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 use alloc::heap::{allocate, deallocate, EMPTY};
14 use hash::{Hash, Hasher};
16 use mem::{align_of, size_of};
18 use num::wrapping::OverflowingOps;
19 use ops::{Deref, DerefMut};
20 use ptr::{self, Unique};
21 use collections::hash_state::HashState;
23 use self::BucketState::*;
25 const EMPTY_BUCKET: u64 = 0;
27 /// The raw hashtable, providing safe-ish access to the unzipped and highly
28 /// optimized arrays of hashes, keys, and values.
30 /// This design uses less memory and is a lot faster than the naive
31 /// `Vec<Option<u64, K, V>>`, because we don't pay for the overhead of an
32 /// option on every element, and we get a generally more cache-aware design.
34 /// Essential invariants of this structure:
36 /// - if t.hashes[i] == EMPTY_BUCKET, then `Bucket::at_index(&t, i).raw`
37 /// points to 'undefined' contents. Don't read from it. This invariant is
38 /// enforced outside this module with the `EmptyBucket`, `FullBucket`,
39 /// and `SafeHash` types.
41 /// - An `EmptyBucket` is only constructed at an index with
42 /// a hash of EMPTY_BUCKET.
44 /// - A `FullBucket` is only constructed at an index with a
45 /// non-EMPTY_BUCKET hash.
47 /// - A `SafeHash` is only constructed for non-`EMPTY_BUCKET` hash. We get
48 /// around hashes of zero by changing them to 0x8000_0000_0000_0000,
49 /// which will likely map to the same bucket, while not being confused
52 /// - All three "arrays represented by pointers" are the same length:
53 /// `capacity`. This is set at creation and never changes. The arrays
54 /// are unzipped to save space (we don't have to pay for the padding
55 /// between odd sized elements, such as in a map from u64 to u8), and
56 /// be more cache aware (scanning through 8 hashes brings in at most
57 /// 2 cache lines, since they're all right beside each other).
59 /// You can kind of think of this module/data structure as a safe wrapper
60 /// around just the "table" part of the hashtable. It enforces some
61 /// invariants at the type level and employs some performance trickery,
62 /// but in general is just a tricked out `Vec<Option<u64, K, V>>`.
63 #[unsafe_no_drop_flag]
64 pub struct RawTable<K, V> {
69 // Because K/V do not appear directly in any of the types in the struct,
70 // inform rustc that in fact instances of K and V are reachable from here.
71 marker: marker::PhantomData<(K,V)>,
74 unsafe impl<K: Send, V: Send> Send for RawTable<K, V> {}
75 unsafe impl<K: Sync, V: Sync> Sync for RawTable<K, V> {}
77 struct RawBucket<K, V> {
81 _marker: marker::PhantomData<(K,V)>,
84 impl<K,V> Copy for RawBucket<K,V> {}
85 impl<K,V> Clone for RawBucket<K,V> {
86 fn clone(&self) -> RawBucket<K, V> { *self }
89 pub struct Bucket<K, V, M> {
95 impl<K,V,M:Copy> Copy for Bucket<K,V,M> {}
96 impl<K,V,M:Copy> Clone for Bucket<K,V,M> {
97 fn clone(&self) -> Bucket<K,V,M> { *self }
100 pub struct EmptyBucket<K, V, M> {
101 raw: RawBucket<K, V>,
106 pub struct FullBucket<K, V, M> {
107 raw: RawBucket<K, V>,
112 pub type EmptyBucketImm<'table, K, V> = EmptyBucket<K, V, &'table RawTable<K, V>>;
113 pub type FullBucketImm<'table, K, V> = FullBucket<K, V, &'table RawTable<K, V>>;
115 pub type EmptyBucketMut<'table, K, V> = EmptyBucket<K, V, &'table mut RawTable<K, V>>;
116 pub type FullBucketMut<'table, K, V> = FullBucket<K, V, &'table mut RawTable<K, V>>;
118 pub enum BucketState<K, V, M> {
119 Empty(EmptyBucket<K, V, M>),
120 Full(FullBucket<K, V, M>),
123 // A GapThenFull encapsulates the state of two consecutive buckets at once.
124 // The first bucket, called the gap, is known to be empty.
125 // The second bucket is full.
126 pub struct GapThenFull<K, V, M> {
127 gap: EmptyBucket<K, V, ()>,
128 full: FullBucket<K, V, M>,
131 /// A hash that is not zero, since we use a hash of zero to represent empty
133 #[derive(PartialEq, Copy, Clone)]
134 pub struct SafeHash {
139 /// Peek at the hash value, which is guaranteed to be non-zero.
141 pub fn inspect(&self) -> u64 { self.hash }
144 /// We need to remove hashes of 0. That's reserved for empty buckets.
145 /// This function wraps up `hash_keyed` to be the only way outside this
146 /// module to generate a SafeHash.
147 pub fn make_hash<T: ?Sized, S>(hash_state: &S, t: &T) -> SafeHash
148 where T: Hash, S: HashState
150 let mut state = hash_state.hasher();
152 // We need to avoid 0 in order to prevent collisions with
153 // EMPTY_HASH. We can maintain our precious uniform distribution
154 // of initial indexes by unconditionally setting the MSB,
155 // effectively reducing 64-bits hashes to 63 bits.
156 SafeHash { hash: 0x8000_0000_0000_0000 | state.finish() }
159 // `replace` casts a `*u64` to a `*SafeHash`. Since we statically
160 // ensure that a `FullBucket` points to an index with a non-zero hash,
161 // and a `SafeHash` is just a `u64` with a different name, this is
164 // This test ensures that a `SafeHash` really IS the same size as a
165 // `u64`. If you need to change the size of `SafeHash` (and
166 // consequently made this test fail), `replace` needs to be
167 // modified to no longer assume this.
169 fn can_alias_safehash_as_u64() {
170 assert_eq!(size_of::<SafeHash>(), size_of::<u64>())
173 impl<K, V> RawBucket<K, V> {
174 unsafe fn offset(self, count: isize) -> RawBucket<K, V> {
176 hash: self.hash.offset(count),
177 key: self.key.offset(count),
178 val: self.val.offset(count),
179 _marker: marker::PhantomData,
184 // Buckets hold references to the table.
185 impl<K, V, M> FullBucket<K, V, M> {
186 /// Borrow a reference to the table.
187 pub fn table(&self) -> &M {
190 /// Move out the reference to the table.
191 pub fn into_table(self) -> M {
194 /// Get the raw index.
195 pub fn index(&self) -> usize {
200 impl<K, V, M> EmptyBucket<K, V, M> {
201 /// Borrow a reference to the table.
202 pub fn table(&self) -> &M {
205 /// Move out the reference to the table.
206 pub fn into_table(self) -> M {
211 impl<K, V, M> Bucket<K, V, M> {
212 /// Move out the reference to the table.
213 pub fn into_table(self) -> M {
216 /// Get the raw index.
217 pub fn index(&self) -> usize {
222 impl<K, V, M: Deref<Target=RawTable<K, V>>> Bucket<K, V, M> {
223 pub fn new(table: M, hash: SafeHash) -> Bucket<K, V, M> {
224 Bucket::at_index(table, hash.inspect() as usize)
227 pub fn at_index(table: M, ib_index: usize) -> Bucket<K, V, M> {
228 // if capacity is 0, then the RawBucket will be populated with bogus pointers.
229 // This is an uncommon case though, so avoid it in release builds.
230 debug_assert!(table.capacity() > 0, "Table should have capacity at this point");
231 let ib_index = ib_index & (table.capacity() - 1);
234 table.first_bucket_raw().offset(ib_index as isize)
241 pub fn first(table: M) -> Bucket<K, V, M> {
243 raw: table.first_bucket_raw(),
249 /// Reads a bucket at a given index, returning an enum indicating whether
250 /// it's initialized or not. You need to match on this enum to get
251 /// the appropriate types to call most of the other functions in
253 pub fn peek(self) -> BucketState<K, V, M> {
254 match unsafe { *self.raw.hash } {
270 /// Modifies the bucket pointer in place to make it point to the next slot.
271 pub fn next(&mut self) {
272 // Branchless bucket iteration step.
273 // As we reach the end of the table...
274 // We take the current idx: 0111111b
275 // Xor it by its increment: ^ 1000000b
278 // Then AND with the capacity: & 1000000b
280 // to get the backwards offset: 1000000b
281 // ... and it's zero at all other times.
282 let maybe_wraparound_dist = (self.idx ^ (self.idx + 1)) & self.table.capacity();
283 // Finally, we obtain the offset 1 or the offset -cap + 1.
284 let dist = 1 - (maybe_wraparound_dist as isize);
289 self.raw = self.raw.offset(dist);
294 impl<K, V, M: Deref<Target=RawTable<K, V>>> EmptyBucket<K, V, M> {
296 pub fn next(self) -> Bucket<K, V, M> {
297 let mut bucket = self.into_bucket();
303 pub fn into_bucket(self) -> Bucket<K, V, M> {
311 pub fn gap_peek(self) -> Option<GapThenFull<K, V, M>> {
312 let gap = EmptyBucket {
318 match self.next().peek() {
330 impl<K, V, M: Deref<Target=RawTable<K, V>> + DerefMut> EmptyBucket<K, V, M> {
331 /// Puts given key and value pair, along with the key's hash,
332 /// into this bucket in the hashtable. Note how `self` is 'moved' into
333 /// this function, because this slot will no longer be empty when
334 /// we return! A `FullBucket` is returned for later use, pointing to
335 /// the newly-filled slot in the hashtable.
337 /// Use `make_hash` to construct a `SafeHash` to pass to this function.
338 pub fn put(mut self, hash: SafeHash, key: K, value: V)
339 -> FullBucket<K, V, M> {
341 *self.raw.hash = hash.inspect();
342 ptr::write(self.raw.key, key);
343 ptr::write(self.raw.val, value);
346 self.table.size += 1;
348 FullBucket { raw: self.raw, idx: self.idx, table: self.table }
352 impl<K, V, M: Deref<Target=RawTable<K, V>>> FullBucket<K, V, M> {
354 pub fn next(self) -> Bucket<K, V, M> {
355 let mut bucket = self.into_bucket();
361 pub fn into_bucket(self) -> Bucket<K, V, M> {
369 /// Get the distance between this bucket and the 'ideal' location
370 /// as determined by the key's hash stored in it.
372 /// In the cited blog posts above, this is called the "distance to
373 /// initial bucket", or DIB. Also known as "probe count".
374 pub fn distance(&self) -> usize {
375 // Calculates the distance one has to travel when going from
376 // `hash mod capacity` onwards to `idx mod capacity`, wrapping around
377 // if the destination is not reached before the end of the table.
378 (self.idx.wrapping_sub(self.hash().inspect() as usize)) & (self.table.capacity() - 1)
382 pub fn hash(&self) -> SafeHash {
390 /// Gets references to the key and value at a given index.
391 pub fn read(&self) -> (&K, &V) {
399 impl<K, V, M: Deref<Target=RawTable<K, V>> + DerefMut> FullBucket<K, V, M> {
400 /// Removes this bucket's key and value from the hashtable.
402 /// This works similarly to `put`, building an `EmptyBucket` out of the
404 pub fn take(mut self) -> (EmptyBucket<K, V, M>, K, V) {
405 self.table.size -= 1;
408 *self.raw.hash = EMPTY_BUCKET;
415 ptr::read(self.raw.key),
416 ptr::read(self.raw.val)
421 pub fn replace(&mut self, h: SafeHash, k: K, v: V) -> (SafeHash, K, V) {
423 let old_hash = ptr::replace(self.raw.hash as *mut SafeHash, h);
424 let old_key = ptr::replace(self.raw.key, k);
425 let old_val = ptr::replace(self.raw.val, v);
427 (old_hash, old_key, old_val)
431 /// Gets mutable references to the key and value at a given index.
432 pub fn read_mut(&mut self) -> (&mut K, &mut V) {
440 impl<'t, K, V, M: Deref<Target=RawTable<K, V>> + 't> FullBucket<K, V, M> {
441 /// Exchange a bucket state for immutable references into the table.
442 /// Because the underlying reference to the table is also consumed,
443 /// no further changes to the structure of the table are possible;
444 /// in exchange for this, the returned references have a longer lifetime
445 /// than the references returned by `read()`.
446 pub fn into_refs(self) -> (&'t K, &'t V) {
454 impl<'t, K, V, M: Deref<Target=RawTable<K, V>> + DerefMut + 't> FullBucket<K, V, M> {
455 /// This works similarly to `into_refs`, exchanging a bucket state
456 /// for mutable references into the table.
457 pub fn into_mut_refs(self) -> (&'t mut K, &'t mut V) {
465 impl<K, V, M> BucketState<K, V, M> {
467 pub fn expect_full(self) -> FullBucket<K, V, M> {
470 Empty(..) => panic!("Expected full bucket")
475 impl<K, V, M: Deref<Target=RawTable<K, V>>> GapThenFull<K, V, M> {
477 pub fn full(&self) -> &FullBucket<K, V, M> {
481 pub fn shift(mut self) -> Option<GapThenFull<K, V, M>> {
483 *self.gap.raw.hash = mem::replace(&mut *self.full.raw.hash, EMPTY_BUCKET);
484 ptr::copy_nonoverlapping(self.full.raw.key, self.gap.raw.key, 1);
485 ptr::copy_nonoverlapping(self.full.raw.val, self.gap.raw.val, 1);
488 let FullBucket { raw: prev_raw, idx: prev_idx, .. } = self.full;
490 match self.full.next().peek() {
492 self.gap.raw = prev_raw;
493 self.gap.idx = prev_idx;
505 /// Rounds up to a multiple of a power of two. Returns the closest multiple
506 /// of `target_alignment` that is higher or equal to `unrounded`.
510 /// Panics if `target_alignment` is not a power of two.
512 fn round_up_to_next(unrounded: usize, target_alignment: usize) -> usize {
513 assert!(target_alignment.is_power_of_two());
514 (unrounded + target_alignment - 1) & !(target_alignment - 1)
519 assert_eq!(round_up_to_next(0, 4), 0);
520 assert_eq!(round_up_to_next(1, 4), 4);
521 assert_eq!(round_up_to_next(2, 4), 4);
522 assert_eq!(round_up_to_next(3, 4), 4);
523 assert_eq!(round_up_to_next(4, 4), 4);
524 assert_eq!(round_up_to_next(5, 4), 8);
527 // Returns a tuple of (key_offset, val_offset),
528 // from the start of a mallocated array.
530 fn calculate_offsets(hashes_size: usize,
531 keys_size: usize, keys_align: usize,
533 -> (usize, usize, bool) {
534 let keys_offset = round_up_to_next(hashes_size, keys_align);
535 let (end_of_keys, oflo) = keys_offset.overflowing_add(keys_size);
537 let vals_offset = round_up_to_next(end_of_keys, vals_align);
539 (keys_offset, vals_offset, oflo)
542 // Returns a tuple of (minimum required malloc alignment, hash_offset,
543 // array_size), from the start of a mallocated array.
544 fn calculate_allocation(hash_size: usize, hash_align: usize,
545 keys_size: usize, keys_align: usize,
546 vals_size: usize, vals_align: usize)
547 -> (usize, usize, usize, bool) {
549 let (_, vals_offset, oflo) = calculate_offsets(hash_size,
550 keys_size, keys_align,
552 let (end_of_vals, oflo2) = vals_offset.overflowing_add(vals_size);
554 let align = cmp::max(hash_align, cmp::max(keys_align, vals_align));
556 (align, hash_offset, end_of_vals, oflo || oflo2)
560 fn test_offset_calculation() {
561 assert_eq!(calculate_allocation(128, 8, 15, 1, 4, 4), (8, 0, 148, false));
562 assert_eq!(calculate_allocation(3, 1, 2, 1, 1, 1), (1, 0, 6, false));
563 assert_eq!(calculate_allocation(6, 2, 12, 4, 24, 8), (8, 0, 48, false));
564 assert_eq!(calculate_offsets(128, 15, 1, 4), (128, 144, false));
565 assert_eq!(calculate_offsets(3, 2, 1, 1), (3, 5, false));
566 assert_eq!(calculate_offsets(6, 12, 4, 8), (8, 24, false));
569 impl<K, V> RawTable<K, V> {
570 /// Does not initialize the buckets. The caller should ensure they,
571 /// at the very least, set every hash to EMPTY_BUCKET.
572 unsafe fn new_uninitialized(capacity: usize) -> RawTable<K, V> {
577 hashes: Unique::new(EMPTY as *mut u64),
578 marker: marker::PhantomData,
582 // No need for `checked_mul` before a more restrictive check performed
583 // later in this method.
584 let hashes_size = capacity * size_of::<u64>();
585 let keys_size = capacity * size_of::< K >();
586 let vals_size = capacity * size_of::< V >();
588 // Allocating hashmaps is a little tricky. We need to allocate three
589 // arrays, but since we know their sizes and alignments up front,
590 // we just allocate a single array, and then have the subarrays
593 // This is great in theory, but in practice getting the alignment
594 // right is a little subtle. Therefore, calculating offsets has been
595 // factored out into a different function.
596 let (malloc_alignment, hash_offset, size, oflo) =
597 calculate_allocation(
598 hashes_size, align_of::<u64>(),
599 keys_size, align_of::< K >(),
600 vals_size, align_of::< V >());
602 assert!(!oflo, "capacity overflow");
604 // One check for overflow that covers calculation and rounding of size.
605 let size_of_bucket = size_of::<u64>().checked_add(size_of::<K>()).unwrap()
606 .checked_add(size_of::<V>()).unwrap();
607 assert!(size >= capacity.checked_mul(size_of_bucket)
608 .expect("capacity overflow"),
609 "capacity overflow");
611 let buffer = allocate(size, malloc_alignment);
612 if buffer.is_null() { ::alloc::oom() }
614 let hashes = buffer.offset(hash_offset as isize) as *mut u64;
619 hashes: Unique::new(hashes),
620 marker: marker::PhantomData,
624 fn first_bucket_raw(&self) -> RawBucket<K, V> {
625 let hashes_size = self.capacity * size_of::<u64>();
626 let keys_size = self.capacity * size_of::<K>();
628 let buffer = *self.hashes as *mut u8;
629 let (keys_offset, vals_offset, oflo) =
630 calculate_offsets(hashes_size,
631 keys_size, align_of::<K>(),
633 debug_assert!(!oflo, "capacity overflow");
637 key: buffer.offset(keys_offset as isize) as *mut K,
638 val: buffer.offset(vals_offset as isize) as *mut V,
639 _marker: marker::PhantomData,
644 /// Creates a new raw table from a given capacity. All buckets are
646 pub fn new(capacity: usize) -> RawTable<K, V> {
648 let ret = RawTable::new_uninitialized(capacity);
649 ptr::write_bytes(*ret.hashes, 0, capacity);
654 /// The hashtable's capacity, similar to a vector's.
655 pub fn capacity(&self) -> usize {
659 /// The number of elements ever `put` in the hashtable, minus the number
660 /// of elements ever `take`n.
661 pub fn size(&self) -> usize {
665 fn raw_buckets(&self) -> RawBuckets<K, V> {
667 raw: self.first_bucket_raw(),
669 self.hashes.offset(self.capacity as isize)
671 marker: marker::PhantomData,
675 pub fn iter(&self) -> Iter<K, V> {
677 iter: self.raw_buckets(),
678 elems_left: self.size(),
682 pub fn iter_mut(&mut self) -> IterMut<K, V> {
684 iter: self.raw_buckets(),
685 elems_left: self.size(),
689 pub fn into_iter(self) -> IntoIter<K, V> {
690 let RawBuckets { raw, hashes_end, .. } = self.raw_buckets();
691 // Replace the marker regardless of lifetime bounds on parameters.
695 hashes_end: hashes_end,
696 marker: marker::PhantomData,
702 pub fn drain(&mut self) -> Drain<K, V> {
703 let RawBuckets { raw, hashes_end, .. } = self.raw_buckets();
704 // Replace the marker regardless of lifetime bounds on parameters.
708 hashes_end: hashes_end,
709 marker: marker::PhantomData,
715 /// Returns an iterator that copies out each entry. Used while the table
716 /// is being dropped.
717 unsafe fn rev_move_buckets(&mut self) -> RevMoveBuckets<K, V> {
718 let raw_bucket = self.first_bucket_raw();
720 raw: raw_bucket.offset(self.capacity as isize),
721 hashes_end: raw_bucket.hash,
722 elems_left: self.size,
723 marker: marker::PhantomData,
728 /// A raw iterator. The basis for some other iterators in this module. Although
729 /// this interface is safe, it's not used outside this module.
730 struct RawBuckets<'a, K, V> {
731 raw: RawBucket<K, V>,
732 hashes_end: *mut u64,
734 // Strictly speaking, this should be &'a (K,V), but that would
735 // require that K:'a, and we often use RawBuckets<'static...> for
736 // move iterations, so that messes up a lot of other things. So
737 // just use `&'a (K,V)` as this is not a publicly exposed type
739 marker: marker::PhantomData<&'a ()>,
742 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
743 impl<'a, K, V> Clone for RawBuckets<'a, K, V> {
744 fn clone(&self) -> RawBuckets<'a, K, V> {
747 hashes_end: self.hashes_end,
748 marker: marker::PhantomData,
754 impl<'a, K, V> Iterator for RawBuckets<'a, K, V> {
755 type Item = RawBucket<K, V>;
757 fn next(&mut self) -> Option<RawBucket<K, V>> {
758 while self.raw.hash != self.hashes_end {
760 // We are swapping out the pointer to a bucket and replacing
761 // it with the pointer to the next one.
762 let prev = ptr::replace(&mut self.raw, self.raw.offset(1));
763 if *prev.hash != EMPTY_BUCKET {
773 /// An iterator that moves out buckets in reverse order. It leaves the table
774 /// in an inconsistent state and should only be used for dropping
775 /// the table's remaining entries. It's used in the implementation of Drop.
776 struct RevMoveBuckets<'a, K, V> {
777 raw: RawBucket<K, V>,
778 hashes_end: *mut u64,
781 // As above, `&'a (K,V)` would seem better, but we often use
782 // 'static for the lifetime, and this is not a publicly exposed
784 marker: marker::PhantomData<&'a ()>,
787 impl<'a, K, V> Iterator for RevMoveBuckets<'a, K, V> {
790 fn next(&mut self) -> Option<(K, V)> {
791 if self.elems_left == 0 {
796 debug_assert!(self.raw.hash != self.hashes_end);
799 self.raw = self.raw.offset(-1);
801 if *self.raw.hash != EMPTY_BUCKET {
802 self.elems_left -= 1;
804 ptr::read(self.raw.key),
805 ptr::read(self.raw.val)
813 /// Iterator over shared references to entries in a table.
814 pub struct Iter<'a, K: 'a, V: 'a> {
815 iter: RawBuckets<'a, K, V>,
819 unsafe impl<'a, K: Sync, V: Sync> Sync for Iter<'a, K, V> {}
820 unsafe impl<'a, K: Sync, V: Sync> Send for Iter<'a, K, V> {}
822 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
823 impl<'a, K, V> Clone for Iter<'a, K, V> {
824 fn clone(&self) -> Iter<'a, K, V> {
826 iter: self.iter.clone(),
827 elems_left: self.elems_left
833 /// Iterator over mutable references to entries in a table.
834 pub struct IterMut<'a, K: 'a, V: 'a> {
835 iter: RawBuckets<'a, K, V>,
839 unsafe impl<'a, K: Sync, V: Sync> Sync for IterMut<'a, K, V> {}
840 // Both K: Sync and K: Send are correct for IterMut's Send impl,
841 // but Send is the more useful bound
842 unsafe impl<'a, K: Send, V: Send> Send for IterMut<'a, K, V> {}
844 /// Iterator over the entries in a table, consuming the table.
845 pub struct IntoIter<K, V> {
846 table: RawTable<K, V>,
847 iter: RawBuckets<'static, K, V>
850 unsafe impl<K: Sync, V: Sync> Sync for IntoIter<K, V> {}
851 unsafe impl<K: Send, V: Send> Send for IntoIter<K, V> {}
853 /// Iterator over the entries in a table, clearing the table.
854 pub struct Drain<'a, K: 'a, V: 'a> {
855 table: &'a mut RawTable<K, V>,
856 iter: RawBuckets<'static, K, V>,
859 unsafe impl<'a, K: Sync, V: Sync> Sync for Drain<'a, K, V> {}
860 unsafe impl<'a, K: Send, V: Send> Send for Drain<'a, K, V> {}
862 impl<'a, K, V> Iterator for Iter<'a, K, V> {
863 type Item = (&'a K, &'a V);
865 fn next(&mut self) -> Option<(&'a K, &'a V)> {
866 self.iter.next().map(|bucket| {
867 self.elems_left -= 1;
875 fn size_hint(&self) -> (usize, Option<usize>) {
876 (self.elems_left, Some(self.elems_left))
879 impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {
880 fn len(&self) -> usize { self.elems_left }
883 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
884 type Item = (&'a K, &'a mut V);
886 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
887 self.iter.next().map(|bucket| {
888 self.elems_left -= 1;
896 fn size_hint(&self) -> (usize, Option<usize>) {
897 (self.elems_left, Some(self.elems_left))
900 impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
901 fn len(&self) -> usize { self.elems_left }
904 impl<K, V> Iterator for IntoIter<K, V> {
905 type Item = (SafeHash, K, V);
907 fn next(&mut self) -> Option<(SafeHash, K, V)> {
908 self.iter.next().map(|bucket| {
909 self.table.size -= 1;
915 ptr::read(bucket.key),
916 ptr::read(bucket.val)
922 fn size_hint(&self) -> (usize, Option<usize>) {
923 let size = self.table.size();
927 impl<K, V> ExactSizeIterator for IntoIter<K, V> {
928 fn len(&self) -> usize { self.table.size() }
931 impl<'a, K, V> Iterator for Drain<'a, K, V> {
932 type Item = (SafeHash, K, V);
935 fn next(&mut self) -> Option<(SafeHash, K, V)> {
936 self.iter.next().map(|bucket| {
937 self.table.size -= 1;
941 hash: ptr::replace(bucket.hash, EMPTY_BUCKET),
943 ptr::read(bucket.key),
944 ptr::read(bucket.val)
950 fn size_hint(&self) -> (usize, Option<usize>) {
951 let size = self.table.size();
955 impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
956 fn len(&self) -> usize { self.table.size() }
959 impl<'a, K: 'a, V: 'a> Drop for Drain<'a, K, V> {
965 impl<K: Clone, V: Clone> Clone for RawTable<K, V> {
966 fn clone(&self) -> RawTable<K, V> {
968 let mut new_ht = RawTable::new_uninitialized(self.capacity());
971 let cap = self.capacity();
972 let mut new_buckets = Bucket::first(&mut new_ht);
973 let mut buckets = Bucket::first(self);
974 while buckets.index() != cap {
975 match buckets.peek() {
978 let (k, v) = full.read();
979 (full.hash(), k.clone(), v.clone())
981 *new_buckets.raw.hash = h.inspect();
982 ptr::write(new_buckets.raw.key, k);
983 ptr::write(new_buckets.raw.val, v);
986 *new_buckets.raw.hash = EMPTY_BUCKET;
994 new_ht.size = self.size();
1001 impl<K, V> Drop for RawTable<K, V> {
1002 #[unsafe_destructor_blind_to_params]
1003 fn drop(&mut self) {
1004 if self.capacity == 0 || self.capacity == mem::POST_DROP_USIZE {
1008 // This is done in reverse because we've likely partially taken
1009 // some elements out with `.into_iter()` from the front.
1010 // Check if the size is 0, so we don't do a useless scan when
1011 // dropping empty tables such as on resize.
1012 // Also avoid double drop of elements that have been already moved out.
1014 for _ in self.rev_move_buckets() {}
1017 let hashes_size = self.capacity * size_of::<u64>();
1018 let keys_size = self.capacity * size_of::<K>();
1019 let vals_size = self.capacity * size_of::<V>();
1020 let (align, _, size, oflo) =
1021 calculate_allocation(hashes_size, align_of::<u64>(),
1022 keys_size, align_of::<K>(),
1023 vals_size, align_of::<V>());
1025 debug_assert!(!oflo, "should be impossible");
1028 deallocate(*self.hashes as *mut u8, size, align);
1029 // Remember how everything was allocated out of one buffer
1030 // during initialization? We only need one call to free here.