auto merge of #3979 : Ms2ger/servo/as_unsafe_cell, r=jdm

9 files changed, 33 insertions, 102 deletions

diff --git a/components/layout/wrapper.rs b/components/layout/wrapper.rs
index 4f5e0e46eea..4f774041979 100644
--- a/components/layout/wrapper.rs
+++ b/components/layout/wrapper.rs
@@ -37,7 +37,6 @@ use util::{LayoutDataAccess, LayoutDataFlags, LayoutDataWrapper, OpaqueNodeMetho
 use util::{PrivateLayoutData};
 
 use gfx::display_list::OpaqueNode;
-use script::dom::bindings::cell::{Ref, RefMut};
 use script::dom::bindings::codegen::InheritTypes::{ElementCast, HTMLIFrameElementCast};
 use script::dom::bindings::codegen::InheritTypes::{HTMLImageElementCast, HTMLInputElementCast};
 use script::dom::bindings::codegen::InheritTypes::{TextCast};
@@ -62,6 +61,8 @@ use style::{PropertyDeclarationBlock, SpecificNamespace, TElement, TElementAttri
 use url::Url;
 use string_cache::{Atom, Namespace};
 
+use std::cell::{Ref, RefMut};
+
 /// Allows some convenience methods on generic layout nodes.
 pub trait TLayoutNode {
     /// Creates a new layout node with the same lifetime as this layout node.
diff --git a/components/script/dom/attr.rs b/components/script/dom/attr.rs
index 324d17d6e14..95e05f8e79d 100644
--- a/components/script/dom/attr.rs
+++ b/components/script/dom/attr.rs
@@ -2,7 +2,7 @@
  * 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/. */
 
-use dom::bindings::cell::{DOMRefCell, Ref};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::AttrBinding;
 use dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
 use dom::bindings::codegen::InheritTypes::NodeCast;
@@ -16,9 +16,12 @@ use dom::virtualmethods::vtable_for;
 
 use devtools_traits::AttrInfo;
 use servo_util::str::{DOMString, split_html_space_chars};
-use std::mem;
+
 use string_cache::{Atom, Namespace};
 
+use std::cell::Ref;
+use std::mem;
+
 pub enum AttrSettingType {
     FirstSetAttr,
     ReplacedAttr,
diff --git a/components/script/dom/bindings/cell.rs b/components/script/dom/bindings/cell.rs
index 44acbef710e..76219b799c8 100644
--- a/components/script/dom/bindings/cell.rs
+++ b/components/script/dom/bindings/cell.rs
@@ -8,18 +8,14 @@ use js::jsapi::{JSTracer};
 use servo_util::task_state;
 use servo_util::task_state::{SCRIPT, IN_GC};
 
-use std::cell::{Cell, UnsafeCell};
-use std::kinds::marker;
+use std::cell::{RefCell, Ref, RefMut};
 
 /// A mutable field in the DOM.
 ///
 /// This extends the API of `core::cell::RefCell` to allow unsafe access in
 /// certain situations, with dynamic checking in debug builds.
 pub struct DOMRefCell<T> {
-    value: UnsafeCell<T>,
-    borrow: Cell<BorrowFlag>,
-    nocopy: marker::NoCopy,
-    nosync: marker::NoSync,
+    value: RefCell<T>,
 }
 
 // Functionality specific to Servo's `DOMRefCell` type
@@ -31,7 +27,7 @@ impl<T> DOMRefCell<T> {
     /// For use in the layout task only.
     pub unsafe fn borrow_for_layout<'a>(&'a self) -> &'a T {
         debug_assert!(task_state::get().is_layout());
-        &*self.value.get()
+        &*self.value.as_unsafe_cell().get()
     }
 
     /// Borrow the contents for the purpose of GC tracing.
@@ -40,36 +36,24 @@ impl<T> DOMRefCell<T> {
     /// so you have to be careful in trace code!
     pub unsafe fn borrow_for_gc_trace<'a>(&'a self) -> &'a T {
         debug_assert!(task_state::get().contains(SCRIPT | IN_GC));
-        &*self.value.get()
+        &*self.value.as_unsafe_cell().get()
     }
 
     /// Is the cell mutably borrowed?
     ///
     /// For safety checks in debug builds only.
     pub fn is_mutably_borrowed(&self) -> bool {
-        self.borrow.get() == WRITING
+        self.value.try_borrow().is_some()
     }
 
     pub fn try_borrow<'a>(&'a self) -> Option<Ref<'a, T>> {
         debug_assert!(task_state::get().is_script());
-        match self.borrow.get() {
-            WRITING => None,
-            borrow => {
-                self.borrow.set(borrow + 1);
-                Some(Ref { _parent: self })
-            }
-        }
+        self.value.try_borrow()
     }
 
     pub fn try_borrow_mut<'a>(&'a self) -> Option<RefMut<'a, T>> {
         debug_assert!(task_state::get().is_script());
-        match self.borrow.get() {
-            UNUSED => {
-                self.borrow.set(WRITING);
-                Some(RefMut { _parent: self })
-            },
-            _ => None
-        }
+        self.value.try_borrow_mut()
     }
 }
 
@@ -81,28 +65,15 @@ impl<T: JSTraceable> JSTraceable for DOMRefCell<T> {
 
 // Functionality duplicated with `core::cell::RefCell`
 // ===================================================
-//
-// This can shrink once rust-lang/rust#18131 is fixed.
-
-// Values [1, MAX-1] represent the number of `Ref` active
-// (will not outgrow its range since `uint` is the size of the address space)
-type BorrowFlag = uint;
-const UNUSED: BorrowFlag = 0;
-const WRITING: BorrowFlag = -1;
-
 impl<T> DOMRefCell<T> {
     pub fn new(value: T) -> DOMRefCell<T> {
         DOMRefCell {
-            value: UnsafeCell::new(value),
-            borrow: Cell::new(UNUSED),
-            nocopy: marker::NoCopy,
-            nosync: marker::NoSync,
+            value: RefCell::new(value),
         }
     }
 
     pub fn unwrap(self) -> T {
-        debug_assert!(self.borrow.get() == UNUSED);
-        unsafe{self.value.unwrap()}
+        self.value.unwrap()
     }
 
     pub fn borrow<'a>(&'a self) -> Ref<'a, T> {
@@ -119,50 +90,3 @@ impl<T> DOMRefCell<T> {
         }
     }
 }
-
-pub struct Ref<'b, T:'b> {
-    _parent: &'b DOMRefCell<T>
-}
-
-#[unsafe_destructor]
-impl<'b, T> Drop for Ref<'b, T> {
-    fn drop(&mut self) {
-        let borrow = self._parent.borrow.get();
-        debug_assert!(borrow != WRITING && borrow != UNUSED);
-        self._parent.borrow.set(borrow - 1);
-    }
-}
-
-impl<'b, T> Deref<T> for Ref<'b, T> {
-    #[inline]
-    fn deref<'a>(&'a self) -> &'a T {
-        unsafe { &*self._parent.value.get() }
-    }
-}
-
-pub struct RefMut<'b, T:'b> {
-    _parent: &'b DOMRefCell<T>
-}
-
-#[unsafe_destructor]
-impl<'b, T> Drop for RefMut<'b, T> {
-    fn drop(&mut self) {
-        let borrow = self._parent.borrow.get();
-        debug_assert!(borrow == WRITING);
-        self._parent.borrow.set(UNUSED);
-    }
-}
-
-impl<'b, T> Deref<T> for RefMut<'b, T> {
-    #[inline]
-    fn deref<'a>(&'a self) -> &'a T {
-        unsafe { &*self._parent.value.get() }
-    }
-}
-
-impl<'b, T> DerefMut<T> for RefMut<'b, T> {
-    #[inline]
-    fn deref_mut<'a>(&'a mut self) -> &'a mut T {
-        unsafe { &mut *self._parent.value.get() }
-    }
-}
diff --git a/components/script/dom/bindings/utils.rs b/components/script/dom/bindings/utils.rs
index 3117fc10f45..ad85597fd07 100644
--- a/components/script/dom/bindings/utils.rs
+++ b/components/script/dom/bindings/utils.rs
@@ -469,13 +469,11 @@ impl Reflector {
         self.object.set(object);
     }
 
-    /// Return a pointer to the memory location at which the JS reflector object is stored.
-    /// Used by Temporary values to root the reflector, as required by the JSAPI rooting
-    /// APIs.
-    pub fn rootable(&self) -> *mut *mut JSObject {
-        &self.object as *const Cell<*mut JSObject>
-                     as *mut Cell<*mut JSObject>
-                     as *mut *mut JSObject
+    /// Return a pointer to the memory location at which the JS reflector
+    /// object is stored. Used by Temporary values to root the reflector, as
+    /// required by the JSAPI rooting APIs.
+    pub unsafe fn rootable(&self) -> *mut *mut JSObject {
+        self.object.as_unsafe_cell().get()
     }
 
     /// Create an uninitialized `Reflector`.
diff --git a/components/script/dom/characterdata.rs b/components/script/dom/characterdata.rs
index a5eec3d8dc1..f1331ceacd4 100644
--- a/components/script/dom/characterdata.rs
+++ b/components/script/dom/characterdata.rs
@@ -4,7 +4,7 @@
 
 //! DOM bindings for `CharacterData`.
 
-use dom::bindings::cell::{DOMRefCell, Ref};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::CharacterDataBinding::CharacterDataMethods;
 use dom::bindings::codegen::InheritTypes::{CharacterDataDerived, NodeCast};
 use dom::bindings::error::{Fallible, ErrorResult, IndexSize};
@@ -13,8 +13,11 @@ use dom::bindings::utils::{Reflectable, Reflector};
 use dom::document::Document;
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::node::{CommentNodeTypeId, Node, NodeTypeId, TextNodeTypeId, ProcessingInstructionNodeTypeId, NodeHelpers};
+
 use servo_util::str::DOMString;
 
+use std::cell::Ref;
+
 #[dom_struct]
 pub struct CharacterData {
     node: Node,
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index b5a39073dad..2b8632fd7c1 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::attr::AttrHelpers;
-use dom::bindings::cell::{DOMRefCell, Ref};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::DocumentBinding;
 use dom::bindings::codegen::Bindings::DocumentBinding::{DocumentMethods, DocumentReadyState};
 use dom::bindings::codegen::Bindings::DocumentBinding::DocumentReadyStateValues;
@@ -65,7 +65,7 @@ use url::Url;
 use std::collections::HashMap;
 use std::collections::hash_map::{Vacant, Occupied};
 use std::ascii::AsciiExt;
-use std::cell::Cell;
+use std::cell::{Cell, Ref};
 use std::default::Default;
 use time;
 
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 87d3f889544..a5bac9110f2 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -7,7 +7,7 @@
 use dom::attr::{Attr, ReplacedAttr, FirstSetAttr, AttrHelpers, AttrHelpersForLayout};
 use dom::attr::{AttrValue, StringAttrValue, UIntAttrValue, AtomAttrValue};
 use dom::namednodemap::NamedNodeMap;
-use dom::bindings::cell::{DOMRefCell, Ref, RefMut};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
 use dom::bindings::codegen::Bindings::ElementBinding;
 use dom::bindings::codegen::Bindings::ElementBinding::ElementMethods;
@@ -41,6 +41,7 @@ use servo_util::namespace;
 use servo_util::str::{DOMString, LengthOrPercentageOrAuto};
 
 use std::ascii::AsciiExt;
+use std::cell::{Ref, RefMut};
 use std::default::Default;
 use std::mem;
 use string_cache::{Atom, Namespace, QualName};
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index a3664207b85..046029da9e6 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -2,7 +2,7 @@
  * 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/. */
 
-use dom::bindings::cell::{DOMRefCell, Ref, RefMut};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::{OnErrorEventHandlerNonNull, EventHandlerNonNull};
 use dom::bindings::codegen::Bindings::WindowBinding;
 use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
@@ -40,6 +40,7 @@ use url::{Url, UrlParser};
 
 use libc;
 use serialize::base64::{FromBase64, ToBase64, STANDARD};
+use std::cell::{Ref, RefMut};
 use std::default::Default;
 use std::rc::Rc;
 use time;
diff --git a/components/script/page.rs b/components/script/page.rs
index 23e0f0152dd..d0c8c3e0bcf 100644
--- a/components/script/page.rs
+++ b/components/script/page.rs
@@ -2,7 +2,7 @@
  * 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/. */
 
-use dom::bindings::cell::{DOMRefCell, Ref, RefMut};
+use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
 use dom::bindings::codegen::InheritTypes::NodeCast;
 use dom::bindings::js::{JS, JSRef, Temporary, OptionalRootable};
@@ -30,7 +30,7 @@ use servo_util::geometry::{Au, MAX_RECT};
 use servo_util::geometry;
 use servo_util::str::DOMString;
 use servo_util::smallvec::{SmallVec1, SmallVec};
-use std::cell::Cell;
+use std::cell::{Cell, Ref, RefMut};
 use std::comm::{channel, Receiver, Empty, Disconnected};
 use std::mem::replace;
 use std::num::abs;