FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/time.h

     /*
      * time.h - NTFS time conversion functions.  Part of the Linux-NTFS project.
      *
      * Copyright (c) 2001-2005 Anton Altaparmakov
      *
      * This program/include file is free software; you can redistribute it and/or
      * modify it under the terms of the GNU General Public License as published
      * by the Free Software Foundation; either version 2 of the License, or
      * (at your option) any later version.
     *
     * This program/include file is distributed in the hope that it will be
     * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
     * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program (in the main directory of the Linux-NTFS
     * distribution in the file COPYING); if not, write to the Free Software
     * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     */
    
    #ifndef _LINUX_NTFS_TIME_H
    #define _LINUX_NTFS_TIME_H
    
    #include <linux/time.h>         /* For current_kernel_time(). */
    #include <asm/div64.h>          /* For do_div(). */
    
    #include "endian.h"
    
    #define NTFS_TIME_OFFSET ((s64)(369 * 365 + 89) * 24 * 3600 * 10000000)
    
    /**
     * utc2ntfs - convert Linux UTC time to NTFS time
     * @ts:         Linux UTC time to convert to NTFS time
     *
     * Convert the Linux UTC time @ts to its corresponding NTFS time and return
     * that in little endian format.
     *
     * Linux stores time in a struct timespec consisting of a time_t (long at
     * present) tv_sec and a long tv_nsec where tv_sec is the number of 1-second
     * intervals since 1st January 1970, 00:00:00 UTC and tv_nsec is the number of
     * 1-nano-second intervals since the value of tv_sec.
     *
     * NTFS uses Microsoft's standard time format which is stored in a s64 and is
     * measured as the number of 100-nano-second intervals since 1st January 1601,
     * 00:00:00 UTC.
     */
    static inline sle64 utc2ntfs(const struct timespec ts)
    {
            /*
             * Convert the seconds to 100ns intervals, add the nano-seconds
             * converted to 100ns intervals, and then add the NTFS time offset.
             */
            return cpu_to_sle64((s64)ts.tv_sec * 10000000 + ts.tv_nsec / 100 +
                            NTFS_TIME_OFFSET);
    }
    
    /**
     * get_current_ntfs_time - get the current time in little endian NTFS format
     *
     * Get the current time from the Linux kernel, convert it to its corresponding
     * NTFS time and return that in little endian format.
     */
    static inline sle64 get_current_ntfs_time(void)
    {
            return utc2ntfs(current_kernel_time());
    }
    
    /**
     * ntfs2utc - convert NTFS time to Linux time
     * @time:       NTFS time (little endian) to convert to Linux UTC
     *
     * Convert the little endian NTFS time @time to its corresponding Linux UTC
     * time and return that in cpu format.
     *
     * Linux stores time in a struct timespec consisting of a time_t (long at
     * present) tv_sec and a long tv_nsec where tv_sec is the number of 1-second
     * intervals since 1st January 1970, 00:00:00 UTC and tv_nsec is the number of
     * 1-nano-second intervals since the value of tv_sec.
     *
     * NTFS uses Microsoft's standard time format which is stored in a s64 and is
     * measured as the number of 100 nano-second intervals since 1st January 1601,
     * 00:00:00 UTC.
     */
    static inline struct timespec ntfs2utc(const sle64 time)
    {
            struct timespec ts;
    
            /* Subtract the NTFS time offset. */
            u64 t = (u64)(sle64_to_cpu(time) - NTFS_TIME_OFFSET);
            /*
             * Convert the time to 1-second intervals and the remainder to
             * 1-nano-second intervals.
             */
            ts.tv_nsec = do_div(t, 10000000) * 100;
            ts.tv_sec = t;
            return ts;
    }
    
   #endif /* _LINUX_NTFS_TIME_H */

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