1 files changed, 251 insertions, 0 deletions
diff --git a/src/f32/math.rs b/src/f32/math.rs
new file mode 100644
index 0000000..3e25875
--- /dev/null
+++ b/src/f32/math.rs
@@ -0,0 +1,251 @@
+/// Returns a very close approximation of `self.clamp(-1.0, 1.0).acos()`.
+#[inline]
+fn acos_approx_f32(v: f32) -> f32 {
+    // Based on https://github.com/microsoft/DirectXMath `XMScalarAcos`
+    // Clamp input to [-1,1].
+    let nonnegative = v >= 0.0;
+    let x = abs(v);
+    let mut omx = 1.0 - x;
+    if omx < 0.0 {
+        omx = 0.0;
+    }
+    let root = sqrt(omx);
+
+    // 7-degree minimax approximation
+    #[allow(clippy::approx_constant)]
+    let mut result =
+        ((((((-0.001_262_491_1 * x + 0.006_670_09) * x - 0.017_088_126) * x + 0.030_891_88) * x
+            - 0.050_174_303)
+            * x
+            + 0.088_978_99)
+            * x
+            - 0.214_598_8)
+            * x
+            + 1.570_796_3;
+    result *= root;
+
+    // acos(x) = pi - acos(-x) when x < 0
+    if nonnegative {
+        result
+    } else {
+        core::f32::consts::PI - result
+    }
+}
+
+#[cfg(feature = "libm")]
+mod libm_math {
+    #[inline(always)]
+    pub(crate) fn abs(f: f32) -> f32 {
+        libm::fabsf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn acos_approx(f: f32) -> f32 {
+        super::acos_approx_f32(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn asin(f: f32) -> f32 {
+        libm::asinf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn atan2(f: f32, other: f32) -> f32 {
+        libm::atan2f(f, other)
+    }
+
+    #[allow(unused)]
+    #[inline(always)]
+    pub(crate) fn sin(f: f32) -> f32 {
+        libm::sinf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn sin_cos(f: f32) -> (f32, f32) {
+        libm::sincosf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn tan(f: f32) -> f32 {
+        libm::tanf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn sqrt(f: f32) -> f32 {
+        libm::sqrtf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn copysign(f: f32, sign: f32) -> f32 {
+        libm::copysignf(f, sign)
+    }
+
+    #[inline(always)]
+    pub(crate) fn signum(f: f32) -> f32 {
+        if f.is_nan() {
+            f32::NAN
+        } else {
+            copysign(1.0, f)
+        }
+    }
+
+    #[inline(always)]
+    pub(crate) fn round(f: f32) -> f32 {
+        libm::roundf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn trunc(f: f32) -> f32 {
+        libm::truncf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn ceil(f: f32) -> f32 {
+        libm::ceilf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn floor(f: f32) -> f32 {
+        libm::floorf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn exp(f: f32) -> f32 {
+        libm::expf(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn powf(f: f32, n: f32) -> f32 {
+        libm::powf(f, n)
+    }
+
+    #[inline(always)]
+    pub(crate) fn mul_add(a: f32, b: f32, c: f32) -> f32 {
+        libm::fmaf(a, b, c)
+    }
+
+    #[inline]
+    pub fn div_euclid(a: f32, b: f32) -> f32 {
+        // Based on https://doc.rust-lang.org/src/std/f32.rs.html#293
+        let q = libm::truncf(a / b);
+        if a % b < 0.0 {
+            return if b > 0.0 { q - 1.0 } else { q + 1.0 };
+        }
+        q
+    }
+
+    #[inline]
+    pub fn rem_euclid(a: f32, b: f32) -> f32 {
+        let r = a % b;
+        if r < 0.0 {
+            r + abs(b)
+        } else {
+            r
+        }
+    }
+}
+
+#[cfg(not(feature = "libm"))]
+mod std_math {
+    #[inline(always)]
+    pub(crate) fn abs(f: f32) -> f32 {
+        f32::abs(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn acos_approx(f: f32) -> f32 {
+        super::acos_approx_f32(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn asin(f: f32) -> f32 {
+        f32::asin(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn atan2(f: f32, other: f32) -> f32 {
+        f32::atan2(f, other)
+    }
+
+    #[allow(unused)]
+    #[inline(always)]
+    pub(crate) fn sin(f: f32) -> f32 {
+        f32::sin(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn sin_cos(f: f32) -> (f32, f32) {
+        f32::sin_cos(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn tan(f: f32) -> f32 {
+        f32::tan(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn sqrt(f: f32) -> f32 {
+        f32::sqrt(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn copysign(f: f32, sign: f32) -> f32 {
+        f32::copysign(f, sign)
+    }
+
+    #[inline(always)]
+    pub(crate) fn signum(f: f32) -> f32 {
+        f32::signum(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn round(f: f32) -> f32 {
+        f32::round(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn trunc(f: f32) -> f32 {
+        f32::trunc(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn ceil(f: f32) -> f32 {
+        f32::ceil(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn floor(f: f32) -> f32 {
+        f32::floor(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn exp(f: f32) -> f32 {
+        f32::exp(f)
+    }
+
+    #[inline(always)]
+    pub(crate) fn powf(f: f32, n: f32) -> f32 {
+        f32::powf(f, n)
+    }
+
+    #[inline(always)]
+    pub(crate) fn mul_add(a: f32, b: f32, c: f32) -> f32 {
+        f32::mul_add(a, b, c)
+    }
+
+    #[inline]
+    pub fn div_euclid(a: f32, b: f32) -> f32 {
+        f32::div_euclid(a, b)
+    }
+
+    #[inline]
+    pub fn rem_euclid(a: f32, b: f32) -> f32 {
+        f32::rem_euclid(a, b)
+    }
+}
+
+#[cfg(feature = "libm")]
+pub(crate) use libm_math::*;
+
+#[cfg(not(feature = "libm"))]
+pub(crate) use std_math::*;