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. Intutively,
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),
442 impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
443 fn make_hash<Sized? X: Hash<S>>(&self, x: &X) -> SafeHash {
444 table::make_hash(&self.hasher, x)
447 /// Search for a key, yielding the index if it's found in the hashtable.
448 /// If you already have the hash for the key lying around, use
450 fn search<'a, Sized? Q>(&'a self, q: &Q) -> Option<FullBucketImm<'a, K, V>>
451 where Q: BorrowFrom<K> + Eq + Hash<S>
453 let hash = self.make_hash(q);
454 search_hashed(&self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
458 fn search_mut<'a, Sized? Q>(&'a mut self, q: &Q) -> Option<FullBucketMut<'a, K, V>>
459 where Q: BorrowFrom<K> + Eq + Hash<S>
461 let hash = self.make_hash(q);
462 search_hashed(&mut self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
466 // The caller should ensure that invariants by Robin Hood Hashing hold.
467 fn insert_hashed_ordered(&mut self, hash: SafeHash, k: K, v: V) {
468 let cap = self.table.capacity();
469 let mut buckets = Bucket::new(&mut self.table, hash);
470 let ib = buckets.index();
472 while buckets.index() != ib + cap {
473 // We don't need to compare hashes for value swap.
474 // Not even DIBs for Robin Hood.
475 buckets = match buckets.peek() {
477 empty.put(hash, k, v);
480 Full(b) => b.into_bucket()
484 panic!("Internal HashMap error: Out of space.");
488 impl<K: Hash + Eq, V> HashMap<K, V, RandomSipHasher> {
489 /// Create an empty HashMap.
494 /// use std::collections::HashMap;
495 /// let mut map: HashMap<&str, int> = HashMap::new();
499 pub fn new() -> HashMap<K, V, RandomSipHasher> {
500 let hasher = RandomSipHasher::new();
501 HashMap::with_hasher(hasher)
504 /// Creates an empty hash map with the given initial capacity.
509 /// use std::collections::HashMap;
510 /// let mut map: HashMap<&str, int> = HashMap::with_capacity(10);
514 pub fn with_capacity(capacity: uint) -> HashMap<K, V, RandomSipHasher> {
515 let hasher = RandomSipHasher::new();
516 HashMap::with_capacity_and_hasher(capacity, hasher)
520 impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
521 /// Creates an empty hashmap which will use the given hasher to hash keys.
523 /// The creates map has the default initial capacity.
528 /// use std::collections::HashMap;
529 /// use std::hash::sip::SipHasher;
531 /// let h = SipHasher::new();
532 /// let mut map = HashMap::with_hasher(h);
533 /// map.insert(1i, 2u);
536 #[unstable = "hasher stuff is unclear"]
537 pub fn with_hasher(hasher: H) -> HashMap<K, V, H> {
540 resize_policy: DefaultResizePolicy::new(),
541 table: RawTable::new(0),
545 /// Create an empty HashMap with space for at least `capacity`
546 /// elements, using `hasher` to hash the keys.
548 /// Warning: `hasher` is normally randomly generated, and
549 /// is designed to allow HashMaps to be resistant to attacks that
550 /// cause many collisions and very poor performance. Setting it
551 /// manually using this function can expose a DoS attack vector.
556 /// use std::collections::HashMap;
557 /// use std::hash::sip::SipHasher;
559 /// let h = SipHasher::new();
560 /// let mut map = HashMap::with_capacity_and_hasher(10, h);
561 /// map.insert(1i, 2u);
564 #[unstable = "hasher stuff is unclear"]
565 pub fn with_capacity_and_hasher(capacity: uint, hasher: H) -> HashMap<K, V, H> {
566 let resize_policy = DefaultResizePolicy::new();
567 let min_cap = max(INITIAL_CAPACITY, resize_policy.min_capacity(capacity));
568 let internal_cap = min_cap.checked_next_power_of_two().expect("capacity overflow");
569 assert!(internal_cap >= capacity, "capacity overflow");
572 resize_policy: resize_policy,
573 table: RawTable::new(internal_cap),
577 /// Returns the number of elements the map can hold without reallocating.
582 /// use std::collections::HashMap;
583 /// let map: HashMap<int, int> = HashMap::with_capacity(100);
584 /// assert!(map.capacity() >= 100);
588 pub fn capacity(&self) -> uint {
589 self.resize_policy.usable_capacity(self.table.capacity())
592 /// Reserves capacity for at least `additional` more elements to be inserted
593 /// in the `HashMap`. The collection may reserve more space to avoid
594 /// frequent reallocations.
598 /// Panics if the new allocation size overflows `uint`.
603 /// use std::collections::HashMap;
604 /// let mut map: HashMap<&str, int> = HashMap::new();
608 pub fn reserve(&mut self, additional: uint) {
609 let new_size = self.len().checked_add(additional).expect("capacity overflow");
610 let min_cap = self.resize_policy.min_capacity(new_size);
612 // An invalid value shouldn't make us run out of space. This includes
613 // an overflow check.
614 assert!(new_size <= min_cap);
616 if self.table.capacity() < min_cap {
617 let new_capacity = max(min_cap.next_power_of_two(), INITIAL_CAPACITY);
618 self.resize(new_capacity);
622 /// Resizes the internal vectors to a new capacity. It's your responsibility to:
623 /// 1) Make sure the new capacity is enough for all the elements, accounting
624 /// for the load factor.
625 /// 2) Ensure new_capacity is a power of two or zero.
626 fn resize(&mut self, new_capacity: uint) {
627 assert!(self.table.size() <= new_capacity);
628 assert!(new_capacity.is_power_of_two() || new_capacity == 0);
630 let mut old_table = replace(&mut self.table, RawTable::new(new_capacity));
631 let old_size = old_table.size();
633 if old_table.capacity() == 0 || old_table.size() == 0 {
638 // Specialization of the other branch.
639 let mut bucket = Bucket::first(&mut old_table);
641 // "So a few of the first shall be last: for many be called,
644 // We'll most likely encounter a few buckets at the beginning that
645 // have their initial buckets near the end of the table. They were
646 // placed at the beginning as the probe wrapped around the table
647 // during insertion. We must skip forward to a bucket that won't
648 // get reinserted too early and won't unfairly steal others spot.
649 // This eliminates the need for robin hood.
651 bucket = match bucket.peek() {
653 if full.distance() == 0 {
654 // This bucket occupies its ideal spot.
655 // It indicates the start of another "cluster".
656 bucket = full.into_bucket();
659 // Leaving this bucket in the last cluster for later.
663 // Encountered a hole between clusters.
670 // This is how the buckets might be laid out in memory:
671 // ($ marks an initialized bucket)
673 // |$$$_$$$$$$_$$$$$|
675 // But we've skipped the entire initial cluster of buckets
676 // and will continue iteration in this order:
679 // ^ wrap around once end is reached
682 // ^ exit once table.size == 0
684 bucket = match bucket.peek() {
686 let h = bucket.hash();
687 let (b, k, v) = bucket.take();
688 self.insert_hashed_ordered(h, k, v);
690 let t = b.table(); // FIXME "lifetime too short".
691 if t.size() == 0 { break }
695 Empty(b) => b.into_bucket()
700 assert_eq!(self.table.size(), old_size);
703 /// Shrinks the capacity of the map as much as possible. It will drop
704 /// down as much as possible while maintaining the internal rules
705 /// and possibly leaving some space in accordance with the resize policy.
710 /// use std::collections::HashMap;
712 /// let mut map: HashMap<int, int> = HashMap::with_capacity(100);
713 /// map.insert(1, 2);
714 /// map.insert(3, 4);
715 /// assert!(map.capacity() >= 100);
716 /// map.shrink_to_fit();
717 /// assert!(map.capacity() >= 2);
720 pub fn shrink_to_fit(&mut self) {
721 let min_capacity = self.resize_policy.min_capacity(self.len());
722 let min_capacity = max(min_capacity.next_power_of_two(), INITIAL_CAPACITY);
724 // An invalid value shouldn't make us run out of space.
725 debug_assert!(self.len() <= min_capacity);
727 if self.table.capacity() != min_capacity {
728 let old_table = replace(&mut self.table, RawTable::new(min_capacity));
729 let old_size = old_table.size();
731 // Shrink the table. Naive algorithm for resizing:
732 for (h, k, v) in old_table.into_iter() {
733 self.insert_hashed_nocheck(h, k, v);
736 debug_assert_eq!(self.table.size(), old_size);
740 /// Insert a pre-hashed key-value pair, without first checking
741 /// that there's enough room in the buckets. Returns a reference to the
742 /// newly insert value.
744 /// If the key already exists, the hashtable will be returned untouched
745 /// and a reference to the existing element will be returned.
746 fn insert_hashed_nocheck(&mut self, hash: SafeHash, k: K, v: V) -> &mut V {
747 self.insert_or_replace_with(hash, k, v, |_, _, _| ())
750 fn insert_or_replace_with<'a, F>(&'a mut self,
754 mut found_existing: F)
756 F: FnMut(&mut K, &mut V, V),
758 // Worst case, we'll find one empty bucket among `size + 1` buckets.
759 let size = self.table.size();
760 let mut probe = Bucket::new(&mut self.table, hash);
761 let ib = probe.index();
764 let mut bucket = match probe.peek() {
767 return bucket.put(hash, k, v).into_mut_refs().1;
769 Full(bucket) => bucket
773 if bucket.hash() == hash {
775 if k == *bucket.read_mut().0 {
776 let (bucket_k, bucket_v) = bucket.into_mut_refs();
777 debug_assert!(k == *bucket_k);
778 // Key already exists. Get its reference.
779 found_existing(bucket_k, bucket_v, v);
784 let robin_ib = bucket.index() as int - bucket.distance() as int;
786 if (ib as int) < robin_ib {
787 // Found a luckier bucket than me. Better steal his spot.
788 return robin_hood(bucket, robin_ib as uint, hash, k, v);
791 probe = bucket.next();
792 assert!(probe.index() != ib + size + 1);
796 /// An iterator visiting all keys in arbitrary order.
797 /// Iterator element type is `&'a K`.
802 /// use std::collections::HashMap;
804 /// let mut map = HashMap::new();
805 /// map.insert("a", 1i);
806 /// map.insert("b", 2);
807 /// map.insert("c", 3);
809 /// for key in map.keys() {
810 /// println!("{}", key);
814 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
815 fn first<A, B>((a, _): (A, B)) -> A { a }
816 let first: fn((&'a K,&'a V)) -> &'a K = first; // coerce to fn ptr
818 Keys { inner: self.iter().map(first) }
821 /// An iterator visiting all values in arbitrary order.
822 /// Iterator element type is `&'a V`.
827 /// use std::collections::HashMap;
829 /// let mut map = HashMap::new();
830 /// map.insert("a", 1i);
831 /// map.insert("b", 2);
832 /// map.insert("c", 3);
834 /// for key in map.values() {
835 /// println!("{}", key);
839 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
840 fn second<A, B>((_, b): (A, B)) -> B { b }
841 let second: fn((&'a K,&'a V)) -> &'a V = second; // coerce to fn ptr
843 Values { inner: self.iter().map(second) }
846 /// An iterator visiting all key-value pairs in arbitrary order.
847 /// Iterator element type is `(&'a K, &'a V)`.
852 /// use std::collections::HashMap;
854 /// let mut map = HashMap::new();
855 /// map.insert("a", 1i);
856 /// map.insert("b", 2);
857 /// map.insert("c", 3);
859 /// for (key, val) in map.iter() {
860 /// println!("key: {} val: {}", key, val);
864 pub fn iter(&self) -> Iter<K, V> {
865 Iter { inner: self.table.iter() }
868 /// An iterator visiting all key-value pairs in arbitrary order,
869 /// with mutable references to the values.
870 /// Iterator element type is `(&'a K, &'a mut V)`.
875 /// use std::collections::HashMap;
877 /// let mut map = HashMap::new();
878 /// map.insert("a", 1i);
879 /// map.insert("b", 2);
880 /// map.insert("c", 3);
882 /// // Update all values
883 /// for (_, val) in map.iter_mut() {
887 /// for (key, val) in map.iter() {
888 /// println!("key: {} val: {}", key, val);
892 pub fn iter_mut(&mut self) -> IterMut<K, V> {
893 IterMut { inner: self.table.iter_mut() }
896 /// Creates a consuming iterator, that is, one that moves each key-value
897 /// pair out of the map in arbitrary order. The map cannot be used after
903 /// use std::collections::HashMap;
905 /// let mut map = HashMap::new();
906 /// map.insert("a", 1i);
907 /// map.insert("b", 2);
908 /// map.insert("c", 3);
910 /// // Not possible with .iter()
911 /// let vec: Vec<(&str, int)> = map.into_iter().collect();
914 pub fn into_iter(self) -> IntoIter<K, V> {
915 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
916 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two;
919 inner: self.table.into_iter().map(last_two)
923 /// Gets the given key's corresponding entry in the map for in-place manipulation
924 pub fn entry<'a>(&'a mut self, key: K) -> Entry<'a, K, V> {
928 let hash = self.make_hash(&key);
929 search_entry_hashed(&mut self.table, hash, key)
932 /// Return the number of elements in the map.
937 /// use std::collections::HashMap;
939 /// let mut a = HashMap::new();
940 /// assert_eq!(a.len(), 0);
941 /// a.insert(1u, "a");
942 /// assert_eq!(a.len(), 1);
945 pub fn len(&self) -> uint { self.table.size() }
947 /// Return true if the map contains no elements.
952 /// use std::collections::HashMap;
954 /// let mut a = HashMap::new();
955 /// assert!(a.is_empty());
956 /// a.insert(1u, "a");
957 /// assert!(!a.is_empty());
961 pub fn is_empty(&self) -> bool { self.len() == 0 }
963 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
964 /// allocated memory for reuse.
969 /// use std::collections::HashMap;
971 /// let mut a = HashMap::new();
972 /// a.insert(1u, "a");
973 /// a.insert(2u, "b");
975 /// for (k, v) in a.drain().take(1) {
976 /// assert!(k == 1 || k == 2);
977 /// assert!(v == "a" || v == "b");
980 /// assert!(a.is_empty());
983 #[unstable = "matches collection reform specification, waiting for dust to settle"]
984 pub fn drain(&mut self) -> Drain<K, V> {
985 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
986 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two; // coerce to fn pointer
989 inner: self.table.drain().map(last_two),
993 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
999 /// use std::collections::HashMap;
1001 /// let mut a = HashMap::new();
1002 /// a.insert(1u, "a");
1004 /// assert!(a.is_empty());
1008 pub fn clear(&mut self) {
1012 /// Returns a reference to the value corresponding to the key.
1014 /// The key may be any borrowed form of the map's key type, but
1015 /// `Hash` and `Eq` on the borrowed form *must* match those for
1021 /// use std::collections::HashMap;
1023 /// let mut map = HashMap::new();
1024 /// map.insert(1u, "a");
1025 /// assert_eq!(map.get(&1), Some(&"a"));
1026 /// assert_eq!(map.get(&2), None);
1029 pub fn get<Sized? Q>(&self, k: &Q) -> Option<&V>
1030 where Q: Hash<S> + Eq + BorrowFrom<K>
1032 self.search(k).map(|bucket| bucket.into_refs().1)
1035 /// Returns true if the map contains a value for the specified key.
1037 /// The key may be any borrowed form of the map's key type, but
1038 /// `Hash` and `Eq` on the borrowed form *must* match those for
1044 /// use std::collections::HashMap;
1046 /// let mut map = HashMap::new();
1047 /// map.insert(1u, "a");
1048 /// assert_eq!(map.contains_key(&1), true);
1049 /// assert_eq!(map.contains_key(&2), false);
1052 pub fn contains_key<Sized? Q>(&self, k: &Q) -> bool
1053 where Q: Hash<S> + Eq + BorrowFrom<K>
1055 self.search(k).is_some()
1058 /// Returns a mutable reference to the value corresponding to the key.
1060 /// The key may be any borrowed form of the map's key type, but
1061 /// `Hash` and `Eq` on the borrowed form *must* match those for
1067 /// use std::collections::HashMap;
1069 /// let mut map = HashMap::new();
1070 /// map.insert(1u, "a");
1071 /// match map.get_mut(&1) {
1072 /// Some(x) => *x = "b",
1075 /// assert_eq!(map[1], "b");
1078 pub fn get_mut<Sized? Q>(&mut self, k: &Q) -> Option<&mut V>
1079 where Q: Hash<S> + Eq + BorrowFrom<K>
1081 self.search_mut(k).map(|bucket| bucket.into_mut_refs().1)
1084 /// Inserts a key-value pair from the map. If the key already had a value
1085 /// present in the map, that value is returned. Otherwise, `None` is returned.
1090 /// use std::collections::HashMap;
1092 /// let mut map = HashMap::new();
1093 /// assert_eq!(map.insert(37u, "a"), None);
1094 /// assert_eq!(map.is_empty(), false);
1096 /// map.insert(37, "b");
1097 /// assert_eq!(map.insert(37, "c"), Some("b"));
1098 /// assert_eq!(map[37], "c");
1101 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1102 let hash = self.make_hash(&k);
1105 let mut retval = None;
1106 self.insert_or_replace_with(hash, k, v, |_, val_ref, val| {
1107 retval = Some(replace(val_ref, val));
1112 /// Removes a key from the map, returning the value at the key if the key
1113 /// was previously in the map.
1115 /// The key may be any borrowed form of the map's key type, but
1116 /// `Hash` and `Eq` on the borrowed form *must* match those for
1122 /// use std::collections::HashMap;
1124 /// let mut map = HashMap::new();
1125 /// map.insert(1u, "a");
1126 /// assert_eq!(map.remove(&1), Some("a"));
1127 /// assert_eq!(map.remove(&1), None);
1130 pub fn remove<Sized? Q>(&mut self, k: &Q) -> Option<V>
1131 where Q: Hash<S> + Eq + BorrowFrom<K>
1133 if self.table.size() == 0 {
1137 self.search_mut(k).map(|bucket| pop_internal(bucket).1)
1141 fn search_entry_hashed<'a, K: Eq, V>(table: &'a mut RawTable<K,V>, hash: SafeHash, k: K)
1142 -> Entry<'a, K, V> {
1143 // Worst case, we'll find one empty bucket among `size + 1` buckets.
1144 let size = table.size();
1145 let mut probe = Bucket::new(table, hash);
1146 let ib = probe.index();
1149 let bucket = match probe.peek() {
1152 return Vacant(VacantEntry {
1155 elem: NoElem(bucket),
1158 Full(bucket) => bucket
1162 if bucket.hash() == hash {
1164 if k == *bucket.read().0 {
1165 return Occupied(OccupiedEntry{
1171 let robin_ib = bucket.index() as int - bucket.distance() as int;
1173 if (ib as int) < robin_ib {
1174 // Found a luckier bucket than me. Better steal his spot.
1175 return Vacant(VacantEntry {
1178 elem: NeqElem(bucket, robin_ib as uint),
1182 probe = bucket.next();
1183 assert!(probe.index() != ib + size + 1);
1188 impl<K: Eq + Hash<S>, V: PartialEq, S, H: Hasher<S>> PartialEq for HashMap<K, V, H> {
1189 fn eq(&self, other: &HashMap<K, V, H>) -> bool {
1190 if self.len() != other.len() { return false; }
1192 self.iter().all(|(key, value)|
1193 other.get(key).map_or(false, |v| *value == *v)
1199 impl<K: Eq + Hash<S>, V: Eq, S, H: Hasher<S>> Eq for HashMap<K, V, H> {}
1202 impl<K: Eq + Hash<S> + Show, V: Show, S, H: Hasher<S>> Show for HashMap<K, V, H> {
1203 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1204 try!(write!(f, "{{"));
1206 for (i, (k, v)) in self.iter().enumerate() {
1207 if i != 0 { try!(write!(f, ", ")); }
1208 try!(write!(f, "{}: {}", *k, *v));
1216 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> Default for HashMap<K, V, H> {
1218 fn default() -> HashMap<K, V, H> {
1219 HashMap::with_hasher(Default::default())
1223 // NOTE(stage0): remove impl after a snapshot
1226 impl<K: Hash<S> + Eq, Sized? Q, V, S, H: Hasher<S>> Index<Q, V> for HashMap<K, V, H>
1227 where Q: BorrowFrom<K> + Hash<S> + Eq
1230 fn index<'a>(&'a self, index: &Q) -> &'a V {
1231 self.get(index).expect("no entry found for key")
1235 #[cfg(not(stage0))] // NOTE(stage0): remove cfg after a snapshot
1237 impl<K: Hash<S> + Eq, Sized? Q, V, S, H: Hasher<S>> Index<Q> for HashMap<K, V, H>
1238 where Q: BorrowFrom<K> + Hash<S> + Eq
1243 fn index<'a>(&'a self, index: &Q) -> &'a V {
1244 self.get(index).expect("no entry found for key")
1248 // NOTE(stage0): remove impl after a snapshot
1251 impl<K: Hash<S> + Eq, Sized? Q, V, S, H: Hasher<S>> IndexMut<Q, V> for HashMap<K, V, H>
1252 where Q: BorrowFrom<K> + Hash<S> + Eq
1255 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1256 self.get_mut(index).expect("no entry found for key")
1260 #[cfg(not(stage0))] // NOTE(stage0): remove cfg after a snapshot
1262 impl<K: Hash<S> + Eq, Sized? Q, V, S, H: Hasher<S>> IndexMut<Q> for HashMap<K, V, H>
1263 where Q: BorrowFrom<K> + Hash<S> + Eq
1268 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1269 self.get_mut(index).expect("no entry found for key")
1273 /// HashMap iterator
1275 pub struct Iter<'a, K: 'a, V: 'a> {
1276 inner: table::Iter<'a, K, V>
1279 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1280 impl<'a, K, V> Clone for Iter<'a, K, V> {
1281 fn clone(&self) -> Iter<'a, K, V> {
1283 inner: self.inner.clone()
1288 /// HashMap mutable values iterator
1290 pub struct IterMut<'a, K: 'a, V: 'a> {
1291 inner: table::IterMut<'a, K, V>
1294 /// HashMap move iterator
1296 pub struct IntoIter<K, V> {
1300 table::IntoIter<K, V>,
1301 fn((SafeHash, K, V)) -> (K, V),
1305 /// HashMap keys iterator
1307 pub struct Keys<'a, K: 'a, V: 'a> {
1308 inner: Map<(&'a K, &'a V), &'a K, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
1311 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1312 impl<'a, K, V> Clone for Keys<'a, K, V> {
1313 fn clone(&self) -> Keys<'a, K, V> {
1315 inner: self.inner.clone()
1320 /// HashMap values iterator
1322 pub struct Values<'a, K: 'a, V: 'a> {
1323 inner: Map<(&'a K, &'a V), &'a V, Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
1326 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1327 impl<'a, K, V> Clone for Values<'a, K, V> {
1328 fn clone(&self) -> Values<'a, K, V> {
1330 inner: self.inner.clone()
1335 /// HashMap drain iterator
1336 #[unstable = "matches collection reform specification, waiting for dust to settle"]
1337 pub struct Drain<'a, K: 'a, V: 'a> {
1341 table::Drain<'a, K, V>,
1342 fn((SafeHash, K, V)) -> (K, V),
1346 /// A view into a single occupied location in a HashMap
1347 pub struct OccupiedEntry<'a, K:'a, V:'a> {
1348 elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
1351 /// A view into a single empty location in a HashMap
1352 pub struct VacantEntry<'a, K:'a, V:'a> {
1355 elem: VacantEntryState<K,V, &'a mut RawTable<K, V>>,
1358 /// A view into a single location in a map, which may be vacant or occupied
1359 pub enum Entry<'a, K:'a, V:'a> {
1360 /// An occupied Entry
1361 Occupied(OccupiedEntry<'a, K, V>),
1363 Vacant(VacantEntry<'a, K, V>),
1366 /// Possible states of a VacantEntry
1367 enum VacantEntryState<K, V, M> {
1368 /// The index is occupied, but the key to insert has precedence,
1369 /// and will kick the current one out on insertion
1370 NeqElem(FullBucket<K, V, M>, uint),
1371 /// The index is genuinely vacant
1372 NoElem(EmptyBucket<K, V, M>),
1376 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1377 type Item = (&'a K, &'a V);
1379 #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1380 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1384 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1385 type Item = (&'a K, &'a mut V);
1387 #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1388 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1392 impl<K, V> Iterator for IntoIter<K, V> {
1395 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1396 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1400 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1403 #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1404 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1408 impl<'a, K, V> Iterator for Values<'a, K, V> {
1411 #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1412 #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
1416 impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
1420 fn next(&mut self) -> Option<(K, V)> {
1424 fn size_hint(&self) -> (uint, Option<uint>) {
1425 self.inner.size_hint()
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 set(&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 take(self) -> V {
1455 pop_internal(self.elem).1
1459 impl<'a, K, V> VacantEntry<'a, K, V> {
1460 /// Sets the value of the entry with the VacantEntry's key,
1461 /// and returns a mutable reference to it
1462 pub fn set(self, value: V) -> &'a mut V {
1464 NeqElem(bucket, ib) => {
1465 robin_hood(bucket, ib, self.hash, self.key, value)
1468 bucket.put(self.hash, self.key, value).into_mut_refs().1
1475 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> FromIterator<(K, V)> for HashMap<K, V, H> {
1476 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> HashMap<K, V, H> {
1477 let lower = iter.size_hint().0;
1478 let mut map = HashMap::with_capacity_and_hasher(lower, Default::default());
1485 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> Extend<(K, V)> for HashMap<K, V, H> {
1486 fn extend<T: Iterator<Item=(K, V)>>(&mut self, mut iter: T) {
1487 for (k, v) in iter {
1498 use super::Entry::{Occupied, Vacant};
1499 use iter::{range_inclusive, range_step_inclusive, repeat};
1501 use rand::{weak_rng, Rng};
1504 fn test_create_capacity_zero() {
1505 let mut m = HashMap::with_capacity(0);
1507 assert!(m.insert(1i, 1i).is_none());
1509 assert!(m.contains_key(&1));
1510 assert!(!m.contains_key(&0));
1515 let mut m = HashMap::new();
1516 assert_eq!(m.len(), 0);
1517 assert!(m.insert(1i, 2i).is_none());
1518 assert_eq!(m.len(), 1);
1519 assert!(m.insert(2i, 4i).is_none());
1520 assert_eq!(m.len(), 2);
1521 assert_eq!(*m.get(&1).unwrap(), 2);
1522 assert_eq!(*m.get(&2).unwrap(), 4);
1525 thread_local! { static DROP_VECTOR: RefCell<Vec<int>> = RefCell::new(Vec::new()) }
1527 #[derive(Hash, PartialEq, Eq)]
1533 fn new(k: uint) -> Dropable {
1534 DROP_VECTOR.with(|slot| {
1535 slot.borrow_mut()[k] += 1;
1542 impl Drop for Dropable {
1543 fn drop(&mut self) {
1544 DROP_VECTOR.with(|slot| {
1545 slot.borrow_mut()[self.k] -= 1;
1550 impl Clone for Dropable {
1551 fn clone(&self) -> Dropable {
1552 Dropable::new(self.k)
1558 DROP_VECTOR.with(|slot| {
1559 *slot.borrow_mut() = repeat(0i).take(200).collect();
1563 let mut m = HashMap::new();
1565 DROP_VECTOR.with(|v| {
1566 for i in range(0u, 200) {
1567 assert_eq!(v.borrow()[i], 0);
1571 for i in range(0u, 100) {
1572 let d1 = Dropable::new(i);
1573 let d2 = Dropable::new(i+100);
1577 DROP_VECTOR.with(|v| {
1578 for i in range(0u, 200) {
1579 assert_eq!(v.borrow()[i], 1);
1583 for i in range(0u, 50) {
1584 let k = Dropable::new(i);
1585 let v = m.remove(&k);
1587 assert!(v.is_some());
1589 DROP_VECTOR.with(|v| {
1590 assert_eq!(v.borrow()[i], 1);
1591 assert_eq!(v.borrow()[i+100], 1);
1595 DROP_VECTOR.with(|v| {
1596 for i in range(0u, 50) {
1597 assert_eq!(v.borrow()[i], 0);
1598 assert_eq!(v.borrow()[i+100], 0);
1601 for i in range(50u, 100) {
1602 assert_eq!(v.borrow()[i], 1);
1603 assert_eq!(v.borrow()[i+100], 1);
1608 DROP_VECTOR.with(|v| {
1609 for i in range(0u, 200) {
1610 assert_eq!(v.borrow()[i], 0);
1616 fn test_move_iter_drops() {
1617 DROP_VECTOR.with(|v| {
1618 *v.borrow_mut() = repeat(0).take(200).collect();
1622 let mut hm = HashMap::new();
1624 DROP_VECTOR.with(|v| {
1625 for i in range(0u, 200) {
1626 assert_eq!(v.borrow()[i], 0);
1630 for i in range(0u, 100) {
1631 let d1 = Dropable::new(i);
1632 let d2 = Dropable::new(i+100);
1636 DROP_VECTOR.with(|v| {
1637 for i in range(0u, 200) {
1638 assert_eq!(v.borrow()[i], 1);
1645 // By the way, ensure that cloning doesn't screw up the dropping.
1649 let mut half = hm.into_iter().take(50);
1651 DROP_VECTOR.with(|v| {
1652 for i in range(0u, 200) {
1653 assert_eq!(v.borrow()[i], 1);
1659 DROP_VECTOR.with(|v| {
1660 let nk = range(0u, 100).filter(|&i| {
1664 let nv = range(0u, 100).filter(|&i| {
1665 v.borrow()[i+100] == 1
1673 DROP_VECTOR.with(|v| {
1674 for i in range(0u, 200) {
1675 assert_eq!(v.borrow()[i], 0);
1681 fn test_empty_pop() {
1682 let mut m: HashMap<int, bool> = HashMap::new();
1683 assert_eq!(m.remove(&0), None);
1687 fn test_lots_of_insertions() {
1688 let mut m = HashMap::new();
1690 // Try this a few times to make sure we never screw up the hashmap's
1692 for _ in range(0i, 10) {
1693 assert!(m.is_empty());
1695 for i in range_inclusive(1i, 1000) {
1696 assert!(m.insert(i, i).is_none());
1698 for j in range_inclusive(1, i) {
1700 assert_eq!(r, Some(&j));
1703 for j in range_inclusive(i+1, 1000) {
1705 assert_eq!(r, None);
1709 for i in range_inclusive(1001i, 2000) {
1710 assert!(!m.contains_key(&i));
1714 for i in range_inclusive(1i, 1000) {
1715 assert!(m.remove(&i).is_some());
1717 for j in range_inclusive(1, i) {
1718 assert!(!m.contains_key(&j));
1721 for j in range_inclusive(i+1, 1000) {
1722 assert!(m.contains_key(&j));
1726 for i in range_inclusive(1i, 1000) {
1727 assert!(!m.contains_key(&i));
1730 for i in range_inclusive(1i, 1000) {
1731 assert!(m.insert(i, i).is_none());
1735 for i in range_step_inclusive(1000i, 1, -1) {
1736 assert!(m.remove(&i).is_some());
1738 for j in range_inclusive(i, 1000) {
1739 assert!(!m.contains_key(&j));
1742 for j in range_inclusive(1, i-1) {
1743 assert!(m.contains_key(&j));
1750 fn test_find_mut() {
1751 let mut m = HashMap::new();
1752 assert!(m.insert(1i, 12i).is_none());
1753 assert!(m.insert(2i, 8i).is_none());
1754 assert!(m.insert(5i, 14i).is_none());
1756 match m.get_mut(&5) {
1757 None => panic!(), Some(x) => *x = new
1759 assert_eq!(m.get(&5), Some(&new));
1763 fn test_insert_overwrite() {
1764 let mut m = HashMap::new();
1765 assert!(m.insert(1i, 2i).is_none());
1766 assert_eq!(*m.get(&1).unwrap(), 2);
1767 assert!(!m.insert(1i, 3i).is_none());
1768 assert_eq!(*m.get(&1).unwrap(), 3);
1772 fn test_insert_conflicts() {
1773 let mut m = HashMap::with_capacity(4);
1774 assert!(m.insert(1i, 2i).is_none());
1775 assert!(m.insert(5i, 3i).is_none());
1776 assert!(m.insert(9i, 4i).is_none());
1777 assert_eq!(*m.get(&9).unwrap(), 4);
1778 assert_eq!(*m.get(&5).unwrap(), 3);
1779 assert_eq!(*m.get(&1).unwrap(), 2);
1783 fn test_conflict_remove() {
1784 let mut m = HashMap::with_capacity(4);
1785 assert!(m.insert(1i, 2i).is_none());
1786 assert_eq!(*m.get(&1).unwrap(), 2);
1787 assert!(m.insert(5, 3).is_none());
1788 assert_eq!(*m.get(&1).unwrap(), 2);
1789 assert_eq!(*m.get(&5).unwrap(), 3);
1790 assert!(m.insert(9, 4).is_none());
1791 assert_eq!(*m.get(&1).unwrap(), 2);
1792 assert_eq!(*m.get(&5).unwrap(), 3);
1793 assert_eq!(*m.get(&9).unwrap(), 4);
1794 assert!(m.remove(&1).is_some());
1795 assert_eq!(*m.get(&9).unwrap(), 4);
1796 assert_eq!(*m.get(&5).unwrap(), 3);
1800 fn test_is_empty() {
1801 let mut m = HashMap::with_capacity(4);
1802 assert!(m.insert(1i, 2i).is_none());
1803 assert!(!m.is_empty());
1804 assert!(m.remove(&1).is_some());
1805 assert!(m.is_empty());
1810 let mut m = HashMap::new();
1812 assert_eq!(m.remove(&1), Some(2));
1813 assert_eq!(m.remove(&1), None);
1818 let mut m = HashMap::with_capacity(4);
1819 for i in range(0u, 32) {
1820 assert!(m.insert(i, i*2).is_none());
1822 assert_eq!(m.len(), 32);
1824 let mut observed: u32 = 0;
1826 for (k, v) in m.iter() {
1827 assert_eq!(*v, *k * 2);
1828 observed |= 1 << *k;
1830 assert_eq!(observed, 0xFFFF_FFFF);
1835 let vec = vec![(1i, 'a'), (2i, 'b'), (3i, 'c')];
1836 let map = vec.into_iter().collect::<HashMap<int, char>>();
1837 let keys = map.keys().map(|&k| k).collect::<Vec<int>>();
1838 assert_eq!(keys.len(), 3);
1839 assert!(keys.contains(&1));
1840 assert!(keys.contains(&2));
1841 assert!(keys.contains(&3));
1846 let vec = vec![(1i, 'a'), (2i, 'b'), (3i, 'c')];
1847 let map = vec.into_iter().collect::<HashMap<int, char>>();
1848 let values = map.values().map(|&v| v).collect::<Vec<char>>();
1849 assert_eq!(values.len(), 3);
1850 assert!(values.contains(&'a'));
1851 assert!(values.contains(&'b'));
1852 assert!(values.contains(&'c'));
1857 let mut m = HashMap::new();
1858 assert!(m.get(&1i).is_none());
1862 Some(v) => assert_eq!(*v, 2)
1868 let mut m1 = HashMap::new();
1873 let mut m2 = HashMap::new();
1886 let mut map: HashMap<int, int> = HashMap::new();
1887 let empty: HashMap<int, int> = HashMap::new();
1892 let map_str = format!("{}", map);
1894 assert!(map_str == "{1: 2, 3: 4}" || map_str == "{3: 4, 1: 2}");
1895 assert_eq!(format!("{}", empty), "{}");
1900 let mut m = HashMap::new();
1902 assert_eq!(m.len(), 0);
1903 assert!(m.is_empty());
1906 let old_cap = m.table.capacity();
1907 while old_cap == m.table.capacity() {
1912 assert_eq!(m.len(), i);
1913 assert!(!m.is_empty());
1917 fn test_behavior_resize_policy() {
1918 let mut m = HashMap::new();
1920 assert_eq!(m.len(), 0);
1921 assert_eq!(m.table.capacity(), 0);
1922 assert!(m.is_empty());
1926 assert!(m.is_empty());
1927 let initial_cap = m.table.capacity();
1928 m.reserve(initial_cap);
1929 let cap = m.table.capacity();
1931 assert_eq!(cap, initial_cap * 2);
1934 for _ in range(0, cap * 3 / 4) {
1938 // three quarters full
1940 assert_eq!(m.len(), i);
1941 assert_eq!(m.table.capacity(), cap);
1943 for _ in range(0, cap / 4) {
1949 let new_cap = m.table.capacity();
1950 assert_eq!(new_cap, cap * 2);
1952 for _ in range(0, cap / 2 - 1) {
1955 assert_eq!(m.table.capacity(), new_cap);
1957 // A little more than one quarter full.
1959 assert_eq!(m.table.capacity(), cap);
1960 // again, a little more than half full
1961 for _ in range(0, cap / 2 - 1) {
1967 assert_eq!(m.len(), i);
1968 assert!(!m.is_empty());
1969 assert_eq!(m.table.capacity(), initial_cap);
1973 fn test_reserve_shrink_to_fit() {
1974 let mut m = HashMap::new();
1977 assert!(m.capacity() >= m.len());
1978 for i in range(0, 128) {
1983 let usable_cap = m.capacity();
1984 for i in range(128, 128+256) {
1986 assert_eq!(m.capacity(), usable_cap);
1989 for i in range(100, 128+256) {
1990 assert_eq!(m.remove(&i), Some(i));
1994 assert_eq!(m.len(), 100);
1995 assert!(!m.is_empty());
1996 assert!(m.capacity() >= m.len());
1998 for i in range(0, 100) {
1999 assert_eq!(m.remove(&i), Some(i));
2004 assert_eq!(m.len(), 1);
2005 assert!(m.capacity() >= m.len());
2006 assert_eq!(m.remove(&0), Some(0));
2010 fn test_find_equiv() {
2011 let mut m = HashMap::new();
2013 let (foo, bar, baz) = (1i,2i,3i);
2014 m.insert("foo".to_string(), foo);
2015 m.insert("bar".to_string(), bar);
2016 m.insert("baz".to_string(), baz);
2019 assert_eq!(m.get("foo"), Some(&foo));
2020 assert_eq!(m.get("bar"), Some(&bar));
2021 assert_eq!(m.get("baz"), Some(&baz));
2023 assert_eq!(m.get("qux"), None);
2027 fn test_from_iter() {
2028 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2030 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2032 for &(k, v) in xs.iter() {
2033 assert_eq!(map.get(&k), Some(&v));
2038 fn test_size_hint() {
2039 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2041 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2043 let mut iter = map.iter();
2045 for _ in iter.by_ref().take(3) {}
2047 assert_eq!(iter.size_hint(), (3, Some(3)));
2051 fn test_mut_size_hint() {
2052 let xs = [(1i, 1i), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2054 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2056 let mut iter = map.iter_mut();
2058 for _ in iter.by_ref().take(3) {}
2060 assert_eq!(iter.size_hint(), (3, Some(3)));
2065 let mut map: HashMap<int, int> = HashMap::new();
2071 assert_eq!(map[2], 1);
2076 fn test_index_nonexistent() {
2077 let mut map: HashMap<int, int> = HashMap::new();
2088 let xs = [(1i, 10i), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
2090 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2092 // Existing key (insert)
2093 match map.entry(1) {
2094 Vacant(_) => unreachable!(),
2095 Occupied(mut view) => {
2096 assert_eq!(view.get(), &10);
2097 assert_eq!(view.set(100), 10);
2100 assert_eq!(map.get(&1).unwrap(), &100);
2101 assert_eq!(map.len(), 6);
2104 // Existing key (update)
2105 match map.entry(2) {
2106 Vacant(_) => unreachable!(),
2107 Occupied(mut view) => {
2108 let v = view.get_mut();
2109 let new_v = (*v) * 10;
2113 assert_eq!(map.get(&2).unwrap(), &200);
2114 assert_eq!(map.len(), 6);
2116 // Existing key (take)
2117 match map.entry(3) {
2118 Vacant(_) => unreachable!(),
2120 assert_eq!(view.take(), 30);
2123 assert_eq!(map.get(&3), None);
2124 assert_eq!(map.len(), 5);
2127 // Inexistent key (insert)
2128 match map.entry(10) {
2129 Occupied(_) => unreachable!(),
2131 assert_eq!(*view.set(1000), 1000);
2134 assert_eq!(map.get(&10).unwrap(), &1000);
2135 assert_eq!(map.len(), 6);
2139 fn test_entry_take_doesnt_corrupt() {
2141 fn check(m: &HashMap<int, ()>) {
2143 assert!(m.contains_key(k),
2144 "{} is in keys() but not in the map?", k);
2148 let mut m = HashMap::new();
2149 let mut rng = weak_rng();
2151 // Populate the map with some items.
2152 for _ in range(0u, 50) {
2153 let x = rng.gen_range(-10, 10);
2157 for i in range(0u, 1000) {
2158 let x = rng.gen_range(-10, 10);
2162 println!("{}: remove {}", i, x);