script_bindings/
lock.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
5use std::sync::OnceLock;
6
7/// A OnceLock wrapping a type that is not considered threadsafe by the Rust compiler, but
8/// will be used in a threadsafe manner (it will not be mutated, after being initialized).
9///
10/// This is needed to allow using JS API types (which usually involve raw pointers) in static initializers,
11/// when Servo guarantees through the use of OnceLock that only one thread will ever initialize
12/// the value.
13pub struct ThreadUnsafeOnceLock<T>(OnceLock<T>);
14
15impl<T> ThreadUnsafeOnceLock<T> {
16    pub const fn new() -> Self {
17        Self(OnceLock::new())
18    }
19
20    /// Initialize the value inside this lock. Panics if the lock has been previously initialized.
21    pub fn set(&self, val: T) {
22        assert!(self.0.set(val).is_ok());
23    }
24
25    /// Get a reference to the value inside this lock. Panics if the lock has not been initialized.
26    ///
27    /// # Safety
28    ///   The caller must ensure that it does not mutate value contained inside this lock
29    ///   (using interior mutability).
30    pub unsafe fn get(&self) -> &T {
31        self.0.get().unwrap()
32    }
33}
34
35unsafe impl<T> Sync for ThreadUnsafeOnceLock<T> {}
36unsafe impl<T> Send for ThreadUnsafeOnceLock<T> {}
script_bindings/lock.rs

script_bindings/
lock.rs
