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use super::ref_counted::RefCounted;
use super::{Collectible, Guard, Ptr};
use crate::collector::Collector;
use std::mem::forget;
use std::ops::Deref;
use std::panic::UnwindSafe;
use std::ptr::{addr_of, NonNull};
/// [`Owned`] uniquely owns an instance.
///
/// The instance it passed to the `EBR` garbage collector when the [`Owned`] is dropped.
#[derive(Debug)]
pub struct Owned<T> {
instance_ptr: NonNull<RefCounted<T>>,
}
impl<T: 'static> Owned<T> {
/// Creates a new instance of [`Owned`].
///
/// The type of the instance must be determined at compile-time, must not contain non-static
/// references, and must not be a non-static reference since the instance can, theoretically,
/// survive the process. For instance, `struct Disallowed<'l, T>(&'l T)` is not allowed,
/// because an instance of the type cannot outlive `'l` whereas the garbage collector does not
/// guarantee that the instance is dropped within `'l`.
///
/// # Examples
///
/// ```
/// use sdd::Owned;
///
/// let owned: Owned<usize> = Owned::new(31);
/// ```
#[inline]
pub fn new(t: T) -> Self {
let owned = Box::new(RefCounted::new_unique(t));
Self {
instance_ptr: unsafe { NonNull::new_unchecked(Box::into_raw(owned)) },
}
}
}
impl<T> Owned<T> {
/// Creates a new [`Owned`] without checking the lifetime of `T`.
///
/// # Safety
///
/// `T::drop` can be run after the [`Owned`] is dropped, therefore it is safe only if `T::drop`
/// does not access short-lived data or [`std::mem::needs_drop`] is `false` for `T`.
///
/// # Examples
///
/// ```
/// use sdd::Owned;
///
/// let hello = String::from("hello");
/// let owned: Owned<&str> = unsafe { Owned::new_unchecked(hello.as_str()) };
/// ```
#[inline]
pub unsafe fn new_unchecked(t: T) -> Self {
let owned = Box::new(RefCounted::new_unique(t));
Self {
instance_ptr: unsafe { NonNull::new_unchecked(Box::into_raw(owned)) },
}
}
/// Returns a [`Ptr`] to the instance that may live as long as the supplied [`Guard`].
///
/// # Examples
///
/// ```
/// use sdd::{Guard, Owned};
///
/// let owned: Owned<usize> = Owned::new(37);
/// let guard = Guard::new();
/// let ptr = owned.get_guarded_ptr(&guard);
/// drop(owned);
///
/// assert_eq!(*ptr.as_ref().unwrap(), 37);
/// ```
#[inline]
#[must_use]
pub fn get_guarded_ptr<'g>(&self, _guard: &'g Guard) -> Ptr<'g, T> {
Ptr::from(self.instance_ptr.as_ptr())
}
/// Returns a reference to the instance that may live as long as the supplied [`Guard`].
///
/// # Examples
///
/// ```
/// use sdd::{Guard, Owned};
///
/// let owned: Owned<usize> = Owned::new(37);
/// let guard = Guard::new();
/// let ref_b = owned.get_guarded_ref(&guard);
/// drop(owned);
///
/// assert_eq!(*ref_b, 37);
/// ```
#[inline]
#[must_use]
pub fn get_guarded_ref<'g>(&self, _guard: &'g Guard) -> &'g T {
unsafe { std::mem::transmute(&**self.underlying()) }
}
/// Returns a mutable reference to the instance.
///
/// # Safety
///
/// The method is `unsafe` since there can be a [`Ptr`] to the instance.
///
/// # Examples
///
/// ```
/// use sdd::Owned;
///
/// let mut owned: Owned<usize> = Owned::new(38);
/// unsafe {
/// *owned.get_mut() += 1;
/// }
/// assert_eq!(*owned, 39);
/// ```
#[inline]
pub unsafe fn get_mut(&mut self) -> &mut T {
self.instance_ptr.as_mut().get_mut_unique()
}
/// Provides a raw pointer to the instance.
///
/// # Examples
///
/// ```
/// use sdd::Owned;
/// use std::sync::atomic::AtomicBool;
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let owned: Owned<usize> = Owned::new(10);
///
/// assert_eq!(unsafe { *owned.as_ptr() }, 10);
/// ```
#[inline]
#[must_use]
pub fn as_ptr(&self) -> *const T {
addr_of!(**self.underlying())
}
/// Releases the ownership by passing `self` to the given [`Guard`].
///
/// # Examples
///
/// ```
/// use sdd::{Guard, Owned};
///
/// let owned: Owned<usize> = Owned::new(47);
/// let guard = Guard::new();
/// owned.release(&guard);
/// ```
#[inline]
pub fn release(mut self, guard: &Guard) {
self.pass_underlying_to_collector(guard);
forget(self);
}
/// Drops the instance immediately.
///
/// # Safety
///
/// The caller must ensure that there is no [`Ptr`] pointing to the instance.
///
/// # Examples
///
/// ```
/// use sdd::Owned;
/// use std::sync::atomic::AtomicBool;
/// use std::sync::atomic::Ordering::Relaxed;
///
/// static DROPPED: AtomicBool = AtomicBool::new(false);
/// struct T(&'static AtomicBool);
/// impl Drop for T {
/// fn drop(&mut self) {
/// self.0.store(true, Relaxed);
/// }
/// }
///
/// let owned: Owned<T> = Owned::new(T(&DROPPED));
/// assert!(!DROPPED.load(Relaxed));
///
/// unsafe {
/// owned.drop_in_place();
/// }
///
/// assert!(DROPPED.load(Relaxed));
/// ```
#[inline]
pub unsafe fn drop_in_place(mut self) {
drop(Box::from_raw(self.instance_ptr.as_mut()));
forget(self);
}
/// Provides a raw pointer to its [`RefCounted`].
#[inline]
pub(super) const fn get_underlying_ptr(&self) -> *mut RefCounted<T> {
self.instance_ptr.as_ptr()
}
/// Creates a new [`Owned`] from the given pointer.
#[inline]
pub(super) fn from(ptr: NonNull<RefCounted<T>>) -> Self {
debug_assert_eq!(
unsafe {
ptr.as_ref()
.ref_cnt()
.load(std::sync::atomic::Ordering::Relaxed)
},
0
);
Self { instance_ptr: ptr }
}
/// Returns a reference to the underlying instance.
#[inline]
fn underlying(&self) -> &RefCounted<T> {
unsafe { self.instance_ptr.as_ref() }
}
#[inline]
fn pass_underlying_to_collector(&mut self, guard: &Guard) {
let dyn_mut: &mut dyn Collectible = unsafe { self.instance_ptr.as_mut() };
let dyn_mut_ptr: *mut dyn Collectible = unsafe { std::mem::transmute(dyn_mut) };
guard.collect(dyn_mut_ptr);
}
}
impl<T> AsRef<T> for Owned<T> {
#[inline]
fn as_ref(&self) -> &T {
self.underlying()
}
}
impl<T> Deref for Owned<T> {
type Target = T;
#[inline]
fn deref(&self) -> &Self::Target {
self.underlying()
}
}
impl<T> Drop for Owned<T> {
#[inline]
fn drop(&mut self) {
let guard = Guard::new_for_drop(Collector::current());
self.pass_underlying_to_collector(&guard);
}
}
unsafe impl<T: Send> Send for Owned<T> {}
unsafe impl<T: Sync> Sync for Owned<T> {}
impl<T: UnwindSafe> UnwindSafe for Owned<T> {}