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Add an implementation of HashSet

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Gwilym Inzani 2024-09-25 15:18:25 +01:00
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441
agb-hashmap/src/hash_set.rs Normal file
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@ -0,0 +1,441 @@
use crate::{Allocator, ClonableAllocator, Global};
use core::{borrow::Borrow, fmt::Debug, hash::Hash};
use super::HashMap;
/// A `HashSet` is implemented as a [`HashMap`] where the value is `()`.
///
/// As with the [`HashMap`] type, a `HashSet` requires that the elements implement the
/// [`Eq`] and [`Hash`] traits, although this is frequently achieved by using
/// `#[derive(PartialEq, Eq, Hash)]`. If you implement these yourself, it is important
/// that the following property holds:
///
/// It is a logic error for the key to be modified in such a way that the key's hash, as
/// determined by the [`Hash`] trait, or its equality as determined by the [`Eq`] trait,
/// changes while it is in the map. The behaviour for such a logic error is not specified,
/// but will not result in undefined behaviour. This could include panics, incorrect results,
/// aborts, memory leaks and non-termination.
///
/// The API surface provided is incredibly similar to the
/// [`std::collections::HashSet`](https://doc.rust-lang.org/std/collections/struct.HashMap.html)
/// implementation with fewer guarantees, and better optimised for the `GameBoy Advance`.
///
/// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
/// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
///
/// # Example
///
/// ```
/// use agb_hashmap::HashSet;
///
/// // Type inference lets you omit the type signature (which would be HashSet<String> in this example)
/// let mut games = HashSet::new();
///
/// // Add some games
/// games.insert("Pokemon Emerald".to_string());
/// games.insert("Golden Sun".to_string());
/// games.insert("Super Dodge Ball Advance".to_string());
///
/// // Check for a specific game
/// if !games.contains("Legend of Zelda: The Minish Cap") {
/// println!("We've got {} games, but The Minish Cap ain't one", games.len());
/// }
///
/// // Remove a game
/// games.remove("Golden Sun");
///
/// // Iterate over everything
/// for game in &games {
/// println!("{game}");
/// }
/// ```
#[derive(Clone)]
pub struct HashSet<K, ALLOCATOR: Allocator = Global> {
map: HashMap<K, (), ALLOCATOR>,
}
impl<K> HashSet<K> {
/// Creates a `HashSet`
#[must_use]
pub fn new() -> Self {
Self::new_in(Global)
}
/// Creates an empty `HashSet` with specified internal size. The size must be a power of 2
#[must_use]
pub fn with_size(size: usize) -> Self {
Self::with_size_in(size, Global)
}
/// Creates an empty `HashSet` which can hold at least `capacity` elements before resizing. The actual
/// internal size may be larger as it must be a power of 2
#[must_use]
pub fn with_capacity(capacity: usize) -> Self {
Self::with_capacity_in(capacity, Global)
}
}
impl<K, ALLOCATOR: ClonableAllocator> HashSet<K, ALLOCATOR> {
/// Creates an empty `HashSet` with specified internal size using the specified allocator.
/// The size must be a power of 2
#[must_use]
pub fn with_size_in(size: usize, alloc: ALLOCATOR) -> Self {
Self {
map: HashMap::with_size_in(size, alloc),
}
}
/// Creates a `HashSet` with a specified allocator
#[must_use]
pub fn new_in(alloc: ALLOCATOR) -> Self {
Self::with_size_in(16, alloc)
}
/// Creates an empty `HashSet` which can hold at least `capacity` elements before resizing. The actual
/// internal size may be larger as it must be a power of 2
///
/// # Panics
///
/// Panics if capacity is larger than 2^32 * .85
#[must_use]
pub fn with_capacity_in(capacity: usize, alloc: ALLOCATOR) -> Self {
Self {
map: HashMap::with_capacity_in(capacity, alloc),
}
}
/// Returns a reference to the underlying allocator
pub fn allocator(&self) -> &ALLOCATOR {
self.map.allocator()
}
/// Returns the number of elements in the set
#[must_use]
pub fn len(&self) -> usize {
self.map.len()
}
/// Returns whether or not the set is empty
#[must_use]
pub fn is_empty(&self) -> bool {
self.map.is_empty()
}
/// Returns the number of elements the set can hold without resizing
#[must_use]
pub fn capacity(&self) -> usize {
self.map.capacity()
}
/// Removes all elements from the set
pub fn clear(&mut self) {
self.map.clear();
}
/// An iterator visiting all the values in the set
pub fn iter(&self) -> impl Iterator<Item = &'_ K> {
self.map.keys()
}
/// Retains only the elements specified by the predicate `f`
pub fn retain<F>(&mut self, mut f: F)
where
F: FnMut(&K) -> bool,
{
self.map.retain(|k, _| f(k));
}
}
impl<K> Default for HashSet<K> {
fn default() -> Self {
Self::new()
}
}
impl<K, ALLOCATOR: ClonableAllocator> HashSet<K, ALLOCATOR>
where
K: Eq + Hash,
{
/// Inserts a value into the set. This does not replace the value if it already existed.
///
/// Returns whether the value was newly inserted, that is:
///
/// * If the set did not previously contain this value, `true` is returned
/// * If the set already contained this value, `false` is returned.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let mut set = HashSet::new();
/// assert_eq!(set.insert(2), true);
/// assert_eq!(set.insert(2), false);
/// assert_eq!(set.len(), 1);
/// ```
pub fn insert(&mut self, value: K) -> bool {
self.map.insert(value, ()).is_none()
}
/// Removes a value from the set. Returns whether the value was present in the set.
///
/// # Examples
/// ```
/// use agb_hashmap::HashSet;
///
/// let mut set = HashSet::new();
/// set.insert(2);
///
/// assert_eq!(set.remove(&2), true);
/// assert_eq!(set.remove(&2), false);
/// assert!(set.is_empty());
/// ```
pub fn remove<Q>(&mut self, value: &Q) -> bool
where
K: Borrow<Q>,
Q: Hash + Eq + ?Sized,
{
self.map.remove(value).is_some()
}
/// Returns `true` if the set contains the value `value`.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let set = HashSet::from([1, 2, 3]);
/// assert_eq!(set.contains(&1), true);
/// assert_eq!(set.contains(&4), false);
/// ```
pub fn contains<Q>(&self, value: &Q) -> bool
where
K: Borrow<Q>,
Q: Hash + Eq + ?Sized,
{
self.map.contains_key(value)
}
/// Visits the values reperesting the difference i.e. the values that are in `self` but not in `other`.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// // Can be seen as `a - b`
/// let diff: HashSet<_> = a.difference(&b).collect();
/// assert_eq!(diff, HashSet::from([&1]));
///
/// // Difference is not symmetric. `b - a` means something different
/// let diff: HashSet<_> = b.difference(&a).collect();
/// assert_eq!(diff, HashSet::from([&4]));
/// ``````
pub fn difference<'a>(
&'a self,
other: &'a HashSet<K, ALLOCATOR>,
) -> impl Iterator<Item = &'a K> {
self.iter().filter(|k| !other.contains(k))
}
/// Visits the values which are in `self` or `other` but not both.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let diff1: HashSet<_> = a.symmetric_difference(&b).collect();
/// let diff2: HashSet<_> = b.symmetric_difference(&a).collect();
///
/// assert_eq!(diff1, diff2);
/// assert_eq!(diff1, HashSet::from([&1, &4]));
/// ```
pub fn symmetric_difference<'a>(
&'a self,
other: &'a HashSet<K, ALLOCATOR>,
) -> impl Iterator<Item = &'a K> {
self.iter()
.filter(|k| !other.contains(k))
.chain(other.iter().filter(|k| !self.contains(k)))
}
/// Visits the values in the intersection of `self` and `other`.
///
/// When an equal element is present in `self` and `other`, then the resulting intersection may
/// yield references to one or the other. This can be relevant if `K` contains fields which are not
/// covered by the `Eq` implementation.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let intersection: HashSet<_> = a.intersection(&b).collect();
/// assert_eq!(intersection, HashSet::from([&2, &3]));
/// ```
pub fn intersection<'a>(
&'a self,
other: &'a HashSet<K, ALLOCATOR>,
) -> impl Iterator<Item = &'a K> {
let (smaller, larger) = if self.len() < other.len() {
(self, other)
} else {
(other, self)
};
smaller.iter().filter(|k| larger.contains(k))
}
/// Visits the values in self and other without duplicates.
///
/// When an equal element is present in `self` and `other`, then the resulting union may
/// yield references to one or the other. This can be relevant if `K` contains fields which are not
/// covered by the `Eq` implementation.
///
/// # Examples
///
/// ```
/// use agb_hashmap::HashSet;
///
/// let a = HashSet::from([1, 2, 3]);
/// let b = HashSet::from([4, 2, 3, 4]);
///
/// let union: Vec<_> = a.union(&b).collect();
/// assert_eq!(union.len(), 4);
/// assert_eq!(HashSet::from_iter(union), HashSet::from([&1, &2, &3, &4]));
/// ```
pub fn union<'a>(&'a self, other: &'a HashSet<K, ALLOCATOR>) -> impl Iterator<Item = &'a K> {
let (smaller, larger) = if self.len() < other.len() {
(self, other)
} else {
(other, self)
};
larger.iter().chain(smaller.difference(self))
}
}
impl<K, ALLOCATOR: ClonableAllocator> IntoIterator for HashSet<K, ALLOCATOR> {
type Item = K;
type IntoIter = IterOwned<K, ALLOCATOR>;
fn into_iter(self) -> Self::IntoIter {
IterOwned {
map_iter: self.map.into_iter(),
}
}
}
/// An iterator over the entries of a [`HashSet`].
///
/// This struct is created using the `into_iter()` method on [`HashSet`] as part of its implementation
/// of the `IntoIterator` trait.
pub struct IterOwned<K, ALLOCATOR: ClonableAllocator> {
map_iter: super::IterOwned<K, (), ALLOCATOR>,
}
impl<K, ALLOCATOR: ClonableAllocator> Iterator for IterOwned<K, ALLOCATOR> {
type Item = K;
fn next(&mut self) -> Option<Self::Item> {
self.map_iter.next().map(|(k, _)| k)
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.map_iter.size_hint()
}
}
impl<K, ALLOCATOR: ClonableAllocator> ExactSizeIterator for IterOwned<K, ALLOCATOR> {}
impl<'a, K, ALLOCATOR: ClonableAllocator> IntoIterator for &'a HashSet<K, ALLOCATOR> {
type Item = &'a K;
type IntoIter = Iter<'a, K, ALLOCATOR>;
fn into_iter(self) -> Self::IntoIter {
Iter {
map_iter: (&self.map).into_iter(),
}
}
}
pub struct Iter<'a, K, ALLOCATOR: ClonableAllocator> {
map_iter: super::Iter<'a, K, (), ALLOCATOR>,
}
impl<'a, K, ALLOCATOR: ClonableAllocator> Iterator for Iter<'a, K, ALLOCATOR> {
type Item = &'a K;
fn next(&mut self) -> Option<Self::Item> {
self.map_iter.next().map(|(k, _)| k)
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.map_iter.size_hint()
}
}
impl<'a, K, ALLOCATOR: ClonableAllocator> ExactSizeIterator for Iter<'a, K, ALLOCATOR> {}
impl<K> FromIterator<K> for HashSet<K>
where
K: Eq + Hash,
{
fn from_iter<T: IntoIterator<Item = K>>(iter: T) -> Self {
let mut set = HashSet::new();
set.extend(iter);
set
}
}
impl<K> Extend<K> for HashSet<K>
where
K: Eq + Hash,
{
fn extend<T: IntoIterator<Item = K>>(&mut self, iter: T) {
for k in iter {
self.insert(k);
}
}
}
impl<K, ALLOCATOR: ClonableAllocator> PartialEq for HashSet<K, ALLOCATOR>
where
K: Eq + Hash,
{
fn eq(&self, other: &Self) -> bool {
self.map == other.map
}
}
impl<K, ALLOCATOR: ClonableAllocator> Eq for HashSet<K, ALLOCATOR> where K: Eq + Hash {}
impl<K, ALLOCATOR: ClonableAllocator> Debug for HashSet<K, ALLOCATOR>
where
K: Debug,
{
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_set().entries(self.iter()).finish()
}
}
impl<K, const N: usize> From<[K; N]> for HashSet<K>
where
K: Eq + Hash,
{
fn from(value: [K; N]) -> Self {
HashSet::from_iter(value)
}
}

7
agb-hashmap/src/lib.rs
View file

@ -54,12 +54,15 @@ use core::{
use rustc_hash::FxHasher;
mod hash_set;
mod node;
mod node_storage;
use node::Node;
use node_storage::NodeStorage;
pub use hash_set::HashSet;
// # Robin Hood Hash Tables
//
// The problem with regular hash tables where failing to find a slot for a specific
@ -525,6 +528,8 @@ impl<'a, K, V, ALLOCATOR: ClonableAllocator> Iterator for Iter<'a, K, V, ALLOCAT
}
}
impl<'a, K, V, ALLOCATOR: ClonableAllocator> ExactSizeIterator for Iter<'a, K, V, ALLOCATOR> {}
impl<'a, K, V, ALLOCATOR: ClonableAllocator> IntoIterator for &'a HashMap<K, V, ALLOCATOR> {
type Item = (&'a K, &'a V);
type IntoIter = Iter<'a, K, V, ALLOCATOR>;
@ -575,6 +580,8 @@ impl<K, V, ALLOCATOR: ClonableAllocator> Iterator for IterOwned<K, V, ALLOCATOR>
}
}
impl<K, V, ALLOCATOR: ClonableAllocator> ExactSizeIterator for IterOwned<K, V, ALLOCATOR> {}
/// An iterator over entries of a [`HashMap`]
///
/// This struct is created using the `into_iter()` method on [`HashMap`] as part of its implementation