1 // ignore-tidy-filelength
8 use hashbrown::hash_map as base;
10 use crate::borrow::Borrow;
11 use crate::cell::Cell;
12 use crate::collections::TryReserveError;
13 use crate::fmt::{self, Debug};
15 use crate::hash::{BuildHasher, Hash, Hasher, SipHasher13};
16 use crate::iter::{FromIterator, FusedIterator};
17 use crate::ops::Index;
20 /// A [hash map] implemented with quadratic probing and SIMD lookup.
22 /// By default, `HashMap` uses a hashing algorithm selected to provide
23 /// resistance against HashDoS attacks. The algorithm is randomly seeded, and a
24 /// reasonable best-effort is made to generate this seed from a high quality,
25 /// secure source of randomness provided by the host without blocking the
26 /// program. Because of this, the randomness of the seed depends on the output
27 /// quality of the system's random number generator when the seed is created.
28 /// In particular, seeds generated when the system's entropy pool is abnormally
29 /// low such as during system boot may be of a lower quality.
31 /// The default hashing algorithm is currently SipHash 1-3, though this is
32 /// subject to change at any point in the future. While its performance is very
33 /// competitive for medium sized keys, other hashing algorithms will outperform
34 /// it for small keys such as integers as well as large keys such as long
35 /// strings, though those algorithms will typically *not* protect against
36 /// attacks such as HashDoS.
38 /// The hashing algorithm can be replaced on a per-`HashMap` basis using the
39 /// [`default`], [`with_hasher`], and [`with_capacity_and_hasher`] methods.
40 /// There are many alternative [hashing algorithms available on crates.io].
42 /// It is required that the keys implement the [`Eq`] and [`Hash`] traits, although
43 /// this can frequently be achieved by using `#[derive(PartialEq, Eq, Hash)]`.
44 /// If you implement these yourself, it is important that the following
48 /// k1 == k2 -> hash(k1) == hash(k2)
51 /// In other words, if two keys are equal, their hashes must be equal.
53 /// It is a logic error for a key to be modified in such a way that the key's
54 /// hash, as determined by the [`Hash`] trait, or its equality, as determined by
55 /// the [`Eq`] trait, changes while it is in the map. This is normally only
56 /// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
57 /// The behavior resulting from such a logic error is not specified, but will
58 /// not result in undefined behavior. This could include panics, incorrect results,
59 /// aborts, memory leaks, and non-termination.
61 /// The hash table implementation is a Rust port of Google's [SwissTable].
62 /// The original C++ version of SwissTable can be found [here], and this
63 /// [CppCon talk] gives an overview of how the algorithm works.
65 /// [hash map]: crate::collections#use-a-hashmap-when
66 /// [hashing algorithms available on crates.io]: https://crates.io/keywords/hasher
67 /// [SwissTable]: https://abseil.io/blog/20180927-swisstables
68 /// [here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h
69 /// [CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4
74 /// use std::collections::HashMap;
76 /// // Type inference lets us omit an explicit type signature (which
77 /// // would be `HashMap<String, String>` in this example).
78 /// let mut book_reviews = HashMap::new();
80 /// // Review some books.
81 /// book_reviews.insert(
82 /// "Adventures of Huckleberry Finn".to_string(),
83 /// "My favorite book.".to_string(),
85 /// book_reviews.insert(
86 /// "Grimms' Fairy Tales".to_string(),
87 /// "Masterpiece.".to_string(),
89 /// book_reviews.insert(
90 /// "Pride and Prejudice".to_string(),
91 /// "Very enjoyable.".to_string(),
93 /// book_reviews.insert(
94 /// "The Adventures of Sherlock Holmes".to_string(),
95 /// "Eye lyked it alot.".to_string(),
98 /// // Check for a specific one.
99 /// // When collections store owned values (String), they can still be
100 /// // queried using references (&str).
101 /// if !book_reviews.contains_key("Les Misérables") {
102 /// println!("We've got {} reviews, but Les Misérables ain't one.",
103 /// book_reviews.len());
106 /// // oops, this review has a lot of spelling mistakes, let's delete it.
107 /// book_reviews.remove("The Adventures of Sherlock Holmes");
109 /// // Look up the values associated with some keys.
110 /// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
111 /// for &book in &to_find {
112 /// match book_reviews.get(book) {
113 /// Some(review) => println!("{}: {}", book, review),
114 /// None => println!("{} is unreviewed.", book)
118 /// // Look up the value for a key (will panic if the key is not found).
119 /// println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);
121 /// // Iterate over everything.
122 /// for (book, review) in &book_reviews {
123 /// println!("{}: \"{}\"", book, review);
127 /// `HashMap` also implements an [`Entry API`](#method.entry), which allows
128 /// for more complex methods of getting, setting, updating and removing keys and
132 /// use std::collections::HashMap;
134 /// // type inference lets us omit an explicit type signature (which
135 /// // would be `HashMap<&str, u8>` in this example).
136 /// let mut player_stats = HashMap::new();
138 /// fn random_stat_buff() -> u8 {
139 /// // could actually return some random value here - let's just return
140 /// // some fixed value for now
144 /// // insert a key only if it doesn't already exist
145 /// player_stats.entry("health").or_insert(100);
147 /// // insert a key using a function that provides a new value only if it
148 /// // doesn't already exist
149 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
151 /// // update a key, guarding against the key possibly not being set
152 /// let stat = player_stats.entry("attack").or_insert(100);
153 /// *stat += random_stat_buff();
156 /// The easiest way to use `HashMap` with a custom key type is to derive [`Eq`] and [`Hash`].
157 /// We must also derive [`PartialEq`].
159 /// [`RefCell`]: crate::cell::RefCell
160 /// [`Cell`]: crate::cell::Cell
161 /// [`default`]: Default::default
162 /// [`with_hasher`]: Self::with_hasher
163 /// [`with_capacity_and_hasher`]: Self::with_capacity_and_hasher
166 /// use std::collections::HashMap;
168 /// #[derive(Hash, Eq, PartialEq, Debug)]
175 /// /// Creates a new Viking.
176 /// fn new(name: &str, country: &str) -> Viking {
177 /// Viking { name: name.to_string(), country: country.to_string() }
181 /// // Use a HashMap to store the vikings' health points.
182 /// let mut vikings = HashMap::new();
184 /// vikings.insert(Viking::new("Einar", "Norway"), 25);
185 /// vikings.insert(Viking::new("Olaf", "Denmark"), 24);
186 /// vikings.insert(Viking::new("Harald", "Iceland"), 12);
188 /// // Use derived implementation to print the status of the vikings.
189 /// for (viking, health) in &vikings {
190 /// println!("{:?} has {} hp", viking, health);
194 /// A `HashMap` with fixed list of elements can be initialized from an array:
197 /// use std::collections::HashMap;
199 /// let timber_resources: HashMap<&str, i32> = [("Norway", 100), ("Denmark", 50), ("Iceland", 10)]
200 /// .iter().cloned().collect();
201 /// // use the values stored in map
204 #[cfg_attr(not(test), rustc_diagnostic_item = "hashmap_type")]
205 #[stable(feature = "rust1", since = "1.0.0")]
206 pub struct HashMap<K, V, S = RandomState> {
207 base: base::HashMap<K, V, S>,
210 impl<K, V> HashMap<K, V, RandomState> {
211 /// Creates an empty `HashMap`.
213 /// The hash map is initially created with a capacity of 0, so it will not allocate until it
214 /// is first inserted into.
219 /// use std::collections::HashMap;
220 /// let mut map: HashMap<&str, i32> = HashMap::new();
223 #[stable(feature = "rust1", since = "1.0.0")]
224 pub fn new() -> HashMap<K, V, RandomState> {
228 /// Creates an empty `HashMap` with the specified capacity.
230 /// The hash map will be able to hold at least `capacity` elements without
231 /// reallocating. If `capacity` is 0, the hash map will not allocate.
236 /// use std::collections::HashMap;
237 /// let mut map: HashMap<&str, i32> = HashMap::with_capacity(10);
240 #[stable(feature = "rust1", since = "1.0.0")]
241 pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState> {
242 HashMap::with_capacity_and_hasher(capacity, Default::default())
246 impl<K, V, S> HashMap<K, V, S> {
247 /// Creates an empty `HashMap` which will use the given hash builder to hash
250 /// The created map has the default initial capacity.
252 /// Warning: `hash_builder` is normally randomly generated, and
253 /// is designed to allow HashMaps to be resistant to attacks that
254 /// cause many collisions and very poor performance. Setting it
255 /// manually using this function can expose a DoS attack vector.
257 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
258 /// the HashMap to be useful, see its documentation for details.
263 /// use std::collections::HashMap;
264 /// use std::collections::hash_map::RandomState;
266 /// let s = RandomState::new();
267 /// let mut map = HashMap::with_hasher(s);
268 /// map.insert(1, 2);
271 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
272 pub fn with_hasher(hash_builder: S) -> HashMap<K, V, S> {
273 HashMap { base: base::HashMap::with_hasher(hash_builder) }
276 /// Creates an empty `HashMap` with the specified capacity, using `hash_builder`
277 /// to hash the keys.
279 /// The hash map will be able to hold at least `capacity` elements without
280 /// reallocating. If `capacity` is 0, the hash map will not allocate.
282 /// Warning: `hash_builder` is normally randomly generated, and
283 /// is designed to allow HashMaps to be resistant to attacks that
284 /// cause many collisions and very poor performance. Setting it
285 /// manually using this function can expose a DoS attack vector.
287 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
288 /// the HashMap to be useful, see its documentation for details.
293 /// use std::collections::HashMap;
294 /// use std::collections::hash_map::RandomState;
296 /// let s = RandomState::new();
297 /// let mut map = HashMap::with_capacity_and_hasher(10, s);
298 /// map.insert(1, 2);
301 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
302 pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> HashMap<K, V, S> {
303 HashMap { base: base::HashMap::with_capacity_and_hasher(capacity, hash_builder) }
306 /// Returns the number of elements the map can hold without reallocating.
308 /// This number is a lower bound; the `HashMap<K, V>` might be able to hold
309 /// more, but is guaranteed to be able to hold at least this many.
314 /// use std::collections::HashMap;
315 /// let map: HashMap<i32, i32> = HashMap::with_capacity(100);
316 /// assert!(map.capacity() >= 100);
319 #[stable(feature = "rust1", since = "1.0.0")]
320 pub fn capacity(&self) -> usize {
324 /// An iterator visiting all keys in arbitrary order.
325 /// The iterator element type is `&'a K`.
330 /// use std::collections::HashMap;
332 /// let mut map = HashMap::new();
333 /// map.insert("a", 1);
334 /// map.insert("b", 2);
335 /// map.insert("c", 3);
337 /// for key in map.keys() {
338 /// println!("{}", key);
341 #[stable(feature = "rust1", since = "1.0.0")]
342 pub fn keys(&self) -> Keys<'_, K, V> {
343 Keys { inner: self.iter() }
346 /// An iterator visiting all values in arbitrary order.
347 /// The iterator element type is `&'a V`.
352 /// use std::collections::HashMap;
354 /// let mut map = HashMap::new();
355 /// map.insert("a", 1);
356 /// map.insert("b", 2);
357 /// map.insert("c", 3);
359 /// for val in map.values() {
360 /// println!("{}", val);
363 #[stable(feature = "rust1", since = "1.0.0")]
364 pub fn values(&self) -> Values<'_, K, V> {
365 Values { inner: self.iter() }
368 /// An iterator visiting all values mutably in arbitrary order.
369 /// The iterator element type is `&'a mut V`.
374 /// use std::collections::HashMap;
376 /// let mut map = HashMap::new();
378 /// map.insert("a", 1);
379 /// map.insert("b", 2);
380 /// map.insert("c", 3);
382 /// for val in map.values_mut() {
383 /// *val = *val + 10;
386 /// for val in map.values() {
387 /// println!("{}", val);
390 #[stable(feature = "map_values_mut", since = "1.10.0")]
391 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
392 ValuesMut { inner: self.iter_mut() }
395 /// An iterator visiting all key-value pairs in arbitrary order.
396 /// The iterator element type is `(&'a K, &'a V)`.
401 /// use std::collections::HashMap;
403 /// let mut map = HashMap::new();
404 /// map.insert("a", 1);
405 /// map.insert("b", 2);
406 /// map.insert("c", 3);
408 /// for (key, val) in map.iter() {
409 /// println!("key: {} val: {}", key, val);
412 #[stable(feature = "rust1", since = "1.0.0")]
413 pub fn iter(&self) -> Iter<'_, K, V> {
414 Iter { base: self.base.iter() }
417 /// An iterator visiting all key-value pairs in arbitrary order,
418 /// with mutable references to the values.
419 /// The iterator element type is `(&'a K, &'a mut V)`.
424 /// use std::collections::HashMap;
426 /// let mut map = HashMap::new();
427 /// map.insert("a", 1);
428 /// map.insert("b", 2);
429 /// map.insert("c", 3);
431 /// // Update all values
432 /// for (_, val) in map.iter_mut() {
436 /// for (key, val) in &map {
437 /// println!("key: {} val: {}", key, val);
440 #[stable(feature = "rust1", since = "1.0.0")]
441 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
442 IterMut { base: self.base.iter_mut() }
445 /// Returns the number of elements in the map.
450 /// use std::collections::HashMap;
452 /// let mut a = HashMap::new();
453 /// assert_eq!(a.len(), 0);
454 /// a.insert(1, "a");
455 /// assert_eq!(a.len(), 1);
457 #[doc(alias = "length")]
458 #[stable(feature = "rust1", since = "1.0.0")]
459 pub fn len(&self) -> usize {
463 /// Returns `true` if the map contains no elements.
468 /// use std::collections::HashMap;
470 /// let mut a = HashMap::new();
471 /// assert!(a.is_empty());
472 /// a.insert(1, "a");
473 /// assert!(!a.is_empty());
476 #[stable(feature = "rust1", since = "1.0.0")]
477 pub fn is_empty(&self) -> bool {
481 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
482 /// allocated memory for reuse.
487 /// use std::collections::HashMap;
489 /// let mut a = HashMap::new();
490 /// a.insert(1, "a");
491 /// a.insert(2, "b");
493 /// for (k, v) in a.drain().take(1) {
494 /// assert!(k == 1 || k == 2);
495 /// assert!(v == "a" || v == "b");
498 /// assert!(a.is_empty());
501 #[stable(feature = "drain", since = "1.6.0")]
502 pub fn drain(&mut self) -> Drain<'_, K, V> {
503 Drain { base: self.base.drain() }
506 /// Creates an iterator which uses a closure to determine if an element should be removed.
508 /// If the closure returns true, the element is removed from the map and yielded.
509 /// If the closure returns false, or panics, the element remains in the map and will not be
512 /// Note that `drain_filter` lets you mutate every value in the filter closure, regardless of
513 /// whether you choose to keep or remove it.
515 /// If the iterator is only partially consumed or not consumed at all, each of the remaining
516 /// elements will still be subjected to the closure and removed and dropped if it returns true.
518 /// It is unspecified how many more elements will be subjected to the closure
519 /// if a panic occurs in the closure, or a panic occurs while dropping an element,
520 /// or if the `DrainFilter` value is leaked.
524 /// Splitting a map into even and odd keys, reusing the original map:
527 /// #![feature(hash_drain_filter)]
528 /// use std::collections::HashMap;
530 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
531 /// let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();
533 /// let mut evens = drained.keys().copied().collect::<Vec<_>>();
534 /// let mut odds = map.keys().copied().collect::<Vec<_>>();
538 /// assert_eq!(evens, vec![0, 2, 4, 6]);
539 /// assert_eq!(odds, vec![1, 3, 5, 7]);
542 #[unstable(feature = "hash_drain_filter", issue = "59618")]
543 pub fn drain_filter<F>(&mut self, pred: F) -> DrainFilter<'_, K, V, F>
545 F: FnMut(&K, &mut V) -> bool,
547 DrainFilter { base: self.base.drain_filter(pred) }
550 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
556 /// use std::collections::HashMap;
558 /// let mut a = HashMap::new();
559 /// a.insert(1, "a");
561 /// assert!(a.is_empty());
564 #[stable(feature = "rust1", since = "1.0.0")]
565 pub fn clear(&mut self) {
569 /// Returns a reference to the map's [`BuildHasher`].
574 /// use std::collections::HashMap;
575 /// use std::collections::hash_map::RandomState;
577 /// let hasher = RandomState::new();
578 /// let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
579 /// let hasher: &RandomState = map.hasher();
582 #[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
583 pub fn hasher(&self) -> &S {
588 impl<K, V, S> HashMap<K, V, S>
593 /// Reserves capacity for at least `additional` more elements to be inserted
594 /// in the `HashMap`. The collection may reserve more space to avoid
595 /// frequent reallocations.
599 /// Panics if the new allocation size overflows [`usize`].
604 /// use std::collections::HashMap;
605 /// let mut map: HashMap<&str, i32> = HashMap::new();
609 #[stable(feature = "rust1", since = "1.0.0")]
610 pub fn reserve(&mut self, additional: usize) {
611 self.base.reserve(additional)
614 /// Tries to reserve capacity for at least `additional` more elements to be inserted
615 /// in the given `HashMap<K, V>`. The collection may reserve more space to avoid
616 /// frequent reallocations.
620 /// If the capacity overflows, or the allocator reports a failure, then an error
626 /// #![feature(try_reserve)]
627 /// use std::collections::HashMap;
629 /// let mut map: HashMap<&str, isize> = HashMap::new();
630 /// map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
633 #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
634 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
635 self.base.try_reserve(additional).map_err(map_try_reserve_error)
638 /// Shrinks the capacity of the map as much as possible. It will drop
639 /// down as much as possible while maintaining the internal rules
640 /// and possibly leaving some space in accordance with the resize policy.
645 /// use std::collections::HashMap;
647 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
648 /// map.insert(1, 2);
649 /// map.insert(3, 4);
650 /// assert!(map.capacity() >= 100);
651 /// map.shrink_to_fit();
652 /// assert!(map.capacity() >= 2);
655 #[stable(feature = "rust1", since = "1.0.0")]
656 pub fn shrink_to_fit(&mut self) {
657 self.base.shrink_to_fit();
660 /// Shrinks the capacity of the map with a lower limit. It will drop
661 /// down no lower than the supplied limit while maintaining the internal rules
662 /// and possibly leaving some space in accordance with the resize policy.
664 /// If the current capacity is less than the lower limit, this is a no-op.
669 /// #![feature(shrink_to)]
670 /// use std::collections::HashMap;
672 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
673 /// map.insert(1, 2);
674 /// map.insert(3, 4);
675 /// assert!(map.capacity() >= 100);
676 /// map.shrink_to(10);
677 /// assert!(map.capacity() >= 10);
678 /// map.shrink_to(0);
679 /// assert!(map.capacity() >= 2);
682 #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")]
683 pub fn shrink_to(&mut self, min_capacity: usize) {
684 self.base.shrink_to(min_capacity);
687 /// Gets the given key's corresponding entry in the map for in-place manipulation.
692 /// use std::collections::HashMap;
694 /// let mut letters = HashMap::new();
696 /// for ch in "a short treatise on fungi".chars() {
697 /// let counter = letters.entry(ch).or_insert(0);
701 /// assert_eq!(letters[&'s'], 2);
702 /// assert_eq!(letters[&'t'], 3);
703 /// assert_eq!(letters[&'u'], 1);
704 /// assert_eq!(letters.get(&'y'), None);
707 #[stable(feature = "rust1", since = "1.0.0")]
708 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
709 map_entry(self.base.rustc_entry(key))
712 /// Returns a reference to the value corresponding to the key.
714 /// The key may be any borrowed form of the map's key type, but
715 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
721 /// use std::collections::HashMap;
723 /// let mut map = HashMap::new();
724 /// map.insert(1, "a");
725 /// assert_eq!(map.get(&1), Some(&"a"));
726 /// assert_eq!(map.get(&2), None);
728 #[stable(feature = "rust1", since = "1.0.0")]
730 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
738 /// Returns the key-value pair corresponding to the supplied key.
740 /// The supplied key may be any borrowed form of the map's key type, but
741 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
747 /// use std::collections::HashMap;
749 /// let mut map = HashMap::new();
750 /// map.insert(1, "a");
751 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
752 /// assert_eq!(map.get_key_value(&2), None);
755 #[stable(feature = "map_get_key_value", since = "1.40.0")]
756 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
761 self.base.get_key_value(k)
764 /// Returns `true` if the map contains a value for the specified key.
766 /// The key may be any borrowed form of the map's key type, but
767 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
773 /// use std::collections::HashMap;
775 /// let mut map = HashMap::new();
776 /// map.insert(1, "a");
777 /// assert_eq!(map.contains_key(&1), true);
778 /// assert_eq!(map.contains_key(&2), false);
781 #[stable(feature = "rust1", since = "1.0.0")]
782 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
787 self.base.contains_key(k)
790 /// Returns a mutable reference to the value corresponding to the key.
792 /// The key may be any borrowed form of the map's key type, but
793 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
799 /// use std::collections::HashMap;
801 /// let mut map = HashMap::new();
802 /// map.insert(1, "a");
803 /// if let Some(x) = map.get_mut(&1) {
806 /// assert_eq!(map[&1], "b");
809 #[stable(feature = "rust1", since = "1.0.0")]
810 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
818 /// Inserts a key-value pair into the map.
820 /// If the map did not have this key present, [`None`] is returned.
822 /// If the map did have this key present, the value is updated, and the old
823 /// value is returned. The key is not updated, though; this matters for
824 /// types that can be `==` without being identical. See the [module-level
825 /// documentation] for more.
827 /// [module-level documentation]: crate::collections#insert-and-complex-keys
832 /// use std::collections::HashMap;
834 /// let mut map = HashMap::new();
835 /// assert_eq!(map.insert(37, "a"), None);
836 /// assert_eq!(map.is_empty(), false);
838 /// map.insert(37, "b");
839 /// assert_eq!(map.insert(37, "c"), Some("b"));
840 /// assert_eq!(map[&37], "c");
843 #[stable(feature = "rust1", since = "1.0.0")]
844 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
845 self.base.insert(k, v)
848 /// Tries to insert a key-value pair into the map, and returns
849 /// a mutable reference to the value in the entry.
851 /// If the map already had this key present, nothing is updated, and
852 /// an error containing the occupied entry and the value is returned.
859 /// #![feature(map_try_insert)]
861 /// use std::collections::HashMap;
863 /// let mut map = HashMap::new();
864 /// assert_eq!(map.try_insert(37, "a").unwrap(), &"a");
866 /// let err = map.try_insert(37, "b").unwrap_err();
867 /// assert_eq!(err.entry.key(), &37);
868 /// assert_eq!(err.entry.get(), &"a");
869 /// assert_eq!(err.value, "b");
871 #[unstable(feature = "map_try_insert", issue = "82766")]
872 pub fn try_insert(&mut self, key: K, value: V) -> Result<&mut V, OccupiedError<'_, K, V>> {
873 match self.entry(key) {
874 Occupied(entry) => Err(OccupiedError { entry, value }),
875 Vacant(entry) => Ok(entry.insert(value)),
879 /// Removes a key from the map, returning the value at the key if the key
880 /// was previously in the map.
882 /// The key may be any borrowed form of the map's key type, but
883 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
889 /// use std::collections::HashMap;
891 /// let mut map = HashMap::new();
892 /// map.insert(1, "a");
893 /// assert_eq!(map.remove(&1), Some("a"));
894 /// assert_eq!(map.remove(&1), None);
896 #[doc(alias = "delete")]
898 #[stable(feature = "rust1", since = "1.0.0")]
899 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
907 /// Removes a key from the map, returning the stored key and value if the
908 /// key was previously in the map.
910 /// The key may be any borrowed form of the map's key type, but
911 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
917 /// use std::collections::HashMap;
920 /// let mut map = HashMap::new();
921 /// map.insert(1, "a");
922 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
923 /// assert_eq!(map.remove(&1), None);
927 #[stable(feature = "hash_map_remove_entry", since = "1.27.0")]
928 pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)>
933 self.base.remove_entry(k)
936 /// Retains only the elements specified by the predicate.
938 /// In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.
943 /// use std::collections::HashMap;
945 /// let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
946 /// map.retain(|&k, _| k % 2 == 0);
947 /// assert_eq!(map.len(), 4);
950 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
951 pub fn retain<F>(&mut self, f: F)
953 F: FnMut(&K, &mut V) -> bool,
958 /// Creates a consuming iterator visiting all the keys in arbitrary order.
959 /// The map cannot be used after calling this.
960 /// The iterator element type is `K`.
965 /// #![feature(map_into_keys_values)]
966 /// use std::collections::HashMap;
968 /// let mut map = HashMap::new();
969 /// map.insert("a", 1);
970 /// map.insert("b", 2);
971 /// map.insert("c", 3);
973 /// let vec: Vec<&str> = map.into_keys().collect();
976 #[unstable(feature = "map_into_keys_values", issue = "75294")]
977 pub fn into_keys(self) -> IntoKeys<K, V> {
978 IntoKeys { inner: self.into_iter() }
981 /// Creates a consuming iterator visiting all the values in arbitrary order.
982 /// The map cannot be used after calling this.
983 /// The iterator element type is `V`.
988 /// #![feature(map_into_keys_values)]
989 /// use std::collections::HashMap;
991 /// let mut map = HashMap::new();
992 /// map.insert("a", 1);
993 /// map.insert("b", 2);
994 /// map.insert("c", 3);
996 /// let vec: Vec<i32> = map.into_values().collect();
999 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1000 pub fn into_values(self) -> IntoValues<K, V> {
1001 IntoValues { inner: self.into_iter() }
1005 impl<K, V, S> HashMap<K, V, S>
1009 /// Creates a raw entry builder for the HashMap.
1011 /// Raw entries provide the lowest level of control for searching and
1012 /// manipulating a map. They must be manually initialized with a hash and
1013 /// then manually searched. After this, insertions into a vacant entry
1014 /// still require an owned key to be provided.
1016 /// Raw entries are useful for such exotic situations as:
1018 /// * Hash memoization
1019 /// * Deferring the creation of an owned key until it is known to be required
1020 /// * Using a search key that doesn't work with the Borrow trait
1021 /// * Using custom comparison logic without newtype wrappers
1023 /// Because raw entries provide much more low-level control, it's much easier
1024 /// to put the HashMap into an inconsistent state which, while memory-safe,
1025 /// will cause the map to produce seemingly random results. Higher-level and
1026 /// more foolproof APIs like `entry` should be preferred when possible.
1028 /// In particular, the hash used to initialized the raw entry must still be
1029 /// consistent with the hash of the key that is ultimately stored in the entry.
1030 /// This is because implementations of HashMap may need to recompute hashes
1031 /// when resizing, at which point only the keys are available.
1033 /// Raw entries give mutable access to the keys. This must not be used
1034 /// to modify how the key would compare or hash, as the map will not re-evaluate
1035 /// where the key should go, meaning the keys may become "lost" if their
1036 /// location does not reflect their state. For instance, if you change a key
1037 /// so that the map now contains keys which compare equal, search may start
1038 /// acting erratically, with two keys randomly masking each other. Implementations
1039 /// are free to assume this doesn't happen (within the limits of memory-safety).
1041 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1042 pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S> {
1043 RawEntryBuilderMut { map: self }
1046 /// Creates a raw immutable entry builder for the HashMap.
1048 /// Raw entries provide the lowest level of control for searching and
1049 /// manipulating a map. They must be manually initialized with a hash and
1050 /// then manually searched.
1052 /// This is useful for
1053 /// * Hash memoization
1054 /// * Using a search key that doesn't work with the Borrow trait
1055 /// * Using custom comparison logic without newtype wrappers
1057 /// Unless you are in such a situation, higher-level and more foolproof APIs like
1058 /// `get` should be preferred.
1060 /// Immutable raw entries have very limited use; you might instead want `raw_entry_mut`.
1062 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1063 pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S> {
1064 RawEntryBuilder { map: self }
1068 #[stable(feature = "rust1", since = "1.0.0")]
1069 impl<K, V, S> Clone for HashMap<K, V, S>
1076 fn clone(&self) -> Self {
1077 Self { base: self.base.clone() }
1081 fn clone_from(&mut self, other: &Self) {
1082 self.base.clone_from(&other.base);
1086 #[stable(feature = "rust1", since = "1.0.0")]
1087 impl<K, V, S> PartialEq for HashMap<K, V, S>
1093 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1094 if self.len() != other.len() {
1098 self.iter().all(|(key, value)| other.get(key).map_or(false, |v| *value == *v))
1102 #[stable(feature = "rust1", since = "1.0.0")]
1103 impl<K, V, S> Eq for HashMap<K, V, S>
1111 #[stable(feature = "rust1", since = "1.0.0")]
1112 impl<K, V, S> Debug for HashMap<K, V, S>
1117 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1118 f.debug_map().entries(self.iter()).finish()
1122 #[stable(feature = "rust1", since = "1.0.0")]
1123 impl<K, V, S> Default for HashMap<K, V, S>
1127 /// Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.
1129 fn default() -> HashMap<K, V, S> {
1130 HashMap::with_hasher(Default::default())
1134 #[stable(feature = "rust1", since = "1.0.0")]
1135 impl<K, Q: ?Sized, V, S> Index<&Q> for HashMap<K, V, S>
1137 K: Eq + Hash + Borrow<Q>,
1143 /// Returns a reference to the value corresponding to the supplied key.
1147 /// Panics if the key is not present in the `HashMap`.
1149 fn index(&self, key: &Q) -> &V {
1150 self.get(key).expect("no entry found for key")
1154 /// An iterator over the entries of a `HashMap`.
1156 /// This `struct` is created by the [`iter`] method on [`HashMap`]. See its
1157 /// documentation for more.
1159 /// [`iter`]: HashMap::iter
1164 /// use std::collections::HashMap;
1166 /// let mut map = HashMap::new();
1167 /// map.insert("a", 1);
1168 /// let iter = map.iter();
1170 #[stable(feature = "rust1", since = "1.0.0")]
1171 pub struct Iter<'a, K: 'a, V: 'a> {
1172 base: base::Iter<'a, K, V>,
1175 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1176 #[stable(feature = "rust1", since = "1.0.0")]
1177 impl<K, V> Clone for Iter<'_, K, V> {
1179 fn clone(&self) -> Self {
1180 Iter { base: self.base.clone() }
1184 #[stable(feature = "std_debug", since = "1.16.0")]
1185 impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
1186 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1187 f.debug_list().entries(self.clone()).finish()
1191 /// A mutable iterator over the entries of a `HashMap`.
1193 /// This `struct` is created by the [`iter_mut`] method on [`HashMap`]. See its
1194 /// documentation for more.
1196 /// [`iter_mut`]: HashMap::iter_mut
1201 /// use std::collections::HashMap;
1203 /// let mut map = HashMap::new();
1204 /// map.insert("a", 1);
1205 /// let iter = map.iter_mut();
1207 #[stable(feature = "rust1", since = "1.0.0")]
1208 pub struct IterMut<'a, K: 'a, V: 'a> {
1209 base: base::IterMut<'a, K, V>,
1212 impl<'a, K, V> IterMut<'a, K, V> {
1213 /// Returns a iterator of references over the remaining items.
1215 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1216 Iter { base: self.base.rustc_iter() }
1220 /// An owning iterator over the entries of a `HashMap`.
1222 /// This `struct` is created by the [`into_iter`] method on [`HashMap`]
1223 /// (provided by the `IntoIterator` trait). See its documentation for more.
1225 /// [`into_iter`]: IntoIterator::into_iter
1230 /// use std::collections::HashMap;
1232 /// let mut map = HashMap::new();
1233 /// map.insert("a", 1);
1234 /// let iter = map.into_iter();
1236 #[stable(feature = "rust1", since = "1.0.0")]
1237 pub struct IntoIter<K, V> {
1238 base: base::IntoIter<K, V>,
1241 impl<K, V> IntoIter<K, V> {
1242 /// Returns a iterator of references over the remaining items.
1244 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1245 Iter { base: self.base.rustc_iter() }
1249 /// An iterator over the keys of a `HashMap`.
1251 /// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
1252 /// documentation for more.
1254 /// [`keys`]: HashMap::keys
1259 /// use std::collections::HashMap;
1261 /// let mut map = HashMap::new();
1262 /// map.insert("a", 1);
1263 /// let iter_keys = map.keys();
1265 #[stable(feature = "rust1", since = "1.0.0")]
1266 pub struct Keys<'a, K: 'a, V: 'a> {
1267 inner: Iter<'a, K, V>,
1270 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1271 #[stable(feature = "rust1", since = "1.0.0")]
1272 impl<K, V> Clone for Keys<'_, K, V> {
1274 fn clone(&self) -> Self {
1275 Keys { inner: self.inner.clone() }
1279 #[stable(feature = "std_debug", since = "1.16.0")]
1280 impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
1281 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1282 f.debug_list().entries(self.clone()).finish()
1286 /// An iterator over the values of a `HashMap`.
1288 /// This `struct` is created by the [`values`] method on [`HashMap`]. See its
1289 /// documentation for more.
1291 /// [`values`]: HashMap::values
1296 /// use std::collections::HashMap;
1298 /// let mut map = HashMap::new();
1299 /// map.insert("a", 1);
1300 /// let iter_values = map.values();
1302 #[stable(feature = "rust1", since = "1.0.0")]
1303 pub struct Values<'a, K: 'a, V: 'a> {
1304 inner: Iter<'a, K, V>,
1307 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1308 #[stable(feature = "rust1", since = "1.0.0")]
1309 impl<K, V> Clone for Values<'_, K, V> {
1311 fn clone(&self) -> Self {
1312 Values { inner: self.inner.clone() }
1316 #[stable(feature = "std_debug", since = "1.16.0")]
1317 impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
1318 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1319 f.debug_list().entries(self.clone()).finish()
1323 /// A draining iterator over the entries of a `HashMap`.
1325 /// This `struct` is created by the [`drain`] method on [`HashMap`]. See its
1326 /// documentation for more.
1328 /// [`drain`]: HashMap::drain
1333 /// use std::collections::HashMap;
1335 /// let mut map = HashMap::new();
1336 /// map.insert("a", 1);
1337 /// let iter = map.drain();
1339 #[stable(feature = "drain", since = "1.6.0")]
1340 pub struct Drain<'a, K: 'a, V: 'a> {
1341 base: base::Drain<'a, K, V>,
1344 impl<'a, K, V> Drain<'a, K, V> {
1345 /// Returns a iterator of references over the remaining items.
1347 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1348 Iter { base: self.base.rustc_iter() }
1352 /// A draining, filtering iterator over the entries of a `HashMap`.
1354 /// This `struct` is created by the [`drain_filter`] method on [`HashMap`].
1356 /// [`drain_filter`]: HashMap::drain_filter
1361 /// #![feature(hash_drain_filter)]
1363 /// use std::collections::HashMap;
1365 /// let mut map = HashMap::new();
1366 /// map.insert("a", 1);
1367 /// let iter = map.drain_filter(|_k, v| *v % 2 == 0);
1369 #[unstable(feature = "hash_drain_filter", issue = "59618")]
1370 pub struct DrainFilter<'a, K, V, F>
1372 F: FnMut(&K, &mut V) -> bool,
1374 base: base::DrainFilter<'a, K, V, F>,
1377 /// A mutable iterator over the values of a `HashMap`.
1379 /// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
1380 /// documentation for more.
1382 /// [`values_mut`]: HashMap::values_mut
1387 /// use std::collections::HashMap;
1389 /// let mut map = HashMap::new();
1390 /// map.insert("a", 1);
1391 /// let iter_values = map.values_mut();
1393 #[stable(feature = "map_values_mut", since = "1.10.0")]
1394 pub struct ValuesMut<'a, K: 'a, V: 'a> {
1395 inner: IterMut<'a, K, V>,
1398 /// An owning iterator over the keys of a `HashMap`.
1400 /// This `struct` is created by the [`into_keys`] method on [`HashMap`].
1401 /// See its documentation for more.
1403 /// [`into_keys`]: HashMap::into_keys
1408 /// #![feature(map_into_keys_values)]
1410 /// use std::collections::HashMap;
1412 /// let mut map = HashMap::new();
1413 /// map.insert("a", 1);
1414 /// let iter_keys = map.into_keys();
1416 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1417 pub struct IntoKeys<K, V> {
1418 inner: IntoIter<K, V>,
1421 /// An owning iterator over the values of a `HashMap`.
1423 /// This `struct` is created by the [`into_values`] method on [`HashMap`].
1424 /// See its documentation for more.
1426 /// [`into_values`]: HashMap::into_values
1431 /// #![feature(map_into_keys_values)]
1433 /// use std::collections::HashMap;
1435 /// let mut map = HashMap::new();
1436 /// map.insert("a", 1);
1437 /// let iter_keys = map.into_values();
1439 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1440 pub struct IntoValues<K, V> {
1441 inner: IntoIter<K, V>,
1444 /// A builder for computing where in a HashMap a key-value pair would be stored.
1446 /// See the [`HashMap::raw_entry_mut`] docs for usage examples.
1447 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1448 pub struct RawEntryBuilderMut<'a, K: 'a, V: 'a, S: 'a> {
1449 map: &'a mut HashMap<K, V, S>,
1452 /// A view into a single entry in a map, which may either be vacant or occupied.
1454 /// This is a lower-level version of [`Entry`].
1456 /// This `enum` is constructed through the [`raw_entry_mut`] method on [`HashMap`],
1457 /// then calling one of the methods of that [`RawEntryBuilderMut`].
1459 /// [`raw_entry_mut`]: HashMap::raw_entry_mut
1460 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1461 pub enum RawEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1462 /// An occupied entry.
1463 Occupied(RawOccupiedEntryMut<'a, K, V, S>),
1465 Vacant(RawVacantEntryMut<'a, K, V, S>),
1468 /// A view into an occupied entry in a `HashMap`.
1469 /// It is part of the [`RawEntryMut`] enum.
1470 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1471 pub struct RawOccupiedEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1472 base: base::RawOccupiedEntryMut<'a, K, V, S>,
1475 /// A view into a vacant entry in a `HashMap`.
1476 /// It is part of the [`RawEntryMut`] enum.
1477 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1478 pub struct RawVacantEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1479 base: base::RawVacantEntryMut<'a, K, V, S>,
1482 /// A builder for computing where in a HashMap a key-value pair would be stored.
1484 /// See the [`HashMap::raw_entry`] docs for usage examples.
1485 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1486 pub struct RawEntryBuilder<'a, K: 'a, V: 'a, S: 'a> {
1487 map: &'a HashMap<K, V, S>,
1490 impl<'a, K, V, S> RawEntryBuilderMut<'a, K, V, S>
1494 /// Creates a `RawEntryMut` from the given key.
1496 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1497 pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S>
1502 map_raw_entry(self.map.base.raw_entry_mut().from_key(k))
1505 /// Creates a `RawEntryMut` from the given key and its hash.
1507 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1508 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> RawEntryMut<'a, K, V, S>
1513 map_raw_entry(self.map.base.raw_entry_mut().from_key_hashed_nocheck(hash, k))
1516 /// Creates a `RawEntryMut` from the given hash.
1518 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1519 pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S>
1521 for<'b> F: FnMut(&'b K) -> bool,
1523 map_raw_entry(self.map.base.raw_entry_mut().from_hash(hash, is_match))
1527 impl<'a, K, V, S> RawEntryBuilder<'a, K, V, S>
1531 /// Access an entry by key.
1533 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1534 pub fn from_key<Q: ?Sized>(self, k: &Q) -> Option<(&'a K, &'a V)>
1539 self.map.base.raw_entry().from_key(k)
1542 /// Access an entry by a key and its hash.
1544 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1545 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> Option<(&'a K, &'a V)>
1550 self.map.base.raw_entry().from_key_hashed_nocheck(hash, k)
1553 /// Access an entry by hash.
1555 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1556 pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>
1558 F: FnMut(&K) -> bool,
1560 self.map.base.raw_entry().from_hash(hash, is_match)
1564 impl<'a, K, V, S> RawEntryMut<'a, K, V, S> {
1565 /// Ensures a value is in the entry by inserting the default if empty, and returns
1566 /// mutable references to the key and value in the entry.
1571 /// #![feature(hash_raw_entry)]
1572 /// use std::collections::HashMap;
1574 /// let mut map: HashMap<&str, u32> = HashMap::new();
1576 /// map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 3);
1577 /// assert_eq!(map["poneyland"], 3);
1579 /// *map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 10).1 *= 2;
1580 /// assert_eq!(map["poneyland"], 6);
1583 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1584 pub fn or_insert(self, default_key: K, default_val: V) -> (&'a mut K, &'a mut V)
1590 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1591 RawEntryMut::Vacant(entry) => entry.insert(default_key, default_val),
1595 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1596 /// and returns mutable references to the key and value in the entry.
1601 /// #![feature(hash_raw_entry)]
1602 /// use std::collections::HashMap;
1604 /// let mut map: HashMap<&str, String> = HashMap::new();
1606 /// map.raw_entry_mut().from_key("poneyland").or_insert_with(|| {
1607 /// ("poneyland", "hoho".to_string())
1610 /// assert_eq!(map["poneyland"], "hoho".to_string());
1613 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1614 pub fn or_insert_with<F>(self, default: F) -> (&'a mut K, &'a mut V)
1616 F: FnOnce() -> (K, V),
1621 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1622 RawEntryMut::Vacant(entry) => {
1623 let (k, v) = default();
1629 /// Provides in-place mutable access to an occupied entry before any
1630 /// potential inserts into the map.
1635 /// #![feature(hash_raw_entry)]
1636 /// use std::collections::HashMap;
1638 /// let mut map: HashMap<&str, u32> = HashMap::new();
1640 /// map.raw_entry_mut()
1641 /// .from_key("poneyland")
1642 /// .and_modify(|_k, v| { *v += 1 })
1643 /// .or_insert("poneyland", 42);
1644 /// assert_eq!(map["poneyland"], 42);
1646 /// map.raw_entry_mut()
1647 /// .from_key("poneyland")
1648 /// .and_modify(|_k, v| { *v += 1 })
1649 /// .or_insert("poneyland", 0);
1650 /// assert_eq!(map["poneyland"], 43);
1653 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1654 pub fn and_modify<F>(self, f: F) -> Self
1656 F: FnOnce(&mut K, &mut V),
1659 RawEntryMut::Occupied(mut entry) => {
1661 let (k, v) = entry.get_key_value_mut();
1664 RawEntryMut::Occupied(entry)
1666 RawEntryMut::Vacant(entry) => RawEntryMut::Vacant(entry),
1671 impl<'a, K, V, S> RawOccupiedEntryMut<'a, K, V, S> {
1672 /// Gets a reference to the key in the entry.
1674 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1675 pub fn key(&self) -> &K {
1679 /// Gets a mutable reference to the key in the entry.
1681 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1682 pub fn key_mut(&mut self) -> &mut K {
1686 /// Converts the entry into a mutable reference to the key in the entry
1687 /// with a lifetime bound to the map itself.
1689 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1690 pub fn into_key(self) -> &'a mut K {
1691 self.base.into_key()
1694 /// Gets a reference to the value in the entry.
1696 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1697 pub fn get(&self) -> &V {
1701 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
1702 /// with a lifetime bound to the map itself.
1704 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1705 pub fn into_mut(self) -> &'a mut V {
1706 self.base.into_mut()
1709 /// Gets a mutable reference to the value in the entry.
1711 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1712 pub fn get_mut(&mut self) -> &mut V {
1716 /// Gets a reference to the key and value in the entry.
1718 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1719 pub fn get_key_value(&mut self) -> (&K, &V) {
1720 self.base.get_key_value()
1723 /// Gets a mutable reference to the key and value in the entry.
1725 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1726 pub fn get_key_value_mut(&mut self) -> (&mut K, &mut V) {
1727 self.base.get_key_value_mut()
1730 /// Converts the `OccupiedEntry` into a mutable reference to the key and value in the entry
1731 /// with a lifetime bound to the map itself.
1733 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1734 pub fn into_key_value(self) -> (&'a mut K, &'a mut V) {
1735 self.base.into_key_value()
1738 /// Sets the value of the entry, and returns the entry's old value.
1740 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1741 pub fn insert(&mut self, value: V) -> V {
1742 self.base.insert(value)
1745 /// Sets the value of the entry, and returns the entry's old value.
1747 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1748 pub fn insert_key(&mut self, key: K) -> K {
1749 self.base.insert_key(key)
1752 /// Takes the value out of the entry, and returns it.
1754 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1755 pub fn remove(self) -> V {
1759 /// Take the ownership of the key and value from the map.
1761 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1762 pub fn remove_entry(self) -> (K, V) {
1763 self.base.remove_entry()
1767 impl<'a, K, V, S> RawVacantEntryMut<'a, K, V, S> {
1768 /// Sets the value of the entry with the `VacantEntry`'s key,
1769 /// and returns a mutable reference to it.
1771 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1772 pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
1777 self.base.insert(key, value)
1780 /// Sets the value of the entry with the VacantEntry's key,
1781 /// and returns a mutable reference to it.
1783 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1784 pub fn insert_hashed_nocheck(self, hash: u64, key: K, value: V) -> (&'a mut K, &'a mut V)
1789 self.base.insert_hashed_nocheck(hash, key, value)
1793 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1794 impl<K, V, S> Debug for RawEntryBuilderMut<'_, K, V, S> {
1795 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1796 f.debug_struct("RawEntryBuilder").finish()
1800 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1801 impl<K: Debug, V: Debug, S> Debug for RawEntryMut<'_, K, V, S> {
1802 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1804 RawEntryMut::Vacant(ref v) => f.debug_tuple("RawEntry").field(v).finish(),
1805 RawEntryMut::Occupied(ref o) => f.debug_tuple("RawEntry").field(o).finish(),
1810 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1811 impl<K: Debug, V: Debug, S> Debug for RawOccupiedEntryMut<'_, K, V, S> {
1812 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1813 f.debug_struct("RawOccupiedEntryMut")
1814 .field("key", self.key())
1815 .field("value", self.get())
1820 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1821 impl<K, V, S> Debug for RawVacantEntryMut<'_, K, V, S> {
1822 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1823 f.debug_struct("RawVacantEntryMut").finish()
1827 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1828 impl<K, V, S> Debug for RawEntryBuilder<'_, K, V, S> {
1829 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1830 f.debug_struct("RawEntryBuilder").finish()
1834 /// A view into a single entry in a map, which may either be vacant or occupied.
1836 /// This `enum` is constructed from the [`entry`] method on [`HashMap`].
1838 /// [`entry`]: HashMap::entry
1839 #[stable(feature = "rust1", since = "1.0.0")]
1840 pub enum Entry<'a, K: 'a, V: 'a> {
1841 /// An occupied entry.
1842 #[stable(feature = "rust1", since = "1.0.0")]
1843 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
1846 #[stable(feature = "rust1", since = "1.0.0")]
1847 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
1850 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1851 impl<K: Debug, V: Debug> Debug for Entry<'_, K, V> {
1852 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1854 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
1855 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
1860 /// A view into an occupied entry in a `HashMap`.
1861 /// It is part of the [`Entry`] enum.
1862 #[stable(feature = "rust1", since = "1.0.0")]
1863 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1864 base: base::RustcOccupiedEntry<'a, K, V>,
1867 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1868 impl<K: Debug, V: Debug> Debug for OccupiedEntry<'_, K, V> {
1869 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1870 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
1874 /// A view into a vacant entry in a `HashMap`.
1875 /// It is part of the [`Entry`] enum.
1876 #[stable(feature = "rust1", since = "1.0.0")]
1877 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1878 base: base::RustcVacantEntry<'a, K, V>,
1881 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1882 impl<K: Debug, V> Debug for VacantEntry<'_, K, V> {
1883 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1884 f.debug_tuple("VacantEntry").field(self.key()).finish()
1888 /// The error returned by [`try_insert`](HashMap::try_insert) when the key already exists.
1890 /// Contains the occupied entry, and the value that was not inserted.
1891 #[unstable(feature = "map_try_insert", issue = "82766")]
1892 pub struct OccupiedError<'a, K: 'a, V: 'a> {
1893 /// The entry in the map that was already occupied.
1894 pub entry: OccupiedEntry<'a, K, V>,
1895 /// The value which was not inserted, because the entry was already occupied.
1899 #[unstable(feature = "map_try_insert", issue = "82766")]
1900 impl<K: Debug, V: Debug> Debug for OccupiedError<'_, K, V> {
1901 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1902 f.debug_struct("OccupiedError")
1903 .field("key", self.entry.key())
1904 .field("old_value", self.entry.get())
1905 .field("new_value", &self.value)
1910 #[unstable(feature = "map_try_insert", issue = "82766")]
1911 impl<'a, K: Debug, V: Debug> fmt::Display for OccupiedError<'a, K, V> {
1912 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1915 "failed to insert {:?}, key {:?} already exists with value {:?}",
1923 #[stable(feature = "rust1", since = "1.0.0")]
1924 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> {
1925 type Item = (&'a K, &'a V);
1926 type IntoIter = Iter<'a, K, V>;
1929 fn into_iter(self) -> Iter<'a, K, V> {
1934 #[stable(feature = "rust1", since = "1.0.0")]
1935 impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S> {
1936 type Item = (&'a K, &'a mut V);
1937 type IntoIter = IterMut<'a, K, V>;
1940 fn into_iter(self) -> IterMut<'a, K, V> {
1945 #[stable(feature = "rust1", since = "1.0.0")]
1946 impl<K, V, S> IntoIterator for HashMap<K, V, S> {
1948 type IntoIter = IntoIter<K, V>;
1950 /// Creates a consuming iterator, that is, one that moves each key-value
1951 /// pair out of the map in arbitrary order. The map cannot be used after
1957 /// use std::collections::HashMap;
1959 /// let mut map = HashMap::new();
1960 /// map.insert("a", 1);
1961 /// map.insert("b", 2);
1962 /// map.insert("c", 3);
1964 /// // Not possible with .iter()
1965 /// let vec: Vec<(&str, i32)> = map.into_iter().collect();
1968 fn into_iter(self) -> IntoIter<K, V> {
1969 IntoIter { base: self.base.into_iter() }
1973 #[stable(feature = "rust1", since = "1.0.0")]
1974 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1975 type Item = (&'a K, &'a V);
1978 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1982 fn size_hint(&self) -> (usize, Option<usize>) {
1983 self.base.size_hint()
1986 #[stable(feature = "rust1", since = "1.0.0")]
1987 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1989 fn len(&self) -> usize {
1994 #[stable(feature = "fused", since = "1.26.0")]
1995 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1997 #[stable(feature = "rust1", since = "1.0.0")]
1998 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1999 type Item = (&'a K, &'a mut V);
2002 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
2006 fn size_hint(&self) -> (usize, Option<usize>) {
2007 self.base.size_hint()
2010 #[stable(feature = "rust1", since = "1.0.0")]
2011 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
2013 fn len(&self) -> usize {
2017 #[stable(feature = "fused", since = "1.26.0")]
2018 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
2020 #[stable(feature = "std_debug", since = "1.16.0")]
2021 impl<K, V> fmt::Debug for IterMut<'_, K, V>
2026 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2027 f.debug_list().entries(self.iter()).finish()
2031 #[stable(feature = "rust1", since = "1.0.0")]
2032 impl<K, V> Iterator for IntoIter<K, V> {
2036 fn next(&mut self) -> Option<(K, V)> {
2040 fn size_hint(&self) -> (usize, Option<usize>) {
2041 self.base.size_hint()
2044 #[stable(feature = "rust1", since = "1.0.0")]
2045 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
2047 fn len(&self) -> usize {
2051 #[stable(feature = "fused", since = "1.26.0")]
2052 impl<K, V> FusedIterator for IntoIter<K, V> {}
2054 #[stable(feature = "std_debug", since = "1.16.0")]
2055 impl<K: Debug, V: Debug> fmt::Debug for IntoIter<K, V> {
2056 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2057 f.debug_list().entries(self.iter()).finish()
2061 #[stable(feature = "rust1", since = "1.0.0")]
2062 impl<'a, K, V> Iterator for Keys<'a, K, V> {
2066 fn next(&mut self) -> Option<&'a K> {
2067 self.inner.next().map(|(k, _)| k)
2070 fn size_hint(&self) -> (usize, Option<usize>) {
2071 self.inner.size_hint()
2074 #[stable(feature = "rust1", since = "1.0.0")]
2075 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
2077 fn len(&self) -> usize {
2081 #[stable(feature = "fused", since = "1.26.0")]
2082 impl<K, V> FusedIterator for Keys<'_, K, V> {}
2084 #[stable(feature = "rust1", since = "1.0.0")]
2085 impl<'a, K, V> Iterator for Values<'a, K, V> {
2089 fn next(&mut self) -> Option<&'a V> {
2090 self.inner.next().map(|(_, v)| v)
2093 fn size_hint(&self) -> (usize, Option<usize>) {
2094 self.inner.size_hint()
2097 #[stable(feature = "rust1", since = "1.0.0")]
2098 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
2100 fn len(&self) -> usize {
2104 #[stable(feature = "fused", since = "1.26.0")]
2105 impl<K, V> FusedIterator for Values<'_, K, V> {}
2107 #[stable(feature = "map_values_mut", since = "1.10.0")]
2108 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
2109 type Item = &'a mut V;
2112 fn next(&mut self) -> Option<&'a mut V> {
2113 self.inner.next().map(|(_, v)| v)
2116 fn size_hint(&self) -> (usize, Option<usize>) {
2117 self.inner.size_hint()
2120 #[stable(feature = "map_values_mut", since = "1.10.0")]
2121 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
2123 fn len(&self) -> usize {
2127 #[stable(feature = "fused", since = "1.26.0")]
2128 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
2130 #[stable(feature = "std_debug", since = "1.16.0")]
2131 impl<K, V: fmt::Debug> fmt::Debug for ValuesMut<'_, K, V> {
2132 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2133 f.debug_list().entries(self.inner.iter().map(|(_, val)| val)).finish()
2137 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2138 impl<K, V> Iterator for IntoKeys<K, V> {
2142 fn next(&mut self) -> Option<K> {
2143 self.inner.next().map(|(k, _)| k)
2146 fn size_hint(&self) -> (usize, Option<usize>) {
2147 self.inner.size_hint()
2150 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2151 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
2153 fn len(&self) -> usize {
2157 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2158 impl<K, V> FusedIterator for IntoKeys<K, V> {}
2160 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2161 impl<K: Debug, V> fmt::Debug for IntoKeys<K, V> {
2162 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2163 f.debug_list().entries(self.inner.iter().map(|(k, _)| k)).finish()
2167 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2168 impl<K, V> Iterator for IntoValues<K, V> {
2172 fn next(&mut self) -> Option<V> {
2173 self.inner.next().map(|(_, v)| v)
2176 fn size_hint(&self) -> (usize, Option<usize>) {
2177 self.inner.size_hint()
2180 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2181 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
2183 fn len(&self) -> usize {
2187 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2188 impl<K, V> FusedIterator for IntoValues<K, V> {}
2190 #[unstable(feature = "map_into_keys_values", issue = "75294")]
2191 impl<K, V: Debug> fmt::Debug for IntoValues<K, V> {
2192 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2193 f.debug_list().entries(self.inner.iter().map(|(_, v)| v)).finish()
2197 #[stable(feature = "drain", since = "1.6.0")]
2198 impl<'a, K, V> Iterator for Drain<'a, K, V> {
2202 fn next(&mut self) -> Option<(K, V)> {
2206 fn size_hint(&self) -> (usize, Option<usize>) {
2207 self.base.size_hint()
2210 #[stable(feature = "drain", since = "1.6.0")]
2211 impl<K, V> ExactSizeIterator for Drain<'_, K, V> {
2213 fn len(&self) -> usize {
2217 #[stable(feature = "fused", since = "1.26.0")]
2218 impl<K, V> FusedIterator for Drain<'_, K, V> {}
2220 #[stable(feature = "std_debug", since = "1.16.0")]
2221 impl<K, V> fmt::Debug for Drain<'_, K, V>
2226 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2227 f.debug_list().entries(self.iter()).finish()
2231 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2232 impl<K, V, F> Iterator for DrainFilter<'_, K, V, F>
2234 F: FnMut(&K, &mut V) -> bool,
2239 fn next(&mut self) -> Option<(K, V)> {
2243 fn size_hint(&self) -> (usize, Option<usize>) {
2244 self.base.size_hint()
2248 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2249 impl<K, V, F> FusedIterator for DrainFilter<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
2251 #[unstable(feature = "hash_drain_filter", issue = "59618")]
2252 impl<'a, K, V, F> fmt::Debug for DrainFilter<'a, K, V, F>
2254 F: FnMut(&K, &mut V) -> bool,
2256 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2257 f.pad("DrainFilter { .. }")
2261 impl<'a, K, V> Entry<'a, K, V> {
2262 /// Ensures a value is in the entry by inserting the default if empty, and returns
2263 /// a mutable reference to the value in the entry.
2268 /// use std::collections::HashMap;
2270 /// let mut map: HashMap<&str, u32> = HashMap::new();
2272 /// map.entry("poneyland").or_insert(3);
2273 /// assert_eq!(map["poneyland"], 3);
2275 /// *map.entry("poneyland").or_insert(10) *= 2;
2276 /// assert_eq!(map["poneyland"], 6);
2279 #[stable(feature = "rust1", since = "1.0.0")]
2280 pub fn or_insert(self, default: V) -> &'a mut V {
2282 Occupied(entry) => entry.into_mut(),
2283 Vacant(entry) => entry.insert(default),
2287 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2288 /// and returns a mutable reference to the value in the entry.
2293 /// use std::collections::HashMap;
2295 /// let mut map: HashMap<&str, String> = HashMap::new();
2296 /// let s = "hoho".to_string();
2298 /// map.entry("poneyland").or_insert_with(|| s);
2300 /// assert_eq!(map["poneyland"], "hoho".to_string());
2303 #[stable(feature = "rust1", since = "1.0.0")]
2304 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2306 Occupied(entry) => entry.into_mut(),
2307 Vacant(entry) => entry.insert(default()),
2311 /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
2312 /// This method allows for generating key-derived values for insertion by providing the default
2313 /// function a reference to the key that was moved during the `.entry(key)` method call.
2315 /// The reference to the moved key is provided so that cloning or copying the key is
2316 /// unnecessary, unlike with `.or_insert_with(|| ... )`.
2321 /// use std::collections::HashMap;
2323 /// let mut map: HashMap<&str, usize> = HashMap::new();
2325 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2327 /// assert_eq!(map["poneyland"], 9);
2330 #[stable(feature = "or_insert_with_key", since = "1.50.0")]
2331 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2333 Occupied(entry) => entry.into_mut(),
2335 let value = default(entry.key());
2341 /// Returns a reference to this entry's key.
2346 /// use std::collections::HashMap;
2348 /// let mut map: HashMap<&str, u32> = HashMap::new();
2349 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2352 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2353 pub fn key(&self) -> &K {
2355 Occupied(ref entry) => entry.key(),
2356 Vacant(ref entry) => entry.key(),
2360 /// Provides in-place mutable access to an occupied entry before any
2361 /// potential inserts into the map.
2366 /// use std::collections::HashMap;
2368 /// let mut map: HashMap<&str, u32> = HashMap::new();
2370 /// map.entry("poneyland")
2371 /// .and_modify(|e| { *e += 1 })
2373 /// assert_eq!(map["poneyland"], 42);
2375 /// map.entry("poneyland")
2376 /// .and_modify(|e| { *e += 1 })
2378 /// assert_eq!(map["poneyland"], 43);
2381 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2382 pub fn and_modify<F>(self, f: F) -> Self
2387 Occupied(mut entry) => {
2391 Vacant(entry) => Vacant(entry),
2395 /// Sets the value of the entry, and returns an `OccupiedEntry`.
2400 /// #![feature(entry_insert)]
2401 /// use std::collections::HashMap;
2403 /// let mut map: HashMap<&str, String> = HashMap::new();
2404 /// let entry = map.entry("poneyland").insert("hoho".to_string());
2406 /// assert_eq!(entry.key(), &"poneyland");
2409 #[unstable(feature = "entry_insert", issue = "65225")]
2410 pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V> {
2412 Occupied(mut entry) => {
2413 entry.insert(value);
2416 Vacant(entry) => entry.insert_entry(value),
2421 impl<'a, K, V: Default> Entry<'a, K, V> {
2422 /// Ensures a value is in the entry by inserting the default value if empty,
2423 /// and returns a mutable reference to the value in the entry.
2429 /// use std::collections::HashMap;
2431 /// let mut map: HashMap<&str, Option<u32>> = HashMap::new();
2432 /// map.entry("poneyland").or_default();
2434 /// assert_eq!(map["poneyland"], None);
2438 #[stable(feature = "entry_or_default", since = "1.28.0")]
2439 pub fn or_default(self) -> &'a mut V {
2441 Occupied(entry) => entry.into_mut(),
2442 Vacant(entry) => entry.insert(Default::default()),
2447 impl<'a, K, V> OccupiedEntry<'a, K, V> {
2448 /// Gets a reference to the key in the entry.
2453 /// use std::collections::HashMap;
2455 /// let mut map: HashMap<&str, u32> = HashMap::new();
2456 /// map.entry("poneyland").or_insert(12);
2457 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2460 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2461 pub fn key(&self) -> &K {
2465 /// Take the ownership of the key and value from the map.
2470 /// use std::collections::HashMap;
2471 /// use std::collections::hash_map::Entry;
2473 /// let mut map: HashMap<&str, u32> = HashMap::new();
2474 /// map.entry("poneyland").or_insert(12);
2476 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2477 /// // We delete the entry from the map.
2478 /// o.remove_entry();
2481 /// assert_eq!(map.contains_key("poneyland"), false);
2484 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2485 pub fn remove_entry(self) -> (K, V) {
2486 self.base.remove_entry()
2489 /// Gets a reference to the value in the entry.
2494 /// use std::collections::HashMap;
2495 /// use std::collections::hash_map::Entry;
2497 /// let mut map: HashMap<&str, u32> = HashMap::new();
2498 /// map.entry("poneyland").or_insert(12);
2500 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2501 /// assert_eq!(o.get(), &12);
2505 #[stable(feature = "rust1", since = "1.0.0")]
2506 pub fn get(&self) -> &V {
2510 /// Gets a mutable reference to the value in the entry.
2512 /// If you need a reference to the `OccupiedEntry` which may outlive the
2513 /// destruction of the `Entry` value, see [`into_mut`].
2515 /// [`into_mut`]: Self::into_mut
2520 /// use std::collections::HashMap;
2521 /// use std::collections::hash_map::Entry;
2523 /// let mut map: HashMap<&str, u32> = HashMap::new();
2524 /// map.entry("poneyland").or_insert(12);
2526 /// assert_eq!(map["poneyland"], 12);
2527 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2528 /// *o.get_mut() += 10;
2529 /// assert_eq!(*o.get(), 22);
2531 /// // We can use the same Entry multiple times.
2532 /// *o.get_mut() += 2;
2535 /// assert_eq!(map["poneyland"], 24);
2538 #[stable(feature = "rust1", since = "1.0.0")]
2539 pub fn get_mut(&mut self) -> &mut V {
2543 /// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
2544 /// with a lifetime bound to the map itself.
2546 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2548 /// [`get_mut`]: Self::get_mut
2553 /// use std::collections::HashMap;
2554 /// use std::collections::hash_map::Entry;
2556 /// let mut map: HashMap<&str, u32> = HashMap::new();
2557 /// map.entry("poneyland").or_insert(12);
2559 /// assert_eq!(map["poneyland"], 12);
2560 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2561 /// *o.into_mut() += 10;
2564 /// assert_eq!(map["poneyland"], 22);
2567 #[stable(feature = "rust1", since = "1.0.0")]
2568 pub fn into_mut(self) -> &'a mut V {
2569 self.base.into_mut()
2572 /// Sets the value of the entry, and returns the entry's old value.
2577 /// use std::collections::HashMap;
2578 /// use std::collections::hash_map::Entry;
2580 /// let mut map: HashMap<&str, u32> = HashMap::new();
2581 /// map.entry("poneyland").or_insert(12);
2583 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2584 /// assert_eq!(o.insert(15), 12);
2587 /// assert_eq!(map["poneyland"], 15);
2590 #[stable(feature = "rust1", since = "1.0.0")]
2591 pub fn insert(&mut self, value: V) -> V {
2592 self.base.insert(value)
2595 /// Takes the value out of the entry, and returns it.
2600 /// use std::collections::HashMap;
2601 /// use std::collections::hash_map::Entry;
2603 /// let mut map: HashMap<&str, u32> = HashMap::new();
2604 /// map.entry("poneyland").or_insert(12);
2606 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2607 /// assert_eq!(o.remove(), 12);
2610 /// assert_eq!(map.contains_key("poneyland"), false);
2613 #[stable(feature = "rust1", since = "1.0.0")]
2614 pub fn remove(self) -> V {
2618 /// Replaces the entry, returning the old key and value. The new key in the hash map will be
2619 /// the key used to create this entry.
2624 /// #![feature(map_entry_replace)]
2625 /// use std::collections::hash_map::{Entry, HashMap};
2626 /// use std::rc::Rc;
2628 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2629 /// map.insert(Rc::new("Stringthing".to_string()), 15);
2631 /// let my_key = Rc::new("Stringthing".to_string());
2633 /// if let Entry::Occupied(entry) = map.entry(my_key) {
2634 /// // Also replace the key with a handle to our other key.
2635 /// let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
2640 #[unstable(feature = "map_entry_replace", issue = "44286")]
2641 pub fn replace_entry(self, value: V) -> (K, V) {
2642 self.base.replace_entry(value)
2645 /// Replaces the key in the hash map with the key used to create this entry.
2650 /// #![feature(map_entry_replace)]
2651 /// use std::collections::hash_map::{Entry, HashMap};
2652 /// use std::rc::Rc;
2654 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2655 /// let known_strings: Vec<Rc<String>> = Vec::new();
2657 /// // Initialise known strings, run program, etc.
2659 /// reclaim_memory(&mut map, &known_strings);
2661 /// fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
2662 /// for s in known_strings {
2663 /// if let Entry::Occupied(entry) = map.entry(Rc::clone(s)) {
2664 /// // Replaces the entry's key with our version of it in `known_strings`.
2665 /// entry.replace_key();
2671 #[unstable(feature = "map_entry_replace", issue = "44286")]
2672 pub fn replace_key(self) -> K {
2673 self.base.replace_key()
2677 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
2678 /// Gets a reference to the key that would be used when inserting a value
2679 /// through the `VacantEntry`.
2684 /// use std::collections::HashMap;
2686 /// let mut map: HashMap<&str, u32> = HashMap::new();
2687 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2690 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2691 pub fn key(&self) -> &K {
2695 /// Take ownership of the key.
2700 /// use std::collections::HashMap;
2701 /// use std::collections::hash_map::Entry;
2703 /// let mut map: HashMap<&str, u32> = HashMap::new();
2705 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2710 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2711 pub fn into_key(self) -> K {
2712 self.base.into_key()
2715 /// Sets the value of the entry with the `VacantEntry`'s key,
2716 /// and returns a mutable reference to it.
2721 /// use std::collections::HashMap;
2722 /// use std::collections::hash_map::Entry;
2724 /// let mut map: HashMap<&str, u32> = HashMap::new();
2726 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2729 /// assert_eq!(map["poneyland"], 37);
2732 #[stable(feature = "rust1", since = "1.0.0")]
2733 pub fn insert(self, value: V) -> &'a mut V {
2734 self.base.insert(value)
2737 /// Sets the value of the entry with the `VacantEntry`'s key,
2738 /// and returns an `OccupiedEntry`.
2743 /// use std::collections::HashMap;
2744 /// use std::collections::hash_map::Entry;
2746 /// let mut map: HashMap<&str, u32> = HashMap::new();
2748 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2751 /// assert_eq!(map["poneyland"], 37);
2754 fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> {
2755 let base = self.base.insert_entry(value);
2756 OccupiedEntry { base }
2760 #[stable(feature = "rust1", since = "1.0.0")]
2761 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
2764 S: BuildHasher + Default,
2766 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> HashMap<K, V, S> {
2767 let mut map = HashMap::with_hasher(Default::default());
2773 /// Inserts all new key-values from the iterator and replaces values with existing
2774 /// keys with new values returned from the iterator.
2775 #[stable(feature = "rust1", since = "1.0.0")]
2776 impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>
2782 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
2783 self.base.extend(iter)
2787 fn extend_one(&mut self, (k, v): (K, V)) {
2788 self.base.insert(k, v);
2792 fn extend_reserve(&mut self, additional: usize) {
2793 // self.base.extend_reserve(additional);
2794 // FIXME: hashbrown should implement this method.
2795 // But until then, use the same reservation logic:
2797 // Reserve the entire hint lower bound if the map is empty.
2798 // Otherwise reserve half the hint (rounded up), so the map
2799 // will only resize twice in the worst case.
2800 let reserve = if self.is_empty() { additional } else { (additional + 1) / 2 };
2801 self.base.reserve(reserve);
2805 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
2806 impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>
2808 K: Eq + Hash + Copy,
2813 fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T) {
2814 self.base.extend(iter)
2818 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2819 self.base.insert(k, v);
2823 fn extend_reserve(&mut self, additional: usize) {
2824 Extend::<(K, V)>::extend_reserve(self, additional)
2828 /// `RandomState` is the default state for [`HashMap`] types.
2830 /// A particular instance `RandomState` will create the same instances of
2831 /// [`Hasher`], but the hashers created by two different `RandomState`
2832 /// instances are unlikely to produce the same result for the same values.
2837 /// use std::collections::HashMap;
2838 /// use std::collections::hash_map::RandomState;
2840 /// let s = RandomState::new();
2841 /// let mut map = HashMap::with_hasher(s);
2842 /// map.insert(1, 2);
2845 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2846 pub struct RandomState {
2852 /// Constructs a new `RandomState` that is initialized with random keys.
2857 /// use std::collections::hash_map::RandomState;
2859 /// let s = RandomState::new();
2862 #[allow(deprecated)]
2864 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2865 pub fn new() -> RandomState {
2866 // Historically this function did not cache keys from the OS and instead
2867 // simply always called `rand::thread_rng().gen()` twice. In #31356 it
2868 // was discovered, however, that because we re-seed the thread-local RNG
2869 // from the OS periodically that this can cause excessive slowdown when
2870 // many hash maps are created on a thread. To solve this performance
2871 // trap we cache the first set of randomly generated keys per-thread.
2873 // Later in #36481 it was discovered that exposing a deterministic
2874 // iteration order allows a form of DOS attack. To counter that we
2875 // increment one of the seeds on every RandomState creation, giving
2876 // every corresponding HashMap a different iteration order.
2877 thread_local!(static KEYS: Cell<(u64, u64)> = {
2878 Cell::new(sys::hashmap_random_keys())
2882 let (k0, k1) = keys.get();
2883 keys.set((k0.wrapping_add(1), k1));
2884 RandomState { k0, k1 }
2889 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2890 impl BuildHasher for RandomState {
2891 type Hasher = DefaultHasher;
2893 #[allow(deprecated)]
2894 fn build_hasher(&self) -> DefaultHasher {
2895 DefaultHasher(SipHasher13::new_with_keys(self.k0, self.k1))
2899 /// The default [`Hasher`] used by [`RandomState`].
2901 /// The internal algorithm is not specified, and so it and its hashes should
2902 /// not be relied upon over releases.
2903 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2904 #[allow(deprecated)]
2905 #[derive(Clone, Debug)]
2906 pub struct DefaultHasher(SipHasher13);
2908 impl DefaultHasher {
2909 /// Creates a new `DefaultHasher`.
2911 /// This hasher is not guaranteed to be the same as all other
2912 /// `DefaultHasher` instances, but is the same as all other `DefaultHasher`
2913 /// instances created through `new` or `default`.
2914 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2915 #[allow(deprecated)]
2916 pub fn new() -> DefaultHasher {
2917 DefaultHasher(SipHasher13::new_with_keys(0, 0))
2921 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2922 impl Default for DefaultHasher {
2923 /// Creates a new `DefaultHasher` using [`new`].
2924 /// See its documentation for more.
2926 /// [`new`]: DefaultHasher::new
2927 fn default() -> DefaultHasher {
2928 DefaultHasher::new()
2932 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2933 impl Hasher for DefaultHasher {
2935 fn write(&mut self, msg: &[u8]) {
2940 fn finish(&self) -> u64 {
2945 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2946 impl Default for RandomState {
2947 /// Constructs a new `RandomState`.
2949 fn default() -> RandomState {
2954 #[stable(feature = "std_debug", since = "1.16.0")]
2955 impl fmt::Debug for RandomState {
2956 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2957 f.pad("RandomState { .. }")
2962 fn map_entry<'a, K: 'a, V: 'a>(raw: base::RustcEntry<'a, K, V>) -> Entry<'a, K, V> {
2964 base::RustcEntry::Occupied(base) => Entry::Occupied(OccupiedEntry { base }),
2965 base::RustcEntry::Vacant(base) => Entry::Vacant(VacantEntry { base }),
2970 pub(super) fn map_try_reserve_error(err: hashbrown::TryReserveError) -> TryReserveError {
2972 hashbrown::TryReserveError::CapacityOverflow => TryReserveError::CapacityOverflow,
2973 hashbrown::TryReserveError::AllocError { layout } => {
2974 TryReserveError::AllocError { layout, non_exhaustive: () }
2980 fn map_raw_entry<'a, K: 'a, V: 'a, S: 'a>(
2981 raw: base::RawEntryMut<'a, K, V, S>,
2982 ) -> RawEntryMut<'a, K, V, S> {
2984 base::RawEntryMut::Occupied(base) => RawEntryMut::Occupied(RawOccupiedEntryMut { base }),
2985 base::RawEntryMut::Vacant(base) => RawEntryMut::Vacant(RawVacantEntryMut { base }),
2990 fn assert_covariance() {
2991 fn map_key<'new>(v: HashMap<&'static str, u8>) -> HashMap<&'new str, u8> {
2994 fn map_val<'new>(v: HashMap<u8, &'static str>) -> HashMap<u8, &'new str> {
2997 fn iter_key<'a, 'new>(v: Iter<'a, &'static str, u8>) -> Iter<'a, &'new str, u8> {
3000 fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
3003 fn into_iter_key<'new>(v: IntoIter<&'static str, u8>) -> IntoIter<&'new str, u8> {
3006 fn into_iter_val<'new>(v: IntoIter<u8, &'static str>) -> IntoIter<u8, &'new str> {
3009 fn keys_key<'a, 'new>(v: Keys<'a, &'static str, u8>) -> Keys<'a, &'new str, u8> {
3012 fn keys_val<'a, 'new>(v: Keys<'a, u8, &'static str>) -> Keys<'a, u8, &'new str> {
3015 fn values_key<'a, 'new>(v: Values<'a, &'static str, u8>) -> Values<'a, &'new str, u8> {
3018 fn values_val<'a, 'new>(v: Values<'a, u8, &'static str>) -> Values<'a, u8, &'new str> {
3022 d: Drain<'static, &'static str, &'static str>,
3023 ) -> Drain<'new, &'new str, &'new str> {