1 files changed, 80 insertions, 0 deletions
diff --git a/third_party/rust/euclid/src/trig.rs b/third_party/rust/euclid/src/trig.rs
new file mode 100644
index 0000000000..907ffb0baa
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+++ b/third_party/rust/euclid/src/trig.rs
@@ -0,0 +1,80 @@
+// Copyright 2013 The Servo Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Trait for basic trigonometry functions, so they can be used on generic numeric types
+pub trait Trig {
+    fn sin(self) -> Self;
+    fn cos(self) -> Self;
+    fn tan(self) -> Self;
+    fn fast_atan2(y: Self, x: Self) -> Self;
+    fn degrees_to_radians(deg: Self) -> Self;
+    fn radians_to_degrees(rad: Self) -> Self;
+}
+
+macro_rules! trig {
+    ($ty:ident) => {
+        impl Trig for $ty {
+            #[inline]
+            fn sin(self) -> $ty {
+                num_traits::Float::sin(self)
+            }
+            #[inline]
+            fn cos(self) -> $ty {
+                num_traits::Float::cos(self)
+            }
+            #[inline]
+            fn tan(self) -> $ty {
+                num_traits::Float::tan(self)
+            }
+
+            /// A slightly faster approximation of `atan2`.
+            ///
+            /// Note that it does not deal with the case where both x and y are 0.
+            #[inline]
+            fn fast_atan2(y: $ty, x: $ty) -> $ty {
+                // This macro is used with f32 and f64 and clippy warns about the extra
+                // precision with f32.
+                #![cfg_attr(feature = "cargo-clippy", allow(excessive_precision))]
+
+                // See https://math.stackexchange.com/questions/1098487/atan2-faster-approximation#1105038
+                use core::$ty::consts;
+                let x_abs = num_traits::Float::abs(x);
+                let y_abs = num_traits::Float::abs(y);
+                let a = x_abs.min(y_abs) / x_abs.max(y_abs);
+                let s = a * a;
+                let mut result =
+                    ((-0.046_496_474_9 * s + 0.159_314_22) * s - 0.327_622_764) * s * a + a;
+                if y_abs > x_abs {
+                    result = consts::FRAC_PI_2 - result;
+                }
+                if x < 0.0 {
+                    result = consts::PI - result
+                }
+                if y < 0.0 {
+                    result = -result
+                }
+
+                result
+            }
+
+            #[inline]
+            fn degrees_to_radians(deg: Self) -> Self {
+                deg.to_radians()
+            }
+
+            #[inline]
+            fn radians_to_degrees(rad: Self) -> Self {
+                rad.to_degrees()
+            }
+        }
+    };
+}
+
+trig!(f32);
+trig!(f64);