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
|
/* 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/. */
//! Machinery to conditionally expose things.
use js::jsapi::{HandleObject, JSContext};
use servo_config::prefs::PREFS;
/// A container with a condition.
pub struct Guard<T: Clone + Copy> {
condition: Condition,
value: T,
}
impl<T: Clone + Copy> Guard<T> {
/// Construct a new guarded value.
pub const fn new(condition: Condition, value: T) -> Self {
Guard {
condition: condition,
value: value,
}
}
/// Expose the value if the condition is satisfied.
///
/// The passed handle is the object on which the value may be exposed.
pub unsafe fn expose(&self, cx: *mut JSContext, obj: HandleObject) -> Option<T> {
if self.condition.is_satisfied(cx, obj) {
Some(self.value)
} else {
None
}
}
}
/// A condition to expose things.
pub enum Condition {
/// The condition is satisfied if the function returns true.
Func(unsafe fn(*mut JSContext, HandleObject) -> bool),
/// The condition is satisfied if the preference is set.
Pref(&'static str),
/// The condition is always satisfied.
Satisfied,
}
impl Condition {
unsafe fn is_satisfied(&self, cx: *mut JSContext, obj: HandleObject) -> bool {
match *self {
Condition::Pref(name) => PREFS.get(name).as_boolean().unwrap_or(false),
Condition::Func(f) => f(cx, obj),
Condition::Satisfied => true,
}
}
}
|
