/* SPDX-License-Identifier: GPL-2.0-or-later */

  /*
   * time.h - NTFS time conversion functions.  Part of the Linux-NTFS project.
   *

   * Copyright (c) 2001-2005 Anton Altaparmakov

   */
  
  #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 timespec64 consisting of a time64_t 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 timespec64 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)
  {

  	struct timespec64 ts;
  
  	ktime_get_coarse_real_ts64(&ts);
  	return utc2ntfs(ts);

  }
  
  /**
   * 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 timespec64 consisting of a time64_t 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 timespec64 ntfs2utc(const sle64 time)

  {

  	struct timespec64 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 */