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use crate::{Handle, Node};
use core::marker::PhantomData;
use core::ops::Deref;
use core::ptr::NonNull;
use core::sync::atomic::{AtomicUsize, Ordering, fence};
pub struct Shared<T> {
pub(crate) node: NonNull<Node<SharedInner<T>>>,
pub(crate) phantom: PhantomData<SharedInner<T>>,
}
pub(crate) struct SharedInner<T> {
count: AtomicUsize,
data: T,
}
unsafe impl<T: Send + Sync> Send for Shared<T> {}
unsafe impl<T: Send + Sync> Sync for Shared<T> {}
impl<T: Send + 'static> Shared<T> {
pub fn new(handle: &Handle, data: T) -> Shared<T> {
Shared {
node: unsafe {
NonNull::new_unchecked(Node::alloc(handle, SharedInner {
count: AtomicUsize::new(1),
data,
}))
},
phantom: PhantomData,
}
}
}
impl<T> Shared<T> {
pub fn get_mut(this: &mut Self) -> Option<&mut T> {
unsafe {
if this.node.as_ref().data.count.load(Ordering::Acquire) == 1 {
Some(&mut this.node.as_mut().data.data)
} else {
None
}
}
}
}
impl<T> Clone for Shared<T> {
fn clone(&self) -> Self {
unsafe {
self.node.as_ref().data.count.fetch_add(1, Ordering::Relaxed);
}
Shared { node: self.node, phantom: PhantomData }
}
}
impl<T> Deref for Shared<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
unsafe { &self.node.as_ref().data.data }
}
}
impl<T> Drop for Shared<T> {
fn drop(&mut self) {
unsafe {
let count = self.node.as_ref().data.count.fetch_sub(1, Ordering::Release);
if count == 1 {
fence(Ordering::Acquire);
Node::queue_drop(self.node.as_ptr());
}
}
}
}
#[cfg(test)]
mod tests {
use crate::{Collector, Shared};
use core::sync::atomic::{AtomicUsize, Ordering};
#[test]
fn shared() {
extern crate alloc;
use alloc::sync::Arc;
struct Test(Arc<AtomicUsize>);
impl Drop for Test {
fn drop(&mut self) {
self.0.fetch_add(1, Ordering::Relaxed);
}
}
let counter = Arc::new(AtomicUsize::new(0));
let mut collector = Collector::new();
let handle = collector.handle();
let shared = Shared::new(&handle, Test(counter.clone()));
let mut copies = alloc::vec::Vec::new();
for _ in 0..10 {
copies.push(shared.clone());
}
assert_eq!(counter.load(Ordering::Relaxed), 0);
core::mem::drop(shared);
core::mem::drop(copies);
collector.collect();
assert_eq!(counter.load(Ordering::Relaxed), 1);
}
#[test]
fn get_mut() {
let collector = Collector::new();
let mut x = Shared::new(&collector.handle(), 3);
*Shared::get_mut(&mut x).unwrap() = 4;
assert_eq!(*x, 4);
let _y = Shared::clone(&x);
assert!(Shared::get_mut(&mut x).is_none());
}
}