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