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-rw-r--r--servo/components/style/gecko_bindings/sugar/refptr.rs289
1 files changed, 289 insertions, 0 deletions
diff --git a/servo/components/style/gecko_bindings/sugar/refptr.rs b/servo/components/style/gecko_bindings/sugar/refptr.rs
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+++ b/servo/components/style/gecko_bindings/sugar/refptr.rs
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+/* 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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-01 18:59:08 +0000