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    #[allow(clippy::new_without_default)]
17    pub const fn new() -> Self {
18        Self(OnceLock::new())
19    }
20
21    /// Initialize the value inside this lock. Panics if the lock has been previously initialized.
22    pub fn set(&self, val: T) {
23        assert!(self.0.set(val).is_ok());
24    }
25
26    /// Get a reference to the value inside this lock. Panics if the lock has not been initialized.
27    ///
28    /// # Safety
29    ///   The caller must ensure that it does not mutate value contained inside this lock
30    ///   (using interior mutability).
31    pub unsafe fn get(&self) -> &T {
32        self.0.get().unwrap()
33    }
34}
35
36unsafe impl<T> Sync for ThreadUnsafeOnceLock<T> {}
37unsafe impl<T> Send for ThreadUnsafeOnceLock<T> {}
script_bindings/lock.rs

script_bindings/
lock.rs
