1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // ignore-lexer-test FIXME #15883
14 use self::SearchResult::*;
15 use self::VacantEntryState::*;
19 use cmp::{max, Eq, PartialEq};
21 use fmt::{self, Debug};
22 use hash::{Hash, SipHasher};
23 use iter::{self, Iterator, ExactSizeIterator, IntoIterator, IteratorExt, FromIterator, Extend, Map};
25 use mem::{self, replace};
26 use num::{Int, UnsignedInt};
27 use ops::{Deref, FnMut, Index, IndexMut};
28 use option::Option::{self, Some, None};
29 use rand::{self, Rng};
30 use result::Result::{self, Ok, Err};
42 use super::table::BucketState::{
46 use super::state::HashState;
48 const INITIAL_LOG2_CAP: usize = 5;
49 #[unstable(feature = "std_misc")]
50 pub const INITIAL_CAPACITY: usize = 1 << INITIAL_LOG2_CAP; // 2^5
52 /// The default behavior of HashMap implements a load factor of 90.9%.
53 /// This behavior is characterized by the following condition:
55 /// - if size > 0.909 * capacity: grow the map
57 struct DefaultResizePolicy;
59 impl DefaultResizePolicy {
60 fn new() -> DefaultResizePolicy {
65 fn min_capacity(&self, usable_size: usize) -> usize {
66 // Here, we are rephrasing the logic by specifying the lower limit
69 // - if `cap < size * 1.1`: grow the map
73 /// An inverse of `min_capacity`, approximately.
75 fn usable_capacity(&self, cap: usize) -> usize {
76 // As the number of entries approaches usable capacity,
77 // min_capacity(size) must be smaller than the internal capacity,
78 // so that the map is not resized:
79 // `min_capacity(usable_capacity(x)) <= x`.
80 // The left-hand side can only be smaller due to flooring by integer
83 // This doesn't have to be checked for overflow since allocation size
84 // in bytes will overflow earlier than multiplication by 10.
90 fn test_resize_policy() {
91 let rp = DefaultResizePolicy;
93 assert!(rp.min_capacity(rp.usable_capacity(n)) <= n);
94 assert!(rp.usable_capacity(rp.min_capacity(n)) <= n);
98 // The main performance trick in this hashmap is called Robin Hood Hashing.
99 // It gains its excellent performance from one essential operation:
101 // If an insertion collides with an existing element, and that element's
102 // "probe distance" (how far away the element is from its ideal location)
103 // is higher than how far we've already probed, swap the elements.
105 // This massively lowers variance in probe distance, and allows us to get very
106 // high load factors with good performance. The 90% load factor I use is rather
109 // > Why a load factor of approximately 90%?
111 // In general, all the distances to initial buckets will converge on the mean.
112 // At a load factor of α, the odds of finding the target bucket after k
113 // probes is approximately 1-α^k. If we set this equal to 50% (since we converge
114 // on the mean) and set k=8 (64-byte cache line / 8-byte hash), α=0.92. I round
115 // this down to make the math easier on the CPU and avoid its FPU.
116 // Since on average we start the probing in the middle of a cache line, this
117 // strategy pulls in two cache lines of hashes on every lookup. I think that's
118 // pretty good, but if you want to trade off some space, it could go down to one
119 // cache line on average with an α of 0.84.
121 // > Wait, what? Where did you get 1-α^k from?
123 // On the first probe, your odds of a collision with an existing element is α.
124 // The odds of doing this twice in a row is approximately α^2. For three times,
125 // α^3, etc. Therefore, the odds of colliding k times is α^k. The odds of NOT
126 // colliding after k tries is 1-α^k.
128 // The paper from 1986 cited below mentions an implementation which keeps track
129 // of the distance-to-initial-bucket histogram. This approach is not suitable
130 // for modern architectures because it requires maintaining an internal data
131 // structure. This allows very good first guesses, but we are most concerned
132 // with guessing entire cache lines, not individual indexes. Furthermore, array
133 // accesses are no longer linear and in one direction, as we have now. There
134 // is also memory and cache pressure that this would entail that would be very
135 // difficult to properly see in a microbenchmark.
137 // ## Future Improvements (FIXME!)
139 // Allow the load factor to be changed dynamically and/or at initialization.
141 // Also, would it be possible for us to reuse storage when growing the
142 // underlying table? This is exactly the use case for 'realloc', and may
143 // be worth exploring.
145 // ## Future Optimizations (FIXME!)
147 // Another possible design choice that I made without any real reason is
148 // parameterizing the raw table over keys and values. Technically, all we need
149 // is the size and alignment of keys and values, and the code should be just as
150 // efficient (well, we might need one for power-of-two size and one for not...).
151 // This has the potential to reduce code bloat in rust executables, without
152 // really losing anything except 4 words (key size, key alignment, val size,
153 // val alignment) which can be passed in to every call of a `RawTable` function.
154 // This would definitely be an avenue worth exploring if people start complaining
155 // about the size of rust executables.
157 // Annotate exceedingly likely branches in `table::make_hash`
158 // and `search_hashed` to reduce instruction cache pressure
159 // and mispredictions once it becomes possible (blocked on issue #11092).
161 // Shrinking the table could simply reallocate in place after moving buckets
162 // to the first half.
164 // The growth algorithm (fragment of the Proof of Correctness)
165 // --------------------
167 // The growth algorithm is basically a fast path of the naive reinsertion-
168 // during-resize algorithm. Other paths should never be taken.
170 // Consider growing a robin hood hashtable of capacity n. Normally, we do this
171 // by allocating a new table of capacity `2n`, and then individually reinsert
172 // each element in the old table into the new one. This guarantees that the
173 // new table is a valid robin hood hashtable with all the desired statistical
174 // properties. Remark that the order we reinsert the elements in should not
175 // matter. For simplicity and efficiency, we will consider only linear
176 // reinsertions, which consist of reinserting all elements in the old table
177 // into the new one by increasing order of index. However we will not be
178 // starting our reinsertions from index 0 in general. If we start from index
179 // i, for the purpose of reinsertion we will consider all elements with real
180 // index j < i to have virtual index n + j.
182 // Our hash generation scheme consists of generating a 64-bit hash and
183 // truncating the most significant bits. When moving to the new table, we
184 // simply introduce a new bit to the front of the hash. Therefore, if an
185 // elements has ideal index i in the old table, it can have one of two ideal
186 // locations in the new table. If the new bit is 0, then the new ideal index
187 // is i. If the new bit is 1, then the new ideal index is n + i. Intuitively,
188 // we are producing two independent tables of size n, and for each element we
189 // independently choose which table to insert it into with equal probability.
190 // However the rather than wrapping around themselves on overflowing their
191 // indexes, the first table overflows into the first, and the first into the
192 // second. Visually, our new table will look something like:
194 // [yy_xxx_xxxx_xxx|xx_yyy_yyyy_yyy]
196 // Where x's are elements inserted into the first table, y's are elements
197 // inserted into the second, and _'s are empty sections. We now define a few
198 // key concepts that we will use later. Note that this is a very abstract
199 // perspective of the table. A real resized table would be at least half
202 // Theorem: A linear robin hood reinsertion from the first ideal element
203 // produces identical results to a linear naive reinsertion from the same
206 // FIXME(Gankro, pczarn): review the proof and put it all in a separate README.md
208 /// A hash map implementation which uses linear probing with Robin
209 /// Hood bucket stealing.
211 /// The hashes are all keyed by the task-local random number generator
212 /// on creation by default. This means that the ordering of the keys is
213 /// randomized, but makes the tables more resistant to
214 /// denial-of-service attacks (Hash DoS). This behaviour can be
215 /// overridden with one of the constructors.
217 /// It is required that the keys implement the `Eq` and `Hash` traits, although
218 /// this can frequently be achieved by using `#[derive(Eq, Hash)]`.
220 /// Relevant papers/articles:
222 /// 1. Pedro Celis. ["Robin Hood Hashing"](https://cs.uwaterloo.ca/research/tr/1986/CS-86-14.pdf)
223 /// 2. Emmanuel Goossaert. ["Robin Hood
224 /// hashing"](http://codecapsule.com/2013/11/11/robin-hood-hashing/)
225 /// 3. Emmanuel Goossaert. ["Robin Hood hashing: backward shift
226 /// deletion"](http://codecapsule.com/2013/11/17/robin-hood-hashing-backward-shift-deletion/)
231 /// use std::collections::HashMap;
233 /// // type inference lets us omit an explicit type signature (which
234 /// // would be `HashMap<&str, &str>` in this example).
235 /// let mut book_reviews = HashMap::new();
237 /// // review some books.
238 /// book_reviews.insert("Adventures of Huckleberry Finn", "My favorite book.");
239 /// book_reviews.insert("Grimms' Fairy Tales", "Masterpiece.");
240 /// book_reviews.insert("Pride and Prejudice", "Very enjoyable.");
241 /// book_reviews.insert("The Adventures of Sherlock Holmes", "Eye lyked it alot.");
243 /// // check for a specific one.
244 /// if !book_reviews.contains_key(&("Les Misérables")) {
245 /// println!("We've got {} reviews, but Les Misérables ain't one.",
246 /// book_reviews.len());
249 /// // oops, this review has a lot of spelling mistakes, let's delete it.
250 /// book_reviews.remove(&("The Adventures of Sherlock Holmes"));
252 /// // look up the values associated with some keys.
253 /// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
254 /// for book in to_find.iter() {
255 /// match book_reviews.get(book) {
256 /// Some(review) => println!("{}: {}", *book, *review),
257 /// None => println!("{} is unreviewed.", *book)
261 /// // iterate over everything.
262 /// for (book, review) in book_reviews.iter() {
263 /// println!("{}: \"{}\"", *book, *review);
267 /// The easiest way to use `HashMap` with a custom type as key is to derive `Eq` and `Hash`.
268 /// We must also derive `PartialEq`.
271 /// use std::collections::HashMap;
273 /// #[derive(Hash, Eq, PartialEq, Debug)]
280 /// /// Create a new Viking.
281 /// fn new(name: &str, country: &str) -> Viking {
282 /// Viking { name: name.to_string(), country: country.to_string() }
286 /// // Use a HashMap to store the vikings' health points.
287 /// let mut vikings = HashMap::new();
289 /// vikings.insert(Viking::new("Einar", "Norway"), 25);
290 /// vikings.insert(Viking::new("Olaf", "Denmark"), 24);
291 /// vikings.insert(Viking::new("Harald", "Iceland"), 12);
293 /// // Use derived implementation to print the status of the vikings.
294 /// for (viking, health) in vikings.iter() {
295 /// println!("{:?} has {} hp", viking, health);
299 #[stable(feature = "rust1", since = "1.0.0")]
300 pub struct HashMap<K, V, S = RandomState> {
301 // All hashes are keyed on these values, to prevent hash collision attacks.
304 table: RawTable<K, V>,
306 resize_policy: DefaultResizePolicy,
309 /// Search for a pre-hashed key.
310 fn search_hashed<K, V, M, F>(table: M,
313 -> SearchResult<K, V, M> where
314 M: Deref<Target=RawTable<K, V>>,
315 F: FnMut(&K) -> bool,
317 let size = table.size();
318 let mut probe = Bucket::new(table, hash);
319 let ib = probe.index();
321 while probe.index() != ib + size {
322 let full = match probe.peek() {
323 Empty(b) => return TableRef(b.into_table()), // hit an empty bucket
327 if full.distance() + ib < full.index() {
328 // We can finish the search early if we hit any bucket
329 // with a lower distance to initial bucket than we've probed.
330 return TableRef(full.into_table());
333 // If the hash doesn't match, it can't be this one..
334 if hash == full.hash() {
335 // If the key doesn't match, it can't be this one..
336 if is_match(full.read().0) {
337 return FoundExisting(full);
344 TableRef(probe.into_table())
347 fn pop_internal<K, V>(starting_bucket: FullBucketMut<K, V>) -> (K, V) {
348 let (empty, retkey, retval) = starting_bucket.take();
349 let mut gap = match empty.gap_peek() {
351 None => return (retkey, retval)
354 while gap.full().distance() != 0 {
355 gap = match gap.shift() {
361 // Now we've done all our shifting. Return the value we grabbed earlier.
365 /// Perform robin hood bucket stealing at the given `bucket`. You must
366 /// also pass the position of that bucket's initial bucket so we don't have
367 /// to recalculate it.
369 /// `hash`, `k`, and `v` are the elements to "robin hood" into the hashtable.
370 fn robin_hood<'a, K: 'a, V: 'a>(mut bucket: FullBucketMut<'a, K, V>,
376 let starting_index = bucket.index();
378 let table = bucket.table(); // FIXME "lifetime too short".
381 // There can be at most `size - dib` buckets to displace, because
382 // in the worst case, there are `size` elements and we already are
383 // `distance` buckets away from the initial one.
384 let idx_end = starting_index + size - bucket.distance();
387 let (old_hash, old_key, old_val) = bucket.replace(hash, k, v);
389 let probe = bucket.next();
390 assert!(probe.index() != idx_end);
392 let full_bucket = match probe.peek() {
395 let b = bucket.put(old_hash, old_key, old_val);
396 // Now that it's stolen, just read the value's pointer
397 // right out of the table!
398 return Bucket::at_index(b.into_table(), starting_index)
404 Full(bucket) => bucket
407 let probe_ib = full_bucket.index() - full_bucket.distance();
409 bucket = full_bucket;
411 // Robin hood! Steal the spot.
423 /// A result that works like Option<FullBucket<..>> but preserves
424 /// the reference that grants us access to the table in any case.
425 enum SearchResult<K, V, M> {
426 // This is an entry that holds the given key:
427 FoundExisting(FullBucket<K, V, M>),
429 // There was no such entry. The reference is given back:
433 impl<K, V, M> SearchResult<K, V, M> {
434 fn into_option(self) -> Option<FullBucket<K, V, M>> {
436 FoundExisting(bucket) => Some(bucket),
442 impl<K, V, S> HashMap<K, V, S>
443 where K: Eq + Hash, S: HashState
445 fn make_hash<X: ?Sized>(&self, x: &X) -> SafeHash where X: Hash {
446 table::make_hash(&self.hash_state, x)
449 /// Search for a key, yielding the index if it's found in the hashtable.
450 /// If you already have the hash for the key lying around, use
452 fn search<'a, Q: ?Sized>(&'a self, q: &Q) -> Option<FullBucketImm<'a, K, V>>
453 where K: Borrow<Q>, Q: Eq + Hash
455 let hash = self.make_hash(q);
456 search_hashed(&self.table, hash, |k| q.eq(k.borrow()))
460 fn search_mut<'a, Q: ?Sized>(&'a mut self, q: &Q) -> Option<FullBucketMut<'a, K, V>>
461 where K: Borrow<Q>, Q: Eq + Hash
463 let hash = self.make_hash(q);
464 search_hashed(&mut self.table, hash, |k| q.eq(k.borrow()))
468 // The caller should ensure that invariants by Robin Hood Hashing hold.
469 fn insert_hashed_ordered(&mut self, hash: SafeHash, k: K, v: V) {
470 let cap = self.table.capacity();
471 let mut buckets = Bucket::new(&mut self.table, hash);
472 let ib = buckets.index();
474 while buckets.index() != ib + cap {
475 // We don't need to compare hashes for value swap.
476 // Not even DIBs for Robin Hood.
477 buckets = match buckets.peek() {
479 empty.put(hash, k, v);
482 Full(b) => b.into_bucket()
486 panic!("Internal HashMap error: Out of space.");
490 impl<K: Hash + Eq, V> HashMap<K, V, RandomState> {
491 /// Create an empty HashMap.
496 /// use std::collections::HashMap;
497 /// let mut map: HashMap<&str, int> = HashMap::new();
500 #[stable(feature = "rust1", since = "1.0.0")]
501 pub fn new() -> HashMap<K, V, RandomState> {
505 /// Creates an empty hash map with the given initial capacity.
510 /// use std::collections::HashMap;
511 /// let mut map: HashMap<&str, int> = HashMap::with_capacity(10);
514 #[stable(feature = "rust1", since = "1.0.0")]
515 pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState> {
516 HashMap::with_capacity_and_hash_state(capacity, Default::default())
520 impl<K, V, S> HashMap<K, V, S>
521 where K: Eq + Hash, S: HashState
523 /// Creates an empty hashmap which will use the given hasher to hash keys.
525 /// The creates map has the default initial capacity.
530 /// use std::collections::HashMap;
531 /// use std::collections::hash_map::RandomState;
533 /// let s = RandomState::new();
534 /// let mut map = HashMap::with_hash_state(s);
535 /// map.insert(1, 2);
538 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
539 pub fn with_hash_state(hash_state: S) -> HashMap<K, V, S> {
541 hash_state: hash_state,
542 resize_policy: DefaultResizePolicy::new(),
543 table: RawTable::new(0),
547 /// Create an empty HashMap with space for at least `capacity`
548 /// elements, using `hasher` to hash the keys.
550 /// Warning: `hasher` is normally randomly generated, and
551 /// is designed to allow HashMaps to be resistant to attacks that
552 /// cause many collisions and very poor performance. Setting it
553 /// manually using this function can expose a DoS attack vector.
558 /// use std::collections::HashMap;
559 /// use std::collections::hash_map::RandomState;
561 /// let s = RandomState::new();
562 /// let mut map = HashMap::with_capacity_and_hash_state(10, s);
563 /// map.insert(1, 2);
566 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
567 pub fn with_capacity_and_hash_state(capacity: usize, hash_state: S)
568 -> HashMap<K, V, S> {
569 let resize_policy = DefaultResizePolicy::new();
570 let min_cap = max(INITIAL_CAPACITY, resize_policy.min_capacity(capacity));
571 let internal_cap = min_cap.checked_next_power_of_two().expect("capacity overflow");
572 assert!(internal_cap >= capacity, "capacity overflow");
574 hash_state: hash_state,
575 resize_policy: resize_policy,
576 table: RawTable::new(internal_cap),
580 /// Returns the number of elements the map can hold without reallocating.
585 /// use std::collections::HashMap;
586 /// let map: HashMap<int, int> = HashMap::with_capacity(100);
587 /// assert!(map.capacity() >= 100);
590 #[stable(feature = "rust1", since = "1.0.0")]
591 pub fn capacity(&self) -> usize {
592 self.resize_policy.usable_capacity(self.table.capacity())
595 /// Reserves capacity for at least `additional` more elements to be inserted
596 /// in the `HashMap`. The collection may reserve more space to avoid
597 /// frequent reallocations.
601 /// Panics if the new allocation size overflows `usize`.
606 /// use std::collections::HashMap;
607 /// let mut map: HashMap<&str, int> = HashMap::new();
610 #[stable(feature = "rust1", since = "1.0.0")]
611 pub fn reserve(&mut self, additional: usize) {
612 let new_size = self.len().checked_add(additional).expect("capacity overflow");
613 let min_cap = self.resize_policy.min_capacity(new_size);
615 // An invalid value shouldn't make us run out of space. This includes
616 // an overflow check.
617 assert!(new_size <= min_cap);
619 if self.table.capacity() < min_cap {
620 let new_capacity = max(min_cap.next_power_of_two(), INITIAL_CAPACITY);
621 self.resize(new_capacity);
625 /// Resizes the internal vectors to a new capacity. It's your responsibility to:
626 /// 1) Make sure the new capacity is enough for all the elements, accounting
627 /// for the load factor.
628 /// 2) Ensure new_capacity is a power of two or zero.
629 fn resize(&mut self, new_capacity: usize) {
630 assert!(self.table.size() <= new_capacity);
631 assert!(new_capacity.is_power_of_two() || new_capacity == 0);
633 let mut old_table = replace(&mut self.table, RawTable::new(new_capacity));
634 let old_size = old_table.size();
636 if old_table.capacity() == 0 || old_table.size() == 0 {
641 // Specialization of the other branch.
642 let mut bucket = Bucket::first(&mut old_table);
644 // "So a few of the first shall be last: for many be called,
647 // We'll most likely encounter a few buckets at the beginning that
648 // have their initial buckets near the end of the table. They were
649 // placed at the beginning as the probe wrapped around the table
650 // during insertion. We must skip forward to a bucket that won't
651 // get reinserted too early and won't unfairly steal others spot.
652 // This eliminates the need for robin hood.
654 bucket = match bucket.peek() {
656 if full.distance() == 0 {
657 // This bucket occupies its ideal spot.
658 // It indicates the start of another "cluster".
659 bucket = full.into_bucket();
662 // Leaving this bucket in the last cluster for later.
666 // Encountered a hole between clusters.
673 // This is how the buckets might be laid out in memory:
674 // ($ marks an initialized bucket)
676 // |$$$_$$$$$$_$$$$$|
678 // But we've skipped the entire initial cluster of buckets
679 // and will continue iteration in this order:
682 // ^ wrap around once end is reached
685 // ^ exit once table.size == 0
687 bucket = match bucket.peek() {
689 let h = bucket.hash();
690 let (b, k, v) = bucket.take();
691 self.insert_hashed_ordered(h, k, v);
693 let t = b.table(); // FIXME "lifetime too short".
694 if t.size() == 0 { break }
698 Empty(b) => b.into_bucket()
703 assert_eq!(self.table.size(), old_size);
706 /// Shrinks the capacity of the map as much as possible. It will drop
707 /// down as much as possible while maintaining the internal rules
708 /// and possibly leaving some space in accordance with the resize policy.
713 /// use std::collections::HashMap;
715 /// let mut map: HashMap<int, int> = HashMap::with_capacity(100);
716 /// map.insert(1, 2);
717 /// map.insert(3, 4);
718 /// assert!(map.capacity() >= 100);
719 /// map.shrink_to_fit();
720 /// assert!(map.capacity() >= 2);
722 #[stable(feature = "rust1", since = "1.0.0")]
723 pub fn shrink_to_fit(&mut self) {
724 let min_capacity = self.resize_policy.min_capacity(self.len());
725 let min_capacity = max(min_capacity.next_power_of_two(), INITIAL_CAPACITY);
727 // An invalid value shouldn't make us run out of space.
728 debug_assert!(self.len() <= min_capacity);
730 if self.table.capacity() != min_capacity {
731 let old_table = replace(&mut self.table, RawTable::new(min_capacity));
732 let old_size = old_table.size();
734 // Shrink the table. Naive algorithm for resizing:
735 for (h, k, v) in old_table.into_iter() {
736 self.insert_hashed_nocheck(h, k, v);
739 debug_assert_eq!(self.table.size(), old_size);
743 /// Insert a pre-hashed key-value pair, without first checking
744 /// that there's enough room in the buckets. Returns a reference to the
745 /// newly insert value.
747 /// If the key already exists, the hashtable will be returned untouched
748 /// and a reference to the existing element will be returned.
749 fn insert_hashed_nocheck(&mut self, hash: SafeHash, k: K, v: V) -> &mut V {
750 self.insert_or_replace_with(hash, k, v, |_, _, _| ())
753 fn insert_or_replace_with<'a, F>(&'a mut self,
757 mut found_existing: F)
759 F: FnMut(&mut K, &mut V, V),
761 // Worst case, we'll find one empty bucket among `size + 1` buckets.
762 let size = self.table.size();
763 let mut probe = Bucket::new(&mut self.table, hash);
764 let ib = probe.index();
767 let mut bucket = match probe.peek() {
770 return bucket.put(hash, k, v).into_mut_refs().1;
772 Full(bucket) => bucket
776 if bucket.hash() == hash {
778 if k == *bucket.read_mut().0 {
779 let (bucket_k, bucket_v) = bucket.into_mut_refs();
780 debug_assert!(k == *bucket_k);
781 // Key already exists. Get its reference.
782 found_existing(bucket_k, bucket_v, v);
787 let robin_ib = bucket.index() as int - bucket.distance() as int;
789 if (ib as int) < robin_ib {
790 // Found a luckier bucket than me. Better steal his spot.
791 return robin_hood(bucket, robin_ib as usize, hash, k, v);
794 probe = bucket.next();
795 assert!(probe.index() != ib + size + 1);
799 /// An iterator visiting all keys in arbitrary order.
800 /// Iterator element type is `&'a K`.
805 /// use std::collections::HashMap;
807 /// let mut map = HashMap::new();
808 /// map.insert("a", 1);
809 /// map.insert("b", 2);
810 /// map.insert("c", 3);
812 /// for key in map.keys() {
813 /// println!("{}", key);
816 #[stable(feature = "rust1", since = "1.0.0")]
817 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
818 fn first<A, B>((a, _): (A, B)) -> A { a }
819 let first: fn((&'a K,&'a V)) -> &'a K = first; // coerce to fn ptr
821 Keys { inner: self.iter().map(first) }
824 /// An iterator visiting all values in arbitrary order.
825 /// Iterator element type is `&'a V`.
830 /// use std::collections::HashMap;
832 /// let mut map = HashMap::new();
833 /// map.insert("a", 1);
834 /// map.insert("b", 2);
835 /// map.insert("c", 3);
837 /// for val in map.values() {
838 /// println!("{}", val);
841 #[stable(feature = "rust1", since = "1.0.0")]
842 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
843 fn second<A, B>((_, b): (A, B)) -> B { b }
844 let second: fn((&'a K,&'a V)) -> &'a V = second; // coerce to fn ptr
846 Values { inner: self.iter().map(second) }
849 /// An iterator visiting all key-value pairs in arbitrary order.
850 /// Iterator element type is `(&'a K, &'a V)`.
855 /// use std::collections::HashMap;
857 /// let mut map = HashMap::new();
858 /// map.insert("a", 1);
859 /// map.insert("b", 2);
860 /// map.insert("c", 3);
862 /// for (key, val) in map.iter() {
863 /// println!("key: {} val: {}", key, val);
866 #[stable(feature = "rust1", since = "1.0.0")]
867 pub fn iter(&self) -> Iter<K, V> {
868 Iter { inner: self.table.iter() }
871 /// An iterator visiting all key-value pairs in arbitrary order,
872 /// with mutable references to the values.
873 /// Iterator element type is `(&'a K, &'a mut V)`.
878 /// use std::collections::HashMap;
880 /// let mut map = HashMap::new();
881 /// map.insert("a", 1);
882 /// map.insert("b", 2);
883 /// map.insert("c", 3);
885 /// // Update all values
886 /// for (_, val) in map.iter_mut() {
890 /// for (key, val) in map.iter() {
891 /// println!("key: {} val: {}", key, val);
894 #[stable(feature = "rust1", since = "1.0.0")]
895 pub fn iter_mut(&mut self) -> IterMut<K, V> {
896 IterMut { inner: self.table.iter_mut() }
899 /// Creates a consuming iterator, that is, one that moves each key-value
900 /// pair out of the map in arbitrary order. The map cannot be used after
906 /// use std::collections::HashMap;
908 /// let mut map = HashMap::new();
909 /// map.insert("a", 1);
910 /// map.insert("b", 2);
911 /// map.insert("c", 3);
913 /// // Not possible with .iter()
914 /// let vec: Vec<(&str, int)> = map.into_iter().collect();
916 #[stable(feature = "rust1", since = "1.0.0")]
917 pub fn into_iter(self) -> IntoIter<K, V> {
918 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
919 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two;
922 inner: self.table.into_iter().map(last_two)
926 /// Gets the given key's corresponding entry in the map for in-place manipulation.
927 #[stable(feature = "rust1", since = "1.0.0")]
928 pub fn entry(&mut self, key: K) -> Entry<K, V> {
932 let hash = self.make_hash(&key);
933 search_entry_hashed(&mut self.table, hash, key)
936 /// Returns the number of elements in the map.
941 /// use std::collections::HashMap;
943 /// let mut a = HashMap::new();
944 /// assert_eq!(a.len(), 0);
945 /// a.insert(1, "a");
946 /// assert_eq!(a.len(), 1);
948 #[stable(feature = "rust1", since = "1.0.0")]
949 pub fn len(&self) -> usize { self.table.size() }
951 /// Returns true if the map contains no elements.
956 /// use std::collections::HashMap;
958 /// let mut a = HashMap::new();
959 /// assert!(a.is_empty());
960 /// a.insert(1, "a");
961 /// assert!(!a.is_empty());
964 #[stable(feature = "rust1", since = "1.0.0")]
965 pub fn is_empty(&self) -> bool { self.len() == 0 }
967 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
968 /// allocated memory for reuse.
973 /// use std::collections::HashMap;
975 /// let mut a = HashMap::new();
976 /// a.insert(1, "a");
977 /// a.insert(2, "b");
979 /// for (k, v) in a.drain().take(1) {
980 /// assert!(k == 1 || k == 2);
981 /// assert!(v == "a" || v == "b");
984 /// assert!(a.is_empty());
987 #[unstable(feature = "std_misc",
988 reason = "matches collection reform specification, waiting for dust to settle")]
989 pub fn drain(&mut self) -> Drain<K, V> {
990 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
991 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two; // coerce to fn pointer
994 inner: self.table.drain().map(last_two),
998 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
1004 /// use std::collections::HashMap;
1006 /// let mut a = HashMap::new();
1007 /// a.insert(1, "a");
1009 /// assert!(a.is_empty());
1011 #[stable(feature = "rust1", since = "1.0.0")]
1013 pub fn clear(&mut self) {
1017 /// Returns a reference to the value corresponding to the key.
1019 /// The key may be any borrowed form of the map's key type, but
1020 /// `Hash` and `Eq` on the borrowed form *must* match those for
1026 /// use std::collections::HashMap;
1028 /// let mut map = HashMap::new();
1029 /// map.insert(1, "a");
1030 /// assert_eq!(map.get(&1), Some(&"a"));
1031 /// assert_eq!(map.get(&2), None);
1033 #[stable(feature = "rust1", since = "1.0.0")]
1034 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
1035 where K: Borrow<Q>, Q: Hash + Eq
1037 self.search(k).map(|bucket| bucket.into_refs().1)
1040 /// Returns true if the map contains a value for the specified key.
1042 /// The key may be any borrowed form of the map's key type, but
1043 /// `Hash` and `Eq` on the borrowed form *must* match those for
1049 /// use std::collections::HashMap;
1051 /// let mut map = HashMap::new();
1052 /// map.insert(1, "a");
1053 /// assert_eq!(map.contains_key(&1), true);
1054 /// assert_eq!(map.contains_key(&2), false);
1056 #[stable(feature = "rust1", since = "1.0.0")]
1057 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
1058 where K: Borrow<Q>, Q: Hash + Eq
1060 self.search(k).is_some()
1063 /// Returns a mutable reference to the value corresponding to the key.
1065 /// The key may be any borrowed form of the map's key type, but
1066 /// `Hash` and `Eq` on the borrowed form *must* match those for
1072 /// use std::collections::HashMap;
1074 /// let mut map = HashMap::new();
1075 /// map.insert(1, "a");
1076 /// match map.get_mut(&1) {
1077 /// Some(x) => *x = "b",
1080 /// assert_eq!(map[1], "b");
1082 #[stable(feature = "rust1", since = "1.0.0")]
1083 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
1084 where K: Borrow<Q>, Q: Hash + Eq
1086 self.search_mut(k).map(|bucket| bucket.into_mut_refs().1)
1089 /// Inserts a key-value pair from the map. If the key already had a value
1090 /// present in the map, that value is returned. Otherwise, `None` is returned.
1095 /// use std::collections::HashMap;
1097 /// let mut map = HashMap::new();
1098 /// assert_eq!(map.insert(37, "a"), None);
1099 /// assert_eq!(map.is_empty(), false);
1101 /// map.insert(37, "b");
1102 /// assert_eq!(map.insert(37, "c"), Some("b"));
1103 /// assert_eq!(map[37], "c");
1105 #[stable(feature = "rust1", since = "1.0.0")]
1106 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1107 let hash = self.make_hash(&k);
1110 let mut retval = None;
1111 self.insert_or_replace_with(hash, k, v, |_, val_ref, val| {
1112 retval = Some(replace(val_ref, val));
1117 /// Removes a key from the map, returning the value at the key if the key
1118 /// was previously in the map.
1120 /// The key may be any borrowed form of the map's key type, but
1121 /// `Hash` and `Eq` on the borrowed form *must* match those for
1127 /// use std::collections::HashMap;
1129 /// let mut map = HashMap::new();
1130 /// map.insert(1, "a");
1131 /// assert_eq!(map.remove(&1), Some("a"));
1132 /// assert_eq!(map.remove(&1), None);
1134 #[stable(feature = "rust1", since = "1.0.0")]
1135 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
1136 where K: Borrow<Q>, Q: Hash + Eq
1138 if self.table.size() == 0 {
1142 self.search_mut(k).map(|bucket| pop_internal(bucket).1)
1146 fn search_entry_hashed<'a, K: Eq, V>(table: &'a mut RawTable<K,V>, hash: SafeHash, k: K)
1149 // Worst case, we'll find one empty bucket among `size + 1` buckets.
1150 let size = table.size();
1151 let mut probe = Bucket::new(table, hash);
1152 let ib = probe.index();
1155 let bucket = match probe.peek() {
1158 return Vacant(VacantEntry {
1161 elem: NoElem(bucket),
1164 Full(bucket) => bucket
1168 if bucket.hash() == hash {
1170 if k == *bucket.read().0 {
1171 return Occupied(OccupiedEntry{
1177 let robin_ib = bucket.index() as int - bucket.distance() as int;
1179 if (ib as int) < robin_ib {
1180 // Found a luckier bucket than me. Better steal his spot.
1181 return Vacant(VacantEntry {
1184 elem: NeqElem(bucket, robin_ib as usize),
1188 probe = bucket.next();
1189 assert!(probe.index() != ib + size + 1);
1193 impl<K, V, S> PartialEq for HashMap<K, V, S>
1194 where K: Eq + Hash, V: PartialEq, S: HashState
1196 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1197 if self.len() != other.len() { return false; }
1199 self.iter().all(|(key, value)|
1200 other.get(key).map_or(false, |v| *value == *v)
1205 #[stable(feature = "rust1", since = "1.0.0")]
1206 impl<K, V, S> Eq for HashMap<K, V, S>
1207 where K: Eq + Hash, V: Eq, S: HashState
1210 #[stable(feature = "rust1", since = "1.0.0")]
1211 impl<K, V, S> Debug for HashMap<K, V, S>
1212 where K: Eq + Hash + Debug, V: Debug, S: HashState
1214 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1215 try!(write!(f, "{{"));
1217 for (i, (k, v)) in self.iter().enumerate() {
1218 if i != 0 { try!(write!(f, ", ")); }
1219 try!(write!(f, "{:?}: {:?}", *k, *v));
1226 #[stable(feature = "rust1", since = "1.0.0")]
1227 impl<K, V, S> Default for HashMap<K, V, S>
1229 S: HashState + Default,
1231 fn default() -> HashMap<K, V, S> {
1232 HashMap::with_hash_state(Default::default())
1236 #[stable(feature = "rust1", since = "1.0.0")]
1237 impl<K, Q: ?Sized, V, S> Index<Q> for HashMap<K, V, S>
1238 where K: Eq + Hash + Borrow<Q>,
1245 fn index<'a>(&'a self, index: &Q) -> &'a V {
1246 self.get(index).expect("no entry found for key")
1250 #[stable(feature = "rust1", since = "1.0.0")]
1251 impl<K, V, S, Q: ?Sized> IndexMut<Q> for HashMap<K, V, S>
1252 where K: Eq + Hash + Borrow<Q>,
1257 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1258 self.get_mut(index).expect("no entry found for key")
1262 /// HashMap iterator.
1263 #[stable(feature = "rust1", since = "1.0.0")]
1264 pub struct Iter<'a, K: 'a, V: 'a> {
1265 inner: table::Iter<'a, K, V>
1268 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1269 impl<'a, K, V> Clone for Iter<'a, K, V> {
1270 fn clone(&self) -> Iter<'a, K, V> {
1272 inner: self.inner.clone()
1277 /// HashMap mutable values iterator.
1278 #[stable(feature = "rust1", since = "1.0.0")]
1279 pub struct IterMut<'a, K: 'a, V: 'a> {
1280 inner: table::IterMut<'a, K, V>
1283 /// HashMap move iterator.
1284 #[stable(feature = "rust1", since = "1.0.0")]
1285 pub struct IntoIter<K, V> {
1286 inner: iter::Map<table::IntoIter<K, V>, fn((SafeHash, K, V)) -> (K, V)>
1289 /// HashMap keys iterator.
1290 #[stable(feature = "rust1", since = "1.0.0")]
1291 pub struct Keys<'a, K: 'a, V: 'a> {
1292 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
1295 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1296 impl<'a, K, V> Clone for Keys<'a, K, V> {
1297 fn clone(&self) -> Keys<'a, K, V> {
1299 inner: self.inner.clone()
1304 /// HashMap values iterator.
1305 #[stable(feature = "rust1", since = "1.0.0")]
1306 pub struct Values<'a, K: 'a, V: 'a> {
1307 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
1310 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1311 impl<'a, K, V> Clone for Values<'a, K, V> {
1312 fn clone(&self) -> Values<'a, K, V> {
1314 inner: self.inner.clone()
1319 /// HashMap drain iterator.
1320 #[unstable(feature = "std_misc",
1321 reason = "matches collection reform specification, waiting for dust to settle")]
1322 pub struct Drain<'a, K: 'a, V: 'a> {
1323 inner: iter::Map<table::Drain<'a, K, V>, fn((SafeHash, K, V)) -> (K, V)>
1326 /// A view into a single occupied location in a HashMap.
1327 #[unstable(feature = "std_misc",
1328 reason = "precise API still being fleshed out")]
1329 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1330 elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
1333 /// A view into a single empty location in a HashMap.
1334 #[unstable(feature = "std_misc",
1335 reason = "precise API still being fleshed out")]
1336 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1339 elem: VacantEntryState<K, V, &'a mut RawTable<K, V>>,
1342 /// A view into a single location in a map, which may be vacant or occupied.
1343 #[unstable(feature = "std_misc",
1344 reason = "precise API still being fleshed out")]
1345 pub enum Entry<'a, K: 'a, V: 'a> {
1346 /// An occupied Entry.
1347 Occupied(OccupiedEntry<'a, K, V>),
1349 Vacant(VacantEntry<'a, K, V>),
1352 /// Possible states of a VacantEntry.
1353 enum VacantEntryState<K, V, M> {
1354 /// The index is occupied, but the key to insert has precedence,
1355 /// and will kick the current one out on insertion.
1356 NeqElem(FullBucket<K, V, M>, usize),
1357 /// The index is genuinely vacant.
1358 NoElem(EmptyBucket<K, V, M>),
1361 #[stable(feature = "rust1", since = "1.0.0")]
1362 impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S>
1363 where K: Eq + Hash, S: HashState
1365 type Item = (&'a K, &'a V);
1366 type IntoIter = Iter<'a, K, V>;
1368 fn into_iter(self) -> Iter<'a, K, V> {
1373 #[stable(feature = "rust1", since = "1.0.0")]
1374 impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S>
1375 where K: Eq + Hash, S: HashState
1377 type Item = (&'a K, &'a mut V);
1378 type IntoIter = IterMut<'a, K, V>;
1380 fn into_iter(mut self) -> IterMut<'a, K, V> {
1385 #[stable(feature = "rust1", since = "1.0.0")]
1386 impl<K, V, S> IntoIterator for HashMap<K, V, S>
1387 where K: Eq + Hash, S: HashState
1390 type IntoIter = IntoIter<K, V>;
1392 fn into_iter(self) -> IntoIter<K, V> {
1397 #[stable(feature = "rust1", since = "1.0.0")]
1398 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1399 type Item = (&'a K, &'a V);
1401 #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1402 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1404 #[stable(feature = "rust1", since = "1.0.0")]
1405 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
1406 #[inline] fn len(&self) -> usize { self.inner.len() }
1409 #[stable(feature = "rust1", since = "1.0.0")]
1410 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1411 type Item = (&'a K, &'a mut V);
1413 #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1414 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1416 #[stable(feature = "rust1", since = "1.0.0")]
1417 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
1418 #[inline] fn len(&self) -> usize { self.inner.len() }
1421 #[stable(feature = "rust1", since = "1.0.0")]
1422 impl<K, V> Iterator for IntoIter<K, V> {
1425 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1426 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1428 #[stable(feature = "rust1", since = "1.0.0")]
1429 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1430 #[inline] fn len(&self) -> usize { self.inner.len() }
1433 #[stable(feature = "rust1", since = "1.0.0")]
1434 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1437 #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1438 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1440 #[stable(feature = "rust1", since = "1.0.0")]
1441 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {
1442 #[inline] fn len(&self) -> usize { self.inner.len() }
1445 #[stable(feature = "rust1", since = "1.0.0")]
1446 impl<'a, K, V> Iterator for Values<'a, K, V> {
1449 #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1450 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1452 #[stable(feature = "rust1", since = "1.0.0")]
1453 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {
1454 #[inline] fn len(&self) -> usize { self.inner.len() }
1457 #[stable(feature = "rust1", since = "1.0.0")]
1458 impl<'a, K, V> Iterator for Drain<'a, K, V> {
1461 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1462 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1464 #[stable(feature = "rust1", since = "1.0.0")]
1465 impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
1466 #[inline] fn len(&self) -> usize { self.inner.len() }
1469 #[unstable(feature = "std_misc",
1470 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1471 impl<'a, K, V> Entry<'a, K, V> {
1472 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant.
1473 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1475 Occupied(entry) => Ok(entry.into_mut()),
1476 Vacant(entry) => Err(entry),
1481 impl<'a, K, V> OccupiedEntry<'a, K, V> {
1482 /// Gets a reference to the value in the entry.
1483 #[stable(feature = "rust1", since = "1.0.0")]
1484 pub fn get(&self) -> &V {
1488 /// Gets a mutable reference to the value in the entry.
1489 #[stable(feature = "rust1", since = "1.0.0")]
1490 pub fn get_mut(&mut self) -> &mut V {
1491 self.elem.read_mut().1
1494 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
1495 /// with a lifetime bound to the map itself
1496 #[stable(feature = "rust1", since = "1.0.0")]
1497 pub fn into_mut(self) -> &'a mut V {
1498 self.elem.into_mut_refs().1
1501 /// Sets the value of the entry, and returns the entry's old value
1502 #[stable(feature = "rust1", since = "1.0.0")]
1503 pub fn insert(&mut self, mut value: V) -> V {
1504 let old_value = self.get_mut();
1505 mem::swap(&mut value, old_value);
1509 /// Takes the value out of the entry, and returns it
1510 #[stable(feature = "rust1", since = "1.0.0")]
1511 pub fn remove(self) -> V {
1512 pop_internal(self.elem).1
1516 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
1517 /// Sets the value of the entry with the VacantEntry's key,
1518 /// and returns a mutable reference to it
1519 #[stable(feature = "rust1", since = "1.0.0")]
1520 pub fn insert(self, value: V) -> &'a mut V {
1522 NeqElem(bucket, ib) => {
1523 robin_hood(bucket, ib, self.hash, self.key, value)
1526 bucket.put(self.hash, self.key, value).into_mut_refs().1
1532 #[stable(feature = "rust1", since = "1.0.0")]
1533 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
1534 where K: Eq + Hash, S: HashState + Default
1536 fn from_iter<T: IntoIterator<Item=(K, V)>>(iterable: T) -> HashMap<K, V, S> {
1537 let iter = iterable.into_iter();
1538 let lower = iter.size_hint().0;
1539 let mut map = HashMap::with_capacity_and_hash_state(lower,
1540 Default::default());
1546 #[stable(feature = "rust1", since = "1.0.0")]
1547 impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>
1548 where K: Eq + Hash, S: HashState
1550 fn extend<T: IntoIterator<Item=(K, V)>>(&mut self, iter: T) {
1551 for (k, v) in iter {
1558 /// `RandomState` is the default state for `HashMap` types.
1560 /// A particular instance `RandomState` will create the same instances of
1561 /// `Hasher`, but the hashers created by two different `RandomState`
1562 /// instances are unlikely to produce the same result for the same values.
1564 #[unstable(feature = "std_misc",
1565 reason = "hashing an hash maps may be altered")]
1566 pub struct RandomState {
1571 #[unstable(feature = "std_misc",
1572 reason = "hashing an hash maps may be altered")]
1574 /// Construct a new `RandomState` that is initialized with random keys.
1576 #[allow(deprecated)]
1577 pub fn new() -> RandomState {
1578 let mut r = rand::thread_rng();
1579 RandomState { k0: r.gen(), k1: r.gen() }
1583 #[unstable(feature = "std_misc",
1584 reason = "hashing an hash maps may be altered")]
1585 impl HashState for RandomState {
1586 type Hasher = SipHasher;
1587 fn hasher(&self) -> SipHasher {
1588 SipHasher::new_with_keys(self.k0, self.k1)
1592 #[unstable(feature = "std_misc",
1593 reason = "hashing an hash maps may be altered")]
1594 impl Default for RandomState {
1596 fn default() -> RandomState {
1606 use super::Entry::{Occupied, Vacant};
1607 use iter::{range_inclusive, range_step_inclusive, repeat};
1609 use rand::{weak_rng, Rng};
1612 fn test_create_capacity_zero() {
1613 let mut m = HashMap::with_capacity(0);
1615 assert!(m.insert(1, 1).is_none());
1617 assert!(m.contains_key(&1));
1618 assert!(!m.contains_key(&0));
1623 let mut m = HashMap::new();
1624 assert_eq!(m.len(), 0);
1625 assert!(m.insert(1, 2).is_none());
1626 assert_eq!(m.len(), 1);
1627 assert!(m.insert(2, 4).is_none());
1628 assert_eq!(m.len(), 2);
1629 assert_eq!(*m.get(&1).unwrap(), 2);
1630 assert_eq!(*m.get(&2).unwrap(), 4);
1633 thread_local! { static DROP_VECTOR: RefCell<Vec<int>> = RefCell::new(Vec::new()) }
1635 #[derive(Hash, PartialEq, Eq)]
1641 fn new(k: usize) -> Dropable {
1642 DROP_VECTOR.with(|slot| {
1643 slot.borrow_mut()[k] += 1;
1650 impl Drop for Dropable {
1651 fn drop(&mut self) {
1652 DROP_VECTOR.with(|slot| {
1653 slot.borrow_mut()[self.k] -= 1;
1658 impl Clone for Dropable {
1659 fn clone(&self) -> Dropable {
1660 Dropable::new(self.k)
1666 DROP_VECTOR.with(|slot| {
1667 *slot.borrow_mut() = repeat(0).take(200).collect();
1671 let mut m = HashMap::new();
1673 DROP_VECTOR.with(|v| {
1675 assert_eq!(v.borrow()[i], 0);
1680 let d1 = Dropable::new(i);
1681 let d2 = Dropable::new(i+100);
1685 DROP_VECTOR.with(|v| {
1687 assert_eq!(v.borrow()[i], 1);
1692 let k = Dropable::new(i);
1693 let v = m.remove(&k);
1695 assert!(v.is_some());
1697 DROP_VECTOR.with(|v| {
1698 assert_eq!(v.borrow()[i], 1);
1699 assert_eq!(v.borrow()[i+100], 1);
1703 DROP_VECTOR.with(|v| {
1705 assert_eq!(v.borrow()[i], 0);
1706 assert_eq!(v.borrow()[i+100], 0);
1710 assert_eq!(v.borrow()[i], 1);
1711 assert_eq!(v.borrow()[i+100], 1);
1716 DROP_VECTOR.with(|v| {
1718 assert_eq!(v.borrow()[i], 0);
1724 fn test_move_iter_drops() {
1725 DROP_VECTOR.with(|v| {
1726 *v.borrow_mut() = repeat(0).take(200).collect();
1730 let mut hm = HashMap::new();
1732 DROP_VECTOR.with(|v| {
1734 assert_eq!(v.borrow()[i], 0);
1739 let d1 = Dropable::new(i);
1740 let d2 = Dropable::new(i+100);
1744 DROP_VECTOR.with(|v| {
1746 assert_eq!(v.borrow()[i], 1);
1753 // By the way, ensure that cloning doesn't screw up the dropping.
1757 let mut half = hm.into_iter().take(50);
1759 DROP_VECTOR.with(|v| {
1761 assert_eq!(v.borrow()[i], 1);
1765 for _ in half.by_ref() {}
1767 DROP_VECTOR.with(|v| {
1768 let nk = (0..100).filter(|&i| {
1772 let nv = (0..100).filter(|&i| {
1773 v.borrow()[i+100] == 1
1781 DROP_VECTOR.with(|v| {
1783 assert_eq!(v.borrow()[i], 0);
1789 fn test_empty_pop() {
1790 let mut m: HashMap<int, bool> = HashMap::new();
1791 assert_eq!(m.remove(&0), None);
1795 fn test_lots_of_insertions() {
1796 let mut m = HashMap::new();
1798 // Try this a few times to make sure we never screw up the hashmap's
1801 assert!(m.is_empty());
1803 for i in range_inclusive(1, 1000) {
1804 assert!(m.insert(i, i).is_none());
1806 for j in range_inclusive(1, i) {
1808 assert_eq!(r, Some(&j));
1811 for j in range_inclusive(i+1, 1000) {
1813 assert_eq!(r, None);
1817 for i in range_inclusive(1001, 2000) {
1818 assert!(!m.contains_key(&i));
1822 for i in range_inclusive(1, 1000) {
1823 assert!(m.remove(&i).is_some());
1825 for j in range_inclusive(1, i) {
1826 assert!(!m.contains_key(&j));
1829 for j in range_inclusive(i+1, 1000) {
1830 assert!(m.contains_key(&j));
1834 for i in range_inclusive(1, 1000) {
1835 assert!(!m.contains_key(&i));
1838 for i in range_inclusive(1, 1000) {
1839 assert!(m.insert(i, i).is_none());
1843 for i in range_step_inclusive(1000, 1, -1) {
1844 assert!(m.remove(&i).is_some());
1846 for j in range_inclusive(i, 1000) {
1847 assert!(!m.contains_key(&j));
1850 for j in range_inclusive(1, i-1) {
1851 assert!(m.contains_key(&j));
1858 fn test_find_mut() {
1859 let mut m = HashMap::new();
1860 assert!(m.insert(1, 12).is_none());
1861 assert!(m.insert(2, 8).is_none());
1862 assert!(m.insert(5, 14).is_none());
1864 match m.get_mut(&5) {
1865 None => panic!(), Some(x) => *x = new
1867 assert_eq!(m.get(&5), Some(&new));
1871 fn test_insert_overwrite() {
1872 let mut m = HashMap::new();
1873 assert!(m.insert(1, 2).is_none());
1874 assert_eq!(*m.get(&1).unwrap(), 2);
1875 assert!(!m.insert(1, 3).is_none());
1876 assert_eq!(*m.get(&1).unwrap(), 3);
1880 fn test_insert_conflicts() {
1881 let mut m = HashMap::with_capacity(4);
1882 assert!(m.insert(1, 2).is_none());
1883 assert!(m.insert(5, 3).is_none());
1884 assert!(m.insert(9, 4).is_none());
1885 assert_eq!(*m.get(&9).unwrap(), 4);
1886 assert_eq!(*m.get(&5).unwrap(), 3);
1887 assert_eq!(*m.get(&1).unwrap(), 2);
1891 fn test_conflict_remove() {
1892 let mut m = HashMap::with_capacity(4);
1893 assert!(m.insert(1, 2).is_none());
1894 assert_eq!(*m.get(&1).unwrap(), 2);
1895 assert!(m.insert(5, 3).is_none());
1896 assert_eq!(*m.get(&1).unwrap(), 2);
1897 assert_eq!(*m.get(&5).unwrap(), 3);
1898 assert!(m.insert(9, 4).is_none());
1899 assert_eq!(*m.get(&1).unwrap(), 2);
1900 assert_eq!(*m.get(&5).unwrap(), 3);
1901 assert_eq!(*m.get(&9).unwrap(), 4);
1902 assert!(m.remove(&1).is_some());
1903 assert_eq!(*m.get(&9).unwrap(), 4);
1904 assert_eq!(*m.get(&5).unwrap(), 3);
1908 fn test_is_empty() {
1909 let mut m = HashMap::with_capacity(4);
1910 assert!(m.insert(1, 2).is_none());
1911 assert!(!m.is_empty());
1912 assert!(m.remove(&1).is_some());
1913 assert!(m.is_empty());
1918 let mut m = HashMap::new();
1920 assert_eq!(m.remove(&1), Some(2));
1921 assert_eq!(m.remove(&1), None);
1926 let mut m = HashMap::with_capacity(4);
1928 assert!(m.insert(i, i*2).is_none());
1930 assert_eq!(m.len(), 32);
1932 let mut observed: u32 = 0;
1935 assert_eq!(*v, *k * 2);
1936 observed |= 1 << *k;
1938 assert_eq!(observed, 0xFFFF_FFFF);
1943 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1944 let map: HashMap<_, _> = vec.into_iter().collect();
1945 let keys: Vec<_> = map.keys().cloned().collect();
1946 assert_eq!(keys.len(), 3);
1947 assert!(keys.contains(&1));
1948 assert!(keys.contains(&2));
1949 assert!(keys.contains(&3));
1954 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1955 let map: HashMap<_, _> = vec.into_iter().collect();
1956 let values: Vec<_> = map.values().cloned().collect();
1957 assert_eq!(values.len(), 3);
1958 assert!(values.contains(&'a'));
1959 assert!(values.contains(&'b'));
1960 assert!(values.contains(&'c'));
1965 let mut m = HashMap::new();
1966 assert!(m.get(&1).is_none());
1970 Some(v) => assert_eq!(*v, 2)
1976 let mut m1 = HashMap::new();
1981 let mut m2 = HashMap::new();
1994 let mut map = HashMap::new();
1995 let empty: HashMap<i32, i32> = HashMap::new();
2000 let map_str = format!("{:?}", map);
2002 assert!(map_str == "{1: 2, 3: 4}" ||
2003 map_str == "{3: 4, 1: 2}");
2004 assert_eq!(format!("{:?}", empty), "{}");
2009 let mut m = HashMap::new();
2011 assert_eq!(m.len(), 0);
2012 assert!(m.is_empty());
2015 let old_cap = m.table.capacity();
2016 while old_cap == m.table.capacity() {
2021 assert_eq!(m.len(), i);
2022 assert!(!m.is_empty());
2026 fn test_behavior_resize_policy() {
2027 let mut m = HashMap::new();
2029 assert_eq!(m.len(), 0);
2030 assert_eq!(m.table.capacity(), 0);
2031 assert!(m.is_empty());
2035 assert!(m.is_empty());
2036 let initial_cap = m.table.capacity();
2037 m.reserve(initial_cap);
2038 let cap = m.table.capacity();
2040 assert_eq!(cap, initial_cap * 2);
2043 for _ in 0..cap * 3 / 4 {
2047 // three quarters full
2049 assert_eq!(m.len(), i);
2050 assert_eq!(m.table.capacity(), cap);
2052 for _ in 0..cap / 4 {
2058 let new_cap = m.table.capacity();
2059 assert_eq!(new_cap, cap * 2);
2061 for _ in 0..cap / 2 - 1 {
2064 assert_eq!(m.table.capacity(), new_cap);
2066 // A little more than one quarter full.
2068 assert_eq!(m.table.capacity(), cap);
2069 // again, a little more than half full
2070 for _ in 0..cap / 2 - 1 {
2076 assert_eq!(m.len(), i);
2077 assert!(!m.is_empty());
2078 assert_eq!(m.table.capacity(), initial_cap);
2082 fn test_reserve_shrink_to_fit() {
2083 let mut m = HashMap::new();
2086 assert!(m.capacity() >= m.len());
2092 let usable_cap = m.capacity();
2093 for i in 128..(128 + 256) {
2095 assert_eq!(m.capacity(), usable_cap);
2098 for i in 100..(128 + 256) {
2099 assert_eq!(m.remove(&i), Some(i));
2103 assert_eq!(m.len(), 100);
2104 assert!(!m.is_empty());
2105 assert!(m.capacity() >= m.len());
2108 assert_eq!(m.remove(&i), Some(i));
2113 assert_eq!(m.len(), 1);
2114 assert!(m.capacity() >= m.len());
2115 assert_eq!(m.remove(&0), Some(0));
2119 fn test_from_iter() {
2120 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2122 let map: HashMap<_, _> = xs.iter().cloned().collect();
2124 for &(k, v) in &xs {
2125 assert_eq!(map.get(&k), Some(&v));
2130 fn test_size_hint() {
2131 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2133 let map: HashMap<_, _> = xs.iter().cloned().collect();
2135 let mut iter = map.iter();
2137 for _ in iter.by_ref().take(3) {}
2139 assert_eq!(iter.size_hint(), (3, Some(3)));
2143 fn test_iter_len() {
2144 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2146 let map: HashMap<_, _> = xs.iter().cloned().collect();
2148 let mut iter = map.iter();
2150 for _ in iter.by_ref().take(3) {}
2152 assert_eq!(iter.len(), 3);
2156 fn test_mut_size_hint() {
2157 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2159 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2161 let mut iter = map.iter_mut();
2163 for _ in iter.by_ref().take(3) {}
2165 assert_eq!(iter.size_hint(), (3, Some(3)));
2169 fn test_iter_mut_len() {
2170 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2172 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2174 let mut iter = map.iter_mut();
2176 for _ in iter.by_ref().take(3) {}
2178 assert_eq!(iter.len(), 3);
2183 let mut map = HashMap::new();
2189 assert_eq!(map[2], 1);
2194 fn test_index_nonexistent() {
2195 let mut map = HashMap::new();
2206 let xs = [(1, 10), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
2208 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2210 // Existing key (insert)
2211 match map.entry(1) {
2212 Vacant(_) => unreachable!(),
2213 Occupied(mut view) => {
2214 assert_eq!(view.get(), &10);
2215 assert_eq!(view.insert(100), 10);
2218 assert_eq!(map.get(&1).unwrap(), &100);
2219 assert_eq!(map.len(), 6);
2222 // Existing key (update)
2223 match map.entry(2) {
2224 Vacant(_) => unreachable!(),
2225 Occupied(mut view) => {
2226 let v = view.get_mut();
2227 let new_v = (*v) * 10;
2231 assert_eq!(map.get(&2).unwrap(), &200);
2232 assert_eq!(map.len(), 6);
2234 // Existing key (take)
2235 match map.entry(3) {
2236 Vacant(_) => unreachable!(),
2238 assert_eq!(view.remove(), 30);
2241 assert_eq!(map.get(&3), None);
2242 assert_eq!(map.len(), 5);
2245 // Inexistent key (insert)
2246 match map.entry(10) {
2247 Occupied(_) => unreachable!(),
2249 assert_eq!(*view.insert(1000), 1000);
2252 assert_eq!(map.get(&10).unwrap(), &1000);
2253 assert_eq!(map.len(), 6);
2257 fn test_entry_take_doesnt_corrupt() {
2258 #![allow(deprecated)] //rand
2260 fn check(m: &HashMap<isize, ()>) {
2262 assert!(m.contains_key(k),
2263 "{} is in keys() but not in the map?", k);
2267 let mut m = HashMap::new();
2268 let mut rng = weak_rng();
2270 // Populate the map with some items.
2272 let x = rng.gen_range(-10, 10);
2277 let x = rng.gen_range(-10, 10);
2281 println!("{}: remove {}", i, x);