fs/ntfs/time.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * time.h - NTFS time conversion functions.  Part of the Linux-NTFS project.
   4  *
   5  * Copyright (c) 2001-2005 Anton Altaparmakov
   6  */
   7
   8 #ifndef _LINUX_NTFS_TIME_H
   9 #define _LINUX_NTFS_TIME_H
  10
  11 #include <linux/time.h>         /* For current_kernel_time(). */
  12 #include <asm/div64.h>          /* For do_div(). */
  13
  14 #include "endian.h"
  15
  16 #define NTFS_TIME_OFFSET ((s64)(369 * 365 + 89) * 24 * 3600 * 10000000)
  17
  18 /**
  19  * utc2ntfs - convert Linux UTC time to NTFS time
  20  * @ts:         Linux UTC time to convert to NTFS time
  21  *
  22  * Convert the Linux UTC time @ts to its corresponding NTFS time and return
  23  * that in little endian format.
  24  *
  25  * Linux stores time in a struct timespec64 consisting of a time64_t tv_sec
  26  * and a long tv_nsec where tv_sec is the number of 1-second intervals since
  27  * 1st January 1970, 00:00:00 UTC and tv_nsec is the number of 1-nano-second
  28  * intervals since the value of tv_sec.
  29  *
  30  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  31  * measured as the number of 100-nano-second intervals since 1st January 1601,
  32  * 00:00:00 UTC.
  33  */
  34 static inline sle64 utc2ntfs(const struct timespec64 ts)
  35 {
  36         /*
  37          * Convert the seconds to 100ns intervals, add the nano-seconds
  38          * converted to 100ns intervals, and then add the NTFS time offset.
  39          */
  40         return cpu_to_sle64((s64)ts.tv_sec * 10000000 + ts.tv_nsec / 100 +
  41                         NTFS_TIME_OFFSET);
  42 }
  43
  44 /**
  45  * get_current_ntfs_time - get the current time in little endian NTFS format
  46  *
  47  * Get the current time from the Linux kernel, convert it to its corresponding
  48  * NTFS time and return that in little endian format.
  49  */
  50 static inline sle64 get_current_ntfs_time(void)
  51 {
  52         struct timespec64 ts;
  53
  54         ktime_get_coarse_real_ts64(&ts);
  55         return utc2ntfs(ts);
  56 }
  57
  58 /**
  59  * ntfs2utc - convert NTFS time to Linux time
  60  * @time:       NTFS time (little endian) to convert to Linux UTC
  61  *
  62  * Convert the little endian NTFS time @time to its corresponding Linux UTC
  63  * time and return that in cpu format.
  64  *
  65  * Linux stores time in a struct timespec64 consisting of a time64_t tv_sec
  66  * and a long tv_nsec where tv_sec is the number of 1-second intervals since
  67  * 1st January 1970, 00:00:00 UTC and tv_nsec is the number of 1-nano-second
  68  * intervals since the value of tv_sec.
  69  *
  70  * NTFS uses Microsoft's standard time format which is stored in a s64 and is
  71  * measured as the number of 100 nano-second intervals since 1st January 1601,
  72  * 00:00:00 UTC.
  73  */
  74 static inline struct timespec64 ntfs2utc(const sle64 time)
  75 {
  76         struct timespec64 ts;
  77
  78         /* Subtract the NTFS time offset. */
  79         u64 t = (u64)(sle64_to_cpu(time) - NTFS_TIME_OFFSET);
  80         /*
  81          * Convert the time to 1-second intervals and the remainder to
  82          * 1-nano-second intervals.
  83          */
  84         ts.tv_nsec = do_div(t, 10000000) * 100;
  85         ts.tv_sec = t;
  86         return ts;
  87 }
  88
  89 #endif /* _LINUX_NTFS_TIME_H */