Struct VecMap 

pub struct VecMap<K, V> { /* private fields */ }

A Vec-backed map that provides HashMap-like lookup by key.

Duplicates

Duplicates are tolerated: VecMap::insert always appends, and VecMap::get/VecMap::get_mut return the last matching entry so that later writes shadow earlier ones. This optimizes for fast insertion and construction (that might happen on the client’s application hot path), avoiding a linear scan on each insert, or a potential full re-hashing with a hashmap. Additionally, while overriding a metric or a meta definitively happens, it’s assumed to be rare enough so such that the size penalty of duplication is expected to be reasonable.

Important: note that only VecMap::get and VecMap::get_mut are duplicate-aware, so to speak. VecMap::len, VecMap::iter, and others just delegates to the underlying Vec, and won’t deduplicate.

Explicit deduplication is currently being done on-demand by VecMap::dedup. An internal flag is used to avoid undue deduplication (see VecMap::dedup). VecMap is automatically deduped before serialization.

In the future, we could trigger deduplication on other events, for example at insertion if the size is bigger than a threshold (and we haven’t deduped for x operations).

Ordering

As this is a map, iteration order is not defined nor guaranteed. In practice, iteration follows insertion order, but Self::dedup will reverse the underlying vector.

Implementations

impl<K, V> VecMap<K, V>

pub fn new() -> Self

pub fn with_capacity(capacity: usize) -> Self

pub fn insert(&mut self, key: K, value: V)

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

where K: Borrow<Q>, Q: ?Sized + PartialEq,

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

where K: Borrow<Q>, Q: ?Sized + PartialEq,

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

where K: Borrow<Q>, Q: ?Sized + PartialEq,

pub fn remove_slow<Q>(&mut self, key: &Q)

where K: Borrow<Q>, Q: ?Sized + PartialEq,

Remove all entries matching this key from the map. This method uses Vec::retain, and is thus potentially costly (like any removal in a vector-like datastructure).

pub fn iter(&self) -> Iter<'_, (K, V)>

Iterate over the element, including duplicate entries.

pub fn iter_mut(&mut self) -> IterMut<'_, (K, V)>

Iterate mutably over the elements, including duplicate entries.

pub fn len(&self) -> usize

Return the length of the underlying vector, thus including duplicate entries.

pub fn is_empty(&self) -> bool

pub fn is_deduped(&self) -> bool

Return true if the map hasn’t been extended since the last call to Self::dedup, guaranteeing that the underlying vector doesn’t have any duplicate key.

If is_deduped returns false, the map may have duplicate keys.

impl<K: Hash + Eq + Clone, V> VecMap<K, V>

pub fn dedup(&mut self)

Remove entries with a duplicate key, only keeping the last one. After this, a flag is set internally, such that as long as the map isn’t extended or mutably iterated, the next Self::dedup doesn’t perform the work again.

Trait Implementations

impl<K: Clone, V: Clone> Clone for VecMap<K, V>

fn clone(&self) -> VecMap<K, V>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<K: Debug, V: Debug> Debug for VecMap<K, V>

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

Formats the value using the given formatter.

impl<K, V> Default for VecMap<K, V>

fn default() -> Self

Returns the “default value” for a type.

impl<K, V> Extend<(K, V)> for VecMap<K, V>

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

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, V> From<Vec<(K, V)>> for VecMap<K, V>

fn from(data: Vec<(K, V)>) -> Self

Converts to this type from the input type.

impl<K, V> From<VecMap<K, V>> for Vec<(K, V)>

fn from(value: VecMap<K, V>) -> Self

Converts to this type from the input type.

impl<K, V> FromIterator<(K, V)> for VecMap<K, V>

fn from_iter<I: IntoIterator<Item = (K, V)>>(iter: I) -> Self

Creates a value from an iterator.

impl<'a, K, V> IntoIterator for &'a VecMap<K, V>

type Item = &'a (K, V)

The type of the elements being iterated over.

type IntoIter = Iter<'a, (K, V)>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, K, V> IntoIterator for &'a mut VecMap<K, V>

type Item = &'a mut (K, V)

The type of the elements being iterated over.

type IntoIter = IterMut<'a, (K, V)>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<K, V> IntoIterator for VecMap<K, V>

type Item = (K, V)

The type of the elements being iterated over.

type IntoIter = IntoIter<(K, V)>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<K: PartialEq, V: PartialEq> PartialEq for VecMap<K, V>

fn eq(&self, other: &VecMap<K, V>) -> 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: Serialize + Eq + Hash, V: Serialize> Serialize for VecMap<K, V>

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl<K, V> StructuralPartialEq for VecMap<K, V>