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 mut map = HashMap::new();
338 /// map.insert("a", 1);
339 /// map.insert("b", 2);
340 /// map.insert("c", 3);
342 /// for key in map.keys() {
343 /// println!("{}", key);
346 #[stable(feature = "rust1", since = "1.0.0")]
347 pub fn keys(&self) -> Keys<'_, K, V> {
348 Keys { inner: self.iter() }
351 /// An iterator visiting all values in arbitrary order.
352 /// The iterator element type is `&'a V`.
357 /// use std::collections::HashMap;
359 /// let mut map = HashMap::new();
360 /// map.insert("a", 1);
361 /// map.insert("b", 2);
362 /// map.insert("c", 3);
364 /// for val in map.values() {
365 /// println!("{}", val);
368 #[stable(feature = "rust1", since = "1.0.0")]
369 pub fn values(&self) -> Values<'_, K, V> {
370 Values { inner: self.iter() }
373 /// An iterator visiting all values mutably in arbitrary order.
374 /// The iterator element type is `&'a mut V`.
379 /// use std::collections::HashMap;
381 /// let mut map = HashMap::new();
383 /// map.insert("a", 1);
384 /// map.insert("b", 2);
385 /// map.insert("c", 3);
387 /// for val in map.values_mut() {
388 /// *val = *val + 10;
391 /// for val in map.values() {
392 /// println!("{}", val);
395 #[stable(feature = "map_values_mut", since = "1.10.0")]
396 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
397 ValuesMut { inner: self.iter_mut() }
400 /// An iterator visiting all key-value pairs in arbitrary order.
401 /// The iterator element type is `(&'a K, &'a V)`.
406 /// use std::collections::HashMap;
408 /// let mut map = HashMap::new();
409 /// map.insert("a", 1);
410 /// map.insert("b", 2);
411 /// map.insert("c", 3);
413 /// for (key, val) in map.iter() {
414 /// println!("key: {} val: {}", key, val);
417 #[stable(feature = "rust1", since = "1.0.0")]
418 pub fn iter(&self) -> Iter<'_, K, V> {
419 Iter { base: self.base.iter() }
422 /// An iterator visiting all key-value pairs in arbitrary order,
423 /// with mutable references to the values.
424 /// The iterator element type is `(&'a K, &'a mut V)`.
429 /// use std::collections::HashMap;
431 /// let mut map = HashMap::new();
432 /// map.insert("a", 1);
433 /// map.insert("b", 2);
434 /// map.insert("c", 3);
436 /// // Update all values
437 /// for (_, val) in map.iter_mut() {
441 /// for (key, val) in &map {
442 /// println!("key: {} val: {}", key, val);
445 #[stable(feature = "rust1", since = "1.0.0")]
446 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
447 IterMut { base: self.base.iter_mut() }
450 /// Returns the number of elements in the map.
455 /// use std::collections::HashMap;
457 /// let mut a = HashMap::new();
458 /// assert_eq!(a.len(), 0);
459 /// a.insert(1, "a");
460 /// assert_eq!(a.len(), 1);
462 #[stable(feature = "rust1", since = "1.0.0")]
463 pub fn len(&self) -> usize {
467 /// Returns `true` if the map contains no elements.
472 /// use std::collections::HashMap;
474 /// let mut a = HashMap::new();
475 /// assert!(a.is_empty());
476 /// a.insert(1, "a");
477 /// assert!(!a.is_empty());
480 #[stable(feature = "rust1", since = "1.0.0")]
481 pub fn is_empty(&self) -> bool {
485 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
486 /// allocated memory for reuse.
491 /// use std::collections::HashMap;
493 /// let mut a = HashMap::new();
494 /// a.insert(1, "a");
495 /// a.insert(2, "b");
497 /// for (k, v) in a.drain().take(1) {
498 /// assert!(k == 1 || k == 2);
499 /// assert!(v == "a" || v == "b");
502 /// assert!(a.is_empty());
505 #[stable(feature = "drain", since = "1.6.0")]
506 pub fn drain(&mut self) -> Drain<'_, K, V> {
507 Drain { base: self.base.drain() }
510 /// Creates an iterator which uses a closure to determine if an element should be removed.
512 /// If the closure returns true, the element is removed from the map and yielded.
513 /// If the closure returns false, or panics, the element remains in the map and will not be
516 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
517 /// whether you choose to keep or remove it.
519 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
520 /// elements will still be subjected to the closure and removed and dropped if it returns true.
522 /// It is unspecified how many more elements will be subjected to the closure
523 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
524 /// or if the `DrainFilter` value is leaked.
528 /// Splitting a map into even and odd keys, reusing the original map:
531 /// #![feature(hash_drain_filter)]
532 /// use std::collections::HashMap;
534 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
535 /// let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();
537 /// let mut evens = drained.keys().copied().collect::<Vec<_>>();
538 /// let mut odds = map.keys().copied().collect::<Vec<_>>();
542 /// assert_eq!(evens, vec![0, 2, 4, 6]);
543 /// assert_eq!(odds, vec![1, 3, 5, 7]);
546 #[unstable(feature = "hash_drain_filter", issue = "59618")]
547 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
549 F: FnMut(&K, &mut V) -> bool,
551 DrainFilter { base: self.base.drain_filter(pred) }
554 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
560 /// use std::collections::HashMap;
562 /// let mut a = HashMap::new();
563 /// a.insert(1, "a");
565 /// assert!(a.is_empty());
568 #[stable(feature = "rust1", since = "1.0.0")]
569 pub fn clear(&mut self) {
573 /// Returns a reference to the map's [`BuildHasher`].
578 /// use std::collections::HashMap;
579 /// use std::collections::hash_map::RandomState;
581 /// let hasher = RandomState::new();
582 /// let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
583 /// let hasher: &RandomState = map.hasher();
586 #[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
587 pub fn hasher(&self) -> &S {
592 impl<K, V, S> HashMap<K, V, S>
597 /// Reserves capacity for at least `additional` more elements to be inserted
598 /// in the `HashMap`. The collection may reserve more space to avoid
599 /// frequent reallocations.
603 /// Panics if the new allocation size overflows [`usize`].
608 /// use std::collections::HashMap;
609 /// let mut map: HashMap<&str, i32> = HashMap::new();
613 #[stable(feature = "rust1", since = "1.0.0")]
614 pub fn reserve(&mut self, additional: usize) {
615 self.base.reserve(additional)
618 /// Tries to reserve capacity for at least `additional` more elements to be inserted
619 /// in the given `HashMap<K, V>`. The collection may reserve more space to avoid
620 /// frequent reallocations.
624 /// If the capacity overflows, or the allocator reports a failure, then an error
630 /// use std::collections::HashMap;
632 /// let mut map: HashMap<&str, isize> = HashMap::new();
633 /// map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
636 #[stable(feature = "try_reserve", since = "1.57.0")]
637 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
638 self.base.try_reserve(additional).map_err(map_try_reserve_error)
641 /// Shrinks the capacity of the map as much as possible. It will drop
642 /// down as much as possible while maintaining the internal rules
643 /// and possibly leaving some space in accordance with the resize policy.
648 /// use std::collections::HashMap;
650 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
651 /// map.insert(1, 2);
652 /// map.insert(3, 4);
653 /// assert!(map.capacity() >= 100);
654 /// map.shrink_to_fit();
655 /// assert!(map.capacity() >= 2);
658 #[stable(feature = "rust1", since = "1.0.0")]
659 pub fn shrink_to_fit(&mut self) {
660 self.base.shrink_to_fit();
663 /// Shrinks the capacity of the map with a lower limit. It will drop
664 /// down no lower than the supplied limit while maintaining the internal rules
665 /// and possibly leaving some space in accordance with the resize policy.
667 /// If the current capacity is less than the lower limit, this is a no-op.
672 /// use std::collections::HashMap;
674 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
675 /// map.insert(1, 2);
676 /// map.insert(3, 4);
677 /// assert!(map.capacity() >= 100);
678 /// map.shrink_to(10);
679 /// assert!(map.capacity() >= 10);
680 /// map.shrink_to(0);
681 /// assert!(map.capacity() >= 2);
684 #[stable(feature = "shrink_to", since = "1.56.0")]
685 pub fn shrink_to(&mut self, min_capacity: usize) {
686 self.base.shrink_to(min_capacity);
689 /// Gets the given key's corresponding entry in the map for in-place manipulation.
694 /// use std::collections::HashMap;
696 /// let mut letters = HashMap::new();
698 /// for ch in "a short treatise on fungi".chars() {
699 /// let counter = letters.entry(ch).or_insert(0);
703 /// assert_eq!(letters[&'s'], 2);
704 /// assert_eq!(letters[&'t'], 3);
705 /// assert_eq!(letters[&'u'], 1);
706 /// assert_eq!(letters.get(&'y'), None);
709 #[stable(feature = "rust1", since = "1.0.0")]
710 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
711 map_entry(self.base.rustc_entry(key))
714 /// Returns a reference to the value corresponding to the key.
716 /// The key may be any borrowed form of the map's key type, but
717 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
723 /// use std::collections::HashMap;
725 /// let mut map = HashMap::new();
726 /// map.insert(1, "a");
727 /// assert_eq!(map.get(&1), Some(&"a"));
728 /// assert_eq!(map.get(&2), None);
730 #[stable(feature = "rust1", since = "1.0.0")]
732 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
740 /// Returns the key-value pair corresponding to the supplied key.
742 /// The supplied key may be any borrowed form of the map's key type, but
743 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
749 /// use std::collections::HashMap;
751 /// let mut map = HashMap::new();
752 /// map.insert(1, "a");
753 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
754 /// assert_eq!(map.get_key_value(&2), None);
757 #[stable(feature = "map_get_key_value", since = "1.40.0")]
758 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
763 self.base.get_key_value(k)
766 /// Returns `true` if the map contains a value for the specified key.
768 /// The key may be any borrowed form of the map's key type, but
769 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
775 /// use std::collections::HashMap;
777 /// let mut map = HashMap::new();
778 /// map.insert(1, "a");
779 /// assert_eq!(map.contains_key(&1), true);
780 /// assert_eq!(map.contains_key(&2), false);
783 #[stable(feature = "rust1", since = "1.0.0")]
784 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
789 self.base.contains_key(k)
792 /// Returns a mutable reference to the value corresponding to the key.
794 /// The key may be any borrowed form of the map's key type, but
795 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
801 /// use std::collections::HashMap;
803 /// let mut map = HashMap::new();
804 /// map.insert(1, "a");
805 /// if let Some(x) = map.get_mut(&1) {
808 /// assert_eq!(map[&1], "b");
811 #[stable(feature = "rust1", since = "1.0.0")]
812 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
820 /// Inserts a key-value pair into the map.
822 /// If the map did not have this key present, [`None`] is returned.
824 /// If the map did have this key present, the value is updated, and the old
825 /// value is returned. The key is not updated, though; this matters for
826 /// types that can be `==` without being identical. See the [module-level
827 /// documentation] for more.
829 /// [module-level documentation]: crate::collections#insert-and-complex-keys
834 /// use std::collections::HashMap;
836 /// let mut map = HashMap::new();
837 /// assert_eq!(map.insert(37, "a"), None);
838 /// assert_eq!(map.is_empty(), false);
840 /// map.insert(37, "b");
841 /// assert_eq!(map.insert(37, "c"), Some("b"));
842 /// assert_eq!(map[&37], "c");
845 #[stable(feature = "rust1", since = "1.0.0")]
846 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
847 self.base.insert(k, v)
850 /// Tries to insert a key-value pair into the map, and returns
851 /// a mutable reference to the value in the entry.
853 /// If the map already had this key present, nothing is updated, and
854 /// an error containing the occupied entry and the value is returned.
861 /// #![feature(map_try_insert)]
863 /// use std::collections::HashMap;
865 /// let mut map = HashMap::new();
866 /// assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
868 /// let err = map.try_insert(37, "b").unwrap_err();
869 /// assert_eq!(err.entry.key(), &37);
870 /// assert_eq!(err.entry.get(), &"a");
871 /// assert_eq!(err.value, "b");
873 #[unstable(feature = "map_try_insert", issue = "82766")]
874 pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>> {
875 match self.entry(key) {
876 Occupied(entry) => Err(OccupiedError { entry, value }),
877 Vacant(entry) => Ok(entry.insert(value)),
881 /// Removes a key from the map, returning the value at the key if the key
882 /// was previously in the map.
884 /// The key may be any borrowed form of the map's key type, but
885 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
891 /// use std::collections::HashMap;
893 /// let mut map = HashMap::new();
894 /// map.insert(1, "a");
895 /// assert_eq!(map.remove(&1), Some("a"));
896 /// assert_eq!(map.remove(&1), None);
899 #[stable(feature = "rust1", since = "1.0.0")]
900 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
908 /// Removes a key from the map, returning the stored key and value if the
909 /// key was previously in the map.
911 /// The key may be any borrowed form of the map's key type, but
912 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
918 /// use std::collections::HashMap;
921 /// let mut map = HashMap::new();
922 /// map.insert(1, "a");
923 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
924 /// assert_eq!(map.remove(&1), None);
928 #[stable(feature = "hash_map_remove_entry", since = "1.27.0")]
929 pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)>
934 self.base.remove_entry(k)
937 /// Retains only the elements specified by the predicate.
939 /// In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.
940 /// The elements are visited in unsorted (and unspecified) order.
945 /// use std::collections::HashMap;
947 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
948 /// map.retain(|&k, _| k % 2 == 0);
949 /// assert_eq!(map.len(), 4);
952 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
953 pub fn retain<F>(&mut self, f: F)
955 F: FnMut(&K, &mut V) -> bool,
960 /// Creates a consuming iterator visiting all the keys in arbitrary order.
961 /// The map cannot be used after calling this.
962 /// The iterator element type is `K`.
967 /// use std::collections::HashMap;
969 /// let mut map = HashMap::new();
970 /// map.insert("a", 1);
971 /// map.insert("b", 2);
972 /// map.insert("c", 3);
974 /// let mut vec: Vec<&str> = map.into_keys().collect();
975 /// // The `IntoKeys` iterator produces keys in arbitrary order, so the
976 /// // keys must be sorted to test them against a sorted array.
977 /// vec.sort_unstable();
978 /// assert_eq!(vec, ["a", "b", "c"]);
981 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
982 pub fn into_keys(self) -> IntoKeys<K, V> {
983 IntoKeys { inner: self.into_iter() }
986 /// Creates a consuming iterator visiting all the values in arbitrary order.
987 /// The map cannot be used after calling this.
988 /// The iterator element type is `V`.
993 /// use std::collections::HashMap;
995 /// let mut map = HashMap::new();
996 /// map.insert("a", 1);
997 /// map.insert("b", 2);
998 /// map.insert("c", 3);
1000 /// let mut vec: Vec<i32> = map.into_values().collect();
1001 /// // The `IntoValues` iterator produces values in arbitrary order, so
1002 /// // the values must be sorted to test them against a sorted array.
1003 /// vec.sort_unstable();
1004 /// assert_eq!(vec, [1, 2, 3]);
1007 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1008 pub fn into_values(self) -> IntoValues<K, V> {
1009 IntoValues { inner: self.into_iter() }
1013 impl<K, V, S> HashMap<K, V, S>
1017 /// Creates a raw entry builder for the HashMap.
1019 /// Raw entries provide the lowest level of control for searching and
1020 /// manipulating a map. They must be manually initialized with a hash and
1021 /// then manually searched. After this, insertions into a vacant entry
1022 /// still require an owned key to be provided.
1024 /// Raw entries are useful for such exotic situations as:
1026 /// * Hash memoization
1027 /// * Deferring the creation of an owned key until it is known to be required
1028 /// * Using a search key that doesn't work with the Borrow trait
1029 /// * Using custom comparison logic without newtype wrappers
1031 /// Because raw entries provide much more low-level control, it's much easier
1032 /// to put the HashMap into an inconsistent state which, while memory-safe,
1033 /// will cause the map to produce seemingly random results. Higher-level and
1034 /// more foolproof APIs like `entry` should be preferred when possible.
1036 /// In particular, the hash used to initialized the raw entry must still be
1037 /// consistent with the hash of the key that is ultimately stored in the entry.
1038 /// This is because implementations of HashMap may need to recompute hashes
1039 /// when resizing, at which point only the keys are available.
1041 /// Raw entries give mutable access to the keys. This must not be used
1042 /// to modify how the key would compare or hash, as the map will not re-evaluate
1043 /// where the key should go, meaning the keys may become "lost" if their
1044 /// location does not reflect their state. For instance, if you change a key
1045 /// so that the map now contains keys which compare equal, search may start
1046 /// acting erratically, with two keys randomly masking each other. Implementations
1047 /// are free to assume this doesn't happen (within the limits of memory-safety).
1049 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1050 pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S> {
1051 RawEntryBuilderMut { map: self }
1054 /// Creates a raw immutable entry builder for the HashMap.
1056 /// Raw entries provide the lowest level of control for searching and
1057 /// manipulating a map. They must be manually initialized with a hash and
1058 /// then manually searched.
1060 /// This is useful for
1061 /// * Hash memoization
1062 /// * Using a search key that doesn't work with the Borrow trait
1063 /// * Using custom comparison logic without newtype wrappers
1065 /// Unless you are in such a situation, higher-level and more foolproof APIs like
1066 /// `get` should be preferred.
1068 /// Immutable raw entries have very limited use; you might instead want `raw_entry_mut`.
1070 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1071 pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S> {
1072 RawEntryBuilder { map: self }
1076 #[stable(feature = "rust1", since = "1.0.0")]
1077 impl<K, V, S> Clone for HashMap<K, V, S>
1084 fn clone(&self) -> Self {
1085 Self { base: self.base.clone() }
1089 fn clone_from(&mut self, other: &Self) {
1090 self.base.clone_from(&other.base);
1094 #[stable(feature = "rust1", since = "1.0.0")]
1095 impl<K, V, S> PartialEq for HashMap<K, V, S>
1101 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1102 if self.len() != other.len() {
1106 self.iter().all(|(key, value)| other.get(key).map_or(false, |v| *value == *v))
1110 #[stable(feature = "rust1", since = "1.0.0")]
1111 impl<K, V, S> Eq for HashMap<K, V, S>
1119 #[stable(feature = "rust1", since = "1.0.0")]
1120 impl<K, V, S> Debug for HashMap<K, V, S>
1125 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1126 f.debug_map().entries(self.iter()).finish()
1130 #[stable(feature = "rust1", since = "1.0.0")]
1131 impl<K, V, S> Default for HashMap<K, V, S>
1135 /// Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.
1137 fn default() -> HashMap<K, V, S> {
1138 HashMap::with_hasher(Default::default())
1142 #[stable(feature = "rust1", since = "1.0.0")]
1143 impl<K, Q: ?Sized, V, S> Index<&Q> for HashMap<K, V, S>
1145 K: Eq + Hash + Borrow<Q>,
1151 /// Returns a reference to the value corresponding to the supplied key.
1155 /// Panics if the key is not present in the `HashMap`.
1157 fn index(&self, key: &Q) -> &V {
1158 self.get(key).expect("no entry found for key")
1162 #[stable(feature = "std_collections_from_array", since = "1.56.0")]
1163 // Note: as what is currently the most convenient built-in way to construct
1164 // a HashMap, a simple usage of this function must not *require* the user
1165 // to provide a type annotation in order to infer the third type parameter
1166 // (the hasher parameter, conventionally "S").
1167 // To that end, this impl is defined using RandomState as the concrete
1168 // type of S, rather than being generic over `S: BuildHasher + Default`.
1169 // It is expected that users who want to specify a hasher will manually use
1170 // `with_capacity_and_hasher`.
1171 // If type parameter defaults worked on impls, and if type parameter
1172 // defaults could be mixed with const generics, then perhaps
1173 // this could be generalized.
1174 // See also the equivalent impl on HashSet.
1175 impl<K, V, const N: usize> From<[(K, V); N]> for HashMap<K, V, RandomState>
1182 /// use std::collections::HashMap;
1184 /// let map1 = HashMap::from([(1, 2), (3, 4)]);
1185 /// let map2: HashMap<_, _> = [(1, 2), (3, 4)].into();
1186 /// assert_eq!(map1, map2);
1188 fn from(arr: [(K, V); N]) -> Self {
1189 crate::array::IntoIter::new(arr).collect()
1193 /// An iterator over the entries of a `HashMap`.
1195 /// This `struct` is created by the [`iter`] method on [`HashMap`]. See its
1196 /// documentation for more.
1198 /// [`iter`]: HashMap::iter
1203 /// use std::collections::HashMap;
1205 /// let mut map = HashMap::new();
1206 /// map.insert("a", 1);
1207 /// let iter = map.iter();
1209 #[stable(feature = "rust1", since = "1.0.0")]
1210 pub struct Iter<'a, K: 'a, V: 'a> {
1211 base: base::Iter<'a, K, V>,
1214 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1215 #[stable(feature = "rust1", since = "1.0.0")]
1216 impl<K, V> Clone for Iter<'_, K, V> {
1218 fn clone(&self) -> Self {
1219 Iter { base: self.base.clone() }
1223 #[stable(feature = "std_debug", since = "1.16.0")]
1224 impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
1225 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1226 f.debug_list().entries(self.clone()).finish()
1230 /// A mutable iterator over the entries of a `HashMap`.
1232 /// This `struct` is created by the [`iter_mut`] method on [`HashMap`]. See its
1233 /// documentation for more.
1235 /// [`iter_mut`]: HashMap::iter_mut
1240 /// use std::collections::HashMap;
1242 /// let mut map = HashMap::new();
1243 /// map.insert("a", 1);
1244 /// let iter = map.iter_mut();
1246 #[stable(feature = "rust1", since = "1.0.0")]
1247 pub struct IterMut<'a, K: 'a, V: 'a> {
1248 base: base::IterMut<'a, K, V>,
1251 impl<'a, K, V> IterMut<'a, K, V> {
1252 /// Returns an iterator of references over the remaining items.
1254 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1255 Iter { base: self.base.rustc_iter() }
1259 /// An owning iterator over the entries of a `HashMap`.
1261 /// This `struct` is created by the [`into_iter`] method on [`HashMap`]
1262 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
1264 /// [`into_iter`]: IntoIterator::into_iter
1265 /// [`IntoIterator`]: crate::iter::IntoIterator
1270 /// use std::collections::HashMap;
1272 /// let mut map = HashMap::new();
1273 /// map.insert("a", 1);
1274 /// let iter = map.into_iter();
1276 #[stable(feature = "rust1", since = "1.0.0")]
1277 pub struct IntoIter<K, V> {
1278 base: base::IntoIter<K, V>,
1281 impl<K, V> IntoIter<K, V> {
1282 /// Returns an iterator of references over the remaining items.
1284 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1285 Iter { base: self.base.rustc_iter() }
1289 /// An iterator over the keys of a `HashMap`.
1291 /// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
1292 /// documentation for more.
1294 /// [`keys`]: HashMap::keys
1299 /// use std::collections::HashMap;
1301 /// let mut map = HashMap::new();
1302 /// map.insert("a", 1);
1303 /// let iter_keys = map.keys();
1305 #[stable(feature = "rust1", since = "1.0.0")]
1306 pub struct Keys<'a, K: 'a, V: 'a> {
1307 inner: Iter<'a, K, V>,
1310 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1311 #[stable(feature = "rust1", since = "1.0.0")]
1312 impl<K, V> Clone for Keys<'_, K, V> {
1314 fn clone(&self) -> Self {
1315 Keys { inner: self.inner.clone() }
1319 #[stable(feature = "std_debug", since = "1.16.0")]
1320 impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
1321 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1322 f.debug_list().entries(self.clone()).finish()
1326 /// An iterator over the values of a `HashMap`.
1328 /// This `struct` is created by the [`values`] method on [`HashMap`]. See its
1329 /// documentation for more.
1331 /// [`values`]: HashMap::values
1336 /// use std::collections::HashMap;
1338 /// let mut map = HashMap::new();
1339 /// map.insert("a", 1);
1340 /// let iter_values = map.values();
1342 #[stable(feature = "rust1", since = "1.0.0")]
1343 pub struct Values<'a, K: 'a, V: 'a> {
1344 inner: Iter<'a, K, V>,
1347 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1348 #[stable(feature = "rust1", since = "1.0.0")]
1349 impl<K, V> Clone for Values<'_, K, V> {
1351 fn clone(&self) -> Self {
1352 Values { inner: self.inner.clone() }
1356 #[stable(feature = "std_debug", since = "1.16.0")]
1357 impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
1358 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1359 f.debug_list().entries(self.clone()).finish()
1363 /// A draining iterator over the entries of a `HashMap`.
1365 /// This `struct` is created by the [`drain`] method on [`HashMap`]. See its
1366 /// documentation for more.
1368 /// [`drain`]: HashMap::drain
1373 /// use std::collections::HashMap;
1375 /// let mut map = HashMap::new();
1376 /// map.insert("a", 1);
1377 /// let iter = map.drain();
1379 #[stable(feature = "drain", since = "1.6.0")]
1380 pub struct Drain<'a, K: 'a, V: 'a> {
1381 base: base::Drain<'a, K, V>,
1384 impl<'a, K, V> Drain<'a, K, V> {
1385 /// Returns an iterator of references over the remaining items.
1387 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1388 Iter { base: self.base.rustc_iter() }
1392 /// A draining, filtering iterator over the entries of a `HashMap`.
1394 /// This `struct` is created by the [`drain_filter`] method on [`HashMap`].
1396 /// [`drain_filter`]: HashMap::drain_filter
1401 /// #![feature(hash_drain_filter)]
1403 /// use std::collections::HashMap;
1405 /// let mut map = HashMap::new();
1406 /// map.insert("a", 1);
1407 /// let iter = map.drain_filter(|_k, v| *v % 2 == 0);
1409 #[unstable(feature = "hash_drain_filter", issue = "59618")]
1410 pub struct DrainFilter<'a, K, V, F>
1412 F: FnMut(&K, &mut V) -> bool,
1414 base: base::DrainFilter<'a, K, V, F>,
1417 /// A mutable iterator over the values of a `HashMap`.
1419 /// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
1420 /// documentation for more.
1422 /// [`values_mut`]: HashMap::values_mut
1427 /// use std::collections::HashMap;
1429 /// let mut map = HashMap::new();
1430 /// map.insert("a", 1);
1431 /// let iter_values = map.values_mut();
1433 #[stable(feature = "map_values_mut", since = "1.10.0")]
1434 pub struct ValuesMut<'a, K: 'a, V: 'a> {
1435 inner: IterMut<'a, K, V>,
1438 /// An owning iterator over the keys of a `HashMap`.
1440 /// This `struct` is created by the [`into_keys`] method on [`HashMap`].
1441 /// See its documentation for more.
1443 /// [`into_keys`]: HashMap::into_keys
1448 /// use std::collections::HashMap;
1450 /// let mut map = HashMap::new();
1451 /// map.insert("a", 1);
1452 /// let iter_keys = map.into_keys();
1454 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1455 pub struct IntoKeys<K, V> {
1456 inner: IntoIter<K, V>,
1459 /// An owning iterator over the values of a `HashMap`.
1461 /// This `struct` is created by the [`into_values`] method on [`HashMap`].
1462 /// See its documentation for more.
1464 /// [`into_values`]: HashMap::into_values
1469 /// use std::collections::HashMap;
1471 /// let mut map = HashMap::new();
1472 /// map.insert("a", 1);
1473 /// let iter_keys = map.into_values();
1475 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
1476 pub struct IntoValues<K, V> {
1477 inner: IntoIter<K, V>,
1480 /// A builder for computing where in a HashMap a key-value pair would be stored.
1482 /// See the [`HashMap::raw_entry_mut`] docs for usage examples.
1483 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1484 pub struct RawEntryBuilderMut<'a, K: 'a, V: 'a, S: 'a> {
1485 map: &'a mut HashMap<K, V, S>,
1488 /// A view into a single entry in a map, which may either be vacant or occupied.
1490 /// This is a lower-level version of [`Entry`].
1492 /// This `enum` is constructed through the [`raw_entry_mut`] method on [`HashMap`],
1493 /// then calling one of the methods of that [`RawEntryBuilderMut`].
1495 /// [`raw_entry_mut`]: HashMap::raw_entry_mut
1496 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1497 pub enum RawEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1498 /// An occupied entry.
1499 Occupied(RawOccupiedEntryMut<'a, K, V, S>),
1501 Vacant(RawVacantEntryMut<'a, K, V, S>),
1504 /// A view into an occupied entry in a `HashMap`.
1505 /// It is part of the [`RawEntryMut`] enum.
1506 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1507 pub struct RawOccupiedEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1508 base: base::RawOccupiedEntryMut<'a, K, V, S>,
1511 /// A view into a vacant entry in a `HashMap`.
1512 /// It is part of the [`RawEntryMut`] enum.
1513 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1514 pub struct RawVacantEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1515 base: base::RawVacantEntryMut<'a, K, V, S>,
1518 /// A builder for computing where in a HashMap a key-value pair would be stored.
1520 /// See the [`HashMap::raw_entry`] docs for usage examples.
1521 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1522 pub struct RawEntryBuilder<'a, K: 'a, V: 'a, S: 'a> {
1523 map: &'a HashMap<K, V, S>,
1526 impl<'a, K, V, S> RawEntryBuilderMut<'a, K, V, S>
1530 /// Creates a `RawEntryMut` from the given key.
1532 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1533 pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S>
1538 map_raw_entry(self.map.base.raw_entry_mut().from_key(k))
1541 /// Creates a `RawEntryMut` from the given key and its hash.
1543 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1544 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> RawEntryMut<'a, K, V, S>
1549 map_raw_entry(self.map.base.raw_entry_mut().from_key_hashed_nocheck(hash, k))
1552 /// Creates a `RawEntryMut` from the given hash.
1554 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1555 pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S>
1557 for<'b> F: FnMut(&'b K) -> bool,
1559 map_raw_entry(self.map.base.raw_entry_mut().from_hash(hash, is_match))
1563 impl<'a, K, V, S> RawEntryBuilder<'a, K, V, S>
1567 /// Access an entry by key.
1569 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1570 pub fn from_key<Q: ?Sized>(self, k: &Q) -> Option<(&'a K, &'a V)>
1575 self.map.base.raw_entry().from_key(k)
1578 /// Access an entry by a key and its hash.
1580 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1581 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> Option<(&'a K, &'a V)>
1586 self.map.base.raw_entry().from_key_hashed_nocheck(hash, k)
1589 /// Access an entry by hash.
1591 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1592 pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>
1594 F: FnMut(&K) -> bool,
1596 self.map.base.raw_entry().from_hash(hash, is_match)
1600 impl<'a, K, V, S> RawEntryMut<'a, K, V, S> {
1601 /// Ensures a value is in the entry by inserting the default if empty, and returns
1602 /// mutable references to the key and value in the entry.
1607 /// #![feature(hash_raw_entry)]
1608 /// use std::collections::HashMap;
1610 /// let mut map: HashMap<&str, u32> = HashMap::new();
1612 /// map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 3);
1613 /// assert_eq!(map["poneyland"], 3);
1615 /// *map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 10).1 *= 2;
1616 /// assert_eq!(map["poneyland"], 6);
1619 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1620 pub fn or_insert(self, default_key: K, default_val: V) -> (&'a mut K, &'a mut V)
1626 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1627 RawEntryMut::Vacant(entry) => entry.insert(default_key, default_val),
1631 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1632 /// and returns mutable references to the key and value in the entry.
1637 /// #![feature(hash_raw_entry)]
1638 /// use std::collections::HashMap;
1640 /// let mut map: HashMap<&str, String> = HashMap::new();
1642 /// map.raw_entry_mut().from_key("poneyland").or_insert_with(|| {
1643 /// ("poneyland", "hoho".to_string())
1646 /// assert_eq!(map["poneyland"], "hoho".to_string());
1649 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1650 pub fn or_insert_with<F>(self, default: F) -> (&'a mut K, &'a mut V)
1652 F: FnOnce() -> (K, V),
1657 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1658 RawEntryMut::Vacant(entry) => {
1659 let (k, v) = default();
1665 /// Provides in-place mutable access to an occupied entry before any
1666 /// potential inserts into the map.
1671 /// #![feature(hash_raw_entry)]
1672 /// use std::collections::HashMap;
1674 /// let mut map: HashMap<&str, u32> = HashMap::new();
1676 /// map.raw_entry_mut()
1677 /// .from_key("poneyland")
1678 /// .and_modify(|_k, v| { *v += 1 })
1679 /// .or_insert("poneyland", 42);
1680 /// assert_eq!(map["poneyland"], 42);
1682 /// map.raw_entry_mut()
1683 /// .from_key("poneyland")
1684 /// .and_modify(|_k, v| { *v += 1 })
1685 /// .or_insert("poneyland", 0);
1686 /// assert_eq!(map["poneyland"], 43);
1689 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1690 pub fn and_modify<F>(self, f: F) -> Self
1692 F: FnOnce(&mut K, &mut V),
1695 RawEntryMut::Occupied(mut entry) => {
1697 let (k, v) = entry.get_key_value_mut();
1700 RawEntryMut::Occupied(entry)
1702 RawEntryMut::Vacant(entry) => RawEntryMut::Vacant(entry),
1707 impl<'a, K, V, S> RawOccupiedEntryMut<'a, K, V, S> {
1708 /// Gets a reference to the key in the entry.
1711 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1712 pub fn key(&self) -> &K {
1716 /// Gets a mutable reference to the key in the entry.
1719 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1720 pub fn key_mut(&mut self) -> &mut K {
1724 /// Converts the entry into a mutable reference to the key in the entry
1725 /// with a lifetime bound to the map itself.
1727 #[must_use = "`self` will be dropped if the result is not used"]
1728 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1729 pub fn into_key(self) -> &'a mut K {
1730 self.base.into_key()
1733 /// Gets a reference to the value in the entry.
1736 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1737 pub fn get(&self) -> &V {
1741 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
1742 /// with a lifetime bound to the map itself.
1744 #[must_use = "`self` will be dropped if the result is not used"]
1745 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1746 pub fn into_mut(self) -> &'a mut V {
1747 self.base.into_mut()
1750 /// Gets a mutable reference to the value in the entry.
1753 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1754 pub fn get_mut(&mut self) -> &mut V {
1758 /// Gets a reference to the key and value in the entry.
1761 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1762 pub fn get_key_value(&mut self) -> (&K, &V) {
1763 self.base.get_key_value()
1766 /// Gets a mutable reference to the key and value in the entry.
1768 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1769 pub fn get_key_value_mut(&mut self) -> (&mut K, &mut V) {
1770 self.base.get_key_value_mut()
1773 /// Converts the `OccupiedEntry` into a mutable reference to the key and value in the entry
1774 /// with a lifetime bound to the map itself.
1776 #[must_use = "`self` will be dropped if the result is not used"]
1777 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1778 pub fn into_key_value(self) -> (&'a mut K, &'a mut V) {
1779 self.base.into_key_value()
1782 /// Sets the value of the entry, and returns the entry's old value.
1784 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1785 pub fn insert(&mut self, value: V) -> V {
1786 self.base.insert(value)
1789 /// Sets the value of the entry, and returns the entry's old value.
1791 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1792 pub fn insert_key(&mut self, key: K) -> K {
1793 self.base.insert_key(key)
1796 /// Takes the value out of the entry, and returns it.
1798 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1799 pub fn remove(self) -> V {
1803 /// Take the ownership of the key and value from the map.
1805 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1806 pub fn remove_entry(self) -> (K, V) {
1807 self.base.remove_entry()
1811 impl<'a, K, V, S> RawVacantEntryMut<'a, K, V, S> {
1812 /// Sets the value of the entry with the `VacantEntry`'s key,
1813 /// and returns a mutable reference to it.
1815 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1816 pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
1821 self.base.insert(key, value)
1824 /// Sets the value of the entry with the VacantEntry's key,
1825 /// and returns a mutable reference to it.
1827 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1828 pub fn insert_hashed_nocheck(self, hash: u64, key: K, value: V) -> (&'a mut K, &'a mut V)
1833 self.base.insert_hashed_nocheck(hash, key, value)
1837 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1838 impl<K, V, S> Debug for RawEntryBuilderMut<'_, K, V, S> {
1839 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1840 f.debug_struct("RawEntryBuilder").finish_non_exhaustive()
1844 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1845 impl<K: Debug, V: Debug, S> Debug for RawEntryMut<'_, K, V, S> {
1846 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1848 RawEntryMut::Vacant(ref v) => f.debug_tuple("RawEntry").field(v).finish(),
1849 RawEntryMut::Occupied(ref o) => f.debug_tuple("RawEntry").field(o).finish(),
1854 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1855 impl<K: Debug, V: Debug, S> Debug for RawOccupiedEntryMut<'_, K, V, S> {
1856 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1857 f.debug_struct("RawOccupiedEntryMut")
1858 .field("key", self.key())
1859 .field("value", self.get())
1860 .finish_non_exhaustive()
1864 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1865 impl<K, V, S> Debug for RawVacantEntryMut<'_, K, V, S> {
1866 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1867 f.debug_struct("RawVacantEntryMut").finish_non_exhaustive()
1871 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1872 impl<K, V, S> Debug for RawEntryBuilder<'_, K, V, S> {
1873 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1874 f.debug_struct("RawEntryBuilder").finish_non_exhaustive()
1878 /// A view into a single entry in a map, which may either be vacant or occupied.
1880 /// This `enum` is constructed from the [`entry`] method on [`HashMap`].
1882 /// [`entry`]: HashMap::entry
1883 #[stable(feature = "rust1", since = "1.0.0")]
1884 #[cfg_attr(not(test), rustc_diagnostic_item = "HashMapEntry")]
1885 pub enum Entry<'a, K: 'a, V: 'a> {
1886 /// An occupied entry.
1887 #[stable(feature = "rust1", since = "1.0.0")]
1888 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
1891 #[stable(feature = "rust1", since = "1.0.0")]
1892 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
1895 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1896 impl<K: Debug, V: Debug> Debug for Entry<'_, K, V> {
1897 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1899 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
1900 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
1905 /// A view into an occupied entry in a `HashMap`.
1906 /// It is part of the [`Entry`] enum.
1907 #[stable(feature = "rust1", since = "1.0.0")]
1908 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1909 base: base::RustcOccupiedEntry<'a, K, V>,
1912 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1913 impl<K: Debug, V: Debug> Debug for OccupiedEntry<'_, K, V> {
1914 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1915 f.debug_struct("OccupiedEntry")
1916 .field("key", self.key())
1917 .field("value", self.get())
1918 .finish_non_exhaustive()
1922 /// A view into a vacant entry in a `HashMap`.
1923 /// It is part of the [`Entry`] enum.
1924 #[stable(feature = "rust1", since = "1.0.0")]
1925 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1926 base: base::RustcVacantEntry<'a, K, V>,
1929 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1930 impl<K: Debug, V> Debug for VacantEntry<'_, K, V> {
1931 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1932 f.debug_tuple("VacantEntry").field(self.key()).finish()
1936 /// The error returned by [`try_insert`](HashMap::try_insert) when the key already exists.
1938 /// Contains the occupied entry, and the value that was not inserted.
1939 #[unstable(feature = "map_try_insert", issue = "82766")]
1940 pub struct OccupiedError<'a, K: 'a, V: 'a> {
1941 /// The entry in the map that was already occupied.
1942 pub entry: OccupiedEntry<'a, K, V>,
1943 /// The value which was not inserted, because the entry was already occupied.
1947 #[unstable(feature = "map_try_insert", issue = "82766")]
1948 impl<K: Debug, V: Debug> Debug for OccupiedError<'_, K, V> {
1949 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1950 f.debug_struct("OccupiedError")
1951 .field("key", self.entry.key())
1952 .field("old_value", self.entry.get())
1953 .field("new_value", &self.value)
1954 .finish_non_exhaustive()
1958 #[unstable(feature = "map_try_insert", issue = "82766")]
1959 impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V> {
1960 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1963 "failed to insert {:?}, key {:?} already exists with value {:?}",
1971 #[stable(feature = "rust1", since = "1.0.0")]
1972 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> {
1973 type Item = (&'a K, &'a V);
1974 type IntoIter = Iter<'a, K, V>;
1977 fn into_iter(self) -> Iter<'a, K, V> {
1982 #[stable(feature = "rust1", since = "1.0.0")]
1983 impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S> {
1984 type Item = (&'a K, &'a mut V);
1985 type IntoIter = IterMut<'a, K, V>;
1988 fn into_iter(self) -> IterMut<'a, K, V> {
1993 #[stable(feature = "rust1", since = "1.0.0")]
1994 impl<K, V, S> IntoIterator for HashMap<K, V, S> {
1996 type IntoIter = IntoIter<K, V>;
1998 /// Creates a consuming iterator, that is, one that moves each key-value
1999 /// pair out of the map in arbitrary order. The map cannot be used after
2005 /// use std::collections::HashMap;
2007 /// let mut map = HashMap::new();
2008 /// map.insert("a", 1);
2009 /// map.insert("b", 2);
2010 /// map.insert("c", 3);
2012 /// // Not possible with .iter()
2013 /// let vec: Vec<(&str, i32)> = map.into_iter().collect();
2016 fn into_iter(self) -> IntoIter<K, V> {
2017 IntoIter { base: self.base.into_iter() }
2021 #[stable(feature = "rust1", since = "1.0.0")]
2022 impl<'a, K, V> Iterator for Iter<'a, K, V> {
2023 type Item = (&'a K, &'a V);
2026 fn next(&mut self) -> Option<(&'a K, &'a V)> {
2030 fn size_hint(&self) -> (usize, Option<usize>) {
2031 self.base.size_hint()
2034 #[stable(feature = "rust1", since = "1.0.0")]
2035 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
2037 fn len(&self) -> usize {
2042 #[stable(feature = "fused", since = "1.26.0")]
2043 impl<K, V> FusedIterator for Iter<'_, K, V> {}
2045 #[stable(feature = "rust1", since = "1.0.0")]
2046 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
2047 type Item = (&'a K, &'a mut V);
2050 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
2054 fn size_hint(&self) -> (usize, Option<usize>) {
2055 self.base.size_hint()
2058 #[stable(feature = "rust1", since = "1.0.0")]
2059 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
2061 fn len(&self) -> usize {
2065 #[stable(feature = "fused", since = "1.26.0")]
2066 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
2068 #[stable(feature = "std_debug", since = "1.16.0")]
2069 impl<K, V> fmt::Debug for IterMut<'_, K, V>
2074 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2075 f.debug_list().entries(self.iter()).finish()
2079 #[stable(feature = "rust1", since = "1.0.0")]
2080 impl<K, V> Iterator for IntoIter<K, V> {
2084 fn next(&mut self) -> Option<(K, V)> {
2088 fn size_hint(&self) -> (usize, Option<usize>) {
2089 self.base.size_hint()
2092 #[stable(feature = "rust1", since = "1.0.0")]
2093 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
2095 fn len(&self) -> usize {
2099 #[stable(feature = "fused", since = "1.26.0")]
2100 impl<K, V> FusedIterator for IntoIter<K, V> {}
2102 #[stable(feature = "std_debug", since = "1.16.0")]
2103 impl<K: Debug, V: Debug> fmt::Debug for IntoIter<K, V> {
2104 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2105 f.debug_list().entries(self.iter()).finish()
2109 #[stable(feature = "rust1", since = "1.0.0")]
2110 impl<'a, K, V> Iterator for Keys<'a, K, V> {
2114 fn next(&mut self) -> Option<&'a K> {
2115 self.inner.next().map(|(k, _)| k)
2118 fn size_hint(&self) -> (usize, Option<usize>) {
2119 self.inner.size_hint()
2122 #[stable(feature = "rust1", since = "1.0.0")]
2123 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
2125 fn len(&self) -> usize {
2129 #[stable(feature = "fused", since = "1.26.0")]
2130 impl<K, V> FusedIterator for Keys<'_, K, V> {}
2132 #[stable(feature = "rust1", since = "1.0.0")]
2133 impl<'a, K, V> Iterator for Values<'a, K, V> {
2137 fn next(&mut self) -> Option<&'a V> {
2138 self.inner.next().map(|(_, v)| v)
2141 fn size_hint(&self) -> (usize, Option<usize>) {
2142 self.inner.size_hint()
2145 #[stable(feature = "rust1", since = "1.0.0")]
2146 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
2148 fn len(&self) -> usize {
2152 #[stable(feature = "fused", since = "1.26.0")]
2153 impl<K, V> FusedIterator for Values<'_, K, V> {}
2155 #[stable(feature = "map_values_mut", since = "1.10.0")]
2156 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
2157 type Item = &'a mut V;
2160 fn next(&mut self) -> Option<&'a mut V> {
2161 self.inner.next().map(|(_, v)| v)
2164 fn size_hint(&self) -> (usize, Option<usize>) {
2165 self.inner.size_hint()
2168 #[stable(feature = "map_values_mut", since = "1.10.0")]
2169 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
2171 fn len(&self) -> usize {
2175 #[stable(feature = "fused", since = "1.26.0")]
2176 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
2178 #[stable(feature = "std_debug", since = "1.16.0")]
2179 impl<K, V: fmt::Debug> fmt::Debug for ValuesMut<'_, K, V> {
2180 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2181 f.debug_list().entries(self.inner.iter().map(|(_, val)| val)).finish()
2185 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2186 impl<K, V> Iterator for IntoKeys<K, V> {
2190 fn next(&mut self) -> Option<K> {
2191 self.inner.next().map(|(k, _)| k)
2194 fn size_hint(&self) -> (usize, Option<usize>) {
2195 self.inner.size_hint()
2198 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2199 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
2201 fn len(&self) -> usize {
2205 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2206 impl<K, V> FusedIterator for IntoKeys<K, V> {}
2208 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2209 impl<K: Debug, V> fmt::Debug for IntoKeys<K, V> {
2210 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2211 f.debug_list().entries(self.inner.iter().map(|(k, _)| k)).finish()
2215 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2216 impl<K, V> Iterator for IntoValues<K, V> {
2220 fn next(&mut self) -> Option<V> {
2221 self.inner.next().map(|(_, v)| v)
2224 fn size_hint(&self) -> (usize, Option<usize>) {
2225 self.inner.size_hint()
2228 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2229 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
2231 fn len(&self) -> usize {
2235 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2236 impl<K, V> FusedIterator for IntoValues<K, V> {}
2238 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
2239 impl<K, V: Debug> fmt::Debug for IntoValues<K, V> {
2240 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2241 f.debug_list().entries(self.inner.iter().map(|(_, v)| v)).finish()
2245 #[stable(feature = "drain", since = "1.6.0")]
2246 impl<'a, K, V> Iterator for Drain<'a, K, V> {
2250 fn next(&mut self) -> Option<(K, V)> {
2254 fn size_hint(&self) -> (usize, Option<usize>) {
2255 self.base.size_hint()
2258 #[stable(feature = "drain", since = "1.6.0")]
2259 impl<K, V> ExactSizeIterator for Drain<'_, K, V> {
2261 fn len(&self) -> usize {
2265 #[stable(feature = "fused", since = "1.26.0")]
2266 impl<K, V> FusedIterator for Drain<'_, K, V> {}
2268 #[stable(feature = "std_debug", since = "1.16.0")]
2269 impl<K, V> fmt::Debug for Drain<'_, K, V>
2274 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2275 f.debug_list().entries(self.iter()).finish()
2279 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2280 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
2282 F: FnMut(&K, &mut V) -> bool,
2287 fn next(&mut self) -> Option<(K, V)> {
2291 fn size_hint(&self) -> (usize, Option<usize>) {
2292 self.base.size_hint()
2296 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2297 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
2299 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2300 impl<'a, K, V, F> fmt::Debug for DrainFilter<'a, K, V, F>
2302 F: FnMut(&K, &mut V) -> bool,
2304 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2305 f.debug_struct("DrainFilter").finish_non_exhaustive()
2309 impl<'a, K, V> Entry<'a, K, V> {
2310 /// Ensures a value is in the entry by inserting the default if empty, and returns
2311 /// a mutable reference to the value in the entry.
2316 /// use std::collections::HashMap;
2318 /// let mut map: HashMap<&str, u32> = HashMap::new();
2320 /// map.entry("poneyland").or_insert(3);
2321 /// assert_eq!(map["poneyland"], 3);
2323 /// *map.entry("poneyland").or_insert(10) *= 2;
2324 /// assert_eq!(map["poneyland"], 6);
2327 #[stable(feature = "rust1", since = "1.0.0")]
2328 pub fn or_insert(self, default: V) -> &'a mut V {
2330 Occupied(entry) => entry.into_mut(),
2331 Vacant(entry) => entry.insert(default),
2335 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2336 /// and returns a mutable reference to the value in the entry.
2341 /// use std::collections::HashMap;
2343 /// let mut map: HashMap<&str, String> = HashMap::new();
2344 /// let s = "hoho".to_string();
2346 /// map.entry("poneyland").or_insert_with(|| s);
2348 /// assert_eq!(map["poneyland"], "hoho".to_string());
2351 #[stable(feature = "rust1", since = "1.0.0")]
2352 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2354 Occupied(entry) => entry.into_mut(),
2355 Vacant(entry) => entry.insert(default()),
2359 /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
2360 /// This method allows for generating key-derived values for insertion by providing the default
2361 /// function a reference to the key that was moved during the `.entry(key)` method call.
2363 /// The reference to the moved key is provided so that cloning or copying the key is
2364 /// unnecessary, unlike with `.or_insert_with(|| ... )`.
2369 /// use std::collections::HashMap;
2371 /// let mut map: HashMap<&str, usize> = HashMap::new();
2373 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2375 /// assert_eq!(map["poneyland"], 9);
2378 #[stable(feature = "or_insert_with_key", since = "1.50.0")]
2379 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2381 Occupied(entry) => entry.into_mut(),
2383 let value = default(entry.key());
2389 /// Returns a reference to this entry's key.
2394 /// use std::collections::HashMap;
2396 /// let mut map: HashMap<&str, u32> = HashMap::new();
2397 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2400 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2401 pub fn key(&self) -> &K {
2403 Occupied(ref entry) => entry.key(),
2404 Vacant(ref entry) => entry.key(),
2408 /// Provides in-place mutable access to an occupied entry before any
2409 /// potential inserts into the map.
2414 /// use std::collections::HashMap;
2416 /// let mut map: HashMap<&str, u32> = HashMap::new();
2418 /// map.entry("poneyland")
2419 /// .and_modify(|e| { *e += 1 })
2421 /// assert_eq!(map["poneyland"], 42);
2423 /// map.entry("poneyland")
2424 /// .and_modify(|e| { *e += 1 })
2426 /// assert_eq!(map["poneyland"], 43);
2429 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2430 pub fn and_modify<F>(self, f: F) -> Self
2435 Occupied(mut entry) => {
2439 Vacant(entry) => Vacant(entry),
2443 /// Sets the value of the entry, and returns an `OccupiedEntry`.
2448 /// #![feature(entry_insert)]
2449 /// use std::collections::HashMap;
2451 /// let mut map: HashMap<&str, String> = HashMap::new();
2452 /// let entry = map.entry("poneyland").insert("hoho".to_string());
2454 /// assert_eq!(entry.key(), &"poneyland");
2457 #[unstable(feature = "entry_insert", issue = "65225")]
2458 pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V> {
2460 Occupied(mut entry) => {
2461 entry.insert(value);
2464 Vacant(entry) => entry.insert_entry(value),
2469 impl<'a, K, V: Default> Entry<'a, K, V> {
2470 /// Ensures a value is in the entry by inserting the default value if empty,
2471 /// and returns a mutable reference to the value in the entry.
2477 /// use std::collections::HashMap;
2479 /// let mut map: HashMap<&str, Option<u32>> = HashMap::new();
2480 /// map.entry("poneyland").or_default();
2482 /// assert_eq!(map["poneyland"], None);
2486 #[stable(feature = "entry_or_default", since = "1.28.0")]
2487 pub fn or_default(self) -> &'a mut V {
2489 Occupied(entry) => entry.into_mut(),
2490 Vacant(entry) => entry.insert(Default::default()),
2495 impl<'a, K, V> OccupiedEntry<'a, K, V> {
2496 /// Gets a reference to the key in the entry.
2501 /// use std::collections::HashMap;
2503 /// let mut map: HashMap<&str, u32> = HashMap::new();
2504 /// map.entry("poneyland").or_insert(12);
2505 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2508 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2509 pub fn key(&self) -> &K {
2513 /// Take the ownership of the key and value from the map.
2518 /// use std::collections::HashMap;
2519 /// use std::collections::hash_map::Entry;
2521 /// let mut map: HashMap<&str, u32> = HashMap::new();
2522 /// map.entry("poneyland").or_insert(12);
2524 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2525 /// // We delete the entry from the map.
2526 /// o.remove_entry();
2529 /// assert_eq!(map.contains_key("poneyland"), false);
2532 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2533 pub fn remove_entry(self) -> (K, V) {
2534 self.base.remove_entry()
2537 /// Gets a reference to the value in the entry.
2542 /// use std::collections::HashMap;
2543 /// use std::collections::hash_map::Entry;
2545 /// let mut map: HashMap<&str, u32> = HashMap::new();
2546 /// map.entry("poneyland").or_insert(12);
2548 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2549 /// assert_eq!(o.get(), &12);
2553 #[stable(feature = "rust1", since = "1.0.0")]
2554 pub fn get(&self) -> &V {
2558 /// Gets a mutable reference to the value in the entry.
2560 /// If you need a reference to the `OccupiedEntry` which may outlive the
2561 /// destruction of the `Entry` value, see [`into_mut`].
2563 /// [`into_mut`]: Self::into_mut
2568 /// use std::collections::HashMap;
2569 /// use std::collections::hash_map::Entry;
2571 /// let mut map: HashMap<&str, u32> = HashMap::new();
2572 /// map.entry("poneyland").or_insert(12);
2574 /// assert_eq!(map["poneyland"], 12);
2575 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2576 /// *o.get_mut() += 10;
2577 /// assert_eq!(*o.get(), 22);
2579 /// // We can use the same Entry multiple times.
2580 /// *o.get_mut() += 2;
2583 /// assert_eq!(map["poneyland"], 24);
2586 #[stable(feature = "rust1", since = "1.0.0")]
2587 pub fn get_mut(&mut self) -> &mut V {
2591 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
2592 /// with a lifetime bound to the map itself.
2594 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2596 /// [`get_mut`]: Self::get_mut
2601 /// use std::collections::HashMap;
2602 /// use std::collections::hash_map::Entry;
2604 /// let mut map: HashMap<&str, u32> = HashMap::new();
2605 /// map.entry("poneyland").or_insert(12);
2607 /// assert_eq!(map["poneyland"], 12);
2608 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2609 /// *o.into_mut() += 10;
2612 /// assert_eq!(map["poneyland"], 22);
2615 #[stable(feature = "rust1", since = "1.0.0")]
2616 pub fn into_mut(self) -> &'a mut V {
2617 self.base.into_mut()
2620 /// Sets the value of the entry, and returns the entry's old value.
2625 /// use std::collections::HashMap;
2626 /// use std::collections::hash_map::Entry;
2628 /// let mut map: HashMap<&str, u32> = HashMap::new();
2629 /// map.entry("poneyland").or_insert(12);
2631 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2632 /// assert_eq!(o.insert(15), 12);
2635 /// assert_eq!(map["poneyland"], 15);
2638 #[stable(feature = "rust1", since = "1.0.0")]
2639 pub fn insert(&mut self, value: V) -> V {
2640 self.base.insert(value)
2643 /// Takes the value out of the entry, and returns it.
2648 /// use std::collections::HashMap;
2649 /// use std::collections::hash_map::Entry;
2651 /// let mut map: HashMap<&str, u32> = HashMap::new();
2652 /// map.entry("poneyland").or_insert(12);
2654 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2655 /// assert_eq!(o.remove(), 12);
2658 /// assert_eq!(map.contains_key("poneyland"), false);
2661 #[stable(feature = "rust1", since = "1.0.0")]
2662 pub fn remove(self) -> V {
2666 /// Replaces the entry, returning the old key and value. The new key in the hash map will be
2667 /// the key used to create this entry.
2672 /// #![feature(map_entry_replace)]
2673 /// use std::collections::hash_map::{Entry, HashMap};
2674 /// use std::rc::Rc;
2676 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2677 /// map.insert(Rc::new("Stringthing".to_string()), 15);
2679 /// let my_key = Rc::new("Stringthing".to_string());
2681 /// if let Entry::Occupied(entry) = map.entry(my_key) {
2682 /// // Also replace the key with a handle to our other key.
2683 /// let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
2688 #[unstable(feature = "map_entry_replace", issue = "44286")]
2689 pub fn replace_entry(self, value: V) -> (K, V) {
2690 self.base.replace_entry(value)
2693 /// Replaces the key in the hash map with the key used to create this entry.
2698 /// #![feature(map_entry_replace)]
2699 /// use std::collections::hash_map::{Entry, HashMap};
2700 /// use std::rc::Rc;
2702 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2703 /// let known_strings: Vec<Rc<String>> = Vec::new();
2705 /// // Initialise known strings, run program, etc.
2707 /// reclaim_memory(&mut map, &known_strings);
2709 /// fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
2710 /// for s in known_strings {
2711 /// if let Entry::Occupied(entry) = map.entry(Rc::clone(s)) {
2712 /// // Replaces the entry's key with our version of it in `known_strings`.
2713 /// entry.replace_key();
2719 #[unstable(feature = "map_entry_replace", issue = "44286")]
2720 pub fn replace_key(self) -> K {
2721 self.base.replace_key()
2725 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
2726 /// Gets a reference to the key that would be used when inserting a value
2727 /// through the `VacantEntry`.
2732 /// use std::collections::HashMap;
2734 /// let mut map: HashMap<&str, u32> = HashMap::new();
2735 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2738 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2739 pub fn key(&self) -> &K {
2743 /// Take ownership of the key.
2748 /// use std::collections::HashMap;
2749 /// use std::collections::hash_map::Entry;
2751 /// let mut map: HashMap<&str, u32> = HashMap::new();
2753 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2758 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2759 pub fn into_key(self) -> K {
2760 self.base.into_key()
2763 /// Sets the value of the entry with the `VacantEntry`'s key,
2764 /// and returns a mutable reference to it.
2769 /// use std::collections::HashMap;
2770 /// use std::collections::hash_map::Entry;
2772 /// let mut map: HashMap<&str, u32> = HashMap::new();
2774 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2777 /// assert_eq!(map["poneyland"], 37);
2780 #[stable(feature = "rust1", since = "1.0.0")]
2781 pub fn insert(self, value: V) -> &'a mut V {
2782 self.base.insert(value)
2785 /// Sets the value of the entry with the `VacantEntry`'s key,
2786 /// and returns an `OccupiedEntry`.
2791 /// use std::collections::HashMap;
2792 /// use std::collections::hash_map::Entry;
2794 /// let mut map: HashMap<&str, u32> = HashMap::new();
2796 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2799 /// assert_eq!(map["poneyland"], 37);
2802 fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> {
2803 let base = self.base.insert_entry(value);
2804 OccupiedEntry { base }
2808 #[stable(feature = "rust1", since = "1.0.0")]
2809 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
2812 S: BuildHasher + Default,
2814 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> HashMap<K, V, S> {
2815 let mut map = HashMap::with_hasher(Default::default());
2821 /// Inserts all new key-values from the iterator and replaces values with existing
2822 /// keys with new values returned from the iterator.
2823 #[stable(feature = "rust1", since = "1.0.0")]
2824 impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>
2830 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
2831 self.base.extend(iter)
2835 fn extend_one(&mut self, (k, v): (K, V)) {
2836 self.base.insert(k, v);
2840 fn extend_reserve(&mut self, additional: usize) {
2841 self.base.extend_reserve(additional);
2845 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
2846 impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>
2848 K: Eq + Hash + Copy,
2853 fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T) {
2854 self.base.extend(iter)
2858 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2859 self.base.insert(k, v);
2863 fn extend_reserve(&mut self, additional: usize) {
2864 Extend::<(K, V)>::extend_reserve(self, additional)
2868 /// `RandomState` is the default state for [`HashMap`] types.
2870 /// A particular instance `RandomState` will create the same instances of
2871 /// [`Hasher`], but the hashers created by two different `RandomState`
2872 /// instances are unlikely to produce the same result for the same values.
2877 /// use std::collections::HashMap;
2878 /// use std::collections::hash_map::RandomState;
2880 /// let s = RandomState::new();
2881 /// let mut map = HashMap::with_hasher(s);
2882 /// map.insert(1, 2);
2885 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2886 pub struct RandomState {
2892 /// Constructs a new `RandomState` that is initialized with random keys.
2897 /// use std::collections::hash_map::RandomState;
2899 /// let s = RandomState::new();
2902 #[allow(deprecated)]
2905 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2906 pub fn new() -> RandomState {
2907 // Historically this function did not cache keys from the OS and instead
2908 // simply always called `rand::thread_rng().gen()` twice. In #31356 it
2909 // was discovered, however, that because we re-seed the thread-local RNG
2910 // from the OS periodically that this can cause excessive slowdown when
2911 // many hash maps are created on a thread. To solve this performance
2912 // trap we cache the first set of randomly generated keys per-thread.
2914 // Later in #36481 it was discovered that exposing a deterministic
2915 // iteration order allows a form of DOS attack. To counter that we
2916 // increment one of the seeds on every RandomState creation, giving
2917 // every corresponding HashMap a different iteration order.
2918 thread_local!(static KEYS: Cell<(u64, u64)> = {
2919 Cell::new(sys::hashmap_random_keys())
2923 let (k0, k1) = keys.get();
2924 keys.set((k0.wrapping_add(1), k1));
2925 RandomState { k0, k1 }
2930 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2931 impl BuildHasher for RandomState {
2932 type Hasher = DefaultHasher;
2934 #[allow(deprecated)]
2935 fn build_hasher(&self) -> DefaultHasher {
2936 DefaultHasher(SipHasher13::new_with_keys(self.k0, self.k1))
2940 /// The default [`Hasher`] used by [`RandomState`].
2942 /// The internal algorithm is not specified, and so it and its hashes should
2943 /// not be relied upon over releases.
2944 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2945 #[allow(deprecated)]
2946 #[derive(Clone, Debug)]
2947 pub struct DefaultHasher(SipHasher13);
2949 impl DefaultHasher {
2950 /// Creates a new `DefaultHasher`.
2952 /// This hasher is not guaranteed to be the same as all other
2953 /// `DefaultHasher` instances, but is the same as all other `DefaultHasher`
2954 /// instances created through `new` or `default`.
2955 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2956 #[allow(deprecated)]
2958 pub fn new() -> DefaultHasher {
2959 DefaultHasher(SipHasher13::new_with_keys(0, 0))
2963 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2964 impl Default for DefaultHasher {
2965 /// Creates a new `DefaultHasher` using [`new`].
2966 /// See its documentation for more.
2968 /// [`new`]: DefaultHasher::new
2969 fn default() -> DefaultHasher {
2970 DefaultHasher::new()
2974 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2975 impl Hasher for DefaultHasher {
2977 fn write(&mut self, msg: &[u8]) {
2982 fn finish(&self) -> u64 {
2987 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2988 impl Default for RandomState {
2989 /// Constructs a new `RandomState`.
2991 fn default() -> RandomState {
2996 #[stable(feature = "std_debug", since = "1.16.0")]
2997 impl fmt::Debug for RandomState {
2998 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2999 f.debug_struct("RandomState").finish_non_exhaustive()
3004 fn map_entry<'a, K: 'a, V: 'a>(raw: base::RustcEntry<'a, K, V>) -> Entry<'a, K, V> {
3006 base::RustcEntry::Occupied(base) => Entry::Occupied(OccupiedEntry { base }),
3007 base::RustcEntry::Vacant(base) => Entry::Vacant(VacantEntry { base }),
3012 pub(super) fn map_try_reserve_error(err: hashbrown::TryReserveError) -> TryReserveError {
3014 hashbrown::TryReserveError::CapacityOverflow => {
3015 TryReserveErrorKind::CapacityOverflow.into()
3017 hashbrown::TryReserveError::AllocError { layout } => {
3018 TryReserveErrorKind::AllocError { layout, non_exhaustive: () }.into()
3024 fn map_raw_entry<'a, K: 'a, V: 'a, S: 'a>(
3025 raw: base::RawEntryMut<'a, K, V, S>,
3026 ) -> RawEntryMut<'a, K, V, S> {
3028 base::RawEntryMut::Occupied(base) => RawEntryMut::Occupied(RawOccupiedEntryMut { base }),
3029 base::RawEntryMut::Vacant(base) => RawEntryMut::Vacant(RawVacantEntryMut { base }),
3034 fn assert_covariance() {
3035 fn map_key<'new>(v: HashMap<&'static str, u8>) -> HashMap<&'new str, u8> {
3038 fn map_val<'new>(v: HashMap<u8, &'static str>) -> HashMap<u8, &'new str> {
3041 fn iter_key<'a, 'new>(v: Iter<'a, &'static str, u8>) -> Iter<'a, &'new str, u8> {
3044 fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
3047 fn into_iter_key<'new>(v: IntoIter<&'static str, u8>) -> IntoIter<&'new str, u8> {
3050 fn into_iter_val<'new>(v: IntoIter<u8, &'static str>) -> IntoIter<u8, &'new str> {
3053 fn keys_key<'a, 'new>(v: Keys<'a, &'static str, u8>) -> Keys<'a, &'new str, u8> {
3056 fn keys_val<'a, 'new>(v: Keys<'a, u8, &'static str>) -> Keys<'a, u8, &'new str> {
3059 fn values_key<'a, 'new>(v: Values<'a, &'static str, u8>) -> Values<'a, &'new str, u8> {
3062 fn values_val<'a, 'new>(v: Values<'a, u8, &'static str>) -> Values<'a, u8, &'new str> {
3066 d: Drain<'static, &'static str, &'static str>,
3067 ) -> Drain<'new, &'new str, &'new str> {