Enum halfbrown::HashMap

pub enum HashMap<K, V> where
    K: Eq + Hash,  {
    Map(HashBrown<K, V>),
    Vec(VecMap<K, V>),
    None,
}

Variants

Map(HashBrown<K, V>)Vec(VecMap<K, V>)None

Methods

impl<K, V> HashMap<K, V> where
    K: Eq + Hash, 

pub fn new() -> Self

Creates an empty HashMap.

The hash map is initially created with a capacity of 0, so it will not allocate until it is first inserted into.

Examples

use halfbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();

pub fn with_capacity(capacity: usize) -> Self

Creates an empty HashMap with the specified capacity.

The hash map will be able to hold at least capacity elements without reallocating. If capacity is 0, the hash map will not allocate.

Examples

use halfbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::with_capacity(10);

pub fn vec_with_capacity(capacity: usize) -> Self

Same as with capacity with the difference that it, despite of the requested size always returns a vector. This allows quicker generation when used in combination with insert_nocheck.

Examples

use halfbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::vec_with_capacity(128);
assert!(map.is_vec());

impl<K, V> HashMap<K, V> where
    K: Eq + Hash, 

pub fn capacity(&self) -> usize

Returns the number of elements the map can hold without reallocating.

This number is a lower bound; the HashMap<K, V> might be able to hold more, but is guaranteed to be able to hold at least this many.

Examples

use halfbrown::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert!(map.capacity() >= 100);

Important traits for Keys<'a, K, V>

impl<'a, K, V> Iterator for Keys<'a, K, V> type Item = &'a K;

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

An iterator visiting all keys in arbitrary order. The iterator element type is &'a K.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for Values<'a, K, V>

impl<'a, K, V> Iterator for Values<'a, K, V> type Item = &'a V;

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

An iterator visiting all values in arbitrary order. The iterator element type is &'a V.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for ValuesMut<'a, K, V>

impl<'a, K, V> Iterator for ValuesMut<'a, K, V> type Item = &'a mut V;

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

An iterator visiting all values mutably in arbitrary order. The iterator element type is &'a mut V.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();

map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

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

Important traits for Iter<'a, K, V>

impl<'a, K, V> Iterator for Iter<'a, K, V> type Item = (&'a K, &'a V);

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

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is (&'a K, &'a V).

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

Important traits for IterMut<'a, K, V>

impl<'a, K, V> Iterator for IterMut<'a, K, V> type Item = (&'a K, &'a mut V);

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

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is (&'a K, &'a mut V).

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

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

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

pub fn len(&self) -> usize

Returns the number of elements in the map.

Examples

use halfbrown::HashMap;

let mut a = HashMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Examples

use halfbrown::HashMap;

let mut a = HashMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());

Important traits for Drain<'a, K, V>

impl<'a, K, V> Iterator for Drain<'a, K, V> type Item = (K, V);

pub fn drain(&mut self) -> Drain<K, V>

Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.

Examples

use halfbrown::HashMap;

let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");

for (k, v) in a.drain().take(1) {
    assert!(k == 1 || k == 2);
    assert!(v == "a" || v == "b");
}

assert!(a.is_empty());

pub fn clear(&mut self)

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

Examples

use halfbrown::HashMap;

let mut a = HashMap::new();
a.insert(1, "a");
a.clear();
assert!(a.is_empty());

impl<K, V> HashMap<K, V> where
    K: Eq + Hash, 

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more elements to be inserted in the HashMap. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new allocation size overflows usize.

Examples

use halfbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();
map.reserve(10);

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use halfbrown::HashMap;

let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to_fit();
assert!(map.capacity() >= 2);

pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V> where
    K: Borrow<Q>,
    Q: 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.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool where
    K: Borrow<Q>,
    Q: Hash + Eq, 

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.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V> where
    K: Borrow<Q>,
    Q: 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.

Examples

use halfbrown::HashMap;

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

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

Inserts a key-value pair into the map.

If the map did not have this key present, None is returned.

If the map did have this key present, the value is updated, and the old value is returned. The key is not updated, though; this matters for types that can be == without being identical. See the module-level documentation for more.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
assert_eq!(map.insert(37, "a"), None);
assert_eq!(map.is_empty(), false);

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

pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V> where
    K: Borrow<Q>,
    Q: Hash + Eq, 

Removes a key from the map, returning the value at the key if the key was previously in the map.

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.

Examples

use halfbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);

pub fn insert_nocheck(&mut self, k: K, v: V)

pub fn is_map(&self) -> bool

Checks if the current backend is a map, if so returns true.

pub fn is_vec(&self) -> bool

Checks if the current backend is a vector, if so returns true.

Trait Implementations

impl<K, V> Default for HashMap<K, V> where
    K: Eq + Hash, 

fn default() -> Self

Returns the "default value" for a type.

impl<K, V> PartialEq<HashMap<K, V>> for HashMap<K, V> where
    K: Eq + Hash,
    V: PartialEq, 

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]

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

This method tests for !=.

impl<K: Clone, V: Clone> Clone for HashMap<K, V> where
    K: Eq + Hash, 

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<K, V> IntoIterator for HashMap<K, V> where
    K: Eq + Hash, 

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?

Important traits for IntoIter<K, V>

impl<K, V> Iterator for IntoIter<K, V> type Item = (K, V);

fn into_iter(self) -> IntoIter<K, V>

Creates an iterator from a value.

impl<'a, K, V> IntoIterator for &'a HashMap<K, V> where
    K: Eq + Hash, 

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?

Important traits for Iter<'a, K, V>

impl<'a, K, V> Iterator for Iter<'a, K, V> type Item = (&'a K, &'a V);

fn into_iter(self) -> Iter<'a, K, V>

Creates an iterator from a value.

impl<K: Debug, V: Debug> Debug for HashMap<K, V> where
    K: Eq + Hash, 

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

Formats the value using the given formatter.

impl<K, Q: ?Sized, V, '_> Index<&'_ Q> for HashMap<K, V> where
    K: Eq + Hash + Borrow<Q>,
    Q: Eq + Hash, 

type Output = V

The returned type after indexing.

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

Performs the indexing (container[index]) operation.

impl<K, V> FromIterator<(K, V)> for HashMap<K, V> where
    K: Eq + Hash, 

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

Creates a value from an iterator.