script_bindings/
finalize.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! Generic finalizer implementations for DOM binding implementations.
6
7use std::any::type_name;
8use std::{mem, ptr};
9
10use js::glue::JS_GetReservedSlot;
11use js::jsapi::JSObject;
12use js::jsval::UndefinedValue;
13use js::rust::GCMethods;
14
15use crate::DomObject;
16use crate::codegen::PrototypeList::PROTO_OR_IFACE_LENGTH;
17use crate::utils::{ProtoOrIfaceArray, get_proto_or_iface_array};
18use crate::weakref::{DOM_WEAK_SLOT, WeakBox, WeakReferenceable};
19
20/// Drop the resources held by reserved slots of a global object
21unsafe fn do_finalize_global(obj: *mut JSObject) {
22    unsafe {
23        let protolist = get_proto_or_iface_array(obj);
24        let list = (*protolist).as_mut_ptr();
25        for idx in 0..PROTO_OR_IFACE_LENGTH as isize {
26            let entry = list.offset(idx);
27            let value = *entry;
28            <*mut JSObject>::post_barrier(entry, value, ptr::null_mut());
29        }
30        let _: Box<ProtoOrIfaceArray> = Box::from_raw(protolist);
31    }
32}
33
34/// # Safety
35/// `this` must point to a valid, non-null instance of T.
36pub(crate) unsafe fn finalize_common<T: DomObject>(this: *const T) {
37    if !this.is_null() {
38        // The pointer can be null if the object is the unforgeable holder of that interface.
39        let this = unsafe { Box::from_raw(this as *mut T) };
40        this.reflector().drop_memory(&*this);
41    }
42    debug!("{} finalize: {:p}", type_name::<T>(), this);
43}
44
45/// # Safety
46/// `obj` must point to a valid, non-null JS object.
47/// `this` must point to a valid, non-null instance of T.
48pub(crate) unsafe fn finalize_global<T: DomObject>(obj: *mut JSObject, this: *const T) {
49    unsafe {
50        do_finalize_global(obj);
51        finalize_common::<T>(this);
52    }
53}
54
55/// # Safety
56/// `obj` must point to a valid, non-null JS object.
57/// `this` must point to a valid, non-null instance of T.
58pub(crate) unsafe fn finalize_weak_referenceable<T: WeakReferenceable>(
59    obj: *mut JSObject,
60    this: *const T,
61) {
62    let mut slot = UndefinedValue();
63    unsafe { JS_GetReservedSlot(obj, DOM_WEAK_SLOT, &mut slot) };
64    let weak_box_ptr = slot.to_private() as *mut WeakBox<T>;
65    if !weak_box_ptr.is_null() {
66        let count = {
67            let weak_box = unsafe { &*weak_box_ptr };
68            assert!(weak_box.value.get().is_some());
69            assert!(weak_box.count.get() > 0);
70            weak_box.value.set(None);
71            let count = weak_box.count.get() - 1;
72            weak_box.count.set(count);
73            count
74        };
75        if count == 0 {
76            mem::drop(unsafe { Box::from_raw(weak_box_ptr) });
77        }
78    }
79    unsafe { finalize_common::<T>(this) };
80}
script_bindings/finalize.rs

script_bindings/
finalize.rs
