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         "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  34         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  35 };
  36
  37 static const char *weekday_names[] = {
  38         "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  39 };
  40
  41
  42 static char *skipfws(char *str)
  43 {
  44         while (isspace(*str))
  45                 str++;
  46         return str;
  47 }
  48
  49
  50 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
  51    (i.e. English) day/month names, and it doesn't work correctly with %z. */
  52 void parse_date(char *date, char *result, int maxlen)
  53 {
  54         struct tm tm;
  55         char *p, *tz;
  56         int i, offset;
  57         time_t then;
  58
  59         memset(&tm, 0, sizeof(tm));
  60
  61         /* Skip day-name */
  62         p = skipfws(date);
  63         if (!isdigit(*p)) {
  64                 for (i=0; i<7; i++) {
  65                         if (!strncmp(p,weekday_names[i],3) && p[3] == ',') {
  66                                 p = skipfws(p+4);
  67                                 goto day;
  68                         }
  69                 }
  70                 return;
  71         }
  72
  73         /* day */
  74  day:
  75         tm.tm_mday = strtoul(p, &p, 10);
  76
  77         if (tm.tm_mday < 1 || tm.tm_mday > 31)
  78                 return;
  79
  80         if (!isspace(*p))
  81                 return;
  82
  83         p = skipfws(p);
  84
  85         /* month */
  86
  87         for (i=0; i<12; i++) {
  88                 if (!strncmp(p, month_names[i], 3) && isspace(p[3])) {
  89                         tm.tm_mon = i;
  90                         p = skipfws(p+strlen(month_names[i]));
  91                         goto year;
  92                 }
  93         }
  94         return; /* Error -- bad month */
  95
  96         /* year */
  97  year:
  98         tm.tm_year = strtoul(p, &p, 10);
  99
 100         if (!tm.tm_year && !isspace(*p))
 101                 return;
 102
 103         if (tm.tm_year > 1900)
 104                 tm.tm_year -= 1900;
 105
 106         p=skipfws(p);
 107
 108         /* hour */
 109         if (!isdigit(*p))
 110                 return;
 111         tm.tm_hour = strtoul(p, &p, 10);
 112
 113         if (tm.tm_hour > 23)
 114                 return;
 115
 116         if (*p != ':')
 117                 return; /* Error -- bad time */
 118         p++;
 119
 120         /* minute */
 121         if (!isdigit(*p))
 122                 return;
 123         tm.tm_min = strtoul(p, &p, 10);
 124
 125         if (tm.tm_min > 59)
 126                 return;
 127
 128         if (*p != ':')
 129                 goto zone;
 130         p++;
 131
 132         /* second */
 133         if (!isdigit(*p))
 134                 return;
 135         tm.tm_sec = strtoul(p, &p, 10);
 136
 137         if (tm.tm_sec > 60)
 138                 return;
 139
 140  zone:
 141         if (!isspace(*p))
 142                 return;
 143
 144         p = skipfws(p);
 145
 146         if (*p == '-')
 147                 offset = -60;
 148         else if (*p == '+')
 149                 offset = 60;
 150         else
 151                return;
 152
 153         if (!isdigit(p[1]) || !isdigit(p[2]) || !isdigit(p[3]) || !isdigit(p[4]))
 154                 return;
 155
 156         tz = p;
 157         i = strtoul(p+1, NULL, 10);
 158         offset *= ((i % 100) + ((i / 100) * 60));
 159
 160         p = skipfws(p + 5);
 161         if (*p && *p != '(') /* trailing comment like (EDT) is ok */
 162                 return;
 163
 164         then = my_mktime(&tm); /* mktime uses local timezone */
 165         if (then == -1)
 166                 return;
 167
 168         then -= offset;
 169
 170         snprintf(result, maxlen, "%lu %5.5s", then, tz);
 171 }
 172
 173 void datestamp(char *buf, int bufsize)
 174 {
 175         time_t now;
 176         int offset;
 177
 178         time(&now);
 179
 180         offset = my_mktime(localtime(&now)) - now;
 181         offset /= 60;
 182
 183         snprintf(buf, bufsize, "%lu %+05d", now, offset/60*100 + offset%60);
 184 }