/*
   * 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 */