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use std::cell::{Cell, UnsafeCell};
use std::ops::{Deref, DerefMut, Drop};
use std::{mem, ptr};
use js::glue::JS_GetReservedSlot;
use js::jsapi::{JSTracer, JS_SetReservedSlot};
use js::jsval::{PrivateValue, UndefinedValue};
use libc::c_void;
use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
use crate::dom::bindings::cell::DomRefCell;
use crate::dom::bindings::reflector::DomObject;
use crate::dom::bindings::root::DomRoot;
use crate::dom::bindings::trace::JSTraceable;
pub const DOM_WEAK_SLOT: u32 = 1;
#[allow(crown::unrooted_must_root)]
#[crown::unrooted_must_root_lint::allow_unrooted_interior]
pub struct WeakRef<T: WeakReferenceable> {
ptr: ptr::NonNull<WeakBox<T>>,
}
#[crown::unrooted_must_root_lint::must_root]
pub struct WeakBox<T: WeakReferenceable> {
pub count: Cell<usize>,
pub value: Cell<Option<ptr::NonNull<T>>>,
}
pub trait WeakReferenceable: DomObject + Sized {
fn downgrade(&self) -> WeakRef<Self> {
unsafe {
let object = self.reflector().get_jsobject().get();
let mut slot = UndefinedValue();
JS_GetReservedSlot(object, DOM_WEAK_SLOT, &mut slot);
let mut ptr = slot.to_private() as *mut WeakBox<Self>;
if ptr.is_null() {
trace!("Creating new WeakBox holder for {:p}.", self);
ptr = Box::into_raw(Box::new(WeakBox {
count: Cell::new(1),
value: Cell::new(Some(ptr::NonNull::from(self))),
}));
let val = PrivateValue(ptr as *const c_void);
JS_SetReservedSlot(object, DOM_WEAK_SLOT, &val);
}
let box_ = &*ptr;
assert!(box_.value.get().is_some());
let new_count = box_.count.get() + 1;
trace!(
"Incrementing WeakBox refcount for {:p} to {}.",
self,
new_count
);
box_.count.set(new_count);
WeakRef {
ptr: ptr::NonNull::new_unchecked(ptr),
}
}
}
}
impl<T: WeakReferenceable> WeakRef<T> {
pub fn new(value: &T) -> Self {
value.downgrade()
}
pub fn root(&self) -> Option<DomRoot<T>> {
unsafe { &*self.ptr.as_ptr() }
.value
.get()
.map(|ptr| unsafe { DomRoot::from_ref(&*ptr.as_ptr()) })
}
pub fn is_alive(&self) -> bool {
unsafe { &*self.ptr.as_ptr() }.value.get().is_some()
}
}
impl<T: WeakReferenceable> Clone for WeakRef<T> {
fn clone(&self) -> WeakRef<T> {
unsafe {
let box_ = &*self.ptr.as_ptr();
let new_count = box_.count.get() + 1;
box_.count.set(new_count);
WeakRef { ptr: self.ptr }
}
}
}
impl<T: WeakReferenceable> MallocSizeOf for WeakRef<T> {
fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
0
}
}
impl<T: WeakReferenceable> PartialEq for WeakRef<T> {
fn eq(&self, other: &Self) -> bool {
unsafe {
(*self.ptr.as_ptr()).value.get().map(ptr::NonNull::as_ptr) ==
(*other.ptr.as_ptr()).value.get().map(ptr::NonNull::as_ptr)
}
}
}
impl<T: WeakReferenceable> PartialEq<T> for WeakRef<T> {
fn eq(&self, other: &T) -> bool {
unsafe {
match self.ptr.as_ref().value.get() {
Some(ptr) => ptr::eq(ptr.as_ptr(), other),
None => false,
}
}
}
}
unsafe impl<T: WeakReferenceable> JSTraceable for WeakRef<T> {
unsafe fn trace(&self, _: *mut JSTracer) {
}
}
impl<T: WeakReferenceable> Drop for WeakRef<T> {
fn drop(&mut self) {
unsafe {
let (count, value) = {
let weak_box = &*self.ptr.as_ptr();
assert!(weak_box.count.get() > 0);
let count = weak_box.count.get() - 1;
weak_box.count.set(count);
(count, weak_box.value.get())
};
if count == 0 {
assert!(value.is_none());
mem::drop(Box::from_raw(self.ptr.as_ptr()));
}
}
}
}
pub struct MutableWeakRef<T: WeakReferenceable> {
cell: UnsafeCell<Option<WeakRef<T>>>,
}
impl<T: WeakReferenceable> MutableWeakRef<T> {
pub fn new(value: Option<&T>) -> MutableWeakRef<T> {
MutableWeakRef {
cell: UnsafeCell::new(value.map(WeakRef::new)),
}
}
pub fn set(&self, value: Option<&T>) {
unsafe {
*self.cell.get() = value.map(WeakRef::new);
}
}
pub fn root(&self) -> Option<DomRoot<T>> {
unsafe { &*self.cell.get() }
.as_ref()
.and_then(WeakRef::root)
}
}
impl<T: WeakReferenceable> MallocSizeOf for MutableWeakRef<T> {
fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
0
}
}
unsafe impl<T: WeakReferenceable> JSTraceable for MutableWeakRef<T> {
unsafe fn trace(&self, _: *mut JSTracer) {
let ptr = self.cell.get();
let should_drop = match *ptr {
Some(ref value) => !value.is_alive(),
None => false,
};
if should_drop {
mem::drop((*ptr).take().unwrap());
}
}
}
#[crown::unrooted_must_root_lint::allow_unrooted_interior]
#[derive(MallocSizeOf)]
pub struct WeakRefVec<T: WeakReferenceable> {
vec: Vec<WeakRef<T>>,
}
impl<T: WeakReferenceable> WeakRefVec<T> {
pub fn new() -> Self {
WeakRefVec { vec: vec![] }
}
pub fn update<F: FnMut(WeakRefEntry<T>)>(&mut self, mut f: F) {
let mut i = 0;
while i < self.vec.len() {
if self.vec[i].is_alive() {
f(WeakRefEntry {
vec: self,
index: &mut i,
});
} else {
self.vec.swap_remove(i);
}
}
}
pub fn retain_alive(&mut self) {
self.update(|_| ());
}
}
impl<T: WeakReferenceable> Deref for WeakRefVec<T> {
type Target = Vec<WeakRef<T>>;
fn deref(&self) -> &Vec<WeakRef<T>> {
&self.vec
}
}
impl<T: WeakReferenceable> DerefMut for WeakRefVec<T> {
fn deref_mut(&mut self) -> &mut Vec<WeakRef<T>> {
&mut self.vec
}
}
#[crown::unrooted_must_root_lint::allow_unrooted_interior]
pub struct WeakRefEntry<'a, T: WeakReferenceable> {
vec: &'a mut WeakRefVec<T>,
index: &'a mut usize,
}
impl<'a, T: WeakReferenceable + 'a> WeakRefEntry<'a, T> {
pub fn remove(self) -> WeakRef<T> {
let ref_ = self.vec.swap_remove(*self.index);
mem::forget(self);
ref_
}
}
impl<'a, T: WeakReferenceable + 'a> Deref for WeakRefEntry<'a, T> {
type Target = WeakRef<T>;
fn deref(&self) -> &WeakRef<T> {
&self.vec[*self.index]
}
}
impl<'a, T: WeakReferenceable + 'a> Drop for WeakRefEntry<'a, T> {
fn drop(&mut self) {
*self.index += 1;
}
}
#[derive(MallocSizeOf)]
pub struct DOMTracker<T: WeakReferenceable> {
dom_objects: DomRefCell<WeakRefVec<T>>,
}
impl<T: WeakReferenceable> DOMTracker<T> {
pub fn new() -> Self {
Self {
dom_objects: DomRefCell::new(WeakRefVec::new()),
}
}
pub fn track(&self, dom_object: &T) {
self.dom_objects.borrow_mut().push(WeakRef::new(dom_object));
}
pub fn for_each<F: FnMut(DomRoot<T>)>(&self, mut f: F) {
self.dom_objects.borrow_mut().update(|weak_ref| {
let root = weak_ref.root().unwrap();
f(root);
});
}
}
#[allow(unsafe_code)]
unsafe impl<T: WeakReferenceable> JSTraceable for DOMTracker<T> {
unsafe fn trace(&self, _: *mut JSTracer) {
self.dom_objects.borrow_mut().retain_alive();
}
}