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use crate::loom::sync::atomic::AtomicPtr;
use std::ptr;
use std::sync::atomic::Ordering::AcqRel;
pub(crate) struct AtomicCell<T> {
data: AtomicPtr<T>,
}
unsafe impl<T: Send> Send for AtomicCell<T> {}
unsafe impl<T: Send> Sync for AtomicCell<T> {}
impl<T> AtomicCell<T> {
pub(crate) fn new(data: Option<Box<T>>) -> AtomicCell<T> {
AtomicCell {
data: AtomicPtr::new(to_raw(data)),
}
}
pub(crate) fn swap(&self, val: Option<Box<T>>) -> Option<Box<T>> {
let old = self.data.swap(to_raw(val), AcqRel);
from_raw(old)
}
pub(crate) fn set(&self, val: Box<T>) {
let _ = self.swap(Some(val));
}
pub(crate) fn take(&self) -> Option<Box<T>> {
self.swap(None)
}
}
fn to_raw<T>(data: Option<Box<T>>) -> *mut T {
data.map(Box::into_raw).unwrap_or(ptr::null_mut())
}
fn from_raw<T>(val: *mut T) -> Option<Box<T>> {
if val.is_null() {
None
} else {
Some(unsafe { Box::from_raw(val) })
}
}
impl<T> Drop for AtomicCell<T> {
fn drop(&mut self) {
// Free any data still held by the cell
let _ = self.take();
}
}