std/sys/pal/unix/
time.rs

1use core::num::niche_types::Nanoseconds;
2
3use crate::io;
4use crate::time::Duration;
5
6const NSEC_PER_SEC: u64 = 1_000_000_000;
7
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(crate) struct Timespec {
22    pub tv_sec: i64,
23    pub tv_nsec: Nanoseconds,
24}
25
26impl Timespec {
27    pub const MAX: Timespec = unsafe { Self::new_unchecked(i64::MAX, 1_000_000_000 - 1) };
28
29    // As described below, on Apple OS, dates before epoch are represented differently.
30    // This is not an issue here however, because we are using tv_sec = i64::MIN,
31    // which will cause the compatibility wrapper to not be executed at all.
32    pub const MIN: Timespec = unsafe { Self::new_unchecked(i64::MIN, 0) };
33
34    const unsafe fn new_unchecked(tv_sec: i64, tv_nsec: i64) -> Timespec {
35        Timespec { tv_sec, tv_nsec: unsafe { Nanoseconds::new_unchecked(tv_nsec as u32) } }
36    }
37
38    pub const fn zero() -> Timespec {
39        unsafe { Self::new_unchecked(0, 0) }
40    }
41
42    pub const fn new(tv_sec: i64, tv_nsec: i64) -> Result<Timespec, io::Error> {
43        // On Apple OS, dates before epoch are represented differently than on other
44        // Unix platforms: e.g. 1/10th of a second before epoch is represented as `seconds=-1`
45        // and `nanoseconds=100_000_000` on other platforms, but is `seconds=0` and
46        // `nanoseconds=-900_000_000` on Apple OS.
47        //
48        // To compensate, we first detect this special case by checking if both
49        // seconds and nanoseconds are in range, and then correct the value for seconds
50        // and nanoseconds to match the common unix representation.
51        //
52        // Please note that Apple OS nonetheless accepts the standard unix format when
53        // setting file times, which makes this compensation round-trippable and generally
54        // transparent.
55        #[cfg(target_vendor = "apple")]
56        let (tv_sec, tv_nsec) =
57            if (tv_sec <= 0 && tv_sec > i64::MIN) && (tv_nsec < 0 && tv_nsec > -1_000_000_000) {
58                (tv_sec - 1, tv_nsec + 1_000_000_000)
59            } else {
60                (tv_sec, tv_nsec)
61            };
62        if tv_nsec >= 0 && tv_nsec < NSEC_PER_SEC as i64 {
63            Ok(unsafe { Self::new_unchecked(tv_sec, tv_nsec) })
64        } else {
65            Err(io::const_error!(io::ErrorKind::InvalidData, "invalid timestamp"))
66        }
67    }
68
69    pub fn now(clock: libc::clockid_t) -> Timespec {
70        use crate::mem::MaybeUninit;
71        use crate::sys::cvt;
72
73        // Try to use 64-bit time in preparation for Y2038.
74        #[cfg(all(
75            target_os = "linux",
76            target_env = "gnu",
77            target_pointer_width = "32",
78            not(target_arch = "riscv32")
79        ))]
80        {
81            use crate::sys::weak::weak;
82
83            // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
84            // and it handles both vDSO calls and ENOSYS fallbacks itself.
85            weak!(
86                fn __clock_gettime64(
87                    clockid: libc::clockid_t,
88                    tp: *mut __timespec64,
89                ) -> libc::c_int;
90            );
91
92            if let Some(clock_gettime64) = __clock_gettime64.get() {
93                let mut t = MaybeUninit::uninit();
94                cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
95                let t = unsafe { t.assume_init() };
96                return Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap();
97            }
98        }
99
100        let mut t = MaybeUninit::uninit();
101        cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
102        let t = unsafe { t.assume_init() };
103        Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap()
104    }
105
106    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
107        // When a >= b, the difference fits in u64.
108        fn sub_ge_to_unsigned(a: i64, b: i64) -> u64 {
109            debug_assert!(a >= b);
110            a.wrapping_sub(b).cast_unsigned()
111        }
112
113        if self >= other {
114            let (secs, nsec) = if self.tv_nsec.as_inner() >= other.tv_nsec.as_inner() {
115                (
116                    sub_ge_to_unsigned(self.tv_sec, other.tv_sec),
117                    self.tv_nsec.as_inner() - other.tv_nsec.as_inner(),
118                )
119            } else {
120                // Following sequence of assertions explain why `self.tv_sec - 1` does not underflow.
121                debug_assert!(self.tv_nsec < other.tv_nsec);
122                debug_assert!(self.tv_sec > other.tv_sec);
123                debug_assert!(self.tv_sec > i64::MIN);
124                (
125                    sub_ge_to_unsigned(self.tv_sec - 1, other.tv_sec),
126                    self.tv_nsec.as_inner() + (NSEC_PER_SEC as u32) - other.tv_nsec.as_inner(),
127                )
128            };
129
130            Ok(Duration::new(secs, nsec))
131        } else {
132            match other.sub_timespec(self) {
133                Ok(d) => Err(d),
134                Err(d) => Ok(d),
135            }
136        }
137    }
138
139    pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
140        let mut secs = self.tv_sec.checked_add_unsigned(other.as_secs())?;
141
142        // Nano calculations can't overflow because nanos are <1B which fit
143        // in a u32.
144        let mut nsec = other.subsec_nanos() + self.tv_nsec.as_inner();
145        if nsec >= NSEC_PER_SEC as u32 {
146            nsec -= NSEC_PER_SEC as u32;
147            secs = secs.checked_add(1)?;
148        }
149        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
150    }
151
152    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
153        let mut secs = self.tv_sec.checked_sub_unsigned(other.as_secs())?;
154
155        // Similar to above, nanos can't overflow.
156        let mut nsec = self.tv_nsec.as_inner() as i32 - other.subsec_nanos() as i32;
157        if nsec < 0 {
158            nsec += NSEC_PER_SEC as i32;
159            secs = secs.checked_sub(1)?;
160        }
161        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
162    }
163
164    #[allow(dead_code)]
165    pub fn to_timespec(&self) -> Option<libc::timespec> {
166        Some(libc::timespec {
167            tv_sec: self.tv_sec.try_into().ok()?,
168            tv_nsec: self.tv_nsec.as_inner().try_into().ok()?,
169        })
170    }
171
172    // On QNX Neutrino, the maximum timespec for e.g. pthread_cond_timedwait
173    // is 2^64 nanoseconds
174    #[cfg(target_os = "nto")]
175    pub(in crate::sys) fn to_timespec_capped(&self) -> Option<libc::timespec> {
176        // Check if timeout in nanoseconds would fit into an u64
177        if (self.tv_nsec.as_inner() as u64)
178            .checked_add((self.tv_sec as u64).checked_mul(NSEC_PER_SEC)?)
179            .is_none()
180        {
181            return None;
182        }
183        self.to_timespec()
184    }
185
186    #[cfg(all(
187        target_os = "linux",
188        target_env = "gnu",
189        target_pointer_width = "32",
190        not(target_arch = "riscv32")
191    ))]
192    pub fn to_timespec64(&self) -> __timespec64 {
193        __timespec64::new(self.tv_sec, self.tv_nsec.as_inner() as _)
194    }
195}
196
197#[cfg(all(
198    target_os = "linux",
199    target_env = "gnu",
200    target_pointer_width = "32",
201    not(target_arch = "riscv32")
202))]
203#[repr(C)]
204pub(crate) struct __timespec64 {
205    pub(crate) tv_sec: i64,
206    #[cfg(target_endian = "big")]
207    _padding: i32,
208    pub(crate) tv_nsec: i32,
209    #[cfg(target_endian = "little")]
210    _padding: i32,
211}
212
213#[cfg(all(
214    target_os = "linux",
215    target_env = "gnu",
216    target_pointer_width = "32",
217    not(target_arch = "riscv32")
218))]
219impl __timespec64 {
220    pub(crate) fn new(tv_sec: i64, tv_nsec: i32) -> Self {
221        Self { tv_sec, tv_nsec, _padding: 0 }
222    }
223}
std/sys/pal/unix/time.rs

std/sys/pal/unix/
time.rs
