scc/hash_set.rs
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//! [`HashSet`] is a concurrent and asynchronous hash set.
use super::{Equivalent, HashMap};
use std::collections::hash_map::RandomState;
use std::fmt::{self, Debug};
use std::hash::{BuildHasher, Hash};
use std::ops::RangeInclusive;
/// Scalable concurrent hash set.
///
/// [`HashSet`] is a concurrent and asynchronous hash set based on [`HashMap`].
pub struct HashSet<K, H = RandomState>
where
H: BuildHasher,
{
map: HashMap<K, (), H>,
}
/// [`Reserve`] keeps the capacity of the associated [`HashSet`] higher than a certain level.
///
/// The [`HashSet`] does not shrink the capacity below the reserved capacity.
pub type Reserve<'h, K, H = RandomState> = super::hash_map::Reserve<'h, K, (), H>;
impl<K, H> HashSet<K, H>
where
H: BuildHasher,
{
/// Creates an empty [`HashSet`] with the given [`BuildHasher`].
///
/// # Examples
///
/// ```
/// use scc::HashSet;
/// use std::collections::hash_map::RandomState;
///
/// let hashset: HashSet<u64, RandomState> = HashSet::with_hasher(RandomState::new());
/// ```
#[cfg(not(feature = "loom"))]
#[inline]
pub const fn with_hasher(build_hasher: H) -> Self {
Self {
map: HashMap::with_hasher(build_hasher),
}
}
/// Creates an empty [`HashSet`] with the given [`BuildHasher`].
#[cfg(feature = "loom")]
#[inline]
pub fn with_hasher(build_hasher: H) -> Self {
Self {
map: HashMap::with_hasher(build_hasher),
}
}
/// Creates an empty [`HashSet`] with the specified capacity and [`BuildHasher`].
///
/// The actual capacity is equal to or greater than the specified capacity.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
/// use std::collections::hash_map::RandomState;
///
/// let hashset: HashSet<u64, RandomState> =
/// HashSet::with_capacity_and_hasher(1000, RandomState::new());
///
/// let result = hashset.capacity();
/// assert_eq!(result, 1024);
/// ```
#[inline]
pub fn with_capacity_and_hasher(capacity: usize, build_hasher: H) -> Self {
Self {
map: HashMap::with_capacity_and_hasher(capacity, build_hasher),
}
}
}
impl<K, H> HashSet<K, H>
where
K: Eq + Hash,
H: BuildHasher,
{
/// Temporarily increases the minimum capacity of the [`HashSet`].
///
/// A [`Reserve`] is returned if the [`HashSet`] could increase the minimum capacity while the
/// increased capacity is not exclusively owned by the returned [`Reserve`], allowing others to
/// benefit from it. The memory for the additional space may not be immediately allocated if
/// the [`HashSet`] is empty or currently being resized, however once the memory is reserved
/// eventually, the capacity will not shrink below the additional capacity until the returned
/// [`Reserve`] is dropped.
///
/// # Errors
///
/// Returns `None` if a too large number is given.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<usize> = HashSet::with_capacity(1000);
/// assert_eq!(hashset.capacity(), 1024);
///
/// let reserved = hashset.reserve(10000);
/// assert!(reserved.is_some());
/// assert_eq!(hashset.capacity(), 16384);
///
/// assert!(hashset.reserve(usize::MAX).is_none());
/// assert_eq!(hashset.capacity(), 16384);
///
/// for i in 0..16 {
/// assert!(hashset.insert(i).is_ok());
/// }
/// drop(reserved);
///
/// assert_eq!(hashset.capacity(), 1024);
/// ```
#[inline]
pub fn reserve(&self, capacity: usize) -> Option<Reserve<K, H>> {
self.map.reserve(capacity)
}
/// Inserts a key into the [`HashSet`].
///
/// # Errors
///
/// Returns an error along with the supplied key if the key exists.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert_eq!(hashset.insert(1).unwrap_err(), 1);
/// ```
#[inline]
pub fn insert(&self, key: K) -> Result<(), K> {
if let Err((k, ())) = self.map.insert(key, ()) {
return Err(k);
}
Ok(())
}
/// Inserts a key into the [`HashSet`].
///
/// It is an asynchronous method returning an `impl Future` for the caller to await.
///
/// # Errors
///
/// Returns an error along with the supplied key if the key exists.
///
/// function.
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
/// let future_insert = hashset.insert_async(11);
/// ```
#[inline]
pub async fn insert_async(&self, key: K) -> Result<(), K> {
self.map.insert_async(key, ()).await.map_err(|(k, ())| k)
}
/// Removes a key if the key exists.
///
/// Returns `None` if the key does not exist.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.remove(&1).is_none());
/// assert!(hashset.insert(1).is_ok());
/// assert_eq!(hashset.remove(&1).unwrap(), 1);
/// ```
#[inline]
pub fn remove<Q>(&self, key: &Q) -> Option<K>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.remove(key).map(|(k, ())| k)
}
/// Removes a key if the key exists.
///
/// Returns `None` if the key does not exist. It is an asynchronous method returning an
/// `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
/// let future_insert = hashset.insert_async(11);
/// let future_remove = hashset.remove_async(&11);
/// ```
#[inline]
pub async fn remove_async<Q>(&self, key: &Q) -> Option<K>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map
.remove_if_async(key, |()| true)
.await
.map(|(k, ())| k)
}
/// Removes a key if the key exists and the given condition is met.
///
/// Returns `None` if the key does not exist or the condition was not met.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.remove_if(&1, || false).is_none());
/// assert_eq!(hashset.remove_if(&1, || true).unwrap(), 1);
/// ```
#[inline]
pub fn remove_if<Q, F: FnOnce() -> bool>(&self, key: &Q, condition: F) -> Option<K>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.remove_if(key, |()| condition()).map(|(k, ())| k)
}
/// Removes a key if the key exists and the given condition is met.
///
/// Returns `None` if the key does not exist or the condition was not met. It is an
/// asynchronous method returning an `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
/// let future_insert = hashset.insert_async(11);
/// let future_remove = hashset.remove_if_async(&11, || true);
/// ```
#[inline]
pub async fn remove_if_async<Q, F: FnOnce() -> bool>(&self, key: &Q, condition: F) -> Option<K>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map
.remove_if_async(key, |()| condition())
.await
.map(|(k, ())| k)
}
/// Reads a key.
///
/// Returns `None` if the key does not exist.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.read(&1, |_| true).is_none());
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.read(&1, |_| true).unwrap());
/// ```
#[inline]
pub fn read<Q, R, F: FnOnce(&K) -> R>(&self, key: &Q, reader: F) -> Option<R>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.read(key, |k, ()| reader(k))
}
/// Reads a key.
///
/// Returns `None` if the key does not exist. It is an asynchronous method returning an
/// `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
/// let future_insert = hashset.insert_async(11);
/// let future_read = hashset.read_async(&11, |k| *k);
/// ```
#[inline]
pub async fn read_async<Q, R, F: FnOnce(&K) -> R>(&self, key: &Q, reader: F) -> Option<R>
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.read_async(key, |k, ()| reader(k)).await
}
/// Returns `true` if the [`HashSet`] contains the specified key.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(!hashset.contains(&1));
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.contains(&1));
/// ```
#[inline]
pub fn contains<Q>(&self, key: &Q) -> bool
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.read(key, |_| ()).is_some()
}
/// Returns `true` if the [`HashSet`] contains the specified key.
///
/// It is an asynchronous method returning an `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// let future_contains = hashset.contains_async(&1);
/// ```
#[inline]
pub async fn contains_async<Q>(&self, key: &Q) -> bool
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.contains_async(key).await
}
/// Scans all the keys.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another thread.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<usize> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.insert(2).is_ok());
///
/// let mut sum = 0;
/// hashset.scan(|k| { sum += *k; });
/// assert_eq!(sum, 3);
/// ```
#[inline]
pub fn scan<F: FnMut(&K)>(&self, mut scanner: F) {
self.map.scan(|k, ()| scanner(k));
}
/// Scans all the keys.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another task.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<usize> = HashSet::default();
///
/// let future_insert = hashset.insert_async(1);
/// let future_scan = hashset.scan_async(|k| println!("{k}"));
/// ```
#[inline]
pub async fn scan_async<F: FnMut(&K)>(&self, mut scanner: F) {
self.map.scan_async(|k, ()| scanner(k)).await;
}
/// Searches for any key that satisfies the given predicate.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another task.
///
/// Returns `true` if a key satisfying the predicate is found.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.insert(2).is_ok());
/// assert!(hashset.insert(3).is_ok());
///
/// assert!(hashset.any(|k| *k == 1));
/// assert!(!hashset.any(|k| *k == 4));
/// ```
#[inline]
pub fn any<P: FnMut(&K) -> bool>(&self, mut pred: P) -> bool {
self.map.any(|k, ()| pred(k))
}
/// Searches for any key that satisfies the given predicate.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another task.
///
/// It is an asynchronous method returning an `impl Future` for the caller to await.
///
/// Returns `true` if a key satisfying the predicate is found.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// let future_insert = hashset.insert(1);
/// let future_any = hashset.any_async(|k| *k == 1);
/// ```
#[inline]
pub async fn any_async<P: FnMut(&K) -> bool>(&self, mut pred: P) -> bool {
self.map.any_async(|k, ()| pred(k)).await
}
/// Retains keys that satisfy the given predicate.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another thread.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert!(hashset.insert(2).is_ok());
/// assert!(hashset.insert(3).is_ok());
///
/// hashset.retain(|k| *k == 1);
///
/// assert!(hashset.contains(&1));
/// assert!(!hashset.contains(&2));
/// assert!(!hashset.contains(&3));
/// ```
#[inline]
pub fn retain<F: FnMut(&K) -> bool>(&self, mut filter: F) {
self.map.retain(|k, ()| filter(k));
}
/// Retains keys that satisfy the given predicate.
///
/// Keys that have existed since the invocation of the method are guaranteed to be visited if
/// they are not removed, however the same key can be visited more than once if the [`HashSet`]
/// gets resized by another task.
///
/// It is an asynchronous method returning an `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// let future_insert = hashset.insert_async(1);
/// let future_retain = hashset.retain_async(|k| *k == 1);
/// ```
#[inline]
pub async fn retain_async<F: FnMut(&K) -> bool>(&self, mut filter: F) {
self.map.retain_async(|k, ()| filter(k)).await;
}
/// Clears the [`HashSet`] by removing all keys.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// hashset.clear();
///
/// assert!(!hashset.contains(&1));
/// ```
#[inline]
pub fn clear(&self) {
self.map.clear();
}
/// Clears the [`HashSet`] by removing all keys.
///
/// It is an asynchronous method returning an `impl Future` for the caller to await.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// let future_insert = hashset.insert_async(1);
/// let future_clear = hashset.clear_async();
/// ```
#[inline]
pub async fn clear_async(&self) {
self.map.clear_async().await;
}
/// Returns the number of entries in the [`HashSet`].
///
/// It reads the entire metadata area of the bucket array to calculate the number of valid
/// entries, making its time complexity `O(N)`. Furthermore, it may overcount entries if an old
/// bucket array has yet to be dropped.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.insert(1).is_ok());
/// assert_eq!(hashset.len(), 1);
/// ```
#[inline]
pub fn len(&self) -> usize {
self.map.len()
}
/// Returns `true` if the [`HashSet`] is empty.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert!(hashset.is_empty());
/// assert!(hashset.insert(1).is_ok());
/// assert!(!hashset.is_empty());
/// ```
#[inline]
pub fn is_empty(&self) -> bool {
self.map.is_empty()
}
/// Returns the capacity of the [`HashSet`].
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset_default: HashSet<u64> = HashSet::default();
/// assert_eq!(hashset_default.capacity(), 0);
///
/// assert!(hashset_default.insert(1).is_ok());
/// assert_eq!(hashset_default.capacity(), 64);
///
/// let hashset: HashSet<u64> = HashSet::with_capacity(1000);
/// assert_eq!(hashset.capacity(), 1024);
/// ```
#[inline]
pub fn capacity(&self) -> usize {
self.map.capacity()
}
/// Returns the current capacity range of the [`HashSet`].
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// assert_eq!(hashset.capacity_range(), 0..=(1_usize << (usize::BITS - 1)));
///
/// let reserved = hashset.reserve(1000);
/// assert_eq!(hashset.capacity_range(), 1000..=(1_usize << (usize::BITS - 1)));
/// ```
#[inline]
pub fn capacity_range(&self) -> RangeInclusive<usize> {
self.map.capacity_range()
}
/// Returns the index of the bucket that may contain the key.
///
/// The method returns the index of the bucket associated with the key. The number of buckets
/// can be calculated by dividing `32` into the capacity.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::with_capacity(1024);
///
/// let bucket_index = hashset.bucket_index(&11);
/// assert!(bucket_index < hashset.capacity() / 32);
/// ```
#[inline]
pub fn bucket_index<Q>(&self, key: &Q) -> usize
where
Q: Equivalent<K> + Hash + ?Sized,
{
self.map.bucket_index(key)
}
}
impl<K, H> Clone for HashSet<K, H>
where
K: Clone + Eq + Hash,
H: BuildHasher + Clone,
{
#[inline]
fn clone(&self) -> Self {
Self {
map: self.map.clone(),
}
}
}
impl<K, H> Debug for HashSet<K, H>
where
K: Debug + Eq + Hash,
H: BuildHasher,
{
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut d = f.debug_set();
self.scan(|k| {
d.entry(k);
});
d.finish()
}
}
impl<K: Eq + Hash> HashSet<K, RandomState> {
/// Creates an empty default [`HashSet`].
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::new();
///
/// let result = hashset.capacity();
/// assert_eq!(result, 0);
/// ```
#[inline]
#[must_use]
pub fn new() -> Self {
Self::default()
}
/// Creates an empty [`HashSet`] with the specified capacity.
///
/// The actual capacity is equal to or greater than the specified capacity.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::with_capacity(1000);
///
/// let result = hashset.capacity();
/// assert_eq!(result, 1024);
/// ```
#[inline]
#[must_use]
pub fn with_capacity(capacity: usize) -> Self {
Self {
map: HashMap::with_capacity(capacity),
}
}
}
impl<K, H> Default for HashSet<K, H>
where
H: BuildHasher + Default,
{
/// Creates an empty default [`HashSet`].
///
/// The default capacity is `64`.
///
/// # Examples
///
/// ```
/// use scc::HashSet;
///
/// let hashset: HashSet<u64> = HashSet::default();
///
/// let result = hashset.capacity();
/// assert_eq!(result, 0);
/// ```
#[inline]
fn default() -> Self {
Self {
map: HashMap::default(),
}
}
}
impl<K, H> PartialEq for HashSet<K, H>
where
K: Eq + Hash,
H: BuildHasher,
{
/// Compares two [`HashSet`] instances.
///
/// ## Locking behavior
///
/// Shared locks on buckets are acquired when comparing two instances of [`HashSet`], therefore
/// it may lead to a deadlock if the instances are being modified by another thread.
#[inline]
fn eq(&self, other: &Self) -> bool {
if !self.any(|k| !other.contains(k)) {
return !other.any(|k| !self.contains(k));
}
false
}
}