ladybird/AK/HashTable.h
Ben Wiederhake f8d7b4daea AK: Add missing headers
Example failure:

IDAllocator.h only pulls in AK/Hashtable.h, so any compilation unit that
includes AK/IDAllocator.h without including AK/Traits.h before it used
to be doomed to fail with the cryptic error message "In instantiation of
'AK::HashTable<T, TraitsForT, IsOrdered>::Iterator AK::HashTable<T,
TraitsForT, IsOrdered>::find(const T&) [with T = int; TraitsForT =
AK::Traits: incomplete type 'AK::Traits<int>' used in nested name
specifier".
2021-10-06 23:52:40 +01:00

500 lines
14 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Forward.h>
#include <AK/HashFunctions.h>
#include <AK/StdLibExtras.h>
#include <AK/Traits.h>
#include <AK/Types.h>
#include <AK/kmalloc.h>
namespace AK {
enum class HashSetResult {
Failed = 0,
InsertedNewEntry,
ReplacedExistingEntry,
KeptExistingEntry
};
enum class HashSetExistingEntryBehavior {
Keep,
Replace
};
template<typename HashTableType, typename T, typename BucketType>
class HashTableIterator {
friend HashTableType;
public:
bool operator==(const HashTableIterator& other) const { return m_bucket == other.m_bucket; }
bool operator!=(const HashTableIterator& other) const { return m_bucket != other.m_bucket; }
T& operator*() { return *m_bucket->slot(); }
T* operator->() { return m_bucket->slot(); }
void operator++() { skip_to_next(); }
private:
void skip_to_next()
{
if (!m_bucket)
return;
do {
++m_bucket;
if (m_bucket->used)
return;
} while (!m_bucket->end);
if (m_bucket->end)
m_bucket = nullptr;
}
explicit HashTableIterator(BucketType* bucket)
: m_bucket(bucket)
{
}
BucketType* m_bucket { nullptr };
};
template<typename OrderedHashTableType, typename T, typename BucketType>
class OrderedHashTableIterator {
friend OrderedHashTableType;
public:
bool operator==(const OrderedHashTableIterator& other) const { return m_bucket == other.m_bucket; }
bool operator!=(const OrderedHashTableIterator& other) const { return m_bucket != other.m_bucket; }
T& operator*() { return *m_bucket->slot(); }
T* operator->() { return m_bucket->slot(); }
void operator++() { m_bucket = m_bucket->next; }
void operator--() { m_bucket = m_bucket->previous; }
private:
explicit OrderedHashTableIterator(BucketType* bucket)
: m_bucket(bucket)
{
}
BucketType* m_bucket { nullptr };
};
template<typename T, typename TraitsForT, bool IsOrdered>
class HashTable {
static constexpr size_t load_factor_in_percent = 60;
struct Bucket {
bool used;
bool deleted;
bool end;
alignas(T) u8 storage[sizeof(T)];
T* slot() { return reinterpret_cast<T*>(storage); }
const T* slot() const { return reinterpret_cast<const T*>(storage); }
};
struct OrderedBucket {
OrderedBucket* previous;
OrderedBucket* next;
bool used;
bool deleted;
alignas(T) u8 storage[sizeof(T)];
T* slot() { return reinterpret_cast<T*>(storage); }
const T* slot() const { return reinterpret_cast<const T*>(storage); }
};
using BucketType = Conditional<IsOrdered, OrderedBucket, Bucket>;
struct CollectionData {
};
struct OrderedCollectionData {
BucketType* head { nullptr };
BucketType* tail { nullptr };
};
using CollectionDataType = Conditional<IsOrdered, OrderedCollectionData, CollectionData>;
public:
HashTable() = default;
explicit HashTable(size_t capacity) { rehash(capacity); }
~HashTable()
{
if (!m_buckets)
return;
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
m_buckets[i].slot()->~T();
}
kfree_sized(m_buckets, size_in_bytes(m_capacity));
}
HashTable(const HashTable& other)
{
rehash(other.capacity());
for (auto& it : other)
set(it);
}
HashTable& operator=(const HashTable& other)
{
HashTable temporary(other);
swap(*this, temporary);
return *this;
}
HashTable(HashTable&& other) noexcept
: m_buckets(other.m_buckets)
, m_collection_data(other.m_collection_data)
, m_size(other.m_size)
, m_capacity(other.m_capacity)
, m_deleted_count(other.m_deleted_count)
{
other.m_size = 0;
other.m_capacity = 0;
other.m_deleted_count = 0;
other.m_buckets = nullptr;
if constexpr (IsOrdered)
other.m_collection_data = { nullptr, nullptr };
}
HashTable& operator=(HashTable&& other) noexcept
{
HashTable temporary { move(other) };
swap(*this, temporary);
return *this;
}
friend void swap(HashTable& a, HashTable& b) noexcept
{
swap(a.m_buckets, b.m_buckets);
swap(a.m_size, b.m_size);
swap(a.m_capacity, b.m_capacity);
swap(a.m_deleted_count, b.m_deleted_count);
if constexpr (IsOrdered)
swap(a.m_collection_data, b.m_collection_data);
}
[[nodiscard]] bool is_empty() const { return !m_size; }
[[nodiscard]] size_t size() const { return m_size; }
[[nodiscard]] size_t capacity() const { return m_capacity; }
template<typename U, size_t N>
bool try_set_from(U (&from_array)[N])
{
for (size_t i = 0; i < N; ++i) {
if (try_set(from_array[i]) == HashSetResult::Failed)
return false;
}
return true;
}
template<typename U, size_t N>
void set_from(U (&from_array)[N])
{
bool result = try_set_from(from_array);
VERIFY(result);
}
void ensure_capacity(size_t capacity)
{
VERIFY(capacity >= size());
rehash(capacity * 2);
}
[[nodiscard]] bool contains(T const& value) const
{
return find(value) != end();
}
using Iterator = Conditional<IsOrdered,
OrderedHashTableIterator<HashTable, T, BucketType>,
HashTableIterator<HashTable, T, BucketType>>;
[[nodiscard]] Iterator begin()
{
if constexpr (IsOrdered)
return Iterator(m_collection_data.head);
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
return Iterator(&m_buckets[i]);
}
return end();
}
[[nodiscard]] Iterator end()
{
return Iterator(nullptr);
}
using ConstIterator = Conditional<IsOrdered,
OrderedHashTableIterator<const HashTable, const T, const BucketType>,
HashTableIterator<const HashTable, const T, const BucketType>>;
[[nodiscard]] ConstIterator begin() const
{
if constexpr (IsOrdered)
return ConstIterator(m_collection_data.head);
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
return ConstIterator(&m_buckets[i]);
}
return end();
}
[[nodiscard]] ConstIterator end() const
{
return ConstIterator(nullptr);
}
void clear()
{
*this = HashTable();
}
template<typename U = T>
HashSetResult try_set(U&& value, HashSetExistingEntryBehavior existing_entry_behavior = HashSetExistingEntryBehavior::Replace)
{
auto* bucket = try_lookup_for_writing(value);
if (!bucket)
return HashSetResult::Failed;
if (bucket->used) {
if (existing_entry_behavior == HashSetExistingEntryBehavior::Keep)
return HashSetResult::KeptExistingEntry;
(*bucket->slot()) = forward<U>(value);
return HashSetResult::ReplacedExistingEntry;
}
new (bucket->slot()) T(forward<U>(value));
bucket->used = true;
if (bucket->deleted) {
bucket->deleted = false;
--m_deleted_count;
}
if constexpr (IsOrdered) {
if (!m_collection_data.head) [[unlikely]] {
m_collection_data.head = bucket;
} else {
bucket->previous = m_collection_data.tail;
m_collection_data.tail->next = bucket;
}
m_collection_data.tail = bucket;
}
++m_size;
return HashSetResult::InsertedNewEntry;
}
template<typename U = T>
HashSetResult set(U&& value, HashSetExistingEntryBehavior existing_entry_behaviour = HashSetExistingEntryBehavior::Replace)
{
auto result = try_set(forward<U>(value), existing_entry_behaviour);
VERIFY(result != HashSetResult::Failed);
return result;
}
template<typename TUnaryPredicate>
[[nodiscard]] Iterator find(unsigned hash, TUnaryPredicate predicate)
{
return Iterator(lookup_with_hash(hash, move(predicate)));
}
[[nodiscard]] Iterator find(T const& value)
{
return find(TraitsForT::hash(value), [&](auto& other) { return TraitsForT::equals(value, other); });
}
template<typename TUnaryPredicate>
[[nodiscard]] ConstIterator find(unsigned hash, TUnaryPredicate predicate) const
{
return ConstIterator(lookup_with_hash(hash, move(predicate)));
}
[[nodiscard]] ConstIterator find(T const& value) const
{
return find(TraitsForT::hash(value), [&](auto& other) { return TraitsForT::equals(value, other); });
}
bool remove(const T& value)
{
auto it = find(value);
if (it != end()) {
remove(it);
return true;
}
return false;
}
void remove(Iterator iterator)
{
VERIFY(iterator.m_bucket);
auto& bucket = *iterator.m_bucket;
VERIFY(bucket.used);
VERIFY(!bucket.deleted);
if constexpr (!IsOrdered)
VERIFY(!bucket.end);
bucket.slot()->~T();
bucket.used = false;
bucket.deleted = true;
--m_size;
++m_deleted_count;
if constexpr (IsOrdered) {
if (bucket.previous)
bucket.previous->next = bucket.next;
else
m_collection_data.head = bucket.next;
if (bucket.next)
bucket.next->previous = bucket.previous;
else
m_collection_data.tail = bucket.previous;
}
}
private:
void insert_during_rehash(T&& value)
{
auto& bucket = lookup_for_writing(value);
new (bucket.slot()) T(move(value));
bucket.used = true;
if constexpr (IsOrdered) {
if (!m_collection_data.head) [[unlikely]] {
m_collection_data.head = &bucket;
} else {
bucket.previous = m_collection_data.tail;
m_collection_data.tail->next = &bucket;
}
m_collection_data.tail = &bucket;
}
}
[[nodiscard]] static constexpr size_t size_in_bytes(size_t capacity)
{
if constexpr (IsOrdered) {
return sizeof(BucketType) * capacity;
} else {
return sizeof(BucketType) * (capacity + 1);
}
}
bool try_rehash(size_t new_capacity)
{
new_capacity = max(new_capacity, static_cast<size_t>(4));
new_capacity = kmalloc_good_size(new_capacity * sizeof(BucketType)) / sizeof(BucketType);
auto* old_buckets = m_buckets;
auto old_capacity = m_capacity;
Iterator old_iter = begin();
auto new_buckets = kmalloc(size_in_bytes(new_capacity));
if (!new_buckets)
return false;
m_buckets = (BucketType*)new_buckets;
__builtin_memset(m_buckets, 0, size_in_bytes(new_capacity));
m_capacity = new_capacity;
m_deleted_count = 0;
if constexpr (IsOrdered)
m_collection_data = { nullptr, nullptr };
else
m_buckets[m_capacity].end = true;
if (!old_buckets)
return true;
for (auto it = move(old_iter); it != end(); ++it) {
insert_during_rehash(move(*it));
it->~T();
}
kfree_sized(old_buckets, size_in_bytes(old_capacity));
return true;
}
void rehash(size_t new_capacity)
{
bool result = try_rehash(new_capacity);
VERIFY(result);
}
template<typename TUnaryPredicate>
[[nodiscard]] BucketType* lookup_with_hash(unsigned hash, TUnaryPredicate predicate) const
{
if (is_empty())
return nullptr;
for (;;) {
auto& bucket = m_buckets[hash % m_capacity];
if (bucket.used && predicate(*bucket.slot()))
return &bucket;
if (!bucket.used && !bucket.deleted)
return nullptr;
hash = double_hash(hash);
}
}
[[nodiscard]] BucketType* try_lookup_for_writing(T const& value)
{
// FIXME: Maybe overrun the "allowed" load factor to avoid OOM
// If we are allowed to do that, separate that logic from
// the normal lookup_for_writing
if (should_grow()) {
if (!try_rehash(capacity() * 2))
return nullptr;
}
auto hash = TraitsForT::hash(value);
BucketType* first_empty_bucket = nullptr;
for (;;) {
auto& bucket = m_buckets[hash % m_capacity];
if (bucket.used && TraitsForT::equals(*bucket.slot(), value))
return &bucket;
if (!bucket.used) {
if (!first_empty_bucket)
first_empty_bucket = &bucket;
if (!bucket.deleted)
return const_cast<BucketType*>(first_empty_bucket);
}
hash = double_hash(hash);
}
}
[[nodiscard]] BucketType& lookup_for_writing(T const& value)
{
auto* item = try_lookup_for_writing(value);
VERIFY(item);
return *item;
}
[[nodiscard]] size_t used_bucket_count() const { return m_size + m_deleted_count; }
[[nodiscard]] bool should_grow() const { return ((used_bucket_count() + 1) * 100) >= (m_capacity * load_factor_in_percent); }
BucketType* m_buckets { nullptr };
[[no_unique_address]] CollectionDataType m_collection_data;
size_t m_size { 0 };
size_t m_capacity { 0 };
size_t m_deleted_count { 0 };
};
}
using AK::HashTable;
using AK::OrderedHashTable;