summer */
 145                         off += timezone_names[i].dst;
 146
 147                         *offset = 60*off;
 148                         return match;
 149                 }
 150         }
 151
 152         /* BAD CRAP */
 153         return 0;
 154 }
 155
 156 static int match_digit(char *date, struct tm *tm, int *offset)
 157 {
 158         char *end, c;
 159         unsigned long num, num2, num3;
 160
 161         num = strtoul(date, &end, 10);
 162
 163         /* Time? num:num[:num] */
 164         if (num < 24 && end[0] == ':' && isdigit(end[1])) {
 165                 tm->tm_hour = num;
 166                 num = strtoul(end+1, &end, 10);
 167                 if (num < 60) {
 168                         tm->tm_min = num;
 169                         if (end[0] == ':' && isdigit(end[1])) {
 170                                 num = strtoul(end+1, &end, 10);
 171                                 if (num < 61)
 172                                         tm->tm_sec = num;
 173                         }
 174                 }
 175                 return end - date;
 176         }
 177
 178         /* Year? Day of month? Numeric date-string?*/
 179         c = *end;
 180         switch (c) {
 181         default:
 182                 if (num > 0 && num < 32) {
 183                         tm->tm_mday = num;
 184                         break;
 185                 }
 186                 if (num > 1900) {
 187                         tm->tm_year = num - 1900;
 188                         break;
 189                 }
 190                 if (num > 70) {
 191                         tm->tm_year = num;
 192                         break;
 193                 }
 194                 break;
 195
 196         case '-':
 197         case '/':
 198                 if (num && num < 32 && isdigit(end[1])) {
 199                         num2 = strtoul(end+1, &end, 10);
 200                         if (!num2 || num2 > 31)
 201                                 break;
 202                         if (num > 12) {
 203                                 if (num2 > 12)
 204                                         break;
 205                                 num3 = num;
 206                                 num  = num2;
 207                                 num2 = num3;
 208                         }
 209                         tm->tm_mon = num - 1;
 210                         tm->tm_mday = num2;
 211                         if (*end == c && isdigit(end[1])) {
 212                                 num3 = strtoul(end+1, &end, 10);
 213                                 if (num3 > 1900)
 214                                         num3 -= 1900;
 215                                 else if (num3 < 38)
 216                                         num3 += 100;
 217                                 tm->tm_year = num3;
 218                         }
 219                         break;
 220                 }
 221         }
 222
 223         return end - date;
 224
 225 }
 226
 227 static int match_tz(char *date, int *offp)
 228 {
 229         char *end;
 230         int offset = strtoul(date+1, &end, 10);
 231         int min, hour;
 232
 233         min = offset % 100;
 234         hour = offset / 100;
 235
 236         offset = hour*60+min;
 237         if (*date == '-')
 238                 offset = -offset;
 239
 240         *offp = offset;
 241         return end - date;
 242 }
 243
 244 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 245    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 246 void parse_date(char *date, char *result, int maxlen)
 247 {
 248         struct tm tm;
 249         int offset;
 250         time_t then;
 251
 252         memset(&tm, 0, sizeof(tm));
 253         tm.tm_year = -1;
 254         tm.tm_mon = -1;
 255         tm.tm_mday = -1;
 256         tm.tm_isdst = -1;
 257         offset = -1;
 258
 259         for (;;) {
 260                 int match = 0;
 261                 unsigned char c = *date;
 262
 263                 /* Stop at end of string or newline */
 264                 if (!c || c == '\n')
 265                         break;
 266
 267                 if (isalpha(c))
 268                         match = match_alpha(date, &tm, &offset);
 269                 else if (isdigit(c))
 270                         match = match_digit(date, &tm, &offset);
 271                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 272                         match = match_tz(date, &offset);
 273
 274                 if (!match) {
 275                         /* BAD CRAP */
 276                         match = 1;
 277                 }
 278
 279                 date += match;
 280         }
 281
 282         /* mktime uses local timezone */
 283         then = my_mktime(&tm);
 284         if (offset == -1)
 285                 offset = (then - mktime(&tm)) / 60;
 286
 287         if (then == -1)
 288                 return;
 289
 290         then -= offset * 60;
 291
 292         snprintf(result, maxlen, "%lu %+03d%02d", then, offset/60, offset % 60);
 293 }
 294
 295 void datestamp(char *buf, int bufsize)
 296 {
 297         time_t now;
 298         int offset;
 299
 300         time(&now);
 301
 302         offset = my_mktime(localtime(&now)) - now;
 303         offset /= 60;
 304
 305         snprintf(buf, bufsize, "%lu %+05d", now, offset/60*100 + offset%60);
 306 }