newlib/libc/time/gmtime.c

   1 /*
   2  * gmtime.c
   3  * Original Author:     G. Haley
   4  *
   5  * Converts the calendar time pointed to by tim_p into a broken-down time
   6  * expressed as Greenwich Mean Time (GMT). Returns a pointer to a structure
   7  * containing the broken-down time, or a null pointer if GMT is not
   8  * available.
   9  */
  10
  11 /*
  12 FUNCTION
  13 <<gmtime>>---convert time to UTC traditional form
  14
  15 INDEX
  16         gmtime
  17 INDEX
  18         gmtime_r
  19
  20 SYNOPSIS
  21         #include <time.h>
  22         struct tm *gmtime(const time_t *<[clock]>);
  23         struct tm *gmtime_r(const time_t *<[clock]>, struct tm *<[res]>);
  24
  25 DESCRIPTION
  26 <<gmtime>> takes the time at <[clock]> representing the number
  27 of elapsed seconds since 00:00:00 on January 1, 1970, Universal
  28 Coordinated Time (UTC, also known in some countries as GMT,
  29 Greenwich Mean time) and converts it to a <<struct tm>>
  30 representation.
  31
  32 <<gmtime>> constructs the traditional time representation in static
  33 storage; each call to <<gmtime>> or <<localtime>> will overwrite the
  34 information generated by previous calls to either function.
  35
  36 RETURNS
  37 A pointer to the traditional time representation (<<struct tm>>).
  38
  39 PORTABILITY
  40 ANSI C requires <<gmtime>>.
  41
  42 <<gmtime>> requires no supporting OS subroutines.
  43 */
  44
  45 #include <stdlib.h>
  46 #include <time.h>
  47
  48 #define _GMT_OFFSET 0
  49
  50 #ifdef _REENT_THREAD_LOCAL
  51 _Thread_local struct __tm _tls_localtime_buf;
  52 #endif
  53
  54 #ifndef _REENT_ONLY
  55
  56 struct tm *
  57 gmtime (const time_t * tim_p)
  58 {
  59   struct _reent *reent = _REENT;
  60
  61   _REENT_CHECK_TM(reent);
  62   return gmtime_r (tim_p, (struct tm *)_REENT_TM(reent));
  63 }
  64
  65 #endif