1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // ignore-lexer-test FIXME #15883
14 use self::SearchResult::*;
15 use self::VacantEntryState::*;
17 use borrow::BorrowFrom;
19 use cmp::{max, Eq, PartialEq};
21 use fmt::{self, Debug};
22 use hash::{self, Hash, SipHasher};
23 use iter::{self, Iterator, ExactSizeIterator, IteratorExt, FromIterator, Extend, Map};
25 use mem::{self, replace};
26 use num::{Int, UnsignedInt};
27 use ops::{Deref, FnMut, Index, IndexMut};
28 use option::Option::{self, Some, None};
29 use rand::{self, Rng};
30 use result::Result::{self, Ok, Err};
42 use super::table::BucketState::{
46 use super::state::HashState;
48 const INITIAL_LOG2_CAP: 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 left-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;
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, Debug)]
280 /// /// Create a new Viking.
281 /// fn new(name: &str, country: &str) -> Viking {
282 /// Viking { name: name.to_string(), country: country.to_string() }
286 /// // Use a HashMap to store the vikings' health points.
287 /// let mut vikings = HashMap::new();
289 /// vikings.insert(Viking::new("Einar", "Norway"), 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);
299 #[stable(feature = "rust1", since = "1.0.0")]
300 pub struct HashMap<K, V, S = RandomState> {
301 // All hashes are keyed on these values, to prevent hash collision attacks.
304 table: RawTable<K, V>,
306 resize_policy: DefaultResizePolicy,
309 /// Search for a pre-hashed key.
310 fn search_hashed<K, V, M, F>(table: M,
313 -> SearchResult<K, V, M> where
314 M: Deref<Target=RawTable<K, V>>,
315 F: FnMut(&K) -> bool,
317 let size = table.size();
318 let mut probe = Bucket::new(table, hash);
319 let ib = probe.index();
321 while probe.index() != ib + size {
322 let full = match probe.peek() {
323 Empty(b) => return TableRef(b.into_table()), // hit an empty bucket
327 if full.distance() + ib < full.index() {
328 // We can finish the search early if we hit any bucket
329 // with a lower distance to initial bucket than we've probed.
330 return TableRef(full.into_table());
333 // If the hash doesn't match, it can't be this one..
334 if hash == full.hash() {
335 // If the key doesn't match, it can't be this one..
336 if is_match(full.read().0) {
337 return FoundExisting(full);
344 TableRef(probe.into_table())
347 fn pop_internal<K, V>(starting_bucket: FullBucketMut<K, V>) -> (K, V) {
348 let (empty, retkey, retval) = starting_bucket.take();
349 let mut gap = match empty.gap_peek() {
351 None => return (retkey, retval)
354 while gap.full().distance() != 0 {
355 gap = match gap.shift() {
361 // Now we've done all our shifting. Return the value we grabbed earlier.
365 /// Perform robin hood bucket stealing at the given `bucket`. You must
366 /// also pass the position of that bucket's initial bucket so we don't have
367 /// to recalculate it.
369 /// `hash`, `k`, and `v` are the elements to "robin hood" into the hashtable.
370 fn robin_hood<'a, K: 'a, V: 'a>(mut bucket: FullBucketMut<'a, K, V>,
376 let starting_index = bucket.index();
378 let table = bucket.table(); // FIXME "lifetime too short".
381 // There can be at most `size - dib` buckets to displace, because
382 // in the worst case, there are `size` elements and we already are
383 // `distance` buckets away from the initial one.
384 let idx_end = starting_index + size - bucket.distance();
387 let (old_hash, old_key, old_val) = bucket.replace(hash, k, v);
389 let probe = bucket.next();
390 assert!(probe.index() != idx_end);
392 let full_bucket = match probe.peek() {
395 let b = bucket.put(old_hash, old_key, old_val);
396 // Now that it's stolen, just read the value's pointer
397 // right out of the table!
398 return Bucket::at_index(b.into_table(), starting_index)
404 Full(bucket) => bucket
407 let probe_ib = full_bucket.index() - full_bucket.distance();
409 bucket = full_bucket;
411 // Robin hood! Steal the spot.
423 /// A result that works like Option<FullBucket<..>> but preserves
424 /// the reference that grants us access to the table in any case.
425 enum SearchResult<K, V, M> {
426 // This is an entry that holds the given key:
427 FoundExisting(FullBucket<K, V, M>),
429 // There was no such entry. The reference is given back:
433 impl<K, V, M> SearchResult<K, V, M> {
434 fn into_option(self) -> Option<FullBucket<K, V, M>> {
436 FoundExisting(bucket) => Some(bucket),
442 impl<K, V, S, H> HashMap<K, V, S>
443 where K: Eq + Hash<H>,
444 S: HashState<Hasher=H>,
445 H: hash::Hasher<Output=u64>
447 fn make_hash<X: ?Sized>(&self, x: &X) -> SafeHash where X: Hash<H> {
448 table::make_hash(&self.hash_state, x)
451 /// Search for a key, yielding the index if it's found in the hashtable.
452 /// If you already have the hash for the key lying around, use
454 fn search<'a, Q: ?Sized>(&'a self, q: &Q) -> Option<FullBucketImm<'a, K, V>>
455 where Q: BorrowFrom<K> + Eq + Hash<H>
457 let hash = self.make_hash(q);
458 search_hashed(&self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
462 fn search_mut<'a, Q: ?Sized>(&'a mut self, q: &Q) -> Option<FullBucketMut<'a, K, V>>
463 where Q: BorrowFrom<K> + Eq + Hash<H>
465 let hash = self.make_hash(q);
466 search_hashed(&mut self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
470 // The caller should ensure that invariants by Robin Hood Hashing hold.
471 fn insert_hashed_ordered(&mut self, hash: SafeHash, k: K, v: V) {
472 let cap = self.table.capacity();
473 let mut buckets = Bucket::new(&mut self.table, hash);
474 let ib = buckets.index();
476 while buckets.index() != ib + cap {
477 // We don't need to compare hashes for value swap.
478 // Not even DIBs for Robin Hood.
479 buckets = match buckets.peek() {
481 empty.put(hash, k, v);
484 Full(b) => b.into_bucket()
488 panic!("Internal HashMap error: Out of space.");
492 impl<K: Hash<Hasher> + Eq, V> HashMap<K, V, RandomState> {
493 /// Create an empty HashMap.
498 /// use std::collections::HashMap;
499 /// let mut map: HashMap<&str, int> = HashMap::new();
502 #[stable(feature = "rust1", since = "1.0.0")]
503 pub fn new() -> HashMap<K, V, RandomState> {
507 /// Creates an empty hash map with the given initial capacity.
512 /// use std::collections::HashMap;
513 /// let mut map: HashMap<&str, int> = HashMap::with_capacity(10);
516 #[stable(feature = "rust1", since = "1.0.0")]
517 pub fn with_capacity(capacity: uint) -> HashMap<K, V, RandomState> {
518 HashMap::with_capacity_and_hash_state(capacity, Default::default())
522 impl<K, V, S, H> HashMap<K, V, S>
523 where K: Eq + Hash<H>,
524 S: HashState<Hasher=H>,
525 H: hash::Hasher<Output=u64>
527 /// Creates an empty hashmap which will use the given hasher to hash keys.
529 /// The creates map has the default initial capacity.
534 /// use std::collections::HashMap;
535 /// use std::collections::hash_map::RandomState;
537 /// let s = RandomState::new();
538 /// let mut map = HashMap::with_hash_state(s);
539 /// map.insert(1, 2u);
542 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
543 pub fn with_hash_state(hash_state: S) -> HashMap<K, V, S> {
545 hash_state: hash_state,
546 resize_policy: DefaultResizePolicy::new(),
547 table: RawTable::new(0),
551 /// Create an empty HashMap with space for at least `capacity`
552 /// elements, using `hasher` to hash the keys.
554 /// Warning: `hasher` is normally randomly generated, and
555 /// is designed to allow HashMaps to be resistant to attacks that
556 /// cause many collisions and very poor performance. Setting it
557 /// manually using this function can expose a DoS attack vector.
562 /// use std::collections::HashMap;
563 /// use std::collections::hash_map::RandomState;
565 /// let s = RandomState::new();
566 /// let mut map = HashMap::with_capacity_and_hash_state(10, s);
567 /// map.insert(1, 2u);
570 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
571 pub fn with_capacity_and_hash_state(capacity: uint, hash_state: S)
572 -> HashMap<K, V, S> {
573 let resize_policy = DefaultResizePolicy::new();
574 let min_cap = max(INITIAL_CAPACITY, resize_policy.min_capacity(capacity));
575 let internal_cap = min_cap.checked_next_power_of_two().expect("capacity overflow");
576 assert!(internal_cap >= capacity, "capacity overflow");
578 hash_state: hash_state,
579 resize_policy: resize_policy,
580 table: RawTable::new(internal_cap),
584 /// Returns the number of elements the map can hold without reallocating.
589 /// use std::collections::HashMap;
590 /// let map: HashMap<int, int> = HashMap::with_capacity(100);
591 /// assert!(map.capacity() >= 100);
594 #[stable(feature = "rust1", since = "1.0.0")]
595 pub fn capacity(&self) -> uint {
596 self.resize_policy.usable_capacity(self.table.capacity())
599 /// Reserves capacity for at least `additional` more elements to be inserted
600 /// in the `HashMap`. The collection may reserve more space to avoid
601 /// frequent reallocations.
605 /// Panics if the new allocation size overflows `uint`.
610 /// use std::collections::HashMap;
611 /// let mut map: HashMap<&str, int> = HashMap::new();
614 #[stable(feature = "rust1", since = "1.0.0")]
615 pub fn reserve(&mut self, additional: uint) {
616 let new_size = self.len().checked_add(additional).expect("capacity overflow");
617 let min_cap = self.resize_policy.min_capacity(new_size);
619 // An invalid value shouldn't make us run out of space. This includes
620 // an overflow check.
621 assert!(new_size <= min_cap);
623 if self.table.capacity() < min_cap {
624 let new_capacity = max(min_cap.next_power_of_two(), INITIAL_CAPACITY);
625 self.resize(new_capacity);
629 /// Resizes the internal vectors to a new capacity. It's your responsibility to:
630 /// 1) Make sure the new capacity is enough for all the elements, accounting
631 /// for the load factor.
632 /// 2) Ensure new_capacity is a power of two or zero.
633 fn resize(&mut self, new_capacity: uint) {
634 assert!(self.table.size() <= new_capacity);
635 assert!(new_capacity.is_power_of_two() || new_capacity == 0);
637 let mut old_table = replace(&mut self.table, RawTable::new(new_capacity));
638 let old_size = old_table.size();
640 if old_table.capacity() == 0 || old_table.size() == 0 {
645 // Specialization of the other branch.
646 let mut bucket = Bucket::first(&mut old_table);
648 // "So a few of the first shall be last: for many be called,
651 // We'll most likely encounter a few buckets at the beginning that
652 // have their initial buckets near the end of the table. They were
653 // placed at the beginning as the probe wrapped around the table
654 // during insertion. We must skip forward to a bucket that won't
655 // get reinserted too early and won't unfairly steal others spot.
656 // This eliminates the need for robin hood.
658 bucket = match bucket.peek() {
660 if full.distance() == 0 {
661 // This bucket occupies its ideal spot.
662 // It indicates the start of another "cluster".
663 bucket = full.into_bucket();
666 // Leaving this bucket in the last cluster for later.
670 // Encountered a hole between clusters.
677 // This is how the buckets might be laid out in memory:
678 // ($ marks an initialized bucket)
680 // |$$$_$$$$$$_$$$$$|
682 // But we've skipped the entire initial cluster of buckets
683 // and will continue iteration in this order:
686 // ^ wrap around once end is reached
689 // ^ exit once table.size == 0
691 bucket = match bucket.peek() {
693 let h = bucket.hash();
694 let (b, k, v) = bucket.take();
695 self.insert_hashed_ordered(h, k, v);
697 let t = b.table(); // FIXME "lifetime too short".
698 if t.size() == 0 { break }
702 Empty(b) => b.into_bucket()
707 assert_eq!(self.table.size(), old_size);
710 /// Shrinks the capacity of the map as much as possible. It will drop
711 /// down as much as possible while maintaining the internal rules
712 /// and possibly leaving some space in accordance with the resize policy.
717 /// use std::collections::HashMap;
719 /// let mut map: HashMap<int, int> = HashMap::with_capacity(100);
720 /// map.insert(1, 2);
721 /// map.insert(3, 4);
722 /// assert!(map.capacity() >= 100);
723 /// map.shrink_to_fit();
724 /// assert!(map.capacity() >= 2);
726 #[stable(feature = "rust1", since = "1.0.0")]
727 pub fn shrink_to_fit(&mut self) {
728 let min_capacity = self.resize_policy.min_capacity(self.len());
729 let min_capacity = max(min_capacity.next_power_of_two(), INITIAL_CAPACITY);
731 // An invalid value shouldn't make us run out of space.
732 debug_assert!(self.len() <= min_capacity);
734 if self.table.capacity() != min_capacity {
735 let old_table = replace(&mut self.table, RawTable::new(min_capacity));
736 let old_size = old_table.size();
738 // Shrink the table. Naive algorithm for resizing:
739 for (h, k, v) in old_table.into_iter() {
740 self.insert_hashed_nocheck(h, k, v);
743 debug_assert_eq!(self.table.size(), old_size);
747 /// Insert a pre-hashed key-value pair, without first checking
748 /// that there's enough room in the buckets. Returns a reference to the
749 /// newly insert value.
751 /// If the key already exists, the hashtable will be returned untouched
752 /// and a reference to the existing element will be returned.
753 fn insert_hashed_nocheck(&mut self, hash: SafeHash, k: K, v: V) -> &mut V {
754 self.insert_or_replace_with(hash, k, v, |_, _, _| ())
757 fn insert_or_replace_with<'a, F>(&'a mut self,
761 mut found_existing: F)
763 F: FnMut(&mut K, &mut V, V),
765 // Worst case, we'll find one empty bucket among `size + 1` buckets.
766 let size = self.table.size();
767 let mut probe = Bucket::new(&mut self.table, hash);
768 let ib = probe.index();
771 let mut bucket = match probe.peek() {
774 return bucket.put(hash, k, v).into_mut_refs().1;
776 Full(bucket) => bucket
780 if bucket.hash() == hash {
782 if k == *bucket.read_mut().0 {
783 let (bucket_k, bucket_v) = bucket.into_mut_refs();
784 debug_assert!(k == *bucket_k);
785 // Key already exists. Get its reference.
786 found_existing(bucket_k, bucket_v, v);
791 let robin_ib = bucket.index() as int - bucket.distance() as int;
793 if (ib as int) < robin_ib {
794 // Found a luckier bucket than me. Better steal his spot.
795 return robin_hood(bucket, robin_ib as uint, hash, k, v);
798 probe = bucket.next();
799 assert!(probe.index() != ib + size + 1);
803 /// An iterator visiting all keys in arbitrary order.
804 /// Iterator element type is `&'a K`.
809 /// use std::collections::HashMap;
811 /// let mut map = HashMap::new();
812 /// map.insert("a", 1);
813 /// map.insert("b", 2);
814 /// map.insert("c", 3);
816 /// for key in map.keys() {
817 /// println!("{}", key);
820 #[stable(feature = "rust1", since = "1.0.0")]
821 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
822 fn first<A, B>((a, _): (A, B)) -> A { a }
823 let first: fn((&'a K,&'a V)) -> &'a K = first; // coerce to fn ptr
825 Keys { inner: self.iter().map(first) }
828 /// An iterator visiting all values in arbitrary order.
829 /// Iterator element type is `&'a V`.
834 /// use std::collections::HashMap;
836 /// let mut map = HashMap::new();
837 /// map.insert("a", 1);
838 /// map.insert("b", 2);
839 /// map.insert("c", 3);
841 /// for val in map.values() {
842 /// println!("{}", val);
845 #[stable(feature = "rust1", since = "1.0.0")]
846 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
847 fn second<A, B>((_, b): (A, B)) -> B { b }
848 let second: fn((&'a K,&'a V)) -> &'a V = second; // coerce to fn ptr
850 Values { inner: self.iter().map(second) }
853 /// An iterator visiting all key-value pairs in arbitrary order.
854 /// Iterator element type is `(&'a K, &'a V)`.
859 /// use std::collections::HashMap;
861 /// let mut map = HashMap::new();
862 /// map.insert("a", 1);
863 /// map.insert("b", 2);
864 /// map.insert("c", 3);
866 /// for (key, val) in map.iter() {
867 /// println!("key: {} val: {}", key, val);
870 #[stable(feature = "rust1", since = "1.0.0")]
871 pub fn iter(&self) -> Iter<K, V> {
872 Iter { inner: self.table.iter() }
875 /// An iterator visiting all key-value pairs in arbitrary order,
876 /// with mutable references to the values.
877 /// Iterator element type is `(&'a K, &'a mut V)`.
882 /// use std::collections::HashMap;
884 /// let mut map = HashMap::new();
885 /// map.insert("a", 1);
886 /// map.insert("b", 2);
887 /// map.insert("c", 3);
889 /// // Update all values
890 /// for (_, val) in map.iter_mut() {
894 /// for (key, val) in map.iter() {
895 /// println!("key: {} val: {}", key, val);
898 #[stable(feature = "rust1", since = "1.0.0")]
899 pub fn iter_mut(&mut self) -> IterMut<K, V> {
900 IterMut { inner: self.table.iter_mut() }
903 /// Creates a consuming iterator, that is, one that moves each key-value
904 /// pair out of the map in arbitrary order. The map cannot be used after
910 /// use std::collections::HashMap;
912 /// let mut map = HashMap::new();
913 /// map.insert("a", 1);
914 /// map.insert("b", 2);
915 /// map.insert("c", 3);
917 /// // Not possible with .iter()
918 /// let vec: Vec<(&str, int)> = map.into_iter().collect();
920 #[stable(feature = "rust1", since = "1.0.0")]
921 pub fn into_iter(self) -> IntoIter<K, V> {
922 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
923 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two;
926 inner: self.table.into_iter().map(last_two)
930 /// Gets the given key's corresponding entry in the map for in-place manipulation.
931 #[unstable(feature = "std_misc",
932 reason = "precise API still being fleshed out")]
933 pub fn entry<'a>(&'a mut self, key: K) -> Entry<'a, K, V>
938 let hash = self.make_hash(&key);
939 search_entry_hashed(&mut self.table, hash, key)
942 /// Returns the number of elements in the map.
947 /// use std::collections::HashMap;
949 /// let mut a = HashMap::new();
950 /// assert_eq!(a.len(), 0);
951 /// a.insert(1u, "a");
952 /// assert_eq!(a.len(), 1);
954 #[stable(feature = "rust1", since = "1.0.0")]
955 pub fn len(&self) -> uint { self.table.size() }
957 /// Returns true if the map contains no elements.
962 /// use std::collections::HashMap;
964 /// let mut a = HashMap::new();
965 /// assert!(a.is_empty());
966 /// a.insert(1u, "a");
967 /// assert!(!a.is_empty());
970 #[stable(feature = "rust1", since = "1.0.0")]
971 pub fn is_empty(&self) -> bool { self.len() == 0 }
973 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
974 /// allocated memory for reuse.
979 /// use std::collections::HashMap;
981 /// let mut a = HashMap::new();
982 /// a.insert(1u, "a");
983 /// a.insert(2u, "b");
985 /// for (k, v) in a.drain().take(1) {
986 /// assert!(k == 1 || k == 2);
987 /// assert!(v == "a" || v == "b");
990 /// assert!(a.is_empty());
993 #[unstable(feature = "std_misc",
994 reason = "matches collection reform specification, waiting for dust to settle")]
995 pub fn drain(&mut self) -> Drain<K, V> {
996 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
997 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two; // coerce to fn pointer
1000 inner: self.table.drain().map(last_two),
1004 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
1010 /// use std::collections::HashMap;
1012 /// let mut a = HashMap::new();
1013 /// a.insert(1u, "a");
1015 /// assert!(a.is_empty());
1017 #[stable(feature = "rust1", since = "1.0.0")]
1019 pub fn clear(&mut self) {
1023 /// Returns a reference to the value corresponding to the key.
1025 /// The key may be any borrowed form of the map's key type, but
1026 /// `Hash` and `Eq` on the borrowed form *must* match those for
1032 /// use std::collections::HashMap;
1034 /// let mut map = HashMap::new();
1035 /// map.insert(1u, "a");
1036 /// assert_eq!(map.get(&1), Some(&"a"));
1037 /// assert_eq!(map.get(&2), None);
1039 #[stable(feature = "rust1", since = "1.0.0")]
1040 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
1041 where Q: Hash<H> + Eq + BorrowFrom<K>
1043 self.search(k).map(|bucket| bucket.into_refs().1)
1046 /// Returns true if the map contains a value for the specified key.
1048 /// The key may be any borrowed form of the map's key type, but
1049 /// `Hash` and `Eq` on the borrowed form *must* match those for
1055 /// use std::collections::HashMap;
1057 /// let mut map = HashMap::new();
1058 /// map.insert(1u, "a");
1059 /// assert_eq!(map.contains_key(&1), true);
1060 /// assert_eq!(map.contains_key(&2), false);
1062 #[stable(feature = "rust1", since = "1.0.0")]
1063 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
1064 where Q: Hash<H> + Eq + BorrowFrom<K>
1066 self.search(k).is_some()
1069 /// Returns a mutable reference to the value corresponding to the key.
1071 /// The key may be any borrowed form of the map's key type, but
1072 /// `Hash` and `Eq` on the borrowed form *must* match those for
1078 /// use std::collections::HashMap;
1080 /// let mut map = HashMap::new();
1081 /// map.insert(1u, "a");
1082 /// match map.get_mut(&1) {
1083 /// Some(x) => *x = "b",
1086 /// assert_eq!(map[1], "b");
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
1090 where Q: Hash<H> + Eq + BorrowFrom<K>
1092 self.search_mut(k).map(|bucket| bucket.into_mut_refs().1)
1095 /// Inserts a key-value pair from the map. If the key already had a value
1096 /// present in the map, that value is returned. Otherwise, `None` is returned.
1101 /// use std::collections::HashMap;
1103 /// let mut map = HashMap::new();
1104 /// assert_eq!(map.insert(37u, "a"), None);
1105 /// assert_eq!(map.is_empty(), false);
1107 /// map.insert(37, "b");
1108 /// assert_eq!(map.insert(37, "c"), Some("b"));
1109 /// assert_eq!(map[37], "c");
1111 #[stable(feature = "rust1", since = "1.0.0")]
1112 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1113 let hash = self.make_hash(&k);
1116 let mut retval = None;
1117 self.insert_or_replace_with(hash, k, v, |_, val_ref, val| {
1118 retval = Some(replace(val_ref, val));
1123 /// Removes a key from the map, returning the value at the key if the key
1124 /// was previously in the map.
1126 /// The key may be any borrowed form of the map's key type, but
1127 /// `Hash` and `Eq` on the borrowed form *must* match those for
1133 /// use std::collections::HashMap;
1135 /// let mut map = HashMap::new();
1136 /// map.insert(1u, "a");
1137 /// assert_eq!(map.remove(&1), Some("a"));
1138 /// assert_eq!(map.remove(&1), None);
1140 #[stable(feature = "rust1", since = "1.0.0")]
1141 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
1142 where Q: Hash<H> + Eq + BorrowFrom<K>
1144 if self.table.size() == 0 {
1148 self.search_mut(k).map(|bucket| pop_internal(bucket).1)
1152 fn search_entry_hashed<'a, K: Eq, V>(table: &'a mut RawTable<K,V>, hash: SafeHash, k: K)
1155 // Worst case, we'll find one empty bucket among `size + 1` buckets.
1156 let size = table.size();
1157 let mut probe = Bucket::new(table, hash);
1158 let ib = probe.index();
1161 let bucket = match probe.peek() {
1164 return Vacant(VacantEntry {
1167 elem: NoElem(bucket),
1170 Full(bucket) => bucket
1174 if bucket.hash() == hash {
1176 if k == *bucket.read().0 {
1177 return Occupied(OccupiedEntry{
1183 let robin_ib = bucket.index() as int - bucket.distance() as int;
1185 if (ib as int) < robin_ib {
1186 // Found a luckier bucket than me. Better steal his spot.
1187 return Vacant(VacantEntry {
1190 elem: NeqElem(bucket, robin_ib as uint),
1194 probe = bucket.next();
1195 assert!(probe.index() != ib + size + 1);
1199 impl<K, V, S, H> PartialEq for HashMap<K, V, S>
1200 where K: Eq + Hash<H>, V: PartialEq,
1201 S: HashState<Hasher=H>,
1202 H: hash::Hasher<Output=u64>
1204 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1205 if self.len() != other.len() { return false; }
1207 self.iter().all(|(key, value)|
1208 other.get(key).map_or(false, |v| *value == *v)
1213 #[stable(feature = "rust1", since = "1.0.0")]
1214 impl<K, V, S, H> Eq for HashMap<K, V, S>
1215 where K: Eq + Hash<H>, V: Eq,
1216 S: HashState<Hasher=H>,
1217 H: hash::Hasher<Output=u64>
1220 #[stable(feature = "rust1", since = "1.0.0")]
1221 impl<K, V, S, H> Debug for HashMap<K, V, S>
1222 where K: Eq + Hash<H> + Debug, V: Debug,
1223 S: HashState<Hasher=H>,
1224 H: hash::Hasher<Output=u64>
1226 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1227 try!(write!(f, "HashMap {{"));
1229 for (i, (k, v)) in self.iter().enumerate() {
1230 if i != 0 { try!(write!(f, ", ")); }
1231 try!(write!(f, "{:?}: {:?}", *k, *v));
1238 #[stable(feature = "rust1", since = "1.0.0")]
1239 impl<K, V, S, H> Default for HashMap<K, V, S>
1240 where K: Eq + Hash<H>,
1241 S: HashState<Hasher=H> + Default,
1242 H: hash::Hasher<Output=u64>
1244 fn default() -> HashMap<K, V, S> {
1245 HashMap::with_hash_state(Default::default())
1249 #[stable(feature = "rust1", since = "1.0.0")]
1250 impl<K, Q: ?Sized, V, S, H> Index<Q> for HashMap<K, V, S>
1251 where K: Eq + Hash<H>,
1252 Q: Eq + Hash<H> + BorrowFrom<K>,
1253 S: HashState<Hasher=H>,
1254 H: hash::Hasher<Output=u64>
1259 fn index<'a>(&'a self, index: &Q) -> &'a V {
1260 self.get(index).expect("no entry found for key")
1264 #[stable(feature = "rust1", since = "1.0.0")]
1265 impl<K, V, S, H, Q: ?Sized> IndexMut<Q> for HashMap<K, V, S>
1266 where K: Eq + Hash<H>,
1267 Q: Eq + Hash<H> + BorrowFrom<K>,
1268 S: HashState<Hasher=H>,
1269 H: hash::Hasher<Output=u64>
1274 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1275 self.get_mut(index).expect("no entry found for key")
1279 /// HashMap iterator.
1280 #[stable(feature = "rust1", since = "1.0.0")]
1281 pub struct Iter<'a, K: 'a, V: 'a> {
1282 inner: table::Iter<'a, K, V>
1285 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1286 impl<'a, K, V> Clone for Iter<'a, K, V> {
1287 fn clone(&self) -> Iter<'a, K, V> {
1289 inner: self.inner.clone()
1294 /// HashMap mutable values iterator.
1295 #[stable(feature = "rust1", since = "1.0.0")]
1296 pub struct IterMut<'a, K: 'a, V: 'a> {
1297 inner: table::IterMut<'a, K, V>
1300 /// HashMap move iterator.
1301 #[stable(feature = "rust1", since = "1.0.0")]
1302 pub struct IntoIter<K, V> {
1303 inner: iter::Map<table::IntoIter<K, V>, fn((SafeHash, K, V)) -> (K, V)>
1306 /// HashMap keys iterator.
1307 #[stable(feature = "rust1", since = "1.0.0")]
1308 pub struct Keys<'a, K: 'a, V: 'a> {
1309 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
1312 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1313 impl<'a, K, V> Clone for Keys<'a, K, V> {
1314 fn clone(&self) -> Keys<'a, K, V> {
1316 inner: self.inner.clone()
1321 /// HashMap values iterator.
1322 #[stable(feature = "rust1", since = "1.0.0")]
1323 pub struct Values<'a, K: 'a, V: 'a> {
1324 inner: Map<Iter<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
1327 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1328 impl<'a, K, V> Clone for Values<'a, K, V> {
1329 fn clone(&self) -> Values<'a, K, V> {
1331 inner: self.inner.clone()
1336 /// HashMap drain iterator.
1337 #[unstable(feature = "std_misc",
1338 reason = "matches collection reform specification, waiting for dust to settle")]
1339 pub struct Drain<'a, K: 'a, V: 'a> {
1340 inner: iter::Map<table::Drain<'a, K, V>, fn((SafeHash, K, V)) -> (K, V)>
1343 /// A view into a single occupied location in a HashMap.
1344 #[unstable(feature = "std_misc",
1345 reason = "precise API still being fleshed out")]
1346 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1347 elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
1350 /// A view into a single empty location in a HashMap.
1351 #[unstable(feature = "std_misc",
1352 reason = "precise API still being fleshed out")]
1353 pub struct VacantEntry<'a, K: 'a, V: 'a> {
1356 elem: VacantEntryState<K, V, &'a mut RawTable<K, V>>,
1359 /// A view into a single location in a map, which may be vacant or occupied.
1360 #[unstable(feature = "std_misc",
1361 reason = "precise API still being fleshed out")]
1362 pub enum Entry<'a, K: 'a, V: 'a> {
1363 /// An occupied Entry.
1364 Occupied(OccupiedEntry<'a, K, V>),
1366 Vacant(VacantEntry<'a, K, V>),
1369 /// Possible states of a VacantEntry.
1370 enum VacantEntryState<K, V, M> {
1371 /// The index is occupied, but the key to insert has precedence,
1372 /// and will kick the current one out on insertion.
1373 NeqElem(FullBucket<K, V, M>, uint),
1374 /// The index is genuinely vacant.
1375 NoElem(EmptyBucket<K, V, M>),
1378 #[stable(feature = "rust1", since = "1.0.0")]
1379 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1380 type Item = (&'a K, &'a V);
1382 #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1383 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1385 #[stable(feature = "rust1", since = "1.0.0")]
1386 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
1387 #[inline] fn len(&self) -> usize { self.inner.len() }
1390 #[stable(feature = "rust1", since = "1.0.0")]
1391 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1392 type Item = (&'a K, &'a mut V);
1394 #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1395 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1397 #[stable(feature = "rust1", since = "1.0.0")]
1398 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
1399 #[inline] fn len(&self) -> usize { self.inner.len() }
1402 #[stable(feature = "rust1", since = "1.0.0")]
1403 impl<K, V> Iterator for IntoIter<K, V> {
1406 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1407 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1409 #[stable(feature = "rust1", since = "1.0.0")]
1410 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1411 #[inline] fn len(&self) -> usize { self.inner.len() }
1414 #[stable(feature = "rust1", since = "1.0.0")]
1415 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1418 #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1419 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1421 #[stable(feature = "rust1", since = "1.0.0")]
1422 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {
1423 #[inline] fn len(&self) -> usize { self.inner.len() }
1426 #[stable(feature = "rust1", since = "1.0.0")]
1427 impl<'a, K, V> Iterator for Values<'a, K, V> {
1430 #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1431 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1433 #[stable(feature = "rust1", since = "1.0.0")]
1434 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {
1435 #[inline] fn len(&self) -> usize { self.inner.len() }
1438 #[stable(feature = "rust1", since = "1.0.0")]
1439 impl<'a, K, V> Iterator for Drain<'a, K, V> {
1442 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1443 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1445 #[stable(feature = "rust1", since = "1.0.0")]
1446 impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
1447 #[inline] fn len(&self) -> usize { self.inner.len() }
1450 #[unstable(feature = "std_misc",
1451 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1452 impl<'a, K, V> Entry<'a, K, V> {
1453 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant.
1454 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1456 Occupied(entry) => Ok(entry.into_mut()),
1457 Vacant(entry) => Err(entry),
1462 #[unstable(feature = "std_misc",
1463 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1464 impl<'a, K, V> OccupiedEntry<'a, K, V> {
1465 /// Gets a reference to the value in the entry.
1466 pub fn get(&self) -> &V {
1470 /// Gets a mutable reference to the value in the entry.
1471 pub fn get_mut(&mut self) -> &mut V {
1472 self.elem.read_mut().1
1475 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
1476 /// with a lifetime bound to the map itself
1477 pub fn into_mut(self) -> &'a mut V {
1478 self.elem.into_mut_refs().1
1481 /// Sets the value of the entry, and returns the entry's old value
1482 pub fn insert(&mut self, mut value: V) -> V {
1483 let old_value = self.get_mut();
1484 mem::swap(&mut value, old_value);
1488 /// Takes the value out of the entry, and returns it
1489 pub fn remove(self) -> V {
1490 pop_internal(self.elem).1
1494 #[unstable(feature = "std_misc",
1495 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1496 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
1497 /// Sets the value of the entry with the VacantEntry's key,
1498 /// and returns a mutable reference to it
1499 pub fn insert(self, value: V) -> &'a mut V {
1501 NeqElem(bucket, ib) => {
1502 robin_hood(bucket, ib, self.hash, self.key, value)
1505 bucket.put(self.hash, self.key, value).into_mut_refs().1
1511 #[stable(feature = "rust1", since = "1.0.0")]
1512 impl<K, V, S, H> FromIterator<(K, V)> for HashMap<K, V, S>
1513 where K: Eq + Hash<H>,
1514 S: HashState<Hasher=H> + Default,
1515 H: hash::Hasher<Output=u64>
1517 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> HashMap<K, V, S> {
1518 let lower = iter.size_hint().0;
1519 let mut map = HashMap::with_capacity_and_hash_state(lower,
1520 Default::default());
1526 #[stable(feature = "rust1", since = "1.0.0")]
1527 impl<K, V, S, H> Extend<(K, V)> for HashMap<K, V, S>
1528 where K: Eq + Hash<H>,
1529 S: HashState<Hasher=H>,
1530 H: hash::Hasher<Output=u64>
1532 fn extend<T: Iterator<Item=(K, V)>>(&mut self, mut iter: T) {
1533 for (k, v) in iter {
1540 /// `RandomState` is the default state for `HashMap` types.
1542 /// A particular instance `RandomState` will create the same instances of
1543 /// `Hasher`, but the hashers created by two different `RandomState`
1544 /// instances are unlikely to produce the same result for the same values.
1546 #[allow(missing_copy_implementations)]
1547 #[unstable(feature = "std_misc",
1548 reason = "hashing an hash maps may be altered")]
1549 pub struct RandomState {
1554 #[unstable(feature = "std_misc",
1555 reason = "hashing an hash maps may be altered")]
1557 /// Construct a new `RandomState` that is initialized with random keys.
1559 pub fn new() -> RandomState {
1560 let mut r = rand::thread_rng();
1561 RandomState { k0: r.gen(), k1: r.gen() }
1565 #[unstable(feature = "std_misc",
1566 reason = "hashing an hash maps may be altered")]
1567 impl HashState for RandomState {
1568 type Hasher = Hasher;
1569 fn hasher(&self) -> Hasher {
1570 Hasher { inner: SipHasher::new_with_keys(self.k0, self.k1) }
1574 #[unstable(feature = "std_misc",
1575 reason = "hashing an hash maps may be altered")]
1576 impl Default for RandomState {
1578 fn default() -> RandomState {
1583 /// A hasher implementation which is generated from `RandomState` instances.
1585 /// This is the default hasher used in a `HashMap` to hash keys. Types do not
1586 /// typically declare an ability to explicitly hash into this particular type,
1587 /// but rather in a `H: hash::Writer` type parameter.
1588 #[allow(missing_copy_implementations)]
1589 pub struct Hasher { inner: SipHasher }
1591 impl hash::Writer for Hasher {
1592 fn write(&mut self, data: &[u8]) { self.inner.write(data) }
1595 impl hash::Hasher for Hasher {
1597 fn reset(&mut self) { self.inner.reset() }
1598 fn finish(&self) -> u64 { self.inner.finish() }
1606 use super::Entry::{Occupied, Vacant};
1607 use iter::{range_inclusive, range_step_inclusive, repeat};
1609 use rand::{weak_rng, Rng};
1612 fn test_create_capacity_zero() {
1613 let mut m = HashMap::with_capacity(0);
1615 assert!(m.insert(1, 1).is_none());
1617 assert!(m.contains_key(&1));
1618 assert!(!m.contains_key(&0));
1623 let mut m = HashMap::new();
1624 assert_eq!(m.len(), 0);
1625 assert!(m.insert(1, 2).is_none());
1626 assert_eq!(m.len(), 1);
1627 assert!(m.insert(2, 4).is_none());
1628 assert_eq!(m.len(), 2);
1629 assert_eq!(*m.get(&1).unwrap(), 2);
1630 assert_eq!(*m.get(&2).unwrap(), 4);
1633 thread_local! { static DROP_VECTOR: RefCell<Vec<int>> = RefCell::new(Vec::new()) }
1635 #[derive(Hash, PartialEq, Eq)]
1641 fn new(k: uint) -> Dropable {
1642 DROP_VECTOR.with(|slot| {
1643 slot.borrow_mut()[k] += 1;
1650 impl Drop for Dropable {
1651 fn drop(&mut self) {
1652 DROP_VECTOR.with(|slot| {
1653 slot.borrow_mut()[self.k] -= 1;
1658 impl Clone for Dropable {
1659 fn clone(&self) -> Dropable {
1660 Dropable::new(self.k)
1666 DROP_VECTOR.with(|slot| {
1667 *slot.borrow_mut() = repeat(0).take(200).collect();
1671 let mut m = HashMap::new();
1673 DROP_VECTOR.with(|v| {
1675 assert_eq!(v.borrow()[i], 0);
1680 let d1 = Dropable::new(i);
1681 let d2 = Dropable::new(i+100);
1685 DROP_VECTOR.with(|v| {
1687 assert_eq!(v.borrow()[i], 1);
1692 let k = Dropable::new(i);
1693 let v = m.remove(&k);
1695 assert!(v.is_some());
1697 DROP_VECTOR.with(|v| {
1698 assert_eq!(v.borrow()[i], 1);
1699 assert_eq!(v.borrow()[i+100], 1);
1703 DROP_VECTOR.with(|v| {
1705 assert_eq!(v.borrow()[i], 0);
1706 assert_eq!(v.borrow()[i+100], 0);
1710 assert_eq!(v.borrow()[i], 1);
1711 assert_eq!(v.borrow()[i+100], 1);
1716 DROP_VECTOR.with(|v| {
1718 assert_eq!(v.borrow()[i], 0);
1724 fn test_move_iter_drops() {
1725 DROP_VECTOR.with(|v| {
1726 *v.borrow_mut() = repeat(0).take(200).collect();
1730 let mut hm = HashMap::new();
1732 DROP_VECTOR.with(|v| {
1734 assert_eq!(v.borrow()[i], 0);
1739 let d1 = Dropable::new(i);
1740 let d2 = Dropable::new(i+100);
1744 DROP_VECTOR.with(|v| {
1746 assert_eq!(v.borrow()[i], 1);
1753 // By the way, ensure that cloning doesn't screw up the dropping.
1757 let mut half = hm.into_iter().take(50);
1759 DROP_VECTOR.with(|v| {
1761 assert_eq!(v.borrow()[i], 1);
1765 for _ in half.by_ref() {}
1767 DROP_VECTOR.with(|v| {
1768 let nk = (0u..100).filter(|&i| {
1772 let nv = (0u..100).filter(|&i| {
1773 v.borrow()[i+100] == 1
1781 DROP_VECTOR.with(|v| {
1783 assert_eq!(v.borrow()[i], 0);
1789 fn test_empty_pop() {
1790 let mut m: HashMap<int, bool> = HashMap::new();
1791 assert_eq!(m.remove(&0), None);
1795 fn test_lots_of_insertions() {
1796 let mut m = HashMap::new();
1798 // Try this a few times to make sure we never screw up the hashmap's
1801 assert!(m.is_empty());
1803 for i in range_inclusive(1, 1000) {
1804 assert!(m.insert(i, i).is_none());
1806 for j in range_inclusive(1, i) {
1808 assert_eq!(r, Some(&j));
1811 for j in range_inclusive(i+1, 1000) {
1813 assert_eq!(r, None);
1817 for i in range_inclusive(1001, 2000) {
1818 assert!(!m.contains_key(&i));
1822 for i in range_inclusive(1, 1000) {
1823 assert!(m.remove(&i).is_some());
1825 for j in range_inclusive(1, i) {
1826 assert!(!m.contains_key(&j));
1829 for j in range_inclusive(i+1, 1000) {
1830 assert!(m.contains_key(&j));
1834 for i in range_inclusive(1, 1000) {
1835 assert!(!m.contains_key(&i));
1838 for i in range_inclusive(1, 1000) {
1839 assert!(m.insert(i, i).is_none());
1843 for i in range_step_inclusive(1000, 1, -1) {
1844 assert!(m.remove(&i).is_some());
1846 for j in range_inclusive(i, 1000) {
1847 assert!(!m.contains_key(&j));
1850 for j in range_inclusive(1, i-1) {
1851 assert!(m.contains_key(&j));
1858 fn test_find_mut() {
1859 let mut m = HashMap::new();
1860 assert!(m.insert(1, 12).is_none());
1861 assert!(m.insert(2, 8).is_none());
1862 assert!(m.insert(5, 14).is_none());
1864 match m.get_mut(&5) {
1865 None => panic!(), Some(x) => *x = new
1867 assert_eq!(m.get(&5), Some(&new));
1871 fn test_insert_overwrite() {
1872 let mut m = HashMap::new();
1873 assert!(m.insert(1, 2).is_none());
1874 assert_eq!(*m.get(&1).unwrap(), 2);
1875 assert!(!m.insert(1, 3).is_none());
1876 assert_eq!(*m.get(&1).unwrap(), 3);
1880 fn test_insert_conflicts() {
1881 let mut m = HashMap::with_capacity(4);
1882 assert!(m.insert(1, 2).is_none());
1883 assert!(m.insert(5, 3).is_none());
1884 assert!(m.insert(9, 4).is_none());
1885 assert_eq!(*m.get(&9).unwrap(), 4);
1886 assert_eq!(*m.get(&5).unwrap(), 3);
1887 assert_eq!(*m.get(&1).unwrap(), 2);
1891 fn test_conflict_remove() {
1892 let mut m = HashMap::with_capacity(4);
1893 assert!(m.insert(1, 2).is_none());
1894 assert_eq!(*m.get(&1).unwrap(), 2);
1895 assert!(m.insert(5, 3).is_none());
1896 assert_eq!(*m.get(&1).unwrap(), 2);
1897 assert_eq!(*m.get(&5).unwrap(), 3);
1898 assert!(m.insert(9, 4).is_none());
1899 assert_eq!(*m.get(&1).unwrap(), 2);
1900 assert_eq!(*m.get(&5).unwrap(), 3);
1901 assert_eq!(*m.get(&9).unwrap(), 4);
1902 assert!(m.remove(&1).is_some());
1903 assert_eq!(*m.get(&9).unwrap(), 4);
1904 assert_eq!(*m.get(&5).unwrap(), 3);
1908 fn test_is_empty() {
1909 let mut m = HashMap::with_capacity(4);
1910 assert!(m.insert(1, 2).is_none());
1911 assert!(!m.is_empty());
1912 assert!(m.remove(&1).is_some());
1913 assert!(m.is_empty());
1918 let mut m = HashMap::new();
1920 assert_eq!(m.remove(&1), Some(2));
1921 assert_eq!(m.remove(&1), None);
1926 let mut m = HashMap::with_capacity(4);
1928 assert!(m.insert(i, i*2).is_none());
1930 assert_eq!(m.len(), 32);
1932 let mut observed: u32 = 0;
1934 for (k, v) in m.iter() {
1935 assert_eq!(*v, *k * 2);
1936 observed |= 1 << *k;
1938 assert_eq!(observed, 0xFFFF_FFFF);
1943 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1944 let map = vec.into_iter().collect::<HashMap<int, char>>();
1945 let keys = map.keys().map(|&k| k).collect::<Vec<int>>();
1946 assert_eq!(keys.len(), 3);
1947 assert!(keys.contains(&1));
1948 assert!(keys.contains(&2));
1949 assert!(keys.contains(&3));
1954 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1955 let map = vec.into_iter().collect::<HashMap<int, char>>();
1956 let values = map.values().map(|&v| v).collect::<Vec<char>>();
1957 assert_eq!(values.len(), 3);
1958 assert!(values.contains(&'a'));
1959 assert!(values.contains(&'b'));
1960 assert!(values.contains(&'c'));
1965 let mut m = HashMap::new();
1966 assert!(m.get(&1).is_none());
1970 Some(v) => assert_eq!(*v, 2)
1976 let mut m1 = HashMap::new();
1981 let mut m2 = HashMap::new();
1994 let mut map: HashMap<int, int> = HashMap::new();
1995 let empty: HashMap<int, int> = HashMap::new();
2000 let map_str = format!("{:?}", map);
2002 assert!(map_str == "HashMap {1: 2, 3: 4}" ||
2003 map_str == "HashMap {3: 4, 1: 2}");
2004 assert_eq!(format!("{:?}", empty), "HashMap {}");
2009 let mut m = HashMap::new();
2011 assert_eq!(m.len(), 0);
2012 assert!(m.is_empty());
2015 let old_cap = m.table.capacity();
2016 while old_cap == m.table.capacity() {
2021 assert_eq!(m.len(), i);
2022 assert!(!m.is_empty());
2026 fn test_behavior_resize_policy() {
2027 let mut m = HashMap::new();
2029 assert_eq!(m.len(), 0);
2030 assert_eq!(m.table.capacity(), 0);
2031 assert!(m.is_empty());
2035 assert!(m.is_empty());
2036 let initial_cap = m.table.capacity();
2037 m.reserve(initial_cap);
2038 let cap = m.table.capacity();
2040 assert_eq!(cap, initial_cap * 2);
2043 for _ in 0..cap * 3 / 4 {
2047 // three quarters full
2049 assert_eq!(m.len(), i);
2050 assert_eq!(m.table.capacity(), cap);
2052 for _ in 0..cap / 4 {
2058 let new_cap = m.table.capacity();
2059 assert_eq!(new_cap, cap * 2);
2061 for _ in 0..cap / 2 - 1 {
2064 assert_eq!(m.table.capacity(), new_cap);
2066 // A little more than one quarter full.
2068 assert_eq!(m.table.capacity(), cap);
2069 // again, a little more than half full
2070 for _ in 0..cap / 2 - 1 {
2076 assert_eq!(m.len(), i);
2077 assert!(!m.is_empty());
2078 assert_eq!(m.table.capacity(), initial_cap);
2082 fn test_reserve_shrink_to_fit() {
2083 let mut m = HashMap::new();
2086 assert!(m.capacity() >= m.len());
2092 let usable_cap = m.capacity();
2093 for i in 128us..128+256 {
2095 assert_eq!(m.capacity(), usable_cap);
2098 for i in 100us..128+256 {
2099 assert_eq!(m.remove(&i), Some(i));
2103 assert_eq!(m.len(), 100);
2104 assert!(!m.is_empty());
2105 assert!(m.capacity() >= m.len());
2108 assert_eq!(m.remove(&i), Some(i));
2113 assert_eq!(m.len(), 1);
2114 assert!(m.capacity() >= m.len());
2115 assert_eq!(m.remove(&0), Some(0));
2119 fn test_from_iter() {
2120 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2122 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2124 for &(k, v) in xs.iter() {
2125 assert_eq!(map.get(&k), Some(&v));
2130 fn test_size_hint() {
2131 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2133 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2135 let mut iter = map.iter();
2137 for _ in iter.by_ref().take(3) {}
2139 assert_eq!(iter.size_hint(), (3, Some(3)));
2143 fn test_iter_len() {
2144 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2146 let map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2148 let mut iter = map.iter();
2150 for _ in iter.by_ref().take(3) {}
2152 assert_eq!(iter.len(), 3);
2156 fn test_mut_size_hint() {
2157 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2159 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2161 let mut iter = map.iter_mut();
2163 for _ in iter.by_ref().take(3) {}
2165 assert_eq!(iter.size_hint(), (3, Some(3)));
2169 fn test_iter_mut_len() {
2170 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2172 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2174 let mut iter = map.iter_mut();
2176 for _ in iter.by_ref().take(3) {}
2178 assert_eq!(iter.len(), 3);
2183 let mut map: HashMap<int, int> = HashMap::new();
2189 assert_eq!(map[2], 1);
2194 fn test_index_nonexistent() {
2195 let mut map: HashMap<int, int> = HashMap::new();
2206 let xs = [(1, 10), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
2208 let mut map: HashMap<int, int> = xs.iter().map(|&x| x).collect();
2210 // Existing key (insert)
2211 match map.entry(1) {
2212 Vacant(_) => unreachable!(),
2213 Occupied(mut view) => {
2214 assert_eq!(view.get(), &10);
2215 assert_eq!(view.insert(100), 10);
2218 assert_eq!(map.get(&1).unwrap(), &100);
2219 assert_eq!(map.len(), 6);
2222 // Existing key (update)
2223 match map.entry(2) {
2224 Vacant(_) => unreachable!(),
2225 Occupied(mut view) => {
2226 let v = view.get_mut();
2227 let new_v = (*v) * 10;
2231 assert_eq!(map.get(&2).unwrap(), &200);
2232 assert_eq!(map.len(), 6);
2234 // Existing key (take)
2235 match map.entry(3) {
2236 Vacant(_) => unreachable!(),
2238 assert_eq!(view.remove(), 30);
2241 assert_eq!(map.get(&3), None);
2242 assert_eq!(map.len(), 5);
2245 // Inexistent key (insert)
2246 match map.entry(10) {
2247 Occupied(_) => unreachable!(),
2249 assert_eq!(*view.insert(1000), 1000);
2252 assert_eq!(map.get(&10).unwrap(), &1000);
2253 assert_eq!(map.len(), 6);
2257 fn test_entry_take_doesnt_corrupt() {
2259 fn check(m: &HashMap<int, ()>) {
2261 assert!(m.contains_key(k),
2262 "{} is in keys() but not in the map?", k);
2266 let mut m = HashMap::new();
2267 let mut rng = weak_rng();
2269 // Populate the map with some items.
2271 let x = rng.gen_range(-10, 10);
2276 let x = rng.gen_range(-10, 10);
2280 println!("{}: remove {}", i, x);