a00bdd176d
-- fa894a667a3bebbe479539c8d5e829beebf36c27 by Abseil Team <absl-team@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 216855907 -- 59e0a42fa9045eb164573b82ce625248bd9999f3 by Jon Cohen <cohenjon@google.com>: Some edits to the documentation for absl::Hash as I was reading through it. Itemized changes: * implement -> implements for grammar * Fix an incomplete sentence * specify *any* type T as opposed to *a* type T ? this is just the language I tend to see for these sorts of concepts in math and makes it more clear that we?re talking about a set of all types T satisfying these constraints * add arguments to comine() and combine_contiguous() ? this was mostly because for hash_continuous there was a reference to `size` elements without any mention of what `size` was. PiperOrigin-RevId: 216766923 -- c2a744d0f70ec5a079c22502b7a7ca72805a29dc by Shaindel Schwartz <shaindel@google.com>: Remove unneeded include. PiperOrigin-RevId: 216703710 -- ad22fc4e3d236f7bd354b61e0fa37ea524a7cf5e by Shaindel Schwartz <shaindel@google.com>: Fix typos. PiperOrigin-RevId: 216699071 GitOrigin-RevId: fa894a667a3bebbe479539c8d5e829beebf36c27 Change-Id: I35c8d8be66043aad9f17bbb867e69acb770bd1b0
1915 lines
66 KiB
C++
1915 lines
66 KiB
C++
// Copyright 2018 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// An open-addressing
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// hashtable with quadratic probing.
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//
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// This is a low level hashtable on top of which different interfaces can be
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// implemented, like flat_hash_set, node_hash_set, string_hash_set, etc.
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//
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// The table interface is similar to that of std::unordered_set. Notable
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// differences are that most member functions support heterogeneous keys when
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// BOTH the hash and eq functions are marked as transparent. They do so by
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// providing a typedef called `is_transparent`.
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//
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// When heterogeneous lookup is enabled, functions that take key_type act as if
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// they have an overload set like:
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//
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// iterator find(const key_type& key);
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// template <class K>
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// iterator find(const K& key);
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//
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// size_type erase(const key_type& key);
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// template <class K>
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// size_type erase(const K& key);
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//
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// std::pair<iterator, iterator> equal_range(const key_type& key);
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// template <class K>
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// std::pair<iterator, iterator> equal_range(const K& key);
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//
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// When heterogeneous lookup is disabled, only the explicit `key_type` overloads
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// exist.
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//
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// find() also supports passing the hash explicitly:
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//
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// iterator find(const key_type& key, size_t hash);
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// template <class U>
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// iterator find(const U& key, size_t hash);
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//
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// In addition the pointer to element and iterator stability guarantees are
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// weaker: all iterators and pointers are invalidated after a new element is
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// inserted.
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//
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// IMPLEMENTATION DETAILS
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//
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// The table stores elements inline in a slot array. In addition to the slot
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// array the table maintains some control state per slot. The extra state is one
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// byte per slot and stores empty or deleted marks, or alternatively 7 bits from
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// the hash of an occupied slot. The table is split into logical groups of
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// slots, like so:
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//
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// Group 1 Group 2 Group 3
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// +---------------+---------------+---------------+
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// | | | | | | | | | | | | | | | | | | | | | | | | |
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// +---------------+---------------+---------------+
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//
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// On lookup the hash is split into two parts:
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// - H2: 7 bits (those stored in the control bytes)
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// - H1: the rest of the bits
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// The groups are probed using H1. For each group the slots are matched to H2 in
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// parallel. Because H2 is 7 bits (128 states) and the number of slots per group
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// is low (8 or 16) in almost all cases a match in H2 is also a lookup hit.
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//
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// On insert, once the right group is found (as in lookup), its slots are
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// filled in order.
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//
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// On erase a slot is cleared. In case the group did not have any empty slots
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// before the erase, the erased slot is marked as deleted.
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//
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// Groups without empty slots (but maybe with deleted slots) extend the probe
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// sequence. The probing algorithm is quadratic. Given N the number of groups,
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// the probing function for the i'th probe is:
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//
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// P(0) = H1 % N
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//
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// P(i) = (P(i - 1) + i) % N
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//
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// This probing function guarantees that after N probes, all the groups of the
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// table will be probed exactly once.
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#ifndef ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
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#define ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
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#ifndef SWISSTABLE_HAVE_SSE2
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#ifdef __SSE2__
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#define SWISSTABLE_HAVE_SSE2 1
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#else
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#define SWISSTABLE_HAVE_SSE2 0
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#endif
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#endif
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#ifndef SWISSTABLE_HAVE_SSSE3
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#ifdef __SSSE3__
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#define SWISSTABLE_HAVE_SSSE3 1
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#else
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#define SWISSTABLE_HAVE_SSSE3 0
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#endif
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#endif
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#if SWISSTABLE_HAVE_SSSE3 && !SWISSTABLE_HAVE_SSE2
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#error "Bad configuration!"
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#endif
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#if SWISSTABLE_HAVE_SSE2
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#include <x86intrin.h>
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#endif
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#include <algorithm>
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#include <cmath>
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#include <cstdint>
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#include <cstring>
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#include <iterator>
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#include <limits>
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#include <memory>
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#include <tuple>
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#include <type_traits>
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#include <utility>
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#include "absl/base/internal/bits.h"
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#include "absl/base/internal/endian.h"
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#include "absl/base/port.h"
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#include "absl/container/internal/compressed_tuple.h"
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#include "absl/container/internal/container_memory.h"
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#include "absl/container/internal/hash_policy_traits.h"
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#include "absl/container/internal/hashtable_debug_hooks.h"
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#include "absl/container/internal/layout.h"
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#include "absl/memory/memory.h"
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#include "absl/meta/type_traits.h"
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#include "absl/types/optional.h"
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#include "absl/utility/utility.h"
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namespace absl {
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namespace container_internal {
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template <size_t Width>
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class probe_seq {
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public:
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probe_seq(size_t hash, size_t mask) {
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assert(((mask + 1) & mask) == 0 && "not a mask");
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mask_ = mask;
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offset_ = hash & mask_;
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}
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size_t offset() const { return offset_; }
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size_t offset(size_t i) const { return (offset_ + i) & mask_; }
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void next() {
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index_ += Width;
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offset_ += index_;
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offset_ &= mask_;
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}
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// 0-based probe index. The i-th probe in the probe sequence.
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size_t index() const { return index_; }
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private:
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size_t mask_;
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size_t offset_;
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size_t index_ = 0;
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};
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template <class ContainerKey, class Hash, class Eq>
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struct RequireUsableKey {
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template <class PassedKey, class... Args>
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std::pair<
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decltype(std::declval<const Hash&>()(std::declval<const PassedKey&>())),
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decltype(std::declval<const Eq&>()(std::declval<const ContainerKey&>(),
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std::declval<const PassedKey&>()))>*
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operator()(const PassedKey&, const Args&...) const;
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};
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template <class E, class Policy, class Hash, class Eq, class... Ts>
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struct IsDecomposable : std::false_type {};
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template <class Policy, class Hash, class Eq, class... Ts>
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struct IsDecomposable<
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absl::void_t<decltype(
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Policy::apply(RequireUsableKey<typename Policy::key_type, Hash, Eq>(),
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std::declval<Ts>()...))>,
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Policy, Hash, Eq, Ts...> : std::true_type {};
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template <class, class = void>
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struct IsTransparent : std::false_type {};
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template <class T>
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struct IsTransparent<T, absl::void_t<typename T::is_transparent>>
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: std::true_type {};
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// TODO(alkis): Switch to std::is_nothrow_swappable when gcc/clang supports it.
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template <class T>
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constexpr bool IsNoThrowSwappable() {
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using std::swap;
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return noexcept(swap(std::declval<T&>(), std::declval<T&>()));
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}
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template <typename T>
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int TrailingZeros(T x) {
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return sizeof(T) == 8 ? base_internal::CountTrailingZerosNonZero64(x)
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: base_internal::CountTrailingZerosNonZero32(x);
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}
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template <typename T>
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int LeadingZeros(T x) {
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return sizeof(T) == 8 ? base_internal::CountLeadingZeros64(x)
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: base_internal::CountLeadingZeros32(x);
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}
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// An abstraction over a bitmask. It provides an easy way to iterate through the
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// indexes of the set bits of a bitmask. When Shift=0 (platforms with SSE),
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// this is a true bitmask. On non-SSE, platforms the arithematic used to
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// emulate the SSE behavior works in bytes (Shift=3) and leaves each bytes as
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// either 0x00 or 0x80.
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//
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// For example:
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// for (int i : BitMask<uint32_t, 16>(0x5)) -> yields 0, 2
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// for (int i : BitMask<uint64_t, 8, 3>(0x0000000080800000)) -> yields 2, 3
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template <class T, int SignificantBits, int Shift = 0>
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class BitMask {
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static_assert(std::is_unsigned<T>::value, "");
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static_assert(Shift == 0 || Shift == 3, "");
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public:
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// These are useful for unit tests (gunit).
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using value_type = int;
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using iterator = BitMask;
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using const_iterator = BitMask;
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explicit BitMask(T mask) : mask_(mask) {}
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BitMask& operator++() {
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mask_ &= (mask_ - 1);
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return *this;
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}
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explicit operator bool() const { return mask_ != 0; }
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int operator*() const { return LowestBitSet(); }
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int LowestBitSet() const {
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return container_internal::TrailingZeros(mask_) >> Shift;
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}
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int HighestBitSet() const {
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return (sizeof(T) * CHAR_BIT - container_internal::LeadingZeros(mask_) -
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1) >>
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Shift;
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}
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BitMask begin() const { return *this; }
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BitMask end() const { return BitMask(0); }
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int TrailingZeros() const {
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return container_internal::TrailingZeros(mask_) >> Shift;
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}
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int LeadingZeros() const {
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constexpr int total_significant_bits = SignificantBits << Shift;
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constexpr int extra_bits = sizeof(T) * 8 - total_significant_bits;
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return container_internal::LeadingZeros(mask_ << extra_bits) >> Shift;
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}
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private:
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friend bool operator==(const BitMask& a, const BitMask& b) {
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return a.mask_ == b.mask_;
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}
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friend bool operator!=(const BitMask& a, const BitMask& b) {
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return a.mask_ != b.mask_;
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}
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T mask_;
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};
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using ctrl_t = signed char;
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using h2_t = uint8_t;
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// The values here are selected for maximum performance. See the static asserts
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// below for details.
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enum Ctrl : ctrl_t {
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kEmpty = -128, // 0b10000000
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kDeleted = -2, // 0b11111110
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kSentinel = -1, // 0b11111111
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};
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static_assert(
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kEmpty & kDeleted & kSentinel & 0x80,
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"Special markers need to have the MSB to make checking for them efficient");
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static_assert(kEmpty < kSentinel && kDeleted < kSentinel,
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"kEmpty and kDeleted must be smaller than kSentinel to make the "
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"SIMD test of IsEmptyOrDeleted() efficient");
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static_assert(kSentinel == -1,
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"kSentinel must be -1 to elide loading it from memory into SIMD "
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"registers (pcmpeqd xmm, xmm)");
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static_assert(kEmpty == -128,
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"kEmpty must be -128 to make the SIMD check for its "
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"existence efficient (psignb xmm, xmm)");
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static_assert(~kEmpty & ~kDeleted & kSentinel & 0x7F,
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"kEmpty and kDeleted must share an unset bit that is not shared "
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"by kSentinel to make the scalar test for MatchEmptyOrDeleted() "
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"efficient");
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static_assert(kDeleted == -2,
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"kDeleted must be -2 to make the implementation of "
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"ConvertSpecialToEmptyAndFullToDeleted efficient");
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// A single block of empty control bytes for tables without any slots allocated.
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// This enables removing a branch in the hot path of find().
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inline ctrl_t* EmptyGroup() {
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alignas(16) static constexpr ctrl_t empty_group[] = {
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kSentinel, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty,
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kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty};
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return const_cast<ctrl_t*>(empty_group);
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}
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// Mixes a randomly generated per-process seed with `hash` and `ctrl` to
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// randomize insertion order within groups.
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bool ShouldInsertBackwards(size_t hash, ctrl_t* ctrl);
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// Returns a hash seed.
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//
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// The seed consists of the ctrl_ pointer, which adds enough entropy to ensure
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// non-determinism of iteration order in most cases.
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inline size_t HashSeed(const ctrl_t* ctrl) {
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// The low bits of the pointer have little or no entropy because of
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// alignment. We shift the pointer to try to use higher entropy bits. A
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// good number seems to be 12 bits, because that aligns with page size.
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return reinterpret_cast<uintptr_t>(ctrl) >> 12;
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}
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inline size_t H1(size_t hash, const ctrl_t* ctrl) {
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return (hash >> 7) ^ HashSeed(ctrl);
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}
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inline ctrl_t H2(size_t hash) { return hash & 0x7F; }
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inline bool IsEmpty(ctrl_t c) { return c == kEmpty; }
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inline bool IsFull(ctrl_t c) { return c >= 0; }
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inline bool IsDeleted(ctrl_t c) { return c == kDeleted; }
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inline bool IsEmptyOrDeleted(ctrl_t c) { return c < kSentinel; }
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#if SWISSTABLE_HAVE_SSE2
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struct Group {
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static constexpr size_t kWidth = 16; // the number of slots per group
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explicit Group(const ctrl_t* pos) {
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ctrl = _mm_loadu_si128(reinterpret_cast<const __m128i*>(pos));
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}
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// Returns a bitmask representing the positions of slots that match hash.
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BitMask<uint32_t, kWidth> Match(h2_t hash) const {
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auto match = _mm_set1_epi8(hash);
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return BitMask<uint32_t, kWidth>(
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_mm_movemask_epi8(_mm_cmpeq_epi8(match, ctrl)));
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}
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// Returns a bitmask representing the positions of empty slots.
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BitMask<uint32_t, kWidth> MatchEmpty() const {
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#if SWISSTABLE_HAVE_SSSE3
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// This only works because kEmpty is -128.
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return BitMask<uint32_t, kWidth>(
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_mm_movemask_epi8(_mm_sign_epi8(ctrl, ctrl)));
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#else
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return Match(kEmpty);
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#endif
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}
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// Returns a bitmask representing the positions of empty or deleted slots.
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BitMask<uint32_t, kWidth> MatchEmptyOrDeleted() const {
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auto special = _mm_set1_epi8(kSentinel);
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return BitMask<uint32_t, kWidth>(
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_mm_movemask_epi8(_mm_cmpgt_epi8(special, ctrl)));
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}
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// Returns the number of trailing empty or deleted elements in the group.
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uint32_t CountLeadingEmptyOrDeleted() const {
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auto special = _mm_set1_epi8(kSentinel);
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return TrailingZeros(_mm_movemask_epi8(_mm_cmpgt_epi8(special, ctrl)) + 1);
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}
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void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
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auto msbs = _mm_set1_epi8(0x80);
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auto x126 = _mm_set1_epi8(126);
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#if SWISSTABLE_HAVE_SSSE3
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auto res = _mm_or_si128(_mm_shuffle_epi8(x126, ctrl), msbs);
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#else
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auto zero = _mm_setzero_si128();
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auto special_mask = _mm_cmpgt_epi8(zero, ctrl);
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auto res = _mm_or_si128(msbs, _mm_andnot_si128(special_mask, x126));
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#endif
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_mm_storeu_si128(reinterpret_cast<__m128i*>(dst), res);
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}
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__m128i ctrl;
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};
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#else
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struct Group {
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static constexpr size_t kWidth = 8;
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explicit Group(const ctrl_t* pos) : ctrl(little_endian::Load64(pos)) {}
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BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
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// For the technique, see:
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// http://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
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// (Determine if a word has a byte equal to n).
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//
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// Caveat: there are false positives but:
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// - they only occur if there is a real match
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// - they never occur on kEmpty, kDeleted, kSentinel
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// - they will be handled gracefully by subsequent checks in code
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//
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// Example:
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// v = 0x1716151413121110
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// hash = 0x12
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// retval = (v - lsbs) & ~v & msbs = 0x0000000080800000
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constexpr uint64_t msbs = 0x8080808080808080ULL;
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constexpr uint64_t lsbs = 0x0101010101010101ULL;
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auto x = ctrl ^ (lsbs * hash);
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return BitMask<uint64_t, kWidth, 3>((x - lsbs) & ~x & msbs);
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}
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BitMask<uint64_t, kWidth, 3> MatchEmpty() const {
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constexpr uint64_t msbs = 0x8080808080808080ULL;
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return BitMask<uint64_t, kWidth, 3>((ctrl & (~ctrl << 6)) & msbs);
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}
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BitMask<uint64_t, kWidth, 3> MatchEmptyOrDeleted() const {
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constexpr uint64_t msbs = 0x8080808080808080ULL;
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return BitMask<uint64_t, kWidth, 3>((ctrl & (~ctrl << 7)) & msbs);
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}
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uint32_t CountLeadingEmptyOrDeleted() const {
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constexpr uint64_t gaps = 0x00FEFEFEFEFEFEFEULL;
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return (TrailingZeros(((~ctrl & (ctrl >> 7)) | gaps) + 1) + 7) >> 3;
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}
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void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
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constexpr uint64_t msbs = 0x8080808080808080ULL;
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constexpr uint64_t lsbs = 0x0101010101010101ULL;
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auto x = ctrl & msbs;
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auto res = (~x + (x >> 7)) & ~lsbs;
|
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little_endian::Store64(dst, res);
|
|
}
|
|
|
|
uint64_t ctrl;
|
|
};
|
|
#endif // SWISSTABLE_HAVE_SSE2
|
|
|
|
template <class Policy, class Hash, class Eq, class Alloc>
|
|
class raw_hash_set;
|
|
|
|
|
|
inline bool IsValidCapacity(size_t n) {
|
|
return ((n + 1) & n) == 0 && n >= Group::kWidth - 1;
|
|
}
|
|
|
|
// PRECONDITION:
|
|
// IsValidCapacity(capacity)
|
|
// ctrl[capacity] == kSentinel
|
|
// ctrl[i] != kSentinel for all i < capacity
|
|
// Applies mapping for every byte in ctrl:
|
|
// DELETED -> EMPTY
|
|
// EMPTY -> EMPTY
|
|
// FULL -> DELETED
|
|
inline void ConvertDeletedToEmptyAndFullToDeleted(
|
|
ctrl_t* ctrl, size_t capacity) {
|
|
assert(ctrl[capacity] == kSentinel);
|
|
assert(IsValidCapacity(capacity));
|
|
for (ctrl_t* pos = ctrl; pos != ctrl + capacity + 1; pos += Group::kWidth) {
|
|
Group{pos}.ConvertSpecialToEmptyAndFullToDeleted(pos);
|
|
}
|
|
// Copy the cloned ctrl bytes.
|
|
std::memcpy(ctrl + capacity + 1, ctrl, Group::kWidth);
|
|
ctrl[capacity] = kSentinel;
|
|
}
|
|
|
|
// Rounds up the capacity to the next power of 2 minus 1 and ensures it is
|
|
// greater or equal to Group::kWidth - 1.
|
|
inline size_t NormalizeCapacity(size_t n) {
|
|
constexpr size_t kMinCapacity = Group::kWidth - 1;
|
|
return n <= kMinCapacity
|
|
? kMinCapacity
|
|
: std::numeric_limits<size_t>::max() >> LeadingZeros(n);
|
|
}
|
|
|
|
// The node_handle concept from C++17.
|
|
// We specialize node_handle for sets and maps. node_handle_base holds the
|
|
// common API of both.
|
|
template <typename Policy, typename Alloc>
|
|
class node_handle_base {
|
|
protected:
|
|
using PolicyTraits = hash_policy_traits<Policy>;
|
|
using slot_type = typename PolicyTraits::slot_type;
|
|
|
|
public:
|
|
using allocator_type = Alloc;
|
|
|
|
constexpr node_handle_base() {}
|
|
node_handle_base(node_handle_base&& other) noexcept {
|
|
*this = std::move(other);
|
|
}
|
|
~node_handle_base() { destroy(); }
|
|
node_handle_base& operator=(node_handle_base&& other) {
|
|
destroy();
|
|
if (!other.empty()) {
|
|
alloc_ = other.alloc_;
|
|
PolicyTraits::transfer(alloc(), slot(), other.slot());
|
|
other.reset();
|
|
}
|
|
return *this;
|
|
}
|
|
|
|
bool empty() const noexcept { return !alloc_; }
|
|
explicit operator bool() const noexcept { return !empty(); }
|
|
allocator_type get_allocator() const { return *alloc_; }
|
|
|
|
protected:
|
|
template <typename, typename, typename, typename>
|
|
friend class raw_hash_set;
|
|
|
|
node_handle_base(const allocator_type& a, slot_type* s) : alloc_(a) {
|
|
PolicyTraits::transfer(alloc(), slot(), s);
|
|
}
|
|
|
|
void destroy() {
|
|
if (!empty()) {
|
|
PolicyTraits::destroy(alloc(), slot());
|
|
reset();
|
|
}
|
|
}
|
|
|
|
void reset() {
|
|
assert(alloc_.has_value());
|
|
alloc_ = absl::nullopt;
|
|
}
|
|
|
|
slot_type* slot() const {
|
|
assert(!empty());
|
|
return reinterpret_cast<slot_type*>(std::addressof(slot_space_));
|
|
}
|
|
allocator_type* alloc() { return std::addressof(*alloc_); }
|
|
|
|
private:
|
|
absl::optional<allocator_type> alloc_;
|
|
mutable absl::aligned_storage_t<sizeof(slot_type), alignof(slot_type)>
|
|
slot_space_;
|
|
};
|
|
|
|
// For sets.
|
|
template <typename Policy, typename Alloc, typename = void>
|
|
class node_handle : public node_handle_base<Policy, Alloc> {
|
|
using Base = typename node_handle::node_handle_base;
|
|
|
|
public:
|
|
using value_type = typename Base::PolicyTraits::value_type;
|
|
|
|
constexpr node_handle() {}
|
|
|
|
value_type& value() const {
|
|
return Base::PolicyTraits::element(this->slot());
|
|
}
|
|
|
|
private:
|
|
template <typename, typename, typename, typename>
|
|
friend class raw_hash_set;
|
|
|
|
node_handle(const Alloc& a, typename Base::slot_type* s) : Base(a, s) {}
|
|
};
|
|
|
|
// For maps.
|
|
template <typename Policy, typename Alloc>
|
|
class node_handle<Policy, Alloc, absl::void_t<typename Policy::mapped_type>>
|
|
: public node_handle_base<Policy, Alloc> {
|
|
using Base = typename node_handle::node_handle_base;
|
|
|
|
public:
|
|
using key_type = typename Policy::key_type;
|
|
using mapped_type = typename Policy::mapped_type;
|
|
|
|
constexpr node_handle() {}
|
|
|
|
auto key() const -> decltype(Base::PolicyTraits::key(this->slot())) {
|
|
return Base::PolicyTraits::key(this->slot());
|
|
}
|
|
|
|
mapped_type& mapped() const {
|
|
return Base::PolicyTraits::value(
|
|
&Base::PolicyTraits::element(this->slot()));
|
|
}
|
|
|
|
private:
|
|
template <typename, typename, typename, typename>
|
|
friend class raw_hash_set;
|
|
|
|
node_handle(const Alloc& a, typename Base::slot_type* s) : Base(a, s) {}
|
|
};
|
|
|
|
// Implement the insert_return_type<> concept of C++17.
|
|
template <class Iterator, class NodeType>
|
|
struct insert_return_type {
|
|
Iterator position;
|
|
bool inserted;
|
|
NodeType node;
|
|
};
|
|
|
|
// Helper trait to allow or disallow arbitrary keys when the hash and
|
|
// eq functions are transparent.
|
|
// It is very important that the inner template is an alias and that the type it
|
|
// produces is not a dependent type. Otherwise, type deduction would fail.
|
|
template <bool is_transparent>
|
|
struct KeyArg {
|
|
// Transparent. Forward `K`.
|
|
template <typename K, typename key_type>
|
|
using type = K;
|
|
};
|
|
|
|
template <>
|
|
struct KeyArg<false> {
|
|
// Not transparent. Always use `key_type`.
|
|
template <typename K, typename key_type>
|
|
using type = key_type;
|
|
};
|
|
|
|
// Policy: a policy defines how to perform different operations on
|
|
// the slots of the hashtable (see hash_policy_traits.h for the full interface
|
|
// of policy).
|
|
//
|
|
// Hash: a (possibly polymorphic) functor that hashes keys of the hashtable. The
|
|
// functor should accept a key and return size_t as hash. For best performance
|
|
// it is important that the hash function provides high entropy across all bits
|
|
// of the hash.
|
|
//
|
|
// Eq: a (possibly polymorphic) functor that compares two keys for equality. It
|
|
// should accept two (of possibly different type) keys and return a bool: true
|
|
// if they are equal, false if they are not. If two keys compare equal, then
|
|
// their hash values as defined by Hash MUST be equal.
|
|
//
|
|
// Allocator: an Allocator [http://devdocs.io/cpp/concept/allocator] with which
|
|
// the storage of the hashtable will be allocated and the elements will be
|
|
// constructed and destroyed.
|
|
template <class Policy, class Hash, class Eq, class Alloc>
|
|
class raw_hash_set {
|
|
using PolicyTraits = hash_policy_traits<Policy>;
|
|
using KeyArgImpl = container_internal::KeyArg<IsTransparent<Eq>::value &&
|
|
IsTransparent<Hash>::value>;
|
|
|
|
public:
|
|
using init_type = typename PolicyTraits::init_type;
|
|
using key_type = typename PolicyTraits::key_type;
|
|
// TODO(sbenza): Hide slot_type as it is an implementation detail. Needs user
|
|
// code fixes!
|
|
using slot_type = typename PolicyTraits::slot_type;
|
|
using allocator_type = Alloc;
|
|
using size_type = size_t;
|
|
using difference_type = ptrdiff_t;
|
|
using hasher = Hash;
|
|
using key_equal = Eq;
|
|
using policy_type = Policy;
|
|
using value_type = typename PolicyTraits::value_type;
|
|
using reference = value_type&;
|
|
using const_reference = const value_type&;
|
|
using pointer = typename absl::allocator_traits<
|
|
allocator_type>::template rebind_traits<value_type>::pointer;
|
|
using const_pointer = typename absl::allocator_traits<
|
|
allocator_type>::template rebind_traits<value_type>::const_pointer;
|
|
|
|
// Alias used for heterogeneous lookup functions.
|
|
// `key_arg<K>` evaluates to `K` when the functors are transparent and to
|
|
// `key_type` otherwise. It permits template argument deduction on `K` for the
|
|
// transparent case.
|
|
template <class K>
|
|
using key_arg = typename KeyArgImpl::template type<K, key_type>;
|
|
|
|
private:
|
|
// Give an early error when key_type is not hashable/eq.
|
|
auto KeyTypeCanBeHashed(const Hash& h, const key_type& k) -> decltype(h(k));
|
|
auto KeyTypeCanBeEq(const Eq& eq, const key_type& k) -> decltype(eq(k, k));
|
|
|
|
using Layout = absl::container_internal::Layout<ctrl_t, slot_type>;
|
|
|
|
static Layout MakeLayout(size_t capacity) {
|
|
assert(IsValidCapacity(capacity));
|
|
return Layout(capacity + Group::kWidth + 1, capacity);
|
|
}
|
|
|
|
using AllocTraits = absl::allocator_traits<allocator_type>;
|
|
using SlotAlloc = typename absl::allocator_traits<
|
|
allocator_type>::template rebind_alloc<slot_type>;
|
|
using SlotAllocTraits = typename absl::allocator_traits<
|
|
allocator_type>::template rebind_traits<slot_type>;
|
|
|
|
static_assert(std::is_lvalue_reference<reference>::value,
|
|
"Policy::element() must return a reference");
|
|
|
|
template <typename T>
|
|
struct SameAsElementReference
|
|
: std::is_same<typename std::remove_cv<
|
|
typename std::remove_reference<reference>::type>::type,
|
|
typename std::remove_cv<
|
|
typename std::remove_reference<T>::type>::type> {};
|
|
|
|
// An enabler for insert(T&&): T must be convertible to init_type or be the
|
|
// same as [cv] value_type [ref].
|
|
// Note: we separate SameAsElementReference into its own type to avoid using
|
|
// reference unless we need to. MSVC doesn't seem to like it in some
|
|
// cases.
|
|
template <class T>
|
|
using RequiresInsertable = typename std::enable_if<
|
|
absl::disjunction<std::is_convertible<T, init_type>,
|
|
SameAsElementReference<T>>::value,
|
|
int>::type;
|
|
|
|
// RequiresNotInit is a workaround for gcc prior to 7.1.
|
|
// See https://godbolt.org/g/Y4xsUh.
|
|
template <class T>
|
|
using RequiresNotInit =
|
|
typename std::enable_if<!std::is_same<T, init_type>::value, int>::type;
|
|
|
|
template <class... Ts>
|
|
using IsDecomposable = IsDecomposable<void, PolicyTraits, Hash, Eq, Ts...>;
|
|
|
|
public:
|
|
static_assert(std::is_same<pointer, value_type*>::value,
|
|
"Allocators with custom pointer types are not supported");
|
|
static_assert(std::is_same<const_pointer, const value_type*>::value,
|
|
"Allocators with custom pointer types are not supported");
|
|
|
|
class iterator {
|
|
friend class raw_hash_set;
|
|
|
|
public:
|
|
using iterator_category = std::forward_iterator_tag;
|
|
using value_type = typename raw_hash_set::value_type;
|
|
using reference =
|
|
absl::conditional_t<PolicyTraits::constant_iterators::value,
|
|
const value_type&, value_type&>;
|
|
using pointer = absl::remove_reference_t<reference>*;
|
|
using difference_type = typename raw_hash_set::difference_type;
|
|
|
|
iterator() {}
|
|
|
|
// PRECONDITION: not an end() iterator.
|
|
reference operator*() const { return PolicyTraits::element(slot_); }
|
|
|
|
// PRECONDITION: not an end() iterator.
|
|
pointer operator->() const { return &operator*(); }
|
|
|
|
// PRECONDITION: not an end() iterator.
|
|
iterator& operator++() {
|
|
++ctrl_;
|
|
++slot_;
|
|
skip_empty_or_deleted();
|
|
return *this;
|
|
}
|
|
// PRECONDITION: not an end() iterator.
|
|
iterator operator++(int) {
|
|
auto tmp = *this;
|
|
++*this;
|
|
return tmp;
|
|
}
|
|
|
|
friend bool operator==(const iterator& a, const iterator& b) {
|
|
return a.ctrl_ == b.ctrl_;
|
|
}
|
|
friend bool operator!=(const iterator& a, const iterator& b) {
|
|
return !(a == b);
|
|
}
|
|
|
|
private:
|
|
iterator(ctrl_t* ctrl) : ctrl_(ctrl) {} // for end()
|
|
iterator(ctrl_t* ctrl, slot_type* slot) : ctrl_(ctrl), slot_(slot) {}
|
|
|
|
void skip_empty_or_deleted() {
|
|
while (IsEmptyOrDeleted(*ctrl_)) {
|
|
// ctrl is not necessarily aligned to Group::kWidth. It is also likely
|
|
// to read past the space for ctrl bytes and into slots. This is ok
|
|
// because ctrl has sizeof() == 1 and slot has sizeof() >= 1 so there
|
|
// is no way to read outside the combined slot array.
|
|
uint32_t shift = Group{ctrl_}.CountLeadingEmptyOrDeleted();
|
|
ctrl_ += shift;
|
|
slot_ += shift;
|
|
}
|
|
}
|
|
|
|
ctrl_t* ctrl_ = nullptr;
|
|
slot_type* slot_;
|
|
};
|
|
|
|
class const_iterator {
|
|
friend class raw_hash_set;
|
|
|
|
public:
|
|
using iterator_category = typename iterator::iterator_category;
|
|
using value_type = typename raw_hash_set::value_type;
|
|
using reference = typename raw_hash_set::const_reference;
|
|
using pointer = typename raw_hash_set::const_pointer;
|
|
using difference_type = typename raw_hash_set::difference_type;
|
|
|
|
const_iterator() {}
|
|
// Implicit construction from iterator.
|
|
const_iterator(iterator i) : inner_(std::move(i)) {}
|
|
|
|
reference operator*() const { return *inner_; }
|
|
pointer operator->() const { return inner_.operator->(); }
|
|
|
|
const_iterator& operator++() {
|
|
++inner_;
|
|
return *this;
|
|
}
|
|
const_iterator operator++(int) { return inner_++; }
|
|
|
|
friend bool operator==(const const_iterator& a, const const_iterator& b) {
|
|
return a.inner_ == b.inner_;
|
|
}
|
|
friend bool operator!=(const const_iterator& a, const const_iterator& b) {
|
|
return !(a == b);
|
|
}
|
|
|
|
private:
|
|
const_iterator(const ctrl_t* ctrl, const slot_type* slot)
|
|
: inner_(const_cast<ctrl_t*>(ctrl), const_cast<slot_type*>(slot)) {}
|
|
|
|
iterator inner_;
|
|
};
|
|
|
|
using node_type = container_internal::node_handle<Policy, Alloc>;
|
|
|
|
raw_hash_set() noexcept(
|
|
std::is_nothrow_default_constructible<hasher>::value&&
|
|
std::is_nothrow_default_constructible<key_equal>::value&&
|
|
std::is_nothrow_default_constructible<allocator_type>::value) {}
|
|
|
|
explicit raw_hash_set(size_t bucket_count, const hasher& hash = hasher(),
|
|
const key_equal& eq = key_equal(),
|
|
const allocator_type& alloc = allocator_type())
|
|
: ctrl_(EmptyGroup()), settings_(0, hash, eq, alloc) {
|
|
if (bucket_count) {
|
|
capacity_ = NormalizeCapacity(bucket_count);
|
|
growth_left() = static_cast<size_t>(capacity_ * kMaxLoadFactor);
|
|
initialize_slots();
|
|
}
|
|
}
|
|
|
|
raw_hash_set(size_t bucket_count, const hasher& hash,
|
|
const allocator_type& alloc)
|
|
: raw_hash_set(bucket_count, hash, key_equal(), alloc) {}
|
|
|
|
raw_hash_set(size_t bucket_count, const allocator_type& alloc)
|
|
: raw_hash_set(bucket_count, hasher(), key_equal(), alloc) {}
|
|
|
|
explicit raw_hash_set(const allocator_type& alloc)
|
|
: raw_hash_set(0, hasher(), key_equal(), alloc) {}
|
|
|
|
template <class InputIter>
|
|
raw_hash_set(InputIter first, InputIter last, size_t bucket_count = 0,
|
|
const hasher& hash = hasher(), const key_equal& eq = key_equal(),
|
|
const allocator_type& alloc = allocator_type())
|
|
: raw_hash_set(bucket_count, hash, eq, alloc) {
|
|
insert(first, last);
|
|
}
|
|
|
|
template <class InputIter>
|
|
raw_hash_set(InputIter first, InputIter last, size_t bucket_count,
|
|
const hasher& hash, const allocator_type& alloc)
|
|
: raw_hash_set(first, last, bucket_count, hash, key_equal(), alloc) {}
|
|
|
|
template <class InputIter>
|
|
raw_hash_set(InputIter first, InputIter last, size_t bucket_count,
|
|
const allocator_type& alloc)
|
|
: raw_hash_set(first, last, bucket_count, hasher(), key_equal(), alloc) {}
|
|
|
|
template <class InputIter>
|
|
raw_hash_set(InputIter first, InputIter last, const allocator_type& alloc)
|
|
: raw_hash_set(first, last, 0, hasher(), key_equal(), alloc) {}
|
|
|
|
// Instead of accepting std::initializer_list<value_type> as the first
|
|
// argument like std::unordered_set<value_type> does, we have two overloads
|
|
// that accept std::initializer_list<T> and std::initializer_list<init_type>.
|
|
// This is advantageous for performance.
|
|
//
|
|
// // Turns {"abc", "def"} into std::initializer_list<std::string>, then copies
|
|
// // the strings into the set.
|
|
// std::unordered_set<std::string> s = {"abc", "def"};
|
|
//
|
|
// // Turns {"abc", "def"} into std::initializer_list<const char*>, then
|
|
// // copies the strings into the set.
|
|
// absl::flat_hash_set<std::string> s = {"abc", "def"};
|
|
//
|
|
// The same trick is used in insert().
|
|
//
|
|
// The enabler is necessary to prevent this constructor from triggering where
|
|
// the copy constructor is meant to be called.
|
|
//
|
|
// absl::flat_hash_set<int> a, b{a};
|
|
//
|
|
// RequiresNotInit<T> is a workaround for gcc prior to 7.1.
|
|
template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
|
|
raw_hash_set(std::initializer_list<T> init, size_t bucket_count = 0,
|
|
const hasher& hash = hasher(), const key_equal& eq = key_equal(),
|
|
const allocator_type& alloc = allocator_type())
|
|
: raw_hash_set(init.begin(), init.end(), bucket_count, hash, eq, alloc) {}
|
|
|
|
raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count = 0,
|
|
const hasher& hash = hasher(), const key_equal& eq = key_equal(),
|
|
const allocator_type& alloc = allocator_type())
|
|
: raw_hash_set(init.begin(), init.end(), bucket_count, hash, eq, alloc) {}
|
|
|
|
template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
|
|
raw_hash_set(std::initializer_list<T> init, size_t bucket_count,
|
|
const hasher& hash, const allocator_type& alloc)
|
|
: raw_hash_set(init, bucket_count, hash, key_equal(), alloc) {}
|
|
|
|
raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count,
|
|
const hasher& hash, const allocator_type& alloc)
|
|
: raw_hash_set(init, bucket_count, hash, key_equal(), alloc) {}
|
|
|
|
template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
|
|
raw_hash_set(std::initializer_list<T> init, size_t bucket_count,
|
|
const allocator_type& alloc)
|
|
: raw_hash_set(init, bucket_count, hasher(), key_equal(), alloc) {}
|
|
|
|
raw_hash_set(std::initializer_list<init_type> init, size_t bucket_count,
|
|
const allocator_type& alloc)
|
|
: raw_hash_set(init, bucket_count, hasher(), key_equal(), alloc) {}
|
|
|
|
template <class T, RequiresNotInit<T> = 0, RequiresInsertable<T> = 0>
|
|
raw_hash_set(std::initializer_list<T> init, const allocator_type& alloc)
|
|
: raw_hash_set(init, 0, hasher(), key_equal(), alloc) {}
|
|
|
|
raw_hash_set(std::initializer_list<init_type> init,
|
|
const allocator_type& alloc)
|
|
: raw_hash_set(init, 0, hasher(), key_equal(), alloc) {}
|
|
|
|
raw_hash_set(const raw_hash_set& that)
|
|
: raw_hash_set(that, AllocTraits::select_on_container_copy_construction(
|
|
that.alloc_ref())) {}
|
|
|
|
raw_hash_set(const raw_hash_set& that, const allocator_type& a)
|
|
: raw_hash_set(0, that.hash_ref(), that.eq_ref(), a) {
|
|
reserve(that.size());
|
|
// Because the table is guaranteed to be empty, we can do something faster
|
|
// than a full `insert`.
|
|
for (const auto& v : that) {
|
|
const size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, v);
|
|
const size_t i = find_first_non_full(hash);
|
|
set_ctrl(i, H2(hash));
|
|
emplace_at(i, v);
|
|
}
|
|
size_ = that.size();
|
|
growth_left() -= that.size();
|
|
}
|
|
|
|
raw_hash_set(raw_hash_set&& that) noexcept(
|
|
std::is_nothrow_copy_constructible<hasher>::value&&
|
|
std::is_nothrow_copy_constructible<key_equal>::value&&
|
|
std::is_nothrow_copy_constructible<allocator_type>::value)
|
|
: ctrl_(absl::exchange(that.ctrl_, EmptyGroup())),
|
|
slots_(absl::exchange(that.slots_, nullptr)),
|
|
size_(absl::exchange(that.size_, 0)),
|
|
capacity_(absl::exchange(that.capacity_, 0)),
|
|
// Hash, equality and allocator are copied instead of moved because
|
|
// `that` must be left valid. If Hash is std::function<Key>, moving it
|
|
// would create a nullptr functor that cannot be called.
|
|
settings_(that.settings_) {
|
|
// growth_left was copied above, reset the one from `that`.
|
|
that.growth_left() = 0;
|
|
}
|
|
|
|
raw_hash_set(raw_hash_set&& that, const allocator_type& a)
|
|
: ctrl_(EmptyGroup()),
|
|
slots_(nullptr),
|
|
size_(0),
|
|
capacity_(0),
|
|
settings_(0, that.hash_ref(), that.eq_ref(), a) {
|
|
if (a == that.alloc_ref()) {
|
|
std::swap(ctrl_, that.ctrl_);
|
|
std::swap(slots_, that.slots_);
|
|
std::swap(size_, that.size_);
|
|
std::swap(capacity_, that.capacity_);
|
|
std::swap(growth_left(), that.growth_left());
|
|
} else {
|
|
reserve(that.size());
|
|
// Note: this will copy elements of dense_set and unordered_set instead of
|
|
// moving them. This can be fixed if it ever becomes an issue.
|
|
for (auto& elem : that) insert(std::move(elem));
|
|
}
|
|
}
|
|
|
|
raw_hash_set& operator=(const raw_hash_set& that) {
|
|
raw_hash_set tmp(that,
|
|
AllocTraits::propagate_on_container_copy_assignment::value
|
|
? that.alloc_ref()
|
|
: alloc_ref());
|
|
swap(tmp);
|
|
return *this;
|
|
}
|
|
|
|
raw_hash_set& operator=(raw_hash_set&& that) noexcept(
|
|
absl::allocator_traits<allocator_type>::is_always_equal::value&&
|
|
std::is_nothrow_move_assignable<hasher>::value&&
|
|
std::is_nothrow_move_assignable<key_equal>::value) {
|
|
// TODO(sbenza): We should only use the operations from the noexcept clause
|
|
// to make sure we actually adhere to that contract.
|
|
return move_assign(
|
|
std::move(that),
|
|
typename AllocTraits::propagate_on_container_move_assignment());
|
|
}
|
|
|
|
~raw_hash_set() { destroy_slots(); }
|
|
|
|
iterator begin() {
|
|
auto it = iterator_at(0);
|
|
it.skip_empty_or_deleted();
|
|
return it;
|
|
}
|
|
iterator end() { return {ctrl_ + capacity_}; }
|
|
|
|
const_iterator begin() const {
|
|
return const_cast<raw_hash_set*>(this)->begin();
|
|
}
|
|
const_iterator end() const { return const_cast<raw_hash_set*>(this)->end(); }
|
|
const_iterator cbegin() const { return begin(); }
|
|
const_iterator cend() const { return end(); }
|
|
|
|
bool empty() const { return !size(); }
|
|
size_t size() const { return size_; }
|
|
size_t capacity() const { return capacity_; }
|
|
size_t max_size() const { return std::numeric_limits<size_t>::max(); }
|
|
|
|
void clear() {
|
|
// Iterating over this container is O(bucket_count()). When bucket_count()
|
|
// is much greater than size(), iteration becomes prohibitively expensive.
|
|
// For clear() it is more important to reuse the allocated array when the
|
|
// container is small because allocation takes comparatively long time
|
|
// compared to destruction of the elements of the container. So we pick the
|
|
// largest bucket_count() threshold for which iteration is still fast and
|
|
// past that we simply deallocate the array.
|
|
if (capacity_ > 127) {
|
|
destroy_slots();
|
|
} else if (capacity_) {
|
|
for (size_t i = 0; i != capacity_; ++i) {
|
|
if (IsFull(ctrl_[i])) {
|
|
PolicyTraits::destroy(&alloc_ref(), slots_ + i);
|
|
}
|
|
}
|
|
size_ = 0;
|
|
reset_ctrl();
|
|
growth_left() = static_cast<size_t>(capacity_ * kMaxLoadFactor);
|
|
}
|
|
assert(empty());
|
|
}
|
|
|
|
// This overload kicks in when the argument is an rvalue of insertable and
|
|
// decomposable type other than init_type.
|
|
//
|
|
// flat_hash_map<std::string, int> m;
|
|
// m.insert(std::make_pair("abc", 42));
|
|
template <class T, RequiresInsertable<T> = 0,
|
|
typename std::enable_if<IsDecomposable<T>::value, int>::type = 0,
|
|
T* = nullptr>
|
|
std::pair<iterator, bool> insert(T&& value) {
|
|
return emplace(std::forward<T>(value));
|
|
}
|
|
|
|
// This overload kicks in when the argument is a bitfield or an lvalue of
|
|
// insertable and decomposable type.
|
|
//
|
|
// union { int n : 1; };
|
|
// flat_hash_set<int> s;
|
|
// s.insert(n);
|
|
//
|
|
// flat_hash_set<std::string> s;
|
|
// const char* p = "hello";
|
|
// s.insert(p);
|
|
//
|
|
// TODO(romanp): Once we stop supporting gcc 5.1 and below, replace
|
|
// RequiresInsertable<T> with RequiresInsertable<const T&>.
|
|
// We are hitting this bug: https://godbolt.org/g/1Vht4f.
|
|
template <
|
|
class T, RequiresInsertable<T> = 0,
|
|
typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
|
|
std::pair<iterator, bool> insert(const T& value) {
|
|
return emplace(value);
|
|
}
|
|
|
|
// This overload kicks in when the argument is an rvalue of init_type. Its
|
|
// purpose is to handle brace-init-list arguments.
|
|
//
|
|
// flat_hash_set<std::string, int> s;
|
|
// s.insert({"abc", 42});
|
|
std::pair<iterator, bool> insert(init_type&& value) {
|
|
return emplace(std::move(value));
|
|
}
|
|
|
|
template <class T, RequiresInsertable<T> = 0,
|
|
typename std::enable_if<IsDecomposable<T>::value, int>::type = 0,
|
|
T* = nullptr>
|
|
iterator insert(const_iterator, T&& value) {
|
|
return insert(std::forward<T>(value)).first;
|
|
}
|
|
|
|
// TODO(romanp): Once we stop supporting gcc 5.1 and below, replace
|
|
// RequiresInsertable<T> with RequiresInsertable<const T&>.
|
|
// We are hitting this bug: https://godbolt.org/g/1Vht4f.
|
|
template <
|
|
class T, RequiresInsertable<T> = 0,
|
|
typename std::enable_if<IsDecomposable<const T&>::value, int>::type = 0>
|
|
iterator insert(const_iterator, const T& value) {
|
|
return insert(value).first;
|
|
}
|
|
|
|
iterator insert(const_iterator, init_type&& value) {
|
|
return insert(std::move(value)).first;
|
|
}
|
|
|
|
template <class InputIt>
|
|
void insert(InputIt first, InputIt last) {
|
|
for (; first != last; ++first) insert(*first);
|
|
}
|
|
|
|
template <class T, RequiresNotInit<T> = 0, RequiresInsertable<const T&> = 0>
|
|
void insert(std::initializer_list<T> ilist) {
|
|
insert(ilist.begin(), ilist.end());
|
|
}
|
|
|
|
void insert(std::initializer_list<init_type> ilist) {
|
|
insert(ilist.begin(), ilist.end());
|
|
}
|
|
|
|
insert_return_type<iterator, node_type> insert(node_type&& node) {
|
|
if (!node) return {end(), false, node_type()};
|
|
const auto& elem = PolicyTraits::element(node.slot());
|
|
auto res = PolicyTraits::apply(
|
|
InsertSlot<false>{*this, std::move(*node.slot())}, elem);
|
|
if (res.second) {
|
|
node.reset();
|
|
return {res.first, true, node_type()};
|
|
} else {
|
|
return {res.first, false, std::move(node)};
|
|
}
|
|
}
|
|
|
|
iterator insert(const_iterator, node_type&& node) {
|
|
return insert(std::move(node)).first;
|
|
}
|
|
|
|
// This overload kicks in if we can deduce the key from args. This enables us
|
|
// to avoid constructing value_type if an entry with the same key already
|
|
// exists.
|
|
//
|
|
// For example:
|
|
//
|
|
// flat_hash_map<std::string, std::string> m = {{"abc", "def"}};
|
|
// // Creates no std::string copies and makes no heap allocations.
|
|
// m.emplace("abc", "xyz");
|
|
template <class... Args, typename std::enable_if<
|
|
IsDecomposable<Args...>::value, int>::type = 0>
|
|
std::pair<iterator, bool> emplace(Args&&... args) {
|
|
return PolicyTraits::apply(EmplaceDecomposable{*this},
|
|
std::forward<Args>(args)...);
|
|
}
|
|
|
|
// This overload kicks in if we cannot deduce the key from args. It constructs
|
|
// value_type unconditionally and then either moves it into the table or
|
|
// destroys.
|
|
template <class... Args, typename std::enable_if<
|
|
!IsDecomposable<Args...>::value, int>::type = 0>
|
|
std::pair<iterator, bool> emplace(Args&&... args) {
|
|
typename std::aligned_storage<sizeof(slot_type), alignof(slot_type)>::type
|
|
raw;
|
|
slot_type* slot = reinterpret_cast<slot_type*>(&raw);
|
|
|
|
PolicyTraits::construct(&alloc_ref(), slot, std::forward<Args>(args)...);
|
|
const auto& elem = PolicyTraits::element(slot);
|
|
return PolicyTraits::apply(InsertSlot<true>{*this, std::move(*slot)}, elem);
|
|
}
|
|
|
|
template <class... Args>
|
|
iterator emplace_hint(const_iterator, Args&&... args) {
|
|
return emplace(std::forward<Args>(args)...).first;
|
|
}
|
|
|
|
// Extension API: support for lazy emplace.
|
|
//
|
|
// Looks up key in the table. If found, returns the iterator to the element.
|
|
// Otherwise calls f with one argument of type raw_hash_set::constructor. f
|
|
// MUST call raw_hash_set::constructor with arguments as if a
|
|
// raw_hash_set::value_type is constructed, otherwise the behavior is
|
|
// undefined.
|
|
//
|
|
// For example:
|
|
//
|
|
// std::unordered_set<ArenaString> s;
|
|
// // Makes ArenaStr even if "abc" is in the map.
|
|
// s.insert(ArenaString(&arena, "abc"));
|
|
//
|
|
// flat_hash_set<ArenaStr> s;
|
|
// // Makes ArenaStr only if "abc" is not in the map.
|
|
// s.lazy_emplace("abc", [&](const constructor& ctor) {
|
|
// ctor(&arena, "abc");
|
|
// });
|
|
//
|
|
// WARNING: This API is currently experimental. If there is a way to implement
|
|
// the same thing with the rest of the API, prefer that.
|
|
class constructor {
|
|
friend class raw_hash_set;
|
|
|
|
public:
|
|
template <class... Args>
|
|
void operator()(Args&&... args) const {
|
|
assert(*slot_);
|
|
PolicyTraits::construct(alloc_, *slot_, std::forward<Args>(args)...);
|
|
*slot_ = nullptr;
|
|
}
|
|
|
|
private:
|
|
constructor(allocator_type* a, slot_type** slot) : alloc_(a), slot_(slot) {}
|
|
|
|
allocator_type* alloc_;
|
|
slot_type** slot_;
|
|
};
|
|
|
|
template <class K = key_type, class F>
|
|
iterator lazy_emplace(const key_arg<K>& key, F&& f) {
|
|
auto res = find_or_prepare_insert(key);
|
|
if (res.second) {
|
|
slot_type* slot = slots_ + res.first;
|
|
std::forward<F>(f)(constructor(&alloc_ref(), &slot));
|
|
assert(!slot);
|
|
}
|
|
return iterator_at(res.first);
|
|
}
|
|
|
|
// Extension API: support for heterogeneous keys.
|
|
//
|
|
// std::unordered_set<std::string> s;
|
|
// // Turns "abc" into std::string.
|
|
// s.erase("abc");
|
|
//
|
|
// flat_hash_set<std::string> s;
|
|
// // Uses "abc" directly without copying it into std::string.
|
|
// s.erase("abc");
|
|
template <class K = key_type>
|
|
size_type erase(const key_arg<K>& key) {
|
|
auto it = find(key);
|
|
if (it == end()) return 0;
|
|
erase(it);
|
|
return 1;
|
|
}
|
|
|
|
// Erases the element pointed to by `it`. Unlike `std::unordered_set::erase`,
|
|
// this method returns void to reduce algorithmic complexity to O(1). In
|
|
// order to erase while iterating across a map, use the following idiom (which
|
|
// also works for standard containers):
|
|
//
|
|
// for (auto it = m.begin(), end = m.end(); it != end;) {
|
|
// if (<pred>) {
|
|
// m.erase(it++);
|
|
// } else {
|
|
// ++it;
|
|
// }
|
|
// }
|
|
void erase(const_iterator cit) { erase(cit.inner_); }
|
|
|
|
// This overload is necessary because otherwise erase<K>(const K&) would be
|
|
// a better match if non-const iterator is passed as an argument.
|
|
void erase(iterator it) {
|
|
assert(it != end());
|
|
PolicyTraits::destroy(&alloc_ref(), it.slot_);
|
|
erase_meta_only(it);
|
|
}
|
|
|
|
iterator erase(const_iterator first, const_iterator last) {
|
|
while (first != last) {
|
|
erase(first++);
|
|
}
|
|
return last.inner_;
|
|
}
|
|
|
|
// Moves elements from `src` into `this`.
|
|
// If the element already exists in `this`, it is left unmodified in `src`.
|
|
template <typename H, typename E>
|
|
void merge(raw_hash_set<Policy, H, E, Alloc>& src) { // NOLINT
|
|
assert(this != &src);
|
|
for (auto it = src.begin(), e = src.end(); it != e; ++it) {
|
|
if (PolicyTraits::apply(InsertSlot<false>{*this, std::move(*it.slot_)},
|
|
PolicyTraits::element(it.slot_))
|
|
.second) {
|
|
src.erase_meta_only(it);
|
|
}
|
|
}
|
|
}
|
|
|
|
template <typename H, typename E>
|
|
void merge(raw_hash_set<Policy, H, E, Alloc>&& src) {
|
|
merge(src);
|
|
}
|
|
|
|
node_type extract(const_iterator position) {
|
|
node_type node(alloc_ref(), position.inner_.slot_);
|
|
erase_meta_only(position);
|
|
return node;
|
|
}
|
|
|
|
template <
|
|
class K = key_type,
|
|
typename std::enable_if<!std::is_same<K, iterator>::value, int>::type = 0>
|
|
node_type extract(const key_arg<K>& key) {
|
|
auto it = find(key);
|
|
return it == end() ? node_type() : extract(const_iterator{it});
|
|
}
|
|
|
|
void swap(raw_hash_set& that) noexcept(
|
|
IsNoThrowSwappable<hasher>() && IsNoThrowSwappable<key_equal>() &&
|
|
(!AllocTraits::propagate_on_container_swap::value ||
|
|
IsNoThrowSwappable<allocator_type>())) {
|
|
using std::swap;
|
|
swap(ctrl_, that.ctrl_);
|
|
swap(slots_, that.slots_);
|
|
swap(size_, that.size_);
|
|
swap(capacity_, that.capacity_);
|
|
swap(growth_left(), that.growth_left());
|
|
swap(hash_ref(), that.hash_ref());
|
|
swap(eq_ref(), that.eq_ref());
|
|
if (AllocTraits::propagate_on_container_swap::value) {
|
|
swap(alloc_ref(), that.alloc_ref());
|
|
} else {
|
|
// If the allocators do not compare equal it is officially undefined
|
|
// behavior. We choose to do nothing.
|
|
}
|
|
}
|
|
|
|
void rehash(size_t n) {
|
|
if (n == 0 && capacity_ == 0) return;
|
|
if (n == 0 && size_ == 0) return destroy_slots();
|
|
auto m = NormalizeCapacity(std::max(n, NumSlotsFast(size())));
|
|
// n == 0 unconditionally rehashes as per the standard.
|
|
if (n == 0 || m > capacity_) {
|
|
resize(m);
|
|
}
|
|
}
|
|
|
|
void reserve(size_t n) {
|
|
rehash(NumSlotsFast(n));
|
|
}
|
|
|
|
// Extension API: support for heterogeneous keys.
|
|
//
|
|
// std::unordered_set<std::string> s;
|
|
// // Turns "abc" into std::string.
|
|
// s.count("abc");
|
|
//
|
|
// ch_set<std::string> s;
|
|
// // Uses "abc" directly without copying it into std::string.
|
|
// s.count("abc");
|
|
template <class K = key_type>
|
|
size_t count(const key_arg<K>& key) const {
|
|
return find(key) == end() ? 0 : 1;
|
|
}
|
|
|
|
// Issues CPU prefetch instructions for the memory needed to find or insert
|
|
// a key. Like all lookup functions, this support heterogeneous keys.
|
|
//
|
|
// NOTE: This is a very low level operation and should not be used without
|
|
// specific benchmarks indicating its importance.
|
|
template <class K = key_type>
|
|
void prefetch(const key_arg<K>& key) const {
|
|
(void)key;
|
|
#if defined(__GNUC__)
|
|
auto seq = probe(hash_ref()(key));
|
|
__builtin_prefetch(static_cast<const void*>(ctrl_ + seq.offset()));
|
|
__builtin_prefetch(static_cast<const void*>(slots_ + seq.offset()));
|
|
#endif // __GNUC__
|
|
}
|
|
|
|
// The API of find() has two extensions.
|
|
//
|
|
// 1. The hash can be passed by the user. It must be equal to the hash of the
|
|
// key.
|
|
//
|
|
// 2. The type of the key argument doesn't have to be key_type. This is so
|
|
// called heterogeneous key support.
|
|
template <class K = key_type>
|
|
iterator find(const key_arg<K>& key, size_t hash) {
|
|
auto seq = probe(hash);
|
|
while (true) {
|
|
Group g{ctrl_ + seq.offset()};
|
|
for (int i : g.Match(H2(hash))) {
|
|
if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
|
|
EqualElement<K>{key, eq_ref()},
|
|
PolicyTraits::element(slots_ + seq.offset(i)))))
|
|
return iterator_at(seq.offset(i));
|
|
}
|
|
if (ABSL_PREDICT_TRUE(g.MatchEmpty())) return end();
|
|
seq.next();
|
|
}
|
|
}
|
|
template <class K = key_type>
|
|
iterator find(const key_arg<K>& key) {
|
|
return find(key, hash_ref()(key));
|
|
}
|
|
|
|
template <class K = key_type>
|
|
const_iterator find(const key_arg<K>& key, size_t hash) const {
|
|
return const_cast<raw_hash_set*>(this)->find(key, hash);
|
|
}
|
|
template <class K = key_type>
|
|
const_iterator find(const key_arg<K>& key) const {
|
|
return find(key, hash_ref()(key));
|
|
}
|
|
|
|
template <class K = key_type>
|
|
bool contains(const key_arg<K>& key) const {
|
|
return find(key) != end();
|
|
}
|
|
|
|
template <class K = key_type>
|
|
std::pair<iterator, iterator> equal_range(const key_arg<K>& key) {
|
|
auto it = find(key);
|
|
if (it != end()) return {it, std::next(it)};
|
|
return {it, it};
|
|
}
|
|
template <class K = key_type>
|
|
std::pair<const_iterator, const_iterator> equal_range(
|
|
const key_arg<K>& key) const {
|
|
auto it = find(key);
|
|
if (it != end()) return {it, std::next(it)};
|
|
return {it, it};
|
|
}
|
|
|
|
size_t bucket_count() const { return capacity_; }
|
|
float load_factor() const {
|
|
return capacity_ ? static_cast<double>(size()) / capacity_ : 0.0;
|
|
}
|
|
float max_load_factor() const { return 1.0f; }
|
|
void max_load_factor(float) {
|
|
// Does nothing.
|
|
}
|
|
|
|
hasher hash_function() const { return hash_ref(); }
|
|
key_equal key_eq() const { return eq_ref(); }
|
|
allocator_type get_allocator() const { return alloc_ref(); }
|
|
|
|
friend bool operator==(const raw_hash_set& a, const raw_hash_set& b) {
|
|
if (a.size() != b.size()) return false;
|
|
const raw_hash_set* outer = &a;
|
|
const raw_hash_set* inner = &b;
|
|
if (outer->capacity() > inner->capacity()) std::swap(outer, inner);
|
|
for (const value_type& elem : *outer)
|
|
if (!inner->has_element(elem)) return false;
|
|
return true;
|
|
}
|
|
|
|
friend bool operator!=(const raw_hash_set& a, const raw_hash_set& b) {
|
|
return !(a == b);
|
|
}
|
|
|
|
friend void swap(raw_hash_set& a,
|
|
raw_hash_set& b) noexcept(noexcept(a.swap(b))) {
|
|
a.swap(b);
|
|
}
|
|
|
|
private:
|
|
template <class Container, typename Enabler>
|
|
friend struct absl::container_internal::hashtable_debug_internal::
|
|
HashtableDebugAccess;
|
|
|
|
struct FindElement {
|
|
template <class K, class... Args>
|
|
const_iterator operator()(const K& key, Args&&...) const {
|
|
return s.find(key);
|
|
}
|
|
const raw_hash_set& s;
|
|
};
|
|
|
|
struct HashElement {
|
|
template <class K, class... Args>
|
|
size_t operator()(const K& key, Args&&...) const {
|
|
return h(key);
|
|
}
|
|
const hasher& h;
|
|
};
|
|
|
|
template <class K1>
|
|
struct EqualElement {
|
|
template <class K2, class... Args>
|
|
bool operator()(const K2& lhs, Args&&...) const {
|
|
return eq(lhs, rhs);
|
|
}
|
|
const K1& rhs;
|
|
const key_equal& eq;
|
|
};
|
|
|
|
struct EmplaceDecomposable {
|
|
template <class K, class... Args>
|
|
std::pair<iterator, bool> operator()(const K& key, Args&&... args) const {
|
|
auto res = s.find_or_prepare_insert(key);
|
|
if (res.second) {
|
|
s.emplace_at(res.first, std::forward<Args>(args)...);
|
|
}
|
|
return {s.iterator_at(res.first), res.second};
|
|
}
|
|
raw_hash_set& s;
|
|
};
|
|
|
|
template <bool do_destroy>
|
|
struct InsertSlot {
|
|
template <class K, class... Args>
|
|
std::pair<iterator, bool> operator()(const K& key, Args&&...) && {
|
|
auto res = s.find_or_prepare_insert(key);
|
|
if (res.second) {
|
|
PolicyTraits::transfer(&s.alloc_ref(), s.slots_ + res.first, &slot);
|
|
} else if (do_destroy) {
|
|
PolicyTraits::destroy(&s.alloc_ref(), &slot);
|
|
}
|
|
return {s.iterator_at(res.first), res.second};
|
|
}
|
|
raw_hash_set& s;
|
|
// Constructed slot. Either moved into place or destroyed.
|
|
slot_type&& slot;
|
|
};
|
|
|
|
// Computes std::ceil(n / kMaxLoadFactor). Faster than calling std::ceil.
|
|
static inline size_t NumSlotsFast(size_t n) {
|
|
return static_cast<size_t>(
|
|
(n * kMaxLoadFactorDenominator + (kMaxLoadFactorNumerator - 1)) /
|
|
kMaxLoadFactorNumerator);
|
|
}
|
|
|
|
// "erases" the object from the container, except that it doesn't actually
|
|
// destroy the object. It only updates all the metadata of the class.
|
|
// This can be used in conjunction with Policy::transfer to move the object to
|
|
// another place.
|
|
void erase_meta_only(const_iterator it) {
|
|
assert(IsFull(*it.inner_.ctrl_) && "erasing a dangling iterator");
|
|
--size_;
|
|
const size_t index = it.inner_.ctrl_ - ctrl_;
|
|
const size_t index_before = (index - Group::kWidth) & capacity_;
|
|
const auto empty_after = Group(it.inner_.ctrl_).MatchEmpty();
|
|
const auto empty_before = Group(ctrl_ + index_before).MatchEmpty();
|
|
|
|
// We count how many consecutive non empties we have to the right and to the
|
|
// left of `it`. If the sum is >= kWidth then there is at least one probe
|
|
// window that might have seen a full group.
|
|
bool was_never_full =
|
|
empty_before && empty_after &&
|
|
static_cast<size_t>(empty_after.TrailingZeros() +
|
|
empty_before.LeadingZeros()) < Group::kWidth;
|
|
|
|
set_ctrl(index, was_never_full ? kEmpty : kDeleted);
|
|
growth_left() += was_never_full;
|
|
}
|
|
|
|
void initialize_slots() {
|
|
assert(capacity_);
|
|
auto layout = MakeLayout(capacity_);
|
|
char* mem = static_cast<char*>(
|
|
Allocate<Layout::Alignment()>(&alloc_ref(), layout.AllocSize()));
|
|
ctrl_ = reinterpret_cast<ctrl_t*>(layout.template Pointer<0>(mem));
|
|
slots_ = layout.template Pointer<1>(mem);
|
|
reset_ctrl();
|
|
growth_left() = static_cast<size_t>(capacity_ * kMaxLoadFactor) - size_;
|
|
}
|
|
|
|
void destroy_slots() {
|
|
if (!capacity_) return;
|
|
for (size_t i = 0; i != capacity_; ++i) {
|
|
if (IsFull(ctrl_[i])) {
|
|
PolicyTraits::destroy(&alloc_ref(), slots_ + i);
|
|
}
|
|
}
|
|
auto layout = MakeLayout(capacity_);
|
|
// Unpoison before returning the memory to the allocator.
|
|
SanitizerUnpoisonMemoryRegion(slots_, sizeof(slot_type) * capacity_);
|
|
Deallocate<Layout::Alignment()>(&alloc_ref(), ctrl_, layout.AllocSize());
|
|
ctrl_ = EmptyGroup();
|
|
slots_ = nullptr;
|
|
size_ = 0;
|
|
capacity_ = 0;
|
|
growth_left() = 0;
|
|
}
|
|
|
|
void resize(size_t new_capacity) {
|
|
assert(IsValidCapacity(new_capacity));
|
|
auto* old_ctrl = ctrl_;
|
|
auto* old_slots = slots_;
|
|
const size_t old_capacity = capacity_;
|
|
capacity_ = new_capacity;
|
|
initialize_slots();
|
|
|
|
for (size_t i = 0; i != old_capacity; ++i) {
|
|
if (IsFull(old_ctrl[i])) {
|
|
size_t hash = PolicyTraits::apply(HashElement{hash_ref()},
|
|
PolicyTraits::element(old_slots + i));
|
|
size_t new_i = find_first_non_full(hash);
|
|
set_ctrl(new_i, H2(hash));
|
|
PolicyTraits::transfer(&alloc_ref(), slots_ + new_i, old_slots + i);
|
|
}
|
|
}
|
|
if (old_capacity) {
|
|
SanitizerUnpoisonMemoryRegion(old_slots,
|
|
sizeof(slot_type) * old_capacity);
|
|
auto layout = MakeLayout(old_capacity);
|
|
Deallocate<Layout::Alignment()>(&alloc_ref(), old_ctrl,
|
|
layout.AllocSize());
|
|
}
|
|
}
|
|
|
|
void drop_deletes_without_resize() ABSL_ATTRIBUTE_NOINLINE {
|
|
assert(IsValidCapacity(capacity_));
|
|
// Algorithm:
|
|
// - mark all DELETED slots as EMPTY
|
|
// - mark all FULL slots as DELETED
|
|
// - for each slot marked as DELETED
|
|
// hash = Hash(element)
|
|
// target = find_first_non_full(hash)
|
|
// if target is in the same group
|
|
// mark slot as FULL
|
|
// else if target is EMPTY
|
|
// transfer element to target
|
|
// mark slot as EMPTY
|
|
// mark target as FULL
|
|
// else if target is DELETED
|
|
// swap current element with target element
|
|
// mark target as FULL
|
|
// repeat procedure for current slot with moved from element (target)
|
|
ConvertDeletedToEmptyAndFullToDeleted(ctrl_, capacity_);
|
|
typename std::aligned_storage<sizeof(slot_type), alignof(slot_type)>::type
|
|
raw;
|
|
slot_type* slot = reinterpret_cast<slot_type*>(&raw);
|
|
for (size_t i = 0; i != capacity_; ++i) {
|
|
if (!IsDeleted(ctrl_[i])) continue;
|
|
size_t hash = PolicyTraits::apply(HashElement{hash_ref()},
|
|
PolicyTraits::element(slots_ + i));
|
|
size_t new_i = find_first_non_full(hash);
|
|
|
|
// Verify if the old and new i fall within the same group wrt the hash.
|
|
// If they do, we don't need to move the object as it falls already in the
|
|
// best probe we can.
|
|
const auto probe_index = [&](size_t pos) {
|
|
return ((pos - probe(hash).offset()) & capacity_) / Group::kWidth;
|
|
};
|
|
|
|
// Element doesn't move.
|
|
if (ABSL_PREDICT_TRUE(probe_index(new_i) == probe_index(i))) {
|
|
set_ctrl(i, H2(hash));
|
|
continue;
|
|
}
|
|
if (IsEmpty(ctrl_[new_i])) {
|
|
// Transfer element to the empty spot.
|
|
// set_ctrl poisons/unpoisons the slots so we have to call it at the
|
|
// right time.
|
|
set_ctrl(new_i, H2(hash));
|
|
PolicyTraits::transfer(&alloc_ref(), slots_ + new_i, slots_ + i);
|
|
set_ctrl(i, kEmpty);
|
|
} else {
|
|
assert(IsDeleted(ctrl_[new_i]));
|
|
set_ctrl(new_i, H2(hash));
|
|
// Until we are done rehashing, DELETED marks previously FULL slots.
|
|
// Swap i and new_i elements.
|
|
PolicyTraits::transfer(&alloc_ref(), slot, slots_ + i);
|
|
PolicyTraits::transfer(&alloc_ref(), slots_ + i, slots_ + new_i);
|
|
PolicyTraits::transfer(&alloc_ref(), slots_ + new_i, slot);
|
|
--i; // repeat
|
|
}
|
|
}
|
|
growth_left() = static_cast<size_t>(capacity_ * kMaxLoadFactor) - size_;
|
|
}
|
|
|
|
void rehash_and_grow_if_necessary() {
|
|
if (capacity_ == 0) {
|
|
resize(Group::kWidth - 1);
|
|
} else if (size() <= kMaxLoadFactor / 2 * capacity_) {
|
|
// Squash DELETED without growing if there is enough capacity.
|
|
drop_deletes_without_resize();
|
|
} else {
|
|
// Otherwise grow the container.
|
|
resize(capacity_ * 2 + 1);
|
|
}
|
|
}
|
|
|
|
bool has_element(const value_type& elem) const {
|
|
size_t hash = PolicyTraits::apply(HashElement{hash_ref()}, elem);
|
|
auto seq = probe(hash);
|
|
while (true) {
|
|
Group g{ctrl_ + seq.offset()};
|
|
for (int i : g.Match(H2(hash))) {
|
|
if (ABSL_PREDICT_TRUE(PolicyTraits::element(slots_ + seq.offset(i)) ==
|
|
elem))
|
|
return true;
|
|
}
|
|
if (ABSL_PREDICT_TRUE(g.MatchEmpty())) return false;
|
|
seq.next();
|
|
assert(seq.index() < capacity_ && "full table!");
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Probes the raw_hash_set with the probe sequence for hash and returns the
|
|
// pointer to the first empty or deleted slot.
|
|
// NOTE: this function must work with tables having both kEmpty and kDelete
|
|
// in one group. Such tables appears during drop_deletes_without_resize.
|
|
//
|
|
// This function is very useful when insertions happen and:
|
|
// - the input is already a set
|
|
// - there are enough slots
|
|
// - the element with the hash is not in the table
|
|
size_t find_first_non_full(size_t hash) {
|
|
auto seq = probe(hash);
|
|
while (true) {
|
|
Group g{ctrl_ + seq.offset()};
|
|
auto mask = g.MatchEmptyOrDeleted();
|
|
if (mask) {
|
|
#if !defined(NDEBUG)
|
|
// We want to force small tables to have random entries too, so
|
|
// in debug build we will randomly insert in either the front or back of
|
|
// the group.
|
|
// TODO(kfm,sbenza): revisit after we do unconditional mixing
|
|
if (ShouldInsertBackwards(hash, ctrl_))
|
|
return seq.offset(mask.HighestBitSet());
|
|
else
|
|
return seq.offset(mask.LowestBitSet());
|
|
#else
|
|
return seq.offset(mask.LowestBitSet());
|
|
#endif
|
|
}
|
|
assert(seq.index() < capacity_ && "full table!");
|
|
seq.next();
|
|
}
|
|
}
|
|
|
|
// TODO(alkis): Optimize this assuming *this and that don't overlap.
|
|
raw_hash_set& move_assign(raw_hash_set&& that, std::true_type) {
|
|
raw_hash_set tmp(std::move(that));
|
|
swap(tmp);
|
|
return *this;
|
|
}
|
|
raw_hash_set& move_assign(raw_hash_set&& that, std::false_type) {
|
|
raw_hash_set tmp(std::move(that), alloc_ref());
|
|
swap(tmp);
|
|
return *this;
|
|
}
|
|
|
|
protected:
|
|
template <class K>
|
|
std::pair<size_t, bool> find_or_prepare_insert(const K& key) {
|
|
auto hash = hash_ref()(key);
|
|
auto seq = probe(hash);
|
|
while (true) {
|
|
Group g{ctrl_ + seq.offset()};
|
|
for (int i : g.Match(H2(hash))) {
|
|
if (ABSL_PREDICT_TRUE(PolicyTraits::apply(
|
|
EqualElement<K>{key, eq_ref()},
|
|
PolicyTraits::element(slots_ + seq.offset(i)))))
|
|
return {seq.offset(i), false};
|
|
}
|
|
if (ABSL_PREDICT_TRUE(g.MatchEmpty())) break;
|
|
seq.next();
|
|
}
|
|
return {prepare_insert(hash), true};
|
|
}
|
|
|
|
size_t prepare_insert(size_t hash) ABSL_ATTRIBUTE_NOINLINE {
|
|
size_t target = find_first_non_full(hash);
|
|
if (ABSL_PREDICT_FALSE(growth_left() == 0 && !IsDeleted(ctrl_[target]))) {
|
|
rehash_and_grow_if_necessary();
|
|
target = find_first_non_full(hash);
|
|
}
|
|
++size_;
|
|
growth_left() -= IsEmpty(ctrl_[target]);
|
|
set_ctrl(target, H2(hash));
|
|
return target;
|
|
}
|
|
|
|
// Constructs the value in the space pointed by the iterator. This only works
|
|
// after an unsuccessful find_or_prepare_insert() and before any other
|
|
// modifications happen in the raw_hash_set.
|
|
//
|
|
// PRECONDITION: i is an index returned from find_or_prepare_insert(k), where
|
|
// k is the key decomposed from `forward<Args>(args)...`, and the bool
|
|
// returned by find_or_prepare_insert(k) was true.
|
|
// POSTCONDITION: *m.iterator_at(i) == value_type(forward<Args>(args)...).
|
|
template <class... Args>
|
|
void emplace_at(size_t i, Args&&... args) {
|
|
PolicyTraits::construct(&alloc_ref(), slots_ + i,
|
|
std::forward<Args>(args)...);
|
|
|
|
assert(PolicyTraits::apply(FindElement{*this}, *iterator_at(i)) ==
|
|
iterator_at(i) &&
|
|
"constructed value does not match the lookup key");
|
|
}
|
|
|
|
iterator iterator_at(size_t i) { return {ctrl_ + i, slots_ + i}; }
|
|
const_iterator iterator_at(size_t i) const { return {ctrl_ + i, slots_ + i}; }
|
|
|
|
private:
|
|
friend struct RawHashSetTestOnlyAccess;
|
|
|
|
probe_seq<Group::kWidth> probe(size_t hash) const {
|
|
return probe_seq<Group::kWidth>(H1(hash, ctrl_), capacity_);
|
|
}
|
|
|
|
// Reset all ctrl bytes back to kEmpty, except the sentinel.
|
|
void reset_ctrl() {
|
|
std::memset(ctrl_, kEmpty, capacity_ + Group::kWidth);
|
|
ctrl_[capacity_] = kSentinel;
|
|
SanitizerPoisonMemoryRegion(slots_, sizeof(slot_type) * capacity_);
|
|
}
|
|
|
|
// Sets the control byte, and if `i < Group::kWidth`, set the cloned byte at
|
|
// the end too.
|
|
void set_ctrl(size_t i, ctrl_t h) {
|
|
assert(i < capacity_);
|
|
|
|
if (IsFull(h)) {
|
|
SanitizerUnpoisonObject(slots_ + i);
|
|
} else {
|
|
SanitizerPoisonObject(slots_ + i);
|
|
}
|
|
|
|
ctrl_[i] = h;
|
|
ctrl_[((i - Group::kWidth) & capacity_) + Group::kWidth] = h;
|
|
}
|
|
|
|
size_t& growth_left() { return settings_.template get<0>(); }
|
|
|
|
hasher& hash_ref() { return settings_.template get<1>(); }
|
|
const hasher& hash_ref() const { return settings_.template get<1>(); }
|
|
key_equal& eq_ref() { return settings_.template get<2>(); }
|
|
const key_equal& eq_ref() const { return settings_.template get<2>(); }
|
|
allocator_type& alloc_ref() { return settings_.template get<3>(); }
|
|
const allocator_type& alloc_ref() const {
|
|
return settings_.template get<3>();
|
|
}
|
|
|
|
// On average each group has 2 empty slot (for the vectorized case).
|
|
static constexpr int64_t kMaxLoadFactorNumerator = 14;
|
|
static constexpr int64_t kMaxLoadFactorDenominator = 16;
|
|
static constexpr float kMaxLoadFactor =
|
|
1.0 * kMaxLoadFactorNumerator / kMaxLoadFactorDenominator;
|
|
|
|
// TODO(alkis): Investigate removing some of these fields:
|
|
// - ctrl/slots can be derived from each other
|
|
// - size can be moved into the slot array
|
|
ctrl_t* ctrl_ = EmptyGroup(); // [(capacity + 1) * ctrl_t]
|
|
slot_type* slots_ = nullptr; // [capacity * slot_type]
|
|
size_t size_ = 0; // number of full slots
|
|
size_t capacity_ = 0; // total number of slots
|
|
absl::container_internal::CompressedTuple<size_t /* growth_left */, hasher,
|
|
key_equal, allocator_type>
|
|
settings_{0, hasher{}, key_equal{}, allocator_type{}};
|
|
};
|
|
|
|
namespace hashtable_debug_internal {
|
|
template <typename Set>
|
|
struct HashtableDebugAccess<Set, absl::void_t<typename Set::raw_hash_set>> {
|
|
using Traits = typename Set::PolicyTraits;
|
|
using Slot = typename Traits::slot_type;
|
|
|
|
static size_t GetNumProbes(const Set& set,
|
|
const typename Set::key_type& key) {
|
|
size_t num_probes = 0;
|
|
size_t hash = set.hash_ref()(key);
|
|
auto seq = set.probe(hash);
|
|
while (true) {
|
|
container_internal::Group g{set.ctrl_ + seq.offset()};
|
|
for (int i : g.Match(container_internal::H2(hash))) {
|
|
if (Traits::apply(
|
|
typename Set::template EqualElement<typename Set::key_type>{
|
|
key, set.eq_ref()},
|
|
Traits::element(set.slots_ + seq.offset(i))))
|
|
return num_probes;
|
|
++num_probes;
|
|
}
|
|
if (g.MatchEmpty()) return num_probes;
|
|
seq.next();
|
|
++num_probes;
|
|
}
|
|
}
|
|
|
|
static size_t AllocatedByteSize(const Set& c) {
|
|
size_t capacity = c.capacity_;
|
|
if (capacity == 0) return 0;
|
|
auto layout = Set::MakeLayout(capacity);
|
|
size_t m = layout.AllocSize();
|
|
|
|
size_t per_slot = Traits::space_used(static_cast<const Slot*>(nullptr));
|
|
if (per_slot != ~size_t{}) {
|
|
m += per_slot * c.size();
|
|
} else {
|
|
for (size_t i = 0; i != capacity; ++i) {
|
|
if (container_internal::IsFull(c.ctrl_[i])) {
|
|
m += Traits::space_used(c.slots_ + i);
|
|
}
|
|
}
|
|
}
|
|
return m;
|
|
}
|
|
|
|
static size_t LowerBoundAllocatedByteSize(size_t size) {
|
|
size_t capacity = container_internal::NormalizeCapacity(
|
|
std::ceil(size / Set::kMaxLoadFactor));
|
|
if (capacity == 0) return 0;
|
|
auto layout = Set::MakeLayout(capacity);
|
|
size_t m = layout.AllocSize();
|
|
size_t per_slot = Traits::space_used(static_cast<const Slot*>(nullptr));
|
|
if (per_slot != ~size_t{}) {
|
|
m += per_slot * size;
|
|
}
|
|
return m;
|
|
}
|
|
};
|
|
|
|
} // namespace hashtable_debug_internal
|
|
} // namespace container_internal
|
|
} // namespace absl
|
|
|
|
#endif // ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
|