lib/libc/stdtime/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 ** @(#)asctime.c        8.5
  12 ** $FreeBSD: src/lib/libc/stdtime/asctime.c,v 1.7.6.1 2001/03/05 11:37:20 obrien Exp $
  13 */
  14 /*LINTLIBRARY*/
  15
  16 #include "namespace.h"
  17 #include "private.h"
  18 #include "un-namespace.h"
  19 #include "tzfile.h"
  20
  21 /*
  22 ** Some systems only handle "%.2d"; others only handle "%02d";
  23 ** "%02.2d" makes (most) everybody happy.
  24 ** At least some versions of gcc warn about the %02.2d;
  25 ** we conditionalize below to avoid the warning.
  26 */
  27 /*
  28 ** All years associated with 32-bit time_t values are exactly four digits long;
  29 ** some years associated with 64-bit time_t values are not.
  30 ** Vintage programs are coded for years that are always four digits long
  31 ** and may assume that the newline always lands in the same place.
  32 ** For years that are less than four digits, we pad the output with
  33 ** leading zeroes to get the newline in the traditional place.
  34 ** The -4 ensures that we get four characters of output even if
  35 ** we call a strftime variant that produces fewer characters for some years.
  36 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
  37 ** but many implementations pad anyway; most likely the standards are buggy.
  38 */
  39 #ifdef __GNUC__
  40 #define ASCTIME_FMT     "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
  41 #else /* !defined __GNUC__ */
  42 #define ASCTIME_FMT     "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
  43 #endif /* !defined __GNUC__ */
  44 /*
  45 ** For years that are more than four digits we put extra spaces before the year
  46 ** so that code trying to overwrite the newline won't end up overwriting
  47 ** a digit within a year and truncating the year (operating on the assumption
  48 ** that no output is better than wrong output).
  49 */
  50 #ifdef __GNUC__
  51 #define ASCTIME_FMT_B   "%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
  52 #else /* !defined __GNUC__ */
  53 #define ASCTIME_FMT_B   "%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
  54 #endif /* !defined __GNUC__ */
  55
  56 #define STD_ASCTIME_BUF_SIZE    26
  57 /*
  58 ** Big enough for something such as
  59 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
  60 ** (two three-character abbreviations, five strings denoting integers,
  61 ** seven explicit spaces, two explicit colons, a newline,
  62 ** and a trailing ASCII nul).
  63 ** The values above are for systems where an int is 32 bits and are provided
  64 ** as an example; the define below calculates the maximum for the system at
  65 ** hand.
  66 */
  67 #define MAX_ASCTIME_BUF_SIZE    (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
  68
  69 static char     buf_asctime[MAX_ASCTIME_BUF_SIZE];
  70
  71 /*
  72 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
  73 */
  74
  75
  76 char *
  77 asctime_r(const struct tm *timeptr, char *buf)
  78 {
  79         static const char       wday_name[][3] = {
  80                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  81         };
  82         static const char       mon_name[][3] = {
  83                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  84                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  85         };
  86         char            year[INT_STRLEN_MAXIMUM(int) + 2];
  87         char            result[MAX_ASCTIME_BUF_SIZE];
  88         const char *    wn;
  89         const char *    mn;
  90
  91         if (timeptr == NULL) {
  92                 errno = EINVAL;
  93                 return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
  94         }
  95         if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
  96                 wn = "???";
  97         else    wn = wday_name[timeptr->tm_wday];
  98         if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
  99                 mn = "???";
 100         else    mn = mon_name[timeptr->tm_mon];
 101         /*
 102         ** Use strftime's %Y to generate the year, to avoid overflow problems
 103         ** when computing timeptr->tm_year + TM_YEAR_BASE.
 104         ** Assume that strftime is unaffected by other out-of-range members
 105         ** (e.g., timeptr->tm_mday) when processing "%Y".
 106         */
 107         strftime(year, sizeof year, "%Y", timeptr);
 108         snprintf(result, sizeof result,
 109                 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
 110                 wn, mn,
 111                 timeptr->tm_mday, timeptr->tm_hour,
 112                 timeptr->tm_min, timeptr->tm_sec,
 113                 year);
 114         if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) {
 115                 return strcpy(buf, result);
 116         } else {
 117                 errno = EOVERFLOW;
 118                 return NULL;
 119         }
 120 }
 121
 122 /*
 123 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
 124 */
 125
 126 char *
 127 asctime(const struct tm *timeptr)
 128 {
 129         return asctime_r(timeptr, buf_asctime);
 130 }