Enum SmallHashMap 

pub enum SmallHashMap<K: Eq + Hash, V, const N: usize, const M: usize> {
    Small(SmallVec<[(K, V); N]>),
    Large(HashMap<K, V>),
}

A hash map optimized for small sizes, with a small size optimization for up to N entries and then a vector for up to M and then finally falling back to a real hash map after M.

The inline and heap based vectors use linear scans, which is faster than hashing as long as the map is small.

Variants

Small(SmallVec<[(K, V); N]>)

Large(HashMap<K, V>)

Implementations

impl<K: Eq + Hash, V, const N: usize, const M: usize> SmallHashMap<K, V, N, M>

pub fn new() -> Self

pub fn insert(&mut self, key: K, value: V) -> Option<V>

Inserts the association key -> value into the map, returning the previous value for key, if any.

pub fn get_or_insert(&mut self, key: K, or_insert: impl FnOnce() -> V) -> &mut V

Returns either the existing value for key or inserts into key using or_insert.

pub fn remove(&mut self, key: &K) -> Option<V>

pub fn clear(&mut self)

Clears all entries from the map.

pub fn len(&self) -> usize

Returns the number of entries in the map.

pub fn is_empty(&self) -> bool

Returns whether the map is empty.

pub fn iter(&self) -> impl ExactSizeIterator<Item = (&K, &V)>

Returns an iterator over all the key-value pairs in the map.

pub fn keys(&self) -> impl ExactSizeIterator<Item = &K>

Returns an iterator over all the keys in the map.

pub fn values(&self) -> impl ExactSizeIterator<Item = &V>

Returns an iterator over all the values in the map.

pub fn contains_key(&self, key: &K) -> bool

Returns whether key is in the map.

pub fn get(&self, key: &K) -> Option<&V>

Returns the value for key, if any.

pub fn get_mut(&mut self, key: &K) -> Option<&mut V>

Returns the value for key, mutably, if any.

Trait Implementations

impl<K: Clone + Eq + Hash, V: Clone, const N: usize, const M: usize> Clone for SmallHashMap<K, V, N, M>

fn clone(&self) -> SmallHashMap<K, V, N, M>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K: Debug + Eq + Hash, V: Debug, const N: usize, const M: usize> Debug for SmallHashMap<K, V, N, M>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K: Eq + Hash, V, const N: usize, const M: usize> Default for SmallHashMap<K, V, N, M>

fn default() -> Self

Returns the “default value” for a type.

impl<K: Eq + Hash, V, const N: usize, const M: usize> Extend<(K, V)> for SmallHashMap<K, V, N, M>

fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<K: PartialEq + Eq + Hash, V: PartialEq, const N: usize, const M: usize> PartialEq for SmallHashMap<K, V, N, M>

fn eq(&self, other: &SmallHashMap<K, V, N, M>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<K: Eq + Eq + Hash, V: Eq, const N: usize, const M: usize> Eq for SmallHashMap<K, V, N, M>

impl<K: Eq + Hash, V, const N: usize, const M: usize> StructuralPartialEq for SmallHashMap<K, V, N, M>