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bytell_hash_map.cpp
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bytell_hash_map.cpp
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// Copyright Malte Skarupke 2017.
// Distributed under the Boost Software License, Version 1.0.
// (See http://www.boost.org/LICENSE_1_0.txt)
#pragma once
#include <cstdint>
#include <cstddef>
#include <cmath>
#include <algorithm>
#include <iterator>
#include <utility>
#include <type_traits>
#include "flat_hash_map.hpp"
#include <vector>
#include <array>
namespace ska
{
namespace detailv8
{
using ska::detailv3::functor_storage;
using ska::detailv3::KeyOrValueHasher;
using ska::detailv3::KeyOrValueEquality;
using ska::detailv3::AssignIfTrue;
using ska::detailv3::HashPolicySelector;
template<typename = void>
struct sherwood_v8_constants
{
static constexpr int8_t magic_for_empty = int8_t(0b11111111);
static constexpr int8_t magic_for_reserved = int8_t(0b11111110);
static constexpr int8_t bits_for_direct_hit = int8_t(0b10000000);
static constexpr int8_t magic_for_direct_hit = int8_t(0b00000000);
static constexpr int8_t magic_for_list_entry = int8_t(0b10000000);
static constexpr int8_t bits_for_distance = int8_t(0b01111111);
inline static int distance_from_metadata(int8_t metadata)
{
return metadata & bits_for_distance;
}
static constexpr int num_jump_distances = 126;
// jump distances chosen like this:
// 1. pick the first 16 integers to promote staying in the same block
// 2. add the next 66 triangular numbers to get even jumps when
// the hash table is a power of two
// 3. add 44 more triangular numbers at a much steeper growth rate
// to get a sequence that allows large jumps so that a table
// with 10000 sequential numbers doesn't endlessly re-allocate
static constexpr size_t jump_distances[num_jump_distances]
{
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231,
253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630,
666, 703, 741, 780, 820, 861, 903, 946, 990, 1035, 1081, 1128, 1176,
1225, 1275, 1326, 1378, 1431, 1485, 1540, 1596, 1653, 1711, 1770, 1830,
1891, 1953, 2016, 2080, 2145, 2211, 2278, 2346, 2415, 2485, 2556,
3741, 8385, 18915, 42486, 95703, 215496, 485605, 1091503, 2456436,
5529475, 12437578, 27986421, 62972253, 141700195, 318819126, 717314626,
1614000520, 3631437253, 8170829695, 18384318876, 41364501751,
93070021080, 209407709220, 471167588430, 1060127437995, 2385287281530,
5366895564381, 12075513791265, 27169907873235, 61132301007778,
137547673121001, 309482258302503, 696335090510256, 1566753939653640,
3525196427195653, 7931691866727775, 17846306747368716,
40154190394120111, 90346928493040500, 203280588949935750,
457381324898247375, 1029107980662394500, 2315492957028380766,
5209859150892887590,
};
};
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::magic_for_empty;
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::magic_for_reserved;
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::bits_for_direct_hit;
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::magic_for_direct_hit;
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::magic_for_list_entry;
template<typename T>
constexpr int8_t sherwood_v8_constants<T>::bits_for_distance;
template<typename T>
constexpr int sherwood_v8_constants<T>::num_jump_distances;
template<typename T>
constexpr size_t sherwood_v8_constants<T>::jump_distances[num_jump_distances];
template<typename T, uint8_t BlockSize>
struct sherwood_v8_block
{
sherwood_v8_block()
{
}
~sherwood_v8_block()
{
}
int8_t control_bytes[BlockSize];
union
{
T data[BlockSize];
};
static sherwood_v8_block * empty_block()
{
static std::array<int8_t, BlockSize> empty_bytes = []
{
std::array<int8_t, BlockSize> result;
result.fill(sherwood_v8_constants<>::magic_for_empty);
return result;
}();
return reinterpret_cast<sherwood_v8_block *>(&empty_bytes);
}
int first_empty_index() const
{
for (int i = 0; i < BlockSize; ++i)
{
if (control_bytes[i] == sherwood_v8_constants<>::magic_for_empty)
return i;
}
return -1;
}
void fill_control_bytes(int8_t value)
{
std::fill(std::begin(control_bytes), std::end(control_bytes), value);
}
};
template<typename T, typename FindKey, typename ArgumentHash, typename Hasher, typename ArgumentEqual, typename Equal, typename ArgumentAlloc, typename ByteAlloc, uint8_t BlockSize>
class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal
{
using AllocatorTraits = std::allocator_traits<ByteAlloc>;
using BlockType = sherwood_v8_block<T, BlockSize>;
using BlockPointer = BlockType *;
using BytePointer = typename AllocatorTraits::pointer;
struct convertible_to_iterator;
using Constants = sherwood_v8_constants<>;
public:
using value_type = T;
using size_type = size_t;
using difference_type = std::ptrdiff_t;
using hasher = ArgumentHash;
using key_equal = ArgumentEqual;
using allocator_type = ByteAlloc;
using reference = value_type &;
using const_reference = const value_type &;
using pointer = value_type *;
using const_pointer = const value_type *;
sherwood_v8_table()
{
}
explicit sherwood_v8_table(size_type bucket_count, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
: ByteAlloc(alloc), Hasher(hash), Equal(equal)
{
if (bucket_count)
rehash(bucket_count);
}
sherwood_v8_table(size_type bucket_count, const ArgumentAlloc & alloc)
: sherwood_v8_table(bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
{
}
sherwood_v8_table(size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
: sherwood_v8_table(bucket_count, hash, ArgumentEqual(), alloc)
{
}
explicit sherwood_v8_table(const ArgumentAlloc & alloc)
: ByteAlloc(alloc)
{
}
template<typename It>
sherwood_v8_table(It first, It last, size_type bucket_count = 0, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
: sherwood_v8_table(bucket_count, hash, equal, alloc)
{
insert(first, last);
}
template<typename It>
sherwood_v8_table(It first, It last, size_type bucket_count, const ArgumentAlloc & alloc)
: sherwood_v8_table(first, last, bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
{
}
template<typename It>
sherwood_v8_table(It first, It last, size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
: sherwood_v8_table(first, last, bucket_count, hash, ArgumentEqual(), alloc)
{
}
sherwood_v8_table(std::initializer_list<T> il, size_type bucket_count = 0, const ArgumentHash & hash = ArgumentHash(), const ArgumentEqual & equal = ArgumentEqual(), const ArgumentAlloc & alloc = ArgumentAlloc())
: sherwood_v8_table(bucket_count, hash, equal, alloc)
{
if (bucket_count == 0)
rehash(il.size());
insert(il.begin(), il.end());
}
sherwood_v8_table(std::initializer_list<T> il, size_type bucket_count, const ArgumentAlloc & alloc)
: sherwood_v8_table(il, bucket_count, ArgumentHash(), ArgumentEqual(), alloc)
{
}
sherwood_v8_table(std::initializer_list<T> il, size_type bucket_count, const ArgumentHash & hash, const ArgumentAlloc & alloc)
: sherwood_v8_table(il, bucket_count, hash, ArgumentEqual(), alloc)
{
}
sherwood_v8_table(const sherwood_v8_table & other)
: sherwood_v8_table(other, AllocatorTraits::select_on_container_copy_construction(other.get_allocator()))
{
}
sherwood_v8_table(const sherwood_v8_table & other, const ArgumentAlloc & alloc)
: ByteAlloc(alloc), Hasher(other), Equal(other), _max_load_factor(other._max_load_factor)
{
rehash_for_other_container(other);
try
{
insert(other.begin(), other.end());
}
catch(...)
{
clear();
deallocate_data(entries, num_slots_minus_one);
throw;
}
}
sherwood_v8_table(sherwood_v8_table && other) noexcept
: ByteAlloc(std::move(other)), Hasher(std::move(other)), Equal(std::move(other))
, _max_load_factor(other._max_load_factor)
{
swap_pointers(other);
}
sherwood_v8_table(sherwood_v8_table && other, const ArgumentAlloc & alloc) noexcept
: ByteAlloc(alloc), Hasher(std::move(other)), Equal(std::move(other))
, _max_load_factor(other._max_load_factor)
{
swap_pointers(other);
}
sherwood_v8_table & operator=(const sherwood_v8_table & other)
{
if (this == std::addressof(other))
return *this;
clear();
if (AllocatorTraits::propagate_on_container_copy_assignment::value)
{
if (static_cast<ByteAlloc &>(*this) != static_cast<const ByteAlloc &>(other))
{
reset_to_empty_state();
}
AssignIfTrue<ByteAlloc, AllocatorTraits::propagate_on_container_copy_assignment::value>()(*this, other);
}
_max_load_factor = other._max_load_factor;
static_cast<Hasher &>(*this) = other;
static_cast<Equal &>(*this) = other;
rehash_for_other_container(other);
insert(other.begin(), other.end());
return *this;
}
sherwood_v8_table & operator=(sherwood_v8_table && other) noexcept
{
if (this == std::addressof(other))
return *this;
else if (AllocatorTraits::propagate_on_container_move_assignment::value)
{
clear();
reset_to_empty_state();
AssignIfTrue<ByteAlloc, AllocatorTraits::propagate_on_container_move_assignment::value>()(*this, std::move(other));
swap_pointers(other);
}
else if (static_cast<ByteAlloc &>(*this) == static_cast<ByteAlloc &>(other))
{
swap_pointers(other);
}
else
{
clear();
_max_load_factor = other._max_load_factor;
rehash_for_other_container(other);
for (T & elem : other)
emplace(std::move(elem));
other.clear();
}
static_cast<Hasher &>(*this) = std::move(other);
static_cast<Equal &>(*this) = std::move(other);
return *this;
}
~sherwood_v8_table()
{
clear();
deallocate_data(entries, num_slots_minus_one);
}
const allocator_type & get_allocator() const
{
return static_cast<const allocator_type &>(*this);
}
const ArgumentEqual & key_eq() const
{
return static_cast<const ArgumentEqual &>(*this);
}
const ArgumentHash & hash_function() const
{
return static_cast<const ArgumentHash &>(*this);
}
template<typename ValueType>
struct templated_iterator
{
private:
friend class sherwood_v8_table;
BlockPointer current = BlockPointer();
size_t index = 0;
public:
templated_iterator()
{
}
templated_iterator(BlockPointer entries, size_t index)
: current(entries)
, index(index)
{
}
using iterator_category = std::forward_iterator_tag;
using value_type = ValueType;
using difference_type = ptrdiff_t;
using pointer = ValueType *;
using reference = ValueType &;
friend bool operator==(const templated_iterator & lhs, const templated_iterator & rhs)
{
return lhs.index == rhs.index;
}
friend bool operator!=(const templated_iterator & lhs, const templated_iterator & rhs)
{
return !(lhs == rhs);
}
templated_iterator & operator++()
{
do
{
if (index % BlockSize == 0)
--current;
if (index-- == 0)
break;
}
while(current->control_bytes[index % BlockSize] == Constants::magic_for_empty);
return *this;
}
templated_iterator operator++(int)
{
templated_iterator copy(*this);
++*this;
return copy;
}
ValueType & operator*() const
{
return current->data[index % BlockSize];
}
ValueType * operator->() const
{
return current->data + index % BlockSize;
}
operator templated_iterator<const value_type>() const
{
return { current, index };
}
};
using iterator = templated_iterator<value_type>;
using const_iterator = templated_iterator<const value_type>;
iterator begin()
{
size_t num_slots = num_slots_minus_one ? num_slots_minus_one + 1 : 0;
return ++iterator{ entries + num_slots / BlockSize, num_slots };
}
const_iterator begin() const
{
size_t num_slots = num_slots_minus_one ? num_slots_minus_one + 1 : 0;
return ++iterator{ entries + num_slots / BlockSize, num_slots };
}
const_iterator cbegin() const
{
return begin();
}
iterator end()
{
return { entries - 1, std::numeric_limits<size_t>::max() };
}
const_iterator end() const
{
return { entries - 1, std::numeric_limits<size_t>::max() };
}
const_iterator cend() const
{
return end();
}
inline iterator find(const FindKey & key)
{
size_t index = hash_object(key);
size_t num_slots_minus_one = this->num_slots_minus_one;
BlockPointer entries = this->entries;
index = hash_policy.index_for_hash(index, num_slots_minus_one);
bool first = true;
for (;;)
{
size_t block_index = index / BlockSize;
int index_in_block = index % BlockSize;
BlockPointer block = entries + block_index;
int8_t metadata = block->control_bytes[index_in_block];
if (first)
{
if ((metadata & Constants::bits_for_direct_hit) != Constants::magic_for_direct_hit)
return end();
first = false;
}
if (compares_equal(key, block->data[index_in_block]))
return { block, index };
int8_t to_next_index = metadata & Constants::bits_for_distance;
if (to_next_index == 0)
return end();
index += Constants::jump_distances[to_next_index];
index = hash_policy.keep_in_range(index, num_slots_minus_one);
}
}
inline const_iterator find(const FindKey & key) const
{
return const_cast<sherwood_v8_table *>(this)->find(key);
}
size_t count(const FindKey & key) const
{
return find(key) == end() ? 0 : 1;
}
std::pair<iterator, iterator> equal_range(const FindKey & key)
{
iterator found = find(key);
if (found == end())
return { found, found };
else
return { found, std::next(found) };
}
std::pair<const_iterator, const_iterator> equal_range(const FindKey & key) const
{
const_iterator found = find(key);
if (found == end())
return { found, found };
else
return { found, std::next(found) };
}
template<typename Key, typename... Args>
inline std::pair<iterator, bool> emplace(Key && key, Args &&... args)
{
size_t index = hash_object(key);
size_t num_slots_minus_one = this->num_slots_minus_one;
BlockPointer entries = this->entries;
index = hash_policy.index_for_hash(index, num_slots_minus_one);
bool first = true;
for (;;)
{
size_t block_index = index / BlockSize;
int index_in_block = index % BlockSize;
BlockPointer block = entries + block_index;
int8_t metadata = block->control_bytes[index_in_block];
if (first)
{
if ((metadata & Constants::bits_for_direct_hit) != Constants::magic_for_direct_hit)
return emplace_direct_hit({ index, block }, std::forward<Key>(key), std::forward<Args>(args)...);
first = false;
}
if (compares_equal(key, block->data[index_in_block]))
return { { block, index }, false };
int8_t to_next_index = metadata & Constants::bits_for_distance;
if (to_next_index == 0)
return emplace_new_key({ index, block }, std::forward<Key>(key), std::forward<Args>(args)...);
index += Constants::jump_distances[to_next_index];
index = hash_policy.keep_in_range(index, num_slots_minus_one);
}
}
std::pair<iterator, bool> insert(const value_type & value)
{
return emplace(value);
}
std::pair<iterator, bool> insert(value_type && value)
{
return emplace(std::move(value));
}
template<typename... Args>
iterator emplace_hint(const_iterator, Args &&... args)
{
return emplace(std::forward<Args>(args)...).first;
}
iterator insert(const_iterator, const value_type & value)
{
return emplace(value).first;
}
iterator insert(const_iterator, value_type && value)
{
return emplace(std::move(value)).first;
}
template<typename It>
void insert(It begin, It end)
{
for (; begin != end; ++begin)
{
emplace(*begin);
}
}
void insert(std::initializer_list<value_type> il)
{
insert(il.begin(), il.end());
}
void rehash(size_t num_items)
{
num_items = std::max(num_items, static_cast<size_t>(std::ceil(num_elements / static_cast<double>(_max_load_factor))));
if (num_items == 0)
{
reset_to_empty_state();
return;
}
auto new_prime_index = hash_policy.next_size_over(num_items);
if (num_items == num_slots_minus_one + 1)
return;
size_t num_blocks = num_items / BlockSize;
if (num_items % BlockSize)
++num_blocks;
size_t memory_requirement = calculate_memory_requirement(num_blocks);
unsigned char * new_memory = &*AllocatorTraits::allocate(*this, memory_requirement);
BlockPointer new_buckets = reinterpret_cast<BlockPointer>(new_memory);
BlockPointer special_end_item = new_buckets + num_blocks;
for (BlockPointer it = new_buckets; it <= special_end_item; ++it)
it->fill_control_bytes(Constants::magic_for_empty);
using std::swap;
swap(entries, new_buckets);
swap(num_slots_minus_one, num_items);
--num_slots_minus_one;
hash_policy.commit(new_prime_index);
num_elements = 0;
if (num_items)
++num_items;
size_t old_num_blocks = num_items / BlockSize;
if (num_items % BlockSize)
++old_num_blocks;
for (BlockPointer it = new_buckets, end = new_buckets + old_num_blocks; it != end; ++it)
{
for (int i = 0; i < BlockSize; ++i)
{
int8_t metadata = it->control_bytes[i];
if (metadata != Constants::magic_for_empty && metadata != Constants::magic_for_reserved)
{
emplace(std::move(it->data[i]));
AllocatorTraits::destroy(*this, it->data + i);
}
}
}
deallocate_data(new_buckets, num_items - 1);
}
void reserve(size_t num_elements)
{
size_t required_buckets = num_buckets_for_reserve(num_elements);
if (required_buckets > bucket_count())
rehash(required_buckets);
}
// the return value is a type that can be converted to an iterator
// the reason for doing this is that it's not free to find the
// iterator pointing at the next element. if you care about the
// next iterator, turn the return value into an iterator
convertible_to_iterator erase(const_iterator to_erase)
{
LinkedListIt current = { to_erase.index, to_erase.current };
if (current.has_next())
{
LinkedListIt previous = current;
LinkedListIt next = current.next(*this);
while (next.has_next())
{
previous = next;
next = next.next(*this);
}
AllocatorTraits::destroy(*this, std::addressof(*current));
AllocatorTraits::construct(*this, std::addressof(*current), std::move(*next));
AllocatorTraits::destroy(*this, std::addressof(*next));
next.set_metadata(Constants::magic_for_empty);
previous.clear_next();
}
else
{
if (!current.is_direct_hit())
find_parent_block(current).clear_next();
AllocatorTraits::destroy(*this, std::addressof(*current));
current.set_metadata(Constants::magic_for_empty);
}
--num_elements;
return { to_erase.current, to_erase.index };
}
iterator erase(const_iterator begin_it, const_iterator end_it)
{
if (begin_it == end_it)
return { begin_it.current, begin_it.index };
if (std::next(begin_it) == end_it)
return erase(begin_it);
if (begin_it == begin() && end_it == end())
{
clear();
return { end_it.current, end_it.index };
}
std::vector<std::pair<int, LinkedListIt>> depth_in_chain;
for (const_iterator it = begin_it; it != end_it; ++it)
{
LinkedListIt list_it(it.index, it.current);
if (list_it.is_direct_hit())
depth_in_chain.emplace_back(0, list_it);
else
{
LinkedListIt root = find_direct_hit(list_it);
int distance = 1;
for (;;)
{
LinkedListIt next = root.next(*this);
if (next == list_it)
break;
++distance;
root = next;
}
depth_in_chain.emplace_back(distance, list_it);
}
}
std::sort(depth_in_chain.begin(), depth_in_chain.end(), [](const auto & a, const auto & b) { return a.first < b.first; });
for (auto it = depth_in_chain.rbegin(), end = depth_in_chain.rend(); it != end; ++it)
{
erase(it->second.it());
}
if (begin_it.current->control_bytes[begin_it.index % BlockSize] == Constants::magic_for_empty)
return ++iterator{ begin_it.current, begin_it.index };
else
return { begin_it.current, begin_it.index };
}
size_t erase(const FindKey & key)
{
auto found = find(key);
if (found == end())
return 0;
else
{
erase(found);
return 1;
}
}
void clear()
{
if (!num_slots_minus_one)
return;
size_t num_slots = num_slots_minus_one + 1;
size_t num_blocks = num_slots / BlockSize;
if (num_slots % BlockSize)
++num_blocks;
for (BlockPointer it = entries, end = it + num_blocks; it != end; ++it)
{
for (int i = 0; i < BlockSize; ++i)
{
if (it->control_bytes[i] != Constants::magic_for_empty)
{
AllocatorTraits::destroy(*this, std::addressof(it->data[i]));
it->control_bytes[i] = Constants::magic_for_empty;
}
}
}
num_elements = 0;
}
void shrink_to_fit()
{
rehash_for_other_container(*this);
}
void swap(sherwood_v8_table & other)
{
using std::swap;
swap_pointers(other);
swap(static_cast<ArgumentHash &>(*this), static_cast<ArgumentHash &>(other));
swap(static_cast<ArgumentEqual &>(*this), static_cast<ArgumentEqual &>(other));
if (AllocatorTraits::propagate_on_container_swap::value)
swap(static_cast<ByteAlloc &>(*this), static_cast<ByteAlloc &>(other));
}
size_t size() const
{
return num_elements;
}
size_t max_size() const
{
return (AllocatorTraits::max_size(*this)) / sizeof(T);
}
size_t bucket_count() const
{
return num_slots_minus_one ? num_slots_minus_one + 1 : 0;
}
size_type max_bucket_count() const
{
return (AllocatorTraits::max_size(*this)) / sizeof(T);
}
size_t bucket(const FindKey & key) const
{
return hash_policy.index_for_hash(hash_object(key), num_slots_minus_one);
}
float load_factor() const
{
return static_cast<double>(num_elements) / (num_slots_minus_one + 1);
}
void max_load_factor(float value)
{
_max_load_factor = value;
}
float max_load_factor() const
{
return _max_load_factor;
}
bool empty() const
{
return num_elements == 0;
}
private:
BlockPointer entries = BlockType::empty_block();
size_t num_slots_minus_one = 0;
typename HashPolicySelector<ArgumentHash>::type hash_policy;
float _max_load_factor = 0.9375f;
size_t num_elements = 0;
size_t num_buckets_for_reserve(size_t num_elements) const
{
return static_cast<size_t>(std::ceil(num_elements / static_cast<double>(_max_load_factor)));
}
void rehash_for_other_container(const sherwood_v8_table & other)
{
rehash(std::min(num_buckets_for_reserve(other.size()), other.bucket_count()));
}
bool is_full() const
{
if (!num_slots_minus_one)
return true;
else
return num_elements + 1 > (num_slots_minus_one + 1) * static_cast<double>(_max_load_factor);
}
void swap_pointers(sherwood_v8_table & other)
{
using std::swap;
swap(hash_policy, other.hash_policy);
swap(entries, other.entries);
swap(num_slots_minus_one, other.num_slots_minus_one);
swap(num_elements, other.num_elements);
swap(_max_load_factor, other._max_load_factor);
}
struct LinkedListIt
{
size_t index = 0;
BlockPointer block = nullptr;
LinkedListIt()
{
}
LinkedListIt(size_t index, BlockPointer block)
: index(index), block(block)
{
}
iterator it() const
{
return { block, index };
}
int index_in_block() const
{
return index % BlockSize;
}
bool is_direct_hit() const
{
return (metadata() & Constants::bits_for_direct_hit) == Constants::magic_for_direct_hit;
}
bool is_empty() const
{
return metadata() == Constants::magic_for_empty;
}
bool has_next() const
{
return jump_index() != 0;
}
int8_t jump_index() const
{
return Constants::distance_from_metadata(metadata());
}
int8_t metadata() const
{
return block->control_bytes[index_in_block()];
}
void set_metadata(int8_t metadata)
{
block->control_bytes[index_in_block()] = metadata;
}
LinkedListIt next(sherwood_v8_table & table) const
{
int8_t distance = jump_index();
size_t next_index = table.hash_policy.keep_in_range(index + Constants::jump_distances[distance], table.num_slots_minus_one);
return { next_index, table.entries + next_index / BlockSize };
}
void set_next(int8_t jump_index)
{
int8_t & metadata = block->control_bytes[index_in_block()];
metadata = (metadata & ~Constants::bits_for_distance) | jump_index;
}
void clear_next()
{
set_next(0);
}
value_type & operator*() const
{
return block->data[index_in_block()];
}
bool operator!() const
{
return !block;
}
explicit operator bool() const
{
return block != nullptr;
}
bool operator==(const LinkedListIt & other) const
{
return index == other.index;
}
bool operator!=(const LinkedListIt & other) const
{
return !(*this == other);
}
};
template<typename... Args>
SKA_NOINLINE(std::pair<iterator, bool>) emplace_direct_hit(LinkedListIt block, Args &&... args)
{
using std::swap;
if (is_full())
{
grow();
return emplace(std::forward<Args>(args)...);
}
if (block.metadata() == Constants::magic_for_empty)
{
AllocatorTraits::construct(*this, std::addressof(*block), std::forward<Args>(args)...);
block.set_metadata(Constants::magic_for_direct_hit);
++num_elements;
return { block.it(), true };
}
else
{
LinkedListIt parent_block = find_parent_block(block);
std::pair<int8_t, LinkedListIt> free_block = find_free_index(parent_block);
if (!free_block.first)
{
grow();
return emplace(std::forward<Args>(args)...);
}
value_type new_value(std::forward<Args>(args)...);
for (LinkedListIt it = block;;)
{
AllocatorTraits::construct(*this, std::addressof(*free_block.second), std::move(*it));
AllocatorTraits::destroy(*this, std::addressof(*it));
parent_block.set_next(free_block.first);
free_block.second.set_metadata(Constants::magic_for_list_entry);
if (!it.has_next())
{
it.set_metadata(Constants::magic_for_empty);
break;
}
LinkedListIt next = it.next(*this);
it.set_metadata(Constants::magic_for_empty);
block.set_metadata(Constants::magic_for_reserved);
it = next;
parent_block = free_block.second;
free_block = find_free_index(free_block.second);
if (!free_block.first)
{
grow();
return emplace(std::move(new_value));
}
}
AllocatorTraits::construct(*this, std::addressof(*block), std::move(new_value));
block.set_metadata(Constants::magic_for_direct_hit);
++num_elements;
return { block.it(), true };
}
}
template<typename... Args>
SKA_NOINLINE(std::pair<iterator, bool>) emplace_new_key(LinkedListIt parent, Args &&... args)
{
if (is_full())
{
grow();
return emplace(std::forward<Args>(args)...);
}
std::pair<int8_t, LinkedListIt> free_block = find_free_index(parent);
if (!free_block.first)
{
grow();
return emplace(std::forward<Args>(args)...);
}
AllocatorTraits::construct(*this, std::addressof(*free_block.second), std::forward<Args>(args)...);
free_block.second.set_metadata(Constants::magic_for_list_entry);
parent.set_next(free_block.first);
++num_elements;
return { free_block.second.it(), true };
}
LinkedListIt find_direct_hit(LinkedListIt child) const
{
size_t to_move_hash = hash_object(*child);
size_t to_move_index = hash_policy.index_for_hash(to_move_hash, num_slots_minus_one);
return { to_move_index, entries + to_move_index / BlockSize };
}
LinkedListIt find_parent_block(LinkedListIt child)
{
LinkedListIt parent_block = find_direct_hit(child);
for (;;)
{
LinkedListIt next = parent_block.next(*this);
if (next == child)
return parent_block;
parent_block = next;
}
}
std::pair<int8_t, LinkedListIt> find_free_index(LinkedListIt parent) const
{
for (int8_t jump_index = 1; jump_index < Constants::num_jump_distances; ++jump_index)
{
size_t index = hash_policy.keep_in_range(parent.index + Constants::jump_distances[jump_index], num_slots_minus_one);
BlockPointer block = entries + index / BlockSize;
if (block->control_bytes[index % BlockSize] == Constants::magic_for_empty)
return { jump_index, { index, block } };
}
return { 0, {} };
}
void grow()
{
rehash(std::max(size_t(10), 2 * bucket_count()));
}
size_t calculate_memory_requirement(size_t num_blocks)
{
size_t memory_required = sizeof(BlockType) * num_blocks;
memory_required += BlockSize; // for metadata of past-the-end pointer
return memory_required;
}
void deallocate_data(BlockPointer begin, size_t num_slots_minus_one)
{
if (begin == BlockType::empty_block())
return;
++num_slots_minus_one;
size_t num_blocks = num_slots_minus_one / BlockSize;
if (num_slots_minus_one % BlockSize)
++num_blocks;
size_t memory = calculate_memory_requirement(num_blocks);
unsigned char * as_byte_pointer = reinterpret_cast<unsigned char *>(begin);
AllocatorTraits::deallocate(*this, typename AllocatorTraits::pointer(as_byte_pointer), memory);
}
void reset_to_empty_state()
{
deallocate_data(entries, num_slots_minus_one);
entries = BlockType::empty_block();
num_slots_minus_one = 0;
hash_policy.reset();
}