std/sys/pal/unix/
time.rs

1use core::num::niche_types::Nanoseconds;
2
3use crate::time::Duration;
4use crate::{fmt, io};
5
6const NSEC_PER_SEC: u64 = 1_000_000_000;
7pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
8#[allow(dead_code)] // Used for pthread condvar timeouts
9pub const TIMESPEC_MAX: libc::timespec =
10    libc::timespec { tv_sec: <libc::time_t>::MAX, tv_nsec: 1_000_000_000 - 1 };
11
12// This additional constant is only used when calling
13// `libc::pthread_cond_timedwait`.
14#[cfg(target_os = "nto")]
15pub(in crate::sys) const TIMESPEC_MAX_CAPPED: libc::timespec = libc::timespec {
16    tv_sec: (u64::MAX / NSEC_PER_SEC) as i64,
17    tv_nsec: (u64::MAX % NSEC_PER_SEC) as i64,
18};
19
20#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
21pub struct SystemTime {
22    pub(crate) t: Timespec,
23}
24
25#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
26pub(crate) struct Timespec {
27    tv_sec: i64,
28    tv_nsec: Nanoseconds,
29}
30
31impl SystemTime {
32    #[cfg_attr(any(target_os = "horizon", target_os = "hurd"), allow(unused))]
33    pub fn new(tv_sec: i64, tv_nsec: i64) -> Result<SystemTime, io::Error> {
34        Ok(SystemTime { t: Timespec::new(tv_sec, tv_nsec)? })
35    }
36
37    pub fn now() -> SystemTime {
38        SystemTime { t: Timespec::now(libc::CLOCK_REALTIME) }
39    }
40
41    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
42        self.t.sub_timespec(&other.t)
43    }
44
45    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
46        Some(SystemTime { t: self.t.checked_add_duration(other)? })
47    }
48
49    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
50        Some(SystemTime { t: self.t.checked_sub_duration(other)? })
51    }
52}
53
54impl fmt::Debug for SystemTime {
55    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
56        f.debug_struct("SystemTime")
57            .field("tv_sec", &self.t.tv_sec)
58            .field("tv_nsec", &self.t.tv_nsec)
59            .finish()
60    }
61}
62
63impl Timespec {
64    const unsafe fn new_unchecked(tv_sec: i64, tv_nsec: i64) -> Timespec {
65        Timespec { tv_sec, tv_nsec: unsafe { Nanoseconds::new_unchecked(tv_nsec as u32) } }
66    }
67
68    pub const fn zero() -> Timespec {
69        unsafe { Self::new_unchecked(0, 0) }
70    }
71
72    const fn new(tv_sec: i64, tv_nsec: i64) -> Result<Timespec, io::Error> {
73        // On Apple OS, dates before epoch are represented differently than on other
74        // Unix platforms: e.g. 1/10th of a second before epoch is represented as `seconds=-1`
75        // and `nanoseconds=100_000_000` on other platforms, but is `seconds=0` and
76        // `nanoseconds=-900_000_000` on Apple OS.
77        //
78        // To compensate, we first detect this special case by checking if both
79        // seconds and nanoseconds are in range, and then correct the value for seconds
80        // and nanoseconds to match the common unix representation.
81        //
82        // Please note that Apple OS nonetheless accepts the standard unix format when
83        // setting file times, which makes this compensation round-trippable and generally
84        // transparent.
85        #[cfg(target_vendor = "apple")]
86        let (tv_sec, tv_nsec) =
87            if (tv_sec <= 0 && tv_sec > i64::MIN) && (tv_nsec < 0 && tv_nsec > -1_000_000_000) {
88                (tv_sec - 1, tv_nsec + 1_000_000_000)
89            } else {
90                (tv_sec, tv_nsec)
91            };
92        if tv_nsec >= 0 && tv_nsec < NSEC_PER_SEC as i64 {
93            Ok(unsafe { Self::new_unchecked(tv_sec, tv_nsec) })
94        } else {
95            Err(io::const_error!(io::ErrorKind::InvalidData, "invalid timestamp"))
96        }
97    }
98
99    pub fn now(clock: libc::clockid_t) -> Timespec {
100        use crate::mem::MaybeUninit;
101        use crate::sys::cvt;
102
103        // Try to use 64-bit time in preparation for Y2038.
104        #[cfg(all(
105            target_os = "linux",
106            target_env = "gnu",
107            target_pointer_width = "32",
108            not(target_arch = "riscv32")
109        ))]
110        {
111            use crate::sys::weak::weak;
112
113            // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
114            // and it handles both vDSO calls and ENOSYS fallbacks itself.
115            weak!(
116                fn __clock_gettime64(
117                    clockid: libc::clockid_t,
118                    tp: *mut __timespec64,
119                ) -> libc::c_int;
120            );
121
122            if let Some(clock_gettime64) = __clock_gettime64.get() {
123                let mut t = MaybeUninit::uninit();
124                cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
125                let t = unsafe { t.assume_init() };
126                return Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap();
127            }
128        }
129
130        let mut t = MaybeUninit::uninit();
131        cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
132        let t = unsafe { t.assume_init() };
133        Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap()
134    }
135
136    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
137        if self >= other {
138            // NOTE(eddyb) two aspects of this `if`-`else` are required for LLVM
139            // to optimize it into a branchless form (see also #75545):
140            //
141            // 1. `self.tv_sec - other.tv_sec` shows up as a common expression
142            //    in both branches, i.e. the `else` must have its `- 1`
143            //    subtraction after the common one, not interleaved with it
144            //    (it used to be `self.tv_sec - 1 - other.tv_sec`)
145            //
146            // 2. the `Duration::new` call (or any other additional complexity)
147            //    is outside of the `if`-`else`, not duplicated in both branches
148            //
149            // Ideally this code could be rearranged such that it more
150            // directly expresses the lower-cost behavior we want from it.
151            let (secs, nsec) = if self.tv_nsec.as_inner() >= other.tv_nsec.as_inner() {
152                (
153                    (self.tv_sec - other.tv_sec) as u64,
154                    self.tv_nsec.as_inner() - other.tv_nsec.as_inner(),
155                )
156            } else {
157                (
158                    (self.tv_sec - other.tv_sec - 1) as u64,
159                    self.tv_nsec.as_inner() + (NSEC_PER_SEC as u32) - other.tv_nsec.as_inner(),
160                )
161            };
162
163            Ok(Duration::new(secs, nsec))
164        } else {
165            match other.sub_timespec(self) {
166                Ok(d) => Err(d),
167                Err(d) => Ok(d),
168            }
169        }
170    }
171
172    pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
173        let mut secs = self.tv_sec.checked_add_unsigned(other.as_secs())?;
174
175        // Nano calculations can't overflow because nanos are <1B which fit
176        // in a u32.
177        let mut nsec = other.subsec_nanos() + self.tv_nsec.as_inner();
178        if nsec >= NSEC_PER_SEC as u32 {
179            nsec -= NSEC_PER_SEC as u32;
180            secs = secs.checked_add(1)?;
181        }
182        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
183    }
184
185    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
186        let mut secs = self.tv_sec.checked_sub_unsigned(other.as_secs())?;
187
188        // Similar to above, nanos can't overflow.
189        let mut nsec = self.tv_nsec.as_inner() as i32 - other.subsec_nanos() as i32;
190        if nsec < 0 {
191            nsec += NSEC_PER_SEC as i32;
192            secs = secs.checked_sub(1)?;
193        }
194        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
195    }
196
197    #[allow(dead_code)]
198    pub fn to_timespec(&self) -> Option<libc::timespec> {
199        Some(libc::timespec {
200            tv_sec: self.tv_sec.try_into().ok()?,
201            tv_nsec: self.tv_nsec.as_inner().try_into().ok()?,
202        })
203    }
204
205    // On QNX Neutrino, the maximum timespec for e.g. pthread_cond_timedwait
206    // is 2^64 nanoseconds
207    #[cfg(target_os = "nto")]
208    pub(in crate::sys) fn to_timespec_capped(&self) -> Option<libc::timespec> {
209        // Check if timeout in nanoseconds would fit into an u64
210        if (self.tv_nsec.as_inner() as u64)
211            .checked_add((self.tv_sec as u64).checked_mul(NSEC_PER_SEC)?)
212            .is_none()
213        {
214            return None;
215        }
216        self.to_timespec()
217    }
218
219    #[cfg(all(
220        target_os = "linux",
221        target_env = "gnu",
222        target_pointer_width = "32",
223        not(target_arch = "riscv32")
224    ))]
225    pub fn to_timespec64(&self) -> __timespec64 {
226        __timespec64::new(self.tv_sec, self.tv_nsec.as_inner() as _)
227    }
228}
229
230#[cfg(all(
231    target_os = "linux",
232    target_env = "gnu",
233    target_pointer_width = "32",
234    not(target_arch = "riscv32")
235))]
236#[repr(C)]
237pub(crate) struct __timespec64 {
238    pub(crate) tv_sec: i64,
239    #[cfg(target_endian = "big")]
240    _padding: i32,
241    pub(crate) tv_nsec: i32,
242    #[cfg(target_endian = "little")]
243    _padding: i32,
244}
245
246#[cfg(all(
247    target_os = "linux",
248    target_env = "gnu",
249    target_pointer_width = "32",
250    not(target_arch = "riscv32")
251))]
252impl __timespec64 {
253    pub(crate) fn new(tv_sec: i64, tv_nsec: i32) -> Self {
254        Self { tv_sec, tv_nsec, _padding: 0 }
255    }
256}
257
258#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
259pub struct Instant {
260    t: Timespec,
261}
262
263impl Instant {
264    pub fn now() -> Instant {
265        // https://www.manpagez.com/man/3/clock_gettime/
266        //
267        // CLOCK_UPTIME_RAW   clock that increments monotonically, in the same man-
268        //                    ner as CLOCK_MONOTONIC_RAW, but that does not incre-
269        //                    ment while the system is asleep.  The returned value
270        //                    is identical to the result of mach_absolute_time()
271        //                    after the appropriate mach_timebase conversion is
272        //                    applied.
273        //
274        // Instant on macos was historically implemented using mach_absolute_time;
275        // we preserve this value domain out of an abundance of caution.
276        #[cfg(target_vendor = "apple")]
277        const clock_id: libc::clockid_t = libc::CLOCK_UPTIME_RAW;
278        #[cfg(not(target_vendor = "apple"))]
279        const clock_id: libc::clockid_t = libc::CLOCK_MONOTONIC;
280        Instant { t: Timespec::now(clock_id) }
281    }
282
283    pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
284        self.t.sub_timespec(&other.t).ok()
285    }
286
287    pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
288        Some(Instant { t: self.t.checked_add_duration(other)? })
289    }
290
291    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
292        Some(Instant { t: self.t.checked_sub_duration(other)? })
293    }
294}
295
296impl fmt::Debug for Instant {
297    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
298        f.debug_struct("Instant")
299            .field("tv_sec", &self.t.tv_sec)
300            .field("tv_nsec", &self.t.tv_nsec)
301            .finish()
302    }
303}
std/sys/pal/unix/time.rs

std/sys/pal/unix/
time.rs
