commands/zoneinfo/asctime.c

   1 /*
   2 ** This file is in the public domain, so clarified as of
   3 ** 1996-06-05 by Arthur David Olson.
   4 */
   5
   6 /*
   7 ** Avoid the temptation to punt entirely to strftime;
   8 ** the output of strftime is supposed to be locale specific
   9 ** whereas the output of asctime is supposed to be constant.
  10 */
  11
  12 #ifndef lint
  13 #ifndef NOID
  14 static char     elsieid[] = "@(#)asctime.c      7.32";
  15 #endif /* !defined NOID */
  16 #endif /* !defined lint */
  17
  18 /*LINTLIBRARY*/
  19
  20 #include "private.h"
  21 #include "tzfile.h"
  22
  23 /*
  24 ** Some systems only handle "%.2d"; others only handle "%02d";
  25 ** "%02.2d" makes (most) everybody happy.
  26 ** At least some versions of gcc warn about the %02.2d; ignore the warning.
  27 */
  28 /*
  29 ** All years associated with 32-bit time_t values are exactly four digits long;
  30 ** some years associated with 64-bit time_t values are not.
  31 ** Vintage programs are coded for years that are always four digits long
  32 ** and may assume that the newline always lands in the same place.
  33 ** For years that are less than four digits, we pad the output with
  34 ** leading zeroes to get the newline in the traditional place.
  35 ** The -4 ensures that we get four characters of output even if
  36 ** we call a strftime variant that produces fewer characters for some years.
  37 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
  38 ** but many implementations pad anyway; most likely the standards are buggy.
  39 */
  40 #define ASCTIME_FMT     "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
  41 /*
  42 ** For years that are more than four digits we put extra spaces before the year
  43 ** so that code trying to overwrite the newline won't end up overwriting
  44 ** a digit within a year and truncating the year (operating on the assumption
  45 ** that no output is better than wrong output).
  46 */
  47 #define ASCTIME_FMT_B   "%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
  48
  49 #define STD_ASCTIME_BUF_SIZE    26
  50 /*
  51 ** Big enough for something such as
  52 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
  53 ** (two three-character abbreviations, five strings denoting integers,
  54 ** seven explicit spaces, two explicit colons, a newline,
  55 ** and a trailing ASCII nul).
  56 ** The values above are for systems where an int is 32 bits and are provided
  57 ** as an example; the define below calculates the maximum for the system at
  58 ** hand.
  59 */
  60 #define MAX_ASCTIME_BUF_SIZE    (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
  61
  62 static char     buf_asctime[MAX_ASCTIME_BUF_SIZE];
  63
  64 /*
  65 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
  66 */
  67
  68 char *
  69 asctime_r(timeptr, buf)
  70 register const struct tm *      timeptr;
  71 char *                          buf;
  72 {
  73         static const char       wday_name[][3] = {
  74                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  75         };
  76         static const char       mon_name[][3] = {
  77                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  78                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  79         };
  80         register const char *   wn;
  81         register const char *   mn;
  82         char                    year[INT_STRLEN_MAXIMUM(int) + 2];
  83         char                    result[MAX_ASCTIME_BUF_SIZE];
  84
  85         if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
  86                 wn = "???";
  87         else    wn = wday_name[timeptr->tm_wday];
  88         if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
  89                 mn = "???";
  90         else    mn = mon_name[timeptr->tm_mon];
  91         /*
  92         ** Use strftime's %Y to generate the year, to avoid overflow problems
  93         ** when computing timeptr->tm_year + TM_YEAR_BASE.
  94         ** Assume that strftime is unaffected by other out-of-range members
  95         ** (e.g., timeptr->tm_mday) when processing "%Y".
  96         */
  97         (void) strftime(year, sizeof year, "%Y", timeptr);
  98         /*
  99         ** We avoid using snprintf since it's not available on all systems.
 100         */
 101         (void) sprintf(result,
 102                 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
 103                 wn, mn,
 104                 timeptr->tm_mday, timeptr->tm_hour,
 105                 timeptr->tm_min, timeptr->tm_sec,
 106                 year);
 107         if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) {
 108                 (void) strcpy(buf, result);
 109                 return buf;
 110         } else {
 111 #ifdef EOVERFLOW
 112                 errno = EOVERFLOW;
 113 #else /* !defined EOVERFLOW */
 114                 errno = EINVAL;
 115 #endif /* !defined EOVERFLOW */
 116                 return NULL;
 117         }
 118 }
 119
 120 /*
 121 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
 122 */
 123
 124 char *
 125 asctime(timeptr)
 126 register const struct tm *      timeptr;
 127 {
 128         return asctime_r(timeptr, buf_asctime);
 129 }