reactos/drivers/fs/ntfs/linux-ntfs/time.c

   1 /*
   2  * time.c - NTFS time conversion functions. Part of the Linux-NTFS project.
   3  *
   4  * Copyright (c) 2001 Anton Altaparmakov.
   5  *
   6  * This program/include file is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as published
   8  * by the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program/include file is distributed in the hope that it will be
  12  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  13  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program (in the main directory of the Linux-NTFS
  18  * distribution in the file COPYING); if not, write to the Free Software
  19  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/sched.h>        /* For CURRENT_TIME. */
  23 #include <asm/div64.h>          /* For do_div(). */
  24
  25 #include "ntfs.h"
  26
  27 #define NTFS_TIME_OFFSET ((s64)(369 * 365 + 89) * 24 * 3600 * 10000000)
  28
  29 /**
  30  * utc2ntfs - convert Linux time to NTFS time
  31  * @time:               Linux time to convert to NTFS
  32  *
  33  * Convert the Linux time @time to its corresponding NTFS time and return that
  34  * in little endian format.
  35  *
  36  * Linux stores time in a long at present and measures it as the number of
  37  * 1-second intervals since 1st January 1970, 00:00:00 UTC.
  38  *
  39  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  40  * measured as the number of 100 nano-second intervals since 1st January 1601,
  41  * 00:00:00 UTC.
  42  */
  43 inline s64 utc2ntfs(const time_t time)
  44 {
  45         /* Convert to 100ns intervals and then add the NTFS time offset. */
  46         return cpu_to_sle64((s64)time * 10000000 + NTFS_TIME_OFFSET);
  47 }
  48
  49 /**
  50  * get_current_ntfs_time - get the current time in little endian NTFS format
  51  *
  52  * Get the current time from the Linux kernel, convert it to its corresponding
  53  * NTFS time and return that in little endian format.
  54  */
  55 inline s64 get_current_ntfs_time(void)
  56 {
  57         /* ignores leap second */
  58         return utc2ntfs(get_seconds()) + xtime.tv_nsec/1000;
  59 }
  60
  61 /**
  62  * ntfs2utc - convert NTFS time to Linux time
  63  * @time:               NTFS time (little endian) to convert to Linux
  64  *
  65  * Convert the little endian NTFS time @time to its corresponding Linux time
  66  * and return that in cpu format.
  67  *
  68  * Linux stores time in a long at present and measures it as the number of
  69  * 1-second intervals since 1st January 1970, 00:00:00 UTC.
  70  *
  71  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  72  * measured as the number of 100 nano-second intervals since 1st January 1601,
  73  * 00:00:00 UTC.
  74  */
  75 inline time_t ntfs2utc(const s64 time)
  76 {
  77         /* Subtract the NTFS time offset, then convert to 1s intervals. */
  78         s64 t = sle64_to_cpu(time) - NTFS_TIME_OFFSET;
  79         do_div(t, 10000000);
  80         return (time_t)t;
  81 }
  82