6 use hashbrown::hash_map as base;
8 use crate::borrow::Borrow;
10 use crate::collections::TryReserveError;
11 use crate::fmt::{self, Debug};
13 use crate::hash::{BuildHasher, Hash, Hasher, SipHasher13};
14 use crate::iter::{FromIterator, FusedIterator};
15 use crate::ops::Index;
18 /// A hash map implemented with quadratic probing and SIMD lookup.
20 /// By default, `HashMap` uses a hashing algorithm selected to provide
21 /// resistance against HashDoS attacks. The algorithm is randomly seeded, and a
22 /// reasonable best-effort is made to generate this seed from a high quality,
23 /// secure source of randomness provided by the host without blocking the
24 /// program. Because of this, the randomness of the seed depends on the output
25 /// quality of the system's random number generator when the seed is created.
26 /// In particular, seeds generated when the system's entropy pool is abnormally
27 /// low such as during system boot may be of a lower quality.
29 /// The default hashing algorithm is currently SipHash 1-3, though this is
30 /// subject to change at any point in the future. While its performance is very
31 /// competitive for medium sized keys, other hashing algorithms will outperform
32 /// it for small keys such as integers as well as large keys such as long
33 /// strings, though those algorithms will typically *not* protect against
34 /// attacks such as HashDoS.
36 /// The hashing algorithm can be replaced on a per-`HashMap` basis using the
37 /// [`default`], [`with_hasher`], and [`with_capacity_and_hasher`] methods. Many
38 /// alternative algorithms are available on crates.io, such as the [`fnv`] crate.
40 /// It is required that the keys implement the [`Eq`] and [`Hash`] traits, although
41 /// this can frequently be achieved by using `#[derive(PartialEq, Eq, Hash)]`.
42 /// If you implement these yourself, it is important that the following
46 /// k1 == k2 -> hash(k1) == hash(k2)
49 /// In other words, if two keys are equal, their hashes must be equal.
51 /// It is a logic error for a key to be modified in such a way that the key's
52 /// hash, as determined by the [`Hash`] trait, or its equality, as determined by
53 /// the [`Eq`] trait, changes while it is in the map. This is normally only
54 /// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
56 /// The hash table implementation is a Rust port of Google's [SwissTable].
57 /// The original C++ version of SwissTable can be found [here], and this
58 /// [CppCon talk] gives an overview of how the algorithm works.
60 /// [SwissTable]: https://abseil.io/blog/20180927-swisstables
61 /// [here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h
62 /// [CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4
67 /// use std::collections::HashMap;
69 /// // Type inference lets us omit an explicit type signature (which
70 /// // would be `HashMap<String, String>` in this example).
71 /// let mut book_reviews = HashMap::new();
73 /// // Review some books.
74 /// book_reviews.insert(
75 /// "Adventures of Huckleberry Finn".to_string(),
76 /// "My favorite book.".to_string(),
78 /// book_reviews.insert(
79 /// "Grimms' Fairy Tales".to_string(),
80 /// "Masterpiece.".to_string(),
82 /// book_reviews.insert(
83 /// "Pride and Prejudice".to_string(),
84 /// "Very enjoyable.".to_string(),
86 /// book_reviews.insert(
87 /// "The Adventures of Sherlock Holmes".to_string(),
88 /// "Eye lyked it alot.".to_string(),
91 /// // Check for a specific one.
92 /// // When collections store owned values (String), they can still be
93 /// // queried using references (&str).
94 /// if !book_reviews.contains_key("Les Misérables") {
95 /// println!("We've got {} reviews, but Les Misérables ain't one.",
96 /// book_reviews.len());
99 /// // oops, this review has a lot of spelling mistakes, let's delete it.
100 /// book_reviews.remove("The Adventures of Sherlock Holmes");
102 /// // Look up the values associated with some keys.
103 /// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
104 /// for &book in &to_find {
105 /// match book_reviews.get(book) {
106 /// Some(review) => println!("{}: {}", book, review),
107 /// None => println!("{} is unreviewed.", book)
111 /// // Look up the value for a key (will panic if the key is not found).
112 /// println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);
114 /// // Iterate over everything.
115 /// for (book, review) in &book_reviews {
116 /// println!("{}: \"{}\"", book, review);
120 /// `HashMap` also implements an [`Entry API`](#method.entry), which allows
121 /// for more complex methods of getting, setting, updating and removing keys and
125 /// use std::collections::HashMap;
127 /// // type inference lets us omit an explicit type signature (which
128 /// // would be `HashMap<&str, u8>` in this example).
129 /// let mut player_stats = HashMap::new();
131 /// fn random_stat_buff() -> u8 {
132 /// // could actually return some random value here - let's just return
133 /// // some fixed value for now
137 /// // insert a key only if it doesn't already exist
138 /// player_stats.entry("health").or_insert(100);
140 /// // insert a key using a function that provides a new value only if it
141 /// // doesn't already exist
142 /// player_stats.entry("defence").or_insert_with(random_stat_buff);
144 /// // update a key, guarding against the key possibly not being set
145 /// let stat = player_stats.entry("attack").or_insert(100);
146 /// *stat += random_stat_buff();
149 /// The easiest way to use `HashMap` with a custom key type is to derive [`Eq`] and [`Hash`].
150 /// We must also derive [`PartialEq`].
152 /// [`RefCell`]: crate::cell::RefCell
153 /// [`Cell`]: crate::cell::Cell
154 /// [`default`]: Default::default
155 /// [`with_hasher`]: Self::with_hasher
156 /// [`with_capacity_and_hasher`]: Self::with_capacity_and_hasher
157 /// [`fnv`]: https://crates.io/crates/fnv
160 /// use std::collections::HashMap;
162 /// #[derive(Hash, Eq, PartialEq, Debug)]
169 /// /// Creates a new Viking.
170 /// fn new(name: &str, country: &str) -> Viking {
171 /// Viking { name: name.to_string(), country: country.to_string() }
175 /// // Use a HashMap to store the vikings' health points.
176 /// let mut vikings = HashMap::new();
178 /// vikings.insert(Viking::new("Einar", "Norway"), 25);
179 /// vikings.insert(Viking::new("Olaf", "Denmark"), 24);
180 /// vikings.insert(Viking::new("Harald", "Iceland"), 12);
182 /// // Use derived implementation to print the status of the vikings.
183 /// for (viking, health) in &vikings {
184 /// println!("{:?} has {} hp", viking, health);
188 /// A `HashMap` with fixed list of elements can be initialized from an array:
191 /// use std::collections::HashMap;
193 /// let timber_resources: HashMap<&str, i32> = [("Norway", 100), ("Denmark", 50), ("Iceland", 10)]
194 /// .iter().cloned().collect();
195 /// // use the values stored in map
199 #[cfg_attr(not(test), rustc_diagnostic_item = "hashmap_type")]
200 #[stable(feature = "rust1", since = "1.0.0")]
201 pub struct HashMap<K, V, S = RandomState> {
202 base: base::HashMap<K, V, S>,
205 impl<K, V> HashMap<K, V, RandomState> {
206 /// Creates an empty `HashMap`.
208 /// The hash map is initially created with a capacity of 0, so it will not allocate until it
209 /// is first inserted into.
214 /// use std::collections::HashMap;
215 /// let mut map: HashMap<&str, i32> = HashMap::new();
218 #[stable(feature = "rust1", since = "1.0.0")]
219 pub fn new() -> HashMap<K, V, RandomState> {
223 /// Creates an empty `HashMap` with the specified capacity.
225 /// The hash map will be able to hold at least `capacity` elements without
226 /// reallocating. If `capacity` is 0, the hash map will not allocate.
231 /// use std::collections::HashMap;
232 /// let mut map: HashMap<&str, i32> = HashMap::with_capacity(10);
235 #[stable(feature = "rust1", since = "1.0.0")]
236 pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState> {
237 HashMap::with_capacity_and_hasher(capacity, Default::default())
241 impl<K, V, S> HashMap<K, V, S> {
242 /// Creates an empty `HashMap` which will use the given hash builder to hash
245 /// The created map has the default initial capacity.
247 /// Warning: `hash_builder` is normally randomly generated, and
248 /// is designed to allow HashMaps to be resistant to attacks that
249 /// cause many collisions and very poor performance. Setting it
250 /// manually using this function can expose a DoS attack vector.
252 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
253 /// the HashMap to be useful, see its documentation for details.
258 /// use std::collections::HashMap;
259 /// use std::collections::hash_map::RandomState;
261 /// let s = RandomState::new();
262 /// let mut map = HashMap::with_hasher(s);
263 /// map.insert(1, 2);
266 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
267 pub fn with_hasher(hash_builder: S) -> HashMap<K, V, S> {
268 HashMap { base: base::HashMap::with_hasher(hash_builder) }
271 /// Creates an empty `HashMap` with the specified capacity, using `hash_builder`
272 /// to hash the keys.
274 /// The hash map will be able to hold at least `capacity` elements without
275 /// reallocating. If `capacity` is 0, the hash map will not allocate.
277 /// Warning: `hash_builder` is normally randomly generated, and
278 /// is designed to allow HashMaps to be resistant to attacks that
279 /// cause many collisions and very poor performance. Setting it
280 /// manually using this function can expose a DoS attack vector.
282 /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
283 /// the HashMap to be useful, see its documentation for details.
288 /// use std::collections::HashMap;
289 /// use std::collections::hash_map::RandomState;
291 /// let s = RandomState::new();
292 /// let mut map = HashMap::with_capacity_and_hasher(10, s);
293 /// map.insert(1, 2);
296 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
297 pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> HashMap<K, V, S> {
298 HashMap { base: base::HashMap::with_capacity_and_hasher(capacity, hash_builder) }
301 /// Returns the number of elements the map can hold without reallocating.
303 /// This number is a lower bound; the `HashMap<K, V>` might be able to hold
304 /// more, but is guaranteed to be able to hold at least this many.
309 /// use std::collections::HashMap;
310 /// let map: HashMap<i32, i32> = HashMap::with_capacity(100);
311 /// assert!(map.capacity() >= 100);
314 #[stable(feature = "rust1", since = "1.0.0")]
315 pub fn capacity(&self) -> usize {
319 /// An iterator visiting all keys in arbitrary order.
320 /// The iterator element type is `&'a K`.
325 /// use std::collections::HashMap;
327 /// let mut map = HashMap::new();
328 /// map.insert("a", 1);
329 /// map.insert("b", 2);
330 /// map.insert("c", 3);
332 /// for key in map.keys() {
333 /// println!("{}", key);
336 #[stable(feature = "rust1", since = "1.0.0")]
337 pub fn keys(&self) -> Keys<'_, K, V> {
338 Keys { inner: self.iter() }
341 /// An iterator visiting all values in arbitrary order.
342 /// The iterator element type is `&'a V`.
347 /// use std::collections::HashMap;
349 /// let mut map = HashMap::new();
350 /// map.insert("a", 1);
351 /// map.insert("b", 2);
352 /// map.insert("c", 3);
354 /// for val in map.values() {
355 /// println!("{}", val);
358 #[stable(feature = "rust1", since = "1.0.0")]
359 pub fn values(&self) -> Values<'_, K, V> {
360 Values { inner: self.iter() }
363 /// An iterator visiting all values mutably in arbitrary order.
364 /// The iterator element type is `&'a mut V`.
369 /// use std::collections::HashMap;
371 /// let mut map = HashMap::new();
373 /// map.insert("a", 1);
374 /// map.insert("b", 2);
375 /// map.insert("c", 3);
377 /// for val in map.values_mut() {
378 /// *val = *val + 10;
381 /// for val in map.values() {
382 /// println!("{}", val);
385 #[stable(feature = "map_values_mut", since = "1.10.0")]
386 pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
387 ValuesMut { inner: self.iter_mut() }
390 /// An iterator visiting all key-value pairs in arbitrary order.
391 /// The iterator element type is `(&'a K, &'a V)`.
396 /// use std::collections::HashMap;
398 /// let mut map = HashMap::new();
399 /// map.insert("a", 1);
400 /// map.insert("b", 2);
401 /// map.insert("c", 3);
403 /// for (key, val) in map.iter() {
404 /// println!("key: {} val: {}", key, val);
407 #[stable(feature = "rust1", since = "1.0.0")]
408 pub fn iter(&self) -> Iter<'_, K, V> {
409 Iter { base: self.base.iter() }
412 /// An iterator visiting all key-value pairs in arbitrary order,
413 /// with mutable references to the values.
414 /// The iterator element type is `(&'a K, &'a mut V)`.
419 /// use std::collections::HashMap;
421 /// let mut map = HashMap::new();
422 /// map.insert("a", 1);
423 /// map.insert("b", 2);
424 /// map.insert("c", 3);
426 /// // Update all values
427 /// for (_, val) in map.iter_mut() {
431 /// for (key, val) in &map {
432 /// println!("key: {} val: {}", key, val);
435 #[stable(feature = "rust1", since = "1.0.0")]
436 pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
437 IterMut { base: self.base.iter_mut() }
440 /// Returns the number of elements in the map.
445 /// use std::collections::HashMap;
447 /// let mut a = HashMap::new();
448 /// assert_eq!(a.len(), 0);
449 /// a.insert(1, "a");
450 /// assert_eq!(a.len(), 1);
452 #[stable(feature = "rust1", since = "1.0.0")]
453 pub fn len(&self) -> usize {
457 /// Returns `true` if the map contains no elements.
462 /// use std::collections::HashMap;
464 /// let mut a = HashMap::new();
465 /// assert!(a.is_empty());
466 /// a.insert(1, "a");
467 /// assert!(!a.is_empty());
470 #[stable(feature = "rust1", since = "1.0.0")]
471 pub fn is_empty(&self) -> bool {
475 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
476 /// allocated memory for reuse.
481 /// use std::collections::HashMap;
483 /// let mut a = HashMap::new();
484 /// a.insert(1, "a");
485 /// a.insert(2, "b");
487 /// for (k, v) in a.drain().take(1) {
488 /// assert!(k == 1 || k == 2);
489 /// assert!(v == "a" || v == "b");
492 /// assert!(a.is_empty());
495 #[stable(feature = "drain", since = "1.6.0")]
496 pub fn drain(&mut self) -> Drain<'_, K, V> {
497 Drain { base: self.base.drain() }
500 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
506 /// use std::collections::HashMap;
508 /// let mut a = HashMap::new();
509 /// a.insert(1, "a");
511 /// assert!(a.is_empty());
513 #[stable(feature = "rust1", since = "1.0.0")]
515 pub fn clear(&mut self) {
519 /// Returns a reference to the map's [`BuildHasher`].
524 /// use std::collections::HashMap;
525 /// use std::collections::hash_map::RandomState;
527 /// let hasher = RandomState::new();
528 /// let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
529 /// let hasher: &RandomState = map.hasher();
532 #[stable(feature = "hashmap_public_hasher", since = "1.9.0")]
533 pub fn hasher(&self) -> &S {
538 impl<K, V, S> HashMap<K, V, S>
543 /// Reserves capacity for at least `additional` more elements to be inserted
544 /// in the `HashMap`. The collection may reserve more space to avoid
545 /// frequent reallocations.
549 /// Panics if the new allocation size overflows [`usize`].
554 /// use std::collections::HashMap;
555 /// let mut map: HashMap<&str, i32> = HashMap::new();
559 #[stable(feature = "rust1", since = "1.0.0")]
560 pub fn reserve(&mut self, additional: usize) {
561 self.base.reserve(additional)
564 /// Tries to reserve capacity for at least `additional` more elements to be inserted
565 /// in the given `HashMap<K,V>`. The collection may reserve more space to avoid
566 /// frequent reallocations.
570 /// If the capacity overflows, or the allocator reports a failure, then an error
576 /// #![feature(try_reserve)]
577 /// use std::collections::HashMap;
578 /// let mut map: HashMap<&str, isize> = HashMap::new();
579 /// map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");
582 #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")]
583 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
584 self.base.try_reserve(additional).map_err(map_try_reserve_error)
587 /// Shrinks the capacity of the map as much as possible. It will drop
588 /// down as much as possible while maintaining the internal rules
589 /// and possibly leaving some space in accordance with the resize policy.
594 /// use std::collections::HashMap;
596 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
597 /// map.insert(1, 2);
598 /// map.insert(3, 4);
599 /// assert!(map.capacity() >= 100);
600 /// map.shrink_to_fit();
601 /// assert!(map.capacity() >= 2);
604 #[stable(feature = "rust1", since = "1.0.0")]
605 pub fn shrink_to_fit(&mut self) {
606 self.base.shrink_to_fit();
609 /// Shrinks the capacity of the map with a lower limit. It will drop
610 /// down no lower than the supplied limit while maintaining the internal rules
611 /// and possibly leaving some space in accordance with the resize policy.
613 /// Panics if the current capacity is smaller than the supplied
614 /// minimum capacity.
619 /// #![feature(shrink_to)]
620 /// use std::collections::HashMap;
622 /// let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
623 /// map.insert(1, 2);
624 /// map.insert(3, 4);
625 /// assert!(map.capacity() >= 100);
626 /// map.shrink_to(10);
627 /// assert!(map.capacity() >= 10);
628 /// map.shrink_to(0);
629 /// assert!(map.capacity() >= 2);
632 #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")]
633 pub fn shrink_to(&mut self, min_capacity: usize) {
634 assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity");
635 self.base.shrink_to(min_capacity);
638 /// Gets the given key's corresponding entry in the map for in-place manipulation.
643 /// use std::collections::HashMap;
645 /// let mut letters = HashMap::new();
647 /// for ch in "a short treatise on fungi".chars() {
648 /// let counter = letters.entry(ch).or_insert(0);
652 /// assert_eq!(letters[&'s'], 2);
653 /// assert_eq!(letters[&'t'], 3);
654 /// assert_eq!(letters[&'u'], 1);
655 /// assert_eq!(letters.get(&'y'), None);
658 #[stable(feature = "rust1", since = "1.0.0")]
659 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
660 map_entry(self.base.rustc_entry(key))
663 /// Returns a reference to the value corresponding to the key.
665 /// The key may be any borrowed form of the map's key type, but
666 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
672 /// use std::collections::HashMap;
674 /// let mut map = HashMap::new();
675 /// map.insert(1, "a");
676 /// assert_eq!(map.get(&1), Some(&"a"));
677 /// assert_eq!(map.get(&2), None);
679 #[stable(feature = "rust1", since = "1.0.0")]
681 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
689 /// Returns the key-value pair corresponding to the supplied key.
691 /// The supplied key may be any borrowed form of the map's key type, but
692 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
698 /// use std::collections::HashMap;
700 /// let mut map = HashMap::new();
701 /// map.insert(1, "a");
702 /// assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
703 /// assert_eq!(map.get_key_value(&2), None);
705 #[stable(feature = "map_get_key_value", since = "1.40.0")]
707 pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
712 self.base.get_key_value(k)
715 /// Returns `true` if the map contains a value for the specified key.
717 /// The key may be any borrowed form of the map's key type, but
718 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
724 /// use std::collections::HashMap;
726 /// let mut map = HashMap::new();
727 /// map.insert(1, "a");
728 /// assert_eq!(map.contains_key(&1), true);
729 /// assert_eq!(map.contains_key(&2), false);
731 #[stable(feature = "rust1", since = "1.0.0")]
733 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
738 self.base.contains_key(k)
741 /// Returns a mutable reference to the value corresponding to the key.
743 /// The key may be any borrowed form of the map's key type, but
744 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
750 /// use std::collections::HashMap;
752 /// let mut map = HashMap::new();
753 /// map.insert(1, "a");
754 /// if let Some(x) = map.get_mut(&1) {
757 /// assert_eq!(map[&1], "b");
759 #[stable(feature = "rust1", since = "1.0.0")]
761 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
769 /// Inserts a key-value pair into the map.
771 /// If the map did not have this key present, [`None`] is returned.
773 /// If the map did have this key present, the value is updated, and the old
774 /// value is returned. The key is not updated, though; this matters for
775 /// types that can be `==` without being identical. See the [module-level
776 /// documentation] for more.
778 /// [module-level documentation]: crate::collections#insert-and-complex-keys
783 /// use std::collections::HashMap;
785 /// let mut map = HashMap::new();
786 /// assert_eq!(map.insert(37, "a"), None);
787 /// assert_eq!(map.is_empty(), false);
789 /// map.insert(37, "b");
790 /// assert_eq!(map.insert(37, "c"), Some("b"));
791 /// assert_eq!(map[&37], "c");
793 #[stable(feature = "rust1", since = "1.0.0")]
795 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
796 self.base.insert(k, v)
799 /// Removes a key from the map, returning the value at the key if the key
800 /// was previously in the map.
802 /// The key may be any borrowed form of the map's key type, but
803 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
809 /// use std::collections::HashMap;
811 /// let mut map = HashMap::new();
812 /// map.insert(1, "a");
813 /// assert_eq!(map.remove(&1), Some("a"));
814 /// assert_eq!(map.remove(&1), None);
816 #[stable(feature = "rust1", since = "1.0.0")]
818 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
826 /// Removes a key from the map, returning the stored key and value if the
827 /// key was previously in the map.
829 /// The key may be any borrowed form of the map's key type, but
830 /// [`Hash`] and [`Eq`] on the borrowed form *must* match those for
836 /// use std::collections::HashMap;
839 /// let mut map = HashMap::new();
840 /// map.insert(1, "a");
841 /// assert_eq!(map.remove_entry(&1), Some((1, "a")));
842 /// assert_eq!(map.remove(&1), None);
845 #[stable(feature = "hash_map_remove_entry", since = "1.27.0")]
847 pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)>
852 self.base.remove_entry(k)
855 /// Retains only the elements specified by the predicate.
857 /// In other words, remove all pairs `(k, v)` such that `f(&k,&mut v)` returns `false`.
862 /// use std::collections::HashMap;
864 /// let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
865 /// map.retain(|&k, _| k % 2 == 0);
866 /// assert_eq!(map.len(), 4);
868 #[stable(feature = "retain_hash_collection", since = "1.18.0")]
870 pub fn retain<F>(&mut self, f: F)
872 F: FnMut(&K, &mut V) -> bool,
877 /// Creates a consuming iterator visiting all the keys in arbitrary order.
878 /// The map cannot be used after calling this.
879 /// The iterator element type is `K`.
884 /// #![feature(map_into_keys_values)]
885 /// use std::collections::HashMap;
887 /// let mut map = HashMap::new();
888 /// map.insert("a", 1);
889 /// map.insert("b", 2);
890 /// map.insert("c", 3);
892 /// let vec: Vec<&str> = map.into_keys().collect();
895 #[unstable(feature = "map_into_keys_values", issue = "75294")]
896 pub fn into_keys(self) -> IntoKeys<K, V> {
897 IntoKeys { inner: self.into_iter() }
900 /// Creates a consuming iterator visiting all the values in arbitrary order.
901 /// The map cannot be used after calling this.
902 /// The iterator element type is `V`.
907 /// #![feature(map_into_keys_values)]
908 /// use std::collections::HashMap;
910 /// let mut map = HashMap::new();
911 /// map.insert("a", 1);
912 /// map.insert("b", 2);
913 /// map.insert("c", 3);
915 /// let vec: Vec<i32> = map.into_values().collect();
918 #[unstable(feature = "map_into_keys_values", issue = "75294")]
919 pub fn into_values(self) -> IntoValues<K, V> {
920 IntoValues { inner: self.into_iter() }
924 impl<K, V, S> HashMap<K, V, S>
928 /// Creates a raw entry builder for the HashMap.
930 /// Raw entries provide the lowest level of control for searching and
931 /// manipulating a map. They must be manually initialized with a hash and
932 /// then manually searched. After this, insertions into a vacant entry
933 /// still require an owned key to be provided.
935 /// Raw entries are useful for such exotic situations as:
937 /// * Hash memoization
938 /// * Deferring the creation of an owned key until it is known to be required
939 /// * Using a search key that doesn't work with the Borrow trait
940 /// * Using custom comparison logic without newtype wrappers
942 /// Because raw entries provide much more low-level control, it's much easier
943 /// to put the HashMap into an inconsistent state which, while memory-safe,
944 /// will cause the map to produce seemingly random results. Higher-level and
945 /// more foolproof APIs like `entry` should be preferred when possible.
947 /// In particular, the hash used to initialized the raw entry must still be
948 /// consistent with the hash of the key that is ultimately stored in the entry.
949 /// This is because implementations of HashMap may need to recompute hashes
950 /// when resizing, at which point only the keys are available.
952 /// Raw entries give mutable access to the keys. This must not be used
953 /// to modify how the key would compare or hash, as the map will not re-evaluate
954 /// where the key should go, meaning the keys may become "lost" if their
955 /// location does not reflect their state. For instance, if you change a key
956 /// so that the map now contains keys which compare equal, search may start
957 /// acting erratically, with two keys randomly masking each other. Implementations
958 /// are free to assume this doesn't happen (within the limits of memory-safety).
960 #[unstable(feature = "hash_raw_entry", issue = "56167")]
961 pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S> {
962 RawEntryBuilderMut { map: self }
965 /// Creates a raw immutable entry builder for the HashMap.
967 /// Raw entries provide the lowest level of control for searching and
968 /// manipulating a map. They must be manually initialized with a hash and
969 /// then manually searched.
971 /// This is useful for
972 /// * Hash memoization
973 /// * Using a search key that doesn't work with the Borrow trait
974 /// * Using custom comparison logic without newtype wrappers
976 /// Unless you are in such a situation, higher-level and more foolproof APIs like
977 /// `get` should be preferred.
979 /// Immutable raw entries have very limited use; you might instead want `raw_entry_mut`.
981 #[unstable(feature = "hash_raw_entry", issue = "56167")]
982 pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S> {
983 RawEntryBuilder { map: self }
987 #[stable(feature = "rust1", since = "1.0.0")]
988 impl<K, V, S> PartialEq for HashMap<K, V, S>
994 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
995 if self.len() != other.len() {
999 self.iter().all(|(key, value)| other.get(key).map_or(false, |v| *value == *v))
1003 #[stable(feature = "rust1", since = "1.0.0")]
1004 impl<K, V, S> Eq for HashMap<K, V, S>
1012 #[stable(feature = "rust1", since = "1.0.0")]
1013 impl<K, V, S> Debug for HashMap<K, V, S>
1018 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1019 f.debug_map().entries(self.iter()).finish()
1023 #[stable(feature = "rust1", since = "1.0.0")]
1024 impl<K, V, S> Default for HashMap<K, V, S>
1028 /// Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.
1030 fn default() -> HashMap<K, V, S> {
1031 HashMap::with_hasher(Default::default())
1035 #[stable(feature = "rust1", since = "1.0.0")]
1036 impl<K, Q: ?Sized, V, S> Index<&Q> for HashMap<K, V, S>
1038 K: Eq + Hash + Borrow<Q>,
1044 /// Returns a reference to the value corresponding to the supplied key.
1048 /// Panics if the key is not present in the `HashMap`.
1050 fn index(&self, key: &Q) -> &V {
1051 self.get(key).expect("no entry found for key")
1055 /// An iterator over the entries of a `HashMap`.
1057 /// This `struct` is created by the [`iter`] method on [`HashMap`]. See its
1058 /// documentation for more.
1060 /// [`iter`]: HashMap::iter
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 pub struct Iter<'a, K: 'a, V: 'a> {
1063 base: base::Iter<'a, K, V>,
1066 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1067 #[stable(feature = "rust1", since = "1.0.0")]
1068 impl<K, V> Clone for Iter<'_, K, V> {
1070 fn clone(&self) -> Self {
1071 Iter { base: self.base.clone() }
1075 #[stable(feature = "std_debug", since = "1.16.0")]
1076 impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
1077 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1078 f.debug_list().entries(self.clone()).finish()
1082 /// A mutable iterator over the entries of a `HashMap`.
1084 /// This `struct` is created by the [`iter_mut`] method on [`HashMap`]. See its
1085 /// documentation for more.
1087 /// [`iter_mut`]: HashMap::iter_mut
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 pub struct IterMut<'a, K: 'a, V: 'a> {
1090 base: base::IterMut<'a, K, V>,
1093 impl<'a, K, V> IterMut<'a, K, V> {
1094 /// Returns a iterator of references over the remaining items.
1096 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1097 Iter { base: self.base.rustc_iter() }
1101 /// An owning iterator over the entries of a `HashMap`.
1103 /// This `struct` is created by the [`into_iter`] method on [`HashMap`]
1104 /// (provided by the `IntoIterator` trait). See its documentation for more.
1106 /// [`into_iter`]: IntoIterator::into_iter
1107 #[stable(feature = "rust1", since = "1.0.0")]
1108 pub struct IntoIter<K, V> {
1109 base: base::IntoIter<K, V>,
1112 impl<K, V> IntoIter<K, V> {
1113 /// Returns a iterator of references over the remaining items.
1115 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1116 Iter { base: self.base.rustc_iter() }
1120 /// An iterator over the keys of a `HashMap`.
1122 /// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
1123 /// documentation for more.
1125 /// [`keys`]: HashMap::keys
1126 #[stable(feature = "rust1", since = "1.0.0")]
1127 pub struct Keys<'a, K: 'a, V: 'a> {
1128 inner: Iter<'a, K, V>,
1131 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1132 #[stable(feature = "rust1", since = "1.0.0")]
1133 impl<K, V> Clone for Keys<'_, K, V> {
1135 fn clone(&self) -> Self {
1136 Keys { inner: self.inner.clone() }
1140 #[stable(feature = "std_debug", since = "1.16.0")]
1141 impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
1142 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1143 f.debug_list().entries(self.clone()).finish()
1147 /// An iterator over the values of a `HashMap`.
1149 /// This `struct` is created by the [`values`] method on [`HashMap`]. See its
1150 /// documentation for more.
1152 /// [`values`]: HashMap::values
1153 #[stable(feature = "rust1", since = "1.0.0")]
1154 pub struct Values<'a, K: 'a, V: 'a> {
1155 inner: Iter<'a, K, V>,
1158 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1159 #[stable(feature = "rust1", since = "1.0.0")]
1160 impl<K, V> Clone for Values<'_, K, V> {
1162 fn clone(&self) -> Self {
1163 Values { inner: self.inner.clone() }
1167 #[stable(feature = "std_debug", since = "1.16.0")]
1168 impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
1169 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1170 f.debug_list().entries(self.clone()).finish()
1174 /// A draining iterator over the entries of a `HashMap`.
1176 /// This `struct` is created by the [`drain`] method on [`HashMap`]. See its
1177 /// documentation for more.
1179 /// [`drain`]: HashMap::drain
1180 #[stable(feature = "drain", since = "1.6.0")]
1181 pub struct Drain<'a, K: 'a, V: 'a> {
1182 base: base::Drain<'a, K, V>,
1185 impl<'a, K, V> Drain<'a, K, V> {
1186 /// Returns a iterator of references over the remaining items.
1188 pub(super) fn iter(&self) -> Iter<'_, K, V> {
1189 Iter { base: self.base.rustc_iter() }
1193 /// A mutable iterator over the values of a `HashMap`.
1195 /// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
1196 /// documentation for more.
1198 /// [`values_mut`]: HashMap::values_mut
1199 #[stable(feature = "map_values_mut", since = "1.10.0")]
1200 pub struct ValuesMut<'a, K: 'a, V: 'a> {
1201 inner: IterMut<'a, K, V>,
1204 /// An owning iterator over the keys of a `HashMap`.
1206 /// This `struct` is created by the [`into_keys`] method on [`HashMap`].
1207 /// See its documentation for more.
1209 /// [`into_keys`]: HashMap::into_keys
1210 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1211 pub struct IntoKeys<K, V> {
1212 inner: IntoIter<K, V>,
1215 /// An owning iterator over the values of a `HashMap`.
1217 /// This `struct` is created by the [`into_values`] method on [`HashMap`].
1218 /// See its documentation for more.
1220 /// [`into_values`]: HashMap::into_values
1221 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1222 pub struct IntoValues<K, V> {
1223 inner: IntoIter<K, V>,
1226 /// A builder for computing where in a HashMap a key-value pair would be stored.
1228 /// See the [`HashMap::raw_entry_mut`] docs for usage examples.
1230 /// [`HashMap::raw_entry_mut`]: HashMap::raw_entry_mut
1232 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1233 pub struct RawEntryBuilderMut<'a, K: 'a, V: 'a, S: 'a> {
1234 map: &'a mut HashMap<K, V, S>,
1237 /// A view into a single entry in a map, which may either be vacant or occupied.
1239 /// This is a lower-level version of [`Entry`].
1241 /// This `enum` is constructed through the [`raw_entry_mut`] method on [`HashMap`],
1242 /// then calling one of the methods of that [`RawEntryBuilderMut`].
1244 /// [`Entry`]: enum.Entry.html
1245 /// [`raw_entry_mut`]: HashMap::raw_entry_mut
1246 /// [`RawEntryBuilderMut`]: struct.RawEntryBuilderMut.html
1247 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1248 pub enum RawEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1249 /// An occupied entry.
1250 Occupied(RawOccupiedEntryMut<'a, K, V>),
1252 Vacant(RawVacantEntryMut<'a, K, V, S>),
1255 /// A view into an occupied entry in a `HashMap`.
1256 /// It is part of the [`RawEntryMut`] enum.
1257 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1258 pub struct RawOccupiedEntryMut<'a, K: 'a, V: 'a> {
1259 base: base::RawOccupiedEntryMut<'a, K, V>,
1262 /// A view into a vacant entry in a `HashMap`.
1263 /// It is part of the [`RawEntryMut`] enum.
1264 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1265 pub struct RawVacantEntryMut<'a, K: 'a, V: 'a, S: 'a> {
1266 base: base::RawVacantEntryMut<'a, K, V, S>,
1269 /// A builder for computing where in a HashMap a key-value pair would be stored.
1271 /// See the [`HashMap::raw_entry`] docs for usage examples.
1273 /// [`HashMap::raw_entry`]: HashMap::raw_entry
1274 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1275 pub struct RawEntryBuilder<'a, K: 'a, V: 'a, S: 'a> {
1276 map: &'a HashMap<K, V, S>,
1279 impl<'a, K, V, S> RawEntryBuilderMut<'a, K, V, S>
1283 /// Creates a `RawEntryMut` from the given key.
1285 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1286 pub fn from_key<Q: ?Sized>(self, k: &Q) -> RawEntryMut<'a, K, V, S>
1291 map_raw_entry(self.map.base.raw_entry_mut().from_key(k))
1294 /// Creates a `RawEntryMut` from the given key and its hash.
1296 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1297 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> RawEntryMut<'a, K, V, S>
1302 map_raw_entry(self.map.base.raw_entry_mut().from_key_hashed_nocheck(hash, k))
1305 /// Creates a `RawEntryMut` from the given hash.
1307 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1308 pub fn from_hash<F>(self, hash: u64, is_match: F) -> RawEntryMut<'a, K, V, S>
1310 for<'b> F: FnMut(&'b K) -> bool,
1312 map_raw_entry(self.map.base.raw_entry_mut().from_hash(hash, is_match))
1316 impl<'a, K, V, S> RawEntryBuilder<'a, K, V, S>
1320 /// Access an entry by key.
1322 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1323 pub fn from_key<Q: ?Sized>(self, k: &Q) -> Option<(&'a K, &'a V)>
1328 self.map.base.raw_entry().from_key(k)
1331 /// Access an entry by a key and its hash.
1333 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1334 pub fn from_key_hashed_nocheck<Q: ?Sized>(self, hash: u64, k: &Q) -> Option<(&'a K, &'a V)>
1339 self.map.base.raw_entry().from_key_hashed_nocheck(hash, k)
1342 /// Access an entry by hash.
1344 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1345 pub fn from_hash<F>(self, hash: u64, is_match: F) -> Option<(&'a K, &'a V)>
1347 F: FnMut(&K) -> bool,
1349 self.map.base.raw_entry().from_hash(hash, is_match)
1353 impl<'a, K, V, S> RawEntryMut<'a, K, V, S> {
1354 /// Ensures a value is in the entry by inserting the default if empty, and returns
1355 /// mutable references to the key and value in the entry.
1360 /// #![feature(hash_raw_entry)]
1361 /// use std::collections::HashMap;
1363 /// let mut map: HashMap<&str, u32> = HashMap::new();
1365 /// map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 3);
1366 /// assert_eq!(map["poneyland"], 3);
1368 /// *map.raw_entry_mut().from_key("poneyland").or_insert("poneyland", 10).1 *= 2;
1369 /// assert_eq!(map["poneyland"], 6);
1372 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1373 pub fn or_insert(self, default_key: K, default_val: V) -> (&'a mut K, &'a mut V)
1379 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1380 RawEntryMut::Vacant(entry) => entry.insert(default_key, default_val),
1384 /// Ensures a value is in the entry by inserting the result of the default function if empty,
1385 /// and returns mutable references to the key and value in the entry.
1390 /// #![feature(hash_raw_entry)]
1391 /// use std::collections::HashMap;
1393 /// let mut map: HashMap<&str, String> = HashMap::new();
1395 /// map.raw_entry_mut().from_key("poneyland").or_insert_with(|| {
1396 /// ("poneyland", "hoho".to_string())
1399 /// assert_eq!(map["poneyland"], "hoho".to_string());
1402 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1403 pub fn or_insert_with<F>(self, default: F) -> (&'a mut K, &'a mut V)
1405 F: FnOnce() -> (K, V),
1410 RawEntryMut::Occupied(entry) => entry.into_key_value(),
1411 RawEntryMut::Vacant(entry) => {
1412 let (k, v) = default();
1418 /// Provides in-place mutable access to an occupied entry before any
1419 /// potential inserts into the map.
1424 /// #![feature(hash_raw_entry)]
1425 /// use std::collections::HashMap;
1427 /// let mut map: HashMap<&str, u32> = HashMap::new();
1429 /// map.raw_entry_mut()
1430 /// .from_key("poneyland")
1431 /// .and_modify(|_k, v| { *v += 1 })
1432 /// .or_insert("poneyland", 42);
1433 /// assert_eq!(map["poneyland"], 42);
1435 /// map.raw_entry_mut()
1436 /// .from_key("poneyland")
1437 /// .and_modify(|_k, v| { *v += 1 })
1438 /// .or_insert("poneyland", 0);
1439 /// assert_eq!(map["poneyland"], 43);
1442 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1443 pub fn and_modify<F>(self, f: F) -> Self
1445 F: FnOnce(&mut K, &mut V),
1448 RawEntryMut::Occupied(mut entry) => {
1450 let (k, v) = entry.get_key_value_mut();
1453 RawEntryMut::Occupied(entry)
1455 RawEntryMut::Vacant(entry) => RawEntryMut::Vacant(entry),
1460 impl<'a, K, V> RawOccupiedEntryMut<'a, K, V> {
1461 /// Gets a reference to the key in the entry.
1463 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1464 pub fn key(&self) -> &K {
1468 /// Gets a mutable reference to the key in the entry.
1470 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1471 pub fn key_mut(&mut self) -> &mut K {
1475 /// Converts the entry into a mutable reference to the key in the entry
1476 /// with a lifetime bound to the map itself.
1478 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1479 pub fn into_key(self) -> &'a mut K {
1480 self.base.into_key()
1483 /// Gets a reference to the value in the entry.
1485 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1486 pub fn get(&self) -> &V {
1490 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
1491 /// with a lifetime bound to the map itself.
1493 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1494 pub fn into_mut(self) -> &'a mut V {
1495 self.base.into_mut()
1498 /// Gets a mutable reference to the value in the entry.
1500 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1501 pub fn get_mut(&mut self) -> &mut V {
1505 /// Gets a reference to the key and value in the entry.
1507 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1508 pub fn get_key_value(&mut self) -> (&K, &V) {
1509 self.base.get_key_value()
1512 /// Gets a mutable reference to the key and value in the entry.
1514 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1515 pub fn get_key_value_mut(&mut self) -> (&mut K, &mut V) {
1516 self.base.get_key_value_mut()
1519 /// Converts the OccupiedEntry into a mutable reference to the key and value in the entry
1520 /// with a lifetime bound to the map itself.
1522 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1523 pub fn into_key_value(self) -> (&'a mut K, &'a mut V) {
1524 self.base.into_key_value()
1527 /// Sets the value of the entry, and returns the entry's old value.
1529 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1530 pub fn insert(&mut self, value: V) -> V {
1531 self.base.insert(value)
1534 /// Sets the value of the entry, and returns the entry's old value.
1536 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1537 pub fn insert_key(&mut self, key: K) -> K {
1538 self.base.insert_key(key)
1541 /// Takes the value out of the entry, and returns it.
1543 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1544 pub fn remove(self) -> V {
1548 /// Take the ownership of the key and value from the map.
1550 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1551 pub fn remove_entry(self) -> (K, V) {
1552 self.base.remove_entry()
1556 impl<'a, K, V, S> RawVacantEntryMut<'a, K, V, S> {
1557 /// Sets the value of the entry with the VacantEntry's key,
1558 /// and returns a mutable reference to it.
1560 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1561 pub fn insert(self, key: K, value: V) -> (&'a mut K, &'a mut V)
1566 self.base.insert(key, value)
1569 /// Sets the value of the entry with the VacantEntry's key,
1570 /// and returns a mutable reference to it.
1572 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1573 pub fn insert_hashed_nocheck(self, hash: u64, key: K, value: V) -> (&'a mut K, &'a mut V)
1578 self.base.insert_hashed_nocheck(hash, key, value)
1582 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1583 impl<K, V, S> Debug for RawEntryBuilderMut<'_, K, V, S> {
1584 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1585 f.debug_struct("RawEntryBuilder").finish()
1589 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1590 impl<K: Debug, V: Debug, S> Debug for RawEntryMut<'_, K, V, S> {
1591 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1593 RawEntryMut::Vacant(ref v) => f.debug_tuple("RawEntry").field(v).finish(),
1594 RawEntryMut::Occupied(ref o) => f.debug_tuple("RawEntry").field(o).finish(),
1599 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1600 impl<K: Debug, V: Debug> Debug for RawOccupiedEntryMut<'_, K, V> {
1601 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1602 f.debug_struct("RawOccupiedEntryMut")
1603 .field("key", self.key())
1604 .field("value", self.get())
1609 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1610 impl<K, V, S> Debug for RawVacantEntryMut<'_, K, V, S> {
1611 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1612 f.debug_struct("RawVacantEntryMut").finish()
1616 #[unstable(feature = "hash_raw_entry", issue = "56167")]
1617 impl<K, V, S> Debug for RawEntryBuilder<'_, K, V, S> {
1618 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1619 f.debug_struct("RawEntryBuilder").finish()
1623 /// A view into a single entry in a map, which may either be vacant or occupied.
1625 /// This `enum` is constructed from the [`entry`] method on [`HashMap`].
1627 /// [`entry`]: HashMap::entry
1628 #[stable(feature = "rust1", since = "1.0.0")]
1629 pub enum Entry<'a, K: 'a, V: 'a> {
1630 /// An occupied entry.
1631 #[stable(feature = "rust1", since = "1.0.0")]
1632 Occupied(#[stable(feature = "rust1", since = "1.0.0")] OccupiedEntry<'a, K, V>),
1635 #[stable(feature = "rust1", since = "1.0.0")]
1636 Vacant(#[stable(feature = "rust1", since = "1.0.0")] VacantEntry<'a, K, V>),
1639 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1640 impl<K: Debug, V: Debug> Debug for Entry<'_, K, V> {
1641 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1643 Vacant(ref v) => f.debug_tuple("Entry").field(v).finish(),
1644 Occupied(ref o) => f.debug_tuple("Entry").field(o).finish(),
1649 /// A view into an occupied entry in a `HashMap`.
1650 /// It is part of the [`Entry`] enum.
1652 /// [`Entry`]: enum.Entry.html
1653 #[stable(feature = "rust1", since = "1.0.0")]
1654 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1655 base: base::RustcOccupiedEntry<'a, K, V>,
1658 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1659 impl<K: Debug, V: Debug> Debug for OccupiedEntry<'_, K, V> {
1660 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1661 f.debug_struct("OccupiedEntry").field("key", self.key()).field("value", self.get()).finish()
1665 /// A view into a vacant entry in a `HashMap`.
1666 /// It is part of the [`Entry`] enum.
1668 /// [`Entry`]: enum.Entry.html
1669 #[stable(feature = "rust1", since = "1.0.0")]
1670 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1671 base: base::RustcVacantEntry<'a, K, V>,
1674 #[stable(feature = "debug_hash_map", since = "1.12.0")]
1675 impl<K: Debug, V> Debug for VacantEntry<'_, K, V> {
1676 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1677 f.debug_tuple("VacantEntry").field(self.key()).finish()
1681 #[stable(feature = "rust1", since = "1.0.0")]
1682 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S> {
1683 type Item = (&'a K, &'a V);
1684 type IntoIter = Iter<'a, K, V>;
1687 fn into_iter(self) -> Iter<'a, K, V> {
1692 #[stable(feature = "rust1", since = "1.0.0")]
1693 impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S> {
1694 type Item = (&'a K, &'a mut V);
1695 type IntoIter = IterMut<'a, K, V>;
1698 fn into_iter(self) -> IterMut<'a, K, V> {
1703 #[stable(feature = "rust1", since = "1.0.0")]
1704 impl<K, V, S> IntoIterator for HashMap<K, V, S> {
1706 type IntoIter = IntoIter<K, V>;
1708 /// Creates a consuming iterator, that is, one that moves each key-value
1709 /// pair out of the map in arbitrary order. The map cannot be used after
1715 /// use std::collections::HashMap;
1717 /// let mut map = HashMap::new();
1718 /// map.insert("a", 1);
1719 /// map.insert("b", 2);
1720 /// map.insert("c", 3);
1722 /// // Not possible with .iter()
1723 /// let vec: Vec<(&str, i32)> = map.into_iter().collect();
1726 fn into_iter(self) -> IntoIter<K, V> {
1727 IntoIter { base: self.base.into_iter() }
1731 #[stable(feature = "rust1", since = "1.0.0")]
1732 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1733 type Item = (&'a K, &'a V);
1736 fn next(&mut self) -> Option<(&'a K, &'a V)> {
1740 fn size_hint(&self) -> (usize, Option<usize>) {
1741 self.base.size_hint()
1744 #[stable(feature = "rust1", since = "1.0.0")]
1745 impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
1747 fn len(&self) -> usize {
1752 #[stable(feature = "fused", since = "1.26.0")]
1753 impl<K, V> FusedIterator for Iter<'_, K, V> {}
1755 #[stable(feature = "rust1", since = "1.0.0")]
1756 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1757 type Item = (&'a K, &'a mut V);
1760 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
1764 fn size_hint(&self) -> (usize, Option<usize>) {
1765 self.base.size_hint()
1768 #[stable(feature = "rust1", since = "1.0.0")]
1769 impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
1771 fn len(&self) -> usize {
1775 #[stable(feature = "fused", since = "1.26.0")]
1776 impl<K, V> FusedIterator for IterMut<'_, K, V> {}
1778 #[stable(feature = "std_debug", since = "1.16.0")]
1779 impl<K, V> fmt::Debug for IterMut<'_, K, V>
1784 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1785 f.debug_list().entries(self.iter()).finish()
1789 #[stable(feature = "rust1", since = "1.0.0")]
1790 impl<K, V> Iterator for IntoIter<K, V> {
1794 fn next(&mut self) -> Option<(K, V)> {
1798 fn size_hint(&self) -> (usize, Option<usize>) {
1799 self.base.size_hint()
1802 #[stable(feature = "rust1", since = "1.0.0")]
1803 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1805 fn len(&self) -> usize {
1809 #[stable(feature = "fused", since = "1.26.0")]
1810 impl<K, V> FusedIterator for IntoIter<K, V> {}
1812 #[stable(feature = "std_debug", since = "1.16.0")]
1813 impl<K: Debug, V: Debug> fmt::Debug for IntoIter<K, V> {
1814 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1815 f.debug_list().entries(self.iter()).finish()
1819 #[stable(feature = "rust1", since = "1.0.0")]
1820 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1824 fn next(&mut self) -> Option<&'a K> {
1825 self.inner.next().map(|(k, _)| k)
1828 fn size_hint(&self) -> (usize, Option<usize>) {
1829 self.inner.size_hint()
1832 #[stable(feature = "rust1", since = "1.0.0")]
1833 impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
1835 fn len(&self) -> usize {
1839 #[stable(feature = "fused", since = "1.26.0")]
1840 impl<K, V> FusedIterator for Keys<'_, K, V> {}
1842 #[stable(feature = "rust1", since = "1.0.0")]
1843 impl<'a, K, V> Iterator for Values<'a, K, V> {
1847 fn next(&mut self) -> Option<&'a V> {
1848 self.inner.next().map(|(_, v)| v)
1851 fn size_hint(&self) -> (usize, Option<usize>) {
1852 self.inner.size_hint()
1855 #[stable(feature = "rust1", since = "1.0.0")]
1856 impl<K, V> ExactSizeIterator for Values<'_, K, V> {
1858 fn len(&self) -> usize {
1862 #[stable(feature = "fused", since = "1.26.0")]
1863 impl<K, V> FusedIterator for Values<'_, K, V> {}
1865 #[stable(feature = "map_values_mut", since = "1.10.0")]
1866 impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
1867 type Item = &'a mut V;
1870 fn next(&mut self) -> Option<&'a mut V> {
1871 self.inner.next().map(|(_, v)| v)
1874 fn size_hint(&self) -> (usize, Option<usize>) {
1875 self.inner.size_hint()
1878 #[stable(feature = "map_values_mut", since = "1.10.0")]
1879 impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
1881 fn len(&self) -> usize {
1885 #[stable(feature = "fused", since = "1.26.0")]
1886 impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
1888 #[stable(feature = "std_debug", since = "1.16.0")]
1889 impl<K, V> fmt::Debug for ValuesMut<'_, K, V>
1894 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1895 f.debug_list().entries(self.inner.iter()).finish()
1899 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1900 impl<K, V> Iterator for IntoKeys<K, V> {
1904 fn next(&mut self) -> Option<K> {
1905 self.inner.next().map(|(k, _)| k)
1908 fn size_hint(&self) -> (usize, Option<usize>) {
1909 self.inner.size_hint()
1912 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1913 impl<K, V> ExactSizeIterator for IntoKeys<K, V> {
1915 fn len(&self) -> usize {
1919 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1920 impl<K, V> FusedIterator for IntoKeys<K, V> {}
1922 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1923 impl<K: Debug, V: Debug> fmt::Debug for IntoKeys<K, V> {
1924 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1925 f.debug_list().entries(self.inner.iter().map(|(k, _)| k)).finish()
1929 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1930 impl<K, V> Iterator for IntoValues<K, V> {
1934 fn next(&mut self) -> Option<V> {
1935 self.inner.next().map(|(_, v)| v)
1938 fn size_hint(&self) -> (usize, Option<usize>) {
1939 self.inner.size_hint()
1942 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1943 impl<K, V> ExactSizeIterator for IntoValues<K, V> {
1945 fn len(&self) -> usize {
1949 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1950 impl<K, V> FusedIterator for IntoValues<K, V> {}
1952 #[unstable(feature = "map_into_keys_values", issue = "75294")]
1953 impl<K: Debug, V: Debug> fmt::Debug for IntoValues<K, V> {
1954 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1955 f.debug_list().entries(self.inner.iter().map(|(_, v)| v)).finish()
1959 #[stable(feature = "drain", since = "1.6.0")]
1960 impl<'a, K, V> Iterator for Drain<'a, K, V> {
1964 fn next(&mut self) -> Option<(K, V)> {
1968 fn size_hint(&self) -> (usize, Option<usize>) {
1969 self.base.size_hint()
1972 #[stable(feature = "drain", since = "1.6.0")]
1973 impl<K, V> ExactSizeIterator for Drain<'_, K, V> {
1975 fn len(&self) -> usize {
1979 #[stable(feature = "fused", since = "1.26.0")]
1980 impl<K, V> FusedIterator for Drain<'_, K, V> {}
1982 #[stable(feature = "std_debug", since = "1.16.0")]
1983 impl<K, V> fmt::Debug for Drain<'_, K, V>
1988 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1989 f.debug_list().entries(self.iter()).finish()
1993 impl<'a, K, V> Entry<'a, K, V> {
1994 #[stable(feature = "rust1", since = "1.0.0")]
1995 /// Ensures a value is in the entry by inserting the default if empty, and returns
1996 /// a mutable reference to the value in the entry.
2001 /// use std::collections::HashMap;
2003 /// let mut map: HashMap<&str, u32> = HashMap::new();
2005 /// map.entry("poneyland").or_insert(3);
2006 /// assert_eq!(map["poneyland"], 3);
2008 /// *map.entry("poneyland").or_insert(10) *= 2;
2009 /// assert_eq!(map["poneyland"], 6);
2012 pub fn or_insert(self, default: V) -> &'a mut V {
2014 Occupied(entry) => entry.into_mut(),
2015 Vacant(entry) => entry.insert(default),
2019 #[stable(feature = "rust1", since = "1.0.0")]
2020 /// Ensures a value is in the entry by inserting the result of the default function if empty,
2021 /// and returns a mutable reference to the value in the entry.
2026 /// use std::collections::HashMap;
2028 /// let mut map: HashMap<&str, String> = HashMap::new();
2029 /// let s = "hoho".to_string();
2031 /// map.entry("poneyland").or_insert_with(|| s);
2033 /// assert_eq!(map["poneyland"], "hoho".to_string());
2036 pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
2038 Occupied(entry) => entry.into_mut(),
2039 Vacant(entry) => entry.insert(default()),
2043 #[unstable(feature = "or_insert_with_key", issue = "71024")]
2044 /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
2045 /// which takes the key as its argument, and returns a mutable reference to the value in the
2051 /// #![feature(or_insert_with_key)]
2052 /// use std::collections::HashMap;
2054 /// let mut map: HashMap<&str, usize> = HashMap::new();
2056 /// map.entry("poneyland").or_insert_with_key(|key| key.chars().count());
2058 /// assert_eq!(map["poneyland"], 9);
2061 pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V {
2063 Occupied(entry) => entry.into_mut(),
2065 let value = default(entry.key());
2071 /// Returns a reference to this entry's key.
2076 /// use std::collections::HashMap;
2078 /// let mut map: HashMap<&str, u32> = HashMap::new();
2079 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2082 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2083 pub fn key(&self) -> &K {
2085 Occupied(ref entry) => entry.key(),
2086 Vacant(ref entry) => entry.key(),
2090 /// Provides in-place mutable access to an occupied entry before any
2091 /// potential inserts into the map.
2096 /// use std::collections::HashMap;
2098 /// let mut map: HashMap<&str, u32> = HashMap::new();
2100 /// map.entry("poneyland")
2101 /// .and_modify(|e| { *e += 1 })
2103 /// assert_eq!(map["poneyland"], 42);
2105 /// map.entry("poneyland")
2106 /// .and_modify(|e| { *e += 1 })
2108 /// assert_eq!(map["poneyland"], 43);
2111 #[stable(feature = "entry_and_modify", since = "1.26.0")]
2112 pub fn and_modify<F>(self, f: F) -> Self
2117 Occupied(mut entry) => {
2121 Vacant(entry) => Vacant(entry),
2125 /// Sets the value of the entry, and returns an OccupiedEntry.
2130 /// #![feature(entry_insert)]
2131 /// use std::collections::HashMap;
2133 /// let mut map: HashMap<&str, String> = HashMap::new();
2134 /// let entry = map.entry("poneyland").insert("hoho".to_string());
2136 /// assert_eq!(entry.key(), &"poneyland");
2139 #[unstable(feature = "entry_insert", issue = "65225")]
2140 pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V> {
2142 Occupied(mut entry) => {
2143 entry.insert(value);
2146 Vacant(entry) => entry.insert_entry(value),
2151 impl<'a, K, V: Default> Entry<'a, K, V> {
2152 #[stable(feature = "entry_or_default", since = "1.28.0")]
2153 /// Ensures a value is in the entry by inserting the default value if empty,
2154 /// and returns a mutable reference to the value in the entry.
2160 /// use std::collections::HashMap;
2162 /// let mut map: HashMap<&str, Option<u32>> = HashMap::new();
2163 /// map.entry("poneyland").or_default();
2165 /// assert_eq!(map["poneyland"], None);
2169 pub fn or_default(self) -> &'a mut V {
2171 Occupied(entry) => entry.into_mut(),
2172 Vacant(entry) => entry.insert(Default::default()),
2177 impl<'a, K, V> OccupiedEntry<'a, K, V> {
2178 /// Gets a reference to the key in the entry.
2183 /// use std::collections::HashMap;
2185 /// let mut map: HashMap<&str, u32> = HashMap::new();
2186 /// map.entry("poneyland").or_insert(12);
2187 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2190 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2191 pub fn key(&self) -> &K {
2195 /// Take the ownership of the key and value from the map.
2200 /// use std::collections::HashMap;
2201 /// use std::collections::hash_map::Entry;
2203 /// let mut map: HashMap<&str, u32> = HashMap::new();
2204 /// map.entry("poneyland").or_insert(12);
2206 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2207 /// // We delete the entry from the map.
2208 /// o.remove_entry();
2211 /// assert_eq!(map.contains_key("poneyland"), false);
2214 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2215 pub fn remove_entry(self) -> (K, V) {
2216 self.base.remove_entry()
2219 /// Gets a reference to the value in the entry.
2224 /// use std::collections::HashMap;
2225 /// use std::collections::hash_map::Entry;
2227 /// let mut map: HashMap<&str, u32> = HashMap::new();
2228 /// map.entry("poneyland").or_insert(12);
2230 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2231 /// assert_eq!(o.get(), &12);
2235 #[stable(feature = "rust1", since = "1.0.0")]
2236 pub fn get(&self) -> &V {
2240 /// Gets a mutable reference to the value in the entry.
2242 /// If you need a reference to the `OccupiedEntry` which may outlive the
2243 /// destruction of the `Entry` value, see [`into_mut`].
2245 /// [`into_mut`]: Self::into_mut
2250 /// use std::collections::HashMap;
2251 /// use std::collections::hash_map::Entry;
2253 /// let mut map: HashMap<&str, u32> = HashMap::new();
2254 /// map.entry("poneyland").or_insert(12);
2256 /// assert_eq!(map["poneyland"], 12);
2257 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2258 /// *o.get_mut() += 10;
2259 /// assert_eq!(*o.get(), 22);
2261 /// // We can use the same Entry multiple times.
2262 /// *o.get_mut() += 2;
2265 /// assert_eq!(map["poneyland"], 24);
2268 #[stable(feature = "rust1", since = "1.0.0")]
2269 pub fn get_mut(&mut self) -> &mut V {
2273 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
2274 /// with a lifetime bound to the map itself.
2276 /// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
2278 /// [`get_mut`]: Self::get_mut
2283 /// use std::collections::HashMap;
2284 /// use std::collections::hash_map::Entry;
2286 /// let mut map: HashMap<&str, u32> = HashMap::new();
2287 /// map.entry("poneyland").or_insert(12);
2289 /// assert_eq!(map["poneyland"], 12);
2290 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2291 /// *o.into_mut() += 10;
2294 /// assert_eq!(map["poneyland"], 22);
2297 #[stable(feature = "rust1", since = "1.0.0")]
2298 pub fn into_mut(self) -> &'a mut V {
2299 self.base.into_mut()
2302 /// Sets the value of the entry, and returns the entry's old value.
2307 /// use std::collections::HashMap;
2308 /// use std::collections::hash_map::Entry;
2310 /// let mut map: HashMap<&str, u32> = HashMap::new();
2311 /// map.entry("poneyland").or_insert(12);
2313 /// if let Entry::Occupied(mut o) = map.entry("poneyland") {
2314 /// assert_eq!(o.insert(15), 12);
2317 /// assert_eq!(map["poneyland"], 15);
2320 #[stable(feature = "rust1", since = "1.0.0")]
2321 pub fn insert(&mut self, value: V) -> V {
2322 self.base.insert(value)
2325 /// Takes the value out of the entry, and returns it.
2330 /// use std::collections::HashMap;
2331 /// use std::collections::hash_map::Entry;
2333 /// let mut map: HashMap<&str, u32> = HashMap::new();
2334 /// map.entry("poneyland").or_insert(12);
2336 /// if let Entry::Occupied(o) = map.entry("poneyland") {
2337 /// assert_eq!(o.remove(), 12);
2340 /// assert_eq!(map.contains_key("poneyland"), false);
2343 #[stable(feature = "rust1", since = "1.0.0")]
2344 pub fn remove(self) -> V {
2348 /// Replaces the entry, returning the old key and value. The new key in the hash map will be
2349 /// the key used to create this entry.
2354 /// #![feature(map_entry_replace)]
2355 /// use std::collections::hash_map::{Entry, HashMap};
2356 /// use std::rc::Rc;
2358 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2359 /// map.insert(Rc::new("Stringthing".to_string()), 15);
2361 /// let my_key = Rc::new("Stringthing".to_string());
2363 /// if let Entry::Occupied(entry) = map.entry(my_key) {
2364 /// // Also replace the key with a handle to our other key.
2365 /// let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
2370 #[unstable(feature = "map_entry_replace", issue = "44286")]
2371 pub fn replace_entry(self, value: V) -> (K, V) {
2372 self.base.replace_entry(value)
2375 /// Replaces the key in the hash map with the key used to create this entry.
2380 /// #![feature(map_entry_replace)]
2381 /// use std::collections::hash_map::{Entry, HashMap};
2382 /// use std::rc::Rc;
2384 /// let mut map: HashMap<Rc<String>, u32> = HashMap::new();
2385 /// let mut known_strings: Vec<Rc<String>> = Vec::new();
2387 /// // Initialise known strings, run program, etc.
2389 /// reclaim_memory(&mut map, &known_strings);
2391 /// fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
2392 /// for s in known_strings {
2393 /// if let Entry::Occupied(entry) = map.entry(s.clone()) {
2394 /// // Replaces the entry's key with our version of it in `known_strings`.
2395 /// entry.replace_key();
2401 #[unstable(feature = "map_entry_replace", issue = "44286")]
2402 pub fn replace_key(self) -> K {
2403 self.base.replace_key()
2407 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
2408 /// Gets a reference to the key that would be used when inserting a value
2409 /// through the `VacantEntry`.
2414 /// use std::collections::HashMap;
2416 /// let mut map: HashMap<&str, u32> = HashMap::new();
2417 /// assert_eq!(map.entry("poneyland").key(), &"poneyland");
2420 #[stable(feature = "map_entry_keys", since = "1.10.0")]
2421 pub fn key(&self) -> &K {
2425 /// Take ownership of the key.
2430 /// use std::collections::HashMap;
2431 /// use std::collections::hash_map::Entry;
2433 /// let mut map: HashMap<&str, u32> = HashMap::new();
2435 /// if let Entry::Vacant(v) = map.entry("poneyland") {
2440 #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
2441 pub fn into_key(self) -> K {
2442 self.base.into_key()
2445 /// Sets the value of the entry with the VacantEntry's key,
2446 /// and returns a mutable reference to it.
2451 /// use std::collections::HashMap;
2452 /// use std::collections::hash_map::Entry;
2454 /// let mut map: HashMap<&str, u32> = HashMap::new();
2456 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2459 /// assert_eq!(map["poneyland"], 37);
2462 #[stable(feature = "rust1", since = "1.0.0")]
2463 pub fn insert(self, value: V) -> &'a mut V {
2464 self.base.insert(value)
2467 /// Sets the value of the entry with the VacantEntry's key,
2468 /// and returns an OccupiedEntry.
2473 /// use std::collections::HashMap;
2474 /// use std::collections::hash_map::Entry;
2476 /// let mut map: HashMap<&str, u32> = HashMap::new();
2478 /// if let Entry::Vacant(o) = map.entry("poneyland") {
2481 /// assert_eq!(map["poneyland"], 37);
2484 fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> {
2485 let base = self.base.insert_entry(value);
2486 OccupiedEntry { base }
2490 #[stable(feature = "rust1", since = "1.0.0")]
2491 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
2494 S: BuildHasher + Default,
2496 fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> HashMap<K, V, S> {
2497 let mut map = HashMap::with_hasher(Default::default());
2503 /// Inserts all new key-values from the iterator and replaces values with existing
2504 /// keys with new values returned from the iterator.
2505 #[stable(feature = "rust1", since = "1.0.0")]
2506 impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>
2512 fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
2513 self.base.extend(iter)
2517 fn extend_one(&mut self, (k, v): (K, V)) {
2518 self.base.insert(k, v);
2522 fn extend_reserve(&mut self, additional: usize) {
2523 // self.base.extend_reserve(additional);
2524 // FIXME: hashbrown should implement this method.
2525 // But until then, use the same reservation logic:
2527 // Reserve the entire hint lower bound if the map is empty.
2528 // Otherwise reserve half the hint (rounded up), so the map
2529 // will only resize twice in the worst case.
2530 let reserve = if self.is_empty() { additional } else { (additional + 1) / 2 };
2531 self.base.reserve(reserve);
2535 #[stable(feature = "hash_extend_copy", since = "1.4.0")]
2536 impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>
2538 K: Eq + Hash + Copy,
2543 fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T) {
2544 self.base.extend(iter)
2548 fn extend_one(&mut self, (&k, &v): (&'a K, &'a V)) {
2549 self.base.insert(k, v);
2553 fn extend_reserve(&mut self, additional: usize) {
2554 Extend::<(K, V)>::extend_reserve(self, additional)
2558 /// `RandomState` is the default state for [`HashMap`] types.
2560 /// A particular instance `RandomState` will create the same instances of
2561 /// [`Hasher`], but the hashers created by two different `RandomState`
2562 /// instances are unlikely to produce the same result for the same values.
2567 /// use std::collections::HashMap;
2568 /// use std::collections::hash_map::RandomState;
2570 /// let s = RandomState::new();
2571 /// let mut map = HashMap::with_hasher(s);
2572 /// map.insert(1, 2);
2575 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2576 pub struct RandomState {
2582 /// Constructs a new `RandomState` that is initialized with random keys.
2587 /// use std::collections::hash_map::RandomState;
2589 /// let s = RandomState::new();
2592 #[allow(deprecated)]
2594 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2595 pub fn new() -> RandomState {
2596 // Historically this function did not cache keys from the OS and instead
2597 // simply always called `rand::thread_rng().gen()` twice. In #31356 it
2598 // was discovered, however, that because we re-seed the thread-local RNG
2599 // from the OS periodically that this can cause excessive slowdown when
2600 // many hash maps are created on a thread. To solve this performance
2601 // trap we cache the first set of randomly generated keys per-thread.
2603 // Later in #36481 it was discovered that exposing a deterministic
2604 // iteration order allows a form of DOS attack. To counter that we
2605 // increment one of the seeds on every RandomState creation, giving
2606 // every corresponding HashMap a different iteration order.
2607 thread_local!(static KEYS: Cell<(u64, u64)> = {
2608 Cell::new(sys::hashmap_random_keys())
2612 let (k0, k1) = keys.get();
2613 keys.set((k0.wrapping_add(1), k1));
2614 RandomState { k0, k1 }
2619 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2620 impl BuildHasher for RandomState {
2621 type Hasher = DefaultHasher;
2623 #[allow(deprecated)]
2624 fn build_hasher(&self) -> DefaultHasher {
2625 DefaultHasher(SipHasher13::new_with_keys(self.k0, self.k1))
2629 /// The default [`Hasher`] used by [`RandomState`].
2631 /// The internal algorithm is not specified, and so it and its hashes should
2632 /// not be relied upon over releases.
2633 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2634 #[allow(deprecated)]
2635 #[derive(Clone, Debug)]
2636 pub struct DefaultHasher(SipHasher13);
2638 impl DefaultHasher {
2639 /// Creates a new `DefaultHasher`.
2641 /// This hasher is not guaranteed to be the same as all other
2642 /// `DefaultHasher` instances, but is the same as all other `DefaultHasher`
2643 /// instances created through `new` or `default`.
2644 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2645 #[allow(deprecated)]
2646 pub fn new() -> DefaultHasher {
2647 DefaultHasher(SipHasher13::new_with_keys(0, 0))
2651 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2652 impl Default for DefaultHasher {
2653 // FIXME: here should link `new` to [DefaultHasher::new], but it occurs intra-doc link
2654 // resolution failure when re-exporting libstd items. When #56922 fixed,
2655 // link `new` to [DefaultHasher::new] again.
2656 /// Creates a new `DefaultHasher` using `new`.
2657 /// See its documentation for more.
2658 fn default() -> DefaultHasher {
2659 DefaultHasher::new()
2663 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
2664 impl Hasher for DefaultHasher {
2666 fn write(&mut self, msg: &[u8]) {
2671 fn finish(&self) -> u64 {
2676 #[stable(feature = "hashmap_build_hasher", since = "1.7.0")]
2677 impl Default for RandomState {
2678 /// Constructs a new `RandomState`.
2680 fn default() -> RandomState {
2685 #[stable(feature = "std_debug", since = "1.16.0")]
2686 impl fmt::Debug for RandomState {
2687 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2688 f.pad("RandomState { .. }")
2693 fn map_entry<'a, K: 'a, V: 'a>(raw: base::RustcEntry<'a, K, V>) -> Entry<'a, K, V> {
2695 base::RustcEntry::Occupied(base) => Entry::Occupied(OccupiedEntry { base }),
2696 base::RustcEntry::Vacant(base) => Entry::Vacant(VacantEntry { base }),
2701 fn map_try_reserve_error(err: hashbrown::TryReserveError) -> TryReserveError {
2703 hashbrown::TryReserveError::CapacityOverflow => TryReserveError::CapacityOverflow,
2704 hashbrown::TryReserveError::AllocError { layout } => {
2705 TryReserveError::AllocError { layout, non_exhaustive: () }
2711 fn map_raw_entry<'a, K: 'a, V: 'a, S: 'a>(
2712 raw: base::RawEntryMut<'a, K, V, S>,
2713 ) -> RawEntryMut<'a, K, V, S> {
2715 base::RawEntryMut::Occupied(base) => RawEntryMut::Occupied(RawOccupiedEntryMut { base }),
2716 base::RawEntryMut::Vacant(base) => RawEntryMut::Vacant(RawVacantEntryMut { base }),
2721 fn assert_covariance() {
2722 fn map_key<'new>(v: HashMap<&'static str, u8>) -> HashMap<&'new str, u8> {
2725 fn map_val<'new>(v: HashMap<u8, &'static str>) -> HashMap<u8, &'new str> {
2728 fn iter_key<'a, 'new>(v: Iter<'a, &'static str, u8>) -> Iter<'a, &'new str, u8> {
2731 fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
2734 fn into_iter_key<'new>(v: IntoIter<&'static str, u8>) -> IntoIter<&'new str, u8> {
2737 fn into_iter_val<'new>(v: IntoIter<u8, &'static str>) -> IntoIter<u8, &'new str> {
2740 fn keys_key<'a, 'new>(v: Keys<'a, &'static str, u8>) -> Keys<'a, &'new str, u8> {
2743 fn keys_val<'a, 'new>(v: Keys<'a, u8, &'static str>) -> Keys<'a, u8, &'new str> {
2746 fn values_key<'a, 'new>(v: Values<'a, &'static str, u8>) -> Values<'a, &'new str, u8> {
2749 fn values_val<'a, 'new>(v: Values<'a, u8, &'static str>) -> Values<'a, u8, &'new str> {
2753 d: Drain<'static, &'static str, &'static str>,
2754 ) -> Drain<'new, &'new str, &'new str> {