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