/* 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);
