Implement pair iterators in WebIDL interfaces.

components/script/dom/bindings/iterable.rs

@@ -0,0 +1,161 @@
+/* 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/. */
+
+#![allow(unsafe_code)]
+
+//! Implementation of `iterable<...>` and `iterable<..., ...>` WebIDL declarations.
+
+use dom::bindings::codegen::Bindings::IterableIteratorBinding::IterableKeyAndValueResult;
+use dom::bindings::codegen::Bindings::IterableIteratorBinding::IterableKeyOrValueResult;
+use dom::bindings::error::Fallible;
+use dom::bindings::global::GlobalRef;
+use dom::bindings::js::{JS, Root};
+use dom::bindings::reflector::{Reflector, Reflectable, reflect_dom_object};
+use dom::bindings::trace::JSTraceable;
+use js::conversions::ToJSValConvertible;
+use js::jsapi::{JSContext, JSObject, MutableHandleValue, MutableHandleObject, HandleValue};
+use js::jsval::UndefinedValue;
+use std::cell::Cell;
+use std::ptr;
+
+/// The values that an iterator will iterate over.
+#[derive(JSTraceable, HeapSizeOf)]
+pub enum IteratorType {
+    /// The keys of the iterable object.
+    Keys,
+    /// The values of the iterable object.
+    Values,
+    /// The keys and values of the iterable object combined.
+    Entries,
+}
+
+/// A DOM object that can be iterated over using a pair value iterator.
+pub trait Iterable {
+    /// The type of the key of the iterator pair.
+    type Key: ToJSValConvertible;
+    /// The type of the value of the iterator pair.
+    type Value: ToJSValConvertible;
+    /// Return the number of entries that can be iterated over.
+    fn get_iterable_length(&self) -> u32;
+    /// Return the value at the provided index.
+    fn get_value_at_index(&self, index: u32) -> Self::Value;
+    /// Return the key at the provided index.
+    fn get_key_at_index(&self, index: u32) -> Self::Key;
+}
+
+/// An iterator over the iterable entries of a given DOM interface.
+//FIXME: #12811 prevents dom_struct with type parameters
+//#[dom_struct]
+#[must_root]
+#[privatize]
+#[derive(JSTraceable)]
+#[derive(HeapSizeOf)]
+pub struct IterableIterator<T: Reflectable + JSTraceable + Iterable> {
+    reflector: Reflector,
+    iterable: JS<T>,
+    type_: IteratorType,
+    index: Cell<u32>,
+}
+
+impl<T: Reflectable + JSTraceable + Iterable> Reflectable for IterableIterator<T> {
+    fn reflector<'a>(&'a self) -> &'a Reflector {
+        &self.reflector
+    }
+    fn init_reflector(&mut self, obj: *mut JSObject) {
+        self.reflector.set_jsobject(obj);
+    }
+}
+
+impl<T: Reflectable + JSTraceable + Iterable> ToJSValConvertible for IterableIterator<T> {
+    #[allow(unsafe_code)]
+    unsafe fn to_jsval(&self,
+                       cx: *mut JSContext,
+                       rval: MutableHandleValue) {
+        let object = Reflectable::reflector(self).get_jsobject();
+        object.to_jsval(cx, rval)
+    }
+}
+
+impl<T: Reflectable + JSTraceable + Iterable> IterableIterator<T> {
+    /// Create a new iterator instance for the provided iterable DOM interface.
+    pub fn new(iterable: &T,
+               type_: IteratorType,
+               wrap: fn(*mut JSContext, GlobalRef, Box<IterableIterator<T>>)
+                     -> Root<Self>) -> Root<Self> {
+        let iterator = box IterableIterator {
+            reflector: Reflector::new(),
+            type_: type_,
+            iterable: JS::from_ref(iterable),
+            index: Cell::new(0),
+        };
+        let global = iterable.global();
+        reflect_dom_object(iterator, global.r(), wrap)
+    }
+
+    /// Return the next value from the iterable object.
+    #[allow(non_snake_case)]
+    pub fn Next(&self, cx: *mut JSContext) -> Fallible<*mut JSObject> {
+        let index = self.index.get();
+        rooted!(in(cx) let mut value = UndefinedValue());
+        rooted!(in(cx) let mut rval = ptr::null_mut());
+        if index >= self.iterable.get_iterable_length() {
+            return dict_return(cx, rval.handle_mut(), true, value.handle())
+                .map(|_| rval.handle().get());
+        }
+        let result = match self.type_ {
+            IteratorType::Keys => {
+                unsafe {
+                    self.iterable.get_key_at_index(index).to_jsval(cx, value.handle_mut());
+                }
+                dict_return(cx, rval.handle_mut(), false, value.handle())
+            }
+            IteratorType::Values => {
+                unsafe {
+                    self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                }
+                dict_return(cx, rval.handle_mut(), false, value.handle())
+            }
+            IteratorType::Entries => {
+                rooted!(in(cx) let mut key = UndefinedValue());
+                unsafe {
+                    self.iterable.get_key_at_index(index).to_jsval(cx, key.handle_mut());
+                    self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                }
+                key_and_value_return(cx, rval.handle_mut(), key.handle(), value.handle())
+            }
+        };
+        self.index.set(index + 1);
+        result.map(|_| rval.handle().get())
+    }
+}
+
+fn dict_return(cx: *mut JSContext,
+               result: MutableHandleObject,
+               done: bool,
+               value: HandleValue) -> Fallible<()> {
+    let mut dict = unsafe { IterableKeyOrValueResult::empty(cx) };
+    dict.done = done;
+    dict.value = value.get();
+    rooted!(in(cx) let mut dict_value = UndefinedValue());
+    unsafe {
+        dict.to_jsval(cx, dict_value.handle_mut());
+    }
+    result.set(dict_value.to_object());
+    Ok(())
+}
+
+fn key_and_value_return(cx: *mut JSContext,
+                        result: MutableHandleObject,
+                        key: HandleValue,
+                        value: HandleValue) -> Fallible<()> {
+    let mut dict = unsafe { IterableKeyAndValueResult::empty(cx) };
+    dict.done = false;
+    dict.value = Some(vec![key.get(), value.get()]);
+    rooted!(in(cx) let mut dict_value = UndefinedValue());
+    unsafe {
+        dict.to_jsval(cx, dict_value.handle_mut());
+    }
+    result.set(dict_value.to_object());
+    Ok(())
+}