fs/ntfs/time.h

   1 /*
   2  * time.h - NTFS time conversion functions.  Part of the Linux-NTFS project.
   3  *
   4  * Copyright (c) 2001-2005 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 #ifndef _LINUX_NTFS_TIME_H
  23 #define _LINUX_NTFS_TIME_H
  24
  25 #include <linux/time.h>         /* For current_kernel_time(). */
  26 #include <asm/div64.h>          /* For do_div(). */
  27
  28 #include "endian.h"
  29
  30 #define NTFS_TIME_OFFSET ((s64)(369 * 365 + 89) * 24 * 3600 * 10000000)
  31
  32 /**
  33  * utc2ntfs - convert Linux UTC time to NTFS time
  34  * @ts:         Linux UTC time to convert to NTFS time
  35  *
  36  * Convert the Linux UTC time @ts to its corresponding NTFS time and return
  37  * that in little endian format.
  38  *
  39  * Linux stores time in a struct timespec consisting of a time_t (long at
  40  * present) tv_sec and a long tv_nsec where tv_sec is the number of 1-second
  41  * intervals since 1st January 1970, 00:00:00 UTC and tv_nsec is the number of
  42  * 1-nano-second intervals since the value of tv_sec.
  43  *
  44  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  45  * measured as the number of 100-nano-second intervals since 1st January 1601,
  46  * 00:00:00 UTC.
  47  */
  48 static inline sle64 utc2ntfs(const struct timespec ts)
  49 {
  50         /*
  51          * Convert the seconds to 100ns intervals, add the nano-seconds
  52          * converted to 100ns intervals, and then add the NTFS time offset.
  53          */
  54         return cpu_to_sle64((s64)ts.tv_sec * 10000000 + ts.tv_nsec / 100 +
  55                         NTFS_TIME_OFFSET);
  56 }
  57
  58 /**
  59  * get_current_ntfs_time - get the current time in little endian NTFS format
  60  *
  61  * Get the current time from the Linux kernel, convert it to its corresponding
  62  * NTFS time and return that in little endian format.
  63  */
  64 static inline sle64 get_current_ntfs_time(void)
  65 {
  66         return utc2ntfs(current_kernel_time());
  67 }
  68
  69 /**
  70  * ntfs2utc - convert NTFS time to Linux time
  71  * @time:       NTFS time (little endian) to convert to Linux UTC
  72  *
  73  * Convert the little endian NTFS time @time to its corresponding Linux UTC
  74  * time and return that in cpu format.
  75  *
  76  * Linux stores time in a struct timespec consisting of a time_t (long at
  77  * present) tv_sec and a long tv_nsec where tv_sec is the number of 1-second
  78  * intervals since 1st January 1970, 00:00:00 UTC and tv_nsec is the number of
  79  * 1-nano-second intervals since the value of tv_sec.
  80  *
  81  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  82  * measured as the number of 100 nano-second intervals since 1st January 1601,
  83  * 00:00:00 UTC.
  84  */
  85 static inline struct timespec ntfs2utc(const sle64 time)
  86 {
  87         struct timespec ts;
  88
  89         /* Subtract the NTFS time offset. */
  90         u64 t = (u64)(sle64_to_cpu(time) - NTFS_TIME_OFFSET);
  91         /*
  92          * Convert the time to 1-second intervals and the remainder to
  93          * 1-nano-second intervals.
  94          */
  95         ts.tv_nsec = do_div(t, 10000000) * 100;
  96         ts.tv_sec = t;
  97         return ts;
  98 }
  99
 100 #endif /* _LINUX_NTFS_TIME_H */