use std::marker::PhantomData;
use std::ops::{Deref, DerefMut};
use crate::{
key::Keyable,
lockable::{Lockable, OwnedLockable},
};
/// returns `true` if the list contains a duplicate
#[must_use]
fn contains_duplicates(l: &[usize]) -> bool {
for i in 0..l.len() {
for j in (i + 1)..l.len() {
if l[i] == l[j] {
return true;
}
}
}
false
}
/// A type which can be locked.
///
/// This could be a tuple of [`Lockable`] types, an array, or a `Vec`. But it
/// can be safely locked without causing a deadlock. To do this, it is very
/// important that no duplicate locks are included within.
#[derive(Debug, Clone, Copy)]
pub struct LockCollection<L> {
collection: L,
}
/// A guard for a generic [`Lockable`] type.
pub struct LockGuard<'a, 'key: 'a, L: Lockable<'a>, Key: Keyable + 'key> {
guard: L::Output,
key: Key,
_phantom: PhantomData<&'key ()>,
}
impl<'a, L: OwnedLockable<'a>> From<L> for LockCollection<L> {
fn from(value: L) -> Self {
Self::new(value)
}
}
impl<'a, L: OwnedLockable<'a>> AsRef<L> for LockCollection<L> {
fn as_ref(&self) -> &L {
&self.collection
}
}
impl<'a, L: OwnedLockable<'a>> AsMut<L> for LockCollection<L> {
fn as_mut(&mut self) -> &mut L {
&mut self.collection
}
}
impl<'a, L: OwnedLockable<'a>> AsRef<Self> for LockCollection<L> {
fn as_ref(&self) -> &Self {
self
}
}
impl<'a, L: OwnedLockable<'a>> AsMut<Self> for LockCollection<L> {
fn as_mut(&mut self) -> &mut Self {
self
}
}
impl<L: IntoIterator> IntoIterator for LockCollection<L> {
type Item = L::Item;
type IntoIter = L::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.collection.into_iter()
}
}
impl<'a, L> IntoIterator for &'a LockCollection<L>
where
&'a L: IntoIterator,
{
type Item = <&'a L as IntoIterator>::Item;
type IntoIter = <&'a L as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.collection.into_iter()
}
}
impl<'a, L> IntoIterator for &'a mut LockCollection<L>
where
&'a mut L: IntoIterator,
{
type Item = <&'a mut L as IntoIterator>::Item;
type IntoIter = <&'a mut L as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.collection.into_iter()
}
}
impl<'a, L: OwnedLockable<'a>, I: FromIterator<L> + OwnedLockable<'a>> FromIterator<L>
for LockCollection<I>
{
fn from_iter<T: IntoIterator<Item = L>>(iter: T) -> Self {
let iter: I = iter.into_iter().collect();
Self::new(iter)
}
}
impl<'a, E: OwnedLockable<'a> + Extend<L>, L: OwnedLockable<'a>> Extend<L> for LockCollection<E> {
fn extend<T: IntoIterator<Item = L>>(&mut self, iter: T) {
self.collection.extend(iter)
}
}
impl<'a, L: OwnedLockable<'a>> LockCollection<L> {
/// Creates a new collection of owned locks.
///
/// Because the locks are owned, there's no need to do any checks for
/// duplicate values.
#[must_use]
pub const fn new(collection: L) -> Self {
Self { collection }
}
/// Creates a new collection of owned locks.
///
/// Because the locks are owned, there's no need to do any checks for
/// duplicate values.
#[must_use]
pub const fn new_ref(collection: &L) -> LockCollection<&L> {
LockCollection { collection }
}
}
impl<L> LockCollection<L> {
/// Creates a new collections of locks.
///
/// # Safety
///
/// This results in undefined behavior if any locks are presented twice
/// within this collection.
#[must_use]
pub const unsafe fn new_unchecked(collection: L) -> Self {
Self { collection }
}
}
impl<'a, L: Lockable<'a>> LockCollection<L> {
/// Creates a new collection of locks.
///
/// This returns `None` if any locks are found twice in the given
/// collection.
///
/// # Performance
///
/// This does a check at runtime to make sure that the collection contains
/// no two copies of the same lock. This is an `O(n^2)` operation. Prefer
/// [`LockCollection::new`] or [`LockCollection::new_ref`] instead.
#[must_use]
pub fn try_new(collection: L) -> Option<Self> {
let ptrs = collection.get_ptrs();
if contains_duplicates(&ptrs) {
return None;
}
Some(Self { collection })
}
/// Locks the lockable type and returns a guard that can be used to access
/// the underlying data.
pub fn lock<'key: 'a, Key: Keyable + 'key>(&'a self, key: Key) -> LockGuard<'a, 'key, L, Key> {
LockGuard {
// safety: we have the thread's key
guard: unsafe { self.collection.lock() },
key,
_phantom: PhantomData,
}
}
/// Attempts to lock the guard without blocking.
///
/// If successful, this method returns a guard that can be used to access
/// the data. Otherwise, `None` is returned.
pub fn try_lock<'key: 'a, Key: Keyable + 'key>(
&'a self,
key: Key,
) -> Option<LockGuard<'a, 'key, L, Key>> {
// safety: we have the thread's key
unsafe { self.collection.try_lock() }.map(|guard| LockGuard {
guard,
key,
_phantom: PhantomData,
})
}
/// Unlocks the underlying lockable data type, returning the key that's
/// associated with it.
#[allow(clippy::missing_const_for_fn)]
pub fn unlock<'key: 'a, Key: Keyable + 'key>(guard: LockGuard<'a, 'key, L, Key>) -> Key {
drop(guard.guard);
guard.key
}
}
impl<'a, L: 'a> LockCollection<L>
where
&'a L: IntoIterator,
{
/// Returns an iterator over references to each value in the collection.
pub fn iter(&'a self) -> <&'a L as IntoIterator>::IntoIter {
self.into_iter()
}
}
impl<'a, L: 'a> LockCollection<L>
where
&'a mut L: IntoIterator,
{
/// Returns an iterator over mutable references to each value in the
/// collection.
pub fn iter_mut(&'a mut self) -> <&'a mut L as IntoIterator>::IntoIter {
self.into_iter()
}
}
impl<'a, 'key: 'a, L: Lockable<'a>, Key: Keyable> Deref for LockGuard<'a, 'key, L, Key> {
type Target = L::Output;
fn deref(&self) -> &Self::Target {
&self.guard
}
}
impl<'a, 'key: 'a, L: Lockable<'a>, Key: Keyable> DerefMut for LockGuard<'a, 'key, L, Key> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.guard
}
}
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