Move Timespec impl to common to use in Hermit

Author: stepancheg

library/std/src/sys/pal/common/mod.rs

@@ -11,6 +11,7 @@
 #![allow(dead_code)]
 
 pub mod small_c_string;
+pub(crate) mod timespec;
 
 #[cfg(test)]
 mod tests;

library/std/src/sys/pal/common/timespec.rs

@@ -0,0 +1,186 @@
+use core::num::niche_types::Nanoseconds;
+
+use crate::io;
+use crate::time::Duration;
+
+const NSEC_PER_SEC: u64 = 1_000_000_000;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub(crate) struct Timespec {
+    pub(crate) tv_sec: i64,
+    pub(crate) tv_nsec: Nanoseconds,
+}
+
+impl Timespec {
+    pub(crate) const MAX: Timespec = unsafe { Self::new_unchecked(i64::MAX, 1_000_000_000 - 1) };
+
+    // As described below, on Apple OS, dates before epoch are represented differently.
+    // This is not an issue here however, because we are using tv_sec = i64::MIN,
+    // which will cause the compatibility wrapper to not be executed at all.
+    pub(crate) const MIN: Timespec = unsafe { Self::new_unchecked(i64::MIN, 0) };
+
+    const unsafe fn new_unchecked(tv_sec: i64, tv_nsec: i64) -> Timespec {
+        Timespec { tv_sec, tv_nsec: unsafe { Nanoseconds::new_unchecked(tv_nsec as u32) } }
+    }
+
+    pub const fn zero() -> Timespec {
+        unsafe { Self::new_unchecked(0, 0) }
+    }
+
+    pub(crate) const fn new(tv_sec: i64, tv_nsec: i64) -> Result<Timespec, io::Error> {
+        // 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(target_vendor = "apple")]
+        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)
+            };
+        if tv_nsec >= 0 && tv_nsec < NSEC_PER_SEC as i64 {
+            Ok(unsafe { Self::new_unchecked(tv_sec, tv_nsec) })
+        } else {
+            Err(io::const_error!(io::ErrorKind::InvalidData, "invalid timestamp"))
+        }
+    }
+
+    #[cfg(any(unix, target_os = "wasi"))]
+    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::time::__timespec64;
+            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(
+                    clockid: libc::clockid_t,
+                    tp: *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();
+                let t = unsafe { t.assume_init() };
+                return Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap();
+            }
+        }
+
+        let mut t = MaybeUninit::uninit();
+        cvt(unsafe { libc::clock_gettime(clock, t.as_mut_ptr()) }).unwrap();
+        let t = unsafe { t.assume_init() };
+        Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap()
+    }
+
+    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
+        // When a >= b, the difference fits in u64.
+        fn sub_ge_to_unsigned(a: i64, b: i64) -> u64 {
+            debug_assert!(a >= b);
+            a.wrapping_sub(b).cast_unsigned()
+        }
+
+        if self >= other {
+            let (secs, nsec) = if self.tv_nsec.as_inner() >= other.tv_nsec.as_inner() {
+                (
+                    sub_ge_to_unsigned(self.tv_sec, other.tv_sec),
+                    self.tv_nsec.as_inner() - other.tv_nsec.as_inner(),
+                )
+            } else {
+                // Following sequence of assertions explain why `self.tv_sec - 1` does not underflow.
+                debug_assert!(self.tv_nsec < other.tv_nsec);
+                debug_assert!(self.tv_sec > other.tv_sec);
+                debug_assert!(self.tv_sec > i64::MIN);
+                (
+                    sub_ge_to_unsigned(self.tv_sec - 1, other.tv_sec),
+                    self.tv_nsec.as_inner() + (NSEC_PER_SEC as u32) - other.tv_nsec.as_inner(),
+                )
+            };
+
+            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.as_inner();
+        if nsec >= NSEC_PER_SEC as u32 {
+            nsec -= NSEC_PER_SEC as u32;
+            secs = secs.checked_add(1)?;
+        }
+        Some(unsafe { Timespec::new_unchecked(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.as_inner() as i32 - other.subsec_nanos() as i32;
+        if nsec < 0 {
+            nsec += NSEC_PER_SEC as i32;
+            secs = secs.checked_sub(1)?;
+        }
+        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
+    }
+
+    #[allow(dead_code)]
+    #[cfg(any(unix, target_os = "wasi"))]
+    pub fn to_timespec(&self) -> Option<libc::timespec> {
+        Some(libc::timespec {
+            tv_sec: self.tv_sec.try_into().ok()?,
+            tv_nsec: self.tv_nsec.as_inner().try_into().ok()?,
+        })
+    }
+
+    // On QNX Neutrino, the maximum timespec for e.g. pthread_cond_timedwait
+    // is 2^64 nanoseconds
+    #[cfg(target_os = "nto")]
+    pub(in crate::sys) fn to_timespec_capped(&self) -> Option<libc::timespec> {
+        // Check if timeout in nanoseconds would fit into an u64
+        if (self.tv_nsec.as_inner() 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) -> crate::sys::time::__timespec64 {
+        crate::sys::time::__timespec64::new(self.tv_sec, self.tv_nsec.as_inner() as _)
+    }
+}

library/std/src/sys/pal/hermit/time.rs

@@ -213,9 +213,9 @@ pub struct SystemTime(Timespec);
 pub const UNIX_EPOCH: SystemTime = SystemTime(Timespec::zero());
 
 impl SystemTime {
-    pub const MAX: SystemTime = SystemTime { t: Timespec::MAX };
+    pub const MAX: SystemTime = SystemTime(Timespec::MAX);
 
-    pub const MIN: SystemTime = SystemTime { t: Timespec::MIN };
+    pub const MIN: SystemTime = SystemTime(Timespec::MIN);
 
     pub fn new(tv_sec: i64, tv_nsec: i32) -> SystemTime {
         SystemTime(Timespec::new(tv_sec, tv_nsec))

library/std/src/sys/pal/unix/futex.rs

@@ -28,9 +28,9 @@ pub type SmallPrimitive = u32;
 /// Returns false on timeout, and true in all other cases.
 #[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
 pub fn futex_wait(futex: &Atomic<u32>, expected: u32, timeout: Option<Duration>) -> bool {
-    use super::time::Timespec;
     use crate::ptr::null;
     use crate::sync::atomic::Ordering::Relaxed;
+    use crate::sys::common::timespec::Timespec;
 
     // Calculate the timeout as an absolute timespec.
     //