lib/libc/time/asctime.c

   1 /*      $NetBSD: asctime.c,v 1.18 2012/10/28 17:11:33 christos Exp $    */
   2
   3 /*
   4 ** This file is in the public domain, so clarified as of
   5 ** 1996-06-05 by Arthur David Olson.
   6 */
   7
   8 /*
   9 ** Avoid the temptation to punt entirely to strftime;
  10 ** the output of strftime is supposed to be locale specific
  11 ** whereas the output of asctime is supposed to be constant.
  12 */
  13
  14 #include <sys/cdefs.h>
  15 #if defined(LIBC_SCCS) && !defined(lint)
  16 #if 0
  17 static char     elsieid[] = "@(#)asctime.c      8.5";
  18 #else
  19 __RCSID("$NetBSD: asctime.c,v 1.18 2012/10/28 17:11:33 christos Exp $");
  20 #endif
  21 #endif /* LIBC_SCCS and not lint */
  22
  23 /*LINTLIBRARY*/
  24
  25 #include "namespace.h"
  26 #include "private.h"
  27 #include "tzfile.h"
  28
  29 #ifdef __weak_alias
  30 __weak_alias(asctime_r,_asctime_r)
  31 #endif
  32
  33 /*
  34 ** Some systems only handle "%.2d"; others only handle "%02d";
  35 ** "%02.2d" makes (most) everybody happy.
  36 ** At least some versions of gcc warn about the %02.2d;
  37 ** we conditionalize below to avoid the warning.
  38 */
  39 /*
  40 ** All years associated with 32-bit time_t values are exactly four digits long;
  41 ** some years associated with 64-bit time_t values are not.
  42 ** Vintage programs are coded for years that are always four digits long
  43 ** and may assume that the newline always lands in the same place.
  44 ** For years that are less than four digits, we pad the output with
  45 ** leading zeroes to get the newline in the traditional place.
  46 ** The -4 ensures that we get four characters of output even if
  47 ** we call a strftime variant that produces fewer characters for some years.
  48 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
  49 ** but many implementations pad anyway; most likely the standards are buggy.
  50 */
  51 #ifdef __GNUC__
  52 #define ASCTIME_FMT     "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
  53 #else /* !defined __GNUC__ */
  54 #define ASCTIME_FMT     "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
  55 #endif /* !defined __GNUC__ */
  56 /*
  57 ** For years that are more than four digits we put extra spaces before the year
  58 ** so that code trying to overwrite the newline won't end up overwriting
  59 ** a digit within a year and truncating the year (operating on the assumption
  60 ** that no output is better than wrong output).
  61 */
  62 #ifdef __GNUC__
  63 #define ASCTIME_FMT_B   "%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
  64 #else /* !defined __GNUC__ */
  65 #define ASCTIME_FMT_B   "%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
  66 #endif /* !defined __GNUC__ */
  67
  68 #define STD_ASCTIME_BUF_SIZE    26
  69 /*
  70 ** Big enough for something such as
  71 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
  72 ** (two three-character abbreviations, five strings denoting integers,
  73 ** seven explicit spaces, two explicit colons, a newline,
  74 ** and a trailing ASCII nul).
  75 ** The values above are for systems where an int is 32 bits and are provided
  76 ** as an example; the define below calculates the maximum for the system at
  77 ** hand.
  78 */
  79 #define MAX_ASCTIME_BUF_SIZE    (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
  80
  81 static char     buf_asctime[MAX_ASCTIME_BUF_SIZE];
  82
  83 /*
  84 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
  85 */
  86
  87 char *
  88 asctime_r(const struct tm *timeptr, char *buf)
  89 {
  90         static const char       wday_name[][3] = {
  91                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  92         };
  93         static const char       mon_name[][3] = {
  94                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  95                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  96         };
  97         const char *    wn;
  98         const char *    mn;
  99         char                    year[INT_STRLEN_MAXIMUM(int) + 2];
 100         char                    result[MAX_ASCTIME_BUF_SIZE];
 101
 102         if (timeptr == NULL) {
 103                 errno = EINVAL;
 104                 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
 105         }
 106         if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
 107                 wn = "???";
 108         else    wn = wday_name[timeptr->tm_wday];
 109         if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
 110                 mn = "???";
 111         else    mn = mon_name[timeptr->tm_mon];
 112         /*
 113         ** Use strftime's %Y to generate the year, to avoid overflow problems
 114         ** when computing timeptr->tm_year + TM_YEAR_BASE.
 115         ** Assume that strftime is unaffected by other out-of-range members
 116         ** (e.g., timeptr->tm_mday) when processing "%Y".
 117         */
 118         (void) strftime(year, sizeof year, "%Y", timeptr);
 119         (void) snprintf(result,
 120                 sizeof(result),
 121                 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
 122                 wn, mn,
 123                 timeptr->tm_mday, timeptr->tm_hour,
 124                 timeptr->tm_min, timeptr->tm_sec,
 125                 year);
 126         if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
 127                 return strcpy(buf, result);
 128         else {
 129 #ifdef EOVERFLOW
 130                 errno = EOVERFLOW;
 131 #else /* !defined EOVERFLOW */
 132                 errno = EINVAL;
 133 #endif /* !defined EOVERFLOW */
 134                 return NULL;
 135         }
 136 }
 137
 138 /*
 139 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
 140 */
 141
 142 char *
 143 asctime(const struct tm *timeptr)
 144 {
 145         return asctime_r(timeptr, buf_asctime);
 146 }