std/sys/pal/unix/
time.rs

1use core::mem;
2use core::num::niche_types::Nanoseconds;
3
4use crate::io;
5use crate::time::Duration;
6
7const NSEC_PER_SEC: u64 = 1_000_000_000;
8
9#[allow(dead_code)] // Used for pthread condvar timeouts
10pub const TIMESPEC_MAX: libc::timespec = {
11    let mut ts = unsafe { mem::zeroed::<libc::timespec>() };
12    ts.tv_sec = <libc::time_t>::MAX;
13    ts.tv_nsec = 1_000_000_000 - 1;
14    ts
15};
16
17// This additional constant is only used when calling
18// `libc::pthread_cond_timedwait`.
19#[cfg(target_os = "nto")]
20pub(in crate::sys) const TIMESPEC_MAX_CAPPED: libc::timespec = libc::timespec {
21    tv_sec: (u64::MAX / NSEC_PER_SEC) as i64,
22    tv_nsec: (u64::MAX % NSEC_PER_SEC) as i64,
23};
24
25#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
26pub(crate) struct Timespec {
27    pub tv_sec: i64,
28    pub tv_nsec: Nanoseconds,
29}
30
31impl Timespec {
32    pub const MAX: Timespec = unsafe { Self::new_unchecked(i64::MAX, 1_000_000_000 - 1) };
33
34    // As described below, on Apple OS, dates before epoch are represented differently.
35    // This is not an issue here however, because we are using tv_sec = i64::MIN,
36    // which will cause the compatibility wrapper to not be executed at all.
37    pub const MIN: Timespec = unsafe { Self::new_unchecked(i64::MIN, 0) };
38
39    const unsafe fn new_unchecked(tv_sec: i64, tv_nsec: i64) -> Timespec {
40        Timespec { tv_sec, tv_nsec: unsafe { Nanoseconds::new_unchecked(tv_nsec as u32) } }
41    }
42
43    pub const fn zero() -> Timespec {
44        unsafe { Self::new_unchecked(0, 0) }
45    }
46
47    pub const fn new(tv_sec: i64, tv_nsec: i64) -> Result<Timespec, io::Error> {
48        // On Apple OS, dates before epoch are represented differently than on other
49        // Unix platforms: e.g. 1/10th of a second before epoch is represented as `seconds=-1`
50        // and `nanoseconds=100_000_000` on other platforms, but is `seconds=0` and
51        // `nanoseconds=-900_000_000` on Apple OS.
52        //
53        // To compensate, we first detect this special case by checking if both
54        // seconds and nanoseconds are in range, and then correct the value for seconds
55        // and nanoseconds to match the common unix representation.
56        //
57        // Please note that Apple OS nonetheless accepts the standard unix format when
58        // setting file times, which makes this compensation round-trippable and generally
59        // transparent.
60        #[cfg(target_vendor = "apple")]
61        let (tv_sec, tv_nsec) =
62            if (tv_sec <= 0 && tv_sec > i64::MIN) && (tv_nsec < 0 && tv_nsec > -1_000_000_000) {
63                (tv_sec - 1, tv_nsec + 1_000_000_000)
64            } else {
65                (tv_sec, tv_nsec)
66            };
67        if tv_nsec >= 0 && tv_nsec < NSEC_PER_SEC as i64 {
68            Ok(unsafe { Self::new_unchecked(tv_sec, tv_nsec) })
69        } else {
70            Err(io::const_error!(io::ErrorKind::InvalidData, "invalid timestamp"))
71        }
72    }
73
74    #[allow(dead_code)]
75    pub fn now(clock: libc::clockid_t) -> Timespec {
76        use crate::mem::MaybeUninit;
77        use crate::sys::cvt;
78
79        // Try to use 64-bit time in preparation for Y2038.
80        #[cfg(all(
81            target_os = "linux",
82            target_env = "gnu",
83            target_pointer_width = "32",
84            not(target_arch = "riscv32")
85        ))]
86        {
87            use crate::sys::weak::weak;
88
89            // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
90            // and it handles both vDSO calls and ENOSYS fallbacks itself.
91            weak!(
92                fn __clock_gettime64(
93                    clockid: libc::clockid_t,
94                    tp: *mut __timespec64,
95                ) -> libc::c_int;
96            );
97
98            if let Some(clock_gettime64) = __clock_gettime64.get() {
99                let mut t = MaybeUninit::uninit();
100                cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
101                let t = unsafe { t.assume_init() };
102                return Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap();
103            }
104        }
105
106        let mut t = MaybeUninit::uninit();
107        cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
108        let t = unsafe { t.assume_init() };
109        Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap()
110    }
111
112    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
113        // When a >= b, the difference fits in u64.
114        fn sub_ge_to_unsigned(a: i64, b: i64) -> u64 {
115            debug_assert!(a >= b);
116            a.wrapping_sub(b).cast_unsigned()
117        }
118
119        if self >= other {
120            let (secs, nsec) = if self.tv_nsec.as_inner() >= other.tv_nsec.as_inner() {
121                (
122                    sub_ge_to_unsigned(self.tv_sec, other.tv_sec),
123                    self.tv_nsec.as_inner() - other.tv_nsec.as_inner(),
124                )
125            } else {
126                // Following sequence of assertions explain why `self.tv_sec - 1` does not underflow.
127                debug_assert!(self.tv_nsec < other.tv_nsec);
128                debug_assert!(self.tv_sec > other.tv_sec);
129                debug_assert!(self.tv_sec > i64::MIN);
130                (
131                    sub_ge_to_unsigned(self.tv_sec - 1, other.tv_sec),
132                    self.tv_nsec.as_inner() + (NSEC_PER_SEC as u32) - other.tv_nsec.as_inner(),
133                )
134            };
135
136            Ok(Duration::new(secs, nsec))
137        } else {
138            match other.sub_timespec(self) {
139                Ok(d) => Err(d),
140                Err(d) => Ok(d),
141            }
142        }
143    }
144
145    pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
146        let mut secs = self.tv_sec.checked_add_unsigned(other.as_secs())?;
147
148        // Nano calculations can't overflow because nanos are <1B which fit
149        // in a u32.
150        let mut nsec = other.subsec_nanos() + self.tv_nsec.as_inner();
151        if nsec >= NSEC_PER_SEC as u32 {
152            nsec -= NSEC_PER_SEC as u32;
153            secs = secs.checked_add(1)?;
154        }
155        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
156    }
157
158    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
159        let mut secs = self.tv_sec.checked_sub_unsigned(other.as_secs())?;
160
161        // Similar to above, nanos can't overflow.
162        let mut nsec = self.tv_nsec.as_inner() as i32 - other.subsec_nanos() as i32;
163        if nsec < 0 {
164            nsec += NSEC_PER_SEC as i32;
165            secs = secs.checked_sub(1)?;
166        }
167        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
168    }
169
170    #[allow(dead_code)]
171    pub fn to_timespec(&self) -> Option<libc::timespec> {
172        Some({
173            let mut ts = libc::timespec::default();
174            ts.tv_sec = self.tv_sec.try_into().ok()?;
175            ts.tv_nsec = self.tv_nsec.as_inner().try_into().ok()?;
176            ts
177        })
178    }
179
180    // On QNX Neutrino, the maximum timespec for e.g. pthread_cond_timedwait
181    // is 2^64 nanoseconds
182    #[cfg(target_os = "nto")]
183    pub(in crate::sys) fn to_timespec_capped(&self) -> Option<libc::timespec> {
184        // Check if timeout in nanoseconds would fit into an u64
185        if (self.tv_nsec.as_inner() as u64)
186            .checked_add((self.tv_sec as u64).checked_mul(NSEC_PER_SEC)?)
187            .is_none()
188        {
189            return None;
190        }
191        self.to_timespec()
192    }
193
194    #[cfg(all(
195        target_os = "linux",
196        target_env = "gnu",
197        target_pointer_width = "32",
198        not(target_arch = "riscv32")
199    ))]
200    pub fn to_timespec64(&self) -> __timespec64 {
201        __timespec64::new(self.tv_sec, self.tv_nsec.as_inner() as _)
202    }
203}
204
205#[cfg(all(
206    target_os = "linux",
207    target_env = "gnu",
208    target_pointer_width = "32",
209    not(target_arch = "riscv32")
210))]
211#[repr(C)]
212pub(crate) struct __timespec64 {
213    pub(crate) tv_sec: i64,
214    #[cfg(target_endian = "big")]
215    _padding: i32,
216    pub(crate) tv_nsec: i32,
217    #[cfg(target_endian = "little")]
218    _padding: i32,
219}
220
221#[cfg(all(
222    target_os = "linux",
223    target_env = "gnu",
224    target_pointer_width = "32",
225    not(target_arch = "riscv32")
226))]
227impl __timespec64 {
228    pub(crate) fn new(tv_sec: i64, tv_nsec: i32) -> Self {
229        Self { tv_sec, tv_nsec, _padding: 0 }
230    }
231}
std/sys/pal/unix/time.rs

std/sys/pal/unix/
time.rs
