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 */ 90