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use std::sync::Arc;
use std::sync::atomic::{AtomicPtr, Ordering};
use std::ptr;
use std::fmt;
#[cfg(test)]
mod test;
pub struct AtomicBox<T> {
ptr: AtomicPtr<Arc<T>>,
}
impl<T> AtomicBox<T> {
pub fn new(data: T) -> AtomicBox<T> {
let arc = Box::new(Arc::new(data));
let ptr = AtomicPtr::new(Box::into_raw(arc));
AtomicBox { ptr: ptr }
}
pub fn load(&self) -> Arc<T> {
loop {
let ptr = self.ptr.swap(ptr::null_mut(), Ordering::Acquire);
if ptr == ptr::null_mut() {
continue;
}
let arc = unsafe { &mut *ptr }.clone();
self.ptr.swap(ptr, Ordering::AcqRel);
return arc;
}
}
pub fn store(&self, data: T) {
self.swap(data);
}
pub fn swap(&self, data: T) -> Box<Arc<T>> {
let arc = Box::new(Arc::new(data));
let ptr = Box::into_raw(arc);
loop {
let old_ptr = self.ptr.swap(ptr::null_mut(), Ordering::AcqRel);
if old_ptr == ptr::null_mut() {
continue;
}
let old_arc = unsafe { Box::from_raw(old_ptr) };
self.ptr.swap(ptr, Ordering::AcqRel);
return old_arc;
}
}
}
impl<T> Drop for AtomicBox<T> {
fn drop(&mut self) {
let _: Box<Arc<T>> = unsafe { Box::from_raw(*self.ptr.get_mut()) };
}
}
impl<T> fmt::Debug for AtomicBox<T>
where T: fmt::Debug
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("AtomicBox")
.field("ptr", &self.load())
.finish()
}
}