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