1 // Copyright 2014 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::*;
17 use borrow::BorrowFrom;
19 use cmp::{max, Eq, PartialEq};
21 use fmt::{self, Show};
22 use hash::{Hash, Hasher, RandomSipHasher};
23 use iter::{self, Iterator, IteratorExt, FromIterator, Extend, Map};
25 use mem::{self, replace};
26 use num::{Int, UnsignedInt};
27 use ops::{Deref, FnMut, Index, IndexMut};
29 use option::Option::{Some, None};
31 use result::Result::{Ok, Err};
43 use super::table::BucketState::{
48 const INITIAL_LOG2_CAP: uint = 5;
49 pub const INITIAL_CAPACITY: uint = 1 << INITIAL_LOG2_CAP; // 2^5
51 /// The default behavior of HashMap implements a load factor of 90.9%.
52 /// This behavior is characterized by the following condition:
54 /// - if size > 0.909 * capacity: grow the map
56 struct DefaultResizePolicy;
58 impl DefaultResizePolicy {
59 fn new() -> DefaultResizePolicy {
64 fn min_capacity(&self, usable_size: uint) -> uint {
65 // Here, we are rephrasing the logic by specifying the lower limit
68 // - if `cap < size * 1.1`: grow the map
72 /// An inverse of `min_capacity`, approximately.
74 fn usable_capacity(&self, cap: uint) -> uint {
75 // As the number of entries approaches usable capacity,
76 // min_capacity(size) must be smaller than the internal capacity,
77 // so that the map is not resized:
78 // `min_capacity(usable_capacity(x)) <= x`.
79 // The lef-hand side can only be smaller due to flooring by integer
82 // This doesn't have to be checked for overflow since allocation size
83 // in bytes will overflow earlier than multiplication by 10.
89 fn test_resize_policy() {
91 let rp = DefaultResizePolicy;
92 for n in range(0u, 1000) {
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 doc.rs
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, Show)]
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"), 25u);
290 /// vikings.insert(Viking::new("Olaf", "Denmark"), 24u);
291 /// vikings.insert(Viking::new("Harald", "Iceland"), 12u);
293 /// // Use derived implementation to print the status of the vikings.
294 /// for (viking, health) in vikings.iter() {
295 /// println!("{:?} has {} hp", viking, health);
300 pub struct HashMap<K, V, H = RandomSipHasher> {
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),
443 impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
444 fn make_hash<X: ?Sized + Hash<S>>(&self, x: &X) -> SafeHash {
445 table::make_hash(&self.hasher, x)
448 /// Search for a key, yielding the index if it's found in the hashtable.
449 /// If you already have the hash for the key lying around, use
451 fn search<'a, Q: ?Sized>(&'a self, q: &Q) -> Option<FullBucketImm<'a, K, V>>
452 where Q: BorrowFrom<K> + Eq + Hash<S>
454 let hash = self.make_hash(q);
455 search_hashed(&self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
459 fn search_mut<'a, Q: ?Sized>(&'a mut self, q: &Q) -> Option<FullBucketMut<'a, K, V>>
460 where Q: BorrowFrom<K> + Eq + Hash<S>
462 let hash = self.make_hash(q);
463 search_hashed(&mut self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
467 // The caller should ensure that invariants by Robin Hood Hashing hold.
468 fn insert_hashed_ordered(&mut self, hash: SafeHash, k: K, v: V) {
469 let cap = self.table.capacity();
470 let mut buckets = Bucket::new(&mut self.table, hash);
471 let ib = buckets.index();
473 while buckets.index() != ib + cap {
474 // We don't need to compare hashes for value swap.
475 // Not even DIBs for Robin Hood.
476 buckets = match buckets.peek() {
478 empty.put(hash, k, v);
481 Full(b) => b.into_bucket()
485 panic!("Internal HashMap error: Out of space.");
489 impl<K: Hash + Eq, V> HashMap<K, V, RandomSipHasher> {
490 /// Create an empty HashMap.
495 /// use std::collections::HashMap;
496 /// let mut map: HashMap<&str, int> = HashMap::new();
500 pub fn new() -> HashMap<K, V, RandomSipHasher> {
501 let hasher = RandomSipHasher::new();
502 HashMap::with_hasher(hasher)
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);
515 pub fn with_capacity(capacity: uint) -> HashMap<K, V, RandomSipHasher> {
516 let hasher = RandomSipHasher::new();
517 HashMap::with_capacity_and_hasher(capacity, hasher)
522 impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
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::hash::sip::SipHasher;
533 /// let h = SipHasher::new();
534 /// let mut map = HashMap::with_hasher(h);
535 /// map.insert(1i, 2u);
538 #[unstable = "hasher stuff is unclear"]
539 pub fn with_hasher(hasher: H) -> HashMap<K, V, H> {
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::hash::sip::SipHasher;
561 /// let h = SipHasher::new();
562 /// let mut map = HashMap::with_capacity_and_hasher(10, h);
563 /// map.insert(1i, 2u);
566 #[unstable = "hasher stuff is unclear"]
567 pub fn with_capacity_and_hasher(capacity: uint, hasher: H) -> HashMap<K, V, H> {
568 let resize_policy = DefaultResizePolicy::new();
569 let min_cap = max(INITIAL_CAPACITY, resize_policy.min_capacity(capacity));
570 let internal_cap = min_cap.checked_next_power_of_two().expect("capacity overflow");
571 assert!(internal_cap >= capacity, "capacity overflow");
574 resize_policy: resize_policy,
575 table: RawTable::new(internal_cap),
579 /// Returns the number of elements the map can hold without reallocating.
584 /// use std::collections::HashMap;
585 /// let map: HashMap<int, int> = HashMap::with_capacity(100);
586 /// assert!(map.capacity() >= 100);
590 pub fn capacity(&self) -> uint {
591 self.resize_policy.usable_capacity(self.table.capacity())
594 /// Reserves capacity for at least `additional` more elements to be inserted
595 /// in the `HashMap`. The collection may reserve more space to avoid
596 /// frequent reallocations.
600 /// Panics if the new allocation size overflows `uint`.
605 /// use std::collections::HashMap;
606 /// let mut map: HashMap<&str, int> = HashMap::new();
610 pub fn reserve(&mut self, additional: uint) {
611 let new_size = self.len().checked_add(additional).expect("capacity overflow");
612 let min_cap = self.resize_policy.min_capacity(new_size);
614 // An invalid value shouldn't make us run out of space. This includes
615 // an overflow check.
616 assert!(new_size <= min_cap);
618 if self.table.capacity() < min_cap {
619 let new_capacity = max(min_cap.next_power_of_two(), INITIAL_CAPACITY);
620 self.resize(new_capacity);
624 /// Resizes the internal vectors to a new capacity. It's your responsibility to:
625 /// 1) Make sure the new capacity is enough for all the elements, accounting
626 /// for the load factor.
627 /// 2) Ensure new_capacity is a power of two or zero.
628 fn resize(&mut self, new_capacity: uint) {
629 assert!(self.table.size() <= new_capacity);
630 assert!(new_capacity.is_power_of_two() || new_capacity == 0);
632 let mut old_table = replace(&mut self.table, RawTable::new(new_capacity));
633 let old_size = old_table.size();
635 if old_table.capacity() == 0 || old_table.size() == 0 {
640 // Specialization of the other branch.
641 let mut bucket = Bucket::first(&mut old_table);
643 // "So a few of the first shall be last: for many be called,
646 // We'll most likely encounter a few buckets at the beginning that
647 // have their initial buckets near the end of the table. They were
648 // placed at the beginning as the probe wrapped around the table
649 // during insertion. We must skip forward to a bucket that won't
650 // get reinserted too early and won't unfairly steal others spot.
651 // This eliminates the need for robin hood.
653 bucket = match bucket.peek() {
655 if full.distance() == 0 {
656 // This bucket occupies its ideal spot.
657 // It indicates the start of another "cluster".
658 bucket = full.into_bucket();
661 // Leaving this bucket in the last cluster for later.
665 // Encountered a hole between clusters.
672 // This is how the buckets might be laid out in memory:
673 // ($ marks an initialized bucket)
675 // |$$$_$$$$$$_$$$$$|
677 // But we've skipped the entire initial cluster of buckets
678 // and will continue iteration in this order:
681 // ^ wrap around once end is reached
684 // ^ exit once table.size == 0
686 bucket = match bucket.peek() {
688 let h = bucket.hash();
689 let (b, k, v) = bucket.take();
690 self.insert_hashed_ordered(h, k, v);
692 let t = b.table(); // FIXME "lifetime too short".
693 if t.size() == 0 { break }
697 Empty(b) => b.into_bucket()
702 assert_eq!(self.table.size(), old_size);
705 /// Shrinks the capacity of the map as much as possible. It will drop
706 /// down as much as possible while maintaining the internal rules
707 /// and possibly leaving some space in accordance with the resize policy.
712 /// use std::collections::HashMap;
714 /// let mut map: HashMap<int, int> = HashMap::with_capacity(100);
715 /// map.insert(1, 2);
716 /// map.insert(3, 4);
717 /// assert!(map.capacity() >= 100);
718 /// map.shrink_to_fit();
719 /// assert!(map.capacity() >= 2);
722 pub fn shrink_to_fit(&mut self) {
723 let min_capacity = self.resize_policy.min_capacity(self.len());
724 let min_capacity = max(min_capacity.next_power_of_two(), INITIAL_CAPACITY);
726 // An invalid value shouldn't make us run out of space.
727 debug_assert!(self.len() <= min_capacity);
729 if self.table.capacity() != min_capacity {
730 let old_table = replace(&mut self.table, RawTable::new(min_capacity));
731 let old_size = old_table.size();
733 // Shrink the table. Naive algorithm for resizing:
734 for (h, k, v) in old_table.into_iter() {
735 self.insert_hashed_nocheck(h, k, v);
738 debug_assert_eq!(self.table.size(), old_size);
742 /// Insert a pre-hashed key-value pair, without first checking
743 /// that there's enough room in the buckets. Returns a reference to the
744 /// newly insert value.
746 /// If the key already exists, the hashtable will be returned untouched
747 /// and a reference to the existing element will be returned.
748 fn insert_hashed_nocheck(&mut self, hash: SafeHash, k: K, v: V) -> &mut V {
749 self.insert_or_replace_with(hash, k, v, |_, _, _| ())
752 fn insert_or_replace_with<'a, F>(&'a mut self,
756 mut found_existing: F)
758 F: FnMut(&mut K, &mut V, V),
760 // Worst case, we'll find one empty bucket among `size + 1` buckets.
761 let size = self.table.size();
762 let mut probe = Bucket::new(&mut self.table, hash);
763 let ib = probe.index();
766 let mut bucket = match probe.peek() {
769 return bucket.put(hash, k, v).into_mut_refs().1;
771 Full(bucket) => bucket
775 if bucket.hash() == hash {
777 if k == *bucket.read_mut().0 {
778 let (bucket_k, bucket_v) = bucket.into_mut_refs();
779 debug_assert!(k == *bucket_k);
780 // Key already exists. Get its reference.
781 found_existing(bucket_k, bucket_v, v);
786 let robin_ib = bucket.index() as int - bucket.distance() as int;
788 if (ib as int) < robin_ib {
789 // Found a luckier bucket than me. Better steal his spot.
790 return robin_hood(bucket, robin_ib as uint, hash, k, v);
793 probe = bucket.next();
794 assert!(probe.index() != ib + size + 1);
798 /// An iterator visiting all keys in arbitrary order.
799 /// Iterator element type is `&'a K`.
804 /// use std::collections::HashMap;
806 /// let mut map = HashMap::new();
807 /// map.insert("a", 1i);
808 /// map.insert("b", 2);
809 /// map.insert("c", 3);
811 /// for key in map.keys() {
812 /// println!("{}", key);
816 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
817 fn first<A, B>((a, _): (A, B)) -> A { a }
818 let first: fn((&'a K,&'a V)) -> &'a K = first; // coerce to fn ptr
820 Keys { inner: self.iter().map(first) }
823 /// An iterator visiting all values in arbitrary order.
824 /// Iterator element type is `&'a V`.
829 /// use std::collections::HashMap;
831 /// let mut map = HashMap::new();
832 /// map.insert("a", 1i);
833 /// map.insert("b", 2);
834 /// map.insert("c", 3);
836 /// for key in map.values() {
837 /// println!("{}", key);
841 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
842 fn second<A, B>((_, b): (A, B)) -> B { b }
843 let second: fn((&'a K,&'a V)) -> &'a V = second; // coerce to fn ptr
845 Values { inner: self.iter().map(second) }
848 /// An iterator visiting all key-value pairs in arbitrary order.
849 /// Iterator element type is `(&'a K, &'a V)`.
854 /// use std::collections::HashMap;
856 /// let mut map = HashMap::new();
857 /// map.insert("a", 1i);
858 /// map.insert("b", 2);
859 /// map.insert("c", 3);
861 /// for (key, val) in map.iter() {
862 /// println!("key: {} val: {}", key, val);
866 pub fn iter(&self) -> Iter<K, V> {
867 Iter { inner: self.table.iter() }
870 /// An iterator visiting all key-value pairs in arbitrary order,
871 /// with mutable references to the values.
872 /// Iterator element type is `(&'a K, &'a mut V)`.
877 /// use std::collections::HashMap;
879 /// let mut map = HashMap::new();
880 /// map.insert("a", 1i);
881 /// map.insert("b", 2);
882 /// map.insert("c", 3);
884 /// // Update all values
885 /// for (_, val) in map.iter_mut() {
889 /// for (key, val) in map.iter() {
890 /// println!("key: {} val: {}", key, val);
894 pub fn iter_mut(&mut self) -> IterMut<K, V> {
895 IterMut { inner: self.table.iter_mut() }
898 /// Creates a consuming iterator, that is, one that moves each key-value
899 /// pair out of the map in arbitrary order. The map cannot be used after
905 /// use std::collections::HashMap;
907 /// let mut map = HashMap::new();
908 /// map.insert("a", 1i);
909 /// map.insert("b", 2);
910 /// map.insert("c", 3);
912 /// // Not possible with .iter()
913 /// let vec: Vec<(&str, int)> = map.into_iter().collect();
916 pub fn into_iter(self) -> IntoIter<K, V> {
917 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
918 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two;
921 inner: self.table.into_iter().map(last_two)
925 /// Gets the given key's corresponding entry in the map for in-place manipulation.
926 #[unstable = "precise API still being fleshed out"]
927 pub fn entry<'a>(&'a mut self, key: K) -> Entry<'a, K, V>
932 let hash = self.make_hash(&key);
933 search_entry_hashed(&mut self.table, hash, key)
936 /// Return 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(1u, "a");
946 /// assert_eq!(a.len(), 1);
949 pub fn len(&self) -> uint { self.table.size() }
951 /// Return 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(1u, "a");
961 /// assert!(!a.is_empty());
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(1u, "a");
977 /// a.insert(2u, "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 = "matches collection reform specification, waiting for dust to settle"]
988 pub fn drain(&mut self) -> Drain<K, V> {
989 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
990 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two; // coerce to fn pointer
993 inner: self.table.drain().map(last_two),
997 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
1003 /// use std::collections::HashMap;
1005 /// let mut a = HashMap::new();
1006 /// a.insert(1u, "a");
1008 /// assert!(a.is_empty());
1012 pub fn clear(&mut self) {
1016 /// Returns a reference to the value corresponding to the key.
1018 /// The key may be any borrowed form of the map's key type, but
1019 /// `Hash` and `Eq` on the borrowed form *must* match those for
1025 /// use std::collections::HashMap;
1027 /// let mut map = HashMap::new();
1028 /// map.insert(1u, "a");
1029 /// assert_eq!(map.get(&1), Some(&"a"));
1030 /// assert_eq!(map.get(&2), None);
1033 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
1034 where Q: Hash<S> + Eq + BorrowFrom<K>
1036 self.search(k).map(|bucket| bucket.into_refs().1)
1039 /// Returns true if the map contains a value for the specified key.
1041 /// The key may be any borrowed form of the map's key type, but
1042 /// `Hash` and `Eq` on the borrowed form *must* match those for
1048 /// use std::collections::HashMap;
1050 /// let mut map = HashMap::new();
1051 /// map.insert(1u, "a");
1052 /// assert_eq!(map.contains_key(&1), true);
1053 /// assert_eq!(map.contains_key(&2), false);
1056 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
1057 where Q: Hash<S> + Eq + BorrowFrom<K>
1059 self.search(k).is_some()
1062 /// Returns a mutable reference to the value corresponding to the key.
1064 /// The key may be any borrowed form of the map's key type, but
1065 /// `Hash` and `Eq` on the borrowed form *must* match those for
1071 /// use std::collections::HashMap;
1073 /// let mut map = HashMap::new();
1074 /// map.insert(1u, "a");
1075 /// match map.get_mut(&1) {
1076 /// Some(x) => *x = "b",
1079 /// assert_eq!(map[1], "b");
1082 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
1083 where Q: Hash<S> + Eq + BorrowFrom<K>
1085 self.search_mut(k).map(|bucket| bucket.into_mut_refs().1)
1088 /// Inserts a key-value pair from the map. If the key already had a value
1089 /// present in the map, that value is returned. Otherwise, `None` is returned.
1094 /// use std::collections::HashMap;
1096 /// let mut map = HashMap::new();
1097 /// assert_eq!(map.insert(37u, "a"), None);
1098 /// assert_eq!(map.is_empty(), false);
1100 /// map.insert(37, "b");
1101 /// assert_eq!(map.insert(37, "c"), Some("b"));
1102 /// assert_eq!(map[37], "c");
1105 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1106 let hash = self.make_hash(&k);
1109 let mut retval = None;
1110 self.insert_or_replace_with(hash, k, v, |_, val_ref, val| {
1111 retval = Some(replace(val_ref, val));
1116 /// Removes a key from the map, returning the value at the key if the key
1117 /// was previously in the map.
1119 /// The key may be any borrowed form of the map's key type, but
1120 /// `Hash` and `Eq` on the borrowed form *must* match those for
1126 /// use std::collections::HashMap;
1128 /// let mut map = HashMap::new();
1129 /// map.insert(1u, "a");
1130 /// assert_eq!(map.remove(&1), Some("a"));
1131 /// assert_eq!(map.remove(&1), None);
1134 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
1135 where Q: Hash<S> + Eq + BorrowFrom<K>
1137 if self.table.size() == 0 {
1141 self.search_mut(k).map(|bucket| pop_internal(bucket).1)
1145 fn search_entry_hashed<'a, K: Eq, V>(table: &'a mut RawTable<K,V>, hash: SafeHash, k: K)
1148 // Worst case, we'll find one empty bucket among `size + 1` buckets.
1149 let size = table.size();
1150 let mut probe = Bucket::new(table, hash);
1151 let ib = probe.index();
1154 let bucket = match probe.peek() {
1157 return Vacant(VacantEntry {
1160 elem: NoElem(bucket),
1163 Full(bucket) => bucket
1167 if bucket.hash() == hash {
1169 if k == *bucket.read().0 {
1170 return Occupied(OccupiedEntry{
1176 let robin_ib = bucket.index() as int - bucket.distance() as int;
1178 if (ib as int) < robin_ib {
1179 // Found a luckier bucket than me. Better steal his spot.
1180 return Vacant(VacantEntry {
1183 elem: NeqElem(bucket, robin_ib as uint),
1187 probe = bucket.next();
1188 assert!(probe.index() != ib + size + 1);
1194 impl<K: Eq + Hash<S>, V: PartialEq, S, H: Hasher<S>> PartialEq for HashMap<K, V, H> {
1195 fn eq(&self, other: &HashMap<K, V, H>) -> bool {
1196 if self.len() != other.len() { return false; }
1198 self.iter().all(|(key, value)|
1199 other.get(key).map_or(false, |v| *value == *v)
1206 impl<K: Eq + Hash<S>, V: Eq, S, H: Hasher<S>> Eq for HashMap<K, V, H> {}
1210 impl<K: Eq + Hash<S> + Show, V: Show, S, H: Hasher<S>> Show for HashMap<K, V, H> {
1211 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1212 try!(write!(f, "HashMap {{"));
1214 for (i, (k, v)) in self.iter().enumerate() {
1215 if i != 0 { try!(write!(f, ", ")); }
1216 try!(write!(f, "{:?}: {:?}", *k, *v));
1225 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> Default for HashMap<K, V, H> {
1227 fn default() -> HashMap<K, V, H> {
1228 HashMap::with_hasher(Default::default())
1234 impl<K: Hash<S> + Eq, Q: ?Sized, V, S, H: Hasher<S>> Index<Q> for HashMap<K, V, H>
1235 where Q: BorrowFrom<K> + Hash<S> + Eq
1240 fn index<'a>(&'a self, index: &Q) -> &'a V {
1241 self.get(index).expect("no entry found for key")
1247 impl<K: Hash<S> + Eq, Q: ?Sized, V, S, H: Hasher<S>> IndexMut<Q> for HashMap<K, V, H>
1248 where Q: BorrowFrom<K> + Hash<S> + Eq
1253 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1254 self.get_mut(index).expect("no entry found for key")
1258 /// HashMap iterator
1260 pub struct Iter<'a, K: 'a, V: 'a> {
1261 inner: table::Iter<'a, K, V>
1264 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1265 impl<'a, K, V> Clone for Iter<'a, K, V> {
1266 fn clone(&self) -> Iter<'a, K, V> {
1268 inner: self.inner.clone()
1273 /// HashMap mutable values iterator
1275 pub struct IterMut<'a, K: 'a, V: 'a> {
1276 inner: table::IterMut<'a, K, V>
1279 /// HashMap move iterator
1281 pub struct IntoIter<K, V> {
1285 table::IntoIter<K, V>,
1286 fn((SafeHash, K, V)) -> (K, V),
1290 /// HashMap keys iterator
1292 pub struct Keys<'a, K: 'a, V: 'a> {
1293 inner: Map<(&'a K, &'a V), &'a K, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
1296 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1297 impl<'a, K, V> Clone for Keys<'a, K, V> {
1298 fn clone(&self) -> Keys<'a, K, V> {
1300 inner: self.inner.clone()
1305 /// HashMap values iterator
1307 pub struct Values<'a, K: 'a, V: 'a> {
1308 inner: Map<(&'a K, &'a V), &'a V, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
1311 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1312 impl<'a, K, V> Clone for Values<'a, K, V> {
1313 fn clone(&self) -> Values<'a, K, V> {
1315 inner: self.inner.clone()
1320 /// HashMap drain iterator
1321 #[unstable = "matches collection reform specification, waiting for dust to settle"]
1322 pub struct Drain<'a, K: 'a, V: 'a> {
1326 table::Drain<'a, K, V>,
1327 fn((SafeHash, K, V)) -> (K, V),
1331 /// A view into a single occupied location in a HashMap
1332 #[unstable = "precise API still being fleshed out"]
1333 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1334 elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
1337 /// A view into a single empty location in a HashMap
1338 #[unstable = "precise API still being fleshed out"]
1339 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1342 elem: VacantEntryState<K, V, &'a mut RawTable<K, V>>,
1345 /// A view into a single location in a map, which may be vacant or occupied
1346 #[unstable = "precise API still being fleshed out"]
1347 pub enum Entry<'a, K: 'a, V: 'a> {
1348 /// An occupied Entry
1349 Occupied(OccupiedEntry<'a, K, V>),
1351 Vacant(VacantEntry<'a, K, V>),
1354 /// Possible states of a VacantEntry
1355 enum VacantEntryState<K, V, M> {
1356 /// The index is occupied, but the key to insert has precedence,
1357 /// and will kick the current one out on insertion
1358 NeqElem(FullBucket<K, V, M>, uint),
1359 /// The index is genuinely vacant
1360 NoElem(EmptyBucket<K, V, M>),
1364 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1365 type Item = (&'a K, &'a V);
1367 #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1368 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1372 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1373 type Item = (&'a K, &'a mut V);
1375 #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1376 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1380 impl<K, V> Iterator for IntoIter<K, V> {
1383 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1384 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1388 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1391 #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1392 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1396 impl<'a, K, V> Iterator for Values<'a, K, V> {
1399 #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1400 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1404 impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
1408 fn next(&mut self) -> Option<(K, V)> {
1412 fn size_hint(&self) -> (uint, Option<uint>) {
1413 self.inner.size_hint()
1417 #[unstable = "matches collection reform v2 specification, waiting for dust to settle"]
1418 impl<'a, K, V> Entry<'a, K, V> {
1419 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant
1420 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1422 Occupied(entry) => Ok(entry.into_mut()),
1423 Vacant(entry) => Err(entry),
1428 #[unstable = "matches collection reform v2 specification, waiting for dust to settle"]
1429 impl<'a, K, V> OccupiedEntry<'a, K, V> {
1430 /// Gets a reference to the value in the entry
1431 pub fn get(&self) -> &V {
1435 /// Gets a mutable reference to the value in the entry
1436 pub fn get_mut(&mut self) -> &mut V {
1437 self.elem.read_mut().1
1440 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
1441 /// with a lifetime bound to the map itself
1442 pub fn into_mut(self) -> &'a mut V {
1443 self.elem.into_mut_refs().1
1446 /// Sets the value of the entry, and returns the entry's old value
1447 pub fn insert(&mut self, mut value: V) -> V {
1448 let old_value = self.get_mut();
1449 mem::swap(&mut value, old_value);
1453 /// Takes the value out of the entry, and returns it
1454 pub fn remove(self) -> V {
1455 pop_internal(self.elem).1
1459 #[unstable = "matches collection reform v2 specification, waiting for dust to settle"]
1460 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
1461 /// Sets the value of the entry with the VacantEntry's key,
1462 /// and returns a mutable reference to it
1463 pub fn insert(self, value: V) -> &'a mut V {
1465 NeqElem(bucket, ib) => {
1466 robin_hood(bucket, ib, self.hash, self.key, value)
1469 bucket.put(self.hash, self.key, value).into_mut_refs().1
1477 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> FromIterator<(K, V)> for HashMap<K, V, H> {
1478 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> HashMap<K, V, H> {
1479 let lower = iter.size_hint().0;
1480 let mut map = HashMap::with_capacity_and_hasher(lower, Default::default());
1488 impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> Extend<(K, V)> for HashMap<K, V, H> {
1489 fn extend<T: Iterator<Item=(K, V)>>(&mut self, mut iter: T) {
1490 for (k, v) in iter {
1501 use super::Entry::{Occupied, Vacant};
1502 use iter::{range_inclusive, range_step_inclusive, repeat};
1504 use rand::{weak_rng, Rng};
1507 fn test_create_capacity_zero() {
1508 let mut m = HashMap::with_capacity(0);
1510 assert!(m.insert(1i, 1i).is_none());
1512 assert!(m.contains_key(&1));
1513 assert!(!m.contains_key(&0));
1518 let mut m = HashMap::new();
1519 assert_eq!(m.len(), 0);
1520 assert!(m.insert(1i, 2i).is_none());
1521 assert_eq!(m.len(), 1);
1522 assert!(m.insert(2i, 4i).is_none());
1523 assert_eq!(m.len(), 2);
1524 assert_eq!(*m.get(&1).unwrap(), 2);
1525 assert_eq!(*m.get(&2).unwrap(), 4);
1528 thread_local! { static DROP_VECTOR: RefCell<Vec<int>> = RefCell::new(Vec::new()) }
1530 #[derive(Hash, PartialEq, Eq)]
1536 fn new(k: uint) -> Dropable {
1537 DROP_VECTOR.with(|slot| {
1538 slot.borrow_mut()[k] += 1;
1545 impl Drop for Dropable {
1546 fn drop(&mut self) {
1547 DROP_VECTOR.with(|slot| {
1548 slot.borrow_mut()[self.k] -= 1;
1553 impl Clone for Dropable {
1554 fn clone(&self) -> Dropable {
1555 Dropable::new(self.k)
1561 DROP_VECTOR.with(|slot| {
1562 *slot.borrow_mut() = repeat(0i).take(200).collect();
1566 let mut m = HashMap::new();
1568 DROP_VECTOR.with(|v| {
1569 for i in range(0u, 200) {
1570 assert_eq!(v.borrow()[i], 0);
1574 for i in range(0u, 100) {
1575 let d1 = Dropable::new(i);
1576 let d2 = Dropable::new(i+100);
1580 DROP_VECTOR.with(|v| {
1581 for i in range(0u, 200) {
1582 assert_eq!(v.borrow()[i], 1);
1586 for i in range(0u, 50) {
1587 let k = Dropable::new(i);
1588 let v = m.remove(&k);
1590 assert!(v.is_some());
1592 DROP_VECTOR.with(|v| {
1593 assert_eq!(v.borrow()[i], 1);
1594 assert_eq!(v.borrow()[i+100], 1);
1598 DROP_VECTOR.with(|v| {
1599 for i in range(0u, 50) {
1600 assert_eq!(v.borrow()[i], 0);
1601 assert_eq!(v.borrow()[i+100], 0);
1604 for i in range(50u, 100) {
1605 assert_eq!(v.borrow()[i], 1);
1606 assert_eq!(v.borrow()[i+100], 1);
1611 DROP_VECTOR.with(|v| {
1612 for i in range(0u, 200) {
1613 assert_eq!(v.borrow()[i], 0);
1619 fn test_move_iter_drops() {
1620 DROP_VECTOR.with(|v| {
1621 *v.borrow_mut() = repeat(0).take(200).collect();
1625 let mut hm = HashMap::new();
1627 DROP_VECTOR.with(|v| {
1628 for i in range(0u, 200) {
1629 assert_eq!(v.borrow()[i], 0);
1633 for i in range(0u, 100) {
1634 let d1 = Dropable::new(i);
1635 let d2 = Dropable::new(i+100);
1639 DROP_VECTOR.with(|v| {
1640 for i in range(0u, 200) {
1641 assert_eq!(v.borrow()[i], 1);
1648 // By the way, ensure that cloning doesn't screw up the dropping.
1652 let mut half = hm.into_iter().take(50);
1654 DROP_VECTOR.with(|v| {
1655 for i in range(0u, 200) {
1656 assert_eq!(v.borrow()[i], 1);
1662 DROP_VECTOR.with(|v| {
1663 let nk = range(0u, 100).filter(|&i| {
1667 let nv = range(0u, 100).filter(|&i| {
1668 v.borrow()[i+100] == 1
1676 DROP_VECTOR.with(|v| {
1677 for i in range(0u, 200) {
1678 assert_eq!(v.borrow()[i], 0);
1684 fn test_empty_pop() {
1685 let mut m: HashMap<int, bool> = HashMap::new();
1686 assert_eq!(m.remove(&0), None);
1690 fn test_lots_of_insertions() {
1691 let mut m = HashMap::new();
1693 // Try this a few times to make sure we never screw up the hashmap's
1695 for _ in range(0i, 10) {
1696 assert!(m.is_empty());
1698 for i in range_inclusive(1i, 1000) {
1699 assert!(m.insert(i, i).is_none());
1701 for j in range_inclusive(1, i) {
1703 assert_eq!(r, Some(&j));
1706 for j in range_inclusive(i+1, 1000) {
1708 assert_eq!(r, None);
1712 for i in range_inclusive(1001i, 2000) {
1713 assert!(!m.contains_key(&i));
1717 for i in range_inclusive(1i, 1000) {
1718 assert!(m.remove(&i).is_some());
1720 for j in range_inclusive(1, i) {
1721 assert!(!m.contains_key(&j));
1724 for j in range_inclusive(i+1, 1000) {
1725 assert!(m.contains_key(&j));
1729 for i in range_inclusive(1i, 1000) {
1730 assert!(!m.contains_key(&i));
1733 for i in range_inclusive(1i, 1000) {
1734 assert!(m.insert(i, i).is_none());
1738 for i in range_step_inclusive(1000i, 1, -1) {
1739 assert!(m.remove(&i).is_some());
1741 for j in range_inclusive(i, 1000) {
1742 assert!(!m.contains_key(&j));
1745 for j in range_inclusive(1, i-1) {
1746 assert!(m.contains_key(&j));
1753 fn test_find_mut() {
1754 let mut m = HashMap::new();
1755 assert!(m.insert(1i, 12i).is_none());
1756 assert!(m.insert(2i, 8i).is_none());
1757 assert!(m.insert(5i, 14i).is_none());
1759 match m.get_mut(&5) {
1760 None => panic!(), Some(x) => *x = new
1762 assert_eq!(m.get(&5), Some(&new));
1766 fn test_insert_overwrite() {
1767 let mut m = HashMap::new();
1768 assert!(m.insert(1i, 2i).is_none());
1769 assert_eq!(*m.get(&1).unwrap(), 2);
1770 assert!(!m.insert(1i, 3i).is_none());
1771 assert_eq!(*m.get(&1).unwrap(), 3);
1775 fn test_insert_conflicts() {
1776 let mut m = HashMap::with_capacity(4);
1777 assert!(m.insert(1i, 2i).is_none());
1778 assert!(m.insert(5i, 3i).is_none());
1779 assert!(m.insert(9i, 4i).is_none());
1780 assert_eq!(*m.get(&9).unwrap(), 4);
1781 assert_eq!(*m.get(&5).unwrap(), 3);
1782 assert_eq!(*m.get(&1).unwrap(), 2);
1786 fn test_conflict_remove() {
1787 let mut m = HashMap::with_capacity(4);
1788 assert!(m.insert(1i, 2i).is_none());
1789 assert_eq!(*m.get(&1).unwrap(), 2);
1790 assert!(m.insert(5, 3).is_none());
1791 assert_eq!(*m.get(&1).unwrap(), 2);
1792 assert_eq!(*m.get(&5).unwrap(), 3);
1793 assert!(m.insert(9, 4).is_none());
1794 assert_eq!(*m.get(&1).unwrap(), 2);
1795 assert_eq!(*m.get(&5).unwrap(), 3);
1796 assert_eq!(*m.get(&9).unwrap(), 4);
1797 assert!(m.remove(&1).is_some());
1798 assert_eq!(*m.get(&9).unwrap(), 4);
1799 assert_eq!(*m.get(&5).unwrap(), 3);
1803 fn test_is_empty() {
1804 let mut m = HashMap::with_capacity(4);
1805 assert!(m.insert(1i, 2i).is_none());
1806 assert!(!m.is_empty());
1807 assert!(m.remove(&1).is_some());
1808 assert!(m.is_empty());
1813 let mut m = HashMap::new();
1815 assert_eq!(m.remove(&1), Some(2));
1816 assert_eq!(m.remove(&1), None);
1821 let mut m = HashMap::with_capacity(4);
1822 for i in range(0u, 32) {
1823 assert!(m.insert(i, i*2).is_none());
1825 assert_eq!(m.len(), 32);
1827 let mut observed: u32 = 0;
1829 for (k, v) in m.iter() {
1830 assert_eq!(*v, *k * 2);
1831 observed |= 1 << *k;
1833 assert_eq!(observed, 0xFFFF_FFFF);
1838 let vec = vec![(1i, 'a'), (2i, 'b'), (3i, 'c')];
1839 let map = vec.into_iter().collect::<HashMap<int, char>>();
1840 let keys = map.keys().map(|&k| k).collect::<Vec<int>>();
1841 assert_eq!(keys.len(), 3);
1842 assert!(keys.contains(&1));
1843 assert!(keys.contains(&2));
1844 assert!(keys.contains(&3));
1849 let vec = vec![(1i, 'a'), (2i, 'b'), (3i, 'c')];
1850 let map = vec.into_iter().collect::<HashMap<int, char>>();
1851 let values = map.values().map(|&v| v).collect::<Vec<char>>();
1852 assert_eq!(values.len(), 3);
1853 assert!(values.contains(&'a'));
1854 assert!(values.contains(&'b'));
1855 assert!(values.contains(&'c'));
1860 let mut m = HashMap::new();
1861 assert!(m.get(&1i).is_none());
1865 Some(v) => assert_eq!(*v, 2)
1871 let mut m1 = HashMap::new();
1876 let mut m2 = HashMap::new();
1889 let mut map: HashMap<int, int> = HashMap::new();
1890 let empty: HashMap<int, int> = HashMap::new();
1895 let map_str = format!("{:?}", map);
1897 assert!(map_str == "HashMap {1i: 2i, 3i: 4i}" ||
1898 map_str == "HashMap {3i: 4i, 1i: 2i}");
1899 assert_eq!(format!("{:?}", empty), "HashMap {}");
1904 let mut m = HashMap::new();
1906 assert_eq!(m.len(), 0);
1907 assert!(m.is_empty());
1910 let old_cap = m.table.capacity();
1911 while old_cap == m.table.capacity() {
1916 assert_eq!(m.len(), i);
1917 assert!(!m.is_empty());
1921 fn test_behavior_resize_policy() {
1922 let mut m = HashMap::new();
1924 assert_eq!(m.len(), 0);
1925 assert_eq!(m.table.capacity(), 0);
1926 assert!(m.is_empty());
1930 assert!(m.is_empty());
1931 let initial_cap = m.table.capacity();
1932 m.reserve(initial_cap);
1933 let cap = m.table.capacity();
1935 assert_eq!(cap, initial_cap * 2);
1938 for _ in range(0, cap * 3 / 4) {
1942 // three quarters full
1944 assert_eq!(m.len(), i);
1945 assert_eq!(m.table.capacity(), cap);
1947 for _ in range(0, cap / 4) {
1953 let new_cap = m.table.capacity();
1954 assert_eq!(new_cap, cap * 2);
1956 for _ in range(0, cap / 2 - 1) {
1959 assert_eq!(m.table.capacity(), new_cap);
1961 // A little more than one quarter full.
1963 assert_eq!(m.table.capacity(), cap);
1964 // again, a little more than half full
1965 for _ in range(0, cap / 2 - 1) {
1971 assert_eq!(m.len(), i);
1972 assert!(!m.is_empty());
1973 assert_eq!(m.table.capacity(), initial_cap);
1977 fn test_reserve_shrink_to_fit() {
1978 let mut m = HashMap::new();
1981 assert!(m.capacity() >= m.len());
1982 for i in range(0, 128) {
1987 let usable_cap = m.capacity();
1988 for i in range(128, 128+256) {
1990 assert_eq!(m.capacity(), usable_cap);
1993 for i in range(100, 128+256) {
1994 assert_eq!(m.remove(&i), Some(i));
1998 assert_eq!(m.len(), 100);
1999 assert!(!m.is_empty());
2000 assert!(m.capacity() >= m.len());
2002 for i in range(0, 100) {
2003 assert_eq!(m.remove(&i), Some(i));
2008 assert_eq!(m.len(), 1);
2009 assert!(m.capacity() >= m.len());
2010 assert_eq!(m.remove(&0), Some(0));
2014 fn test_find_equiv() {
2015 let mut m = HashMap::new();
2017 let (foo, bar, baz) = (1i,2i,3i);
2018 m.insert("foo".to_string(), foo);
2019 m.insert("bar".to_string(), bar);
2020 m.insert("baz".to_string(), baz);
2023 assert_eq!(m.get("foo"), Some(&foo));
2024 assert_eq!(m.get("bar"), Some(&bar));
2025 assert_eq!(m.get("baz"), Some(&baz));
2027 assert_eq!(m.get("qux"), None);
2031 fn test_from_iter() {
2032 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2034 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2036 for &(k, v) in xs.iter() {
2037 assert_eq!(map.get(&k), Some(&v));
2042 fn test_size_hint() {
2043 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2045 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2047 let mut iter = map.iter();
2049 for _ in iter.by_ref().take(3) {}
2051 assert_eq!(iter.size_hint(), (3, Some(3)));
2055 fn test_mut_size_hint() {
2056 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2058 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2060 let mut iter = map.iter_mut();
2062 for _ in iter.by_ref().take(3) {}
2064 assert_eq!(iter.size_hint(), (3, Some(3)));
2069 let mut map: HashMap<int, int> = HashMap::new();
2075 assert_eq!(map[2], 1);
2080 fn test_index_nonexistent() {
2081 let mut map: HashMap<int, int> = HashMap::new();
2092 let xs = [(1i, 10i), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
2094 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2096 // Existing key (insert)
2097 match map.entry(1) {
2098 Vacant(_) => unreachable!(),
2099 Occupied(mut view) => {
2100 assert_eq!(view.get(), &10);
2101 assert_eq!(view.insert(100), 10);
2104 assert_eq!(map.get(&1).unwrap(), &100);
2105 assert_eq!(map.len(), 6);
2108 // Existing key (update)
2109 match map.entry(2) {
2110 Vacant(_) => unreachable!(),
2111 Occupied(mut view) => {
2112 let v = view.get_mut();
2113 let new_v = (*v) * 10;
2117 assert_eq!(map.get(&2).unwrap(), &200);
2118 assert_eq!(map.len(), 6);
2120 // Existing key (take)
2121 match map.entry(3) {
2122 Vacant(_) => unreachable!(),
2124 assert_eq!(view.remove(), 30);
2127 assert_eq!(map.get(&3), None);
2128 assert_eq!(map.len(), 5);
2131 // Inexistent key (insert)
2132 match map.entry(10) {
2133 Occupied(_) => unreachable!(),
2135 assert_eq!(*view.insert(1000), 1000);
2138 assert_eq!(map.get(&10).unwrap(), &1000);
2139 assert_eq!(map.len(), 6);
2143 fn test_entry_take_doesnt_corrupt() {
2145 fn check(m: &HashMap<int, ()>) {
2147 assert!(m.contains_key(k),
2148 "{} is in keys() but not in the map?", k);
2152 let mut m = HashMap::new();
2153 let mut rng = weak_rng();
2155 // Populate the map with some items.
2156 for _ in range(0u, 50) {
2157 let x = rng.gen_range(-10, 10);
2161 for i in range(0u, 1000) {
2162 let x = rng.gen_range(-10, 10);
2166 println!("{}: remove {}", i, x);