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, IntoIterator, IteratorExt, FromIterator, Extend, Map};
25 use mem::{self, replace};
26 use num::{Int, UnsignedInt};
27 use ops::{Deref, FnMut, Index, IndexMut};
28 use option::Option::{self, Some, None};
29 use rand::{self, Rng};
30 use result::Result::{self, Ok, Err};
42 use super::table::BucketState::{
46 use super::state::HashState;
48 const INITIAL_LOG2_CAP: usize = 5;
49 #[unstable(feature = "std_misc")]
50 pub const INITIAL_CAPACITY: usize = 1 << INITIAL_LOG2_CAP; // 2^5
52 /// The default behavior of HashMap implements a load factor of 90.9%.
53 /// This behavior is characterized by the following condition:
55 /// - if size > 0.909 * capacity: grow the map
57 struct DefaultResizePolicy;
59 impl DefaultResizePolicy {
60 fn new() -> DefaultResizePolicy {
65 fn min_capacity(&self, usable_size: usize) -> usize {
66 // Here, we are rephrasing the logic by specifying the lower limit
69 // - if `cap < size * 1.1`: grow the map
73 /// An inverse of `min_capacity`, approximately.
75 fn usable_capacity(&self, cap: usize) -> usize {
76 // As the number of entries approaches usable capacity,
77 // min_capacity(size) must be smaller than the internal capacity,
78 // so that the map is not resized:
79 // `min_capacity(usable_capacity(x)) <= x`.
80 // The left-hand side can only be smaller due to flooring by integer
83 // This doesn't have to be checked for overflow since allocation size
84 // in bytes will overflow earlier than multiplication by 10.
90 fn test_resize_policy() {
92 let rp = DefaultResizePolicy;
94 assert!(rp.min_capacity(rp.usable_capacity(n)) <= n);
95 assert!(rp.usable_capacity(rp.min_capacity(n)) <= n);
99 // The main performance trick in this hashmap is called Robin Hood Hashing.
100 // It gains its excellent performance from one essential operation:
102 // If an insertion collides with an existing element, and that element's
103 // "probe distance" (how far away the element is from its ideal location)
104 // is higher than how far we've already probed, swap the elements.
106 // This massively lowers variance in probe distance, and allows us to get very
107 // high load factors with good performance. The 90% load factor I use is rather
110 // > Why a load factor of approximately 90%?
112 // In general, all the distances to initial buckets will converge on the mean.
113 // At a load factor of α, the odds of finding the target bucket after k
114 // probes is approximately 1-α^k. If we set this equal to 50% (since we converge
115 // on the mean) and set k=8 (64-byte cache line / 8-byte hash), α=0.92. I round
116 // this down to make the math easier on the CPU and avoid its FPU.
117 // Since on average we start the probing in the middle of a cache line, this
118 // strategy pulls in two cache lines of hashes on every lookup. I think that's
119 // pretty good, but if you want to trade off some space, it could go down to one
120 // cache line on average with an α of 0.84.
122 // > Wait, what? Where did you get 1-α^k from?
124 // On the first probe, your odds of a collision with an existing element is α.
125 // The odds of doing this twice in a row is approximately α^2. For three times,
126 // α^3, etc. Therefore, the odds of colliding k times is α^k. The odds of NOT
127 // colliding after k tries is 1-α^k.
129 // The paper from 1986 cited below mentions an implementation which keeps track
130 // of the distance-to-initial-bucket histogram. This approach is not suitable
131 // for modern architectures because it requires maintaining an internal data
132 // structure. This allows very good first guesses, but we are most concerned
133 // with guessing entire cache lines, not individual indexes. Furthermore, array
134 // accesses are no longer linear and in one direction, as we have now. There
135 // is also memory and cache pressure that this would entail that would be very
136 // difficult to properly see in a microbenchmark.
138 // ## Future Improvements (FIXME!)
140 // Allow the load factor to be changed dynamically and/or at initialization.
142 // Also, would it be possible for us to reuse storage when growing the
143 // underlying table? This is exactly the use case for 'realloc', and may
144 // be worth exploring.
146 // ## Future Optimizations (FIXME!)
148 // Another possible design choice that I made without any real reason is
149 // parameterizing the raw table over keys and values. Technically, all we need
150 // is the size and alignment of keys and values, and the code should be just as
151 // efficient (well, we might need one for power-of-two size and one for not...).
152 // This has the potential to reduce code bloat in rust executables, without
153 // really losing anything except 4 words (key size, key alignment, val size,
154 // val alignment) which can be passed in to every call of a `RawTable` function.
155 // This would definitely be an avenue worth exploring if people start complaining
156 // about the size of rust executables.
158 // Annotate exceedingly likely branches in `table::make_hash`
159 // and `search_hashed` to reduce instruction cache pressure
160 // and mispredictions once it becomes possible (blocked on issue #11092).
162 // Shrinking the table could simply reallocate in place after moving buckets
163 // to the first half.
165 // The growth algorithm (fragment of the Proof of Correctness)
166 // --------------------
168 // The growth algorithm is basically a fast path of the naive reinsertion-
169 // during-resize algorithm. Other paths should never be taken.
171 // Consider growing a robin hood hashtable of capacity n. Normally, we do this
172 // by allocating a new table of capacity `2n`, and then individually reinsert
173 // each element in the old table into the new one. This guarantees that the
174 // new table is a valid robin hood hashtable with all the desired statistical
175 // properties. Remark that the order we reinsert the elements in should not
176 // matter. For simplicity and efficiency, we will consider only linear
177 // reinsertions, which consist of reinserting all elements in the old table
178 // into the new one by increasing order of index. However we will not be
179 // starting our reinsertions from index 0 in general. If we start from index
180 // i, for the purpose of reinsertion we will consider all elements with real
181 // index j < i to have virtual index n + j.
183 // Our hash generation scheme consists of generating a 64-bit hash and
184 // truncating the most significant bits. When moving to the new table, we
185 // simply introduce a new bit to the front of the hash. Therefore, if an
186 // elements has ideal index i in the old table, it can have one of two ideal
187 // locations in the new table. If the new bit is 0, then the new ideal index
188 // is i. If the new bit is 1, then the new ideal index is n + i. Intuitively,
189 // we are producing two independent tables of size n, and for each element we
190 // independently choose which table to insert it into with equal probability.
191 // However the rather than wrapping around themselves on overflowing their
192 // indexes, the first table overflows into the first, and the first into the
193 // second. Visually, our new table will look something like:
195 // [yy_xxx_xxxx_xxx|xx_yyy_yyyy_yyy]
197 // Where x's are elements inserted into the first table, y's are elements
198 // inserted into the second, and _'s are empty sections. We now define a few
199 // key concepts that we will use later. Note that this is a very abstract
200 // perspective of the table. A real resized table would be at least half
203 // Theorem: A linear robin hood reinsertion from the first ideal element
204 // produces identical results to a linear naive reinsertion from the same
207 // FIXME(Gankro, pczarn): review the proof and put it all in a separate doc.rs
209 /// A hash map implementation which uses linear probing with Robin
210 /// Hood bucket stealing.
212 /// The hashes are all keyed by the task-local random number generator
213 /// on creation by default. This means that the ordering of the keys is
214 /// randomized, but makes the tables more resistant to
215 /// denial-of-service attacks (Hash DoS). This behaviour can be
216 /// overridden with one of the constructors.
218 /// It is required that the keys implement the `Eq` and `Hash` traits, although
219 /// this can frequently be achieved by using `#[derive(Eq, Hash)]`.
221 /// Relevant papers/articles:
223 /// 1. Pedro Celis. ["Robin Hood Hashing"](https://cs.uwaterloo.ca/research/tr/1986/CS-86-14.pdf)
224 /// 2. Emmanuel Goossaert. ["Robin Hood
225 /// hashing"](http://codecapsule.com/2013/11/11/robin-hood-hashing/)
226 /// 3. Emmanuel Goossaert. ["Robin Hood hashing: backward shift
227 /// deletion"](http://codecapsule.com/2013/11/17/robin-hood-hashing-backward-shift-deletion/)
232 /// use std::collections::HashMap;
234 /// // type inference lets us omit an explicit type signature (which
235 /// // would be `HashMap<&str, &str>` in this example).
236 /// let mut book_reviews = HashMap::new();
238 /// // review some books.
239 /// book_reviews.insert("Adventures of Huckleberry Finn", "My favorite book.");
240 /// book_reviews.insert("Grimms' Fairy Tales", "Masterpiece.");
241 /// book_reviews.insert("Pride and Prejudice", "Very enjoyable.");
242 /// book_reviews.insert("The Adventures of Sherlock Holmes", "Eye lyked it alot.");
244 /// // check for a specific one.
245 /// if !book_reviews.contains_key(&("Les Misérables")) {
246 /// println!("We've got {} reviews, but Les Misérables ain't one.",
247 /// book_reviews.len());
250 /// // oops, this review has a lot of spelling mistakes, let's delete it.
251 /// book_reviews.remove(&("The Adventures of Sherlock Holmes"));
253 /// // look up the values associated with some keys.
254 /// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
255 /// for book in to_find.iter() {
256 /// match book_reviews.get(book) {
257 /// Some(review) => println!("{}: {}", *book, *review),
258 /// None => println!("{} is unreviewed.", *book)
262 /// // iterate over everything.
263 /// for (book, review) in book_reviews.iter() {
264 /// println!("{}: \"{}\"", *book, *review);
268 /// The easiest way to use `HashMap` with a custom type as key is to derive `Eq` and `Hash`.
269 /// We must also derive `PartialEq`.
272 /// use std::collections::HashMap;
274 /// #[derive(Hash, Eq, PartialEq, Debug)]
281 /// /// Create a new Viking.
282 /// fn new(name: &str, country: &str) -> Viking {
283 /// Viking { name: name.to_string(), country: country.to_string() }
287 /// // Use a HashMap to store the vikings' health points.
288 /// let mut vikings = HashMap::new();
290 /// vikings.insert(Viking::new("Einar", "Norway"), 25u);
291 /// vikings.insert(Viking::new("Olaf", "Denmark"), 24u);
292 /// vikings.insert(Viking::new("Harald", "Iceland"), 12u);
294 /// // Use derived implementation to print the status of the vikings.
295 /// for (viking, health) in vikings.iter() {
296 /// println!("{:?} has {} hp", viking, health);
300 #[stable(feature = "rust1", since = "1.0.0")]
301 pub struct HashMap<K, V, S = RandomState> {
302 // All hashes are keyed on these values, to prevent hash collision attacks.
305 table: RawTable<K, V>,
307 resize_policy: DefaultResizePolicy,
310 /// Search for a pre-hashed key.
311 fn search_hashed<K, V, M, F>(table: M,
314 -> SearchResult<K, V, M> where
315 M: Deref<Target=RawTable<K, V>>,
316 F: FnMut(&K) -> bool,
318 let size = table.size();
319 let mut probe = Bucket::new(table, hash);
320 let ib = probe.index();
322 while probe.index() != ib + size {
323 let full = match probe.peek() {
324 Empty(b) => return TableRef(b.into_table()), // hit an empty bucket
328 if full.distance() + ib < full.index() {
329 // We can finish the search early if we hit any bucket
330 // with a lower distance to initial bucket than we've probed.
331 return TableRef(full.into_table());
334 // If the hash doesn't match, it can't be this one..
335 if hash == full.hash() {
336 // If the key doesn't match, it can't be this one..
337 if is_match(full.read().0) {
338 return FoundExisting(full);
345 TableRef(probe.into_table())
348 fn pop_internal<K, V>(starting_bucket: FullBucketMut<K, V>) -> (K, V) {
349 let (empty, retkey, retval) = starting_bucket.take();
350 let mut gap = match empty.gap_peek() {
352 None => return (retkey, retval)
355 while gap.full().distance() != 0 {
356 gap = match gap.shift() {
362 // Now we've done all our shifting. Return the value we grabbed earlier.
366 /// Perform robin hood bucket stealing at the given `bucket`. You must
367 /// also pass the position of that bucket's initial bucket so we don't have
368 /// to recalculate it.
370 /// `hash`, `k`, and `v` are the elements to "robin hood" into the hashtable.
371 fn robin_hood<'a, K: 'a, V: 'a>(mut bucket: FullBucketMut<'a, K, V>,
377 let starting_index = bucket.index();
379 let table = bucket.table(); // FIXME "lifetime too short".
382 // There can be at most `size - dib` buckets to displace, because
383 // in the worst case, there are `size` elements and we already are
384 // `distance` buckets away from the initial one.
385 let idx_end = starting_index + size - bucket.distance();
388 let (old_hash, old_key, old_val) = bucket.replace(hash, k, v);
390 let probe = bucket.next();
391 assert!(probe.index() != idx_end);
393 let full_bucket = match probe.peek() {
396 let b = bucket.put(old_hash, old_key, old_val);
397 // Now that it's stolen, just read the value's pointer
398 // right out of the table!
399 return Bucket::at_index(b.into_table(), starting_index)
405 Full(bucket) => bucket
408 let probe_ib = full_bucket.index() - full_bucket.distance();
410 bucket = full_bucket;
412 // Robin hood! Steal the spot.
424 /// A result that works like Option<FullBucket<..>> but preserves
425 /// the reference that grants us access to the table in any case.
426 enum SearchResult<K, V, M> {
427 // This is an entry that holds the given key:
428 FoundExisting(FullBucket<K, V, M>),
430 // There was no such entry. The reference is given back:
434 impl<K, V, M> SearchResult<K, V, M> {
435 fn into_option(self) -> Option<FullBucket<K, V, M>> {
437 FoundExisting(bucket) => Some(bucket),
443 impl<K, V, S, H> HashMap<K, V, S>
444 where K: Eq + Hash<H>,
445 S: HashState<Hasher=H>,
446 H: hash::Hasher<Output=u64>
448 fn make_hash<X: ?Sized>(&self, x: &X) -> SafeHash where X: Hash<H> {
449 table::make_hash(&self.hash_state, x)
452 /// Search for a key, yielding the index if it's found in the hashtable.
453 /// If you already have the hash for the key lying around, use
455 fn search<'a, Q: ?Sized>(&'a self, q: &Q) -> Option<FullBucketImm<'a, K, V>>
456 where Q: BorrowFrom<K> + Eq + Hash<H>
458 let hash = self.make_hash(q);
459 search_hashed(&self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
463 fn search_mut<'a, Q: ?Sized>(&'a mut self, q: &Q) -> Option<FullBucketMut<'a, K, V>>
464 where Q: BorrowFrom<K> + Eq + Hash<H>
466 let hash = self.make_hash(q);
467 search_hashed(&mut self.table, hash, |k| q.eq(BorrowFrom::borrow_from(k)))
471 // The caller should ensure that invariants by Robin Hood Hashing hold.
472 fn insert_hashed_ordered(&mut self, hash: SafeHash, k: K, v: V) {
473 let cap = self.table.capacity();
474 let mut buckets = Bucket::new(&mut self.table, hash);
475 let ib = buckets.index();
477 while buckets.index() != ib + cap {
478 // We don't need to compare hashes for value swap.
479 // Not even DIBs for Robin Hood.
480 buckets = match buckets.peek() {
482 empty.put(hash, k, v);
485 Full(b) => b.into_bucket()
489 panic!("Internal HashMap error: Out of space.");
493 impl<K: Hash<Hasher> + Eq, V> HashMap<K, V, RandomState> {
494 /// Create an empty HashMap.
499 /// use std::collections::HashMap;
500 /// let mut map: HashMap<&str, int> = HashMap::new();
503 #[stable(feature = "rust1", since = "1.0.0")]
504 pub fn new() -> HashMap<K, V, RandomState> {
508 /// Creates an empty hash map with the given initial capacity.
513 /// use std::collections::HashMap;
514 /// let mut map: HashMap<&str, int> = HashMap::with_capacity(10);
517 #[stable(feature = "rust1", since = "1.0.0")]
518 pub fn with_capacity(capacity: usize) -> HashMap<K, V, RandomState> {
519 HashMap::with_capacity_and_hash_state(capacity, Default::default())
523 impl<K, V, S, H> HashMap<K, V, S>
524 where K: Eq + Hash<H>,
525 S: HashState<Hasher=H>,
526 H: hash::Hasher<Output=u64>
528 /// Creates an empty hashmap which will use the given hasher to hash keys.
530 /// The creates map has the default initial capacity.
535 /// use std::collections::HashMap;
536 /// use std::collections::hash_map::RandomState;
538 /// let s = RandomState::new();
539 /// let mut map = HashMap::with_hash_state(s);
540 /// map.insert(1, 2u);
543 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
544 pub fn with_hash_state(hash_state: S) -> HashMap<K, V, S> {
546 hash_state: hash_state,
547 resize_policy: DefaultResizePolicy::new(),
548 table: RawTable::new(0),
552 /// Create an empty HashMap with space for at least `capacity`
553 /// elements, using `hasher` to hash the keys.
555 /// Warning: `hasher` is normally randomly generated, and
556 /// is designed to allow HashMaps to be resistant to attacks that
557 /// cause many collisions and very poor performance. Setting it
558 /// manually using this function can expose a DoS attack vector.
563 /// use std::collections::HashMap;
564 /// use std::collections::hash_map::RandomState;
566 /// let s = RandomState::new();
567 /// let mut map = HashMap::with_capacity_and_hash_state(10, s);
568 /// map.insert(1, 2u);
571 #[unstable(feature = "std_misc", reason = "hasher stuff is unclear")]
572 pub fn with_capacity_and_hash_state(capacity: usize, hash_state: S)
573 -> HashMap<K, V, S> {
574 let resize_policy = DefaultResizePolicy::new();
575 let min_cap = max(INITIAL_CAPACITY, resize_policy.min_capacity(capacity));
576 let internal_cap = min_cap.checked_next_power_of_two().expect("capacity overflow");
577 assert!(internal_cap >= capacity, "capacity overflow");
579 hash_state: hash_state,
580 resize_policy: resize_policy,
581 table: RawTable::new(internal_cap),
585 /// Returns the number of elements the map can hold without reallocating.
590 /// use std::collections::HashMap;
591 /// let map: HashMap<int, int> = HashMap::with_capacity(100);
592 /// assert!(map.capacity() >= 100);
595 #[stable(feature = "rust1", since = "1.0.0")]
596 pub fn capacity(&self) -> usize {
597 self.resize_policy.usable_capacity(self.table.capacity())
600 /// Reserves capacity for at least `additional` more elements to be inserted
601 /// in the `HashMap`. The collection may reserve more space to avoid
602 /// frequent reallocations.
606 /// Panics if the new allocation size overflows `usize`.
611 /// use std::collections::HashMap;
612 /// let mut map: HashMap<&str, int> = HashMap::new();
615 #[stable(feature = "rust1", since = "1.0.0")]
616 pub fn reserve(&mut self, additional: usize) {
617 let new_size = self.len().checked_add(additional).expect("capacity overflow");
618 let min_cap = self.resize_policy.min_capacity(new_size);
620 // An invalid value shouldn't make us run out of space. This includes
621 // an overflow check.
622 assert!(new_size <= min_cap);
624 if self.table.capacity() < min_cap {
625 let new_capacity = max(min_cap.next_power_of_two(), INITIAL_CAPACITY);
626 self.resize(new_capacity);
630 /// Resizes the internal vectors to a new capacity. It's your responsibility to:
631 /// 1) Make sure the new capacity is enough for all the elements, accounting
632 /// for the load factor.
633 /// 2) Ensure new_capacity is a power of two or zero.
634 fn resize(&mut self, new_capacity: usize) {
635 assert!(self.table.size() <= new_capacity);
636 assert!(new_capacity.is_power_of_two() || new_capacity == 0);
638 let mut old_table = replace(&mut self.table, RawTable::new(new_capacity));
639 let old_size = old_table.size();
641 if old_table.capacity() == 0 || old_table.size() == 0 {
646 // Specialization of the other branch.
647 let mut bucket = Bucket::first(&mut old_table);
649 // "So a few of the first shall be last: for many be called,
652 // We'll most likely encounter a few buckets at the beginning that
653 // have their initial buckets near the end of the table. They were
654 // placed at the beginning as the probe wrapped around the table
655 // during insertion. We must skip forward to a bucket that won't
656 // get reinserted too early and won't unfairly steal others spot.
657 // This eliminates the need for robin hood.
659 bucket = match bucket.peek() {
661 if full.distance() == 0 {
662 // This bucket occupies its ideal spot.
663 // It indicates the start of another "cluster".
664 bucket = full.into_bucket();
667 // Leaving this bucket in the last cluster for later.
671 // Encountered a hole between clusters.
678 // This is how the buckets might be laid out in memory:
679 // ($ marks an initialized bucket)
681 // |$$$_$$$$$$_$$$$$|
683 // But we've skipped the entire initial cluster of buckets
684 // and will continue iteration in this order:
687 // ^ wrap around once end is reached
690 // ^ exit once table.size == 0
692 bucket = match bucket.peek() {
694 let h = bucket.hash();
695 let (b, k, v) = bucket.take();
696 self.insert_hashed_ordered(h, k, v);
698 let t = b.table(); // FIXME "lifetime too short".
699 if t.size() == 0 { break }
703 Empty(b) => b.into_bucket()
708 assert_eq!(self.table.size(), old_size);
711 /// Shrinks the capacity of the map as much as possible. It will drop
712 /// down as much as possible while maintaining the internal rules
713 /// and possibly leaving some space in accordance with the resize policy.
718 /// use std::collections::HashMap;
720 /// let mut map: HashMap<int, int> = HashMap::with_capacity(100);
721 /// map.insert(1, 2);
722 /// map.insert(3, 4);
723 /// assert!(map.capacity() >= 100);
724 /// map.shrink_to_fit();
725 /// assert!(map.capacity() >= 2);
727 #[stable(feature = "rust1", since = "1.0.0")]
728 pub fn shrink_to_fit(&mut self) {
729 let min_capacity = self.resize_policy.min_capacity(self.len());
730 let min_capacity = max(min_capacity.next_power_of_two(), INITIAL_CAPACITY);
732 // An invalid value shouldn't make us run out of space.
733 debug_assert!(self.len() <= min_capacity);
735 if self.table.capacity() != min_capacity {
736 let old_table = replace(&mut self.table, RawTable::new(min_capacity));
737 let old_size = old_table.size();
739 // Shrink the table. Naive algorithm for resizing:
740 for (h, k, v) in old_table.into_iter() {
741 self.insert_hashed_nocheck(h, k, v);
744 debug_assert_eq!(self.table.size(), old_size);
748 /// Insert a pre-hashed key-value pair, without first checking
749 /// that there's enough room in the buckets. Returns a reference to the
750 /// newly insert value.
752 /// If the key already exists, the hashtable will be returned untouched
753 /// and a reference to the existing element will be returned.
754 fn insert_hashed_nocheck(&mut self, hash: SafeHash, k: K, v: V) -> &mut V {
755 self.insert_or_replace_with(hash, k, v, |_, _, _| ())
758 fn insert_or_replace_with<'a, F>(&'a mut self,
762 mut found_existing: F)
764 F: FnMut(&mut K, &mut V, V),
766 // Worst case, we'll find one empty bucket among `size + 1` buckets.
767 let size = self.table.size();
768 let mut probe = Bucket::new(&mut self.table, hash);
769 let ib = probe.index();
772 let mut bucket = match probe.peek() {
775 return bucket.put(hash, k, v).into_mut_refs().1;
777 Full(bucket) => bucket
781 if bucket.hash() == hash {
783 if k == *bucket.read_mut().0 {
784 let (bucket_k, bucket_v) = bucket.into_mut_refs();
785 debug_assert!(k == *bucket_k);
786 // Key already exists. Get its reference.
787 found_existing(bucket_k, bucket_v, v);
792 let robin_ib = bucket.index() as int - bucket.distance() as int;
794 if (ib as int) < robin_ib {
795 // Found a luckier bucket than me. Better steal his spot.
796 return robin_hood(bucket, robin_ib as usize, hash, k, v);
799 probe = bucket.next();
800 assert!(probe.index() != ib + size + 1);
804 /// An iterator visiting all keys in arbitrary order.
805 /// Iterator element type is `&'a K`.
810 /// use std::collections::HashMap;
812 /// let mut map = HashMap::new();
813 /// map.insert("a", 1);
814 /// map.insert("b", 2);
815 /// map.insert("c", 3);
817 /// for key in map.keys() {
818 /// println!("{}", key);
821 #[stable(feature = "rust1", since = "1.0.0")]
822 pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
823 fn first<A, B>((a, _): (A, B)) -> A { a }
824 let first: fn((&'a K,&'a V)) -> &'a K = first; // coerce to fn ptr
826 Keys { inner: self.iter().map(first) }
829 /// An iterator visiting all values in arbitrary order.
830 /// Iterator element type is `&'a V`.
835 /// use std::collections::HashMap;
837 /// let mut map = HashMap::new();
838 /// map.insert("a", 1);
839 /// map.insert("b", 2);
840 /// map.insert("c", 3);
842 /// for val in map.values() {
843 /// println!("{}", val);
846 #[stable(feature = "rust1", since = "1.0.0")]
847 pub fn values<'a>(&'a self) -> Values<'a, K, V> {
848 fn second<A, B>((_, b): (A, B)) -> B { b }
849 let second: fn((&'a K,&'a V)) -> &'a V = second; // coerce to fn ptr
851 Values { inner: self.iter().map(second) }
854 /// An iterator visiting all key-value pairs in arbitrary order.
855 /// Iterator element type is `(&'a K, &'a V)`.
860 /// use std::collections::HashMap;
862 /// let mut map = HashMap::new();
863 /// map.insert("a", 1);
864 /// map.insert("b", 2);
865 /// map.insert("c", 3);
867 /// for (key, val) in map.iter() {
868 /// println!("key: {} val: {}", key, val);
871 #[stable(feature = "rust1", since = "1.0.0")]
872 pub fn iter(&self) -> Iter<K, V> {
873 Iter { inner: self.table.iter() }
876 /// An iterator visiting all key-value pairs in arbitrary order,
877 /// with mutable references to the values.
878 /// Iterator element type is `(&'a K, &'a mut V)`.
883 /// use std::collections::HashMap;
885 /// let mut map = HashMap::new();
886 /// map.insert("a", 1);
887 /// map.insert("b", 2);
888 /// map.insert("c", 3);
890 /// // Update all values
891 /// for (_, val) in map.iter_mut() {
895 /// for (key, val) in map.iter() {
896 /// println!("key: {} val: {}", key, val);
899 #[stable(feature = "rust1", since = "1.0.0")]
900 pub fn iter_mut(&mut self) -> IterMut<K, V> {
901 IterMut { inner: self.table.iter_mut() }
904 /// Creates a consuming iterator, that is, one that moves each key-value
905 /// pair out of the map in arbitrary order. The map cannot be used after
911 /// use std::collections::HashMap;
913 /// let mut map = HashMap::new();
914 /// map.insert("a", 1);
915 /// map.insert("b", 2);
916 /// map.insert("c", 3);
918 /// // Not possible with .iter()
919 /// let vec: Vec<(&str, int)> = map.into_iter().collect();
921 #[stable(feature = "rust1", since = "1.0.0")]
922 pub fn into_iter(self) -> IntoIter<K, V> {
923 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
924 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two;
927 inner: self.table.into_iter().map(last_two)
931 /// Gets the given key's corresponding entry in the map for in-place manipulation.
932 #[stable(feature = "rust1", since = "1.0.0")]
933 pub fn entry(&mut self, key: K) -> Entry<K, V> {
937 let hash = self.make_hash(&key);
938 search_entry_hashed(&mut self.table, hash, key)
941 /// Returns the number of elements in the map.
946 /// use std::collections::HashMap;
948 /// let mut a = HashMap::new();
949 /// assert_eq!(a.len(), 0);
950 /// a.insert(1u, "a");
951 /// assert_eq!(a.len(), 1);
953 #[stable(feature = "rust1", since = "1.0.0")]
954 pub fn len(&self) -> usize { self.table.size() }
956 /// Returns true if the map contains no elements.
961 /// use std::collections::HashMap;
963 /// let mut a = HashMap::new();
964 /// assert!(a.is_empty());
965 /// a.insert(1u, "a");
966 /// assert!(!a.is_empty());
969 #[stable(feature = "rust1", since = "1.0.0")]
970 pub fn is_empty(&self) -> bool { self.len() == 0 }
972 /// Clears the map, returning all key-value pairs as an iterator. Keeps the
973 /// allocated memory for reuse.
978 /// use std::collections::HashMap;
980 /// let mut a = HashMap::new();
981 /// a.insert(1u, "a");
982 /// a.insert(2u, "b");
984 /// for (k, v) in a.drain().take(1) {
985 /// assert!(k == 1 || k == 2);
986 /// assert!(v == "a" || v == "b");
989 /// assert!(a.is_empty());
992 #[unstable(feature = "std_misc",
993 reason = "matches collection reform specification, waiting for dust to settle")]
994 pub fn drain(&mut self) -> Drain<K, V> {
995 fn last_two<A, B, C>((_, b, c): (A, B, C)) -> (B, C) { (b, c) }
996 let last_two: fn((SafeHash, K, V)) -> (K, V) = last_two; // coerce to fn pointer
999 inner: self.table.drain().map(last_two),
1003 /// Clears the map, removing all key-value pairs. Keeps the allocated memory
1009 /// use std::collections::HashMap;
1011 /// let mut a = HashMap::new();
1012 /// a.insert(1u, "a");
1014 /// assert!(a.is_empty());
1016 #[stable(feature = "rust1", since = "1.0.0")]
1018 pub fn clear(&mut self) {
1022 /// Returns a reference to the value corresponding to the key.
1024 /// The key may be any borrowed form of the map's key type, but
1025 /// `Hash` and `Eq` on the borrowed form *must* match those for
1031 /// use std::collections::HashMap;
1033 /// let mut map = HashMap::new();
1034 /// map.insert(1u, "a");
1035 /// assert_eq!(map.get(&1), Some(&"a"));
1036 /// assert_eq!(map.get(&2), None);
1038 #[stable(feature = "rust1", since = "1.0.0")]
1039 pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
1040 where Q: Hash<H> + Eq + BorrowFrom<K>
1042 self.search(k).map(|bucket| bucket.into_refs().1)
1045 /// Returns true if the map contains a value for the specified key.
1047 /// The key may be any borrowed form of the map's key type, but
1048 /// `Hash` and `Eq` on the borrowed form *must* match those for
1054 /// use std::collections::HashMap;
1056 /// let mut map = HashMap::new();
1057 /// map.insert(1u, "a");
1058 /// assert_eq!(map.contains_key(&1), true);
1059 /// assert_eq!(map.contains_key(&2), false);
1061 #[stable(feature = "rust1", since = "1.0.0")]
1062 pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
1063 where Q: Hash<H> + Eq + BorrowFrom<K>
1065 self.search(k).is_some()
1068 /// Returns a mutable reference to the value corresponding to the key.
1070 /// The key may be any borrowed form of the map's key type, but
1071 /// `Hash` and `Eq` on the borrowed form *must* match those for
1077 /// use std::collections::HashMap;
1079 /// let mut map = HashMap::new();
1080 /// map.insert(1u, "a");
1081 /// match map.get_mut(&1) {
1082 /// Some(x) => *x = "b",
1085 /// assert_eq!(map[1], "b");
1087 #[stable(feature = "rust1", since = "1.0.0")]
1088 pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
1089 where Q: Hash<H> + Eq + BorrowFrom<K>
1091 self.search_mut(k).map(|bucket| bucket.into_mut_refs().1)
1094 /// Inserts a key-value pair from the map. If the key already had a value
1095 /// present in the map, that value is returned. Otherwise, `None` is returned.
1100 /// use std::collections::HashMap;
1102 /// let mut map = HashMap::new();
1103 /// assert_eq!(map.insert(37u, "a"), None);
1104 /// assert_eq!(map.is_empty(), false);
1106 /// map.insert(37, "b");
1107 /// assert_eq!(map.insert(37, "c"), Some("b"));
1108 /// assert_eq!(map[37], "c");
1110 #[stable(feature = "rust1", since = "1.0.0")]
1111 pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1112 let hash = self.make_hash(&k);
1115 let mut retval = None;
1116 self.insert_or_replace_with(hash, k, v, |_, val_ref, val| {
1117 retval = Some(replace(val_ref, val));
1122 /// Removes a key from the map, returning the value at the key if the key
1123 /// was previously in the map.
1125 /// The key may be any borrowed form of the map's key type, but
1126 /// `Hash` and `Eq` on the borrowed form *must* match those for
1132 /// use std::collections::HashMap;
1134 /// let mut map = HashMap::new();
1135 /// map.insert(1u, "a");
1136 /// assert_eq!(map.remove(&1), Some("a"));
1137 /// assert_eq!(map.remove(&1), None);
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
1141 where Q: Hash<H> + Eq + BorrowFrom<K>
1143 if self.table.size() == 0 {
1147 self.search_mut(k).map(|bucket| pop_internal(bucket).1)
1151 fn search_entry_hashed<'a, K: Eq, V>(table: &'a mut RawTable<K,V>, hash: SafeHash, k: K)
1154 // Worst case, we'll find one empty bucket among `size + 1` buckets.
1155 let size = table.size();
1156 let mut probe = Bucket::new(table, hash);
1157 let ib = probe.index();
1160 let bucket = match probe.peek() {
1163 return Vacant(VacantEntry {
1166 elem: NoElem(bucket),
1169 Full(bucket) => bucket
1173 if bucket.hash() == hash {
1175 if k == *bucket.read().0 {
1176 return Occupied(OccupiedEntry{
1182 let robin_ib = bucket.index() as int - bucket.distance() as int;
1184 if (ib as int) < robin_ib {
1185 // Found a luckier bucket than me. Better steal his spot.
1186 return Vacant(VacantEntry {
1189 elem: NeqElem(bucket, robin_ib as usize),
1193 probe = bucket.next();
1194 assert!(probe.index() != ib + size + 1);
1198 impl<K, V, S, H> PartialEq for HashMap<K, V, S>
1199 where K: Eq + Hash<H>, V: PartialEq,
1200 S: HashState<Hasher=H>,
1201 H: hash::Hasher<Output=u64>
1203 fn eq(&self, other: &HashMap<K, V, S>) -> bool {
1204 if self.len() != other.len() { return false; }
1206 self.iter().all(|(key, value)|
1207 other.get(key).map_or(false, |v| *value == *v)
1212 #[stable(feature = "rust1", since = "1.0.0")]
1213 impl<K, V, S, H> Eq for HashMap<K, V, S>
1214 where K: Eq + Hash<H>, V: Eq,
1215 S: HashState<Hasher=H>,
1216 H: hash::Hasher<Output=u64>
1219 #[stable(feature = "rust1", since = "1.0.0")]
1220 impl<K, V, S, H> Debug for HashMap<K, V, S>
1221 where K: Eq + Hash<H> + Debug, V: Debug,
1222 S: HashState<Hasher=H>,
1223 H: hash::Hasher<Output=u64>
1225 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1226 try!(write!(f, "HashMap {{"));
1228 for (i, (k, v)) in self.iter().enumerate() {
1229 if i != 0 { try!(write!(f, ", ")); }
1230 try!(write!(f, "{:?}: {:?}", *k, *v));
1237 #[stable(feature = "rust1", since = "1.0.0")]
1238 impl<K, V, S, H> Default for HashMap<K, V, S>
1239 where K: Eq + Hash<H>,
1240 S: HashState<Hasher=H> + Default,
1241 H: hash::Hasher<Output=u64>
1243 fn default() -> HashMap<K, V, S> {
1244 HashMap::with_hash_state(Default::default())
1248 #[stable(feature = "rust1", since = "1.0.0")]
1249 impl<K, Q: ?Sized, V, S, H> Index<Q> for HashMap<K, V, S>
1250 where K: Eq + Hash<H>,
1251 Q: Eq + Hash<H> + BorrowFrom<K>,
1252 S: HashState<Hasher=H>,
1253 H: hash::Hasher<Output=u64>
1258 fn index<'a>(&'a self, index: &Q) -> &'a V {
1259 self.get(index).expect("no entry found for key")
1263 #[stable(feature = "rust1", since = "1.0.0")]
1264 impl<K, V, S, H, Q: ?Sized> IndexMut<Q> for HashMap<K, V, S>
1265 where K: Eq + Hash<H>,
1266 Q: Eq + Hash<H> + BorrowFrom<K>,
1267 S: HashState<Hasher=H>,
1268 H: hash::Hasher<Output=u64>
1273 fn index_mut<'a>(&'a mut self, index: &Q) -> &'a mut V {
1274 self.get_mut(index).expect("no entry found for key")
1278 /// HashMap iterator.
1279 #[stable(feature = "rust1", since = "1.0.0")]
1280 pub struct Iter<'a, K: 'a, V: 'a> {
1281 inner: table::Iter<'a, K, V>
1284 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1285 impl<'a, K, V> Clone for Iter<'a, K, V> {
1286 fn clone(&self) -> Iter<'a, K, V> {
1288 inner: self.inner.clone()
1293 /// HashMap mutable values iterator.
1294 #[stable(feature = "rust1", since = "1.0.0")]
1295 pub struct IterMut<'a, K: 'a, V: 'a> {
1296 inner: table::IterMut<'a, K, V>
1299 /// HashMap move iterator.
1300 #[stable(feature = "rust1", since = "1.0.0")]
1301 pub struct IntoIter<K, V> {
1302 inner: iter::Map<table::IntoIter<K, V>, fn((SafeHash, K, V)) -> (K, V)>
1305 /// HashMap keys iterator.
1306 #[stable(feature = "rust1", since = "1.0.0")]
1307 pub struct Keys<'a, K: 'a, V: 'a> {
1308 inner: Map<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.
1321 #[stable(feature = "rust1", since = "1.0.0")]
1322 pub struct Values<'a, K: 'a, V: 'a> {
1323 inner: Map<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(feature = "std_misc",
1337 reason = "matches collection reform specification, waiting for dust to settle")]
1338 pub struct Drain<'a, K: 'a, V: 'a> {
1339 inner: iter::Map<table::Drain<'a, K, V>, fn((SafeHash, K, V)) -> (K, V)>
1342 /// A view into a single occupied location in a HashMap.
1343 #[unstable(feature = "std_misc",
1344 reason = "precise API still being fleshed out")]
1345 pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
1346 elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
1349 /// A view into a single empty location in a HashMap.
1350 #[unstable(feature = "std_misc",
1351 reason = "precise API still being fleshed out")]
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 #[unstable(feature = "std_misc",
1360 reason = "precise API still being fleshed out")]
1361 pub enum Entry<'a, K: 'a, V: 'a> {
1362 /// An occupied Entry.
1363 Occupied(OccupiedEntry<'a, K, V>),
1365 Vacant(VacantEntry<'a, K, V>),
1368 /// Possible states of a VacantEntry.
1369 enum VacantEntryState<K, V, M> {
1370 /// The index is occupied, but the key to insert has precedence,
1371 /// and will kick the current one out on insertion.
1372 NeqElem(FullBucket<K, V, M>, usize),
1373 /// The index is genuinely vacant.
1374 NoElem(EmptyBucket<K, V, M>),
1377 impl<'a, K, V, S, H> IntoIterator for &'a HashMap<K, V, S>
1378 where K: Eq + Hash<H>,
1379 S: HashState<Hasher=H>,
1380 H: hash::Hasher<Output=u64>
1382 type Iter = Iter<'a, K, V>;
1384 fn into_iter(self) -> Iter<'a, K, V> {
1389 impl<'a, K, V, S, H> IntoIterator for &'a mut HashMap<K, V, S>
1390 where K: Eq + Hash<H>,
1391 S: HashState<Hasher=H>,
1392 H: hash::Hasher<Output=u64>
1394 type Iter = IterMut<'a, K, V>;
1396 fn into_iter(mut self) -> IterMut<'a, K, V> {
1401 impl<K, V, S, H> IntoIterator for HashMap<K, V, S>
1402 where K: Eq + Hash<H>,
1403 S: HashState<Hasher=H>,
1404 H: hash::Hasher<Output=u64>
1406 type Iter = IntoIter<K, V>;
1408 fn into_iter(self) -> IntoIter<K, V> {
1413 #[stable(feature = "rust1", since = "1.0.0")]
1414 impl<'a, K, V> Iterator for Iter<'a, K, V> {
1415 type Item = (&'a K, &'a V);
1417 #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
1418 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1420 #[stable(feature = "rust1", since = "1.0.0")]
1421 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
1422 #[inline] fn len(&self) -> usize { self.inner.len() }
1425 #[stable(feature = "rust1", since = "1.0.0")]
1426 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
1427 type Item = (&'a K, &'a mut V);
1429 #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
1430 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1432 #[stable(feature = "rust1", since = "1.0.0")]
1433 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
1434 #[inline] fn len(&self) -> usize { self.inner.len() }
1437 #[stable(feature = "rust1", since = "1.0.0")]
1438 impl<K, V> Iterator for IntoIter<K, V> {
1441 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1442 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1444 #[stable(feature = "rust1", since = "1.0.0")]
1445 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
1446 #[inline] fn len(&self) -> usize { self.inner.len() }
1449 #[stable(feature = "rust1", since = "1.0.0")]
1450 impl<'a, K, V> Iterator for Keys<'a, K, V> {
1453 #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
1454 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1456 #[stable(feature = "rust1", since = "1.0.0")]
1457 impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {
1458 #[inline] fn len(&self) -> usize { self.inner.len() }
1461 #[stable(feature = "rust1", since = "1.0.0")]
1462 impl<'a, K, V> Iterator for Values<'a, K, V> {
1465 #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
1466 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1468 #[stable(feature = "rust1", since = "1.0.0")]
1469 impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {
1470 #[inline] fn len(&self) -> usize { self.inner.len() }
1473 #[stable(feature = "rust1", since = "1.0.0")]
1474 impl<'a, K, V> Iterator for Drain<'a, K, V> {
1477 #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
1478 #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1480 #[stable(feature = "rust1", since = "1.0.0")]
1481 impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
1482 #[inline] fn len(&self) -> usize { self.inner.len() }
1485 #[unstable(feature = "std_misc",
1486 reason = "matches collection reform v2 specification, waiting for dust to settle")]
1487 impl<'a, K, V> Entry<'a, K, V> {
1488 /// Returns a mutable reference to the entry if occupied, or the VacantEntry if vacant.
1489 pub fn get(self) -> Result<&'a mut V, VacantEntry<'a, K, V>> {
1491 Occupied(entry) => Ok(entry.into_mut()),
1492 Vacant(entry) => Err(entry),
1497 impl<'a, K, V> OccupiedEntry<'a, K, V> {
1498 /// Gets a reference to the value in the entry.
1499 #[stable(feature = "rust1", since = "1.0.0")]
1500 pub fn get(&self) -> &V {
1504 /// Gets a mutable reference to the value in the entry.
1505 #[stable(feature = "rust1", since = "1.0.0")]
1506 pub fn get_mut(&mut self) -> &mut V {
1507 self.elem.read_mut().1
1510 /// Converts the OccupiedEntry into a mutable reference to the value in the entry
1511 /// with a lifetime bound to the map itself
1512 #[stable(feature = "rust1", since = "1.0.0")]
1513 pub fn into_mut(self) -> &'a mut V {
1514 self.elem.into_mut_refs().1
1517 /// Sets the value of the entry, and returns the entry's old value
1518 #[stable(feature = "rust1", since = "1.0.0")]
1519 pub fn insert(&mut self, mut value: V) -> V {
1520 let old_value = self.get_mut();
1521 mem::swap(&mut value, old_value);
1525 /// Takes the value out of the entry, and returns it
1526 #[stable(feature = "rust1", since = "1.0.0")]
1527 pub fn remove(self) -> V {
1528 pop_internal(self.elem).1
1532 impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
1533 /// Sets the value of the entry with the VacantEntry's key,
1534 /// and returns a mutable reference to it
1535 #[stable(feature = "rust1", since = "1.0.0")]
1536 pub fn insert(self, value: V) -> &'a mut V {
1538 NeqElem(bucket, ib) => {
1539 robin_hood(bucket, ib, self.hash, self.key, value)
1542 bucket.put(self.hash, self.key, value).into_mut_refs().1
1548 #[stable(feature = "rust1", since = "1.0.0")]
1549 impl<K, V, S, H> FromIterator<(K, V)> for HashMap<K, V, S>
1550 where K: Eq + Hash<H>,
1551 S: HashState<Hasher=H> + Default,
1552 H: hash::Hasher<Output=u64>
1554 fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> HashMap<K, V, S> {
1555 let lower = iter.size_hint().0;
1556 let mut map = HashMap::with_capacity_and_hash_state(lower,
1557 Default::default());
1563 #[stable(feature = "rust1", since = "1.0.0")]
1564 impl<K, V, S, H> Extend<(K, V)> for HashMap<K, V, S>
1565 where K: Eq + Hash<H>,
1566 S: HashState<Hasher=H>,
1567 H: hash::Hasher<Output=u64>
1569 fn extend<T: Iterator<Item=(K, V)>>(&mut self, iter: T) {
1570 for (k, v) in iter {
1577 /// `RandomState` is the default state for `HashMap` types.
1579 /// A particular instance `RandomState` will create the same instances of
1580 /// `Hasher`, but the hashers created by two different `RandomState`
1581 /// instances are unlikely to produce the same result for the same values.
1583 #[unstable(feature = "std_misc",
1584 reason = "hashing an hash maps may be altered")]
1585 pub struct RandomState {
1590 #[unstable(feature = "std_misc",
1591 reason = "hashing an hash maps may be altered")]
1593 /// Construct a new `RandomState` that is initialized with random keys.
1595 #[allow(deprecated)]
1596 pub fn new() -> RandomState {
1597 let mut r = rand::thread_rng();
1598 RandomState { k0: r.gen(), k1: r.gen() }
1602 #[unstable(feature = "std_misc",
1603 reason = "hashing an hash maps may be altered")]
1604 impl HashState for RandomState {
1605 type Hasher = Hasher;
1606 fn hasher(&self) -> Hasher {
1607 Hasher { inner: SipHasher::new_with_keys(self.k0, self.k1) }
1611 #[unstable(feature = "std_misc",
1612 reason = "hashing an hash maps may be altered")]
1613 impl Default for RandomState {
1615 fn default() -> RandomState {
1620 /// A hasher implementation which is generated from `RandomState` instances.
1622 /// This is the default hasher used in a `HashMap` to hash keys. Types do not
1623 /// typically declare an ability to explicitly hash into this particular type,
1624 /// but rather in a `H: hash::Writer` type parameter.
1625 #[unstable(feature = "std_misc",
1626 reason = "hashing an hash maps may be altered")]
1627 pub struct Hasher { inner: SipHasher }
1629 impl hash::Writer for Hasher {
1630 fn write(&mut self, data: &[u8]) { self.inner.write(data) }
1633 impl hash::Hasher for Hasher {
1635 fn reset(&mut self) { self.inner.reset() }
1636 fn finish(&self) -> u64 { self.inner.finish() }
1644 use super::Entry::{Occupied, Vacant};
1645 use iter::{range_inclusive, range_step_inclusive, repeat};
1647 use rand::{weak_rng, Rng};
1650 fn test_create_capacity_zero() {
1651 let mut m = HashMap::with_capacity(0);
1653 assert!(m.insert(1, 1).is_none());
1655 assert!(m.contains_key(&1));
1656 assert!(!m.contains_key(&0));
1661 let mut m = HashMap::new();
1662 assert_eq!(m.len(), 0);
1663 assert!(m.insert(1, 2).is_none());
1664 assert_eq!(m.len(), 1);
1665 assert!(m.insert(2, 4).is_none());
1666 assert_eq!(m.len(), 2);
1667 assert_eq!(*m.get(&1).unwrap(), 2);
1668 assert_eq!(*m.get(&2).unwrap(), 4);
1671 thread_local! { static DROP_VECTOR: RefCell<Vec<int>> = RefCell::new(Vec::new()) }
1673 #[derive(Hash, PartialEq, Eq)]
1679 fn new(k: usize) -> Dropable {
1680 DROP_VECTOR.with(|slot| {
1681 slot.borrow_mut()[k] += 1;
1688 impl Drop for Dropable {
1689 fn drop(&mut self) {
1690 DROP_VECTOR.with(|slot| {
1691 slot.borrow_mut()[self.k] -= 1;
1696 impl Clone for Dropable {
1697 fn clone(&self) -> Dropable {
1698 Dropable::new(self.k)
1704 DROP_VECTOR.with(|slot| {
1705 *slot.borrow_mut() = repeat(0).take(200).collect();
1709 let mut m = HashMap::new();
1711 DROP_VECTOR.with(|v| {
1713 assert_eq!(v.borrow()[i], 0);
1718 let d1 = Dropable::new(i);
1719 let d2 = Dropable::new(i+100);
1723 DROP_VECTOR.with(|v| {
1725 assert_eq!(v.borrow()[i], 1);
1730 let k = Dropable::new(i);
1731 let v = m.remove(&k);
1733 assert!(v.is_some());
1735 DROP_VECTOR.with(|v| {
1736 assert_eq!(v.borrow()[i], 1);
1737 assert_eq!(v.borrow()[i+100], 1);
1741 DROP_VECTOR.with(|v| {
1743 assert_eq!(v.borrow()[i], 0);
1744 assert_eq!(v.borrow()[i+100], 0);
1748 assert_eq!(v.borrow()[i], 1);
1749 assert_eq!(v.borrow()[i+100], 1);
1754 DROP_VECTOR.with(|v| {
1756 assert_eq!(v.borrow()[i], 0);
1762 fn test_move_iter_drops() {
1763 DROP_VECTOR.with(|v| {
1764 *v.borrow_mut() = repeat(0).take(200).collect();
1768 let mut hm = HashMap::new();
1770 DROP_VECTOR.with(|v| {
1772 assert_eq!(v.borrow()[i], 0);
1777 let d1 = Dropable::new(i);
1778 let d2 = Dropable::new(i+100);
1782 DROP_VECTOR.with(|v| {
1784 assert_eq!(v.borrow()[i], 1);
1791 // By the way, ensure that cloning doesn't screw up the dropping.
1795 let mut half = hm.into_iter().take(50);
1797 DROP_VECTOR.with(|v| {
1799 assert_eq!(v.borrow()[i], 1);
1803 for _ in half.by_ref() {}
1805 DROP_VECTOR.with(|v| {
1806 let nk = (0..100).filter(|&i| {
1810 let nv = (0..100).filter(|&i| {
1811 v.borrow()[i+100] == 1
1819 DROP_VECTOR.with(|v| {
1821 assert_eq!(v.borrow()[i], 0);
1827 fn test_empty_pop() {
1828 let mut m: HashMap<int, bool> = HashMap::new();
1829 assert_eq!(m.remove(&0), None);
1833 fn test_lots_of_insertions() {
1834 let mut m = HashMap::new();
1836 // Try this a few times to make sure we never screw up the hashmap's
1839 assert!(m.is_empty());
1841 for i in range_inclusive(1, 1000) {
1842 assert!(m.insert(i, i).is_none());
1844 for j in range_inclusive(1, i) {
1846 assert_eq!(r, Some(&j));
1849 for j in range_inclusive(i+1, 1000) {
1851 assert_eq!(r, None);
1855 for i in range_inclusive(1001, 2000) {
1856 assert!(!m.contains_key(&i));
1860 for i in range_inclusive(1, 1000) {
1861 assert!(m.remove(&i).is_some());
1863 for j in range_inclusive(1, i) {
1864 assert!(!m.contains_key(&j));
1867 for j in range_inclusive(i+1, 1000) {
1868 assert!(m.contains_key(&j));
1872 for i in range_inclusive(1, 1000) {
1873 assert!(!m.contains_key(&i));
1876 for i in range_inclusive(1, 1000) {
1877 assert!(m.insert(i, i).is_none());
1881 for i in range_step_inclusive(1000, 1, -1) {
1882 assert!(m.remove(&i).is_some());
1884 for j in range_inclusive(i, 1000) {
1885 assert!(!m.contains_key(&j));
1888 for j in range_inclusive(1, i-1) {
1889 assert!(m.contains_key(&j));
1896 fn test_find_mut() {
1897 let mut m = HashMap::new();
1898 assert!(m.insert(1, 12).is_none());
1899 assert!(m.insert(2, 8).is_none());
1900 assert!(m.insert(5, 14).is_none());
1902 match m.get_mut(&5) {
1903 None => panic!(), Some(x) => *x = new
1905 assert_eq!(m.get(&5), Some(&new));
1909 fn test_insert_overwrite() {
1910 let mut m = HashMap::new();
1911 assert!(m.insert(1, 2).is_none());
1912 assert_eq!(*m.get(&1).unwrap(), 2);
1913 assert!(!m.insert(1, 3).is_none());
1914 assert_eq!(*m.get(&1).unwrap(), 3);
1918 fn test_insert_conflicts() {
1919 let mut m = HashMap::with_capacity(4);
1920 assert!(m.insert(1, 2).is_none());
1921 assert!(m.insert(5, 3).is_none());
1922 assert!(m.insert(9, 4).is_none());
1923 assert_eq!(*m.get(&9).unwrap(), 4);
1924 assert_eq!(*m.get(&5).unwrap(), 3);
1925 assert_eq!(*m.get(&1).unwrap(), 2);
1929 fn test_conflict_remove() {
1930 let mut m = HashMap::with_capacity(4);
1931 assert!(m.insert(1, 2).is_none());
1932 assert_eq!(*m.get(&1).unwrap(), 2);
1933 assert!(m.insert(5, 3).is_none());
1934 assert_eq!(*m.get(&1).unwrap(), 2);
1935 assert_eq!(*m.get(&5).unwrap(), 3);
1936 assert!(m.insert(9, 4).is_none());
1937 assert_eq!(*m.get(&1).unwrap(), 2);
1938 assert_eq!(*m.get(&5).unwrap(), 3);
1939 assert_eq!(*m.get(&9).unwrap(), 4);
1940 assert!(m.remove(&1).is_some());
1941 assert_eq!(*m.get(&9).unwrap(), 4);
1942 assert_eq!(*m.get(&5).unwrap(), 3);
1946 fn test_is_empty() {
1947 let mut m = HashMap::with_capacity(4);
1948 assert!(m.insert(1, 2).is_none());
1949 assert!(!m.is_empty());
1950 assert!(m.remove(&1).is_some());
1951 assert!(m.is_empty());
1956 let mut m = HashMap::new();
1958 assert_eq!(m.remove(&1), Some(2));
1959 assert_eq!(m.remove(&1), None);
1964 let mut m = HashMap::with_capacity(4);
1966 assert!(m.insert(i, i*2).is_none());
1968 assert_eq!(m.len(), 32);
1970 let mut observed: u32 = 0;
1973 assert_eq!(*v, *k * 2);
1974 observed |= 1 << *k;
1976 assert_eq!(observed, 0xFFFF_FFFF);
1981 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1982 let map: HashMap<_, _> = vec.into_iter().collect();
1983 let keys: Vec<_> = map.keys().cloned().collect();
1984 assert_eq!(keys.len(), 3);
1985 assert!(keys.contains(&1));
1986 assert!(keys.contains(&2));
1987 assert!(keys.contains(&3));
1992 let vec = vec![(1, 'a'), (2, 'b'), (3, 'c')];
1993 let map: HashMap<_, _> = vec.into_iter().collect();
1994 let values: Vec<_> = map.values().cloned().collect();
1995 assert_eq!(values.len(), 3);
1996 assert!(values.contains(&'a'));
1997 assert!(values.contains(&'b'));
1998 assert!(values.contains(&'c'));
2003 let mut m = HashMap::new();
2004 assert!(m.get(&1).is_none());
2008 Some(v) => assert_eq!(*v, 2)
2014 let mut m1 = HashMap::new();
2019 let mut m2 = HashMap::new();
2032 let mut map = HashMap::new();
2033 let empty: HashMap<i32, i32> = HashMap::new();
2038 let map_str = format!("{:?}", map);
2040 assert!(map_str == "HashMap {1: 2, 3: 4}" ||
2041 map_str == "HashMap {3: 4, 1: 2}");
2042 assert_eq!(format!("{:?}", empty), "HashMap {}");
2047 let mut m = HashMap::new();
2049 assert_eq!(m.len(), 0);
2050 assert!(m.is_empty());
2053 let old_cap = m.table.capacity();
2054 while old_cap == m.table.capacity() {
2059 assert_eq!(m.len(), i);
2060 assert!(!m.is_empty());
2064 fn test_behavior_resize_policy() {
2065 let mut m = HashMap::new();
2067 assert_eq!(m.len(), 0);
2068 assert_eq!(m.table.capacity(), 0);
2069 assert!(m.is_empty());
2073 assert!(m.is_empty());
2074 let initial_cap = m.table.capacity();
2075 m.reserve(initial_cap);
2076 let cap = m.table.capacity();
2078 assert_eq!(cap, initial_cap * 2);
2081 for _ in 0..cap * 3 / 4 {
2085 // three quarters full
2087 assert_eq!(m.len(), i);
2088 assert_eq!(m.table.capacity(), cap);
2090 for _ in 0..cap / 4 {
2096 let new_cap = m.table.capacity();
2097 assert_eq!(new_cap, cap * 2);
2099 for _ in 0..cap / 2 - 1 {
2102 assert_eq!(m.table.capacity(), new_cap);
2104 // A little more than one quarter full.
2106 assert_eq!(m.table.capacity(), cap);
2107 // again, a little more than half full
2108 for _ in 0..cap / 2 - 1 {
2114 assert_eq!(m.len(), i);
2115 assert!(!m.is_empty());
2116 assert_eq!(m.table.capacity(), initial_cap);
2120 fn test_reserve_shrink_to_fit() {
2121 let mut m = HashMap::new();
2124 assert!(m.capacity() >= m.len());
2130 let usable_cap = m.capacity();
2131 for i in 128..(128 + 256) {
2133 assert_eq!(m.capacity(), usable_cap);
2136 for i in 100..(128 + 256) {
2137 assert_eq!(m.remove(&i), Some(i));
2141 assert_eq!(m.len(), 100);
2142 assert!(!m.is_empty());
2143 assert!(m.capacity() >= m.len());
2146 assert_eq!(m.remove(&i), Some(i));
2151 assert_eq!(m.len(), 1);
2152 assert!(m.capacity() >= m.len());
2153 assert_eq!(m.remove(&0), Some(0));
2157 fn test_from_iter() {
2158 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2160 let map: HashMap<_, _> = xs.iter().cloned().collect();
2162 for &(k, v) in &xs {
2163 assert_eq!(map.get(&k), Some(&v));
2168 fn test_size_hint() {
2169 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2171 let map: HashMap<_, _> = xs.iter().cloned().collect();
2173 let mut iter = map.iter();
2175 for _ in iter.by_ref().take(3) {}
2177 assert_eq!(iter.size_hint(), (3, Some(3)));
2181 fn test_iter_len() {
2182 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2184 let map: HashMap<_, _> = xs.iter().cloned().collect();
2186 let mut iter = map.iter();
2188 for _ in iter.by_ref().take(3) {}
2190 assert_eq!(iter.len(), 3);
2194 fn test_mut_size_hint() {
2195 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2197 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2199 let mut iter = map.iter_mut();
2201 for _ in iter.by_ref().take(3) {}
2203 assert_eq!(iter.size_hint(), (3, Some(3)));
2207 fn test_iter_mut_len() {
2208 let xs = [(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)];
2210 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2212 let mut iter = map.iter_mut();
2214 for _ in iter.by_ref().take(3) {}
2216 assert_eq!(iter.len(), 3);
2221 let mut map = HashMap::new();
2227 assert_eq!(map[2], 1);
2232 fn test_index_nonexistent() {
2233 let mut map = HashMap::new();
2244 let xs = [(1, 10), (2, 20), (3, 30), (4, 40), (5, 50), (6, 60)];
2246 let mut map: HashMap<_, _> = xs.iter().cloned().collect();
2248 // Existing key (insert)
2249 match map.entry(1) {
2250 Vacant(_) => unreachable!(),
2251 Occupied(mut view) => {
2252 assert_eq!(view.get(), &10);
2253 assert_eq!(view.insert(100), 10);
2256 assert_eq!(map.get(&1).unwrap(), &100);
2257 assert_eq!(map.len(), 6);
2260 // Existing key (update)
2261 match map.entry(2) {
2262 Vacant(_) => unreachable!(),
2263 Occupied(mut view) => {
2264 let v = view.get_mut();
2265 let new_v = (*v) * 10;
2269 assert_eq!(map.get(&2).unwrap(), &200);
2270 assert_eq!(map.len(), 6);
2272 // Existing key (take)
2273 match map.entry(3) {
2274 Vacant(_) => unreachable!(),
2276 assert_eq!(view.remove(), 30);
2279 assert_eq!(map.get(&3), None);
2280 assert_eq!(map.len(), 5);
2283 // Inexistent key (insert)
2284 match map.entry(10) {
2285 Occupied(_) => unreachable!(),
2287 assert_eq!(*view.insert(1000), 1000);
2290 assert_eq!(map.get(&10).unwrap(), &1000);
2291 assert_eq!(map.len(), 6);
2295 fn test_entry_take_doesnt_corrupt() {
2297 fn check(m: &HashMap<isize, ()>) {
2299 assert!(m.contains_key(k),
2300 "{} is in keys() but not in the map?", k);
2304 let mut m = HashMap::new();
2305 let mut rng = weak_rng();
2307 // Populate the map with some items.
2309 let x = rng.gen_range(-10, 10);
2314 let x = rng.gen_range(-10, 10);
2318 println!("{}: remove {}", i, x);