add Math.clz32 method (boa-dev#524)

boa/src/builtins/math/mod.rs

@@ -19,6 +19,7 @@ use crate::{
     exec::Interpreter,
     BoaProfiler,
 };
+use num_traits::cast::ToPrimitive;
 use std::f64;
 
 #[cfg(test)]
@@ -165,6 +166,25 @@ impl Math {
         Ok(args.get(0).map_or(f64::NAN, |x| f64::from(x).ceil()).into())
     }
 
+    /// Get the number of leading zeros in the 32 bit representation of a number
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-math.exp
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/exp
+    pub(crate) fn clz32(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
+        Ok(args
+            .get(0)
+            .and_then(|x| f64::from(x).to_u32())
+            .map_or(32usize, |u| {
+                let s = format!("{:032b}", u);
+                s.chars().take_while(|x| *x == '0').count()
+            })
+            .into())
+    }
+
     /// Get the cosine of a number.
     ///
     /// More information:
@@ -485,6 +505,7 @@ impl Math {
         make_builtin_fn(Self::atan2, "atan2", &math, 2);
         make_builtin_fn(Self::cbrt, "cbrt", &math, 1);
         make_builtin_fn(Self::ceil, "ceil", &math, 1);
+        make_builtin_fn(Self::clz32, "clz32", &math, 1);
         make_builtin_fn(Self::cos, "cos", &math, 1);
         make_builtin_fn(Self::cosh, "cosh", &math, 1);
         make_builtin_fn(Self::exp, "exp", &math, 1);

boa/src/builtins/math/tests.rs

@@ -183,6 +183,36 @@ fn ceil() {
     assert_eq!(c.to_number(), -7_f64);
 }
 
+#[test]
+fn clz32() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+    let init = r#"
+        var a = Math.clz32();
+        var b = Math.clz32({});
+        var c = Math.clz32(1);
+        var d = Math.clz32("1");
+        var e = Math.clz32(4);
+        var f = Math.clz32(Infinity);
+        "#;
+
+    eprintln!("{}", forward(&mut engine, init));
+
+    let a = forward_val(&mut engine, "a").unwrap();
+    let b = forward_val(&mut engine, "b").unwrap();
+    let c = forward_val(&mut engine, "c").unwrap();
+    let d = forward_val(&mut engine, "d").unwrap();
+    let e = forward_val(&mut engine, "e").unwrap();
+    let f = forward_val(&mut engine, "f").unwrap();
+
+    assert_eq!(a.to_number(), 32_f64);
+    assert_eq!(b.to_number(), 32_f64);
+    assert_eq!(c.to_number(), 31_f64);
+    assert_eq!(d.to_number(), 31_f64);
+    assert_eq!(e.to_number(), 29_f64);
+    assert_eq!(f.to_number(), 32_f64);
+}
+
 #[test]
 fn cos() {
     let realm = Realm::create();