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use super::maybe_std::AtomicPtr;
use super::ref_counted::RefCounted;
use super::{Guard, Owned, Ptr, Tag};
use std::mem::forget;
use std::panic::UnwindSafe;
use std::ptr::{null, null_mut, NonNull};
use std::sync::atomic::Ordering::{self, Relaxed};
/// [`AtomicOwned`] owns the underlying instance, and allows users to perform atomic operations
/// on the pointer to it.
#[derive(Debug)]
pub struct AtomicOwned<T> {
instance_ptr: AtomicPtr<RefCounted<T>>,
}
/// A pair of [`Owned`] and [`Ptr`] of the same type.
pub type OwnedPtrPair<'g, T> = (Option<Owned<T>>, Ptr<'g, T>);
impl<T: 'static> AtomicOwned<T> {
/// Creates a new [`AtomicOwned`] from an instance of `T`.
///
/// 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,
/// live as long as 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::AtomicOwned;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(10);
/// ```
#[inline]
pub fn new(t: T) -> Self {
Self {
instance_ptr: AtomicPtr::new(RefCounted::new_unique(t).cast_mut()),
}
}
}
impl<T> AtomicOwned<T> {
/// Creates a new [`AtomicOwned`] from an [`Owned`] of `T`.
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Owned};
///
/// let owned: Owned<usize> = Owned::new(10);
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::from(owned);
/// ```
#[cfg(not(feature = "loom"))]
#[inline]
#[must_use]
pub const fn from(owned: Owned<T>) -> Self {
let ptr = owned.underlying_ptr();
forget(owned);
let instance_ptr: std::sync::atomic::AtomicPtr<RefCounted<T>> =
AtomicPtr::new(ptr.cast_mut());
Self { instance_ptr }
}
/// Creates a new [`AtomicOwned`] from an [`Owned`] of `T`.
#[cfg(feature = "loom")]
#[inline]
#[must_use]
pub fn from(owned: Owned<T>) -> Self {
let ptr = owned.underlying_ptr();
forget(owned);
let instance_ptr: loom::sync::atomic::AtomicPtr<RefCounted<T>> =
AtomicPtr::new(ptr.cast_mut());
Self { instance_ptr }
}
/// Creates a null [`AtomicOwned`].
///
/// # Examples
///
/// ```
/// use sdd::AtomicOwned;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::null();
/// ```
#[cfg(not(feature = "loom"))]
#[inline]
#[must_use]
pub const fn null() -> Self {
let instance_ptr: std::sync::atomic::AtomicPtr<RefCounted<T>> = AtomicPtr::new(null_mut());
Self { instance_ptr }
}
/// Creates a null [`AtomicOwned`].
#[cfg(feature = "loom")]
#[inline]
#[must_use]
pub fn null() -> Self {
let instance_ptr: loom::sync::atomic::AtomicPtr<RefCounted<T>> = AtomicPtr::new(null_mut());
Self { instance_ptr }
}
/// Returns `true` if the [`AtomicOwned`] is null.
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::null();
/// atomic_owned.update_tag_if(Tag::Both, |p| p.tag() == Tag::None, Relaxed, Relaxed);
/// assert!(atomic_owned.is_null(Relaxed));
/// ```
#[inline]
#[must_use]
pub fn is_null(&self, order: Ordering) -> bool {
Tag::unset_tag(self.instance_ptr.load(order)).is_null()
}
/// Loads a pointer value from the [`AtomicOwned`].
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Guard};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(11);
/// let guard = Guard::new();
/// let ptr = atomic_owned.load(Relaxed, &guard);
/// assert_eq!(*ptr.as_ref().unwrap(), 11);
/// ```
#[inline]
#[must_use]
pub fn load<'g>(&self, order: Ordering, _guard: &'g Guard) -> Ptr<'g, T> {
Ptr::from(self.instance_ptr.load(order))
}
/// Stores the given value into the [`AtomicOwned`] and returns the original value.
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Guard, Owned, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(14);
/// let guard = Guard::new();
/// let (old, tag) = atomic_owned.swap((Some(Owned::new(15)), Tag::Second), Relaxed);
/// assert_eq!(tag, Tag::None);
/// assert_eq!(*old.unwrap(), 14);
/// let (old, tag) = atomic_owned.swap((None, Tag::First), Relaxed);
/// assert_eq!(tag, Tag::Second);
/// assert_eq!(*old.unwrap(), 15);
/// let (old, tag) = atomic_owned.swap((None, Tag::None), Relaxed);
/// assert_eq!(tag, Tag::First);
/// assert!(old.is_none());
/// ```
#[inline]
pub fn swap(&self, new: (Option<Owned<T>>, Tag), order: Ordering) -> (Option<Owned<T>>, Tag) {
let desired = Tag::update_tag(
new.0.as_ref().map_or_else(null, Owned::underlying_ptr),
new.1,
)
.cast_mut();
let prev = self.instance_ptr.swap(desired, order);
let tag = Tag::into_tag(prev);
let prev_ptr = Tag::unset_tag(prev).cast_mut();
forget(new);
(NonNull::new(prev_ptr).map(Owned::from), tag)
}
/// Returns its [`Tag`].
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::null();
/// assert_eq!(atomic_owned.tag(Relaxed), Tag::None);
/// ```
#[inline]
#[must_use]
pub fn tag(&self, order: Ordering) -> Tag {
Tag::into_tag(self.instance_ptr.load(order))
}
/// Sets a new [`Tag`] if the given condition is met.
///
/// Returns `true` if the new [`Tag`] has been successfully set.
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::null();
/// assert!(atomic_owned.update_tag_if(Tag::Both, |p| p.tag() == Tag::None, Relaxed, Relaxed));
/// assert_eq!(atomic_owned.tag(Relaxed), Tag::Both);
/// ```
#[inline]
pub fn update_tag_if<F: FnMut(Ptr<T>) -> bool>(
&self,
tag: Tag,
mut condition: F,
set_order: Ordering,
fetch_order: Ordering,
) -> bool {
self.instance_ptr
.fetch_update(set_order, fetch_order, |ptr| {
if condition(Ptr::from(ptr)) {
Some(Tag::update_tag(ptr, tag).cast_mut())
} else {
None
}
})
.is_ok()
}
/// Stores `new` into the [`AtomicOwned`] if the current value is the same as `current`.
///
/// Returns the previously held value and the updated [`Ptr`].
///
/// # Errors
///
/// Returns `Err` with the supplied [`Owned`] and the current [`Ptr`].
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Guard, Owned, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(17);
/// let guard = Guard::new();
///
/// let mut ptr = atomic_owned.load(Relaxed, &guard);
/// assert_eq!(*ptr.as_ref().unwrap(), 17);
///
/// atomic_owned.update_tag_if(Tag::Both, |_| true, Relaxed, Relaxed);
/// assert!(atomic_owned.compare_exchange(
/// ptr, (Some(Owned::new(18)), Tag::First), Relaxed, Relaxed, &guard).is_err());
///
/// ptr.set_tag(Tag::Both);
/// let old: Owned<usize> = atomic_owned.compare_exchange(
/// ptr, (Some(Owned::new(18)), Tag::First), Relaxed, Relaxed, &guard).unwrap().0.unwrap();
/// assert_eq!(*old, 17);
/// drop(old);
///
/// assert!(atomic_owned.compare_exchange(
/// ptr, (Some(Owned::new(19)), Tag::None), Relaxed, Relaxed, &guard).is_err());
/// assert_eq!(*ptr.as_ref().unwrap(), 17);
/// ```
#[inline]
pub fn compare_exchange<'g>(
&self,
current: Ptr<'g, T>,
new: (Option<Owned<T>>, Tag),
success: Ordering,
failure: Ordering,
_guard: &'g Guard,
) -> Result<OwnedPtrPair<'g, T>, OwnedPtrPair<'g, T>> {
let desired = Tag::update_tag(
new.0.as_ref().map_or_else(null, Owned::underlying_ptr),
new.1,
)
.cast_mut();
match self.instance_ptr.compare_exchange(
current.as_underlying_ptr().cast_mut(),
desired,
success,
failure,
) {
Ok(prev) => {
let prev_owned = NonNull::new(Tag::unset_tag(prev).cast_mut()).map(Owned::from);
forget(new);
Ok((prev_owned, Ptr::from(desired)))
}
Err(actual) => Err((new.0, Ptr::from(actual))),
}
}
/// Stores `new` into the [`AtomicOwned`] if the current value is the same as `current`.
///
/// This method is allowed to spuriously fail even when the comparison succeeds.
///
/// Returns the previously held value and the updated [`Ptr`].
///
/// # Errors
///
/// Returns `Err` with the supplied [`Owned`] and the current [`Ptr`].
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Owned, Guard, Tag};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(17);
/// let guard = Guard::new();
///
/// let mut ptr = atomic_owned.load(Relaxed, &guard);
/// assert_eq!(*ptr.as_ref().unwrap(), 17);
///
/// while let Err((_, actual)) = atomic_owned.compare_exchange_weak(
/// ptr,
/// (Some(Owned::new(18)), Tag::First),
/// Relaxed,
/// Relaxed,
/// &guard) {
/// ptr = actual;
/// }
///
/// let mut ptr = atomic_owned.load(Relaxed, &guard);
/// assert_eq!(*ptr.as_ref().unwrap(), 18);
/// ```
#[inline]
pub fn compare_exchange_weak<'g>(
&self,
current: Ptr<'g, T>,
new: (Option<Owned<T>>, Tag),
success: Ordering,
failure: Ordering,
_guard: &'g Guard,
) -> Result<OwnedPtrPair<'g, T>, OwnedPtrPair<'g, T>> {
let desired = Tag::update_tag(
new.0.as_ref().map_or_else(null, Owned::underlying_ptr),
new.1,
)
.cast_mut();
match self.instance_ptr.compare_exchange_weak(
current.as_underlying_ptr().cast_mut(),
desired,
success,
failure,
) {
Ok(prev) => {
let prev_owned = NonNull::new(Tag::unset_tag(prev).cast_mut()).map(Owned::from);
forget(new);
Ok((prev_owned, Ptr::from(desired)))
}
Err(actual) => Err((new.0, Ptr::from(actual))),
}
}
/// Converts `self` into an [`Owned`].
///
/// Returns `None` if `self` did not own an instance.
///
/// # Examples
///
/// ```
/// use sdd::{AtomicOwned, Owned};
/// use std::sync::atomic::Ordering::Relaxed;
///
/// let atomic_owned: AtomicOwned<usize> = AtomicOwned::new(55);
/// let owned: Owned<usize> = atomic_owned.into_owned(Relaxed).unwrap();
/// assert_eq!(*owned, 55);
/// ```
#[inline]
#[must_use]
pub fn into_owned(self, order: Ordering) -> Option<Owned<T>> {
let ptr = self.instance_ptr.swap(null_mut(), order);
if let Some(underlying_ptr) = NonNull::new(Tag::unset_tag(ptr).cast_mut()) {
return Some(Owned::from(underlying_ptr));
}
None
}
}
impl<T> Default for AtomicOwned<T> {
#[inline]
fn default() -> Self {
Self::null()
}
}
impl<T> Drop for AtomicOwned<T> {
#[inline]
fn drop(&mut self) {
if let Some(ptr) = NonNull::new(Tag::unset_tag(self.instance_ptr.load(Relaxed)).cast_mut())
{
drop(Owned::from(ptr));
}
}
}
unsafe impl<T: Send> Send for AtomicOwned<T> {}
unsafe impl<T: Sync> Sync for AtomicOwned<T> {}
impl<T: UnwindSafe> UnwindSafe for AtomicOwned<T> {}