1 files changed, 346 insertions, 0 deletions
diff --git a/library/std/src/sys/unix/time.rs b/library/std/src/sys/unix/time.rs
new file mode 100644
index 000000000..dff973f59
--- /dev/null
+++ b/library/std/src/sys/unix/time.rs
@@ -0,0 +1,346 @@
+use crate::fmt;
+use crate::time::Duration;
+
+pub use self::inner::Instant;
+
+const NSEC_PER_SEC: u64 = 1_000_000_000;
+pub const UNIX_EPOCH: SystemTime = SystemTime { t: Timespec::zero() };
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct SystemTime {
+    pub(in crate::sys::unix) t: Timespec,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(in crate::sys::unix) struct Timespec {
+    tv_sec: i64,
+    tv_nsec: i64,
+}
+
+impl SystemTime {
+    #[cfg_attr(target_os = "horizon", allow(unused))]
+    pub fn new(tv_sec: i64, tv_nsec: i64) -> SystemTime {
+        SystemTime { t: Timespec::new(tv_sec, tv_nsec) }
+    }
+
+    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)
+            .finish()
+    }
+}
+
+impl Timespec {
+    pub const fn zero() -> Timespec {
+        Timespec { tv_sec: 0, tv_nsec: 0 }
+    }
+
+    fn new(tv_sec: i64, tv_nsec: i64) -> Timespec {
+        Timespec { tv_sec, tv_nsec }
+    }
+
+    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 >= other.tv_nsec {
+                ((self.tv_sec - other.tv_sec) as u64, (self.tv_nsec - other.tv_nsec) as u32)
+            } else {
+                (
+                    (self.tv_sec - other.tv_sec - 1) as u64,
+                    self.tv_nsec as u32 + (NSEC_PER_SEC as u32) - other.tv_nsec as u32,
+                )
+            };
+
+            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 = other
+            .as_secs()
+            .try_into() // <- target type would be `i64`
+            .ok()
+            .and_then(|secs| self.tv_sec.checked_add(secs))?;
+
+        // Nano calculations can't overflow because nanos are <1B which fit
+        // in a u32.
+        let mut nsec = other.subsec_nanos() + self.tv_nsec as u32;
+        if nsec >= NSEC_PER_SEC as u32 {
+            nsec -= NSEC_PER_SEC as u32;
+            secs = secs.checked_add(1)?;
+        }
+        Some(Timespec::new(secs, nsec as i64))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
+        let mut secs = other
+            .as_secs()
+            .try_into() // <- target type would be `i64`
+            .ok()
+            .and_then(|secs| self.tv_sec.checked_sub(secs))?;
+
+        // Similar to above, nanos can't overflow.
+        let mut nsec = self.tv_nsec 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 as i64))
+    }
+
+    #[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.try_into().ok()?,
+        })
+    }
+}
+
+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(any(target_os = "macos", target_os = "ios", target_os = "watchos"))]
+mod inner {
+    use crate::sync::atomic::{AtomicU64, Ordering};
+    use crate::sys::cvt;
+    use crate::sys_common::mul_div_u64;
+    use crate::time::Duration;
+
+    use super::{SystemTime, Timespec, NSEC_PER_SEC};
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+    pub struct Instant {
+        t: u64,
+    }
+
+    #[repr(C)]
+    #[derive(Copy, Clone)]
+    struct mach_timebase_info {
+        numer: u32,
+        denom: u32,
+    }
+    type mach_timebase_info_t = *mut mach_timebase_info;
+    type kern_return_t = libc::c_int;
+
+    impl Instant {
+        pub fn now() -> Instant {
+            extern "C" {
+                fn mach_absolute_time() -> u64;
+            }
+            Instant { t: unsafe { mach_absolute_time() } }
+        }
+
+        pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
+            let diff = self.t.checked_sub(other.t)?;
+            let info = info();
+            let nanos = mul_div_u64(diff, info.numer as u64, info.denom as u64);
+            Some(Duration::new(nanos / NSEC_PER_SEC, (nanos % NSEC_PER_SEC) as u32))
+        }
+
+        pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
+            Some(Instant { t: self.t.checked_add(checked_dur2intervals(other)?)? })
+        }
+
+        pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
+            Some(Instant { t: self.t.checked_sub(checked_dur2intervals(other)?)? })
+        }
+    }
+
+    impl SystemTime {
+        pub fn now() -> SystemTime {
+            use crate::ptr;
+
+            let mut s = libc::timeval { tv_sec: 0, tv_usec: 0 };
+            cvt(unsafe { libc::gettimeofday(&mut s, ptr::null_mut()) }).unwrap();
+            return SystemTime::from(s);
+        }
+    }
+
+    impl From<libc::timeval> for Timespec {
+        fn from(t: libc::timeval) -> Timespec {
+            Timespec::new(t.tv_sec as i64, 1000 * t.tv_usec as i64)
+        }
+    }
+
+    impl From<libc::timeval> for SystemTime {
+        fn from(t: libc::timeval) -> SystemTime {
+            SystemTime { t: Timespec::from(t) }
+        }
+    }
+
+    fn checked_dur2intervals(dur: &Duration) -> Option<u64> {
+        let nanos =
+            dur.as_secs().checked_mul(NSEC_PER_SEC)?.checked_add(dur.subsec_nanos() as u64)?;
+        let info = info();
+        Some(mul_div_u64(nanos, info.denom as u64, info.numer as u64))
+    }
+
+    fn info() -> mach_timebase_info {
+        // INFO_BITS conceptually is an `Option<mach_timebase_info>`. We can do
+        // this in 64 bits because we know 0 is never a valid value for the
+        // `denom` field.
+        //
+        // Encoding this as a single `AtomicU64` allows us to use `Relaxed`
+        // operations, as we are only interested in the effects on a single
+        // memory location.
+        static INFO_BITS: AtomicU64 = AtomicU64::new(0);
+
+        // If a previous thread has initialized `INFO_BITS`, use it.
+        let info_bits = INFO_BITS.load(Ordering::Relaxed);
+        if info_bits != 0 {
+            return info_from_bits(info_bits);
+        }
+
+        // ... otherwise learn for ourselves ...
+        extern "C" {
+            fn mach_timebase_info(info: mach_timebase_info_t) -> kern_return_t;
+        }
+
+        let mut info = info_from_bits(0);
+        unsafe {
+            mach_timebase_info(&mut info);
+        }
+        INFO_BITS.store(info_to_bits(info), Ordering::Relaxed);
+        info
+    }
+
+    #[inline]
+    fn info_to_bits(info: mach_timebase_info) -> u64 {
+        ((info.denom as u64) << 32) | (info.numer as u64)
+    }
+
+    #[inline]
+    fn info_from_bits(bits: u64) -> mach_timebase_info {
+        mach_timebase_info { numer: bits as u32, denom: (bits >> 32) as u32 }
+    }
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "watchos")))]
+mod inner {
+    use crate::fmt;
+    use crate::mem::MaybeUninit;
+    use crate::sys::cvt;
+    use crate::time::Duration;
+
+    use super::{SystemTime, Timespec};
+
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+    pub struct Instant {
+        t: Timespec,
+    }
+
+    impl Instant {
+        pub fn now() -> Instant {
+            Instant { t: Timespec::now(libc::CLOCK_MONOTONIC) }
+        }
+
+        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)
+                .finish()
+        }
+    }
+
+    impl SystemTime {
+        pub fn now() -> SystemTime {
+            SystemTime { t: Timespec::now(libc::CLOCK_REALTIME) }
+        }
+    }
+
+    #[cfg(not(any(target_os = "dragonfly", target_os = "espidf", target_os = "horizon")))]
+    pub type clock_t = libc::c_int;
+    #[cfg(any(target_os = "dragonfly", target_os = "espidf", target_os = "horizon"))]
+    pub type clock_t = libc::c_ulong;
+
+    impl Timespec {
+        pub fn now(clock: clock_t) -> Timespec {
+            // Try to use 64-bit time in preparation for Y2038.
+            #[cfg(all(target_os = "linux", target_env = "gnu", target_pointer_width = "32"))]
+            {
+                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);
+
+                #[repr(C)]
+                struct __timespec64 {
+                    tv_sec: i64,
+                    #[cfg(target_endian = "big")]
+                    _padding: i32,
+                    tv_nsec: i32,
+                    #[cfg(target_endian = "little")]
+                    _padding: i32,
+                }
+
+                if let Some(clock_gettime64) = __clock_gettime64.get() {
+                    let mut t = MaybeUninit::uninit();
+                    cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
+                    let t = unsafe { t.assume_init() };
+                    return Timespec { tv_sec: t.tv_sec, tv_nsec: t.tv_nsec as i64 };
+                }
+            }
+
+            let mut t = MaybeUninit::uninit();
+            cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
+            Timespec::from(unsafe { t.assume_init() })
+        }
+    }
+}