1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
/* 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 http://mozilla.org/MPL/2.0/. */
//! A shareable mutable container for the DOM.
use std::cell::{BorrowError, BorrowMutError, Ref, RefCell, RefMut};
use style::thread_state;
/// A mutable field in the DOM.
///
/// This extends the API of `core::cell::RefCell` to allow unsafe access in
/// certain situations, with dynamic checking in debug builds.
#[derive(Clone, PartialEq, Debug, HeapSizeOf)]
pub struct DOMRefCell<T> {
value: RefCell<T>,
}
// Functionality specific to Servo's `DOMRefCell` type
// ===================================================
impl<T> DOMRefCell<T> {
/// Return a reference to the contents.
///
/// For use in the layout thread only.
#[allow(unsafe_code)]
pub unsafe fn borrow_for_layout(&self) -> &T {
debug_assert!(thread_state::get().is_layout());
&*self.value.as_ptr()
}
/// Borrow the contents for the purpose of GC tracing.
///
/// This succeeds even if the object is mutably borrowed,
/// so you have to be careful in trace code!
#[allow(unsafe_code)]
pub unsafe fn borrow_for_gc_trace(&self) -> &T {
// FIXME: IN_GC isn't reliable enough - doesn't catch minor GCs
// https://github.com/servo/servo/issues/6389
// debug_assert!(thread_state::get().contains(SCRIPT | IN_GC));
&*self.value.as_ptr()
}
/// Borrow the contents for the purpose of script deallocation.
///
#[allow(unsafe_code)]
pub unsafe fn borrow_for_script_deallocation(&self) -> &mut T {
debug_assert!(thread_state::get().contains(thread_state::SCRIPT));
&mut *self.value.as_ptr()
}
/// Version of the above that we use during restyle while the script thread
/// is blocked.
pub fn borrow_mut_for_layout(&self) -> RefMut<T> {
debug_assert!(thread_state::get().is_layout());
self.value.borrow_mut()
}
}
// Functionality duplicated with `core::cell::RefCell`
// ===================================================
impl<T> DOMRefCell<T> {
/// Create a new `DOMRefCell` containing `value`.
pub fn new(value: T) -> DOMRefCell<T> {
DOMRefCell {
value: RefCell::new(value),
}
}
/// Immutably borrows the wrapped value.
///
/// The borrow lasts until the returned `Ref` exits scope. Multiple
/// immutable borrows can be taken out at the same time.
///
/// # Panics
///
/// Panics if this is called off the script thread.
///
/// Panics if the value is currently mutably borrowed.
pub fn borrow(&self) -> Ref<T> {
self.try_borrow().expect("DOMRefCell<T> already mutably borrowed")
}
/// Mutably borrows the wrapped value.
///
/// The borrow lasts until the returned `RefMut` exits scope. The value
/// cannot be borrowed while this borrow is active.
///
/// # Panics
///
/// Panics if this is called off the script thread.
///
/// Panics if the value is currently borrowed.
pub fn borrow_mut(&self) -> RefMut<T> {
self.try_borrow_mut().expect("DOMRefCell<T> already borrowed")
}
/// Attempts to immutably borrow the wrapped value.
///
/// The borrow lasts until the returned `Ref` exits scope. Multiple
/// immutable borrows can be taken out at the same time.
///
/// Returns `None` if the value is currently mutably borrowed.
///
/// # Panics
///
/// Panics if this is called off the script thread.
pub fn try_borrow(&self) -> Result<Ref<T>, BorrowError<T>> {
debug_assert!(thread_state::get().is_script());
self.value.try_borrow()
}
/// Mutably borrows the wrapped value.
///
/// The borrow lasts until the returned `RefMut` exits scope. The value
/// cannot be borrowed while this borrow is active.
///
/// Returns `None` if the value is currently borrowed.
///
/// # Panics
///
/// Panics if this is called off the script thread.
pub fn try_borrow_mut(&self) -> Result<RefMut<T>, BorrowMutError<T>> {
debug_assert!(thread_state::get().is_script());
self.value.try_borrow_mut()
}
}
|
