git.sur5r.net Git - cc65/blob - libsrc/common/localtime.c

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                localtime.c                                */
   4 /*                                                                           */
   5 /*            Convert calendar time into broken down local time              */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2002      Ullrich von Bassewitz                                       */
  10 /*               Wacholderweg 14                                             */
  11 /*               D-70597 Stuttgart                                           */
  12 /* EMail:        uz@musoftware.de                                            */
  13 /*                                                                           */
  14 /*                                                                           */
  15 /* This software is provided 'as-is', without any expressed or implied       */
  16 /* warranty.  In no event will the authors be held liable for any damages    */
  17 /* arising from the use of this software.                                    */
  18 /*                                                                           */
  19 /* Permission is granted to anyone to use this software for any purpose,     */
  20 /* including commercial applications, and to alter it and redistribute it    */
  21 /* freely, subject to the following restrictions:                            */
  22 /*                                                                           */
  23 /* 1. The origin of this software must not be misrepresented; you must not   */
  24 /*    claim that you wrote the original software. If you use this software   */
  25 /*    in a product, an acknowledgment in the product documentation would be  */
  26 /*    appreciated but is not required.                                       */
  27 /* 2. Altered source versions must be plainly marked as such, and must not   */
  28 /*    be misrepresented as being the original software.                      */
  29 /* 3. This notice may not be removed or altered from any source              */
  30 /*    distribution.                                                          */
  31 /*                                                                           */
  32 /*****************************************************************************/
  33
  34
  35
  36 #include <time.h>
  37
  38
  39
  40 /*****************************************************************************/
  41 /*                                   Code                                    */
  42 /*****************************************************************************/
  43
  44
  45
  46 struct tm* __fastcall__ localtime (const time_t* timep)
  47 {
  48     static struct tm timebuf;
  49     time_t t;
  50
  51     /* Check the argument */
  52     if (timep == 0 || (long) (t = *timep) < 0) {
  53         /* Invalid arg */
  54         return 0;
  55     }
  56
  57     /* Since our ints are just 16 bits, split the given time into seconds,
  58     ** hours and days. Each of the values will fit in a 16 bit variable.
  59     ** The mktime routine will then do the rest.
  60     */
  61     timebuf.tm_sec  = t % 3600;
  62     timebuf.tm_min  = 0;
  63     timebuf.tm_hour = (t / 3600) % 24;
  64     timebuf.tm_mday = (t / (3600UL * 24UL)) + 1;
  65     timebuf.tm_mon  = 0;
  66     timebuf.tm_year = 70;       /* Base value is 1/1/1970 */
  67
  68     /* Call mktime to do the final conversion */
  69     mktime (&timebuf);
  70
  71     /* Return the result */
  72     return &timebuf;
  73 }
  74
  75