Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 711 insertions, 0 deletions

diff --git a/servo/components/style/gecko_bindings/mod.rs b/servo/components/style/gecko_bindings/mod.rs
new file mode 100644
index 0000000000..f0b0adc7ec
--- /dev/null
+++ b/servo/components/style/gecko_bindings/mod.rs
@@ -0,0 +1,28 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Gecko's C++ bindings, along with some rust helpers to ease its use.
+
+// FIXME: We allow `improper_ctypes` (for now), because the lint doesn't allow
+// foreign structs to have `PhantomData`. We should remove this once the lint
+// ignores this case.
+
+#[allow(
+    dead_code,
+    improper_ctypes,
+    non_camel_case_types,
+    non_snake_case,
+    non_upper_case_globals,
+    missing_docs
+)]
+// TODO: Remove this when updating bindgen, see
+// https://github.com/rust-lang/rust-bindgen/issues/1651
+#[cfg_attr(test, allow(deref_nullptr))]
+pub mod structs {
+    include!(concat!(env!("OUT_DIR"), "/gecko/structs.rs"));
+}
+
+pub use self::structs as bindings;
+
+pub mod sugar;
diff --git a/servo/components/style/gecko_bindings/sugar/mod.rs b/servo/components/style/gecko_bindings/sugar/mod.rs
new file mode 100644
index 0000000000..00faf63ba6
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/mod.rs
@@ -0,0 +1,13 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Rust sugar and convenience methods for Gecko types.
+
+mod ns_com_ptr;
+mod ns_compatibility;
+mod ns_style_auto_array;
+mod ns_t_array;
+pub mod origin_flags;
+pub mod ownership;
+pub mod refptr;
diff --git a/servo/components/style/gecko_bindings/sugar/ns_com_ptr.rs b/servo/components/style/gecko_bindings/sugar/ns_com_ptr.rs
new file mode 100644
index 0000000000..1c54541bd8
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ns_com_ptr.rs
@@ -0,0 +1,15 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Little helpers for `nsCOMPtr`.
+
+use crate::gecko_bindings::structs::nsCOMPtr;
+
+impl<T> nsCOMPtr<T> {
+    /// Get this pointer as a raw pointer.
+    #[inline]
+    pub fn raw(&self) -> *mut T {
+        self.mRawPtr
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/ns_compatibility.rs b/servo/components/style/gecko_bindings/sugar/ns_compatibility.rs
new file mode 100644
index 0000000000..f4b81e9f79
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ns_compatibility.rs
@@ -0,0 +1,19 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Little helper for `nsCompatibility`.
+
+use crate::context::QuirksMode;
+use crate::gecko_bindings::structs::nsCompatibility;
+
+impl From<nsCompatibility> for QuirksMode {
+    #[inline]
+    fn from(mode: nsCompatibility) -> QuirksMode {
+        match mode {
+            nsCompatibility::eCompatibility_FullStandards => QuirksMode::NoQuirks,
+            nsCompatibility::eCompatibility_AlmostStandards => QuirksMode::LimitedQuirks,
+            nsCompatibility::eCompatibility_NavQuirks => QuirksMode::Quirks,
+        }
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs b/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
new file mode 100644
index 0000000000..b5772a6c77
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
@@ -0,0 +1,111 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Rust helpers for Gecko's `nsStyleAutoArray`.
+
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleAnimationArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleScrollTimelineArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleTransitionArrayLength;
+use crate::gecko_bindings::bindings::Gecko_EnsureStyleViewTimelineArrayLength;
+use crate::gecko_bindings::structs::nsStyleAutoArray;
+use crate::gecko_bindings::structs::{StyleAnimation, StyleTransition};
+use crate::gecko_bindings::structs::{StyleScrollTimeline, StyleViewTimeline};
+use std::iter::{once, Chain, IntoIterator, Once};
+use std::ops::{Index, IndexMut};
+use std::slice::{Iter, IterMut};
+
+impl<T> Index<usize> for nsStyleAutoArray<T> {
+    type Output = T;
+    fn index(&self, index: usize) -> &T {
+        match index {
+            0 => &self.mFirstElement,
+            _ => &self.mOtherElements[index - 1],
+        }
+    }
+}
+
+impl<T> IndexMut<usize> for nsStyleAutoArray<T> {
+    fn index_mut(&mut self, index: usize) -> &mut T {
+        match index {
+            0 => &mut self.mFirstElement,
+            _ => &mut self.mOtherElements[index - 1],
+        }
+    }
+}
+
+impl<T> nsStyleAutoArray<T> {
+    /// Mutably iterate over the array elements.
+    pub fn iter_mut(&mut self) -> Chain<Once<&mut T>, IterMut<T>> {
+        once(&mut self.mFirstElement).chain(self.mOtherElements.iter_mut())
+    }
+
+    /// Iterate over the array elements.
+    pub fn iter(&self) -> Chain<Once<&T>, Iter<T>> {
+        once(&self.mFirstElement).chain(self.mOtherElements.iter())
+    }
+
+    /// Returns the length of the array.
+    ///
+    /// Note that often structs containing autoarrays will have additional
+    /// member fields that contain the length, which must be kept in sync.
+    pub fn len(&self) -> usize {
+        1 + self.mOtherElements.len()
+    }
+}
+
+impl nsStyleAutoArray<StyleAnimation> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleAnimationArrayLength(
+                self as *mut nsStyleAutoArray<StyleAnimation> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleTransition> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleTransitionArrayLength(
+                self as *mut nsStyleAutoArray<StyleTransition> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleViewTimeline> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleViewTimelineArrayLength(
+                self as *mut nsStyleAutoArray<StyleViewTimeline> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl nsStyleAutoArray<StyleScrollTimeline> {
+    /// Ensures that the array has length at least the given length.
+    pub fn ensure_len(&mut self, len: usize) {
+        unsafe {
+            Gecko_EnsureStyleScrollTimelineArrayLength(
+                self as *mut nsStyleAutoArray<StyleScrollTimeline> as *mut _,
+                len,
+            );
+        }
+    }
+}
+
+impl<'a, T> IntoIterator for &'a mut nsStyleAutoArray<T> {
+    type Item = &'a mut T;
+    type IntoIter = Chain<Once<&'a mut T>, IterMut<'a, T>>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter_mut()
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/ns_t_array.rs b/servo/components/style/gecko_bindings/sugar/ns_t_array.rs
new file mode 100644
index 0000000000..d10ed420dd
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ns_t_array.rs
@@ -0,0 +1,144 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Rust helpers for Gecko's nsTArray.
+
+use crate::gecko_bindings::bindings;
+use crate::gecko_bindings::structs::{nsTArray, nsTArrayHeader, CopyableTArray};
+use std::mem;
+use std::ops::{Deref, DerefMut};
+use std::slice;
+
+impl<T> Deref for nsTArray<T> {
+    type Target = [T];
+
+    #[inline]
+    fn deref<'a>(&'a self) -> &'a [T] {
+        unsafe { slice::from_raw_parts(self.slice_begin(), self.header().mLength as usize) }
+    }
+}
+
+impl<T> DerefMut for nsTArray<T> {
+    fn deref_mut<'a>(&'a mut self) -> &'a mut [T] {
+        unsafe { slice::from_raw_parts_mut(self.slice_begin(), self.header().mLength as usize) }
+    }
+}
+
+impl<T> nsTArray<T> {
+    #[inline]
+    fn header<'a>(&'a self) -> &'a nsTArrayHeader {
+        debug_assert!(!self.mBuffer.is_null());
+        unsafe { mem::transmute(self.mBuffer) }
+    }
+
+    // unsafe, since header may be in shared static or something
+    unsafe fn header_mut<'a>(&'a mut self) -> &'a mut nsTArrayHeader {
+        debug_assert!(!self.mBuffer.is_null());
+
+        mem::transmute(self.mBuffer)
+    }
+
+    #[inline]
+    unsafe fn slice_begin(&self) -> *mut T {
+        debug_assert!(!self.mBuffer.is_null());
+        (self.mBuffer as *const nsTArrayHeader).offset(1) as *mut _
+    }
+
+    /// Ensures the array has enough capacity at least to hold `cap` elements.
+    ///
+    /// NOTE: This doesn't call the constructor on the values!
+    pub fn ensure_capacity(&mut self, cap: usize) {
+        if cap >= self.len() {
+            unsafe {
+                bindings::Gecko_EnsureTArrayCapacity(
+                    self as *mut nsTArray<T> as *mut _,
+                    cap,
+                    mem::size_of::<T>(),
+                )
+            }
+        }
+    }
+
+    /// Clears the array storage without calling the destructor on the values.
+    #[inline]
+    pub unsafe fn clear(&mut self) {
+        if self.len() != 0 {
+            bindings::Gecko_ClearPODTArray(
+                self as *mut nsTArray<T> as *mut _,
+                mem::size_of::<T>(),
+                mem::align_of::<T>(),
+            );
+        }
+    }
+
+    /// Clears a POD array. This is safe since copy types are memcopyable.
+    #[inline]
+    pub fn clear_pod(&mut self)
+    where
+        T: Copy,
+    {
+        unsafe { self.clear() }
+    }
+
+    /// Resize and set the length of the array to `len`.
+    ///
+    /// unsafe because this may leave the array with uninitialized elements.
+    ///
+    /// This will not call constructors.  If you need that, either manually add
+    /// bindings or run the typed `EnsureCapacity` call on the gecko side.
+    pub unsafe fn set_len(&mut self, len: u32) {
+        // this can leak
+        debug_assert!(len >= self.len() as u32);
+        if self.len() == len as usize {
+            return;
+        }
+        self.ensure_capacity(len as usize);
+        self.header_mut().mLength = len;
+    }
+
+    /// Resizes an array containing only POD elements
+    ///
+    /// unsafe because this may leave the array with uninitialized elements.
+    ///
+    /// This will not leak since it only works on POD types (and thus doesn't assert)
+    pub unsafe fn set_len_pod(&mut self, len: u32)
+    where
+        T: Copy,
+    {
+        if self.len() == len as usize {
+            return;
+        }
+        self.ensure_capacity(len as usize);
+        let header = self.header_mut();
+        header.mLength = len;
+    }
+
+    /// Collects the given iterator into this array.
+    ///
+    /// Not unsafe because we won't leave uninitialized elements in the array.
+    pub fn assign_from_iter_pod<I>(&mut self, iter: I)
+    where
+        T: Copy,
+        I: ExactSizeIterator + Iterator<Item = T>,
+    {
+        debug_assert!(iter.len() <= 0xFFFFFFFF);
+        unsafe {
+            self.set_len_pod(iter.len() as u32);
+        }
+        self.iter_mut().zip(iter).for_each(|(r, v)| *r = v);
+    }
+}
+
+impl<T> Deref for CopyableTArray<T> {
+    type Target = nsTArray<T>;
+    fn deref(&self) -> &Self::Target {
+        &self._base
+    }
+}
+
+impl<T> DerefMut for CopyableTArray<T> {
+    fn deref_mut(&mut self) -> &mut nsTArray<T> {
+        &mut self._base
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/origin_flags.rs b/servo/components/style/gecko_bindings/sugar/origin_flags.rs
new file mode 100644
index 0000000000..b27060405a
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/origin_flags.rs
@@ -0,0 +1,31 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Helper to iterate over `OriginFlags` bits.
+
+use crate::gecko_bindings::structs::OriginFlags;
+use crate::stylesheets::OriginSet;
+
+/// Checks that the values for OriginFlags are the ones we expect.
+pub fn assert_flags_match() {
+    use crate::stylesheets::origin::*;
+    debug_assert_eq!(
+        OriginFlags::UserAgent.0,
+        OriginSet::ORIGIN_USER_AGENT.bits()
+    );
+    debug_assert_eq!(OriginFlags::Author.0, OriginSet::ORIGIN_AUTHOR.bits());
+    debug_assert_eq!(OriginFlags::User.0, OriginSet::ORIGIN_USER.bits());
+}
+
+impl From<OriginFlags> for OriginSet {
+    fn from(flags: OriginFlags) -> Self {
+        Self::from_bits_retain(flags.0)
+    }
+}
+
+impl From<OriginSet> for OriginFlags {
+    fn from(set: OriginSet) -> Self {
+        OriginFlags(set.bits())
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/ownership.rs b/servo/components/style/gecko_bindings/sugar/ownership.rs
new file mode 100644
index 0000000000..31b512cf1e
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/ownership.rs
@@ -0,0 +1,61 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Helpers for different FFI pointer kinds that Gecko's FFI layer uses.
+
+use crate::gecko_bindings::structs::root::mozilla::detail::CopyablePtr;
+use servo_arc::Arc;
+use std::marker::PhantomData;
+use std::ops::{Deref, DerefMut};
+use std::ptr;
+
+/// Gecko-FFI-safe Arc (T is an ArcInner).
+///
+/// This can be null.
+///
+/// Leaks on drop. Please don't drop this.
+#[repr(C)]
+pub struct Strong<GeckoType> {
+    ptr: *const GeckoType,
+    _marker: PhantomData<GeckoType>,
+}
+
+impl<T> From<Arc<T>> for Strong<T> {
+    fn from(arc: Arc<T>) -> Self {
+        Self {
+            ptr: Arc::into_raw(arc),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<GeckoType> Strong<GeckoType> {
+    #[inline]
+    /// Returns whether this reference is null.
+    pub fn is_null(&self) -> bool {
+        self.ptr.is_null()
+    }
+
+    #[inline]
+    /// Returns a null pointer
+    pub fn null() -> Self {
+        Self {
+            ptr: ptr::null(),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T> Deref for CopyablePtr<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.mPtr
+    }
+}
+
+impl<T> DerefMut for CopyablePtr<T> {
+    fn deref_mut<'a>(&'a mut self) -> &'a mut T {
+        &mut self.mPtr
+    }
+}
diff --git a/servo/components/style/gecko_bindings/sugar/refptr.rs b/servo/components/style/gecko_bindings/sugar/refptr.rs
new file mode 100644
index 0000000000..c4a0479a07
--- /dev/null
+++ b/servo/components/style/gecko_bindings/sugar/refptr.rs
@@ -0,0 +1,289 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! A rust helper to ease the use of Gecko's refcounted types.
+
+use crate::gecko_bindings::{bindings, structs};
+use crate::Atom;
+use servo_arc::Arc;
+use std::fmt::Write;
+use std::marker::PhantomData;
+use std::ops::Deref;
+use std::{fmt, mem, ptr};
+
+/// Trait for all objects that have Addref() and Release
+/// methods and can be placed inside RefPtr<T>
+pub unsafe trait RefCounted {
+    /// Bump the reference count.
+    fn addref(&self);
+    /// Decrease the reference count.
+    unsafe fn release(&self);
+}
+
+/// Trait for types which can be shared across threads in RefPtr.
+pub unsafe trait ThreadSafeRefCounted: RefCounted {}
+
+/// A custom RefPtr implementation to take into account Drop semantics and
+/// a bit less-painful memory management.
+pub struct RefPtr<T: RefCounted> {
+    ptr: *mut T,
+    _marker: PhantomData<T>,
+}
+
+impl<T: RefCounted> fmt::Debug for RefPtr<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("RefPtr { ")?;
+        self.ptr.fmt(f)?;
+        f.write_char('}')
+    }
+}
+
+impl<T: RefCounted> RefPtr<T> {
+    /// Create a new RefPtr from an already addrefed pointer obtained from FFI.
+    ///
+    /// The pointer must be valid, non-null and have been addrefed.
+    pub unsafe fn from_addrefed(ptr: *mut T) -> Self {
+        debug_assert!(!ptr.is_null());
+        RefPtr {
+            ptr,
+            _marker: PhantomData,
+        }
+    }
+
+    /// Returns whether the current pointer is null.
+    pub fn is_null(&self) -> bool {
+        self.ptr.is_null()
+    }
+
+    /// Returns a null pointer.
+    pub fn null() -> Self {
+        Self {
+            ptr: ptr::null_mut(),
+            _marker: PhantomData,
+        }
+    }
+
+    /// Create a new RefPtr from a pointer obtained from FFI.
+    ///
+    /// This method calls addref() internally
+    pub unsafe fn new(ptr: *mut T) -> Self {
+        let ret = RefPtr {
+            ptr,
+            _marker: PhantomData,
+        };
+        ret.addref();
+        ret
+    }
+
+    /// Produces an FFI-compatible RefPtr that can be stored in style structs.
+    ///
+    /// structs::RefPtr does not have a destructor, so this may leak
+    pub fn forget(self) -> structs::RefPtr<T> {
+        let ret = structs::RefPtr {
+            mRawPtr: self.ptr,
+            _phantom_0: PhantomData,
+        };
+        mem::forget(self);
+        ret
+    }
+
+    /// Returns the raw inner pointer to be fed back into FFI.
+    pub fn get(&self) -> *mut T {
+        self.ptr
+    }
+
+    /// Addref the inner data, obviously leaky on its own.
+    pub fn addref(&self) {
+        if !self.ptr.is_null() {
+            unsafe {
+                (*self.ptr).addref();
+            }
+        }
+    }
+
+    /// Release the inner data.
+    ///
+    /// Call only when the data actually needs releasing.
+    pub unsafe fn release(&self) {
+        if !self.ptr.is_null() {
+            (*self.ptr).release();
+        }
+    }
+}
+
+impl<T: RefCounted> Deref for RefPtr<T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        debug_assert!(!self.ptr.is_null());
+        unsafe { &*self.ptr }
+    }
+}
+
+impl<T: RefCounted> structs::RefPtr<T> {
+    /// Produces a Rust-side RefPtr from an FFI RefPtr, bumping the refcount.
+    ///
+    /// Must be called on a valid, non-null structs::RefPtr<T>.
+    pub unsafe fn to_safe(&self) -> RefPtr<T> {
+        let r = RefPtr {
+            ptr: self.mRawPtr,
+            _marker: PhantomData,
+        };
+        r.addref();
+        r
+    }
+    /// Produces a Rust-side RefPtr, consuming the existing one (and not bumping
+    /// the refcount).
+    pub unsafe fn into_safe(self) -> RefPtr<T> {
+        debug_assert!(!self.mRawPtr.is_null());
+        RefPtr {
+            ptr: self.mRawPtr,
+            _marker: PhantomData,
+        }
+    }
+
+    /// Replace a structs::RefPtr<T> with a different one, appropriately
+    /// addref/releasing.
+    ///
+    /// Both `self` and `other` must be valid, but can be null.
+    ///
+    /// Safe when called on an aliased pointer because the refcount in that case
+    /// needs to be at least two.
+    pub unsafe fn set(&mut self, other: &Self) {
+        self.clear();
+        if !other.mRawPtr.is_null() {
+            *self = other.to_safe().forget();
+        }
+    }
+
+    /// Clear an instance of the structs::RefPtr<T>, by releasing
+    /// it and setting its contents to null.
+    ///
+    /// `self` must be valid, but can be null.
+    pub unsafe fn clear(&mut self) {
+        if !self.mRawPtr.is_null() {
+            (*self.mRawPtr).release();
+            self.mRawPtr = ptr::null_mut();
+        }
+    }
+
+    /// Replace a `structs::RefPtr<T>` with a `RefPtr<T>`,
+    /// consuming the `RefPtr<T>`, and releasing the old
+    /// value in `self` if necessary.
+    ///
+    /// `self` must be valid, possibly null.
+    pub fn set_move(&mut self, other: RefPtr<T>) {
+        if !self.mRawPtr.is_null() {
+            unsafe {
+                (*self.mRawPtr).release();
+            }
+        }
+        *self = other.forget();
+    }
+}
+
+impl<T> structs::RefPtr<T> {
+    /// Returns a new, null refptr.
+    pub fn null() -> Self {
+        Self {
+            mRawPtr: ptr::null_mut(),
+            _phantom_0: PhantomData,
+        }
+    }
+
+    /// Create a new RefPtr from an arc.
+    pub fn from_arc(s: Arc<T>) -> Self {
+        Self {
+            mRawPtr: Arc::into_raw(s) as *mut _,
+            _phantom_0: PhantomData,
+        }
+    }
+
+    /// Sets the contents to an Arc<T>.
+    pub fn set_arc(&mut self, other: Arc<T>) {
+        unsafe {
+            if !self.mRawPtr.is_null() {
+                let _ = Arc::from_raw(self.mRawPtr);
+            }
+            self.mRawPtr = Arc::into_raw(other) as *mut _;
+        }
+    }
+}
+
+impl<T: RefCounted> Drop for RefPtr<T> {
+    fn drop(&mut self) {
+        unsafe { self.release() }
+    }
+}
+
+impl<T: RefCounted> Clone for RefPtr<T> {
+    fn clone(&self) -> Self {
+        self.addref();
+        RefPtr {
+            ptr: self.ptr,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T: RefCounted> PartialEq for RefPtr<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.ptr == other.ptr
+    }
+}
+
+unsafe impl<T: ThreadSafeRefCounted> Send for RefPtr<T> {}
+unsafe impl<T: ThreadSafeRefCounted> Sync for RefPtr<T> {}
+
+macro_rules! impl_refcount {
+    ($t:ty, $addref:path, $release:path) => {
+        unsafe impl RefCounted for $t {
+            #[inline]
+            fn addref(&self) {
+                unsafe { $addref(self as *const _ as *mut _) }
+            }
+
+            #[inline]
+            unsafe fn release(&self) {
+                $release(self as *const _ as *mut _)
+            }
+        }
+    };
+}
+
+// Companion of NS_DECL_THREADSAFE_FFI_REFCOUNTING.
+//
+// Gets you a free RefCounted impl implemented via FFI.
+macro_rules! impl_threadsafe_refcount {
+    ($t:ty, $addref:path, $release:path) => {
+        impl_refcount!($t, $addref, $release);
+        unsafe impl ThreadSafeRefCounted for $t {}
+    };
+}
+
+impl_threadsafe_refcount!(
+    structs::mozilla::URLExtraData,
+    bindings::Gecko_AddRefURLExtraDataArbitraryThread,
+    bindings::Gecko_ReleaseURLExtraDataArbitraryThread
+);
+impl_threadsafe_refcount!(
+    structs::nsIURI,
+    bindings::Gecko_AddRefnsIURIArbitraryThread,
+    bindings::Gecko_ReleasensIURIArbitraryThread
+);
+impl_threadsafe_refcount!(
+    structs::SheetLoadDataHolder,
+    bindings::Gecko_AddRefSheetLoadDataHolderArbitraryThread,
+    bindings::Gecko_ReleaseSheetLoadDataHolderArbitraryThread
+);
+
+#[inline]
+unsafe fn addref_atom(atom: *mut structs::nsAtom) {
+    mem::forget(Atom::from_raw(atom));
+}
+
+#[inline]
+unsafe fn release_atom(atom: *mut structs::nsAtom) {
+    let _ = Atom::from_addrefed(atom);
+}
+impl_threadsafe_refcount!(structs::nsAtom, addref_atom, release_atom);