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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#![allow(unsafe_code)]
use std::cell::UnsafeCell;
use std::sync::atomic::AtomicUsize;
mod internal;
pub use internal::{AtomicRef, AtomicRefMut};
pub struct AtomicRefCell<T: ?Sized> {
counter: AtomicUsize,
data: UnsafeCell<T>,
}
impl<T> AtomicRefCell<T> {
#[inline]
pub const fn new(value: T) -> Self {
Self {
counter: AtomicUsize::new(0),
data: UnsafeCell::new(value),
}
}
}
impl<T: ?Sized> AtomicRefCell<T> {
#[inline]
pub fn borrow(&self) -> AtomicRef<'_, T> {
AtomicRef::new(self).unwrap()
}
#[inline]
pub fn try_borrow(&self) -> Option<AtomicRef<'_, T>> {
AtomicRef::new(self)
}
#[inline]
pub fn borrow_mut(&self) -> AtomicRefMut<'_, T> {
AtomicRefMut::new(self).unwrap()
}
#[inline]
pub fn try_borrow_mut(&self) -> Option<AtomicRefMut<'_, T>> {
AtomicRefMut::new(self)
}
}
// SAFETY: Accesses to the inner data are synchronized by the atomic reference counter.
unsafe impl<T: ?Sized + Send> Send for AtomicRefCell<T> {}
// SAFETY: Accesses to the inner data are synchronized by the atomic reference counter. Additional
// `Send` bound is needed because `AtomicRefCell` provides mutable access behind a shared reference.
unsafe impl<T: ?Sized + Send + Sync> Sync for AtomicRefCell<T> {}
impl<T: std::fmt::Debug> std::fmt::Debug for AtomicRefCell<T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let val = self.try_borrow();
if let Some(val) = val {
f.debug_tuple("AtomicRefCell").field(&*val).finish()
} else {
f.debug_tuple("AtomicRefCell")
.field(&format_args!("[borrowed]"))
.finish()
}
}
}