Move WebIDL constants machinery to bindings::constant

components/script/dom/bindings/constant.rs

@@ -0,0 +1,65 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+//! WebIDL constants.
+
+use js::jsapi::{HandleObject, JSContext, JSPROP_ENUMERATE, JSPROP_PERMANENT};
+use js::jsapi::{JSPROP_READONLY, JS_DefineProperty};
+use js::jsval::{BooleanValue, DoubleValue, Int32Value, JSVal, NullValue, UInt32Value};
+use libc;
+
+/// Representation of an IDL constant.
+#[derive(Clone)]
+pub struct ConstantSpec {
+    /// name of the constant.
+    pub name: &'static [u8],
+    /// value of the constant.
+    pub value: ConstantVal,
+}
+
+/// Representation of an IDL constant value.
+#[derive(Clone)]
+pub enum ConstantVal {
+    /// `long` constant.
+    IntVal(i32),
+    /// `unsigned long` constant.
+    UintVal(u32),
+    /// `double` constant.
+    DoubleVal(f64),
+    /// `boolean` constant.
+    BoolVal(bool),
+    /// `null` constant.
+    NullVal,
+}
+
+impl ConstantSpec {
+    /// Returns a `JSVal` that represents the value of this `ConstantSpec`.
+    pub fn get_value(&self) -> JSVal {
+        match self.value {
+            ConstantVal::NullVal => NullValue(),
+            ConstantVal::IntVal(i) => Int32Value(i),
+            ConstantVal::UintVal(u) => UInt32Value(u),
+            ConstantVal::DoubleVal(d) => DoubleValue(d),
+            ConstantVal::BoolVal(b) => BooleanValue(b),
+        }
+    }
+}
+
+/// Defines constants on `obj`.
+/// Fails on JSAPI failure.
+pub unsafe fn define_constants(
+        cx: *mut JSContext,
+        obj: HandleObject,
+        constants: &[ConstantSpec]) {
+    for spec in constants {
+        rooted!(in(cx) let value = spec.get_value());
+        assert!(JS_DefineProperty(cx,
+                                  obj,
+                                  spec.name.as_ptr() as *const libc::c_char,
+                                  value.handle(),
+                                  JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT,
+                                  None,
+                                  None));
+    }
+}