src/time/strftime.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <langinfo.h>
   5 #include <locale.h>
   6 #include <ctype.h>
   7 #include <time.h>
   8 #include <limits.h>
   9 #include "locale_impl.h"
  10 #include "time_impl.h"
  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 + 7U - (tm->tm_wday+6U)%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 + 371U - tm->tm_yday - 2) % 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 + 7U - tm->tm_yday - 1) % 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 + 371U - tm->tm_yday) % 7;
  40                 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
  41                         val = 1;
  42         }
  43         return val;
  44 }
  45
  46 const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *tm, locale_t loc, int pad)
  47 {
  48         nl_item item;
  49         long long val;
  50         const char *fmt = "-";
  51         int width = 2, def_pad = '0';
  52
  53         switch (f) {
  54         case 'a':
  55                 if (tm->tm_wday > 6U) goto string;
  56                 item = ABDAY_1 + tm->tm_wday;
  57                 goto nl_strcat;
  58         case 'A':
  59                 if (tm->tm_wday > 6U) goto string;
  60                 item = DAY_1 + tm->tm_wday;
  61                 goto nl_strcat;
  62         case 'h':
  63         case 'b':
  64                 if (tm->tm_mon > 11U) goto string;
  65                 item = ABMON_1 + tm->tm_mon;
  66                 goto nl_strcat;
  67         case 'B':
  68                 if (tm->tm_mon > 11U) goto string;
  69                 item = MON_1 + tm->tm_mon;
  70                 goto nl_strcat;
  71         case 'c':
  72                 item = D_T_FMT;
  73                 goto nl_strftime;
  74         case 'C':
  75                 val = (1900LL+tm->tm_year) / 100;
  76                 goto number;
  77         case 'e':
  78                 def_pad = '_';
  79         case 'd':
  80                 val = tm->tm_mday;
  81                 goto number;
  82         case 'D':
  83                 fmt = "%m/%d/%y";
  84                 goto recu_strftime;
  85         case 'F':
  86                 fmt = "%Y-%m-%d";
  87                 goto recu_strftime;
  88         case 'g':
  89         case 'G':
  90                 val = tm->tm_year + 1900LL;
  91                 if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
  92                 else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
  93                 if (f=='g') val %= 100;
  94                 else width = 4;
  95                 goto number;
  96         case 'H':
  97                 val = tm->tm_hour;
  98                 goto number;
  99         case 'I':
 100                 val = tm->tm_hour;
 101                 if (!val) val = 12;
 102                 else if (val > 12) val -= 12;
 103                 goto number;
 104         case 'j':
 105                 val = tm->tm_yday+1;
 106                 width = 3;
 107                 goto number;
 108         case 'm':
 109                 val = tm->tm_mon+1;
 110                 goto number;
 111         case 'M':
 112                 val = tm->tm_min;
 113                 goto number;
 114         case 'n':
 115                 *l = 1;
 116                 return "\n";
 117         case 'p':
 118                 item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
 119                 goto nl_strcat;
 120         case 'r':
 121                 item = T_FMT_AMPM;
 122                 goto nl_strftime;
 123         case 'R':
 124                 fmt = "%H:%M";
 125                 goto recu_strftime;
 126         case 's':
 127                 val = __tm_to_secs(tm) - tm->__tm_gmtoff;
 128                 width = 1;
 129                 goto number;
 130         case 'S':
 131                 val = tm->tm_sec;
 132                 goto number;
 133         case 't':
 134                 *l = 1;
 135                 return "\t";
 136         case 'T':
 137                 fmt = "%H:%M:%S";
 138                 goto recu_strftime;
 139         case 'u':
 140                 val = tm->tm_wday ? tm->tm_wday : 7;
 141                 width = 1;
 142                 goto number;
 143         case 'U':
 144                 val = (tm->tm_yday + 7U - tm->tm_wday) / 7;
 145                 goto number;
 146         case 'W':
 147                 val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
 148                 goto number;
 149         case 'V':
 150                 val = week_num(tm);
 151                 goto number;
 152         case 'w':
 153                 val = tm->tm_wday;
 154                 width = 1;
 155                 goto number;
 156         case 'x':
 157                 item = D_FMT;
 158                 goto nl_strftime;
 159         case 'X':
 160                 item = T_FMT;
 161                 goto nl_strftime;
 162         case 'y':
 163                 val = (tm->tm_year + 1900LL) % 100;
 164                 if (val < 0) val = -val;
 165                 goto number;
 166         case 'Y':
 167                 val = tm->tm_year + 1900LL;
 168                 if (val >= 10000) {
 169                         *l = snprintf(*s, sizeof *s, "+%lld", val);
 170                         return *s;
 171                 }
 172                 width = 4;
 173                 goto number;
 174         case 'z':
 175                 if (tm->tm_isdst < 0) {
 176                         *l = 0;
 177                         return "";
 178                 }
 179                 *l = snprintf(*s, sizeof *s, "%+.4ld",
 180                         tm->__tm_gmtoff/3600*100 + tm->__tm_gmtoff%3600/60);
 181                 return *s;
 182         case 'Z':
 183                 if (tm->tm_isdst < 0) {
 184                         *l = 0;
 185                         return "";
 186                 }
 187                 fmt = __tm_to_tzname(tm);
 188                 goto string;
 189         case '%':
 190                 *l = 1;
 191                 return "%";
 192         default:
 193                 return 0;
 194         }
 195 number:
 196         switch (pad ? pad : def_pad) {
 197         case '-': *l = snprintf(*s, sizeof *s, "%lld", val); break;
 198         case '_': *l = snprintf(*s, sizeof *s, "%*lld", width, val); break;
 199         case '0':
 200         default:  *l = snprintf(*s, sizeof *s, "%0*lld", width, val); break;
 201         }
 202         return *s;
 203 nl_strcat:
 204         fmt = __nl_langinfo_l(item, loc);
 205 string:
 206         *l = strlen(fmt);
 207         return fmt;
 208 nl_strftime:
 209         fmt = __nl_langinfo_l(item, loc);
 210 recu_strftime:
 211         *l = __strftime_l(*s, sizeof *s, fmt, tm, loc);
 212         if (!*l) return 0;
 213         return *s;
 214 }
 215
 216 size_t __strftime_l(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm, locale_t loc)
 217 {
 218         size_t l, k;
 219         char buf[100];
 220         char *p;
 221         const char *t;
 222         int pad, plus;
 223         unsigned long width;
 224         for (l=0; l<n; f++) {
 225                 if (!*f) {
 226                         s[l] = 0;
 227                         return l;
 228                 }
 229                 if (*f != '%') {
 230                         s[l++] = *f;
 231                         continue;
 232                 }
 233                 f++;
 234                 pad = 0;
 235                 if (*f == '-' || *f == '_' || *f == '0') pad = *f++;
 236                 if ((plus = (*f == '+'))) f++;
 237                 if (isdigit(*f)) {
 238                         width = strtoul(f, &p, 10);
 239                 } else {
 240                         width = 0;
 241                         p = (void *)f;
 242                 }
 243                 if (*p == 'C' || *p == 'F' || *p == 'G' || *p == 'Y') {
 244                         if (!width && p!=f) width = 1;
 245                 } else {
 246                         width = 0;
 247                 }
 248                 f = p;
 249                 if (*f == 'E' || *f == 'O') f++;
 250                 t = __strftime_fmt_1(&buf, &k, *f, tm, loc, pad);
 251                 if (!t) break;
 252                 if (width) {
 253                         /* Trim off any sign and leading zeros, then
 254                          * count remaining digits to determine behavior
 255                          * for the + flag. */
 256                         if (*t=='+' || *t=='-') t++, k--;
 257                         for (; *t=='0' && t[1]-'0'<10U; t++, k--);
 258                         if (width < k) width = k;
 259                         size_t d;
 260                         for (d=0; t[d]-'0'<10U; d++);
 261                         if (tm->tm_year < -1900) {
 262                                 s[l++] = '-';
 263                                 width--;
 264                         } else if (plus && d+(width-k) >= (*p=='C'?3:5)) {
 265                                 s[l++] = '+';
 266                                 width--;
 267                         }
 268                         for (; width > k && l < n; width--)
 269                                 s[l++] = '0';
 270                 }
 271                 if (k > n-l) k = n-l;
 272                 memcpy(s+l, t, k);
 273                 l += k;
 274         }
 275         if (n) {
 276                 if (l==n) l=n-1;
 277                 s[l] = 0;
 278         }
 279         return 0;
 280 }
 281
 282 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
 283 {
 284         return __strftime_l(s, n, f, tm, CURRENT_LOCALE);
 285 }
 286
 287 weak_alias(__strftime_l, strftime_l);