pub struct HashMap<K, V, S = DefaultHashBuilder, A: Allocator = Global> { /* private fields */ }
Expand description
A hash map implemented with quadratic probing and SIMD lookup.
The default hashing algorithm is currently foldhash
, though this is
subject to change at any point in the future. This hash function is very
fast for all types of keys, but this algorithm will typically not protect
against attacks such as HashDoS.
The hashing algorithm can be replaced on a per-HashMap
basis using the
default
, with_hasher
, and with_capacity_and_hasher
methods. Many
alternative algorithms are available on crates.io, such as the fnv
crate.
It is required that the keys implement the Eq
and Hash
traits, although
this can frequently be achieved by using #[derive(PartialEq, Eq, Hash)]
.
If you implement these yourself, it is important that the following
property holds:
k1 == k2 -> hash(k1) == hash(k2)
In other words, if two keys are equal, their hashes must be equal.
It is a logic error for a key to be modified in such a way that the key’s
hash, as determined by the Hash
trait, or its equality, as determined by
the Eq
trait, changes while it is in the map. This is normally only
possible through Cell
, RefCell
, global state, I/O, or unsafe code.
It is also a logic error for the Hash
implementation of a key to panic.
This is generally only possible if the trait is implemented manually. If a
panic does occur then the contents of the HashMap
may become corrupted and
some items may be dropped from the table.
§Examples
use hashbrown::HashMap;
// Type inference lets us omit an explicit type signature (which
// would be `HashMap<String, String>` in this example).
let mut book_reviews = HashMap::new();
// Review some books.
book_reviews.insert(
"Adventures of Huckleberry Finn".to_string(),
"My favorite book.".to_string(),
);
book_reviews.insert(
"Grimms' Fairy Tales".to_string(),
"Masterpiece.".to_string(),
);
book_reviews.insert(
"Pride and Prejudice".to_string(),
"Very enjoyable.".to_string(),
);
book_reviews.insert(
"The Adventures of Sherlock Holmes".to_string(),
"Eye lyked it alot.".to_string(),
);
// Check for a specific one.
// When collections store owned values (String), they can still be
// queried using references (&str).
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)
}
}
// Look up the value for a key (will panic if the key is not found).
println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);
// Iterate over everything.
for (book, review) in &book_reviews {
println!("{}: \"{}\"", book, review);
}
HashMap
also implements an Entry API
, which allows
for more complex methods of getting, setting, updating and removing keys and
their values:
use hashbrown::HashMap;
// type inference lets us omit an explicit type signature (which
// would be `HashMap<&str, u8>` in this example).
let mut player_stats = HashMap::new();
fn random_stat_buff() -> u8 {
// could actually return some random value here - let's just return
// some fixed value for now
42
}
// insert a key only if it doesn't already exist
player_stats.entry("health").or_insert(100);
// insert a key using a function that provides a new value only if it
// doesn't already exist
player_stats.entry("defence").or_insert_with(random_stat_buff);
// update a key, guarding against the key possibly not being set
let stat = player_stats.entry("attack").or_insert(100);
*stat += random_stat_buff();
The easiest way to use HashMap
with a custom key type is to derive Eq
and Hash
.
We must also derive PartialEq
.
use hashbrown::HashMap;
#[derive(Hash, Eq, PartialEq, Debug)]
struct Viking {
name: String,
country: String,
}
impl Viking {
/// Creates a new Viking.
fn new(name: &str, country: &str) -> Viking {
Viking { name: name.to_string(), country: country.to_string() }
}
}
// Use a HashMap to store the vikings' health points.
let mut vikings = HashMap::new();
vikings.insert(Viking::new("Einar", "Norway"), 25);
vikings.insert(Viking::new("Olaf", "Denmark"), 24);
vikings.insert(Viking::new("Harald", "Iceland"), 12);
// Use derived implementation to print the status of the vikings.
for (viking, health) in &vikings {
println!("{:?} has {} hp", viking, health);
}
A HashMap
with fixed list of elements can be initialized from an array:
use hashbrown::HashMap;
let timber_resources: HashMap<&str, i32> = [("Norway", 100), ("Denmark", 50), ("Iceland", 10)]
.into_iter().collect();
// use the values stored in map
Implementations§
source§impl<K, V, S> HashMap<K, V, S>
impl<K, V, S> HashMap<K, V, S>
sourcepub const fn with_hasher(hash_builder: S) -> Self
pub const fn with_hasher(hash_builder: S) -> Self
Creates an empty HashMap
which will use the given hash builder to hash
keys.
The hash map is initially created with a capacity of 0, so it will not allocate until it is first inserted into.
§HashDoS resistance
The hash_builder
normally use a fixed key by default and that does
not allow the HashMap
to be protected against attacks such as HashDoS
.
Users who require HashDoS resistance should explicitly use
std::collections::hash_map::RandomState
as the hasher when creating a HashMap
.
The hash_builder
passed should implement the BuildHasher
trait for
the HashMap
to be useful, see its documentation for details.
§Examples
use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;
let s = DefaultHashBuilder::default();
let mut map = HashMap::with_hasher(s);
assert_eq!(map.len(), 0);
assert_eq!(map.capacity(), 0);
map.insert(1, 2);
sourcepub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self
pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self
Creates an empty HashMap
with the specified capacity, using hash_builder
to hash the keys.
The hash map will be able to hold at least capacity
elements without
reallocating. If capacity
is 0, the hash map will not allocate.
§HashDoS resistance
The hash_builder
normally use a fixed key by default and that does
not allow the HashMap
to be protected against attacks such as HashDoS
.
Users who require HashDoS resistance should explicitly use
std::collections::hash_map::RandomState
as the hasher when creating a HashMap
.
The hash_builder
passed should implement the BuildHasher
trait for
the HashMap
to be useful, see its documentation for details.
§Examples
use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;
let s = DefaultHashBuilder::default();
let mut map = HashMap::with_capacity_and_hasher(10, s);
assert_eq!(map.len(), 0);
assert!(map.capacity() >= 10);
map.insert(1, 2);
source§impl<K, V, S, A: Allocator> HashMap<K, V, S, A>
impl<K, V, S, A: Allocator> HashMap<K, V, S, A>
sourcepub const fn with_hasher_in(hash_builder: S, alloc: A) -> Self
pub const fn with_hasher_in(hash_builder: S, alloc: A) -> Self
Creates an empty HashMap
which will use the given hash builder to hash
keys. It will be allocated with the given allocator.
The hash map is initially created with a capacity of 0, so it will not allocate until it is first inserted into.
§HashDoS resistance
The hash_builder
normally use a fixed key by default and that does
not allow the HashMap
to be protected against attacks such as HashDoS
.
Users who require HashDoS resistance should explicitly use
std::collections::hash_map::RandomState
as the hasher when creating a HashMap
.
§Examples
use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;
let s = DefaultHashBuilder::default();
let mut map = HashMap::with_hasher(s);
map.insert(1, 2);
sourcepub fn with_capacity_and_hasher_in(
capacity: usize,
hash_builder: S,
alloc: A,
) -> Self
pub fn with_capacity_and_hasher_in( capacity: usize, hash_builder: S, alloc: A, ) -> Self
Creates an empty HashMap
with the specified capacity, using hash_builder
to hash the keys. It will be allocated with the given allocator.
The hash map will be able to hold at least capacity
elements without
reallocating. If capacity
is 0, the hash map will not allocate.
§HashDoS resistance
The hash_builder
normally use a fixed key by default and that does
not allow the HashMap
to be protected against attacks such as HashDoS
.
Users who require HashDoS resistance should explicitly use
std::collections::hash_map::RandomState
as the hasher when creating a HashMap
.
§Examples
use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;
let s = DefaultHashBuilder::default();
let mut map = HashMap::with_capacity_and_hasher(10, s);
map.insert(1, 2);
sourcepub fn hasher(&self) -> &S
pub fn hasher(&self) -> &S
Returns a reference to the map’s BuildHasher
.
§Examples
use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;
let hasher = DefaultHashBuilder::default();
let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
let hasher: &DefaultHashBuilder = map.hasher();
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 hashbrown::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert_eq!(map.len(), 0);
assert!(map.capacity() >= 100);
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<&str> = Vec::new();
for key in map.keys() {
println!("{}", key);
vec.push(*key);
}
// The `Keys` 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"]);
assert_eq!(map.len(), 3);
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<i32> = Vec::new();
for val in map.values() {
println!("{}", val);
vec.push(*val);
}
// The `Values` 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]);
assert_eq!(map.len(), 3);
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 hashbrown::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;
}
assert_eq!(map.len(), 3);
let mut vec: Vec<i32> = Vec::new();
for val in map.values() {
println!("{}", val);
vec.push(*val);
}
// The `Values` 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, [11, 12, 13]);
assert_eq!(map.len(), 3);
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<(&str, i32)> = Vec::new();
for (key, val) in map.iter() {
println!("key: {} val: {}", key, val);
vec.push((*key, *val));
}
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [("a", 1), ("b", 2), ("c", 3)]);
assert_eq!(map.len(), 3);
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 hashbrown::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;
}
assert_eq!(map.len(), 3);
let mut vec: Vec<(&str, i32)> = Vec::new();
for (key, val) in &map {
println!("key: {} val: {}", key, val);
vec.push((*key, *val));
}
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [("a", 2), ("b", 4), ("c", 6)]);
assert_eq!(map.len(), 3);
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the number of elements in the map.
§Examples
use hashbrown::HashMap;
let mut a = HashMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true
if the map contains no elements.
§Examples
use hashbrown::HashMap;
let mut a = HashMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());
sourcepub fn drain(&mut self) -> Drain<'_, K, V, A> ⓘ
pub fn drain(&mut self) -> Drain<'_, K, V, A> ⓘ
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 vector to optimize its implementation.
§Examples
use hashbrown::HashMap;
let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");
let capacity_before_drain = a.capacity();
for (k, v) in a.drain().take(1) {
assert!(k == 1 || k == 2);
assert!(v == "a" || v == "b");
}
// As we can see, the map is empty and contains no element.
assert!(a.is_empty() && a.len() == 0);
// But map capacity is equal to old one.
assert_eq!(a.capacity(), capacity_before_drain);
let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");
{ // Iterator is dropped without being consumed.
let d = a.drain();
}
// But the map is empty even if we do not use Drain iterator.
assert!(a.is_empty());
sourcepub fn retain<F>(&mut self, f: F)
pub fn retain<F>(&mut self, f: F)
Retains only the elements specified by the predicate. Keeps the allocated memory for reuse.
In other words, remove all pairs (k, v)
such that f(&k, &mut v)
returns false
.
The elements are visited in unsorted (and unspecified) order.
§Examples
use hashbrown::HashMap;
let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
assert_eq!(map.len(), 8);
map.retain(|&k, _| k % 2 == 0);
// We can see, that the number of elements inside map is changed.
assert_eq!(map.len(), 4);
let mut vec: Vec<(i32, i32)> = map.iter().map(|(&k, &v)| (k, v)).collect();
vec.sort_unstable();
assert_eq!(vec, [(0, 0), (2, 20), (4, 40), (6, 60)]);
sourcepub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F, A> ⓘ
pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F, A> ⓘ
Drains elements which are true under the given predicate, and returns an iterator over the removed items.
In other words, move all pairs (k, v)
such that f(&k, &mut v)
returns true
out
into another iterator.
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.
Keeps the allocated memory for reuse.
§Examples
use hashbrown::HashMap;
let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
let drained: HashMap<i32, i32> = map.extract_if(|k, _v| k % 2 == 0).collect();
let mut evens = drained.keys().cloned().collect::<Vec<_>>();
let mut odds = map.keys().cloned().collect::<Vec<_>>();
evens.sort();
odds.sort();
assert_eq!(evens, vec![0, 2, 4, 6]);
assert_eq!(odds, vec![1, 3, 5, 7]);
let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
{ // Iterator is dropped without being consumed.
let d = map.extract_if(|k, _v| k % 2 != 0);
}
// ExtractIf was not exhausted, therefore no elements were drained.
assert_eq!(map.len(), 8);
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 hashbrown::HashMap;
let mut a = HashMap::new();
a.insert(1, "a");
let capacity_before_clear = a.capacity();
a.clear();
// Map is empty.
assert!(a.is_empty());
// But map capacity is equal to old one.
assert_eq!(a.capacity(), capacity_before_clear);
sourcepub fn into_keys(self) -> IntoKeys<K, V, A> ⓘ
pub fn into_keys(self) -> IntoKeys<K, V, A> ⓘ
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("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"]);
sourcepub fn into_values(self) -> IntoValues<K, V, A> ⓘ
pub fn into_values(self) -> IntoValues<K, V, A> ⓘ
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("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]);
source§impl<K, V, S, A> HashMap<K, V, S, A>
impl<K, V, S, A> HashMap<K, V, S, A>
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 avoid
frequent reallocations.
§Panics
Panics if the new capacity exceeds isize::MAX
bytes and abort
the program
in case of allocation error. Use try_reserve
instead
if you want to handle memory allocation failure.
§Examples
use hashbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();
// Map is empty and doesn't allocate memory
assert_eq!(map.capacity(), 0);
map.reserve(10);
// And now map can hold at least 10 elements
assert!(map.capacity() >= 10);
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 given HashMap<K,V>
. The collection may reserve more space to avoid
frequent reallocations.
§Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
§Examples
use hashbrown::HashMap;
let mut map: HashMap<&str, isize> = HashMap::new();
// Map is empty and doesn't allocate memory
assert_eq!(map.capacity(), 0);
map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
// And now map can hold at least 10 elements
assert!(map.capacity() >= 10);
If the capacity overflows, or the allocator reports a failure, then an error is returned:
use hashbrown::HashMap;
use hashbrown::TryReserveError;
let mut map: HashMap<i32, i32> = HashMap::new();
match map.try_reserve(usize::MAX) {
Err(error) => match error {
TryReserveError::CapacityOverflow => {}
_ => panic!("TryReserveError::AllocError ?"),
},
_ => panic!(),
}
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 hashbrown::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);
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.
This function does nothing if the current capacity is smaller than the supplied minimum capacity.
§Examples
use hashbrown::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);
map.shrink_to(10);
assert!(map.capacity() >= 2);
sourcepub fn entry(&mut self, key: K) -> Entry<'_, K, V, S, A>
pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S, A>
Gets the given key’s corresponding entry in the map for in-place manipulation.
§Examples
use hashbrown::HashMap;
let mut letters = HashMap::new();
for ch in "a short treatise on fungi".chars() {
let counter = letters.entry(ch).or_insert(0);
*counter += 1;
}
assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);
sourcepub fn entry_ref<'a, 'b, Q>(
&'a mut self,
key: &'b Q,
) -> EntryRef<'a, 'b, K, Q, V, S, A>
pub fn entry_ref<'a, 'b, Q>( &'a mut self, key: &'b Q, ) -> EntryRef<'a, 'b, K, Q, V, S, A>
Gets the given key’s corresponding entry by reference in the map for in-place manipulation.
§Examples
use hashbrown::HashMap;
let mut words: HashMap<String, usize> = HashMap::new();
let source = ["poneyland", "horseyland", "poneyland", "poneyland"];
for (i, &s) in source.iter().enumerate() {
let counter = words.entry_ref(s).or_insert(0);
*counter += 1;
}
assert_eq!(words["poneyland"], 3);
assert_eq!(words["horseyland"], 1);
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 hashbrown::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 hashbrown::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_key_value_mut<Q>(&mut self, k: &Q) -> Option<(&K, &mut V)>
pub fn get_key_value_mut<Q>(&mut self, k: &Q) -> Option<(&K, &mut V)>
Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
let (k, v) = map.get_key_value_mut(&1).unwrap();
assert_eq!(k, &1);
assert_eq!(v, &mut "a");
*v = "b";
assert_eq!(map.get_key_value_mut(&1), Some((&1, &mut "b")));
assert_eq!(map.get_key_value_mut(&2), None);
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 hashbrown::HashMap;
let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);
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 hashbrown::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");
assert_eq!(map.get_mut(&2), None);
sourcepub fn get_many_mut<Q, const N: usize>(
&mut self,
ks: [&Q; N],
) -> [Option<&mut V>; N]
pub fn get_many_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]
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
use hashbrown::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
]
);
use hashbrown::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]
pub unsafe fn get_many_unchecked_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]
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
use hashbrown::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]);
sourcepub fn get_many_key_value_mut<Q, const N: usize>(
&mut self,
ks: [&Q; N],
) -> [Option<(&K, &mut V)>; N]
pub fn get_many_key_value_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<(&K, &mut V)>; N]
Attempts to get mutable references to N
values in the map at once, with immutable
references to the corresponding keys.
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
use hashbrown::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);
let got = libraries.get_many_key_value_mut([
"Bodleian Library",
"Herzogin-Anna-Amalia-Bibliothek",
]);
assert_eq!(
got,
[
Some((&"Bodleian Library".to_string(), &mut 1602)),
Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut 1691)),
],
);
// Missing keys result in None
let got = libraries.get_many_key_value_mut([
"Bodleian Library",
"Gewandhaus",
]);
assert_eq!(got, [Some((&"Bodleian Library".to_string(), &mut 1602)), None]);
use hashbrown::HashMap;
let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
// Duplicate keys result in panic!
let got = libraries.get_many_key_value_mut([
"Bodleian Library",
"Herzogin-Anna-Amalia-Bibliothek",
"Herzogin-Anna-Amalia-Bibliothek",
]);
sourcepub unsafe fn get_many_key_value_unchecked_mut<Q, const N: usize>(
&mut self,
ks: [&Q; N],
) -> [Option<(&K, &mut V)>; N]
pub unsafe fn get_many_key_value_unchecked_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<(&K, &mut V)>; N]
Attempts to get mutable references to N
values in the map at once, with immutable
references to the corresponding keys, without validating that the values are unique.
Returns an array of length N
with the results of each query. None
will be returned if
any of the keys are missing.
For a safe alternative see get_many_key_value_mut
.
§Safety
Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.
§Examples
use hashbrown::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);
let got = libraries.get_many_key_value_mut([
"Bodleian Library",
"Herzogin-Anna-Amalia-Bibliothek",
]);
assert_eq!(
got,
[
Some((&"Bodleian Library".to_string(), &mut 1602)),
Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut 1691)),
],
);
// Missing keys result in None
let got = libraries.get_many_key_value_mut([
"Bodleian Library",
"Gewandhaus",
]);
assert_eq!(
got,
[
Some((&"Bodleian Library".to_string(), &mut 1602)),
None,
],
);
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 std::collections
module-level documentation for more.
§Examples
use hashbrown::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 unsafe fn insert_unique_unchecked(&mut self, k: K, v: V) -> (&K, &mut V)
pub unsafe fn insert_unique_unchecked(&mut self, k: K, v: V) -> (&K, &mut V)
Insert a key-value pair into the map without checking if the key already exists in the map.
This operation is faster than regular insert, because it does not perform lookup before insertion.
This operation is useful during initial population of the map. For example, when constructing a map from another map, we know that keys are unique.
Returns a reference to the key and value just inserted.
§Safety
This operation is safe if a key does not exist in the map.
However, if a key exists in the map already, the behavior is unspecified: this operation may panic, loop forever, or any following operation with the map may panic, loop forever or return arbitrary result.
That said, this operation (and following operations) are guaranteed to not violate memory safety.
However this operation is still unsafe because the resulting HashMap
may be passed to unsafe code which does expect the map to behave
correctly, and would cause unsoundness as a result.
§Examples
use hashbrown::HashMap;
let mut map1 = HashMap::new();
assert_eq!(map1.insert(1, "a"), None);
assert_eq!(map1.insert(2, "b"), None);
assert_eq!(map1.insert(3, "c"), None);
assert_eq!(map1.len(), 3);
let mut map2 = HashMap::new();
for (key, value) in map1.into_iter() {
unsafe {
map2.insert_unique_unchecked(key, value);
}
}
let (key, value) = unsafe { map2.insert_unique_unchecked(4, "d") };
assert_eq!(key, &4);
assert_eq!(value, &mut "d");
*value = "e";
assert_eq!(map2[&1], "a");
assert_eq!(map2[&2], "b");
assert_eq!(map2[&3], "c");
assert_eq!(map2[&4], "e");
assert_eq!(map2.len(), 4);
sourcepub fn try_insert(
&mut self,
key: K,
value: V,
) -> Result<&mut V, OccupiedError<'_, K, V, S, A>>
pub fn try_insert( &mut self, key: K, value: V, ) -> Result<&mut V, OccupiedError<'_, K, V, S, A>>
Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.
§Errors
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:
use hashbrown::HashMap;
use hashbrown::hash_map::OccupiedError;
let mut map = HashMap::new();
assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
match map.try_insert(37, "b") {
Err(OccupiedError { entry, value }) => {
assert_eq!(entry.key(), &37);
assert_eq!(entry.get(), &"a");
assert_eq!(value, "b");
}
_ => panic!()
}
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. Keeps the allocated memory for reuse.
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 hashbrown::HashMap;
let mut map = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);
map.insert(1, "a");
assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);
// Now map holds none elements
assert!(map.is_empty());
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. Keeps the allocated memory for reuse.
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 hashbrown::HashMap;
let mut map = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);
map.insert(1, "a");
assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove(&1), None);
// Now map hold none elements
assert!(map.is_empty());
sourcepub fn allocation_size(&self) -> usize
pub fn allocation_size(&self) -> usize
Returns the total amount of memory allocated internally by the hash set, in bytes.
The returned number is informational only. It is intended to be primarily used for memory profiling.
Trait Implementations§
source§impl<K, V, S, A> Default for HashMap<K, V, S, A>
impl<K, V, S, A> Default for HashMap<K, V, S, A>
source§fn default() -> Self
fn default() -> Self
Creates an empty HashMap<K, V, S, A>
, with the Default
value for the hasher and allocator.
§Examples
use hashbrown::HashMap;
use std::collections::hash_map::RandomState;
// You can specify all types of HashMap, including hasher and allocator.
// Created map is empty and don't allocate memory
let map: HashMap<u32, String> = Default::default();
assert_eq!(map.capacity(), 0);
let map: HashMap<u32, String, RandomState> = HashMap::default();
assert_eq!(map.capacity(), 0);
source§impl<'a, K, V, S, A> Extend<&'a (K, V)> for HashMap<K, V, S, A>
impl<'a, K, V, S, A> Extend<&'a (K, V)> for HashMap<K, V, S, A>
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
source§fn extend<T: IntoIterator<Item = &'a (K, V)>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = &'a (K, V)>>(&mut self, iter: T)
Inserts all new key-values from the iterator to existing HashMap<K, V, S, A>
.
Replace values with existing keys with new values returned from the iterator.
The keys and values must implement Copy
trait.
§Examples
use hashbrown::hash_map::HashMap;
let mut map = HashMap::new();
map.insert(1, 100);
let arr = [(1, 1), (2, 2)];
let some_iter = arr.iter();
map.extend(some_iter);
// Replace values with existing keys with new values returned from the iterator.
// So that the map.get(&1) doesn't return Some(&100).
assert_eq!(map.get(&1), Some(&1));
let some_vec: Vec<_> = vec![(3, 3), (4, 4)];
map.extend(&some_vec);
let some_arr = [(5, 5), (6, 6)];
map.extend(&some_arr);
let mut vec: Vec<_> = map.into_iter().collect();
// The `IntoIter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)]);
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<'a, K, V, S, A> Extend<(&'a K, &'a V)> for HashMap<K, V, S, A>
impl<'a, K, V, S, A> Extend<(&'a K, &'a V)> for HashMap<K, V, S, A>
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
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)
Inserts all new key-values from the iterator to existing HashMap<K, V, S, A>
.
Replace values with existing keys with new values returned from the iterator.
The keys and values must implement Copy
trait.
§Examples
use hashbrown::hash_map::HashMap;
let mut map = HashMap::new();
map.insert(1, 100);
let arr = [(1, 1), (2, 2)];
let some_iter = arr.iter().map(|(k, v)| (k, v));
map.extend(some_iter);
// Replace values with existing keys with new values returned from the iterator.
// So that the map.get(&1) doesn't return Some(&100).
assert_eq!(map.get(&1), Some(&1));
let some_vec: Vec<_> = vec![(3, 3), (4, 4)];
map.extend(some_vec.iter().map(|(k, v)| (k, v)));
let some_arr = [(5, 5), (6, 6)];
map.extend(some_arr.iter().map(|(k, v)| (k, v)));
// You can also extend from another HashMap
let mut new_map = HashMap::new();
new_map.extend(&map);
assert_eq!(new_map, map);
let mut vec: Vec<_> = new_map.into_iter().collect();
// The `IntoIter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)]);
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, A> Extend<(K, V)> for HashMap<K, V, S, A>
impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A>
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
source§fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)
Inserts all new key-values from the iterator to existing HashMap<K, V, S, A>
.
Replace values with existing keys with new values returned from the iterator.
§Examples
use hashbrown::hash_map::HashMap;
let mut map = HashMap::new();
map.insert(1, 100);
let some_iter = [(1, 1), (2, 2)].into_iter();
map.extend(some_iter);
// Replace values with existing keys with new values returned from the iterator.
// So that the map.get(&1) doesn't return Some(&100).
assert_eq!(map.get(&1), Some(&1));
let some_vec: Vec<_> = vec![(3, 3), (4, 4)];
map.extend(some_vec);
let some_arr = [(5, 5), (6, 6)];
map.extend(some_arr);
let old_map_len = map.len();
// You can also extend from another HashMap
let mut new_map = HashMap::new();
new_map.extend(map);
assert_eq!(new_map.len(), old_map_len);
let mut vec: Vec<_> = new_map.into_iter().collect();
// The `IntoIter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)]);
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, A> FromIterator<(K, V)> for HashMap<K, V, S, A>
impl<K, V, S, A> FromIterator<(K, V)> for HashMap<K, V, S, A>
source§impl<'a, K, V, S, A: Allocator> IntoIterator for &'a HashMap<K, V, S, A>
impl<'a, K, V, S, A: Allocator> IntoIterator for &'a HashMap<K, V, S, A>
source§fn into_iter(self) -> Iter<'a, K, V> ⓘ
fn into_iter(self) -> Iter<'a, K, V> ⓘ
Creates an iterator over the entries of a HashMap
in arbitrary order.
The iterator element type is (&'a K, &'a V)
.
Return the same Iter
struct as by the iter
method on HashMap
.
§Examples
use hashbrown::HashMap;
let map_one: HashMap<_, _> = [(1, "a"), (2, "b"), (3, "c")].into();
let mut map_two = HashMap::new();
for (key, value) in &map_one {
println!("Key: {}, Value: {}", key, value);
map_two.insert(*key, *value);
}
assert_eq!(map_one, map_two);
source§impl<'a, K, V, S, A: Allocator> IntoIterator for &'a mut HashMap<K, V, S, A>
impl<'a, K, V, S, A: Allocator> IntoIterator for &'a mut HashMap<K, V, S, A>
source§fn into_iter(self) -> IterMut<'a, K, V> ⓘ
fn into_iter(self) -> IterMut<'a, K, V> ⓘ
Creates an iterator over the entries of a HashMap
in arbitrary order
with mutable references to the values. The iterator element type is
(&'a K, &'a mut V)
.
Return the same IterMut
struct as by the iter_mut
method on
HashMap
.
§Examples
use hashbrown::HashMap;
let mut map: HashMap<_, _> = [("a", 1), ("b", 2), ("c", 3)].into();
for (key, value) in &mut map {
println!("Key: {}, Value: {}", key, value);
*value *= 2;
}
let mut vec = map.iter().collect::<Vec<_>>();
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [(&"a", &2), (&"b", &4), (&"c", &6)]);
source§impl<K, V, S, A: Allocator> IntoIterator for HashMap<K, V, S, A>
impl<K, V, S, A: Allocator> IntoIterator for HashMap<K, V, S, A>
source§fn into_iter(self) -> IntoIter<K, V, A> ⓘ
fn into_iter(self) -> IntoIter<K, V, A> ⓘ
Creates a consuming iterator, that is, one that moves each key-value pair out of the map in arbitrary order. The map cannot be used after calling this.
§Examples
use hashbrown::HashMap;
let map: HashMap<_, _> = [("a", 1), ("b", 2), ("c", 3)].into();
// Not possible with .iter()
let mut vec: Vec<(&str, i32)> = map.into_iter().collect();
// The `IntoIter` iterator produces items in arbitrary order, so
// the items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [("a", 1), ("b", 2), ("c", 3)]);
source§impl<K, V, S, A> PartialEq for HashMap<K, V, S, A>
impl<K, V, S, A> PartialEq for HashMap<K, V, S, A>
impl<K, V, S, A> Eq for HashMap<K, V, S, A>
Auto Trait Implementations§
impl<K, V, S, A> Freeze for HashMap<K, V, S, A>
impl<K, V, S, A> RefUnwindSafe for HashMap<K, V, S, A>
impl<K, V, S, A> Send for HashMap<K, V, S, A>
impl<K, V, S, A> Sync for HashMap<K, V, S, A>
impl<K, V, S, A> Unpin for HashMap<K, V, S, A>
impl<K, V, S, A> UnwindSafe for HashMap<K, V, S, A>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§default unsafe fn clone_to_uninit(&self, dst: *mut T)
default unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)