icuSources/tools/tzcode/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      8.2";
  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;
  27 ** we conditionalize below to avoid the warning.
  28 */
  29 /*
  30 ** All years associated with 32-bit time_t values are exactly four digits long;
  31 ** some years associated with 64-bit time_t values are not.
  32 ** Vintage programs are coded for years that are always four digits long
  33 ** and may assume that the newline always lands in the same place.
  34 ** For years that are less than four digits, we pad the output with
  35 ** leading zeroes to get the newline in the traditional place.
  36 ** The -4 ensures that we get four characters of output even if
  37 ** we call a strftime variant that produces fewer characters for some years.
  38 ** The ISO C 1999 and POSIX 1003.1-2004 standards prohibit padding the year,
  39 ** but many implementations pad anyway; most likely the standards are buggy.
  40 */
  41 #ifdef __GNUC__
  42 #define ASCTIME_FMT     "%.3s %.3s%3d %2.2d:%2.2d:%2.2d %-4s\n"
  43 #else /* !defined __GNUC__ */
  44 #define ASCTIME_FMT     "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4s\n"
  45 #endif /* !defined __GNUC__ */
  46 /*
  47 ** For years that are more than four digits we put extra spaces before the year
  48 ** so that code trying to overwrite the newline won't end up overwriting
  49 ** a digit within a year and truncating the year (operating on the assumption
  50 ** that no output is better than wrong output).
  51 */
  52 #ifdef __GNUC__
  53 #define ASCTIME_FMT_B   "%.3s %.3s%3d %2.2d:%2.2d:%2.2d     %s\n"
  54 #else /* !defined __GNUC__ */
  55 #define ASCTIME_FMT_B   "%.3s %.3s%3d %02.2d:%02.2d:%02.2d     %s\n"
  56 #endif /* !defined __GNUC__ */
  57
  58 #define STD_ASCTIME_BUF_SIZE    26
  59 /*
  60 ** Big enough for something such as
  61 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
  62 ** (two three-character abbreviations, five strings denoting integers,
  63 ** seven explicit spaces, two explicit colons, a newline,
  64 ** and a trailing ASCII nul).
  65 ** The values above are for systems where an int is 32 bits and are provided
  66 ** as an example; the define below calculates the maximum for the system at
  67 ** hand.
  68 */
  69 #define MAX_ASCTIME_BUF_SIZE    (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
  70
  71 static char     buf_asctime[MAX_ASCTIME_BUF_SIZE];
  72
  73 /*
  74 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
  75 */
  76
  77 char *
  78 asctime_r(timeptr, buf)
  79 register const struct tm *      timeptr;
  80 char *                          buf;
  81 {
  82         static const char       wday_name[][3] = {
  83                 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  84         };
  85         static const char       mon_name[][3] = {
  86                 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  87                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  88         };
  89         register const char *   wn;
  90         register const char *   mn;
  91         char                    year[INT_STRLEN_MAXIMUM(int) + 2];
  92         char                    result[MAX_ASCTIME_BUF_SIZE];
  93
  94         if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
  95                 wn = "???";
  96         else    wn = wday_name[timeptr->tm_wday];
  97         if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
  98                 mn = "???";
  99         else    mn = mon_name[timeptr->tm_mon];
 100         /*
 101         ** Use strftime's %Y to generate the year, to avoid overflow problems
 102         ** when computing timeptr->tm_year + TM_YEAR_BASE.
 103         ** Assume that strftime is unaffected by other out-of-range members
 104         ** (e.g., timeptr->tm_mday) when processing "%Y".
 105         */
 106         (void) strftime(year, sizeof year, "%Y", timeptr);
 107         /*
 108         ** We avoid using snprintf since it's not available on all systems.
 109         */
 110         (void) sprintf(result,
 111                 ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
 112                 wn, mn,
 113                 timeptr->tm_mday, timeptr->tm_hour,
 114                 timeptr->tm_min, timeptr->tm_sec,
 115                 year);
 116         if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime) {
 117                 (void) strcpy(buf, result);
 118                 return buf;
 119         } else {
 120 #ifdef EOVERFLOW
 121                 errno = EOVERFLOW;
 122 #else /* !defined EOVERFLOW */
 123                 errno = EINVAL;
 124 #endif /* !defined EOVERFLOW */
 125                 return NULL;
 126         }
 127 }
 128
 129 /*
 130 ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition.
 131 */
 132
 133 char *
 134 asctime(timeptr)
 135 register const struct tm *      timeptr;
 136 {
 137         return asctime_r(timeptr, buf_asctime);
 138 }