nsz Git - musl/blob - src/time/strftime.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <langinfo.h>
   4 #include <time.h>
   5 #include <limits.h>
   6 #include "__time.h"
   7
   8 // FIXME: integer overflows
   9
  10 const char *__langinfo(nl_item);
  11
  12 static int is_leap(int y)
  13 {
  14         /* Avoid overflow */
  15         if (y>INT_MAX-1900) y -= 2000;
  16         y += 1900;
  17         return !(y%4) && ((y%100) || !(y%400));
  18 }
  19
  20 static int week_num(const struct tm *tm)
  21 {
  22         int val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
  23         /* If 1 Jan is just 1-3 days past Monday,
  24          * the previous week is also in this year. */
  25         if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
  26                 val++;
  27         if (!val) {
  28                 val = 52;
  29                 /* If 31 December of prev year a Thursday,
  30                  * or Friday of a leap year, then the
  31                  * prev year has 53 weeks. */
  32                 int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
  33                 if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
  34                         val++;
  35         } else if (val == 53) {
  36                 /* If 1 January is not a Thursday, and not
  37                  * a Wednesday of a leap year, then this
  38                  * year has only 52 weeks. */
  39                 int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
  40                 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
  41                         val = 1;
  42         }
  43         return val;
  44 }
  45
  46 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
  47 {
  48         nl_item item;
  49         int val;
  50         const char *fmt;
  51         size_t l;
  52         for (l=0; *f && l<n; f++) {
  53                 if (*f == '%') {
  54 do_fmt:
  55                 switch (*++f) {
  56                 case '%':
  57                         goto literal;
  58                 case 'E':
  59                 case 'O':
  60                         goto do_fmt;
  61                 case 'a':
  62                         item = ABDAY_1 + tm->tm_wday;
  63                         goto nl_strcat;
  64                 case 'A':
  65                         item = DAY_1 + tm->tm_wday;
  66                         goto nl_strcat;
  67                 case 'h':
  68                 case 'b':
  69                         item = ABMON_1 + tm->tm_mon;
  70                         goto nl_strcat;
  71                 case 'B':
  72                         item = MON_1 + tm->tm_mon;
  73                         goto nl_strcat;
  74                 case 'c':
  75                         item = D_T_FMT;
  76                         goto nl_strftime;
  77                 case 'C':
  78                         val = (1900+tm->tm_year) / 100;
  79                         fmt = "%02d";
  80                         goto number;
  81                 case 'd':
  82                         val = tm->tm_mday;
  83                         fmt = "%02d";
  84                         goto number;
  85                 case 'D':
  86                         fmt = "%m/%d/%y";
  87                         goto recu_strftime;
  88                 case 'e':
  89                         val = tm->tm_mday;
  90                         fmt = "%2d";
  91                         goto number;
  92                 case 'F':
  93                         fmt = "%Y-%m-%d";
  94                         goto recu_strftime;
  95                 case 'g':
  96                 case 'G':
  97                         fmt = "%04d";
  98                         val = tm->tm_year + 1900;
  99                         if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
 100                         else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
 101                         if (*f=='g') {
 102                                 fmt = "%02d";
 103                                 val %= 100;
 104                         }
 105                         goto number;
 106                 case 'H':
 107                         val = tm->tm_hour;
 108                         fmt = "%02d";
 109                         goto number;
 110                 case 'I':
 111                         val = tm->tm_hour;
 112                         if (!val) val = 12;
 113                         else if (val > 12) val -= 12;
 114                         fmt = "%02d";
 115                         goto number;
 116                 case 'j':
 117                         val = tm->tm_yday+1;
 118                         fmt = "%03d";
 119                         goto number;
 120                 case 'm':
 121                         val = tm->tm_mon+1;
 122                         fmt = "%02d";
 123                         goto number;
 124                 case 'M':
 125                         val = tm->tm_min;
 126                         fmt = "%02d";
 127                         goto number;
 128                 case 'n':
 129                         s[l++] = '\n';
 130                         continue;
 131                 case 'p':
 132                         item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
 133                         goto nl_strcat;
 134                 case 'r':
 135                         item = T_FMT_AMPM;
 136                         goto nl_strftime;
 137                 case 'R':
 138                         fmt = "%H:%M";
 139                         goto recu_strftime;
 140                 case 'S':
 141                         val = tm->tm_sec;
 142                         fmt = "%02d";
 143                         goto number;
 144                 case 't':
 145                         s[l++] = '\t';
 146                         continue;
 147                 case 'T':
 148                         fmt = "%H:%M:%S";
 149                         goto recu_strftime;
 150                 case 'u':
 151                         val = tm->tm_wday ? tm->tm_wday : 7;
 152                         fmt = "%d";
 153                         goto number;
 154                 case 'U':
 155                         val = (tm->tm_yday + 7 - tm->tm_wday) / 7;
 156                         fmt = "%02d";
 157                         goto number;
 158                 case 'W':
 159                         val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
 160                         fmt = "%02d";
 161                         goto number;
 162                 case 'V':
 163                         val = week_num(tm);
 164                         fmt = "%02d";
 165                         goto number;
 166                 case 'w':
 167                         val = tm->tm_wday;
 168                         fmt = "%d";
 169                         goto number;
 170                 case 'x':
 171                         item = D_FMT;
 172                         goto nl_strftime;
 173                 case 'X':
 174                         item = T_FMT;
 175                         goto nl_strftime;
 176                 case 'y':
 177                         val = tm->tm_year % 100;
 178                         fmt = "%02d";
 179                         goto number;
 180                 case 'Y':
 181                         val = tm->tm_year + 1900;
 182                         fmt = "%04d";
 183                         goto number;
 184                 case 'z':
 185                         if (tm->tm_isdst < 0) continue;
 186                         val = -__timezone - (tm->tm_isdst ? __dst_offset : 0);
 187                         l += snprintf(s+l, n-l, "%+.2d%.2d", val/3600, abs(val%3600)/60);
 188                         continue;
 189                 case 'Z':
 190                         if (tm->tm_isdst < 0 || !__tzname[0] || !__tzname[0][0])
 191                                 continue;
 192                         l += snprintf(s+l, n-l, "%s", __tzname[!!tm->tm_isdst]);
 193                         continue;
 194                 default:
 195                         return 0;
 196                 }
 197                 }
 198 literal:
 199                 s[l++] = *f;
 200                 continue;
 201 number:
 202                 l += snprintf(s+l, n-l, fmt, val);
 203                 continue;
 204 nl_strcat:
 205                 l += snprintf(s+l, n-l, "%s", __langinfo(item));
 206                 continue;
 207 nl_strftime:
 208                 fmt = __langinfo(item);
 209 recu_strftime:
 210                 l += strftime(s+l, n-l, fmt, tm);
 211         }
 212         if (l >= n) return 0;
 213         s[l] = 0;
 214         return l;
 215 }