src/strftime.c

   1 /*
   2  * strftime.c
   3  *
   4  * Public-domain relatively quick-and-dirty implemenation of
   5  * ANSI library routine for System V Unix systems.
   6  *
   7  * It's written in old-style C for maximal portability.
   8  * However, since I'm used to prototypes, I've included them too.
   9  *
  10  * If you want stuff in the System V ascftime routine, add the SYSV_EXT define.
  11  * For stuff needed to implement the P1003.2 date command, add POSIX2_DATE.
  12  * For complete POSIX semantics, add POSIX_SEMANTICS.
  13  *
  14  * The code for %c, %x, and %X is my best guess as to what's "appropriate".
  15  * This version ignores LOCALE information.
  16  * It also doesn't worry about multi-byte characters.
  17  * So there.
  18  *
  19  * Arnold Robbins
  20  * January, February, March, 1991
  21  * Updated March 1992
  22  *
  23  * Fixes from ado@elsie.nci.nih.gov
  24  * February 1991
  25  *
  26  * Fixed compiler warnings from GCC
  27  * Olly Betts 2005-01-12
  28  *
  29  * Fix memory leak if realloc() fails
  30  * Olly Betts 2010-12-21
  31  *
  32  * Fix compilation error with GCC
  33  * Olly Betts 2010-12-21
  34  */
  35
  36 #include <stdio.h>
  37 #include <ctype.h>
  38 #include <string.h>
  39 #include <time.h>
  40 #include <sys/types.h>
  41
  42 #ifndef __STDC__
  43 #define const   /**/
  44
  45 extern void *malloc();
  46 extern void *realloc();
  47 extern void free();
  48 extern void tzset();
  49 extern char *strchr();
  50 extern char *getenv();
  51 static int weeknumber();
  52 #else
  53 #include <stdlib.h>
  54 extern void tzset(void);
  55 static int weeknumber(const struct tm *timeptr, int firstweekday);
  56 #endif
  57
  58 #ifdef __GNUC__
  59 #define inline  __inline__
  60 #else
  61 #define inline  /**/
  62 #endif
  63
  64 #define range(low, item, hi)    max(low, min(item, hi))
  65
  66 extern char *tzname[2];
  67 extern int daylight;
  68
  69 #define SYSV_EXT        1       /* stuff in System V ascftime routine */
  70 #define POSIX2_DATE     1       /* stuff in Posix 1003.2 date command */
  71 #define VMS_EXT         1       /* include %V for VMS date format */
  72 #define POSIX_SEMANTICS 1       /* call tzset() if TZ changes */
  73
  74 #if defined(POSIX2_DATE) && ! defined(SYSV_EXT)
  75 #define SYSV_EXT        1
  76 #endif
  77
  78 /* min --- return minimum of two numbers */
  79
  80 #ifndef __STDC__
  81 static inline int
  82 min(a, b)
  83 int a, b;
  84 #else
  85 static inline int
  86 min(int a, int b)
  87 #endif
  88 {
  89         return (a < b ? a : b);
  90 }
  91
  92 /* max --- return maximum of two numbers */
  93
  94 #ifndef __STDC__
  95 static inline int
  96 max(a, b)
  97 int a, b;
  98 #else
  99 static inline int
 100 max(int a, int b)
 101 #endif
 102 {
 103         return (a > b ? a : b);
 104 }
 105
 106 /* strftime --- produce formatted time */
 107
 108 #ifndef __STDC__
 109 size_t
 110 strftime(s, maxsize, format, timeptr)
 111 char *s;
 112 size_t maxsize;
 113 const char *format;
 114 const struct tm *timeptr;
 115 #else
 116 size_t
 117 strftime(char *s, size_t maxsize, const char *format, const struct tm *timeptr)
 118 #endif
 119 {
 120         char *endp = s + maxsize;
 121         char *start = s;
 122         char tbuf[100];
 123         int i;
 124         static short first = 1;
 125         static char *savetz = NULL;
 126         static int savetzlen = 0;
 127         char *tz;
 128         int tzlen;
 129
 130         /* various tables, useful in North America */
 131         static const char *days_a[] = {
 132                 "Sun", "Mon", "Tue", "Wed",
 133                 "Thu", "Fri", "Sat",
 134         };
 135         static const char *days_l[] = {
 136                 "Sunday", "Monday", "Tuesday", "Wednesday",
 137                 "Thursday", "Friday", "Saturday",
 138         };
 139         static const char *months_a[] = {
 140                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
 141                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
 142         };
 143         static const char *months_l[] = {
 144                 "January", "February", "March", "April",
 145                 "May", "June", "July", "August", "September",
 146                 "October", "November", "December",
 147         };
 148         static const char *ampm[] = { "AM", "PM", };
 149
 150         if (s == NULL || format == NULL || timeptr == NULL || maxsize == 0)
 151                 return 0;
 152
 153         if (strchr(format, '%') == NULL && strlen(format) + 1 >= maxsize)
 154                 return 0;
 155
 156 #ifndef POSIX_SEMANTICS
 157         if (first) {
 158                 tzset();
 159                 first = 0;
 160         }
 161 #else   /* POSIX_SEMANTICS */
 162         tz = getenv("TZ");
 163         tzlen = strlen(tz);
 164         if (first) {
 165                 if (tz != NULL) {
 166                         savetz = (char *) malloc(tzlen + 1);
 167                         if (savetz != NULL) {
 168                                 savetzlen = tzlen + 1;
 169                                 strcpy(savetz, tz);
 170                         }
 171                 }
 172                 tzset();
 173                 first = 0;
 174         }
 175         /* if we have a saved TZ, and it is different, recapture and reset */
 176         if (tz && savetz && (tz[0] != savetz[0] || strcmp(tz, savetz) != 0)) {
 177                 i = strlen(tz) + 1;
 178                 if (i > savetzlen) {
 179                         char * newsavetz = (char *) realloc(savetz, i);
 180                         if (newsavetz) {
 181                                 savetzlen = i;
 182                                 strcpy(newsavetz, tz);
 183                         } else {
 184                                 free(savetz);
 185                         }
 186                         savetz = newsavetz;
 187                 } else
 188                         strcpy(savetz, tz);
 189                 tzset();
 190         }
 191 #endif /* POSIX_SEMANTICS */
 192
 193         for (; *format && s < endp - 1; format++) {
 194                 tbuf[0] = '\0';
 195                 if (*format != '%') {
 196                         *s++ = *format;
 197                         continue;
 198                 }
 199         again:
 200                 switch (*++format) {
 201                 case '\0':
 202                         *s++ = '%';
 203                         goto out;
 204
 205                 case '%':
 206                         *s++ = '%';
 207                         continue;
 208
 209                 case 'a':       /* abbreviated weekday name */
 210                         if (timeptr->tm_wday < 0 || timeptr->tm_wday > 6)
 211                                 strcpy(tbuf, "?");
 212                         else
 213                                 strcpy(tbuf, days_a[timeptr->tm_wday]);
 214                         break;
 215
 216                 case 'A':       /* full weekday name */
 217                         if (timeptr->tm_wday < 0 || timeptr->tm_wday > 6)
 218                                 strcpy(tbuf, "?");
 219                         else
 220                                 strcpy(tbuf, days_l[timeptr->tm_wday]);
 221                         break;
 222
 223 #ifdef SYSV_EXT
 224                 case 'h':       /* abbreviated month name */
 225 #endif
 226                 case 'b':       /* abbreviated month name */
 227                         if (timeptr->tm_mon < 0 || timeptr->tm_mon > 11)
 228                                 strcpy(tbuf, "?");
 229                         else
 230                                 strcpy(tbuf, months_a[timeptr->tm_mon]);
 231                         break;
 232
 233                 case 'B':       /* full month name */
 234                         if (timeptr->tm_mon < 0 || timeptr->tm_mon > 11)
 235                                 strcpy(tbuf, "?");
 236                         else
 237                                 strcpy(tbuf, months_l[timeptr->tm_mon]);
 238                         break;
 239
 240                 case 'c':       /* appropriate date and time representation */
 241                         sprintf(tbuf, "%s %s %2d %02d:%02d:%02d %d",
 242                                 days_a[range(0, timeptr->tm_wday, 6)],
 243                                 months_a[range(0, timeptr->tm_mon, 11)],
 244                                 range(1, timeptr->tm_mday, 31),
 245                                 range(0, timeptr->tm_hour, 23),
 246                                 range(0, timeptr->tm_min, 59),
 247                                 range(0, timeptr->tm_sec, 61),
 248                                 timeptr->tm_year + 1900);
 249                         break;
 250
 251                 case 'd':       /* day of the month, 01 - 31 */
 252                         i = range(1, timeptr->tm_mday, 31);
 253                         sprintf(tbuf, "%02d", i);
 254                         break;
 255
 256                 case 'H':       /* hour, 24-hour clock, 00 - 23 */
 257                         i = range(0, timeptr->tm_hour, 23);
 258                         sprintf(tbuf, "%02d", i);
 259                         break;
 260
 261                 case 'I':       /* hour, 12-hour clock, 01 - 12 */
 262                         i = range(0, timeptr->tm_hour, 23);
 263                         if (i == 0)
 264                                 i = 12;
 265                         else if (i > 12)
 266                                 i -= 12;
 267                         sprintf(tbuf, "%02d", i);
 268                         break;
 269
 270                 case 'j':       /* day of the year, 001 - 366 */
 271                         sprintf(tbuf, "%03d", timeptr->tm_yday + 1);
 272                         break;
 273
 274                 case 'm':       /* month, 01 - 12 */
 275                         i = range(0, timeptr->tm_mon, 11);
 276                         sprintf(tbuf, "%02d", i + 1);
 277                         break;
 278
 279                 case 'M':       /* minute, 00 - 59 */
 280                         i = range(0, timeptr->tm_min, 59);
 281                         sprintf(tbuf, "%02d", i);
 282                         break;
 283
 284                 case 'p':       /* am or pm based on 12-hour clock */
 285                         i = range(0, timeptr->tm_hour, 23);
 286                         if (i < 12)
 287                                 strcpy(tbuf, ampm[0]);
 288                         else
 289                                 strcpy(tbuf, ampm[1]);
 290                         break;
 291
 292                 case 'S':       /* second, 00 - 61 */
 293                         i = range(0, timeptr->tm_sec, 61);
 294                         sprintf(tbuf, "%02d", i);
 295                         break;
 296
 297                 case 'U':       /* week of year, Sunday is first day of week */
 298                         sprintf(tbuf, "%d", weeknumber(timeptr, 0));
 299                         break;
 300
 301                 case 'w':       /* weekday, Sunday == 0, 0 - 6 */
 302                         i = range(0, timeptr->tm_wday, 6);
 303                         sprintf(tbuf, "%d", i);
 304                         break;
 305
 306                 case 'W':       /* week of year, Monday is first day of week */
 307                         sprintf(tbuf, "%d", weeknumber(timeptr, 1));
 308                         break;
 309
 310                 case 'x':       /* appropriate date representation */
 311                         sprintf(tbuf, "%s %s %2d %d",
 312                                 days_a[range(0, timeptr->tm_wday, 6)],
 313                                 months_a[range(0, timeptr->tm_mon, 11)],
 314                                 range(1, timeptr->tm_mday, 31),
 315                                 timeptr->tm_year + 1900);
 316                         break;
 317
 318                 case 'X':       /* appropriate time representation */
 319                         sprintf(tbuf, "%02d:%02d:%02d",
 320                                 range(0, timeptr->tm_hour, 23),
 321                                 range(0, timeptr->tm_min, 59),
 322                                 range(0, timeptr->tm_sec, 61));
 323                         break;
 324
 325                 case 'y':       /* year without a century, 00 - 99 */
 326                         i = timeptr->tm_year % 100;
 327                         sprintf(tbuf, "%d", i);
 328                         break;
 329
 330                 case 'Y':       /* year with century */
 331                         sprintf(tbuf, "%d", 1900 + timeptr->tm_year);
 332                         break;
 333
 334                 case 'Z':       /* time zone name or abbrevation */
 335                         i = 0;
 336                         if (daylight && timeptr->tm_isdst)
 337                                 i = 1;
 338                         strcpy(tbuf, tzname[i]);
 339                         break;
 340
 341 #ifdef SYSV_EXT
 342                 case 'n':       /* same as \n */
 343                         tbuf[0] = '\n';
 344                         tbuf[1] = '\0';
 345                         break;
 346
 347                 case 't':       /* same as \t */
 348                         tbuf[0] = '\t';
 349                         tbuf[1] = '\0';
 350                         break;
 351
 352                 case 'D':       /* date as %m/%d/%y */
 353                         strftime(tbuf, sizeof tbuf, "%m/%d/%y", timeptr);
 354                         break;
 355
 356                 case 'e':       /* day of month, blank padded */
 357                         sprintf(tbuf, "%2d", range(1, timeptr->tm_mday, 31));
 358                         break;
 359
 360                 case 'r':       /* time as %I:%M:%S %p */
 361                         strftime(tbuf, sizeof tbuf, "%I:%M:%S %p", timeptr);
 362                         break;
 363
 364                 case 'R':       /* time as %H:%M */
 365                         strftime(tbuf, sizeof tbuf, "%H:%M", timeptr);
 366                         break;
 367
 368                 case 'T':       /* time as %H:%M:%S */
 369                         strftime(tbuf, sizeof tbuf, "%H:%M:%S", timeptr);
 370                         break;
 371 #endif
 372
 373
 374 #ifdef VMS_EXT
 375                 case 'V':       /* date as dd-bbb-YYYY */
 376                         sprintf(tbuf, "%2d-%3.3s-%4d",
 377                                 range(1, timeptr->tm_mday, 31),
 378                                 months_a[range(0, timeptr->tm_mon, 11)],
 379                                 timeptr->tm_year + 1900);
 380                         for (i = 3; i < 6; i++)
 381                                 if (islower(tbuf[i]))
 382                                         tbuf[i] = toupper(tbuf[i]);
 383                         break;
 384 #endif
 385
 386
 387 #ifdef POSIX2_DATE
 388                 case 'C':
 389                         sprintf(tbuf, "%02d", (timeptr->tm_year + 1900) / 100);
 390                         break;
 391
 392
 393                 case 'E':
 394                 case 'O':
 395                         /* POSIX locale extensions, ignored for now */
 396                         goto again;
 397 #endif
 398                 default:
 399                         tbuf[0] = '%';
 400                         tbuf[1] = *format;
 401                         tbuf[2] = '\0';
 402                         break;
 403                 }
 404                 i = strlen(tbuf);
 405                 if (i) {
 406                         if (s + i < endp - 1) {
 407                                 strcpy(s, tbuf);
 408                                 s += i;
 409                         } else
 410                                 return 0;
 411                 }
 412         }
 413 out:
 414         if (s < endp && *format == '\0') {
 415                 *s = '\0';
 416                 return (s - start);
 417         } else
 418                 return 0;
 419 }
 420
 421 /* weeknumber --- figure how many weeks into the year */
 422
 423 /* With thanks and tip of the hatlo to ado@elsie.nci.nih.gov */
 424 /* Modified byMichal Jaegermann <audfax!emory!vm.ucs.UAlberta.CA!NTOMCZAK> */
 425
 426 #ifndef __STDC__
 427 static int
 428 weeknumber(timeptr, firstweekday)
 429 const struct tm *timeptr;
 430 int firstweekday;
 431 #else
 432 static int
 433 weeknumber(const struct tm *timeptr, int firstweekday)
 434 #endif
 435 /*
 436  * firstweekday is 0 if starting in Sunday, non-zero if in Monday
 437  */
 438 {
 439     return (timeptr->tm_yday - timeptr->tm_wday +
 440             (firstweekday ? (timeptr->tm_wday ? 8 : 1) : 7)) / 7;
 441 }