fastjar/dostime.c

   1 /* dostime.c - convert dos time to/from time_t.
   2
   3    Copyright (C) 2002 Free Software Foundation
   4
   5   This program is free software; you can redistribute it and/or
   6   modify it under the terms of the GNU General Public License
   7   as published by the Free Software Foundation; either version 2
   8   of the License, or (at your option) any later version.
   9
  10   This program is distributed in the hope that it will be useful,
  11   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13   GNU General Public License for more details.
  14
  15   You should have received a copy of the GNU General Public License
  16   along with this program; if not, write to the Free Software
  17   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18 */
  19
  20 #include <config.h>
  21
  22 #include <time.h>
  23
  24 #include <stddef.h>
  25
  26 #include "dostime.h"
  27
  28 /*
  29  * The specification to which this was written.  From Joe Buck.
  30  * The DOS format appears to have only 2 second resolution.  It is an
  31  * unsigned long, and ORs together
  32  *
  33  * (year-1980)<<25
  34  * month<<21  (month is tm_mon + 1, 1=Jan through 12=Dec)
  35  * day<<16    (day is tm_mday, 1-31)
  36  * hour<<11   (hour is tm_hour, 0-23)
  37  * min<<5          (min is tm_min, 0-59)
  38  * sec>>1          (sec is tm_sec, 0-59, that's right, we throw away the LSB)
  39  *
  40  * DOS uses local time, so the localtime() call is used to turn the time_t
  41  * into a struct tm.
  42  */
  43
  44 time_t
  45 dos2unixtime (unsigned long dostime)
  46 {
  47   struct tm ltime;
  48   time_t now = time (NULL);
  49
  50   /* Call localtime to initialize timezone in TIME.  */
  51   ltime = *localtime (&now);
  52
  53   ltime.tm_year = (dostime >> 25) + 80;
  54   ltime.tm_mon = ((dostime >> 21) & 0x0f) - 1;
  55   ltime.tm_mday = (dostime >> 16) & 0x1f;
  56   ltime.tm_hour = (dostime >> 11) & 0x0f;
  57   ltime.tm_min = (dostime >> 5) & 0x3f;
  58   ltime.tm_sec = (dostime & 0x1f) << 1;
  59
  60   ltime.tm_wday = -1;
  61   ltime.tm_yday = -1;
  62   ltime.tm_isdst = -1;
  63
  64   return mktime (&ltime);
  65 }
  66
  67 unsigned long
  68 unix2dostime (time_t *time)
  69 {
  70   struct tm *ltime = localtime (time);
  71   int year = ltime->tm_year - 80;
  72   if (year < 0)
  73     year = 0;
  74
  75   return (year << 25
  76           | (ltime->tm_mon + 1) << 21
  77           | ltime->tm_mday << 16
  78           | ltime->tm_hour << 11
  79           | ltime->tm_min << 5
  80           | ltime->tm_sec >> 1);
  81 }