1 /*
   2  * ntfstime.h - NTFS time related functions.  Part of the Linux-NTFS project.
   3  *
   4  * Copyright (c) 2005      Anton Altaparmakov
   5  * Copyright (c) 2005-2007 Yura Pakhuchiy
   6  *
   7  * This program/include file is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as published
   9  * by the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program/include file is distributed in the hope that it will be
  13  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  14  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program (in the main directory of the Linux-NTFS
  19  * distribution in the file COPYING); if not, write to the Free Software
  20  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22 
  23 #ifndef _NTFS_NTFSTIME_H
  24 #define _NTFS_NTFSTIME_H
  25 
  26 #ifdef HAVE_TIME_H
  27 #include <time.h>
  28 #endif
  29 
  30 #include "types.h"
  31 
  32 #define NTFS_TIME_OFFSET ((s64)(369 * 365 + 89) * 24 * 3600 * 10000000)
  33 
  34 /**
  35  * ntfs2utc - Convert an NTFS time to Unix time
  36  * @ntfs_time:  An NTFS time in 100ns units since 1601
  37  *
  38  * NTFS stores times as the number of 100ns intervals since January 1st 1601 at
  39  * 00:00 UTC.  This system will not suffer from Y2K problems until ~57000AD.
  40  *
  41  * Return:  n  A Unix time (number of seconds since 1970)
  42  */
  43 static __inline__ time_t ntfs2utc(sle64 ntfs_time)
  44 {
  45         return (sle64_to_cpu(ntfs_time) - (NTFS_TIME_OFFSET)) / 10000000;
  46 }
  47 
  48 /**
  49  * utc2ntfs - Convert Linux time to NTFS time
  50  * @utc_time:  Linux time to convert to NTFS
  51  *
  52  * Convert the Linux time @utc_time to its corresponding NTFS time.
  53  *
  54  * Linux stores time in a long at present and measures it as the number of
  55  * 1-second intervals since 1st January 1970, 00:00:00 UTC.
  56  *
  57  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  58  * measured as the number of 100 nano-second intervals since 1st January 1601,
  59  * 00:00:00 UTC.
  60  *
  61  * Return:  n  An NTFS time (100ns units since Jan 1601)
  62  */
  63 static __inline__ sle64 utc2ntfs(time_t utc_time)
  64 {
  65         /* Convert to 100ns intervals and then add the NTFS time offset. */
  66         return cpu_to_sle64((s64)utc_time * 10000000 + NTFS_TIME_OFFSET);
  67 }
  68 
  69 #endif /* _NTFS_NTFSTIME_H */