6 use hashbrown::hash_map as base;
8 use crate::borrow::Borrow;
10 use crate::collections::TryReserveError;
11 use crate::collections::TryReserveErrorKind;
12 use crate::fmt::{self, Debug};
14 use crate::hash::{BuildHasher, Hash, Hasher, SipHasher13};
15 use crate::iter::{FromIterator, FusedIterator};
16 use crate::ops::Index;
19 /// A [hash map] implemented with quadratic probing and SIMD lookup.
21 /// By default, `HashMap` uses a hashing algorithm selected to provide
22 /// resistance against HashDoS attacks. The algorithm is randomly seeded, and a
23 /// reasonable best-effort is made to generate this seed from a high quality,
24 /// secure source of randomness provided by the host without blocking the
25 /// program. Because of this, the randomness of the seed depends on the output
26 /// quality of the system's random number generator when the seed is created.
27 /// In particular, seeds generated when the system's entropy pool is abnormally
28 /// low such as during system boot may be of a lower quality.
30 /// The default hashing algorithm is currently SipHash 1-3, though this is
31 /// subject to change at any point in the future. While its performance is very
32 /// competitive for medium sized keys, other hashing algorithms will outperform
33 /// it for small keys such as integers as well as large keys such as long
34 /// strings, though those algorithms will typically *not* protect against
35 /// attacks such as HashDoS.
37 /// The hashing algorithm can be replaced on a per-`HashMap` basis using the
38 /// [`default`], [`with_hasher`], and [`with_capacity_and_hasher`] methods.
39 /// There are many alternative [hashing algorithms available on crates.io].
41 /// It is required that the keys implement the [`Eq`] and [`Hash`] traits, although
42 /// this can frequently be achieved by using `#[derive(PartialEq, Eq, Hash)]`.
43 /// If you implement these yourself, it is important that the following
47 /// k1 == k2 -> hash(k1) == hash(k2)
50 /// In other words, if two keys are equal, their hashes must be equal.
52 /// It is a logic error for a key to be modified in such a way that the key's
53 /// hash, as determined by the [`Hash`] trait, or its equality, as determined by
54 /// the [`Eq`] trait, changes while it is in the map. This is normally only
55 /// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
56 /// The behavior resulting from such a logic error is not specified, but will
57 /// not result in undefined behavior. This could include panics, incorrect results,
58 /// aborts, memory leaks, and non-termination.
60 /// The hash table implementation is a Rust port of Google's [SwissTable].
61 /// The original C++ version of SwissTable can be found [here], and this
62 /// [CppCon talk] gives an overview of how the algorithm works.
64 /// [hash map]: crate::collections#use-a-hashmap-when
65 /// [hashing algorithms available on crates.io]: https://crates.io/keywords/hasher
66 /// [SwissTable]: https://abseil.io/blog/20180927-swisstables
67 /// [here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h
68 /// [CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4
73 /// use std::collections::HashMap;
75 /// // Type inference lets us omit an explicit type signature (which
76 /// // would be `HashMap<String, String>` in this example).
77 /// let mut book_reviews = HashMap::new();
79 /// // Review some books.
80 /// book_reviews.insert(
81 /// "Adventures of Huckleberry Finn".to_string(),
82 /// "My favorite book.".to_string(),
84 /// book_reviews.insert(
85 /// "Grimms' Fairy Tales".to_string(),
86 /// "Masterpiece.".to_string(),
88 /// book_reviews.insert(
89 /// "Pride and Prejudice".to_string(),
90 /// "Very enjoyable.".to_string(),
92 /// book_reviews.insert(
93 /// "The Adventures of Sherlock Holmes".to_string(),
94 /// "Eye lyked it alot.".to_string(),
97 /// // Check for a specific one.
98 /// // When collections store owned values (String), they can still be
99 /// // queried using references (&str).
100 /// if !book_reviews.contains_key("Les Misérables") {
101 /// println!("We've got {} reviews, but Les Misérables ain't one.",
102 /// book_reviews.len());
105 /// // oops, this review has a lot of spelling mistakes, let's delete it.
106 /// book_reviews.remove("The Adventures of Sherlock Holmes");
108 /// // Look up the values associated with some keys.
109 /// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
110 /// for &book in &to_find {
111 /// match book_reviews.get(book) {
112 /// Some(review) => println!("{}: {}", book, review),
113 /// None => println!("{} is unreviewed.", book)
117 /// // Look up the value for a key (will panic if the key is not found).
118 /// println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);
120 /// // Iterate over everything.
121 /// for (book, review) in &book_reviews {
122 /// println!("{}: \"{}\"", book, review);
126 /// A `HashMap` with a known list of items can be initialized from an array:
129 /// use std::collections::HashMap;
131 /// let solar_distance = HashMap::from([
132 /// ("Mercury", 0.4),
139 /// `HashMap` implements an [`Entry API`](#method.entry), which allows
140 /// for complex methods of getting, setting, updating and removing keys and
144 /// use std::collections::HashMap;
146 /// // type inference lets us omit an explicit type signature (which
147 /// // would be `HashMap<&str, u8>` in this example).
148 /// let mut player_stats = HashMap::new();
150 /// fn random_stat_buff() -> u8 {
151 /// // could actually return some random value here - let's just return
152 /// // some fixed value for now
156 /// // insert a key only if it doesn't already exist
157 /// player_stats.entry("health").or_insert(100);
159 /// // insert a key using a function that provides a new value only if it
160 /// // doesn't already exist
161 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
163 /// // update a key, guarding against the key possibly not being set
164 /// let stat = player_stats.entry("attack").or_insert(100);
165 /// *stat += random_stat_buff();
168 /// The easiest way to use `HashMap` with a custom key type is to derive [`Eq`] and [`Hash`].
169 /// We must also derive [`PartialEq`].
171 /// [`RefCell`]: crate::cell::RefCell
172 /// [`Cell`]: crate::cell::Cell
173 /// [`default`]: Default::default
174 /// [`with_hasher`]: Self::with_hasher
175 /// [`with_capacity_and_hasher`]: Self::with_capacity_and_hasher
178 /// use std::collections::HashMap;
180 /// #[derive(Hash, Eq, PartialEq, Debug)]
187 /// /// Creates a new Viking.
188 /// fn new(name: &str, country: &str) -> Viking {
189 /// Viking { name: name.to_string(), country: country.to_string() }
193 /// // Use a HashMap to store the vikings' health points.
194 /// let vikings = HashMap::from([
195 /// (Viking::new("Einar", "Norway"), 25),
196 /// (Viking::new("Olaf", "Denmark"), 24),
197 /// (Viking::new("Harald", "Iceland"), 12),
200 /// // Use derived implementation to print the status of the vikings.
201 /// for (viking, health) in &vikings {
202 /// println!("{:?} has {} hp", viking, health);
206 #[cfg_attr(not(test), rustc_diagnostic_item = "HashMap")]
207 #[stable(feature = "rust1", since = "1.0.0")]
208 #[rustc_insignificant_dtor]
209 pub struct HashMap<K, V, S = RandomState> {
210 base: base::HashMap<K, V, S>,
213 impl<K, V> HashMap<K, V, RandomState> {
214 /// Creates an empty `HashMap`.
216 /// The hash map is initially created with a capacity of 0, so it will not allocate until it
217 /// is first inserted into.
222 /// use std::collections::HashMap;
223 /// let mut map: HashMap<&str, i32> = HashMap::new();
227 #[stable(feature = "rust1", since = "1.0.0")]
228 pub fn new() -> HashMap<K, V, RandomState> {
232 /// Creates an empty `HashMap` with the specified capacity.
234 /// The hash map will be able to hold at least `capacity` elements without
235 /// reallocating. If `capacity` is 0, the hash map will not allocate.
240 /// use std::collections::HashMap;
241 /// let mut map: HashMap<&str, i32> = HashMap::with_capacity(10);
245 #[stable(feature = "rust1", since = "1.0.0")]
246 pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState> {
247 HashMap::with_capacity_and_hasher(capacity, Default::default())
251 impl<K, V, S> HashMap<K, V, S> {
252 /// Creates an empty `HashMap` which will use the given hash builder to hash
255 /// The created map has the default initial capacity.
257 /// Warning: `hash_builder` is normally randomly generated, and
258 /// is designed to allow HashMaps to be resistant to attacks that
259 /// cause many collisions and very poor performance. Setting it
260 /// manually using this function can expose a DoS attack vector.
262 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
263 /// the HashMap to be useful, see its documentation for details.
268 /// use std::collections::HashMap;
269 /// use std::collections::hash_map::RandomState;
271 /// let s = RandomState::new();
272 /// let mut map = HashMap::with_hasher(s);
273 /// map.insert(1, 2);
276 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
277 pub fn with_hasher(hash_builder: S) -> HashMap<K, V, S> {
278 HashMap { base: base::HashMap::with_hasher(hash_builder) }
281 /// Creates an empty `HashMap` with the specified capacity, using `hash_builder`
282 /// to hash the keys.
284 /// The hash map will be able to hold at least `capacity` elements without
285 /// reallocating. If `capacity` is 0, the hash map will not allocate.
287 /// Warning: `hash_builder` is normally randomly generated, and
288 /// is designed to allow HashMaps to be resistant to attacks that
289 /// cause many collisions and very poor performance. Setting it
290 /// manually using this function can expose a DoS attack vector.
292 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
293 /// the HashMap to be useful, see its documentation for details.
298 /// use std::collections::HashMap;
299 /// use std::collections::hash_map::RandomState;
301 /// let s = RandomState::new();
302 /// let mut map = HashMap::with_capacity_and_hasher(10, s);
303 /// map.insert(1, 2);
306 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
307 pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> HashMap<K, V, S> {
308 HashMap { base: base::HashMap::with_capacity_and_hasher(capacity, hash_builder) }
311 /// Returns the number of elements the map can hold without reallocating.
313 /// This number is a lower bound; the `HashMap<K, V>` might be able to hold
314 /// more, but is guaranteed to be able to hold at least this many.
319 /// use std::collections::HashMap;
320 /// let map: HashMap<i32, i32> = HashMap::with_capacity(100);
321 /// assert!(map.capacity() >= 100);
324 #[stable(feature = "rust1", since = "1.0.0")]
325 pub fn capacity(&self) -> usize {
329 /// An iterator visiting all keys in arbitrary order.
330 /// The iterator element type is `&'a K`.
335 /// use std::collections::HashMap;
337 /// let map = HashMap::from([
343 /// for key in map.keys() {
344 /// println!("{}", key);
347 #[stable(feature = "rust1", since = "1.0.0")]
348 pub fn keys(&self) -> Keys<'_, K, V> {
349 Keys { inner: self.iter() }
352 /// An iterator visiting all values in arbitrary order.
353 /// The iterator element type is `&'a V`.
358 /// use std::collections::HashMap;
360 /// let map = HashMap::from([
366 /// for val in map.values() {
367 /// println!("{}", val);
370 #[stable(feature = "rust1", since = "1.0.0")]
371 pub fn values(&self) -> Values<'_, K, V> {
372 Values { inner: self.iter() }
375 /// An iterator visiting all values mutably in arbitrary order.
376 /// The iterator element type is `&'a mut V`.
381 /// use std::collections::HashMap;
383 /// let mut map = HashMap::from([
389 /// for val in map.values_mut() {
390 /// *val = *val + 10;
393 /// for val in map.values() {
394 /// println!("{}", val);
397 #[stable(feature = "map_values_mut", since = "1.10.0")]
398 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
399 ValuesMut { inner: self.iter_mut() }
402 /// An iterator visiting all key-value pairs in arbitrary order.
403 /// The iterator element type is `(&'a K, &'a V)`.
408 /// use std::collections::HashMap;
410 /// let map = HashMap::from([
416 /// for (key, val) in map.iter() {
417 /// println!("key: {} val: {}", key, val);
420 #[stable(feature = "rust1", since = "1.0.0")]
421 pub fn iter(&self) -> Iter<'_, K, V> {
422 Iter { base: self.base.iter() }
425 /// An iterator visiting all key-value pairs in arbitrary order,
426 /// with mutable references to the values.
427 /// The iterator element type is `(&'a K, &'a mut V)`.
432 /// use std::collections::HashMap;
434 /// let mut map = HashMap::from([
440 /// // Update all values
441 /// for (_, val) in map.iter_mut() {
445 /// for (key, val) in &map {
446 /// println!("key: {} val: {}", key, val);
449 #[stable(feature = "rust1", since = "1.0.0")]
450 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
451 IterMut { base: self.base.iter_mut() }
454 /// Returns the number of elements in the map.
459 /// use std::collections::HashMap;
461 /// let mut a = HashMap::new();
462 /// assert_eq!(a.len(), 0);
463 /// a.insert(1, "a");
464 /// assert_eq!(a.len(), 1);
466 #[stable(feature = "rust1", since = "1.0.0")]
467 pub fn len(&self) -> usize {
471 /// Returns `true` if the map contains no elements.
476 /// use std::collections::HashMap;
478 /// let mut a = HashMap::new();
479 /// assert!(a.is_empty());
480 /// a.insert(1, "a");
481 /// assert!(!a.is_empty());
484 #[stable(feature = "rust1", since = "1.0.0")]
485 pub fn is_empty(&self) -> bool {
489 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
490 /// allocated memory for reuse.
495 /// use std::collections::HashMap;
497 /// let mut a = HashMap::new();
498 /// a.insert(1, "a");
499 /// a.insert(2, "b");
501 /// for (k, v) in a.drain().take(1) {
502 /// assert!(k == 1 || k == 2);
503 /// assert!(v == "a" || v == "b");
506 /// assert!(a.is_empty());
509 #[stable(feature = "drain", since = "1.6.0")]
510 pub fn drain(&mut self) -> Drain<'_, K, V> {
511 Drain { base: self.base.drain() }
514 /// Creates an iterator which uses a closure to determine if an element should be removed.
516 /// If the closure returns true, the element is removed from the map and yielded.
517 /// If the closure returns false, or panics, the element remains in the map and will not be
520 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
521 /// whether you choose to keep or remove it.
523 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
524 /// elements will still be subjected to the closure and removed and dropped if it returns true.
526 /// It is unspecified how many more elements will be subjected to the closure
527 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
528 /// or if the `DrainFilter` value is leaked.
532 /// Splitting a map into even and odd keys, reusing the original map:
535 /// #![feature(hash_drain_filter)]
536 /// use std::collections::HashMap;
538 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
539 /// let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();
541 /// let mut evens = drained.keys().copied().collect::<Vec<_>>();
542 /// let mut odds = map.keys().copied().collect::<Vec<_>>();
546 /// assert_eq!(evens, vec![0, 2, 4, 6]);
547 /// assert_eq!(odds, vec![1, 3, 5, 7]);
550 #[unstable(feature = "hash_drain_filter", issue = "59618")]
551 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
553 F: FnMut(&K, &mut V) -> bool,
555 DrainFilter { base: self.base.drain_filter(pred) }
558 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
564 /// use std::collections::HashMap;
566 /// let mut a = HashMap::new();
567 /// a.insert(1, "a");
569 /// assert!(a.is_empty());
572 #[stable(feature = "rust1", since = "1.0.0")]
573 pub fn clear(&mut self) {
577 /// Returns a reference to the map's [`BuildHasher`].
582 /// use std::collections::HashMap;
583 /// use std::collections::hash_map::RandomState;
585 /// let hasher = RandomState::new();
586 /// let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
587 /// let hasher: &RandomState = map.hasher();
590 #[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
591 pub fn hasher(&self) -> &S {
596 impl<K, V, S> HashMap<K, V, S>
601 /// Reserves capacity for at least `additional` more elements to be inserted
602 /// in the `HashMap`. The collection may reserve more space to avoid
603 /// frequent reallocations.
607 /// Panics if the new allocation size overflows [`usize`].
612 /// use std::collections::HashMap;
613 /// let mut map: HashMap<&str, i32> = HashMap::new();
617 #[stable(feature = "rust1", since = "1.0.0")]
618 pub fn reserve(&mut self, additional: usize) {
619 self.base.reserve(additional)
622 /// Tries to reserve capacity for at least `additional` more elements to be inserted
623 /// in the given `HashMap<K, V>`. The collection may reserve more space to avoid
624 /// frequent reallocations.
628 /// If the capacity overflows, or the allocator reports a failure, then an error
634 /// use std::collections::HashMap;
636 /// let mut map: HashMap<&str, isize> = HashMap::new();
637 /// map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
640 #[stable(feature = "try_reserve", since = "1.57.0")]
641 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
642 self.base.try_reserve(additional).map_err(map_try_reserve_error)
645 /// Shrinks the capacity of the map as much as possible. It will drop
646 /// down as much as possible while maintaining the internal rules
647 /// and possibly leaving some space in accordance with the resize policy.
652 /// use std::collections::HashMap;
654 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
655 /// map.insert(1, 2);
656 /// map.insert(3, 4);
657 /// assert!(map.capacity() >= 100);
658 /// map.shrink_to_fit();
659 /// assert!(map.capacity() >= 2);
662 #[stable(feature = "rust1", since = "1.0.0")]
663 pub fn shrink_to_fit(&mut self) {
664 self.base.shrink_to_fit();
667 /// Shrinks the capacity of the map with a lower limit. It will drop
668 /// down no lower than the supplied limit while maintaining the internal rules
669 /// and possibly leaving some space in accordance with the resize policy.
671 /// If the current capacity is less than the lower limit, this is a no-op.
676 /// use std::collections::HashMap;
678 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
679 /// map.insert(1, 2);
680 /// map.insert(3, 4);
681 /// assert!(map.capacity() >= 100);
682 /// map.shrink_to(10);
683 /// assert!(map.capacity() >= 10);
684 /// map.shrink_to(0);
685 /// assert!(map.capacity() >= 2);
688 #[stable(feature = "shrink_to", since = "1.56.0")]
689 pub fn shrink_to(&mut self, min_capacity: usize) {
690 self.base.shrink_to(min_capacity);
693 /// Gets the given key's corresponding entry in the map for in-place manipulation.
698 /// use std::collections::HashMap;
700 /// let mut letters = HashMap::new();
702 /// for ch in "a short treatise on fungi".chars() {
703 /// let counter = letters.entry(ch).or_insert(0);
707 /// assert_eq!(letters[&'s'], 2);
708 /// assert_eq!(letters[&'t'], 3);
709 /// assert_eq!(letters[&'u'], 1);
710 /// assert_eq!(letters.get(&'y'), None);
713 #[stable(feature = "rust1", since = "1.0.0")]
714 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
715 map_entry(self.base.rustc_entry(key))
718 /// Returns a reference to the value corresponding to the key.
720 /// The key may be any borrowed form of the map's key type, but
721 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
727 /// use std::collections::HashMap;
729 /// let mut map = HashMap::new();
730 /// map.insert(1, "a");
731 /// assert_eq!(map.get(&1), Some(&"a"));
732 /// assert_eq!(map.get(&2), None);
734 #[stable(feature = "rust1", since = "1.0.0")]
736 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
744 /// Returns the key-value pair corresponding to the supplied key.
746 /// The supplied key may be any borrowed form of the map's key type, but
747 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
753 /// use std::collections::HashMap;
755 /// let mut map = HashMap::new();
756 /// map.insert(1, "a");
757 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
758 /// assert_eq!(map.get_key_value(&2), None);
761 #[stable(feature = "map_get_key_value", since = "1.40.0")]
762 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
767 self.base.get_key_value(k)
770 /// Returns `true` if the map contains a value for the specified key.
772 /// The key may be any borrowed form of the map's key type, but
773 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
779 /// use std::collections::HashMap;
781 /// let mut map = HashMap::new();
782 /// map.insert(1, "a");
783 /// assert_eq!(map.contains_key(&1), true);
784 /// assert_eq!(map.contains_key(&2), false);
787 #[stable(feature = "rust1", since = "1.0.0")]
788 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
793 self.base.contains_key(k)
796 /// Returns a mutable reference to the value corresponding to the key.
798 /// The key may be any borrowed form of the map's key type, but
799 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
805 /// use std::collections::HashMap;
807 /// let mut map = HashMap::new();
808 /// map.insert(1, "a");
809 /// if let Some(x) = map.get_mut(&1) {
812 /// assert_eq!(map[&1], "b");
815 #[stable(feature = "rust1", since = "1.0.0")]
816 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
824 /// Inserts a key-value pair into the map.
826 /// If the map did not have this key present, [`None`] is returned.
828 /// If the map did have this key present, the value is updated, and the old
829 /// value is returned. The key is not updated, though; this matters for
830 /// types that can be `==` without being identical. See the [module-level
831 /// documentation] for more.
833 /// [module-level documentation]: crate::collections#insert-and-complex-keys
838 /// use std::collections::HashMap;
840 /// let mut map = HashMap::new();
841 /// assert_eq!(map.insert(37, "a"), None);
842 /// assert_eq!(map.is_empty(), false);
844 /// map.insert(37, "b");
845 /// assert_eq!(map.insert(37, "c"), Some("b"));
846 /// assert_eq!(map[&37], "c");
849 #[stable(feature = "rust1", since = "1.0.0")]
850 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
851 self.base.insert(k, v)
854 /// Tries to insert a key-value pair into the map, and returns
855 /// a mutable reference to the value in the entry.
857 /// If the map already had this key present, nothing is updated, and
858 /// an error containing the occupied entry and the value is returned.
865 /// #![feature(map_try_insert)]
867 /// use std::collections::HashMap;
869 /// let mut map = HashMap::new();
870 /// assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
872 /// let err = map.try_insert(37, "b").unwrap_err();
873 /// assert_eq!(err.entry.key(), &37);
874 /// assert_eq!(err.entry.get(), &"a");
875 /// assert_eq!(err.value, "b");
877 #[unstable(feature = "map_try_insert", issue = "82766")]
878 pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>> {
879 match self.entry(key) {
880 Occupied(entry) => Err(OccupiedError { entry, value }),
881 Vacant(entry) => Ok(entry.insert(value)),
885 /// Removes a key from the map, returning the value at the key if the key
886 /// was previously in the map.
888 /// The key may be any borrowed form of the map's key type, but
889 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
895 /// use std::collections::HashMap;
897 /// let mut map = HashMap::new();
898 /// map.insert(1, "a");
899 /// assert_eq!(map.remove(&1), Some("a"));
900 /// assert_eq!(map.remove(&1), None);
903 #[stable(feature = "rust1", since = "1.0.0")]
904 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
912 /// Removes a key from the map, returning the stored key and value if the
913 /// key was previously in the map.
915 /// The key may be any borrowed form of the map's key type, but
916 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
922 /// use std::collections::HashMap;
925 /// let mut map = HashMap::new();
926 /// map.insert(1, "a");
927 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
928 /// assert_eq!(map.remove(&1), None);
932 #[stable(feature = "hash_map_remove_entry", since = "1.27.0")]
933 pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)>
938 self.base.remove_entry(k)
941 /// Retains only the elements specified by the predicate.
943 /// In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.
944 /// The elements are visited in unsorted (and unspecified) order.
949 /// use std::collections::HashMap;
951 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
952 /// map.retain(|&k, _| k % 2 == 0);
953 /// assert_eq!(map.len(), 4);
956 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
957 pub fn retain<F>(&mut self, f: F)
959 F: FnMut(&K, &mut V) -> bool,
964 /// Creates a consuming iterator visiting all the keys in arbitrary order.
965 /// The map cannot be used after calling this.
966 /// The iterator element type is `K`.
971 /// use std::collections::HashMap;
973 /// let map = HashMap::from([
979 /// let mut vec: Vec<&str> = map.into_keys().collect();
980 /// // The `IntoKeys` iterator produces keys in arbitrary order, so the
981 /// // keys must be sorted to test them against a sorted array.
982 /// vec.sort_unstable();
983 /// assert_eq!(vec, ["a", "b", "c"]);
986 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
987 pub fn into_keys(self) -> IntoKeys<K, V> {
988 IntoKeys { inner: self.into_iter() }
991 /// Creates a consuming iterator visiting all the values in arbitrary order.
992 /// The map cannot be used after calling this.
993 /// The iterator element type is `V`.
998 /// use std::collections::HashMap;
1000 /// let map = HashMap::from([
1006 /// let mut vec: Vec<i32> = map.into_values().collect();
1007 /// // The `IntoValues` iterator produces values in arbitrary order, so
1008 /// // the values must be sorted to test them against a sorted array.
1009 /// vec.sort_unstable();
1010 /// assert_eq!(vec, [1, 2, 3]);
1013 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1014 pub fn into_values(self) -> IntoValues<K, V> {
1015 IntoValues { inner: self.into_iter() }
1019 impl<K, V, S> HashMap<K, V, S>
1023 /// Creates a raw entry builder for the HashMap.
1025 /// Raw entries provide the lowest level of control for searching and
1026 /// manipulating a map. They must be manually initialized with a hash and
1027 /// then manually searched. After this, insertions into a vacant entry
1028 /// still require an owned key to be provided.
1030 /// Raw entries are useful for such exotic situations as:
1032 /// * Hash memoization
1033 /// * Deferring the creation of an owned key until it is known to be required
1034 /// * Using a search key that doesn't work with the Borrow trait
1035 /// * Using custom comparison logic without newtype wrappers
1037 /// Because raw entries provide much more low-level control, it's much easier
1038 /// to put the HashMap into an inconsistent state which, while memory-safe,
1039 /// will cause the map to produce seemingly random results. Higher-level and
1040 /// more foolproof APIs like `entry` should be preferred when possible.
1042 /// In particular, the hash used to initialized the raw entry must still be
1043 /// consistent with the hash of the key that is ultimately stored in the entry.
1044 /// This is because implementations of HashMap may need to recompute hashes
1045 /// when resizing, at which point only the keys are available.
1047 /// Raw entries give mutable access to the keys. This must not be used
1048 /// to modify how the key would compare or hash, as the map will not re-evaluate
1049 /// where the key should go, meaning the keys may become "lost" if their
1050 /// location does not reflect their state. For instance, if you change a key
1051 /// so that the map now contains keys which compare equal, search may start
1052 /// acting erratically, with two keys randomly masking each other. Implementations
1053 /// are free to assume this doesn't happen (within the limits of memory-safety).
1055 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1056 pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S> {
1057 RawEntryBuilderMut { map: self }
1060 /// Creates a raw immutable entry builder for the HashMap.
1062 /// Raw entries provide the lowest level of control for searching and
1063 /// manipulating a map. They must be manually initialized with a hash and
1064 /// then manually searched.
1066 /// This is useful for
1067 /// * Hash memoization
1068 /// * Using a search key that doesn't work with the Borrow trait
1069 /// * Using custom comparison logic without newtype wrappers
1071 /// Unless you are in such a situation, higher-level and more foolproof APIs like
1072 /// `get` should be preferred.
1074 /// Immutable raw entries have very limited use; you might instead want `raw_entry_mut`.
1076 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1077 pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S> {
1078 RawEntryBuilder { map: self }
1082 #[stable(feature = "rust1", since = "1.0.0")]
1083 impl<K, V, S> Clone for HashMap<K, V, S>
1090 fn clone(&self) -> Self {
1091 Self { base: self.base.clone() }
1095 fn clone_from(&mut self, other: &Self) {
1096 self.base.clone_from(&other.base);
1100 #[stable(feature = "rust1", since = "1.0.0")]
1101 impl<K, V, S> PartialEq for HashMap<K, V, S>
1107 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1108 if self.len() != other.len() {
1112 self.iter().all(|(key, value)| other.get(key).map_or(false, |v| *value == *v))
1116 #[stable(feature = "rust1", since = "1.0.0")]
1117 impl<K, V, S> Eq for HashMap<K, V, S>
1125 #[stable(feature = "rust1", since = "1.0.0")]
1126 impl<K, V, S> Debug for HashMap<K, V, S>
1131 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1132 f.debug_map().entries(self.iter()).finish()
1136 #[stable(feature = "rust1", since = "1.0.0")]
1137 impl<K, V, S> Default for HashMap<K, V, S>
1141 /// Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.
1143 fn default() -> HashMap<K, V, S> {
1144 HashMap::with_hasher(Default::default())
1148 #[stable(feature = "rust1", since = "1.0.0")]
1149 impl<K, Q: ?Sized, V, S> Index<&Q> for HashMap<K, V, S>
1151 K: Eq + Hash + Borrow<Q>,
1157 /// Returns a reference to the value corresponding to the supplied key.
1161 /// Panics if the key is not present in the `HashMap`.
1163 fn index(&self, key: &Q) -> &V {
1164 self.get(key).expect("no entry found for key")
1168 #[stable(feature = "std_collections_from_array", since = "1.56.0")]
1169 // Note: as what is currently the most convenient built-in way to construct
1170 // a HashMap, a simple usage of this function must not *require* the user
1171 // to provide a type annotation in order to infer the third type parameter
1172 // (the hasher parameter, conventionally "S").
1173 // To that end, this impl is defined using RandomState as the concrete
1174 // type of S, rather than being generic over `S: BuildHasher + Default`.
1175 // It is expected that users who want to specify a hasher will manually use
1176 // `with_capacity_and_hasher`.
1177 // If type parameter defaults worked on impls, and if type parameter
1178 // defaults could be mixed with const generics, then perhaps
1179 // this could be generalized.
1180 // See also the equivalent impl on HashSet.
1181 impl<K, V, const N: usize> From<[(K, V); N]> for HashMap<K, V, RandomState>
1188 /// use std::collections::HashMap;
1190 /// let map1 = HashMap::from([(1, 2), (3, 4)]);
1191 /// let map2: HashMap<_, _> = [(1, 2), (3, 4)].into();
1192 /// assert_eq!(map1, map2);
1194 fn from(arr: [(K, V); N]) -> Self {
1195 Self::from_iter(arr)
1199 /// An iterator over the entries of a `HashMap`.
1201 /// This `struct` is created by the [`iter`] method on [`HashMap`]. See its
1202 /// documentation for more.
1204 /// [`iter`]: HashMap::iter
1209 /// use std::collections::HashMap;
1211 /// let map = HashMap::from([
1214 /// let iter = map.iter();
1216 #[stable(feature = "rust1", since = "1.0.0")]
1217 pub struct Iter<'a, K: 'a, V: 'a> {
1218 base: base::Iter<'a, K, V>,
1221 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1222 #[stable(feature = "rust1", since = "1.0.0")]
1223 impl<K, V> Clone for Iter<'_, K, V> {
1225 fn clone(&self) -> Self {
1226 Iter { base: self.base.clone() }
1230 #[stable(feature = "std_debug", since = "1.16.0")]
1231 impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
1232 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1233 f.debug_list().entries(self.clone()).finish()
1237 /// A mutable iterator over the entries of a `HashMap`.
1239 /// This `struct` is created by the [`iter_mut`] method on [`HashMap`]. See its
1240 /// documentation for more.
1242 /// [`iter_mut`]: HashMap::iter_mut
1247 /// use std::collections::HashMap;
1249 /// let mut map = HashMap::from([
1252 /// let iter = map.iter_mut();
1254 #[stable(feature = "rust1", since = "1.0.0")]
1255 pub struct IterMut<'a, K: 'a, V: 'a> {
1256 base: base::IterMut<'a, K, V>,
1259 impl<'a, K, V> IterMut<'a, K, V> {
1260 /// Returns an iterator of references over the remaining items.
1262 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1263 Iter { base: self.base.rustc_iter() }
1267 /// An owning iterator over the entries of a `HashMap`.
1269 /// This `struct` is created by the [`into_iter`] method on [`HashMap`]
1270 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
1272 /// [`into_iter`]: IntoIterator::into_iter
1273 /// [`IntoIterator`]: crate::iter::IntoIterator
1278 /// use std::collections::HashMap;
1280 /// let map = HashMap::from([
1283 /// let iter = map.into_iter();
1285 #[stable(feature = "rust1", since = "1.0.0")]
1286 pub struct IntoIter<K, V> {
1287 base: base::IntoIter<K, V>,
1290 impl<K, V> IntoIter<K, V> {
1291 /// Returns an iterator of references over the remaining items.
1293 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1294 Iter { base: self.base.rustc_iter() }
1298 /// An iterator over the keys of a `HashMap`.
1300 /// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
1301 /// documentation for more.
1303 /// [`keys`]: HashMap::keys
1308 /// use std::collections::HashMap;
1310 /// let map = HashMap::from([
1313 /// let iter_keys = map.keys();
1315 #[stable(feature = "rust1", since = "1.0.0")]
1316 pub struct Keys<'a, K: 'a, V: 'a> {
1317 inner: Iter<'a, K, V>,
1320 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1321 #[stable(feature = "rust1", since = "1.0.0")]
1322 impl<K, V> Clone for Keys<'_, K, V> {
1324 fn clone(&self) -> Self {
1325 Keys { inner: self.inner.clone() }
1329 #[stable(feature = "std_debug", since = "1.16.0")]
1330 impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
1331 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1332 f.debug_list().entries(self.clone()).finish()
1336 /// An iterator over the values of a `HashMap`.
1338 /// This `struct` is created by the [`values`] method on [`HashMap`]. See its
1339 /// documentation for more.
1341 /// [`values`]: HashMap::values
1346 /// use std::collections::HashMap;
1348 /// let map = HashMap::from([
1351 /// let iter_values = map.values();
1353 #[stable(feature = "rust1", since = "1.0.0")]
1354 pub struct Values<'a, K: 'a, V: 'a> {
1355 inner: Iter<'a, K, V>,
1358 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1359 #[stable(feature = "rust1", since = "1.0.0")]
1360 impl<K, V> Clone for Values<'_, K, V> {
1362 fn clone(&self) -> Self {
1363 Values { inner: self.inner.clone() }
1367 #[stable(feature = "std_debug", since = "1.16.0")]
1368 impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
1369 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1370 f.debug_list().entries(self.clone()).finish()
1374 /// A draining iterator over the entries of a `HashMap`.
1376 /// This `struct` is created by the [`drain`] method on [`HashMap`]. See its
1377 /// documentation for more.
1379 /// [`drain`]: HashMap::drain
1384 /// use std::collections::HashMap;
1386 /// let mut map = HashMap::from([
1389 /// let iter = map.drain();
1391 #[stable(feature = "drain", since = "1.6.0")]
1392 pub struct Drain<'a, K: 'a, V: 'a> {
1393 base: base::Drain<'a, K, V>,
1396 impl<'a, K, V> Drain<'a, K, V> {
1397 /// Returns an iterator of references over the remaining items.
1399 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1400 Iter { base: self.base.rustc_iter() }
1404 /// A draining, filtering iterator over the entries of a `HashMap`.
1406 /// This `struct` is created by the [`drain_filter`] method on [`HashMap`].
1408 /// [`drain_filter`]: HashMap::drain_filter
1413 /// #![feature(hash_drain_filter)]
1415 /// use std::collections::HashMap;
1417 /// let mut map = HashMap::from([
1420 /// let iter = map.drain_filter(|_k, v| *v % 2 == 0);
1422 #[unstable(feature = "hash_drain_filter", issue = "59618")]
1423 pub struct DrainFilter<'a, K, V, F>
1425 F: FnMut(&K, &mut V) -> bool,
1427 base: base::DrainFilter<'a, K, V, F>,
1430 /// A mutable iterator over the values of a `HashMap`.
1432 /// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
1433 /// documentation for more.
1435 /// [`values_mut`]: HashMap::values_mut
1440 /// use std::collections::HashMap;
1442 /// let mut map = HashMap::from([
1445 /// let iter_values = map.values_mut();
1447 #[stable(feature = "map_values_mut", since = "1.10.0")]
1448 pub struct ValuesMut<'a, K: 'a, V: 'a> {
1449 inner: IterMut<'a, K, V>,
1452 /// An owning iterator over the keys of a `HashMap`.
1454 /// This `struct` is created by the [`into_keys`] method on [`HashMap`].
1455 /// See its documentation for more.
1457 /// [`into_keys`]: HashMap::into_keys
1462 /// use std::collections::HashMap;
1464 /// let map = HashMap::from([
1467 /// let iter_keys = map.into_keys();
1469 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1470 pub struct IntoKeys<K, V> {
1471 inner: IntoIter<K, V>,
1474 /// An owning iterator over the values of a `HashMap`.
1476 /// This `struct` is created by the [`into_values`] method on [`HashMap`].
1477 /// See its documentation for more.
1479 /// [`into_values`]: HashMap::into_values
1484 /// use std::collections::HashMap;
1486 /// let map = HashMap::from([
1489 /// let iter_keys = map.into_values();
1491 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1492 pub struct IntoValues<K, V> {
1493 inner: IntoIter<K, V>,
1496 /// A builder for computing where in a HashMap a key-value pair would be stored.
1498 /// See the [`HashMap::raw_entry_mut`] docs for usage examples.
1499 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1500 pub struct RawEntryBuilderMut<'a, K: 'a, V: 'a, S: 'a> {
1501 map: &'a mut HashMap<K, V, S>,
1504 /// A view into a single entry in a map, which may either be vacant or occupied.
1506 /// This is a lower-level version of [`Entry`].
1508 /// This `enum` is constructed through the [`raw_entry_mut`] method on [`HashMap`],
1509 /// then calling one of the methods of that [`RawEntryBuilderMut`].
1511 /// [`raw_entry_mut`]: HashMap::raw_entry_mut
1512 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1513 pub enum RawEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1514 /// An occupied entry.
1515 Occupied(RawOccupiedEntryMut<'a, K, V, S>),
1517 Vacant(RawVacantEntryMut<'a, K, V, S>),
1520 /// A view into an occupied entry in a `HashMap`.
1521 /// It is part of the [`RawEntryMut`] enum.
1522 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1523 pub struct RawOccupiedEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1524 base: base::RawOccupiedEntryMut<'a, K, V, S>,
1527 /// A view into a vacant entry in a `HashMap`.
1528 /// It is part of the [`RawEntryMut`] enum.
1529 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1530 pub struct RawVacantEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1531 base: base::RawVacantEntryMut<'a, K, V, S>,
1534 /// A builder for computing where in a HashMap a key-value pair would be stored.
1536 /// See the [`HashMap::raw_entry`] docs for usage examples.
1537 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1538 pub struct RawEntryBuilder<'a, K: 'a, V: 'a, S: 'a> {
1539 map: &'a HashMap<K, V, S>,
1542 impl<'a, K, V, S> RawEntryBuilderMut<'a, K, V, S>
1546 /// Creates a `RawEntryMut` from the given key.
1548 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1549 pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S>
1554 map_raw_entry(self.map.base.raw_entry_mut().from_key(k))
1557 /// Creates a `RawEntryMut` from the given key and its hash.
1559 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1560 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> RawEntryMut<'a, K, V, S>
1565 map_raw_entry(self.map.base.raw_entry_mut().from_key_hashed_nocheck(hash, k))
1568 /// Creates a `RawEntryMut` from the given hash.
1570 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1571 pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S>
1573 for<'b> F: FnMut(&'b K) -> bool,
1575 map_raw_entry(self.map.base.raw_entry_mut().from_hash(hash, is_match))
1579 impl<'a, K, V, S> RawEntryBuilder<'a, K, V, S>
1583 /// Access an entry by key.
1585 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1586 pub fn from_key<Q: ?Sized>(self, k: &Q) -> Option<(&'a K, &'a V)>
1591 self.map.base.raw_entry().from_key(k)
1594 /// Access an entry by a key and its hash.
1596 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1597 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> Option<(&'a K, &'a V)>
1602 self.map.base.raw_entry().from_key_hashed_nocheck(hash, k)
1605 /// Access an entry by hash.
1607 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1608 pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>
1610 F: FnMut(&K) -> bool,
1612 self.map.base.raw_entry().from_hash(hash, is_match)
1616 impl<'a, K, V, S> RawEntryMut<'a, K, V, S> {
1617 /// Ensures a value is in the entry by inserting the default if empty, and returns
1618 /// mutable references to the key and value in the entry.
1623 /// #![feature(hash_raw_entry)]
1624 /// use std::collections::HashMap;
1626 /// let mut map: HashMap<&str, u32> = HashMap::new();
1628 /// map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 3);
1629 /// assert_eq!(map["poneyland"], 3);
1631 /// *map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 10).1 *= 2;
1632 /// assert_eq!(map["poneyland"], 6);
1635 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1636 pub fn or_insert(self, default_key: K, default_val: V) -> (&'a mut K, &'a mut V)
1642 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1643 RawEntryMut::Vacant(entry) => entry.insert(default_key, default_val),
1647 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1648 /// and returns mutable references to the key and value in the entry.
1653 /// #![feature(hash_raw_entry)]
1654 /// use std::collections::HashMap;
1656 /// let mut map: HashMap<&str, String> = HashMap::new();
1658 /// map.raw_entry_mut().from_key("poneyland").or_insert_with(|| {
1659 /// ("poneyland", "hoho".to_string())
1662 /// assert_eq!(map["poneyland"], "hoho".to_string());
1665 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1666 pub fn or_insert_with<F>(self, default: F) -> (&'a mut K, &'a mut V)
1668 F: FnOnce() -> (K, V),
1673 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1674 RawEntryMut::Vacant(entry) => {
1675 let (k, v) = default();
1681 /// Provides in-place mutable access to an occupied entry before any
1682 /// potential inserts into the map.
1687 /// #![feature(hash_raw_entry)]
1688 /// use std::collections::HashMap;
1690 /// let mut map: HashMap<&str, u32> = HashMap::new();
1692 /// map.raw_entry_mut()
1693 /// .from_key("poneyland")
1694 /// .and_modify(|_k, v| { *v += 1 })
1695 /// .or_insert("poneyland", 42);
1696 /// assert_eq!(map["poneyland"], 42);
1698 /// map.raw_entry_mut()
1699 /// .from_key("poneyland")
1700 /// .and_modify(|_k, v| { *v += 1 })
1701 /// .or_insert("poneyland", 0);
1702 /// assert_eq!(map["poneyland"], 43);
1705 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1706 pub fn and_modify<F>(self, f: F) -> Self
1708 F: FnOnce(&mut K, &mut V),
1711 RawEntryMut::Occupied(mut entry) => {
1713 let (k, v) = entry.get_key_value_mut();
1716 RawEntryMut::Occupied(entry)
1718 RawEntryMut::Vacant(entry) => RawEntryMut::Vacant(entry),
1723 impl<'a, K, V, S> RawOccupiedEntryMut<'a, K, V, S> {
1724 /// Gets a reference to the key in the entry.
1727 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1728 pub fn key(&self) -> &K {
1732 /// Gets a mutable reference to the key in the entry.
1735 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1736 pub fn key_mut(&mut self) -> &mut K {
1740 /// Converts the entry into a mutable reference to the key in the entry
1741 /// with a lifetime bound to the map itself.
1743 #[must_use = "`self` will be dropped if the result is not used"]
1744 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1745 pub fn into_key(self) -> &'a mut K {
1746 self.base.into_key()
1749 /// Gets a reference to the value in the entry.
1752 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1753 pub fn get(&self) -> &V {
1757 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
1758 /// with a lifetime bound to the map itself.
1760 #[must_use = "`self` will be dropped if the result is not used"]
1761 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1762 pub fn into_mut(self) -> &'a mut V {
1763 self.base.into_mut()
1766 /// Gets a mutable reference to the value in the entry.
1769 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1770 pub fn get_mut(&mut self) -> &mut V {
1774 /// Gets a reference to the key and value in the entry.
1777 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1778 pub fn get_key_value(&mut self) -> (&K, &V) {
1779 self.base.get_key_value()
1782 /// Gets a mutable reference to the key and value in the entry.
1784 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1785 pub fn get_key_value_mut(&mut self) -> (&mut K, &mut V) {
1786 self.base.get_key_value_mut()
1789 /// Converts the `OccupiedEntry` into a mutable reference to the key and value in the entry
1790 /// with a lifetime bound to the map itself.
1792 #[must_use = "`self` will be dropped if the result is not used"]
1793 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1794 pub fn into_key_value(self) -> (&'a mut K, &'a mut V) {
1795 self.base.into_key_value()
1798 /// Sets the value of the entry, and returns the entry's old value.
1800 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1801 pub fn insert(&mut self, value: V) -> V {
1802 self.base.insert(value)
1805 /// Sets the value of the entry, and returns the entry's old value.
1807 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1808 pub fn insert_key(&mut self, key: K) -> K {
1809 self.base.insert_key(key)
1812 /// Takes the value out of the entry, and returns it.
1814 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1815 pub fn remove(self) -> V {
1819 /// Take the ownership of the key and value from the map.
1821 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1822 pub fn remove_entry(self) -> (K, V) {
1823 self.base.remove_entry()
1827 impl<'a, K, V, S> RawVacantEntryMut<'a, K, V, S> {
1828 /// Sets the value of the entry with the `VacantEntry`'s key,
1829 /// and returns a mutable reference to it.
1831 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1832 pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
1837 self.base.insert(key, value)
1840 /// Sets the value of the entry with the VacantEntry's key,
1841 /// and returns a mutable reference to it.
1843 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1844 pub fn insert_hashed_nocheck(self, hash: u64, key: K, value: V) -> (&'a mut K, &'a mut V)
1849 self.base.insert_hashed_nocheck(hash, key, value)
1853 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1854 impl<K, V, S> Debug for RawEntryBuilderMut<'_, K, V, S> {
1855 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1856 f.debug_struct("RawEntryBuilder").finish_non_exhaustive()
1860 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1861 impl<K: Debug, V: Debug, S> Debug for RawEntryMut<'_, K, V, S> {
1862 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1864 RawEntryMut::Vacant(ref v) => f.debug_tuple("RawEntry").field(v).finish(),
1865 RawEntryMut::Occupied(ref o) => f.debug_tuple("RawEntry").field(o).finish(),
1870 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1871 impl<K: Debug, V: Debug, S> Debug for RawOccupiedEntryMut<'_, K, V, S> {
1872 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1873 f.debug_struct("RawOccupiedEntryMut")
1874 .field("key", self.key())
1875 .field("value", self.get())
1876 .finish_non_exhaustive()
1880 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1881 impl<K, V, S> Debug for RawVacantEntryMut<'_, K, V, S> {
1882 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1883 f.debug_struct("RawVacantEntryMut").finish_non_exhaustive()
1887 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1888 impl<K, V, S> Debug for RawEntryBuilder<'_, K, V, S> {
1889 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1890 f.debug_struct("RawEntryBuilder").finish_non_exhaustive()
1894 /// A view into a single entry in a map, which may either be vacant or occupied.
1896 /// This `enum` is constructed from the [`entry`] method on [`HashMap`].
1898 /// [`entry`]: HashMap::entry
1899 #[stable(feature = "rust1", since = "1.0.0")]
1900 #[cfg_attr(not(test), rustc_diagnostic_item = "HashMapEntry")]
1901 pub enum Entry<'a, K: 'a, V: 'a> {
1902 /// An occupied entry.
1903 #[stable(feature = "rust1", since = "1.0.0")]
1904 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
1907 #[stable(feature = "rust1", since = "1.0.0")]
1908 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
1911 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1912 impl<K: Debug, V: Debug> Debug for Entry<'_, K, V> {
1913 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1915 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
1916 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
1921 /// A view into an occupied entry in a `HashMap`.
1922 /// It is part of the [`Entry`] enum.
1923 #[stable(feature = "rust1", since = "1.0.0")]
1924 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1925 base: base::RustcOccupiedEntry<'a, K, V>,
1928 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1929 impl<K: Debug, V: Debug> Debug for OccupiedEntry<'_, K, V> {
1930 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1931 f.debug_struct("OccupiedEntry")
1932 .field("key", self.key())
1933 .field("value", self.get())
1934 .finish_non_exhaustive()
1938 /// A view into a vacant entry in a `HashMap`.
1939 /// It is part of the [`Entry`] enum.
1940 #[stable(feature = "rust1", since = "1.0.0")]
1941 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1942 base: base::RustcVacantEntry<'a, K, V>,
1945 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1946 impl<K: Debug, V> Debug for VacantEntry<'_, K, V> {
1947 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1948 f.debug_tuple("VacantEntry").field(self.key()).finish()
1952 /// The error returned by [`try_insert`](HashMap::try_insert) when the key already exists.
1954 /// Contains the occupied entry, and the value that was not inserted.
1955 #[unstable(feature = "map_try_insert", issue = "82766")]
1956 pub struct OccupiedError<'a, K: 'a, V: 'a> {
1957 /// The entry in the map that was already occupied.
1958 pub entry: OccupiedEntry<'a, K, V>,
1959 /// The value which was not inserted, because the entry was already occupied.
1963 #[unstable(feature = "map_try_insert", issue = "82766")]
1964 impl<K: Debug, V: Debug> Debug for OccupiedError<'_, K, V> {
1965 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1966 f.debug_struct("OccupiedError")
1967 .field("key", self.entry.key())
1968 .field("old_value", self.entry.get())
1969 .field("new_value", &self.value)
1970 .finish_non_exhaustive()
1974 #[unstable(feature = "map_try_insert", issue = "82766")]
1975 impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V> {
1976 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1979 "failed to insert {:?}, key {:?} already exists with value {:?}",
1987 #[stable(feature = "rust1", since = "1.0.0")]
1988 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> {
1989 type Item = (&'a K, &'a V);
1990 type IntoIter = Iter<'a, K, V>;
1993 fn into_iter(self) -> Iter<'a, K, V> {
1998 #[stable(feature = "rust1", since = "1.0.0")]
1999 impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S> {
2000 type Item = (&'a K, &'a mut V);
2001 type IntoIter = IterMut<'a, K, V>;
2004 fn into_iter(self) -> IterMut<'a, K, V> {
2009 #[stable(feature = "rust1", since = "1.0.0")]
2010 impl<K, V, S> IntoIterator for HashMap<K, V, S> {
2012 type IntoIter = IntoIter<K, V>;
2014 /// Creates a consuming iterator, that is, one that moves each key-value
2015 /// pair out of the map in arbitrary order. The map cannot be used after
2021 /// use std::collections::HashMap;
2023 /// let map = HashMap::from([
2029 /// // Not possible with .iter()
2030 /// let vec: Vec<(&str, i32)> = map.into_iter().collect();
2033 fn into_iter(self) -> IntoIter<K, V> {
2034 IntoIter { base: self.base.into_iter() }
2038 #[stable(feature = "rust1", since = "1.0.0")]
2039 impl<'a, K, V> Iterator for Iter<'a, K, V> {
2040 type Item = (&'a K, &'a V);
2043 fn next(&mut self) -> Option<(&'a K, &'a V)> {
2047 fn size_hint(&self) -> (usize, Option<usize>) {
2048 self.base.size_hint()
2051 #[stable(feature = "rust1", since = "1.0.0")]
2052 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
2054 fn len(&self) -> usize {
2059 #[stable(feature = "fused", since = "1.26.0")]
2060 impl<K, V> FusedIterator for Iter<'_, K, V> {}
2062 #[stable(feature = "rust1", since = "1.0.0")]
2063 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
2064 type Item = (&'a K, &'a mut V);
2067 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
2071 fn size_hint(&self) -> (usize, Option<usize>) {
2072 self.base.size_hint()
2075 #[stable(feature = "rust1", since = "1.0.0")]
2076 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
2078 fn len(&self) -> usize {
2082 #[stable(feature = "fused", since = "1.26.0")]
2083 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
2085 #[stable(feature = "std_debug", since = "1.16.0")]
2086 impl<K, V> fmt::Debug for IterMut<'_, K, V>
2091 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2092 f.debug_list().entries(self.iter()).finish()
2096 #[stable(feature = "rust1", since = "1.0.0")]
2097 impl<K, V> Iterator for IntoIter<K, V> {
2101 fn next(&mut self) -> Option<(K, V)> {
2105 fn size_hint(&self) -> (usize, Option<usize>) {
2106 self.base.size_hint()
2109 #[stable(feature = "rust1", since = "1.0.0")]
2110 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
2112 fn len(&self) -> usize {
2116 #[stable(feature = "fused", since = "1.26.0")]
2117 impl<K, V> FusedIterator for IntoIter<K, V> {}
2119 #[stable(feature = "std_debug", since = "1.16.0")]
2120 impl<K: Debug, V: Debug> fmt::Debug for IntoIter<K, V> {
2121 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2122 f.debug_list().entries(self.iter()).finish()
2126 #[stable(feature = "rust1", since = "1.0.0")]
2127 impl<'a, K, V> Iterator for Keys<'a, K, V> {
2131 fn next(&mut self) -> Option<&'a K> {
2132 self.inner.next().map(|(k, _)| k)
2135 fn size_hint(&self) -> (usize, Option<usize>) {
2136 self.inner.size_hint()
2139 #[stable(feature = "rust1", since = "1.0.0")]
2140 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
2142 fn len(&self) -> usize {
2146 #[stable(feature = "fused", since = "1.26.0")]
2147 impl<K, V> FusedIterator for Keys<'_, K, V> {}
2149 #[stable(feature = "rust1", since = "1.0.0")]
2150 impl<'a, K, V> Iterator for Values<'a, K, V> {
2154 fn next(&mut self) -> Option<&'a V> {
2155 self.inner.next().map(|(_, v)| v)
2158 fn size_hint(&self) -> (usize, Option<usize>) {
2159 self.inner.size_hint()
2162 #[stable(feature = "rust1", since = "1.0.0")]
2163 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
2165 fn len(&self) -> usize {
2169 #[stable(feature = "fused", since = "1.26.0")]
2170 impl<K, V> FusedIterator for Values<'_, K, V> {}
2172 #[stable(feature = "map_values_mut", since = "1.10.0")]
2173 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
2174 type Item = &'a mut V;
2177 fn next(&mut self) -> Option<&'a mut V> {
2178 self.inner.next().map(|(_, v)| v)
2181 fn size_hint(&self) -> (usize, Option<usize>) {
2182 self.inner.size_hint()
2185 #[stable(feature = "map_values_mut", since = "1.10.0")]
2186 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
2188 fn len(&self) -> usize {
2192 #[stable(feature = "fused", since = "1.26.0")]
2193 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
2195 #[stable(feature = "std_debug", since = "1.16.0")]
2196 impl<K, V: fmt::Debug> fmt::Debug for ValuesMut<'_, K, V> {
2197 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2198 f.debug_list().entries(self.inner.iter().map(|(_, val)| val)).finish()
2202 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2203 impl<K, V> Iterator for IntoKeys<K, V> {
2207 fn next(&mut self) -> Option<K> {
2208 self.inner.next().map(|(k, _)| k)
2211 fn size_hint(&self) -> (usize, Option<usize>) {
2212 self.inner.size_hint()
2215 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2216 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
2218 fn len(&self) -> usize {
2222 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2223 impl<K, V> FusedIterator for IntoKeys<K, V> {}
2225 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2226 impl<K: Debug, V> fmt::Debug for IntoKeys<K, V> {
2227 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2228 f.debug_list().entries(self.inner.iter().map(|(k, _)| k)).finish()
2232 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2233 impl<K, V> Iterator for IntoValues<K, V> {
2237 fn next(&mut self) -> Option<V> {
2238 self.inner.next().map(|(_, v)| v)
2241 fn size_hint(&self) -> (usize, Option<usize>) {
2242 self.inner.size_hint()
2245 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2246 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
2248 fn len(&self) -> usize {
2252 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2253 impl<K, V> FusedIterator for IntoValues<K, V> {}
2255 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2256 impl<K, V: Debug> fmt::Debug for IntoValues<K, V> {
2257 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2258 f.debug_list().entries(self.inner.iter().map(|(_, v)| v)).finish()
2262 #[stable(feature = "drain", since = "1.6.0")]
2263 impl<'a, K, V> Iterator for Drain<'a, K, V> {
2267 fn next(&mut self) -> Option<(K, V)> {
2271 fn size_hint(&self) -> (usize, Option<usize>) {
2272 self.base.size_hint()
2275 #[stable(feature = "drain", since = "1.6.0")]
2276 impl<K, V> ExactSizeIterator for Drain<'_, K, V> {
2278 fn len(&self) -> usize {
2282 #[stable(feature = "fused", since = "1.26.0")]
2283 impl<K, V> FusedIterator for Drain<'_, K, V> {}
2285 #[stable(feature = "std_debug", since = "1.16.0")]
2286 impl<K, V> fmt::Debug for Drain<'_, K, V>
2291 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2292 f.debug_list().entries(self.iter()).finish()
2296 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2297 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
2299 F: FnMut(&K, &mut V) -> bool,
2304 fn next(&mut self) -> Option<(K, V)> {
2308 fn size_hint(&self) -> (usize, Option<usize>) {
2309 self.base.size_hint()
2313 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2314 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
2316 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2317 impl<'a, K, V, F> fmt::Debug for DrainFilter<'a, K, V, F>
2319 F: FnMut(&K, &mut V) -> bool,
2321 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2322 f.debug_struct("DrainFilter").finish_non_exhaustive()
2326 impl<'a, K, V> Entry<'a, K, V> {
2327 /// Ensures a value is in the entry by inserting the default if empty, and returns
2328 /// a mutable reference to the value in the entry.
2333 /// use std::collections::HashMap;
2335 /// let mut map: HashMap<&str, u32> = HashMap::new();
2337 /// map.entry("poneyland").or_insert(3);
2338 /// assert_eq!(map["poneyland"], 3);
2340 /// *map.entry("poneyland").or_insert(10) *= 2;
2341 /// assert_eq!(map["poneyland"], 6);
2344 #[stable(feature = "rust1", since = "1.0.0")]
2345 pub fn or_insert(self, default: V) -> &'a mut V {
2347 Occupied(entry) => entry.into_mut(),
2348 Vacant(entry) => entry.insert(default),
2352 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2353 /// and returns a mutable reference to the value in the entry.
2358 /// use std::collections::HashMap;
2360 /// let mut map: HashMap<&str, String> = HashMap::new();
2361 /// let s = "hoho".to_string();
2363 /// map.entry("poneyland").or_insert_with(|| s);
2365 /// assert_eq!(map["poneyland"], "hoho".to_string());
2368 #[stable(feature = "rust1", since = "1.0.0")]
2369 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2371 Occupied(entry) => entry.into_mut(),
2372 Vacant(entry) => entry.insert(default()),
2376 /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
2377 /// This method allows for generating key-derived values for insertion by providing the default
2378 /// function a reference to the key that was moved during the `.entry(key)` method call.
2380 /// The reference to the moved key is provided so that cloning or copying the key is
2381 /// unnecessary, unlike with `.or_insert_with(|| ... )`.
2386 /// use std::collections::HashMap;
2388 /// let mut map: HashMap<&str, usize> = HashMap::new();
2390 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2392 /// assert_eq!(map["poneyland"], 9);
2395 #[stable(feature = "or_insert_with_key", since = "1.50.0")]
2396 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2398 Occupied(entry) => entry.into_mut(),
2400 let value = default(entry.key());
2406 /// Returns a reference to this entry's key.
2411 /// use std::collections::HashMap;
2413 /// let mut map: HashMap<&str, u32> = HashMap::new();
2414 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2417 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2418 pub fn key(&self) -> &K {
2420 Occupied(ref entry) => entry.key(),
2421 Vacant(ref entry) => entry.key(),
2425 /// Provides in-place mutable access to an occupied entry before any
2426 /// potential inserts into the map.
2431 /// use std::collections::HashMap;
2433 /// let mut map: HashMap<&str, u32> = HashMap::new();
2435 /// map.entry("poneyland")
2436 /// .and_modify(|e| { *e += 1 })
2438 /// assert_eq!(map["poneyland"], 42);
2440 /// map.entry("poneyland")
2441 /// .and_modify(|e| { *e += 1 })
2443 /// assert_eq!(map["poneyland"], 43);
2446 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2447 pub fn and_modify<F>(self, f: F) -> Self
2452 Occupied(mut entry) => {
2456 Vacant(entry) => Vacant(entry),
2460 /// Sets the value of the entry, and returns an `OccupiedEntry`.
2465 /// #![feature(entry_insert)]
2466 /// use std::collections::HashMap;
2468 /// let mut map: HashMap<&str, String> = HashMap::new();
2469 /// let entry = map.entry("poneyland").insert("hoho".to_string());
2471 /// assert_eq!(entry.key(), &"poneyland");
2474 #[unstable(feature = "entry_insert", issue = "65225")]
2475 pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V> {
2477 Occupied(mut entry) => {
2478 entry.insert(value);
2481 Vacant(entry) => entry.insert_entry(value),
2486 impl<'a, K, V: Default> Entry<'a, K, V> {
2487 /// Ensures a value is in the entry by inserting the default value if empty,
2488 /// and returns a mutable reference to the value in the entry.
2494 /// use std::collections::HashMap;
2496 /// let mut map: HashMap<&str, Option<u32>> = HashMap::new();
2497 /// map.entry("poneyland").or_default();
2499 /// assert_eq!(map["poneyland"], None);
2503 #[stable(feature = "entry_or_default", since = "1.28.0")]
2504 pub fn or_default(self) -> &'a mut V {
2506 Occupied(entry) => entry.into_mut(),
2507 Vacant(entry) => entry.insert(Default::default()),
2512 impl<'a, K, V> OccupiedEntry<'a, K, V> {
2513 /// Gets a reference to the key in the entry.
2518 /// use std::collections::HashMap;
2520 /// let mut map: HashMap<&str, u32> = HashMap::new();
2521 /// map.entry("poneyland").or_insert(12);
2522 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2525 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2526 pub fn key(&self) -> &K {
2530 /// Take the ownership of the key and value from the map.
2535 /// use std::collections::HashMap;
2536 /// use std::collections::hash_map::Entry;
2538 /// let mut map: HashMap<&str, u32> = HashMap::new();
2539 /// map.entry("poneyland").or_insert(12);
2541 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2542 /// // We delete the entry from the map.
2543 /// o.remove_entry();
2546 /// assert_eq!(map.contains_key("poneyland"), false);
2549 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2550 pub fn remove_entry(self) -> (K, V) {
2551 self.base.remove_entry()
2554 /// Gets a reference to the value in the entry.
2559 /// use std::collections::HashMap;
2560 /// use std::collections::hash_map::Entry;
2562 /// let mut map: HashMap<&str, u32> = HashMap::new();
2563 /// map.entry("poneyland").or_insert(12);
2565 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2566 /// assert_eq!(o.get(), &12);
2570 #[stable(feature = "rust1", since = "1.0.0")]
2571 pub fn get(&self) -> &V {
2575 /// Gets a mutable reference to the value in the entry.
2577 /// If you need a reference to the `OccupiedEntry` which may outlive the
2578 /// destruction of the `Entry` value, see [`into_mut`].
2580 /// [`into_mut`]: Self::into_mut
2585 /// use std::collections::HashMap;
2586 /// use std::collections::hash_map::Entry;
2588 /// let mut map: HashMap<&str, u32> = HashMap::new();
2589 /// map.entry("poneyland").or_insert(12);
2591 /// assert_eq!(map["poneyland"], 12);
2592 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2593 /// *o.get_mut() += 10;
2594 /// assert_eq!(*o.get(), 22);
2596 /// // We can use the same Entry multiple times.
2597 /// *o.get_mut() += 2;
2600 /// assert_eq!(map["poneyland"], 24);
2603 #[stable(feature = "rust1", since = "1.0.0")]
2604 pub fn get_mut(&mut self) -> &mut V {
2608 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
2609 /// with a lifetime bound to the map itself.
2611 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2613 /// [`get_mut`]: Self::get_mut
2618 /// use std::collections::HashMap;
2619 /// use std::collections::hash_map::Entry;
2621 /// let mut map: HashMap<&str, u32> = HashMap::new();
2622 /// map.entry("poneyland").or_insert(12);
2624 /// assert_eq!(map["poneyland"], 12);
2625 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2626 /// *o.into_mut() += 10;
2629 /// assert_eq!(map["poneyland"], 22);
2632 #[stable(feature = "rust1", since = "1.0.0")]
2633 pub fn into_mut(self) -> &'a mut V {
2634 self.base.into_mut()
2637 /// Sets the value of the entry, and returns the entry's old value.
2642 /// use std::collections::HashMap;
2643 /// use std::collections::hash_map::Entry;
2645 /// let mut map: HashMap<&str, u32> = HashMap::new();
2646 /// map.entry("poneyland").or_insert(12);
2648 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2649 /// assert_eq!(o.insert(15), 12);
2652 /// assert_eq!(map["poneyland"], 15);
2655 #[stable(feature = "rust1", since = "1.0.0")]
2656 pub fn insert(&mut self, value: V) -> V {
2657 self.base.insert(value)
2660 /// Takes the value out of the entry, and returns it.
2665 /// use std::collections::HashMap;
2666 /// use std::collections::hash_map::Entry;
2668 /// let mut map: HashMap<&str, u32> = HashMap::new();
2669 /// map.entry("poneyland").or_insert(12);
2671 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2672 /// assert_eq!(o.remove(), 12);
2675 /// assert_eq!(map.contains_key("poneyland"), false);
2678 #[stable(feature = "rust1", since = "1.0.0")]
2679 pub fn remove(self) -> V {
2683 /// Replaces the entry, returning the old key and value. The new key in the hash map will be
2684 /// the key used to create this entry.
2689 /// #![feature(map_entry_replace)]
2690 /// use std::collections::hash_map::{Entry, HashMap};
2691 /// use std::rc::Rc;
2693 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2694 /// map.insert(Rc::new("Stringthing".to_string()), 15);
2696 /// let my_key = Rc::new("Stringthing".to_string());
2698 /// if let Entry::Occupied(entry) = map.entry(my_key) {
2699 /// // Also replace the key with a handle to our other key.
2700 /// let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
2705 #[unstable(feature = "map_entry_replace", issue = "44286")]
2706 pub fn replace_entry(self, value: V) -> (K, V) {
2707 self.base.replace_entry(value)
2710 /// Replaces the key in the hash map with the key used to create this entry.
2715 /// #![feature(map_entry_replace)]
2716 /// use std::collections::hash_map::{Entry, HashMap};
2717 /// use std::rc::Rc;
2719 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2720 /// let known_strings: Vec<Rc<String>> = Vec::new();
2722 /// // Initialise known strings, run program, etc.
2724 /// reclaim_memory(&mut map, &known_strings);
2726 /// fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
2727 /// for s in known_strings {
2728 /// if let Entry::Occupied(entry) = map.entry(Rc::clone(s)) {
2729 /// // Replaces the entry's key with our version of it in `known_strings`.
2730 /// entry.replace_key();
2736 #[unstable(feature = "map_entry_replace", issue = "44286")]
2737 pub fn replace_key(self) -> K {
2738 self.base.replace_key()
2742 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
2743 /// Gets a reference to the key that would be used when inserting a value
2744 /// through the `VacantEntry`.
2749 /// use std::collections::HashMap;
2751 /// let mut map: HashMap<&str, u32> = HashMap::new();
2752 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2755 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2756 pub fn key(&self) -> &K {
2760 /// Take ownership of the key.
2765 /// use std::collections::HashMap;
2766 /// use std::collections::hash_map::Entry;
2768 /// let mut map: HashMap<&str, u32> = HashMap::new();
2770 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2775 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2776 pub fn into_key(self) -> K {
2777 self.base.into_key()
2780 /// Sets the value of the entry with the `VacantEntry`'s key,
2781 /// and returns a mutable reference to it.
2786 /// use std::collections::HashMap;
2787 /// use std::collections::hash_map::Entry;
2789 /// let mut map: HashMap<&str, u32> = HashMap::new();
2791 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2794 /// assert_eq!(map["poneyland"], 37);
2797 #[stable(feature = "rust1", since = "1.0.0")]
2798 pub fn insert(self, value: V) -> &'a mut V {
2799 self.base.insert(value)
2802 /// Sets the value of the entry with the `VacantEntry`'s key,
2803 /// and returns an `OccupiedEntry`.
2808 /// use std::collections::HashMap;
2809 /// use std::collections::hash_map::Entry;
2811 /// let mut map: HashMap<&str, u32> = HashMap::new();
2813 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2816 /// assert_eq!(map["poneyland"], 37);
2819 fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> {
2820 let base = self.base.insert_entry(value);
2821 OccupiedEntry { base }
2825 #[stable(feature = "rust1", since = "1.0.0")]
2826 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
2829 S: BuildHasher + Default,
2831 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> HashMap<K, V, S> {
2832 let mut map = HashMap::with_hasher(Default::default());
2838 /// Inserts all new key-values from the iterator and replaces values with existing
2839 /// keys with new values returned from the iterator.
2840 #[stable(feature = "rust1", since = "1.0.0")]
2841 impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>
2847 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
2848 self.base.extend(iter)
2852 fn extend_one(&mut self, (k, v): (K, V)) {
2853 self.base.insert(k, v);
2857 fn extend_reserve(&mut self, additional: usize) {
2858 self.base.extend_reserve(additional);
2862 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
2863 impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>
2865 K: Eq + Hash + Copy,
2870 fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T) {
2871 self.base.extend(iter)
2875 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2876 self.base.insert(k, v);
2880 fn extend_reserve(&mut self, additional: usize) {
2881 Extend::<(K, V)>::extend_reserve(self, additional)
2885 /// `RandomState` is the default state for [`HashMap`] types.
2887 /// A particular instance `RandomState` will create the same instances of
2888 /// [`Hasher`], but the hashers created by two different `RandomState`
2889 /// instances are unlikely to produce the same result for the same values.
2894 /// use std::collections::HashMap;
2895 /// use std::collections::hash_map::RandomState;
2897 /// let s = RandomState::new();
2898 /// let mut map = HashMap::with_hasher(s);
2899 /// map.insert(1, 2);
2902 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2903 pub struct RandomState {
2909 /// Constructs a new `RandomState` that is initialized with random keys.
2914 /// use std::collections::hash_map::RandomState;
2916 /// let s = RandomState::new();
2919 #[allow(deprecated)]
2922 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2923 pub fn new() -> RandomState {
2924 // Historically this function did not cache keys from the OS and instead
2925 // simply always called `rand::thread_rng().gen()` twice. In #31356 it
2926 // was discovered, however, that because we re-seed the thread-local RNG
2927 // from the OS periodically that this can cause excessive slowdown when
2928 // many hash maps are created on a thread. To solve this performance
2929 // trap we cache the first set of randomly generated keys per-thread.
2931 // Later in #36481 it was discovered that exposing a deterministic
2932 // iteration order allows a form of DOS attack. To counter that we
2933 // increment one of the seeds on every RandomState creation, giving
2934 // every corresponding HashMap a different iteration order.
2935 thread_local!(static KEYS: Cell<(u64, u64)> = {
2936 Cell::new(sys::hashmap_random_keys())
2940 let (k0, k1) = keys.get();
2941 keys.set((k0.wrapping_add(1), k1));
2942 RandomState { k0, k1 }
2947 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2948 impl BuildHasher for RandomState {
2949 type Hasher = DefaultHasher;
2951 #[allow(deprecated)]
2952 fn build_hasher(&self) -> DefaultHasher {
2953 DefaultHasher(SipHasher13::new_with_keys(self.k0, self.k1))
2957 /// The default [`Hasher`] used by [`RandomState`].
2959 /// The internal algorithm is not specified, and so it and its hashes should
2960 /// not be relied upon over releases.
2961 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2962 #[allow(deprecated)]
2963 #[derive(Clone, Debug)]
2964 pub struct DefaultHasher(SipHasher13);
2966 impl DefaultHasher {
2967 /// Creates a new `DefaultHasher`.
2969 /// This hasher is not guaranteed to be the same as all other
2970 /// `DefaultHasher` instances, but is the same as all other `DefaultHasher`
2971 /// instances created through `new` or `default`.
2972 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2973 #[allow(deprecated)]
2975 pub fn new() -> DefaultHasher {
2976 DefaultHasher(SipHasher13::new_with_keys(0, 0))
2980 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2981 impl Default for DefaultHasher {
2982 /// Creates a new `DefaultHasher` using [`new`].
2983 /// See its documentation for more.
2985 /// [`new`]: DefaultHasher::new
2986 fn default() -> DefaultHasher {
2987 DefaultHasher::new()
2991 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2992 impl Hasher for DefaultHasher {
2994 fn write(&mut self, msg: &[u8]) {
2999 fn finish(&self) -> u64 {
3004 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
3005 impl Default for RandomState {
3006 /// Constructs a new `RandomState`.
3008 fn default() -> RandomState {
3013 #[stable(feature = "std_debug", since = "1.16.0")]
3014 impl fmt::Debug for RandomState {
3015 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3016 f.debug_struct("RandomState").finish_non_exhaustive()
3021 fn map_entry<'a, K: 'a, V: 'a>(raw: base::RustcEntry<'a, K, V>) -> Entry<'a, K, V> {
3023 base::RustcEntry::Occupied(base) => Entry::Occupied(OccupiedEntry { base }),
3024 base::RustcEntry::Vacant(base) => Entry::Vacant(VacantEntry { base }),
3029 pub(super) fn map_try_reserve_error(err: hashbrown::TryReserveError) -> TryReserveError {
3031 hashbrown::TryReserveError::CapacityOverflow => {
3032 TryReserveErrorKind::CapacityOverflow.into()
3034 hashbrown::TryReserveError::AllocError { layout } => {
3035 TryReserveErrorKind::AllocError { layout, non_exhaustive: () }.into()
3041 fn map_raw_entry<'a, K: 'a, V: 'a, S: 'a>(
3042 raw: base::RawEntryMut<'a, K, V, S>,
3043 ) -> RawEntryMut<'a, K, V, S> {
3045 base::RawEntryMut::Occupied(base) => RawEntryMut::Occupied(RawOccupiedEntryMut { base }),
3046 base::RawEntryMut::Vacant(base) => RawEntryMut::Vacant(RawVacantEntryMut { base }),
3051 fn assert_covariance() {
3052 fn map_key<'new>(v: HashMap<&'static str, u8>) -> HashMap<&'new str, u8> {
3055 fn map_val<'new>(v: HashMap<u8, &'static str>) -> HashMap<u8, &'new str> {
3058 fn iter_key<'a, 'new>(v: Iter<'a, &'static str, u8>) -> Iter<'a, &'new str, u8> {
3061 fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
3064 fn into_iter_key<'new>(v: IntoIter<&'static str, u8>) -> IntoIter<&'new str, u8> {
3067 fn into_iter_val<'new>(v: IntoIter<u8, &'static str>) -> IntoIter<u8, &'new str> {
3070 fn keys_key<'a, 'new>(v: Keys<'a, &'static str, u8>) -> Keys<'a, &'new str, u8> {
3073 fn keys_val<'a, 'new>(v: Keys<'a, u8, &'static str>) -> Keys<'a, u8, &'new str> {
3076 fn values_key<'a, 'new>(v: Values<'a, &'static str, u8>) -> Values<'a, &'new str, u8> {
3079 fn values_val<'a, 'new>(v: Values<'a, u8, &'static str>) -> Values<'a, u8, &'new str> {
3083 d: Drain<'static, &'static str, &'static str>,
3084 ) -> Drain<'new, &'new str, &'new str> {