1 files changed, 330 insertions, 0 deletions
diff --git a/library/std/src/sys/pal/unix/time.rs b/library/std/src/sys/pal/unix/time.rs
new file mode 100644
index 00000000000..f62eb828ee5
--- /dev/null
+++ b/library/std/src/sys/pal/unix/time.rs
@@ -0,0 +1,330 @@
+use crate::fmt;
+use crate::time::Duration;
+
+const NSEC_PER_SEC: u64 = 1_000_000_000;
+pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
+#[allow(dead_code)] // Used for pthread condvar timeouts
+pub const TIMESPEC_MAX: libc::timespec =
+    libc::timespec { tv_sec: <libc::time_t>::MAX, tv_nsec: 1_000_000_000 - 1 };
+
+// This additional constant is only used when calling
+// `libc::pthread_cond_timedwait`.
+#[cfg(target_os = "nto")]
+pub(super) const TIMESPEC_MAX_CAPPED: libc::timespec = libc::timespec {
+    tv_sec: (u64::MAX / NSEC_PER_SEC) as i64,
+    tv_nsec: (u64::MAX % NSEC_PER_SEC) as i64,
+};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(0)]
+#[rustc_layout_scalar_valid_range_end(999_999_999)]
+struct Nanoseconds(u32);
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct SystemTime {
+    pub(crate) t: Timespec,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct Timespec {
+    tv_sec: i64,
+    tv_nsec: Nanoseconds,
+}
+
+impl SystemTime {
+    #[cfg_attr(any(target_os = "horizon", target_os = "hurd"), allow(unused))]
+    pub fn new(tv_sec: i64, tv_nsec: i64) -> SystemTime {
+        SystemTime { t: Timespec::new(tv_sec, tv_nsec) }
+    }
+
+    pub fn now() -> SystemTime {
+        SystemTime { t: Timespec::now(libc::CLOCK_REALTIME) }
+    }
+
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.t.sub_timespec(&other.t)
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime { t: self.t.checked_add_duration(other)? })
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime { t: self.t.checked_sub_duration(other)? })
+    }
+}
+
+impl From<libc::timespec> for SystemTime {
+    fn from(t: libc::timespec) -> SystemTime {
+        SystemTime { t: Timespec::from(t) }
+    }
+}
+
+impl fmt::Debug for SystemTime {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("SystemTime")
+            .field("tv_sec", &self.t.tv_sec)
+            .field("tv_nsec", &self.t.tv_nsec.0)
+            .finish()
+    }
+}
+
+impl Timespec {
+    pub const fn zero() -> Timespec {
+        Timespec::new(0, 0)
+    }
+
+    const fn new(tv_sec: i64, tv_nsec: i64) -> Timespec {
+        // On Apple OS, dates before epoch are represented differently than on other
+        // Unix platforms: e.g. 1/10th of a second before epoch is represented as `seconds=-1`
+        // and `nanoseconds=100_000_000` on other platforms, but is `seconds=0` and
+        // `nanoseconds=-900_000_000` on Apple OS.
+        //
+        // To compensate, we first detect this special case by checking if both
+        // seconds and nanoseconds are in range, and then correct the value for seconds
+        // and nanoseconds to match the common unix representation.
+        //
+        // Please note that Apple OS nonetheless accepts the standard unix format when
+        // setting file times, which makes this compensation round-trippable and generally
+        // transparent.
+        #[cfg(any(
+            target_os = "macos",
+            target_os = "ios",
+            target_os = "tvos",
+            target_os = "watchos"
+        ))]
+        let (tv_sec, tv_nsec) =
+            if (tv_sec <= 0 && tv_sec > i64::MIN) && (tv_nsec < 0 && tv_nsec > -1_000_000_000) {
+                (tv_sec - 1, tv_nsec + 1_000_000_000)
+            } else {
+                (tv_sec, tv_nsec)
+            };
+        assert!(tv_nsec >= 0 && tv_nsec < NSEC_PER_SEC as i64);
+        // SAFETY: The assert above checks tv_nsec is within the valid range
+        Timespec { tv_sec, tv_nsec: unsafe { Nanoseconds(tv_nsec as u32) } }
+    }
+
+    pub fn now(clock: libc::clockid_t) -> Timespec {
+        use crate::mem::MaybeUninit;
+        use crate::sys::cvt;
+
+        // Try to use 64-bit time in preparation for Y2038.
+        #[cfg(all(
+            target_os = "linux",
+            target_env = "gnu",
+            target_pointer_width = "32",
+            not(target_arch = "riscv32")
+        ))]
+        {
+            use crate::sys::weak::weak;
+
+            // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
+            // and it handles both vDSO calls and ENOSYS fallbacks itself.
+            weak!(fn __clock_gettime64(libc::clockid_t, *mut __timespec64) -> libc::c_int);
+
+            if let Some(clock_gettime64) = __clock_gettime64.get() {
+                let mut t = MaybeUninit::uninit();
+                cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
+                return Timespec::from(unsafe { t.assume_init() });
+            }
+        }
+
+        let mut t = MaybeUninit::uninit();
+        cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
+        Timespec::from(unsafe { t.assume_init() })
+    }
+
+    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
+        if self >= other {
+            // NOTE(eddyb) two aspects of this `if`-`else` are required for LLVM
+            // to optimize it into a branchless form (see also #75545):
+            //
+            // 1. `self.tv_sec - other.tv_sec` shows up as a common expression
+            //    in both branches, i.e. the `else` must have its `- 1`
+            //    subtraction after the common one, not interleaved with it
+            //    (it used to be `self.tv_sec - 1 - other.tv_sec`)
+            //
+            // 2. the `Duration::new` call (or any other additional complexity)
+            //    is outside of the `if`-`else`, not duplicated in both branches
+            //
+            // Ideally this code could be rearranged such that it more
+            // directly expresses the lower-cost behavior we want from it.
+            let (secs, nsec) = if self.tv_nsec.0 >= other.tv_nsec.0 {
+                ((self.tv_sec - other.tv_sec) as u64, self.tv_nsec.0 - other.tv_nsec.0)
+            } else {
+                (
+                    (self.tv_sec - other.tv_sec - 1) as u64,
+                    self.tv_nsec.0 + (NSEC_PER_SEC as u32) - other.tv_nsec.0,
+                )
+            };
+
+            Ok(Duration::new(secs, nsec))
+        } else {
+            match other.sub_timespec(self) {
+                Ok(d) => Err(d),
+                Err(d) => Ok(d),
+            }
+        }
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
+        let mut secs = self.tv_sec.checked_add_unsigned(other.as_secs())?;
+
+        // Nano calculations can't overflow because nanos are <1B which fit
+        // in a u32.
+        let mut nsec = other.subsec_nanos() + self.tv_nsec.0;
+        if nsec >= NSEC_PER_SEC as u32 {
+            nsec -= NSEC_PER_SEC as u32;
+            secs = secs.checked_add(1)?;
+        }
+        Some(Timespec::new(secs, nsec.into()))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
+        let mut secs = self.tv_sec.checked_sub_unsigned(other.as_secs())?;
+
+        // Similar to above, nanos can't overflow.
+        let mut nsec = self.tv_nsec.0 as i32 - other.subsec_nanos() as i32;
+        if nsec < 0 {
+            nsec += NSEC_PER_SEC as i32;
+            secs = secs.checked_sub(1)?;
+        }
+        Some(Timespec::new(secs, nsec.into()))
+    }
+
+    #[allow(dead_code)]
+    pub fn to_timespec(&self) -> Option<libc::timespec> {
+        Some(libc::timespec {
+            tv_sec: self.tv_sec.try_into().ok()?,
+            tv_nsec: self.tv_nsec.0.try_into().ok()?,
+        })
+    }
+
+    // On QNX Neutrino, the maximum timespec for e.g. pthread_cond_timedwait
+    // is 2^64 nanoseconds
+    #[cfg(target_os = "nto")]
+    pub(super) fn to_timespec_capped(&self) -> Option<libc::timespec> {
+        // Check if timeout in nanoseconds would fit into an u64
+        if (self.tv_nsec.0 as u64)
+            .checked_add((self.tv_sec as u64).checked_mul(NSEC_PER_SEC)?)
+            .is_none()
+        {
+            return None;
+        }
+        self.to_timespec()
+    }
+
+    #[cfg(all(
+        target_os = "linux",
+        target_env = "gnu",
+        target_pointer_width = "32",
+        not(target_arch = "riscv32")
+    ))]
+    pub fn to_timespec64(&self) -> __timespec64 {
+        __timespec64::new(self.tv_sec, self.tv_nsec.0 as _)
+    }
+}
+
+impl From<libc::timespec> for Timespec {
+    fn from(t: libc::timespec) -> Timespec {
+        Timespec::new(t.tv_sec as i64, t.tv_nsec as i64)
+    }
+}
+
+#[cfg(all(
+    target_os = "linux",
+    target_env = "gnu",
+    target_pointer_width = "32",
+    not(target_arch = "riscv32")
+))]
+#[repr(C)]
+pub(crate) struct __timespec64 {
+    pub(crate) tv_sec: i64,
+    #[cfg(target_endian = "big")]
+    _padding: i32,
+    pub(crate) tv_nsec: i32,
+    #[cfg(target_endian = "little")]
+    _padding: i32,
+}
+
+#[cfg(all(
+    target_os = "linux",
+    target_env = "gnu",
+    target_pointer_width = "32",
+    not(target_arch = "riscv32")
+))]
+impl __timespec64 {
+    pub(crate) fn new(tv_sec: i64, tv_nsec: i32) -> Self {
+        Self { tv_sec, tv_nsec, _padding: 0 }
+    }
+}
+
+#[cfg(all(
+    target_os = "linux",
+    target_env = "gnu",
+    target_pointer_width = "32",
+    not(target_arch = "riscv32")
+))]
+impl From<__timespec64> for Timespec {
+    fn from(t: __timespec64) -> Timespec {
+        Timespec::new(t.tv_sec, t.tv_nsec.into())
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Instant {
+    t: Timespec,
+}
+
+impl Instant {
+    pub fn now() -> Instant {
+        // https://www.manpagez.com/man/3/clock_gettime/
+        //
+        // CLOCK_UPTIME_RAW   clock that increments monotonically, in the same man-
+        //                    ner as CLOCK_MONOTONIC_RAW, but that does not incre-
+        //                    ment while the system is asleep.  The returned value
+        //                    is identical to the result of mach_absolute_time()
+        //                    after the appropriate mach_timebase conversion is
+        //                    applied.
+        //
+        // Instant on macos was historically implemented using mach_absolute_time;
+        // we preserve this value domain out of an abundance of caution.
+        #[cfg(any(
+            target_os = "macos",
+            target_os = "ios",
+            target_os = "watchos",
+            target_os = "tvos"
+        ))]
+        const clock_id: libc::clockid_t = libc::CLOCK_UPTIME_RAW;
+        #[cfg(not(any(
+            target_os = "macos",
+            target_os = "ios",
+            target_os = "watchos",
+            target_os = "tvos"
+        )))]
+        const clock_id: libc::clockid_t = libc::CLOCK_MONOTONIC;
+        Instant { t: Timespec::now(clock_id) }
+    }
+
+    pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
+        self.t.sub_timespec(&other.t).ok()
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
+        Some(Instant { t: self.t.checked_add_duration(other)? })
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
+        Some(Instant { t: self.t.checked_sub_duration(other)? })
+    }
+}
+
+impl fmt::Debug for Instant {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Instant")
+            .field("tv_sec", &self.t.tv_sec)
+            .field("tv_nsec", &self.t.tv_nsec.0)
+            .finish()
+    }
+}