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
13 use self::BucketState::*;
17 use hash::{Hash, Hasher};
18 use iter::{Iterator, count};
19 use kinds::{Copy, Sized, marker};
20 use mem::{min_align_of, size_of};
22 use num::{Int, UnsignedInt};
23 use ops::{Deref, DerefMut, Drop};
25 use option::Option::{Some, None};
26 use ptr::{Unique, PtrExt, copy_nonoverlapping_memory, zero_memory};
28 use rt::heap::{allocate, deallocate};
30 const EMPTY_BUCKET: u64 = 0u64;
32 /// The raw hashtable, providing safe-ish access to the unzipped and highly
33 /// optimized arrays of hashes, keys, and values.
35 /// This design uses less memory and is a lot faster than the naive
36 /// `Vec<Option<u64, K, V>>`, because we don't pay for the overhead of an
37 /// option on every element, and we get a generally more cache-aware design.
39 /// Essential invariants of this structure:
41 /// - if t.hashes[i] == EMPTY_BUCKET, then `Bucket::at_index(&t, i).raw`
42 /// points to 'undefined' contents. Don't read from it. This invariant is
43 /// enforced outside this module with the `EmptyBucket`, `FullBucket`,
44 /// and `SafeHash` types.
46 /// - An `EmptyBucket` is only constructed at an index with
47 /// a hash of EMPTY_BUCKET.
49 /// - A `FullBucket` is only constructed at an index with a
50 /// non-EMPTY_BUCKET hash.
52 /// - A `SafeHash` is only constructed for non-`EMPTY_BUCKET` hash. We get
53 /// around hashes of zero by changing them to 0x8000_0000_0000_0000,
54 /// which will likely map to the same bucket, while not being confused
57 /// - All three "arrays represented by pointers" are the same length:
58 /// `capacity`. This is set at creation and never changes. The arrays
59 /// are unzipped to save space (we don't have to pay for the padding
60 /// between odd sized elements, such as in a map from u64 to u8), and
61 /// be more cache aware (scanning through 8 hashes brings in at most
62 /// 2 cache lines, since they're all right beside each other).
64 /// You can kind of think of this module/data structure as a safe wrapper
65 /// around just the "table" part of the hashtable. It enforces some
66 /// invariants at the type level and employs some performance trickery,
67 /// but in general is just a tricked out `Vec<Option<u64, K, V>>`.
68 #[unsafe_no_drop_flag]
69 pub struct RawTable<K, V> {
73 // Because K/V do not appear directly in any of the types in the struct,
74 // inform rustc that in fact instances of K and V are reachable from here.
75 marker: marker::CovariantType<(K,V)>,
78 struct RawBucket<K, V> {
84 impl<K,V> Copy for RawBucket<K,V> {}
86 pub struct Bucket<K, V, M> {
92 impl<K,V,M:Copy> Copy for Bucket<K,V,M> {}
94 pub struct EmptyBucket<K, V, M> {
100 pub struct FullBucket<K, V, M> {
101 raw: RawBucket<K, V>,
106 pub type EmptyBucketImm<'table, K, V> = EmptyBucket<K, V, &'table RawTable<K, V>>;
107 pub type FullBucketImm<'table, K, V> = FullBucket<K, V, &'table RawTable<K, V>>;
109 pub type EmptyBucketMut<'table, K, V> = EmptyBucket<K, V, &'table mut RawTable<K, V>>;
110 pub type FullBucketMut<'table, K, V> = FullBucket<K, V, &'table mut RawTable<K, V>>;
112 pub enum BucketState<K, V, M> {
113 Empty(EmptyBucket<K, V, M>),
114 Full(FullBucket<K, V, M>),
117 // A GapThenFull encapsulates the state of two consecutive buckets at once.
118 // The first bucket, called the gap, is known to be empty.
119 // The second bucket is full.
120 struct GapThenFull<K, V, M> {
121 gap: EmptyBucket<K, V, ()>,
122 full: FullBucket<K, V, M>,
125 /// A hash that is not zero, since we use a hash of zero to represent empty
127 #[derive(PartialEq, Copy)]
128 pub struct SafeHash {
133 /// Peek at the hash value, which is guaranteed to be non-zero.
135 pub fn inspect(&self) -> u64 { self.hash }
138 /// We need to remove hashes of 0. That's reserved for empty buckets.
139 /// This function wraps up `hash_keyed` to be the only way outside this
140 /// module to generate a SafeHash.
141 pub fn make_hash<Sized? T: Hash<S>, S, H: Hasher<S>>(hasher: &H, t: &T) -> SafeHash {
142 // We need to avoid 0u64 in order to prevent collisions with
143 // EMPTY_HASH. We can maintain our precious uniform distribution
144 // of initial indexes by unconditionally setting the MSB,
145 // effectively reducing 64-bits hashes to 63 bits.
146 SafeHash { hash: 0x8000_0000_0000_0000 | hasher.hash(t) }
149 // `replace` casts a `*u64` to a `*SafeHash`. Since we statically
150 // ensure that a `FullBucket` points to an index with a non-zero hash,
151 // and a `SafeHash` is just a `u64` with a different name, this is
154 // This test ensures that a `SafeHash` really IS the same size as a
155 // `u64`. If you need to change the size of `SafeHash` (and
156 // consequently made this test fail), `replace` needs to be
157 // modified to no longer assume this.
159 fn can_alias_safehash_as_u64() {
160 assert_eq!(size_of::<SafeHash>(), size_of::<u64>())
163 impl<K, V> RawBucket<K, V> {
164 unsafe fn offset(self, count: int) -> RawBucket<K, V> {
166 hash: self.hash.offset(count),
167 key: self.key.offset(count),
168 val: self.val.offset(count),
173 // Buckets hold references to the table.
174 impl<K, V, M> FullBucket<K, V, M> {
175 /// Borrow a reference to the table.
176 pub fn table(&self) -> &M {
179 /// Move out the reference to the table.
180 pub fn into_table(self) -> M {
183 /// Get the raw index.
184 pub fn index(&self) -> uint {
189 impl<K, V, M> EmptyBucket<K, V, M> {
190 /// Borrow a reference to the table.
191 pub fn table(&self) -> &M {
194 /// Move out the reference to the table.
195 pub fn into_table(self) -> M {
200 impl<K, V, M> Bucket<K, V, M> {
201 /// Move out the reference to the table.
202 pub fn into_table(self) -> M {
205 /// Get the raw index.
206 pub fn index(&self) -> uint {
211 impl<K, V, M: Deref<Target=RawTable<K, V>>> Bucket<K, V, M> {
212 pub fn new(table: M, hash: SafeHash) -> Bucket<K, V, M> {
213 Bucket::at_index(table, hash.inspect() as uint)
216 pub fn at_index(table: M, ib_index: uint) -> Bucket<K, V, M> {
217 let ib_index = ib_index & (table.capacity() - 1);
220 table.first_bucket_raw().offset(ib_index as int)
227 pub fn first(table: M) -> Bucket<K, V, M> {
229 raw: table.first_bucket_raw(),
235 /// Reads a bucket at a given index, returning an enum indicating whether
236 /// it's initialized or not. You need to match on this enum to get
237 /// the appropriate types to call most of the other functions in
239 pub fn peek(self) -> BucketState<K, V, M> {
240 match unsafe { *self.raw.hash } {
256 /// Modifies the bucket pointer in place to make it point to the next slot.
257 pub fn next(&mut self) {
258 // Branchless bucket iteration step.
259 // As we reach the end of the table...
260 // We take the current idx: 0111111b
261 // Xor it by its increment: ^ 1000000b
264 // Then AND with the capacity: & 1000000b
266 // to get the backwards offset: 1000000b
267 // ... and it's zero at all other times.
268 let maybe_wraparound_dist = (self.idx ^ (self.idx + 1)) & self.table.capacity();
269 // Finally, we obtain the offset 1 or the offset -cap + 1.
270 let dist = 1i - (maybe_wraparound_dist as int);
275 self.raw = self.raw.offset(dist);
280 impl<K, V, M: Deref<Target=RawTable<K, V>>> EmptyBucket<K, V, M> {
282 pub fn next(self) -> Bucket<K, V, M> {
283 let mut bucket = self.into_bucket();
289 pub fn into_bucket(self) -> Bucket<K, V, M> {
297 pub fn gap_peek(self) -> Option<GapThenFull<K, V, M>> {
298 let gap = EmptyBucket {
304 match self.next().peek() {
316 impl<K, V, M: Deref<Target=RawTable<K, V>> + DerefMut> EmptyBucket<K, V, M> {
317 /// Puts given key and value pair, along with the key's hash,
318 /// into this bucket in the hashtable. Note how `self` is 'moved' into
319 /// this function, because this slot will no longer be empty when
320 /// we return! A `FullBucket` is returned for later use, pointing to
321 /// the newly-filled slot in the hashtable.
323 /// Use `make_hash` to construct a `SafeHash` to pass to this function.
324 pub fn put(mut self, hash: SafeHash, key: K, value: V)
325 -> FullBucket<K, V, M> {
327 *self.raw.hash = hash.inspect();
328 ptr::write(self.raw.key, key);
329 ptr::write(self.raw.val, value);
332 self.table.size += 1;
334 FullBucket { raw: self.raw, idx: self.idx, table: self.table }
338 impl<K, V, M: Deref<Target=RawTable<K, V>>> FullBucket<K, V, M> {
340 pub fn next(self) -> Bucket<K, V, M> {
341 let mut bucket = self.into_bucket();
347 pub fn into_bucket(self) -> Bucket<K, V, M> {
355 /// Get the distance between this bucket and the 'ideal' location
356 /// as determined by the key's hash stored in it.
358 /// In the cited blog posts above, this is called the "distance to
359 /// initial bucket", or DIB. Also known as "probe count".
360 pub fn distance(&self) -> uint {
361 // Calculates the distance one has to travel when going from
362 // `hash mod capacity` onwards to `idx mod capacity`, wrapping around
363 // if the destination is not reached before the end of the table.
364 (self.idx - self.hash().inspect() as uint) & (self.table.capacity() - 1)
368 pub fn hash(&self) -> SafeHash {
376 /// Gets references to the key and value at a given index.
377 pub fn read(&self) -> (&K, &V) {
385 impl<K, V, M: Deref<Target=RawTable<K, V>> + DerefMut> FullBucket<K, V, M> {
386 /// Removes this bucket's key and value from the hashtable.
388 /// This works similarly to `put`, building an `EmptyBucket` out of the
390 pub fn take(mut self) -> (EmptyBucket<K, V, M>, K, V) {
391 let key = self.raw.key as *const K;
392 let val = self.raw.val as *const V;
394 self.table.size -= 1;
397 *self.raw.hash = EMPTY_BUCKET;
410 pub fn replace(&mut self, h: SafeHash, k: K, v: V) -> (SafeHash, K, V) {
412 let old_hash = ptr::replace(self.raw.hash as *mut SafeHash, h);
413 let old_key = ptr::replace(self.raw.key, k);
414 let old_val = ptr::replace(self.raw.val, v);
416 (old_hash, old_key, old_val)
420 /// Gets mutable references to the key and value at a given index.
421 pub fn read_mut(&mut self) -> (&mut K, &mut V) {
429 impl<'t, K, V, M: Deref<Target=RawTable<K, V>> + 't> FullBucket<K, V, M> {
430 /// Exchange a bucket state for immutable references into the table.
431 /// Because the underlying reference to the table is also consumed,
432 /// no further changes to the structure of the table are possible;
433 /// in exchange for this, the returned references have a longer lifetime
434 /// than the references returned by `read()`.
435 pub fn into_refs(self) -> (&'t K, &'t V) {
443 impl<'t, K, V, M: Deref<Target=RawTable<K, V>> + DerefMut + 't> FullBucket<K, V, M> {
444 /// This works similarly to `into_refs`, exchanging a bucket state
445 /// for mutable references into the table.
446 pub fn into_mut_refs(self) -> (&'t mut K, &'t mut V) {
454 impl<K, V, M> BucketState<K, V, M> {
456 pub fn expect_full(self) -> FullBucket<K, V, M> {
459 Empty(..) => panic!("Expected full bucket")
464 impl<K, V, M: Deref<Target=RawTable<K, V>>> GapThenFull<K, V, M> {
466 pub fn full(&self) -> &FullBucket<K, V, M> {
470 pub fn shift(mut self) -> Option<GapThenFull<K, V, M>> {
472 *self.gap.raw.hash = mem::replace(&mut *self.full.raw.hash, EMPTY_BUCKET);
473 copy_nonoverlapping_memory(self.gap.raw.key, self.full.raw.key as *const K, 1);
474 copy_nonoverlapping_memory(self.gap.raw.val, self.full.raw.val as *const V, 1);
477 let FullBucket { raw: prev_raw, idx: prev_idx, .. } = self.full;
479 match self.full.next().peek() {
481 self.gap.raw = prev_raw;
482 self.gap.idx = prev_idx;
494 /// Rounds up to a multiple of a power of two. Returns the closest multiple
495 /// of `target_alignment` that is higher or equal to `unrounded`.
499 /// Panics if `target_alignment` is not a power of two.
500 fn round_up_to_next(unrounded: uint, target_alignment: uint) -> uint {
501 assert!(target_alignment.is_power_of_two());
502 (unrounded + target_alignment - 1) & !(target_alignment - 1)
507 assert_eq!(round_up_to_next(0, 4), 0);
508 assert_eq!(round_up_to_next(1, 4), 4);
509 assert_eq!(round_up_to_next(2, 4), 4);
510 assert_eq!(round_up_to_next(3, 4), 4);
511 assert_eq!(round_up_to_next(4, 4), 4);
512 assert_eq!(round_up_to_next(5, 4), 8);
515 // Returns a tuple of (key_offset, val_offset),
516 // from the start of a mallocated array.
517 fn calculate_offsets(hashes_size: uint,
518 keys_size: uint, keys_align: uint,
521 let keys_offset = round_up_to_next(hashes_size, keys_align);
522 let end_of_keys = keys_offset + keys_size;
524 let vals_offset = round_up_to_next(end_of_keys, vals_align);
526 (keys_offset, vals_offset)
529 // Returns a tuple of (minimum required malloc alignment, hash_offset,
530 // array_size), from the start of a mallocated array.
531 fn calculate_allocation(hash_size: uint, hash_align: uint,
532 keys_size: uint, keys_align: uint,
533 vals_size: uint, vals_align: uint)
534 -> (uint, uint, uint) {
536 let (_, vals_offset) = calculate_offsets(hash_size,
537 keys_size, keys_align,
539 let end_of_vals = vals_offset + vals_size;
541 let min_align = cmp::max(hash_align, cmp::max(keys_align, vals_align));
543 (min_align, hash_offset, end_of_vals)
547 fn test_offset_calculation() {
548 assert_eq!(calculate_allocation(128, 8, 15, 1, 4, 4), (8, 0, 148));
549 assert_eq!(calculate_allocation(3, 1, 2, 1, 1, 1), (1, 0, 6));
550 assert_eq!(calculate_allocation(6, 2, 12, 4, 24, 8), (8, 0, 48));
551 assert_eq!(calculate_offsets(128, 15, 1, 4), (128, 144));
552 assert_eq!(calculate_offsets(3, 2, 1, 1), (3, 5));
553 assert_eq!(calculate_offsets(6, 12, 4, 8), (8, 24));
556 impl<K, V> RawTable<K, V> {
557 /// Does not initialize the buckets. The caller should ensure they,
558 /// at the very least, set every hash to EMPTY_BUCKET.
559 unsafe fn new_uninitialized(capacity: uint) -> RawTable<K, V> {
564 hashes: Unique::null(),
565 marker: marker::CovariantType,
568 // No need for `checked_mul` before a more restrictive check performed
569 // later in this method.
570 let hashes_size = capacity * size_of::<u64>();
571 let keys_size = capacity * size_of::< K >();
572 let vals_size = capacity * size_of::< V >();
574 // Allocating hashmaps is a little tricky. We need to allocate three
575 // arrays, but since we know their sizes and alignments up front,
576 // we just allocate a single array, and then have the subarrays
579 // This is great in theory, but in practice getting the alignment
580 // right is a little subtle. Therefore, calculating offsets has been
581 // factored out into a different function.
582 let (malloc_alignment, hash_offset, size) =
583 calculate_allocation(
584 hashes_size, min_align_of::<u64>(),
585 keys_size, min_align_of::< K >(),
586 vals_size, min_align_of::< V >());
588 // One check for overflow that covers calculation and rounding of size.
589 let size_of_bucket = size_of::<u64>().checked_add(size_of::<K>()).unwrap()
590 .checked_add(size_of::<V>()).unwrap();
591 assert!(size >= capacity.checked_mul(size_of_bucket)
592 .expect("capacity overflow"),
593 "capacity overflow");
595 let buffer = allocate(size, malloc_alignment);
596 if buffer.is_null() { ::alloc::oom() }
598 let hashes = buffer.offset(hash_offset as int) as *mut u64;
603 hashes: Unique(hashes),
604 marker: marker::CovariantType,
608 fn first_bucket_raw(&self) -> RawBucket<K, V> {
609 let hashes_size = self.capacity * size_of::<u64>();
610 let keys_size = self.capacity * size_of::<K>();
612 let buffer = self.hashes.0 as *mut u8;
613 let (keys_offset, vals_offset) = calculate_offsets(hashes_size,
614 keys_size, min_align_of::<K>(),
615 min_align_of::<V>());
620 key: buffer.offset(keys_offset as int) as *mut K,
621 val: buffer.offset(vals_offset as int) as *mut V
626 /// Creates a new raw table from a given capacity. All buckets are
628 #[allow(experimental)]
629 pub fn new(capacity: uint) -> RawTable<K, V> {
631 let ret = RawTable::new_uninitialized(capacity);
632 zero_memory(ret.hashes.0, capacity);
637 /// The hashtable's capacity, similar to a vector's.
638 pub fn capacity(&self) -> uint {
642 /// The number of elements ever `put` in the hashtable, minus the number
643 /// of elements ever `take`n.
644 pub fn size(&self) -> uint {
648 fn raw_buckets(&self) -> RawBuckets<K, V> {
650 raw: self.first_bucket_raw(),
652 self.hashes.0.offset(self.capacity as int)
654 marker: marker::ContravariantLifetime,
658 pub fn iter(&self) -> Iter<K, V> {
660 iter: self.raw_buckets(),
661 elems_left: self.size(),
665 pub fn iter_mut(&mut self) -> IterMut<K, V> {
667 iter: self.raw_buckets(),
668 elems_left: self.size(),
672 pub fn into_iter(self) -> IntoIter<K, V> {
673 let RawBuckets { raw, hashes_end, .. } = self.raw_buckets();
674 // Replace the marker regardless of lifetime bounds on parameters.
678 hashes_end: hashes_end,
679 marker: marker::ContravariantLifetime,
685 pub fn drain(&mut self) -> Drain<K, V> {
686 let RawBuckets { raw, hashes_end, .. } = self.raw_buckets();
687 // Replace the marker regardless of lifetime bounds on parameters.
691 hashes_end: hashes_end,
692 marker: marker::ContravariantLifetime::<'static>,
698 /// Returns an iterator that copies out each entry. Used while the table
699 /// is being dropped.
700 unsafe fn rev_move_buckets(&mut self) -> RevMoveBuckets<K, V> {
701 let raw_bucket = self.first_bucket_raw();
703 raw: raw_bucket.offset(self.capacity as int),
704 hashes_end: raw_bucket.hash,
705 elems_left: self.size,
706 marker: marker::ContravariantLifetime,
711 /// A raw iterator. The basis for some other iterators in this module. Although
712 /// this interface is safe, it's not used outside this module.
713 struct RawBuckets<'a, K, V> {
714 raw: RawBucket<K, V>,
715 hashes_end: *mut u64,
716 marker: marker::ContravariantLifetime<'a>,
719 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
720 impl<'a, K, V> Clone for RawBuckets<'a, K, V> {
721 fn clone(&self) -> RawBuckets<'a, K, V> {
724 hashes_end: self.hashes_end,
725 marker: marker::ContravariantLifetime,
731 impl<'a, K, V> Iterator for RawBuckets<'a, K, V> {
732 type Item = RawBucket<K, V>;
734 fn next(&mut self) -> Option<RawBucket<K, V>> {
735 while self.raw.hash != self.hashes_end {
737 // We are swapping out the pointer to a bucket and replacing
738 // it with the pointer to the next one.
739 let prev = ptr::replace(&mut self.raw, self.raw.offset(1));
740 if *prev.hash != EMPTY_BUCKET {
750 /// An iterator that moves out buckets in reverse order. It leaves the table
751 /// in an inconsistent state and should only be used for dropping
752 /// the table's remaining entries. It's used in the implementation of Drop.
753 struct RevMoveBuckets<'a, K, V> {
754 raw: RawBucket<K, V>,
755 hashes_end: *mut u64,
757 marker: marker::ContravariantLifetime<'a>,
760 impl<'a, K, V> Iterator for RevMoveBuckets<'a, K, V> {
763 fn next(&mut self) -> Option<(K, V)> {
764 if self.elems_left == 0 {
769 debug_assert!(self.raw.hash != self.hashes_end);
772 self.raw = self.raw.offset(-1);
774 if *self.raw.hash != EMPTY_BUCKET {
775 self.elems_left -= 1;
777 ptr::read(self.raw.key as *const K),
778 ptr::read(self.raw.val as *const V)
786 /// Iterator over shared references to entries in a table.
787 pub struct Iter<'a, K: 'a, V: 'a> {
788 iter: RawBuckets<'a, K, V>,
792 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
793 impl<'a, K, V> Clone for Iter<'a, K, V> {
794 fn clone(&self) -> Iter<'a, K, V> {
796 iter: self.iter.clone(),
797 elems_left: self.elems_left
803 /// Iterator over mutable references to entries in a table.
804 pub struct IterMut<'a, K: 'a, V: 'a> {
805 iter: RawBuckets<'a, K, V>,
809 /// Iterator over the entries in a table, consuming the table.
810 pub struct IntoIter<K, V> {
811 table: RawTable<K, V>,
812 iter: RawBuckets<'static, K, V>
815 /// Iterator over the entries in a table, clearing the table.
816 pub struct Drain<'a, K: 'a, V: 'a> {
817 table: &'a mut RawTable<K, V>,
818 iter: RawBuckets<'static, K, V>,
821 impl<'a, K, V> Iterator for Iter<'a, K, V> {
822 type Item = (&'a K, &'a V);
824 fn next(&mut self) -> Option<(&'a K, &'a V)> {
825 self.iter.next().map(|bucket| {
826 self.elems_left -= 1;
834 fn size_hint(&self) -> (uint, Option<uint>) {
835 (self.elems_left, Some(self.elems_left))
839 impl<'a, K, V> Iterator for IterMut<'a, K, V> {
840 type Item = (&'a K, &'a mut V);
842 fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
843 self.iter.next().map(|bucket| {
844 self.elems_left -= 1;
852 fn size_hint(&self) -> (uint, Option<uint>) {
853 (self.elems_left, Some(self.elems_left))
857 impl<K, V> Iterator for IntoIter<K, V> {
858 type Item = (SafeHash, K, V);
860 fn next(&mut self) -> Option<(SafeHash, K, V)> {
861 self.iter.next().map(|bucket| {
862 self.table.size -= 1;
868 ptr::read(bucket.key as *const K),
869 ptr::read(bucket.val as *const V)
875 fn size_hint(&self) -> (uint, Option<uint>) {
876 let size = self.table.size();
881 impl<'a, K: 'a, V: 'a> Iterator for Drain<'a, K, V> {
882 type Item = (SafeHash, K, V);
885 fn next(&mut self) -> Option<(SafeHash, K, V)> {
886 self.iter.next().map(|bucket| {
887 self.table.size -= 1;
891 hash: ptr::replace(bucket.hash, EMPTY_BUCKET),
893 ptr::read(bucket.key as *const K),
894 ptr::read(bucket.val as *const V)
900 fn size_hint(&self) -> (uint, Option<uint>) {
901 let size = self.table.size();
907 impl<'a, K: 'a, V: 'a> Drop for Drain<'a, K, V> {
913 impl<K: Clone, V: Clone> Clone for RawTable<K, V> {
914 fn clone(&self) -> RawTable<K, V> {
916 let mut new_ht = RawTable::new_uninitialized(self.capacity());
919 let cap = self.capacity();
920 let mut new_buckets = Bucket::first(&mut new_ht);
921 let mut buckets = Bucket::first(self);
922 while buckets.index() != cap {
923 match buckets.peek() {
926 let (k, v) = full.read();
927 (full.hash(), k.clone(), v.clone())
929 *new_buckets.raw.hash = h.inspect();
930 ptr::write(new_buckets.raw.key, k);
931 ptr::write(new_buckets.raw.val, v);
934 *new_buckets.raw.hash = EMPTY_BUCKET;
942 new_ht.size = self.size();
950 impl<K, V> Drop for RawTable<K, V> {
952 if self.hashes.0.is_null() {
955 // This is done in reverse because we've likely partially taken
956 // some elements out with `.into_iter()` from the front.
957 // Check if the size is 0, so we don't do a useless scan when
958 // dropping empty tables such as on resize.
959 // Also avoid double drop of elements that have been already moved out.
961 for _ in self.rev_move_buckets() {}
964 let hashes_size = self.capacity * size_of::<u64>();
965 let keys_size = self.capacity * size_of::<K>();
966 let vals_size = self.capacity * size_of::<V>();
967 let (align, _, size) = calculate_allocation(hashes_size, min_align_of::<u64>(),
968 keys_size, min_align_of::<K>(),
969 vals_size, min_align_of::<V>());
972 deallocate(self.hashes.0 as *mut u8, size, align);
973 // Remember how everything was allocated out of one buffer
974 // during initialization? We only need one call to free here.