Struct IndexMap

pub struct IndexMap<K, V, S, const N: usize> { /* private fields */ }

Fixed capacity IndexMap

Note that you cannot use IndexMap directly, since it is generic around the hashing algorithm in use. Pick a concrete instantiation like FnvIndexMap instead or create your own.

Note that the capacity of the IndexMap must be a power of 2.

Examples

Since IndexMap cannot be used directly, we’re using its FnvIndexMap instantiation for this example.

use heapless::FnvIndexMap;

// A hash map with a capacity of 16 key-value pairs allocated on the stack
let mut book_reviews = FnvIndexMap::<_, _, 16>::new();

// review some books.
book_reviews.insert("Adventures of Huckleberry Finn",    "My favorite book.").unwrap();
book_reviews.insert("Grimms' Fairy Tales",               "Masterpiece.").unwrap();
book_reviews.insert("Pride and Prejudice",               "Very enjoyable.").unwrap();
book_reviews.insert("The Adventures of Sherlock Holmes", "Eye lyked it alot.").unwrap();

// check for a specific one.
if !book_reviews.contains_key("Les Misérables") {
    println!("We've got {} reviews, but Les Misérables ain't one.",
             book_reviews.len());
}

// oops, this review has a lot of spelling mistakes, let's delete it.
book_reviews.remove("The Adventures of Sherlock Holmes");

// look up the values associated with some keys.
let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
for book in &to_find {
    match book_reviews.get(book) {
        Some(review) => println!("{}: {}", book, review),
        None => println!("{} is unreviewed.", book)
    }
}

// iterate over everything.
for (book, review) in &book_reviews {
    println!("{}: \"{}\"", book, review);
}

Implementations

impl<K, V, S, const N: usize> IndexMap<K, V, BuildHasherDefault<S>, N>

pub const fn new() -> Self

Creates an empty IndexMap.

impl<K, V, S, const N: usize> IndexMap<K, V, S, N>

pub fn capacity(&self) -> usize

Returns the number of elements the map can hold

pub fn keys(&self) -> Keys<'_, K, V>

Return an iterator over the keys of the map, in insertion order

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert("a", 1).unwrap();
map.insert("b", 2).unwrap();
map.insert("c", 3).unwrap();

for key in map.keys() {
    println!("{}", key);
}

pub fn values(&self) -> Values<'_, K, V>

Return an iterator over the values of the map, in insertion order

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert("a", 1).unwrap();
map.insert("b", 2).unwrap();
map.insert("c", 3).unwrap();

for val in map.values() {
    println!("{}", val);
}

pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>

Return an iterator over mutable references to the the values of the map, in insertion order

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert("a", 1).unwrap();
map.insert("b", 2).unwrap();
map.insert("c", 3).unwrap();

for val in map.values_mut() {
    *val += 10;
}

for val in map.values() {
    println!("{}", val);
}

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

Return an iterator over the key-value pairs of the map, in insertion order

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert("a", 1).unwrap();
map.insert("b", 2).unwrap();
map.insert("c", 3).unwrap();

for (key, val) in map.iter() {
    println!("key: {} val: {}", key, val);
}

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

Return an iterator over the key-value pairs of the map, in insertion order

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert("a", 1).unwrap();
map.insert("b", 2).unwrap();
map.insert("c", 3).unwrap();

for (_, val) in map.iter_mut() {
    *val = 2;
}

for (key, val) in &map {
    println!("key: {} val: {}", key, val);
}

pub fn first(&self) -> Option<(&K, &V)>

Get the first key-value pair

Computes in O(1) time

pub fn first_mut(&mut self) -> Option<(&K, &mut V)>

Get the first key-value pair, with mutable access to the value

Computes in O(1) time

pub fn last(&self) -> Option<(&K, &V)>

Get the last key-value pair

Computes in O(1) time

pub fn last_mut(&mut self) -> Option<(&K, &mut V)>

Get the last key-value pair, with mutable access to the value

Computes in O(1) time

pub fn len(&self) -> usize

Return the number of key-value pairs in the map.

Computes in O(1) time.

use heapless::FnvIndexMap;

let mut a = FnvIndexMap::<_, _, 16>::new();
assert_eq!(a.len(), 0);
a.insert(1, "a").unwrap();
assert_eq!(a.len(), 1);

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Computes in O(1) time.

use heapless::FnvIndexMap;

let mut a = FnvIndexMap::<_, _, 16>::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());

pub fn clear(&mut self)

Remove all key-value pairs in the map, while preserving its capacity.

Computes in O(n) time.

use heapless::FnvIndexMap;

let mut a = FnvIndexMap::<_, _, 16>::new();
a.insert(1, "a");
a.clear();
assert!(a.is_empty());

impl<K, V, S, const N: usize> IndexMap<K, V, S, N>

where K: Eq + Hash, S: BuildHasher,

pub fn entry(&mut self, key: K) -> Entry<'_, K, V, N>

Returns an entry for the corresponding key

use heapless::FnvIndexMap;
use heapless::Entry;
let mut map = FnvIndexMap::<_, _, 16>::new();
if let Entry::Vacant(v) = map.entry("a") {
    v.insert(1).unwrap();
}
if let Entry::Occupied(mut o) = map.entry("a") {
    println!("found {}", *o.get()); // Prints 1
    o.insert(2);
}
// Prints 2
println!("val: {}", *map.get("a").unwrap());

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

where K: Borrow<Q>, Q: ?Sized + Hash + Eq,

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Computes in O(1) time (average).

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 16>::new();
map.insert(1, "a").unwrap();
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

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

where K: Borrow<Q>, Q: ?Sized + Eq + Hash,

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Computes in O(1) time (average).

Examples

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 8>::new();
map.insert(1, "a").unwrap();
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

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

where K: Borrow<Q>, Q: ?Sized + Hash + Eq,

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Computes in O(1) time (average).

Examples

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 8>::new();
map.insert(1, "a").unwrap();
if let Some(x) = map.get_mut(&1) {
    *x = "b";
}
assert_eq!(map[&1], "b");

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

Inserts a key-value pair into the map.

If an equivalent key already exists in the map: the key remains and retains in its place in the order, its corresponding value is updated with value and the older value is returned inside Some(_).

If no equivalent key existed in the map: the new key-value pair is inserted, last in order, and None is returned.

Computes in O(1) time (average).

See also entry if you you want to insert or modify or if you need to get the index of the corresponding key-value pair.

Examples

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 8>::new();
assert_eq!(map.insert(37, "a"), Ok(None));
assert_eq!(map.is_empty(), false);

map.insert(37, "b");
assert_eq!(map.insert(37, "c"), Ok(Some("b")));
assert_eq!(map[&37], "c");

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

where K: Borrow<Q>, Q: ?Sized + Hash + Eq,

Same as swap_remove

Computes in O(1) time (average).

Examples

use heapless::FnvIndexMap;

let mut map = FnvIndexMap::<_, _, 8>::new();
map.insert(1, "a").unwrap();
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);

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

where K: Borrow<Q>, Q: ?Sized + Hash + Eq,

Remove the key-value pair equivalent to key and return its value.

Like Vec::swap_remove, the pair is removed by swapping it with the last element of the map and popping it off. This perturbs the postion of what used to be the last element!

Return None if key is not in map.

Computes in O(1) time (average).

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&K, &mut V) -> bool,

Retains only the elements specified by the predicate.

In other words, remove all pairs (k, v) for which f(&k, &mut v) returns false.

Trait Implementations

impl<K, V, S, const N: usize> Clone for IndexMap<K, V, S, N>

where K: Clone, V: Clone, S: Clone,

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<K, V, S, const N: usize> Debug for IndexMap<K, V, S, N>

where K: Debug, V: Debug,

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

Formats the value using the given formatter.

impl<K, V, S, const N: usize> Default for IndexMap<K, V, S, N>

where S: Default,

fn default() -> Self

Returns the “default value” for a type.

impl<'a, K, V, S, const N: usize> Extend<(&'a K, &'a V)> for IndexMap<K, V, S, N>

where K: Eq + Hash + Copy, V: Copy, S: BuildHasher,

fn extend<I>(&mut self, iterable: I)

where I: IntoIterator<Item = (&'a K, &'a V)>,

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, S, const N: usize> Extend<(K, V)> for IndexMap<K, V, S, N>

where K: Eq + Hash, S: BuildHasher,

fn extend<I>(&mut self, iterable: I)

where I: IntoIterator<Item = (K, V)>,

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, S, const N: usize> FromIterator<(K, V)> for IndexMap<K, V, S, N>

where K: Eq + Hash, S: BuildHasher + Default,

fn from_iter<I>(iterable: I) -> Self

where I: IntoIterator<Item = (K, V)>,

Creates a value from an iterator.

impl<'a, K, Q, V, S, const N: usize> Index<&'a Q> for IndexMap<K, V, S, N>

where K: Eq + Hash + Borrow<Q>, Q: ?Sized + Eq + Hash, S: BuildHasher,

type Output = V

The returned type after indexing.

fn index(&self, key: &Q) -> &V

Performs the indexing (container[index]) operation.

impl<'a, K, Q, V, S, const N: usize> IndexMut<&'a Q> for IndexMap<K, V, S, N>

where K: Eq + Hash + Borrow<Q>, Q: ?Sized + Eq + Hash, S: BuildHasher,

fn index_mut(&mut self, key: &Q) -> &mut V

Performs the mutable indexing (container[index]) operation.

impl<'a, K, V, S, const N: usize> IntoIterator for &'a IndexMap<K, V, S, N>

type Item = (&'a K, &'a 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, S, const N: usize> IntoIterator for &'a mut IndexMap<K, V, S, N>

type Item = (&'a K, &'a mut 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, S, const N: usize> IntoIterator for IndexMap<K, V, S, N>

type Item = (K, V)

The type of the elements being iterated over.

type IntoIter = IntoIter<K, V, N>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<K, V, S, S2, const N: usize, const N2: usize> PartialEq<IndexMap<K, V, S2, N2>> for IndexMap<K, V, S, N>

where K: Eq + Hash, V: Eq, S: BuildHasher, S2: BuildHasher,

fn eq(&self, other: &IndexMap<K, V, S2, N2>) -> 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, V, S, const N: usize> Eq for IndexMap<K, V, S, N>

where K: Eq + Hash, V: Eq, S: BuildHasher,