1 files changed, 114 insertions, 0 deletions
diff --git a/library/std/src/sys/itron/time.rs b/library/std/src/sys/itron/time.rs
new file mode 100644
index 000000000..427ea0d80
--- /dev/null
+++ b/library/std/src/sys/itron/time.rs
@@ -0,0 +1,114 @@
+use super::{abi, error::expect_success};
+use crate::{mem::MaybeUninit, time::Duration};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct Instant(abi::SYSTIM);
+
+impl Instant {
+    pub fn now() -> Instant {
+        // Safety: The provided pointer is valid
+        unsafe {
+            let mut out = MaybeUninit::uninit();
+            expect_success(abi::get_tim(out.as_mut_ptr()), &"get_tim");
+            Instant(out.assume_init())
+        }
+    }
+
+    pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
+        self.0.checked_sub(other.0).map(|ticks| {
+            // `SYSTIM` is measured in microseconds
+            Duration::from_micros(ticks)
+        })
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
+        // `SYSTIM` is measured in microseconds
+        let ticks = other.as_micros();
+
+        Some(Instant(self.0.checked_add(ticks.try_into().ok()?)?))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
+        // `SYSTIM` is measured in microseconds
+        let ticks = other.as_micros();
+
+        Some(Instant(self.0.checked_sub(ticks.try_into().ok()?)?))
+    }
+}
+
+/// Split `Duration` into zero or more `RELTIM`s.
+#[inline]
+pub fn dur2reltims(dur: Duration) -> impl Iterator<Item = abi::RELTIM> {
+    // `RELTIM` is microseconds
+    let mut ticks = dur.as_micros();
+
+    crate::iter::from_fn(move || {
+        if ticks == 0 {
+            None
+        } else if ticks <= abi::TMAX_RELTIM as u128 {
+            Some(crate::mem::replace(&mut ticks, 0) as abi::RELTIM)
+        } else {
+            ticks -= abi::TMAX_RELTIM as u128;
+            Some(abi::TMAX_RELTIM)
+        }
+    })
+}
+
+/// Split `Duration` into one or more `TMO`s.
+#[inline]
+fn dur2tmos(dur: Duration) -> impl Iterator<Item = abi::TMO> {
+    // `TMO` is microseconds
+    let mut ticks = dur.as_micros();
+    let mut end = false;
+
+    crate::iter::from_fn(move || {
+        if end {
+            None
+        } else if ticks <= abi::TMAX_RELTIM as u128 {
+            end = true;
+            Some(crate::mem::replace(&mut ticks, 0) as abi::TMO)
+        } else {
+            ticks -= abi::TMAX_RELTIM as u128;
+            Some(abi::TMAX_RELTIM)
+        }
+    })
+}
+
+/// Split `Duration` into one or more API calls with timeout.
+#[inline]
+pub fn with_tmos(dur: Duration, mut f: impl FnMut(abi::TMO) -> abi::ER) -> abi::ER {
+    let mut er = abi::E_TMOUT;
+    for tmo in dur2tmos(dur) {
+        er = f(tmo);
+        if er != abi::E_TMOUT {
+            break;
+        }
+    }
+    er
+}
+
+/// Split `Duration` into one or more API calls with timeout. This function can
+/// handle spurious wakeups.
+#[inline]
+pub fn with_tmos_strong(dur: Duration, mut f: impl FnMut(abi::TMO) -> abi::ER) -> abi::ER {
+    // `TMO` and `SYSTIM` are microseconds.
+    // Clamp at `SYSTIM::MAX` for performance reasons. This shouldn't cause
+    // a problem in practice. (`u64::MAX` μs ≈ 584942 years)
+    let ticks = dur.as_micros().min(abi::SYSTIM::MAX as u128) as abi::SYSTIM;
+
+    let start = Instant::now().0;
+    let mut elapsed = 0;
+    let mut er = abi::E_TMOUT;
+    while elapsed <= ticks {
+        er = f(elapsed.min(abi::TMAX_RELTIM as abi::SYSTIM) as abi::TMO);
+        if er != abi::E_TMOUT {
+            break;
+        }
+        elapsed = Instant::now().0.wrapping_sub(start);
+    }
+
+    er
+}
+
+#[cfg(test)]
+mod tests;