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 } timezone_names[] = {
  51         { "IDLW", -12 },        /* International Date Line West */
  52         { "NT",   -11 },        /* Nome */
  53         { "CAT",  -10 },        /* Central Alaska */
  54         { "HST",  -10 },        /* Hawaii Standard */
  55         { "HDT",   -9 },        /* Hawaii Daylight */
  56         { "YDT",   -8 },        /* Yukon Daylight */
  57         { "YST",   -9 },        /* Yukon Standard */
  58         { "PST",   -8 },        /* Pacific Standard */
  59         { "PDT",   -7 },        /* Pacific Daylight */
  60         { "MST",   -7 },        /* Mountain Standard */
  61         { "MDT",   -6 },        /* Mountain Daylight */
  62         { "CST",   -6 },        /* Central Standard */
  63         { "CDT",   -5 },        /* Central Daylight */
  64         { "EST",   -5 },        /* Eastern Standard */
  65         { "EDT",   -4 },        /* Eastern Daylight */
  66         { "AST",   -3 },        /* Atlantic Standard */
  67         { "ADT",   -2 },        /* Atlantic Daylight */
  68         { "WAT",   -1 },        /* West Africa */
  69
  70         { "GMT",    0 },        /* Greenwich Mean */
  71         { "UTC",    0 },        /* Universal (Coordinated) */
  72
  73         { "WET",    0 },        /* Western European */
  74         { "BST",    0 },        /* British Summer */
  75         { "CET",   +1 },        /* Central European */
  76         { "MET",   +1 },        /* Middle European */
  77         { "MEWT",  +1 },        /* Middle European Winter */
  78         { "MEST",  +2 },        /* Middle European Summer */
  79         { "CEST",  +2 },        /* Central European Summer */
  80         { "MESZ",  +1 },        /* Middle European Summer */
  81         { "FWT",   +1 },        /* French Winter */
  82         { "FST",   +2 },        /* French Summer */
  83         { "EET",   +2 },        /* Eastern Europe, USSR Zone 1 */
  84         { "WAST",  +7 },        /* West Australian Standard */
  85         { "WADT",  +8 },        /* West Australian Daylight */
  86         { "CCT",   +8 },        /* China Coast, USSR Zone 7 */
  87         { "JST",   +9 },        /* Japan Standard, USSR Zone 8 */
  88         { "EAST", +10 },        /* Eastern Australian Standard */
  89         { "EADT", +11 },        /* Eastern Australian Daylight */
  90         { "GST",  +10 },        /* Guam Standard, USSR Zone 9 */
  91         { "NZT",  +11 },        /* New Zealand */
  92         { "NZST", +11 },        /* New Zealand Standard */
  93         { "NZDT", +12 },        /* New Zealand Daylight */
  94         { "IDLE", +12 },        /* International Date Line East */
  95 };
  96
  97 #define NR_TZ (sizeof(timezone_names) / sizeof(timezone_names[0]))
  98
  99 static int match_string(const char *date, const char *str)
 100 {
 101         int i = 0;
 102
 103         for (i = 0; *date; date++, str++, i++) {
 104                 if (*date == *str)
 105                         continue;
 106                 if (toupper(*date) == toupper(*str))
 107                         continue;
 108                 if (!isalnum(*date))
 109                         break;
 110                 return 0;
 111         }
 112         return i;
 113 }
 114
 115 /*
 116 * Parse month, weekday, or timezone name
 117 */
 118 static int match_alpha(const char *date, struct tm *tm, int *offset)
 119 {
 120         int i;
 121
 122         for (i = 0; i < 12; i++) {
 123                 int match = match_string(date, month_names[i]);
 124                 if (match >= 3) {
 125                         tm->tm_mon = i;
 126                         return match;
 127                 }
 128         }
 129
 130         for (i = 0; i < 7; i++) {
 131                 int match = match_string(date, weekday_names[i]);
 132                 if (match >= 3) {
 133                         tm->tm_wday = i;
 134                         return match;
 135                 }
 136         }
 137
 138         for (i = 0; i < NR_TZ; i++) {
 139                 int match = match_string(date, timezone_names[i].name);
 140                 if (match >= 3) {
 141                         *offset = 60*timezone_names[i].offset;
 142                         return match;
 143                 }
 144         }
 145
 146         /* BAD CRAP */
 147         return 0;
 148 }
 149
 150 static int match_digit(char *date, struct tm *tm, int *offset)
 151 {
 152         char *end, c;
 153         unsigned long num, num2, num3;
 154
 155         num = strtoul(date, &end, 10);
 156
 157         /* Time? num:num[:num] */
 158         if (num < 24 && end[0] == ':' && isdigit(end[1])) {
 159                 tm->tm_hour = num;
 160                 num = strtoul(end+1, &end, 10);
 161                 if (num < 60) {
 162                         tm->tm_min = num;
 163                         if (end[0] == ':' && isdigit(end[1])) {
 164                                 num = strtoul(end+1, &end, 10);
 165                                 if (num < 61)
 166                                         tm->tm_sec = num;
 167                         }
 168                 }
 169                 return end - date;
 170         }
 171
 172         /* Year? Day of month? Numeric date-string?*/
 173         c = *end;
 174         switch (c) {
 175         default:
 176                 if (num > 0 && num < 32) {
 177                         tm->tm_mday = num;
 178                         break;
 179                 }
 180                 if (num > 1900) {
 181                         tm->tm_year = num - 1900;
 182                         break;
 183                 }
 184                 if (num > 70) {
 185                         tm->tm_year = num;
 186                         break;
 187                 }
 188                 break;
 189
 190         case '-':
 191         case '/':
 192                 if (num && num < 32 && isdigit(end[1])) {
 193                         num2 = strtoul(end+1, &end, 10);
 194                         if (!num2 || num2 > 31)
 195                                 break;
 196                         if (num > 12) {
 197                                 if (num2 > 12)
 198                                         break;
 199                                 num3 = num;
 200                                 num  = num2;
 201                                 num2 = num3;
 202                         }
 203                         tm->tm_mon = num - 1;
 204                         tm->tm_mday = num2;
 205                         if (*end == c && isdigit(end[1])) {
 206                                 num3 = strtoul(end+1, &end, 10);
 207                                 if (num3 > 1900)
 208                                         num3 -= 1900;
 209                                 else if (num3 < 38)
 210                                         num3 += 100;
 211                                 tm->tm_year = num3;
 212                         }
 213                         break;
 214                 }
 215         }
 216
 217         return end - date;
 218
 219 }
 220
 221 static int match_tz(char *date, int *offp)
 222 {
 223         char *end;
 224         int offset = strtoul(date+1, &end, 10);
 225         int min, hour;
 226
 227         min = offset % 100;
 228         hour = offset / 100;
 229
 230         offset = hour*60+min;
 231         if (*date == '-')
 232                 offset = -offset;
 233
 234         *offp = offset;
 235         return end - date;
 236 }
 237
 238 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
 239    (i.e. English) day/month names, and it doesn't work correctly with %z. */
 240 void parse_date(char *date, char *result, int maxlen)
 241 {
 242         struct tm tm;
 243         int offset;
 244         time_t then;
 245
 246         memset(&tm, 0, sizeof(tm));
 247         tm.tm_year = -1;
 248         tm.tm_mon = -1;
 249         tm.tm_mday = -1;
 250         tm.tm_isdst = -1;
 251         offset = -1;
 252
 253         for (;;) {
 254                 int match = 0;
 255                 unsigned char c = *date;
 256
 257                 /* Stop at end of string or newline */
 258                 if (!c || c == '\n')
 259                         break;
 260
 261                 if (isalpha(c))
 262                         match = match_alpha(date, &tm, &offset);
 263                 else if (isdigit(c))
 264                         match = match_digit(date, &tm, &offset);
 265                 else if ((c == '-' || c == '+') && isdigit(date[1]))
 266                         match = match_tz(date, &offset);
 267
 268                 if (!match) {
 269                         /* BAD CRAP */
 270                         match = 1;
 271                 }
 272
 273                 date += match;
 274         }
 275
 276         /* mktime uses local timezone */
 277         then = my_mktime(&tm);
 278         if (offset == -1)
 279                 offset = (then - mktime(&tm)) / 60;
 280
 281         if (then == -1)
 282                 return;
 283
 284         then -= offset * 60;
 285
 286         snprintf(result, maxlen, "%lu %+03d%02d", then, offset/60, offset % 60);
 287 }
 288
 289 void datestamp(char *buf, int bufsize)
 290 {
 291         time_t now;
 292         int offset;
 293
 294         time(&now);
 295
 296         offset = my_mktime(localtime(&now)) - now;
 297         offset /= 60;
 298
 299         snprintf(buf, bufsize, "%lu %+05d", now, offset/60*100 + offset%60);
 300 }