use std::sync::atomic::{AtomicPtr, Ordering};
use std::ptr::null_mut;
pub struct BoxRcu<T> {
inner: AtomicPtr<List<T>>,
}
pub struct List<T> {
value: T,
next: AtomicPtr<List<T>>,
}
impl<T> std::ops::Deref for BoxRcu<T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { &(*self.inner.load(Ordering::Acquire)).value }
}
}
impl<T> std::borrow::Borrow<T> for BoxRcu<T> {
fn borrow(&self) -> &T {
&*self
}
}
impl<T> Drop for List<T> {
fn drop(&mut self) {
let next = self.next.load(Ordering::Acquire);
if next != null_mut() {
unsafe { Box::from_raw(next); }
}
}
}
impl<'a,T: Clone> BoxRcu<T> {
pub fn new(x: T) -> Self {
BoxRcu {
inner: AtomicPtr::new(Box::into_raw(Box::new(List {
value: x,
next: AtomicPtr::new(null_mut()),
}))),
}
}
pub fn update(&'a self) -> Guard<'a, T> {
Guard {
list: AtomicPtr::new(Box::into_raw(Box::new(List {
value: (*(*self)).clone(),
next: unsafe { AtomicPtr::new((*self.inner.load(Ordering::Acquire))
.next.load(Ordering::Acquire)) },
}))),
thebox: &self,
}
}
pub fn clean(&mut self) {
let inner = self.inner.load(Ordering::Acquire);
let next = unsafe { (*inner).next.swap(null_mut(), Ordering::Acquire) };
unsafe { Box::from_raw(next); }
}
}
pub struct Guard<'a,T: Clone> {
list: AtomicPtr<List<T>>,
thebox: &'a BoxRcu<T>,
}
impl<'a,T: Clone> std::ops::Deref for Guard<'a,T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { &(*self.list.load(Ordering::Acquire)).value }
}
}
impl<'a,T: Clone> std::ops::DerefMut for Guard<'a,T> {
fn deref_mut(&mut self) -> &mut T {
unsafe { &mut (*self.list.load(Ordering::Acquire)).value }
}
}
impl<'a,T: Clone> Drop for Guard<'a,T> {
fn drop(&mut self) {
self.thebox.inner.store(self.list.load(Ordering::Acquire), Ordering::Release);
}
}