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Member "asctime.c" (12 Jul 2022, 3611 Bytes) of package /linux/misc/tzcode2022g.tar.gz:

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    1 /* asctime and asctime_r a la POSIX and ISO C, except pad years before 1000.  */
    2 
    3 /*
    4 ** This file is in the public domain, so clarified as of
    5 ** 1996-06-05 by Arthur David Olson.
    6 */
    7 
    8 /*
    9 ** Avoid the temptation to punt entirely to strftime;
   10 ** the output of strftime is supposed to be locale specific
   11 ** whereas the output of asctime is supposed to be constant.
   12 */
   13 
   14 /*LINTLIBRARY*/
   15 
   16 #include "private.h"
   17 #include <stdio.h>
   18 
   19 /*
   20 ** All years associated with 32-bit time_t values are exactly four digits long;
   21 ** some years associated with 64-bit time_t values are not.
   22 ** Vintage programs are coded for years that are always four digits long
   23 ** and may assume that the newline always lands in the same place.
   24 ** For years that are less than four digits, we pad the output with
   25 ** leading zeroes to get the newline in the traditional place.
   26 ** The -4 ensures that we get four characters of output even if
   27 ** we call a strftime variant that produces fewer characters for some years.
   28 ** The ISO C and POSIX standards prohibit padding the year,
   29 ** but many implementations pad anyway; most likely the standards are buggy.
   30 */
   31 static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n";
   32 /*
   33 ** For years that are more than four digits we put extra spaces before the year
   34 ** so that code trying to overwrite the newline won't end up overwriting
   35 ** a digit within a year and truncating the year (operating on the assumption
   36 ** that no output is better than wrong output).
   37 */
   38 static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d     %s\n";
   39 
   40 enum { STD_ASCTIME_BUF_SIZE = 26 };
   41 /*
   42 ** Big enough for something such as
   43 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
   44 ** (two three-character abbreviations, five strings denoting integers,
   45 ** seven explicit spaces, two explicit colons, a newline,
   46 ** and a trailing NUL byte).
   47 ** The values above are for systems where an int is 32 bits and are provided
   48 ** as an example; the size expression below is a bound for the system at
   49 ** hand.
   50 */
   51 static char buf_asctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1];
   52 
   53 char *
   54 asctime_r(register const struct tm *timeptr, char *buf)
   55 {
   56     static const char   wday_name[][4] = {
   57         "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
   58     };
   59     static const char   mon_name[][4] = {
   60         "Jan", "Feb", "Mar", "Apr", "May", "Jun",
   61         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
   62     };
   63     register const char *   wn;
   64     register const char *   mn;
   65     char            year[INT_STRLEN_MAXIMUM(int) + 2];
   66     char result[sizeof buf_asctime];
   67 
   68     if (timeptr == NULL) {
   69         errno = EINVAL;
   70         return strcpy(buf, "??? ??? ?? ??:??:?? ????\n");
   71     }
   72     if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK)
   73         wn = "???";
   74     else    wn = wday_name[timeptr->tm_wday];
   75     if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR)
   76         mn = "???";
   77     else    mn = mon_name[timeptr->tm_mon];
   78     /*
   79     ** Use strftime's %Y to generate the year, to avoid overflow problems
   80     ** when computing timeptr->tm_year + TM_YEAR_BASE.
   81     ** Assume that strftime is unaffected by other out-of-range members
   82     ** (e.g., timeptr->tm_mday) when processing "%Y".
   83     */
   84     strftime(year, sizeof year, "%Y", timeptr);
   85     /*
   86     ** We avoid using snprintf since it's not available on all systems.
   87     */
   88     sprintf(result,
   89         ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B),
   90         wn, mn,
   91         timeptr->tm_mday, timeptr->tm_hour,
   92         timeptr->tm_min, timeptr->tm_sec,
   93         year);
   94     if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
   95         return strcpy(buf, result);
   96     else {
   97         errno = EOVERFLOW;
   98         return NULL;
   99     }
  100 }
  101 
  102 char *
  103 asctime(register const struct tm *timeptr)
  104 {
  105     return asctime_r(timeptr, buf_asctime);
  106 }