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      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 }
    139