ladybird/AK/HashTable.h
Lenny Maiorani e6f907a155 AK: Simplify constructors and conversions from nullptr_t
Problem:
- Many constructors are defined as `{}` rather than using the ` =
  default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
  instead of requiring the caller to default construct. This violates
  the C++ Core Guidelines suggestion to declare single-argument
  constructors explicit
  (https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).

Solution:
- Change default constructors to use the compiler-provided default
  constructor.
- Remove implicit conversion operators from `nullptr_t` and change
  usage to enforce type consistency without conversion.
2021-01-12 09:11:45 +01:00

379 lines
10 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/HashFunctions.h>
#include <AK/LogStream.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
#include <AK/kmalloc.h>
namespace AK {
enum class HashSetResult {
InsertedNewEntry,
ReplacedExistingEntry
};
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 T, typename TraitsForT>
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); }
};
public:
HashTable() = default;
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(m_buckets);
}
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_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;
}
HashTable& operator=(HashTable&& other) noexcept
{
swap(*this, other);
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);
}
bool is_empty() const { return !m_size; }
size_t size() const { return m_size; }
size_t capacity() const { return m_capacity; }
template<typename U, size_t N>
void set_from(U (&from_array)[N])
{
for (size_t i = 0; i < N; ++i) {
set(from_array[i]);
}
}
void ensure_capacity(size_t capacity)
{
ASSERT(capacity >= size());
rehash(capacity * 2);
}
bool contains(const T& value) const
{
return find(value) != end();
}
using Iterator = HashTableIterator<HashTable, T, Bucket>;
Iterator begin()
{
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
return Iterator(&m_buckets[i]);
}
return end();
}
Iterator end()
{
return Iterator(nullptr);
}
using ConstIterator = HashTableIterator<const HashTable, const T, const Bucket>;
ConstIterator begin() const
{
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
return ConstIterator(&m_buckets[i]);
}
return end();
}
ConstIterator end() const
{
return ConstIterator(nullptr);
}
void clear()
{
*this = HashTable();
}
HashSetResult set(T&& value)
{
auto& bucket = lookup_for_writing(value);
if (bucket.used) {
(*bucket.slot()) = move(value);
return HashSetResult::ReplacedExistingEntry;
}
new (bucket.slot()) T(move(value));
bucket.used = true;
if (bucket.deleted) {
bucket.deleted = false;
--m_deleted_count;
}
++m_size;
return HashSetResult::InsertedNewEntry;
}
HashSetResult set(const T& value)
{
return set(T(value));
}
template<typename Finder>
Iterator find(unsigned hash, Finder finder)
{
return Iterator(lookup_with_hash(hash, move(finder)));
}
Iterator find(const T& value)
{
return find(TraitsForT::hash(value), [&](auto& other) { return TraitsForT::equals(value, other); });
}
template<typename Finder>
ConstIterator find(unsigned hash, Finder finder) const
{
return ConstIterator(lookup_with_hash(hash, move(finder)));
}
ConstIterator find(const T& 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)
{
ASSERT(iterator.m_bucket);
auto& bucket = *iterator.m_bucket;
ASSERT(bucket.used);
ASSERT(!bucket.end);
ASSERT(!bucket.deleted);
bucket.slot()->~T();
bucket.used = false;
bucket.deleted = true;
--m_size;
++m_deleted_count;
}
private:
void insert_during_rehash(T&& value)
{
auto& bucket = lookup_for_writing(value);
new (bucket.slot()) T(move(value));
bucket.used = true;
}
void rehash(size_t new_capacity)
{
new_capacity = max(new_capacity, static_cast<size_t>(4));
auto* old_buckets = m_buckets;
auto old_capacity = m_capacity;
m_buckets = (Bucket*)kmalloc(sizeof(Bucket) * (new_capacity + 1));
__builtin_memset(m_buckets, 0, sizeof(Bucket) * (new_capacity + 1));
m_capacity = new_capacity;
m_deleted_count = 0;
m_buckets[m_capacity].end = true;
if (!old_buckets)
return;
for (size_t i = 0; i < old_capacity; ++i) {
auto& old_bucket = old_buckets[i];
if (old_bucket.used) {
insert_during_rehash(move(*old_bucket.slot()));
old_bucket.slot()->~T();
}
}
kfree(old_buckets);
}
template<typename Finder>
Bucket* lookup_with_hash(unsigned hash, Finder finder, Bucket** usable_bucket_for_writing = nullptr) const
{
if (is_empty())
return nullptr;
size_t bucket_index = hash % m_capacity;
for (;;) {
auto& bucket = m_buckets[bucket_index];
if (usable_bucket_for_writing && !*usable_bucket_for_writing && !bucket.used) {
*usable_bucket_for_writing = &bucket;
}
if (bucket.used && finder(*bucket.slot()))
return &bucket;
if (!bucket.used && !bucket.deleted)
return nullptr;
hash = double_hash(hash);
bucket_index = hash % m_capacity;
}
}
const Bucket* lookup_for_reading(const T& value) const
{
return lookup_with_hash(TraitsForT::hash(value), [&value](auto& entry) { return TraitsForT::equals(entry, value); });
}
Bucket& lookup_for_writing(const T& value)
{
auto hash = TraitsForT::hash(value);
Bucket* usable_bucket_for_writing = nullptr;
if (auto* bucket_for_reading = lookup_with_hash(
hash,
[&value](auto& entry) { return TraitsForT::equals(entry, value); },
&usable_bucket_for_writing)) {
return *const_cast<Bucket*>(bucket_for_reading);
}
if (should_grow())
rehash(capacity() * 2);
else if (usable_bucket_for_writing)
return *usable_bucket_for_writing;
size_t bucket_index = hash % m_capacity;
for (;;) {
auto& bucket = m_buckets[bucket_index];
if (!bucket.used)
return bucket;
hash = double_hash(hash);
bucket_index = hash % m_capacity;
}
}
size_t used_bucket_count() const { return m_size + m_deleted_count; }
bool should_grow() const { return ((used_bucket_count() + 1) * 100) >= (m_capacity * load_factor_in_percent); }
Bucket* m_buckets { nullptr };
size_t m_size { 0 };
size_t m_capacity { 0 };
size_t m_deleted_count { 0 };
};
}
using AK::HashTable;