pub struct AHashMap<K, V, S = RandomState>(/* private fields */);
Expand description
A HashMap
using RandomState
to hash the items.
(Requires the std
feature to be enabled.)
Implementations§
Source§impl<K, V> AHashMap<K, V, RandomState>
impl<K, V> AHashMap<K, V, RandomState>
Sourcepub fn new() -> Self
pub fn new() -> Self
This crates a hashmap using RandomState::new which obtains its keys from [RandomSource]. See the documentation in [RandomSource] for notes about key strength.
Sourcepub fn with_capacity(capacity: usize) -> Self
pub fn with_capacity(capacity: usize) -> Self
This crates a hashmap with the specified capacity using RandomState::new. See the documentation in [RandomSource] for notes about key strength.
Source§impl<K, V, S> AHashMap<K, V, S>where
S: BuildHasher,
impl<K, V, S> AHashMap<K, V, S>where
S: BuildHasher,
pub fn with_hasher(hash_builder: S) -> Self
pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self
Source§impl<K, V, S> AHashMap<K, V, S>
impl<K, V, S> AHashMap<K, V, S>
Sourcepub fn get<Q>(&self, k: &Q) -> Option<&V>
pub fn get<Q>(&self, k: &Q) -> Option<&V>
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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);
Sourcepub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
Returns the key-value pair corresponding to the supplied key.
The supplied 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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);
Sourcepub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
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 std::collections::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");
Sourcepub fn insert(&mut self, k: K, v: V) -> Option<V>
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 std::collections::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");
Sourcepub fn into_keys(self) -> IntoKeys<K, V>
pub fn into_keys(self) -> IntoKeys<K, V>
Creates a consuming iterator visiting all the keys in arbitrary order.
The map cannot be used after calling this.
The iterator element type is K
.
§Examples
use std::collections::HashMap;
let map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
let mut vec: Vec<&str> = map.into_keys().collect();
// The `IntoKeys` iterator produces keys in arbitrary order, so the
// keys must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, ["a", "b", "c"]);
§Performance
In the current implementation, iterating over keys takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
Sourcepub fn into_values(self) -> IntoValues<K, V>
pub fn into_values(self) -> IntoValues<K, V>
Creates a consuming iterator visiting all the values in arbitrary order.
The map cannot be used after calling this.
The iterator element type is V
.
§Examples
use std::collections::HashMap;
let map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
let mut vec: Vec<i32> = map.into_values().collect();
// The `IntoValues` iterator produces values in arbitrary order, so
// the values must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [1, 2, 3]);
§Performance
In the current implementation, iterating over values takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
Sourcepub fn remove<Q>(&mut self, k: &Q) -> Option<V>
pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);
Methods from Deref<Target = HashMap<K, V, S>>§
1.0.0 · Sourcepub fn capacity(&self) -> usize
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 std::collections::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert!(map.capacity() >= 100);
1.0.0 · Sourcepub fn keys(&self) -> Keys<'_, K, V>
pub fn keys(&self) -> Keys<'_, K, V>
An iterator visiting all keys in arbitrary order.
The iterator element type is &'a K
.
§Examples
use std::collections::HashMap;
let map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
for key in map.keys() {
println!("{key}");
}
§Performance
In the current implementation, iterating over keys takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.0.0 · Sourcepub fn values(&self) -> Values<'_, K, 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 std::collections::HashMap;
let map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
for val in map.values() {
println!("{val}");
}
§Performance
In the current implementation, iterating over values takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.10.0 · Sourcepub fn values_mut(&mut self) -> ValuesMut<'_, K, 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 std::collections::HashMap;
let mut map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
for val in map.values_mut() {
*val = *val + 10;
}
for val in map.values() {
println!("{val}");
}
§Performance
In the current implementation, iterating over values takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.0.0 · Sourcepub fn iter(&self) -> Iter<'_, K, 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 std::collections::HashMap;
let map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
for (key, val) in map.iter() {
println!("key: {key} val: {val}");
}
§Performance
In the current implementation, iterating over map takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.0.0 · Sourcepub fn iter_mut(&mut self) -> IterMut<'_, K, 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 std::collections::HashMap;
let mut map = HashMap::from([
("a", 1),
("b", 2),
("c", 3),
]);
// Update all values
for (_, val) in map.iter_mut() {
*val *= 2;
}
for (key, val) in &map {
println!("key: {key} val: {val}");
}
§Performance
In the current implementation, iterating over map takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.0.0 · Sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the number of elements in the map.
§Examples
use std::collections::HashMap;
let mut a = HashMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);
1.0.0 · Sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true
if the map contains no elements.
§Examples
use std::collections::HashMap;
let mut a = HashMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());
1.6.0 · Sourcepub fn drain(&mut self) -> Drain<'_, 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.
If the returned iterator is dropped before being fully consumed, it drops the remaining key-value pairs. The returned iterator keeps a mutable borrow on the map to optimize its implementation.
§Examples
use std::collections::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());
Sourcepub fn extract_if<F>(&mut self, pred: F) -> ExtractIf<'_, K, V, F>
🔬This is a nightly-only experimental API. (hash_extract_if
)
pub fn extract_if<F>(&mut self, pred: F) -> ExtractIf<'_, K, V, F>
hash_extract_if
)Creates an iterator which uses a closure to determine if an element should be removed.
If the closure returns true, the element is removed from the map and yielded. If the closure returns false, or panics, the element remains in the map and will not be yielded.
Note that extract_if
lets you mutate every value in the filter closure, regardless of
whether you choose to keep or remove it.
If the returned ExtractIf
is not exhausted, e.g. because it is dropped without iterating
or the iteration short-circuits, then the remaining elements will be retained.
Use retain
with a negated predicate if you do not need the returned iterator.
§Examples
Splitting a map into even and odd keys, reusing the original map:
#![feature(hash_extract_if)]
use std::collections::HashMap;
let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
let extracted: HashMap<i32, i32> = map.extract_if(|k, _v| k % 2 == 0).collect();
let mut evens = extracted.keys().copied().collect::<Vec<_>>();
let mut odds = map.keys().copied().collect::<Vec<_>>();
evens.sort();
odds.sort();
assert_eq!(evens, vec![0, 2, 4, 6]);
assert_eq!(odds, vec![1, 3, 5, 7]);
1.18.0 · Sourcepub fn retain<F>(&mut self, f: F)
pub fn retain<F>(&mut self, f: F)
Retains only the elements specified by the predicate.
In other words, remove all pairs (k, v)
for which f(&k, &mut v)
returns false
.
The elements are visited in unsorted (and unspecified) order.
§Examples
use std::collections::HashMap;
let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
map.retain(|&k, _| k % 2 == 0);
assert_eq!(map.len(), 4);
§Performance
In the current implementation, this operation takes O(capacity) time instead of O(len) because it internally visits empty buckets too.
1.0.0 · Sourcepub fn clear(&mut self)
pub fn clear(&mut self)
Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.
§Examples
use std::collections::HashMap;
let mut a = HashMap::new();
a.insert(1, "a");
a.clear();
assert!(a.is_empty());
1.9.0 · Sourcepub fn hasher(&self) -> &S
pub fn hasher(&self) -> &S
Returns a reference to the map’s BuildHasher
.
§Examples
use std::collections::HashMap;
use std::hash::RandomState;
let hasher = RandomState::new();
let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
let hasher: &RandomState = map.hasher();
1.0.0 · Sourcepub fn reserve(&mut self, additional: usize)
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 speculatively
avoid frequent reallocations. After calling reserve
,
capacity will be greater than or equal to self.len() + additional
.
Does nothing if capacity is already sufficient.
§Panics
Panics if the new allocation size overflows usize
.
§Examples
use std::collections::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();
map.reserve(10);
1.57.0 · Sourcepub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
Tries to reserve capacity for at least additional
more elements to be inserted
in the HashMap
. The collection may reserve more space to speculatively
avoid frequent reallocations. After calling try_reserve
,
capacity will be greater than or equal to self.len() + additional
if
it returns Ok(())
.
Does nothing if capacity is already sufficient.
§Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
§Examples
use std::collections::HashMap;
let mut map: HashMap<&str, isize> = HashMap::new();
map.try_reserve(10).expect("why is the test harness OOMing on a handful of bytes?");
1.0.0 · Sourcepub fn shrink_to_fit(&mut self)
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 std::collections::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);
1.56.0 · Sourcepub fn shrink_to(&mut self, min_capacity: usize)
pub fn shrink_to(&mut self, min_capacity: usize)
Shrinks the capacity of the map with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.
If the current capacity is less than the lower limit, this is a no-op.
§Examples
use std::collections::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(10);
assert!(map.capacity() >= 10);
map.shrink_to(0);
assert!(map.capacity() >= 2);
1.0.0 · Sourcepub fn entry(&mut self, key: K) -> Entry<'_, K, V>
pub fn entry(&mut self, key: K) -> Entry<'_, K, V>
Gets the given key’s corresponding entry in the map for in-place manipulation.
§Examples
use std::collections::HashMap;
let mut letters = HashMap::new();
for ch in "a short treatise on fungi".chars() {
letters.entry(ch).and_modify(|counter| *counter += 1).or_insert(1);
}
assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);
1.0.0 · Sourcepub fn get<Q>(&self, k: &Q) -> Option<&V>
pub fn get<Q>(&self, k: &Q) -> Option<&V>
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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);
1.40.0 · Sourcepub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
Returns the key-value pair corresponding to the supplied key. This is potentially useful:
- for key types where non-identical keys can be considered equal;
- for getting the
&K
stored key value from a borrowed&Q
lookup key; or - for getting a reference to a key with the same lifetime as the collection.
The supplied 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 std::collections::HashMap;
use std::hash::{Hash, Hasher};
#[derive(Clone, Copy, Debug)]
struct S {
id: u32,
name: &'static str, // ignored by equality and hashing operations
}
impl PartialEq for S {
fn eq(&self, other: &S) -> bool {
self.id == other.id
}
}
impl Eq for S {}
impl Hash for S {
fn hash<H: Hasher>(&self, state: &mut H) {
self.id.hash(state);
}
}
let j_a = S { id: 1, name: "Jessica" };
let j_b = S { id: 1, name: "Jess" };
let p = S { id: 2, name: "Paul" };
assert_eq!(j_a, j_b);
let mut map = HashMap::new();
map.insert(j_a, "Paris");
assert_eq!(map.get_key_value(&j_a), Some((&j_a, &"Paris")));
assert_eq!(map.get_key_value(&j_b), Some((&j_a, &"Paris"))); // the notable case
assert_eq!(map.get_key_value(&p), None);
Sourcepub fn get_many_mut<Q, const N: usize>(
&mut self,
ks: [&Q; N],
) -> [Option<&mut V>; N]
🔬This is a nightly-only experimental API. (map_many_mut
)
pub fn get_many_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]
map_many_mut
)Attempts to get mutable references to N
values in the map at once.
Returns an array of length N
with the results of each query. For soundness, at most one
mutable reference will be returned to any value. None
will be used if the key is missing.
§Panics
Panics if any keys are overlapping.
§Examples
#![feature(map_many_mut)]
use std::collections::HashMap;
let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);
// Get Athenæum and Bodleian Library
let [Some(a), Some(b)] = libraries.get_many_mut([
"Athenæum",
"Bodleian Library",
]) else { panic!() };
// Assert values of Athenæum and Library of Congress
let got = libraries.get_many_mut([
"Athenæum",
"Library of Congress",
]);
assert_eq!(
got,
[
Some(&mut 1807),
Some(&mut 1800),
],
);
// Missing keys result in None
let got = libraries.get_many_mut([
"Athenæum",
"New York Public Library",
]);
assert_eq!(
got,
[
Some(&mut 1807),
None
]
);
#![feature(map_many_mut)]
use std::collections::HashMap;
let mut libraries = HashMap::new();
libraries.insert("Athenæum".to_string(), 1807);
// Duplicate keys panic!
let got = libraries.get_many_mut([
"Athenæum",
"Athenæum",
]);
Sourcepub unsafe fn get_many_unchecked_mut<Q, const N: usize>(
&mut self,
ks: [&Q; N],
) -> [Option<&mut V>; N]
🔬This is a nightly-only experimental API. (map_many_mut
)
pub unsafe fn get_many_unchecked_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]
map_many_mut
)Attempts to get mutable references to N
values in the map at once, without validating that
the values are unique.
Returns an array of length N
with the results of each query. None
will be used if
the key is missing.
For a safe alternative see get_many_mut
.
§Safety
Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.
§Examples
#![feature(map_many_mut)]
use std::collections::HashMap;
let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);
// SAFETY: The keys do not overlap.
let [Some(a), Some(b)] = (unsafe { libraries.get_many_unchecked_mut([
"Athenæum",
"Bodleian Library",
]) }) else { panic!() };
// SAFETY: The keys do not overlap.
let got = unsafe { libraries.get_many_unchecked_mut([
"Athenæum",
"Library of Congress",
]) };
assert_eq!(
got,
[
Some(&mut 1807),
Some(&mut 1800),
],
);
// SAFETY: The keys do not overlap.
let got = unsafe { libraries.get_many_unchecked_mut([
"Athenæum",
"New York Public Library",
]) };
// Missing keys result in None
assert_eq!(got, [Some(&mut 1807), None]);
1.0.0 · Sourcepub fn contains_key<Q>(&self, k: &Q) -> bool
pub fn contains_key<Q>(&self, k: &Q) -> bool
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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);
1.0.0 · Sourcepub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
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 std::collections::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");
1.0.0 · Sourcepub fn insert(&mut self, k: K, v: V) -> Option<V>
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 std::collections::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");
Sourcepub fn try_insert(
&mut self,
key: K,
value: V,
) -> Result<&mut V, OccupiedError<'_, K, V>>
🔬This is a nightly-only experimental API. (map_try_insert
)
pub fn try_insert( &mut self, key: K, value: V, ) -> Result<&mut V, OccupiedError<'_, K, V>>
map_try_insert
)Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.
If the map already had this key present, nothing is updated, and an error containing the occupied entry and the value is returned.
§Examples
Basic usage:
#![feature(map_try_insert)]
use std::collections::HashMap;
let mut map = HashMap::new();
assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
let err = map.try_insert(37, "b").unwrap_err();
assert_eq!(err.entry.key(), &37);
assert_eq!(err.entry.get(), &"a");
assert_eq!(err.value, "b");
1.0.0 · Sourcepub fn remove<Q>(&mut self, k: &Q) -> Option<V>
pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);
1.27.0 · Sourcepub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>
pub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>
Removes a key from the map, returning the stored key and value 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 std::collections::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove(&1), None);
Sourcepub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S>
🔬This is a nightly-only experimental API. (hash_raw_entry
)
pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S>
hash_raw_entry
)Creates a raw entry builder for the HashMap.
Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched. After this, insertions into a vacant entry still require an owned key to be provided.
Raw entries are useful for such exotic situations as:
- Hash memoization
- Deferring the creation of an owned key until it is known to be required
- Using a search key that doesn’t work with the Borrow trait
- Using custom comparison logic without newtype wrappers
Because raw entries provide much more low-level control, it’s much easier
to put the HashMap into an inconsistent state which, while memory-safe,
will cause the map to produce seemingly random results. Higher-level and
more foolproof APIs like entry
should be preferred when possible.
In particular, the hash used to initialize the raw entry must still be consistent with the hash of the key that is ultimately stored in the entry. This is because implementations of HashMap may need to recompute hashes when resizing, at which point only the keys are available.
Raw entries give mutable access to the keys. This must not be used to modify how the key would compare or hash, as the map will not re-evaluate where the key should go, meaning the keys may become “lost” if their location does not reflect their state. For instance, if you change a key so that the map now contains keys which compare equal, search may start acting erratically, with two keys randomly masking each other. Implementations are free to assume this doesn’t happen (within the limits of memory-safety).
Sourcepub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S>
🔬This is a nightly-only experimental API. (hash_raw_entry
)
pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S>
hash_raw_entry
)Creates a raw immutable entry builder for the HashMap.
Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched.
This is useful for
- Hash memoization
- Using a search key that doesn’t work with the Borrow trait
- Using custom comparison logic without newtype wrappers
Unless you are in such a situation, higher-level and more foolproof APIs like
get
should be preferred.
Immutable raw entries have very limited use; you might instead want raw_entry_mut
.
Trait Implementations§
Source§impl<'a, K, V, S> Extend<(&'a K, &'a V)> for AHashMap<K, V, S>
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for AHashMap<K, V, S>
Source§fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T)
Source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)Source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)Source§impl<K, V, S> Extend<(K, V)> for AHashMap<K, V, S>
impl<K, V, S> Extend<(K, V)> for AHashMap<K, V, S>
Source§fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)
Source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)Source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)Source§impl<K, V> From<HashMap<K, V, RandomState>> for AHashMap<K, V>
impl<K, V> From<HashMap<K, V, RandomState>> for AHashMap<K, V>
Source§fn from(item: HashMap<K, V, RandomState>) -> Self
fn from(item: HashMap<K, V, RandomState>) -> Self
Source§impl<K, V> FromIterator<(K, V)> for AHashMap<K, V, RandomState>
impl<K, V> FromIterator<(K, V)> for AHashMap<K, V, RandomState>
Source§fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self
fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self
This crates a hashmap from the provided iterator using RandomState::new. See the documentation in [RandomSource] for notes about key strength.