summaryrefslogtreecommitdiff
path: root/absl/container/internal/raw_hash_set.h
diff options
context:
space:
mode:
Diffstat (limited to 'absl/container/internal/raw_hash_set.h')
-rw-r--r--absl/container/internal/raw_hash_set.h1906
1 files changed, 1906 insertions, 0 deletions
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
new file mode 100644
index 00000000..0c0e5906
--- /dev/null
+++ b/absl/container/internal/raw_hash_set.h
@@ -0,0 +1,1906 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// An open-addressing
+// hashtable with quadratic probing.
+//
+// This is a low level hashtable on top of which different interfaces can be
+// implemented, like flat_hash_set, node_hash_set, string_hash_set, etc.
+//
+// The table interface is similar to that of std::unordered_set. Notable
+// differences are that most member functions support heterogeneous keys when
+// BOTH the hash and eq functions are marked as transparent. They do so by
+// providing a typedef called `is_transparent`.
+//
+// When heterogeneous lookup is enabled, functions that take key_type act as if
+// they have an overload set like:
+//
+// iterator find(const key_type& key);
+// template <class K>
+// iterator find(const K& key);
+//
+// size_type erase(const key_type& key);
+// template <class K>
+// size_type erase(const K& key);
+//
+// std::pair<iterator, iterator> equal_range(const key_type& key);
+// template <class K>
+// std::pair<iterator, iterator> equal_range(const K& key);
+//
+// When heterogeneous lookup is disabled, only the explicit `key_type` overloads
+// exist.
+//
+// find() also supports passing the hash explicitly:
+//
+// iterator find(const key_type& key, size_t hash);
+// template <class U>
+// iterator find(const U& key, size_t hash);
+//
+// In addition the pointer to element and iterator stability guarantees are
+// weaker: all iterators and pointers are invalidated after a new element is
+// inserted.
+//
+// IMPLEMENTATION DETAILS
+//
+// The table stores elements inline in a slot array. In addition to the slot
+// array the table maintains some control state per slot. The extra state is one
+// byte per slot and stores empty or deleted marks, or alternatively 7 bits from
+// the hash of an occupied slot. The table is split into logical groups of
+// slots, like so:
+//
+// Group 1 Group 2 Group 3
+// +---------------+---------------+---------------+
+// | | | | | | | | | | | | | | | | | | | | | | | | |
+// +---------------+---------------+---------------+
+//
+// On lookup the hash is split into two parts:
+// - H2: 7 bits (those stored in the control bytes)
+// - H1: the rest of the bits
+// The groups are probed using H1. For each group the slots are matched to H2 in
+// parallel. Because H2 is 7 bits (128 states) and the number of slots per group
+// is low (8 or 16) in almost all cases a match in H2 is also a lookup hit.
+//
+// On insert, once the right group is found (as in lookup), its slots are
+// filled in order.
+//
+// On erase a slot is cleared. In case the group did not have any empty slots
+// before the erase, the erased slot is marked as deleted.
+//
+// Groups without empty slots (but maybe with deleted slots) extend the probe
+// sequence. The probing algorithm is quadratic. Given N the number of groups,
+// the probing function for the i'th probe is:
+//
+// P(0) = H1 % N
+//
+// P(i) = (P(i - 1) + i) % N
+//
+// This probing function guarantees that after N probes, all the groups of the
+// table will be probed exactly once.
+
+#ifndef ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
+#define ABSL_CONTAINER_INTERNAL_RAW_HASH_SET_H_
+
+#ifndef SWISSTABLE_HAVE_SSE2
+#ifdef __SSE2__
+#define SWISSTABLE_HAVE_SSE2 1
+#else
+#define SWISSTABLE_HAVE_SSE2 0
+#endif
+#endif
+
+#ifndef SWISSTABLE_HAVE_SSSE3
+#ifdef __SSSE3__
+#define SWISSTABLE_HAVE_SSSE3 1
+#else
+#define SWISSTABLE_HAVE_SSSE3 0
+#endif
+#endif
+
+#if SWISSTABLE_HAVE_SSSE3 && !SWISSTABLE_HAVE_SSE2
+#error "Bad configuration!"
+#endif
+
+#if SWISSTABLE_HAVE_SSE2
+#include <x86intrin.h>
+#endif
+
+#include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/internal/bits.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/port.h"
+#include "absl/container/internal/compressed_tuple.h"
+#include "absl/container/internal/container_memory.h"
+#include "absl/container/internal/hash_policy_traits.h"
+#include "absl/container/internal/hashtable_debug_hooks.h"
+#include "absl/container/internal/layout.h"
+#include "absl/memory/memory.h"
+#include "absl/meta/type_traits.h"
+#include "absl/types/optional.h"
+#include "absl/utility/utility.h"
+
+namespace absl {
+namespace container_internal {
+
+template <size_t Width>
+class probe_seq {
+ public:
+ probe_seq(size_t hash, size_t mask) {
+ assert(((mask + 1) & mask) == 0 && "not a mask");
+ mask_ = mask;
+ offset_ = hash & mask_;
+ }
+ size_t offset() const { return offset_; }
+ size_t offset(size_t i) const { return (offset_ + i) & mask_; }
+
+ void next() {
+ index_ += Width;
+ offset_ += index_;
+ offset_ &= mask_;
+ }
+ // 0-based probe index. The i-th probe in the probe sequence.
+ size_t index() const { return index_; }
+
+ private:
+ size_t mask_;
+ size_t offset_;
+ size_t index_ = 0;
+};
+
+template <class ContainerKey, class Hash, class Eq>
+struct RequireUsableKey {
+ template <class PassedKey, class... Args>
+ std::pair<
+ decltype(std::declval<const Hash&>()(std::declval<const PassedKey&>())),
+ decltype(std::declval<const Eq&>()(std::declval<const ContainerKey&>(),
+ std::declval<const PassedKey&>()))>*
+ operator()(const PassedKey&, const Args&...) const;
+};
+
+template <class E, class Policy, class Hash, class Eq, class... Ts>
+struct IsDecomposable : std::false_type {};
+
+template <class Policy, class Hash, class Eq, class... Ts>
+struct IsDecomposable<
+ absl::void_t<decltype(
+ Policy::apply(RequireUsableKey<typename Policy::key_type, Hash, Eq>(),
+ std::declval<Ts>()...))>,
+ Policy, Hash, Eq, Ts...> : std::true_type {};
+
+template <class, class = void>
+struct IsTransparent : std::false_type {};
+template <class T>
+struct IsTransparent<T, absl::void_t<typename T::is_transparent>>
+ : std::true_type {};
+
+// TODO(alkis): Switch to std::is_nothrow_swappable when gcc/clang supports it.
+template <class T>
+constexpr bool IsNoThrowSwappable() {
+ using std::swap;
+ return noexcept(swap(std::declval<T&>(), std::declval<T&>()));
+}
+
+template <typename T>
+int TrailingZeros(T x) {
+ return sizeof(T) == 8 ? base_internal::CountTrailingZerosNonZero64(x)
+ : base_internal::CountTrailingZerosNonZero32(x);
+}
+
+template <typename T>
+int LeadingZeros(T x) {
+ return sizeof(T) == 8 ? base_internal::CountLeadingZeros64(x)
+ : base_internal::CountLeadingZeros32(x);
+}
+
+// An abstraction over a bitmask. It provides an easy way to iterate through the
+// indexes of the set bits of a bitmask. When Shift=0 (platforms with SSE),
+// this is a true bitmask. On non-SSE, platforms the arithematic used to
+// emulate the SSE behavior works in bytes (Shift=3) and leaves each bytes as
+// either 0x00 or 0x80.
+//
+// For example:
+// for (int i : BitMask<uint32_t, 16>(0x5)) -> yields 0, 2
+// for (int i : BitMask<uint64_t, 8, 3>(0x0000000080800000)) -> yields 2, 3
+template <class T, int SignificantBits, int Shift = 0>
+class BitMask {
+ static_assert(std::is_unsigned<T>::value, "");
+ static_assert(Shift == 0 || Shift == 3, "");
+
+ public:
+ // These are useful for unit tests (gunit).
+ using value_type = int;
+ using iterator = BitMask;
+ using const_iterator = BitMask;
+
+ explicit BitMask(T mask) : mask_(mask) {}
+ BitMask& operator++() {
+ mask_ &= (mask_ - 1);
+ return *this;
+ }
+ explicit operator bool() const { return mask_ != 0; }
+ int operator*() const { return LowestBitSet(); }
+ int LowestBitSet() const {
+ return container_internal::TrailingZeros(mask_) >> Shift;
+ }
+ int HighestBitSet() const {
+ return (sizeof(T) * CHAR_BIT - container_internal::LeadingZeros(mask_) -
+ 1) >>
+ Shift;
+ }
+
+ BitMask begin() const { return *this; }
+ BitMask end() const { return BitMask(0); }
+
+ int TrailingZeros() const {
+ return container_internal::TrailingZeros(mask_) >> Shift;
+ }
+
+ int LeadingZeros() const {
+ constexpr int total_significant_bits = SignificantBits << Shift;
+ constexpr int extra_bits = sizeof(T) * 8 - total_significant_bits;
+ return container_internal::LeadingZeros(mask_ << extra_bits) >> Shift;
+ }
+
+ private:
+ friend bool operator==(const BitMask& a, const BitMask& b) {
+ return a.mask_ == b.mask_;
+ }
+ friend bool operator!=(const BitMask& a, const BitMask& b) {
+ return a.mask_ != b.mask_;
+ }
+
+ T mask_;
+};
+
+using ctrl_t = signed char;
+using h2_t = uint8_t;
+
+// The values here are selected for maximum performance. See the static asserts
+// below for details.
+enum Ctrl : ctrl_t {
+ kEmpty = -128, // 0b10000000
+ kDeleted = -2, // 0b11111110
+ kSentinel = -1, // 0b11111111
+};
+static_assert(
+ kEmpty & kDeleted & kSentinel & 0x80,
+ "Special markers need to have the MSB to make checking for them efficient");
+static_assert(kEmpty < kSentinel && kDeleted < kSentinel,
+ "kEmpty and kDeleted must be smaller than kSentinel to make the "
+ "SIMD test of IsEmptyOrDeleted() efficient");
+static_assert(kSentinel == -1,
+ "kSentinel must be -1 to elide loading it from memory into SIMD "
+ "registers (pcmpeqd xmm, xmm)");
+static_assert(kEmpty == -128,
+ "kEmpty must be -128 to make the SIMD check for its "
+ "existence efficient (psignb xmm, xmm)");
+static_assert(~kEmpty & ~kDeleted & kSentinel & 0x7F,
+ "kEmpty and kDeleted must share an unset bit that is not shared "
+ "by kSentinel to make the scalar test for MatchEmptyOrDeleted() "
+ "efficient");
+static_assert(kDeleted == -2,
+ "kDeleted must be -2 to make the implementation of "
+ "ConvertSpecialToEmptyAndFullToDeleted efficient");
+
+// A single block of empty control bytes for tables without any slots allocated.
+// This enables removing a branch in the hot path of find().
+inline ctrl_t* EmptyGroup() {
+ alignas(16) static constexpr ctrl_t empty_group[] = {
+ kSentinel, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty,
+ kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty, kEmpty};
+ return const_cast<ctrl_t*>(empty_group);
+}
+
+// Mixes a randomly generated per-process seed with `hash` and `ctrl` to
+// randomize insertion order within groups.
+bool ShouldInsertBackwards(size_t hash, ctrl_t* ctrl);
+
+// Returns a hash seed.
+//
+// The seed consists of the ctrl_ pointer, which adds enough entropy to ensure
+// non-determinism of iteration order in most cases.
+inline size_t HashSeed(const ctrl_t* ctrl) {
+ // The low bits of the pointer have little or no entropy because of
+ // alignment. We shift the pointer to try to use higher entropy bits. A
+ // good number seems to be 12 bits, because that aligns with page size.
+ return reinterpret_cast<uintptr_t>(ctrl) >> 12;
+}
+
+inline size_t H1(size_t hash, const ctrl_t* ctrl) {
+ return (hash >> 7) ^ HashSeed(ctrl);
+}
+inline ctrl_t H2(size_t hash) { return hash & 0x7F; }
+
+inline bool IsEmpty(ctrl_t c) { return c == kEmpty; }
+inline bool IsFull(ctrl_t c) { return c >= 0; }
+inline bool IsDeleted(ctrl_t c) { return c == kDeleted; }
+inline bool IsEmptyOrDeleted(ctrl_t c) { return c < kSentinel; }
+
+#if SWISSTABLE_HAVE_SSE2
+struct Group {
+ static constexpr size_t kWidth = 16; // the number of slots per group
+
+ explicit Group(const ctrl_t* pos) {
+ ctrl = _mm_loadu_si128(reinterpret_cast<const __m128i*>(pos));
+ }
+
+ // Returns a bitmask representing the positions of slots that match hash.
+ BitMask<uint32_t, kWidth> Match(h2_t hash) const {
+ auto match = _mm_set1_epi8(hash);
+ return BitMask<uint32_t, kWidth>(
+ _mm_movemask_epi8(_mm_cmpeq_epi8(match, ctrl)));
+ }
+
+ // Returns a bitmask representing the positions of empty slots.
+ BitMask<uint32_t, kWidth> MatchEmpty() const {
+#if SWISSTABLE_HAVE_SSSE3
+ // This only works because kEmpty is -128.
+ return BitMask<uint32_t, kWidth>(
+ _mm_movemask_epi8(_mm_sign_epi8(ctrl, ctrl)));
+#else
+ return Match(kEmpty);
+#endif
+ }
+
+ // Returns a bitmask representing the positions of empty or deleted slots.
+ BitMask<uint32_t, kWidth> MatchEmptyOrDeleted() const {
+ auto special = _mm_set1_epi8(kSentinel);
+ return BitMask<uint32_t, kWidth>(
+ _mm_movemask_epi8(_mm_cmpgt_epi8(special, ctrl)));
+ }
+
+ // Returns the number of trailing empty or deleted elements in the group.
+ uint32_t CountLeadingEmptyOrDeleted() const {
+ auto special = _mm_set1_epi8(kSentinel);
+ return TrailingZeros(_mm_movemask_epi8(_mm_cmpgt_epi8(special, ctrl)) + 1);
+ }
+
+ void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
+ auto msbs = _mm_set1_epi8(0x80);
+ auto x126 = _mm_set1_epi8(126);
+#if SWISSTABLE_HAVE_SSSE3
+ auto res = _mm_or_si128(_mm_shuffle_epi8(x126, ctrl), msbs);
+#else
+ auto zero = _mm_setzero_si128();
+ auto special_mask = _mm_cmpgt_epi8(zero, ctrl);
+ auto res = _mm_or_si128(msbs, _mm_andnot_si128(special_mask, x126));
+#endif
+ _mm_storeu_si128(reinterpret_cast<__m128i*>(dst), res);
+ }
+
+ __m128i ctrl;
+};
+#else
+struct Group {
+ static constexpr size_t kWidth = 8;
+
+ explicit Group(const ctrl_t* pos) : ctrl(little_endian::Load64(pos)) {}
+
+ BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
+ // For the technique, see:
+ // http://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
+ // (Determine if a word has a byte equal to n).
+ //
+ // Caveat: there are false positives but:
+ // - they only occur if there is a real match
+ // - they never occur on kEmpty, kDeleted, kSentinel
+ // - they will be handled gracefully by subsequent checks in code
+ //
+ // Example:
+ // v = 0x1716151413121110
+ // hash = 0x12
+ // retval = (v - lsbs) & ~v & msbs = 0x0000000080800000
+ constexpr uint64_t msbs = 0x8080808080808080ULL;
+ constexpr uint64_t lsbs = 0x0101010101010101ULL;
+ auto x = ctrl ^ (lsbs * hash);
+ return BitMask<uint64_t, kWidth, 3>((x - lsbs) & ~x & msbs);
+ }
+
+ BitMask<uint64_t, kWidth, 3> MatchEmpty() const {
+ constexpr uint64_t msbs = 0x8080808080808080ULL;
+ return BitMask<uint64_t, kWidth, 3>((ctrl & (~ctrl << 6)) & msbs);
+ }
+
+ BitMask<uint64_t, kWidth, 3> MatchEmptyOrDeleted() const {
+ constexpr uint64_t msbs = 0x8080808080808080ULL;
+ return BitMask<uint64_t, kWidth, 3>((ctrl & (~ctrl << 7)) & msbs);
+ }
+
+ uint32_t CountLeadingEmptyOrDeleted() const {
+ constexpr uint64_t gaps = 0x00FEFEFEFEFEFEFEULL;
+ return (TrailingZeros(((~ctrl & (ctrl >> 7)) | gaps) + 1) + 7) >> 3;
+ }
+
+ void ConvertSpecialToEmptyAndFullToDeleted(ctrl_t* dst) const {
+ constexpr uint64_t msbs = 0x8080808080808080ULL;
+ constexpr uint64_t lsbs = 0x0101010101010101ULL;
+ auto x = ctrl & msbs;
+ auto res = (~x + (x >> 7)) & ~lsbs;
+ 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 tranparent 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, static_cast<size_t>(std::ceil(size() / kMaxLoadFactor))));
+ // n == 0 unconditionally rehashes as per the standard.
+ if (n == 0 || m > capacity_) {
+ resize(m);
+ }
+ }
+
+ void reserve(size_t n) {
+ rehash(static_cast<size_t>(std::ceil(n / kMaxLoadFactor)));
+ }
+
+ // 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;
+ };
+
+ // "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 float kMaxLoadFactor = 14.0 / 16.0;
+
+ // 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_