1 files changed, 129 insertions, 0 deletions
diff --git a/third_party/rust/instant/src/wasm.rs b/third_party/rust/instant/src/wasm.rs
new file mode 100644
index 0000000000..829ef3bd72
--- /dev/null
+++ b/third_party/rust/instant/src/wasm.rs
@@ -0,0 +1,129 @@
+use std::ops::{Add, AddAssign, Sub, SubAssign};
+use std::time::Duration;
+
+#[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Hash)]
+pub struct Instant(Duration);
+
+impl Ord for Instant {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.partial_cmp(other)
+            .expect("an instant should never be NaN or Inf.")
+    }
+}
+impl Eq for Instant {}
+
+impl Instant {
+    #[inline]
+    pub fn now() -> Self {
+        Instant(duration_from_f64(now()))
+    }
+
+    #[inline]
+    pub fn duration_since(&self, earlier: Instant) -> Duration {
+        assert!(
+            earlier.0 <= self.0,
+            "`earlier` cannot be later than `self`."
+        );
+        self.0 - earlier.0
+    }
+
+    #[inline]
+    pub fn elapsed(&self) -> Duration {
+        Self::now().duration_since(*self)
+    }
+
+    /// Returns `Some(t)` where `t` is the time `self + duration` if `t` can be represented as
+    /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
+    /// otherwise.
+    #[inline]
+    pub fn checked_add(&self, duration: Duration) -> Option<Instant> {
+        self.0.checked_add(duration).map(Instant)
+    }
+
+    /// Returns `Some(t)` where `t` is the time `self - duration` if `t` can be represented as
+    /// `Instant` (which means it's inside the bounds of the underlying data structure), `None`
+    /// otherwise.
+    #[inline]
+    pub fn checked_sub(&self, duration: Duration) -> Option<Instant> {
+        self.0.checked_sub(duration).map(Instant)
+    }
+}
+
+impl Add<Duration> for Instant {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, rhs: Duration) -> Self {
+        Instant(self.0 + rhs)
+    }
+}
+
+impl AddAssign<Duration> for Instant {
+    #[inline]
+    fn add_assign(&mut self, rhs: Duration) {
+        self.0 += rhs
+    }
+}
+
+impl Sub<Duration> for Instant {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, rhs: Duration) -> Self {
+        Instant(self.0 - rhs)
+    }
+}
+
+impl Sub<Instant> for Instant {
+    type Output = Duration;
+
+    #[inline]
+    fn sub(self, rhs: Instant) -> Duration {
+        self.duration_since(rhs)
+    }
+}
+
+impl SubAssign<Duration> for Instant {
+    #[inline]
+    fn sub_assign(&mut self, rhs: Duration) {
+        self.0 -= rhs
+    }
+}
+
+fn duration_from_f64(millis: f64) -> Duration {
+    Duration::from_millis(millis.trunc() as u64)
+        + Duration::from_nanos((millis.fract() * 1.0e6) as u64)
+}
+
+#[cfg(all(feature = "stdweb", not(feature = "wasm-bindgen")))]
+#[allow(unused_results)] // Needed because the js macro triggers it.
+pub fn now() -> f64 {
+    use stdweb::unstable::TryInto;
+
+    // https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
+    let v = js! { return performance.now(); };
+    v.try_into().unwrap()
+}
+
+#[cfg(feature = "wasm-bindgen")]
+pub fn now() -> f64 {
+    use wasm_bindgen_rs::prelude::*;
+    use wasm_bindgen_rs::JsCast;
+    js_sys::Reflect::get(&js_sys::global(), &JsValue::from_str("performance"))
+        .expect("failed to get performance from global object")
+        .unchecked_into::<web_sys::Performance>()
+        .now()
+}
+
+// The JS now function is in a module so it won't have to be renamed
+#[cfg(not(any(feature = "wasm-bindgen", feature = "stdweb")))]
+mod js {
+    extern "C" {
+        pub fn now() -> f64;
+    }
+}
+// Make the unsafe extern function "safe" so it can be called like the other 'now' functions
+#[cfg(not(any(feature = "wasm-bindgen", feature = "stdweb")))]
+pub fn now() -> f64 {
+    unsafe { js::now() }
+}