1 files changed, 57 insertions, 0 deletions
diff --git a/components/script_bindings/num.rs b/components/script_bindings/num.rs
new file mode 100644
index 00000000000..58b12f6cb7f
--- /dev/null
+++ b/components/script_bindings/num.rs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! The `Finite<T>` struct.
+
+use std::default::Default;
+use std::ops::Deref;
+
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use num_traits::Float;
+
+/// Encapsulates the IDL restricted float type.
+#[derive(Clone, Copy, Eq, JSTraceable, PartialEq)]
+pub struct Finite<T: Float>(T);
+
+impl<T: Float> Finite<T> {
+    /// Create a new `Finite<T: Float>` safely.
+    pub fn new(value: T) -> Option<Finite<T>> {
+        if value.is_finite() {
+            Some(Finite(value))
+        } else {
+            None
+        }
+    }
+
+    /// Create a new `Finite<T: Float>`.
+    #[inline]
+    pub fn wrap(value: T) -> Finite<T> {
+        assert!(
+            value.is_finite(),
+            "Finite<T> doesn't encapsulate unrestricted value."
+        );
+        Finite(value)
+    }
+}
+
+impl<T: Float> Deref for Finite<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        let Finite(value) = self;
+        value
+    }
+}
+
+impl<T: Float + MallocSizeOf> MallocSizeOf for Finite<T> {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        (**self).size_of(ops)
+    }
+}
+
+impl<T: Float + Default> Default for Finite<T> {
+    fn default() -> Finite<T> {
+        Finite::wrap(T::default())
+    }
+}