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