mirror of
https://github.com/SerenityOS/serenity
synced 2024-07-22 10:36:24 +00:00
623bdd8b6a
Just walk the table from start to finish, deleting buckets as we go. This removes the need for remove() to return an iterator, which is preventing me from implementing hash table auto-shrinking.
581 lines
16 KiB
C++
581 lines
16 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Concepts.h>
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#include <AK/Error.h>
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#include <AK/Forward.h>
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#include <AK/HashFunctions.h>
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#include <AK/StdLibExtras.h>
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#include <AK/Traits.h>
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#include <AK/Types.h>
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#include <AK/kmalloc.h>
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namespace AK {
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enum class HashSetResult {
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InsertedNewEntry,
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ReplacedExistingEntry,
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KeptExistingEntry
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};
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enum class HashSetExistingEntryBehavior {
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Keep,
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Replace
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};
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template<typename HashTableType, typename T, typename BucketType>
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class HashTableIterator {
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friend HashTableType;
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public:
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bool operator==(const HashTableIterator& other) const { return m_bucket == other.m_bucket; }
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bool operator!=(const HashTableIterator& other) const { return m_bucket != other.m_bucket; }
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T& operator*() { return *m_bucket->slot(); }
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T* operator->() { return m_bucket->slot(); }
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void operator++() { skip_to_next(); }
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private:
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void skip_to_next()
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{
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if (!m_bucket)
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return;
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do {
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++m_bucket;
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if (m_bucket->used)
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return;
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} while (!m_bucket->end);
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if (m_bucket->end)
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m_bucket = nullptr;
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}
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explicit HashTableIterator(BucketType* bucket)
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: m_bucket(bucket)
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{
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}
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BucketType* m_bucket { nullptr };
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};
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template<typename OrderedHashTableType, typename T, typename BucketType>
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class OrderedHashTableIterator {
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friend OrderedHashTableType;
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public:
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bool operator==(const OrderedHashTableIterator& other) const { return m_bucket == other.m_bucket; }
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bool operator!=(const OrderedHashTableIterator& other) const { return m_bucket != other.m_bucket; }
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T& operator*() { return *m_bucket->slot(); }
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T* operator->() { return m_bucket->slot(); }
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void operator++() { m_bucket = m_bucket->next; }
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void operator--() { m_bucket = m_bucket->previous; }
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private:
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explicit OrderedHashTableIterator(BucketType* bucket)
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: m_bucket(bucket)
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{
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}
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BucketType* m_bucket { nullptr };
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};
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template<typename T, typename TraitsForT, bool IsOrdered>
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class HashTable {
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static constexpr size_t load_factor_in_percent = 60;
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struct Bucket {
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bool used;
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bool deleted;
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bool end;
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alignas(T) u8 storage[sizeof(T)];
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T* slot() { return reinterpret_cast<T*>(storage); }
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const T* slot() const { return reinterpret_cast<const T*>(storage); }
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};
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struct OrderedBucket {
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OrderedBucket* previous;
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OrderedBucket* next;
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bool used;
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bool deleted;
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alignas(T) u8 storage[sizeof(T)];
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T* slot() { return reinterpret_cast<T*>(storage); }
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const T* slot() const { return reinterpret_cast<const T*>(storage); }
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};
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using BucketType = Conditional<IsOrdered, OrderedBucket, Bucket>;
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struct CollectionData {
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};
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struct OrderedCollectionData {
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BucketType* head { nullptr };
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BucketType* tail { nullptr };
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};
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using CollectionDataType = Conditional<IsOrdered, OrderedCollectionData, CollectionData>;
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public:
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HashTable() = default;
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explicit HashTable(size_t capacity) { rehash(capacity); }
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~HashTable()
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{
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if (!m_buckets)
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return;
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for (size_t i = 0; i < m_capacity; ++i) {
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if (m_buckets[i].used)
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m_buckets[i].slot()->~T();
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}
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kfree_sized(m_buckets, size_in_bytes(m_capacity));
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}
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HashTable(const HashTable& other)
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{
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rehash(other.capacity());
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for (auto& it : other)
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set(it);
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}
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HashTable& operator=(const HashTable& other)
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{
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HashTable temporary(other);
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swap(*this, temporary);
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return *this;
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}
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HashTable(HashTable&& other) noexcept
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: m_buckets(other.m_buckets)
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, m_collection_data(other.m_collection_data)
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, m_size(other.m_size)
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, m_capacity(other.m_capacity)
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, m_deleted_count(other.m_deleted_count)
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{
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other.m_size = 0;
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other.m_capacity = 0;
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other.m_deleted_count = 0;
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other.m_buckets = nullptr;
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if constexpr (IsOrdered)
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other.m_collection_data = { nullptr, nullptr };
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}
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HashTable& operator=(HashTable&& other) noexcept
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{
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HashTable temporary { move(other) };
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swap(*this, temporary);
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return *this;
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}
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friend void swap(HashTable& a, HashTable& b) noexcept
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{
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swap(a.m_buckets, b.m_buckets);
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swap(a.m_size, b.m_size);
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swap(a.m_capacity, b.m_capacity);
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swap(a.m_deleted_count, b.m_deleted_count);
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if constexpr (IsOrdered)
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swap(a.m_collection_data, b.m_collection_data);
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}
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[[nodiscard]] bool is_empty() const { return m_size == 0; }
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[[nodiscard]] size_t size() const { return m_size; }
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[[nodiscard]] size_t capacity() const { return m_capacity; }
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template<typename U, size_t N>
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ErrorOr<void> try_set_from(U (&from_array)[N])
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{
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for (size_t i = 0; i < N; ++i)
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TRY(try_set(from_array[i]));
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return {};
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}
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template<typename U, size_t N>
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void set_from(U (&from_array)[N])
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{
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MUST(try_set_from(from_array));
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}
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void ensure_capacity(size_t capacity)
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{
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VERIFY(capacity >= size());
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rehash(capacity * 2);
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}
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ErrorOr<void> try_ensure_capacity(size_t capacity)
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{
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VERIFY(capacity >= size());
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return try_rehash(capacity * 2);
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}
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[[nodiscard]] bool contains(T const& value) const
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{
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return find(value) != end();
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}
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template<Concepts::HashCompatible<T> K>
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requires(IsSame<TraitsForT, Traits<T>>) [[nodiscard]] bool contains(K const& value) const
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{
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return find(value) != end();
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}
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using Iterator = Conditional<IsOrdered,
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OrderedHashTableIterator<HashTable, T, BucketType>,
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HashTableIterator<HashTable, T, BucketType>>;
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[[nodiscard]] Iterator begin()
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{
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if constexpr (IsOrdered)
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return Iterator(m_collection_data.head);
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for (size_t i = 0; i < m_capacity; ++i) {
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if (m_buckets[i].used)
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return Iterator(&m_buckets[i]);
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}
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return end();
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}
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[[nodiscard]] Iterator end()
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{
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return Iterator(nullptr);
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}
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using ConstIterator = Conditional<IsOrdered,
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OrderedHashTableIterator<const HashTable, const T, const BucketType>,
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HashTableIterator<const HashTable, const T, const BucketType>>;
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[[nodiscard]] ConstIterator begin() const
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{
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if constexpr (IsOrdered)
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return ConstIterator(m_collection_data.head);
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for (size_t i = 0; i < m_capacity; ++i) {
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if (m_buckets[i].used)
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return ConstIterator(&m_buckets[i]);
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}
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return end();
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}
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[[nodiscard]] ConstIterator end() const
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{
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return ConstIterator(nullptr);
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}
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void clear()
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{
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*this = HashTable();
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}
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void clear_with_capacity()
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{
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if constexpr (!Detail::IsTriviallyDestructible<T>) {
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for (auto* bucket : *this)
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bucket->~T();
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}
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__builtin_memset(m_buckets, 0, size_in_bytes(capacity()));
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m_size = 0;
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m_deleted_count = 0;
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if constexpr (IsOrdered)
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m_collection_data = { nullptr, nullptr };
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else
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m_buckets[m_capacity].end = true;
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}
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template<typename U = T>
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ErrorOr<HashSetResult> try_set(U&& value, HashSetExistingEntryBehavior existing_entry_behavior = HashSetExistingEntryBehavior::Replace)
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{
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auto* bucket = TRY(try_lookup_for_writing(value));
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if (bucket->used) {
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if (existing_entry_behavior == HashSetExistingEntryBehavior::Keep)
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return HashSetResult::KeptExistingEntry;
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(*bucket->slot()) = forward<U>(value);
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return HashSetResult::ReplacedExistingEntry;
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}
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new (bucket->slot()) T(forward<U>(value));
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bucket->used = true;
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if (bucket->deleted) {
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bucket->deleted = false;
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--m_deleted_count;
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}
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if constexpr (IsOrdered) {
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if (!m_collection_data.head) [[unlikely]] {
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m_collection_data.head = bucket;
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} else {
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bucket->previous = m_collection_data.tail;
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m_collection_data.tail->next = bucket;
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}
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m_collection_data.tail = bucket;
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}
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++m_size;
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return HashSetResult::InsertedNewEntry;
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}
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template<typename U = T>
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HashSetResult set(U&& value, HashSetExistingEntryBehavior existing_entry_behaviour = HashSetExistingEntryBehavior::Replace)
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{
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return MUST(try_set(forward<U>(value), existing_entry_behaviour));
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}
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template<typename TUnaryPredicate>
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[[nodiscard]] Iterator find(unsigned hash, TUnaryPredicate predicate)
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{
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return Iterator(lookup_with_hash(hash, move(predicate)));
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}
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[[nodiscard]] Iterator find(T const& value)
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{
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return find(TraitsForT::hash(value), [&](auto& other) { return TraitsForT::equals(value, other); });
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}
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template<typename TUnaryPredicate>
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[[nodiscard]] ConstIterator find(unsigned hash, TUnaryPredicate predicate) const
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{
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return ConstIterator(lookup_with_hash(hash, move(predicate)));
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}
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[[nodiscard]] ConstIterator find(T const& value) const
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{
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return find(TraitsForT::hash(value), [&](auto& other) { return TraitsForT::equals(value, other); });
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}
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// FIXME: Support for predicates, while guaranteeing that the predicate call
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// does not call a non trivial constructor each time invoked
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template<Concepts::HashCompatible<T> K>
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requires(IsSame<TraitsForT, Traits<T>>) [[nodiscard]] Iterator find(K const& value)
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{
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return find(Traits<K>::hash(value), [&](auto& other) { return Traits<T>::equals(other, value); });
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}
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template<Concepts::HashCompatible<T> K, typename TUnaryPredicate>
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requires(IsSame<TraitsForT, Traits<T>>) [[nodiscard]] Iterator find(K const& value, TUnaryPredicate predicate)
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{
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return find(Traits<K>::hash(value), move(predicate));
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}
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template<Concepts::HashCompatible<T> K>
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requires(IsSame<TraitsForT, Traits<T>>) [[nodiscard]] ConstIterator find(K const& value) const
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{
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return find(Traits<K>::hash(value), [&](auto& other) { return Traits<T>::equals(other, value); });
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}
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template<Concepts::HashCompatible<T> K, typename TUnaryPredicate>
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requires(IsSame<TraitsForT, Traits<T>>) [[nodiscard]] ConstIterator find(K const& value, TUnaryPredicate predicate) const
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{
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return find(Traits<K>::hash(value), move(predicate));
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}
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bool remove(const T& value)
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{
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auto it = find(value);
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if (it != end()) {
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remove(it);
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return true;
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}
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return false;
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}
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template<Concepts::HashCompatible<T> K>
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requires(IsSame<TraitsForT, Traits<T>>) bool remove(K const& value)
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{
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auto it = find(value);
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if (it != end()) {
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remove(it);
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return true;
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}
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return false;
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}
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Iterator remove(Iterator iterator)
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{
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VERIFY(iterator.m_bucket);
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auto& bucket = *iterator.m_bucket;
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VERIFY(bucket.used);
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VERIFY(!bucket.deleted);
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if constexpr (!IsOrdered)
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VERIFY(!bucket.end);
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auto next_iterator = iterator;
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++next_iterator;
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delete_bucket(bucket);
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--m_size;
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++m_deleted_count;
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return next_iterator;
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}
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template<typename TUnaryPredicate>
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bool remove_all_matching(TUnaryPredicate predicate)
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{
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size_t removed_count = 0;
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for (size_t i = 0; i < m_capacity; ++i) {
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auto& bucket = m_buckets[i];
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if (bucket.used && predicate(*bucket.slot())) {
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delete_bucket(bucket);
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++removed_count;
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}
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}
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if (removed_count) {
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m_deleted_count += removed_count;
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m_size -= removed_count;
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return true;
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}
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return false;
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}
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private:
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void insert_during_rehash(T&& value)
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{
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auto& bucket = lookup_for_writing(value);
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new (bucket.slot()) T(move(value));
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bucket.used = true;
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if constexpr (IsOrdered) {
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if (!m_collection_data.head) [[unlikely]] {
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m_collection_data.head = &bucket;
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} else {
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bucket.previous = m_collection_data.tail;
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m_collection_data.tail->next = &bucket;
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}
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m_collection_data.tail = &bucket;
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}
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}
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[[nodiscard]] static constexpr size_t size_in_bytes(size_t capacity)
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{
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if constexpr (IsOrdered) {
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return sizeof(BucketType) * capacity;
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} else {
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return sizeof(BucketType) * (capacity + 1);
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}
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}
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ErrorOr<void> try_rehash(size_t new_capacity)
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{
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new_capacity = max(new_capacity, static_cast<size_t>(4));
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new_capacity = kmalloc_good_size(new_capacity * sizeof(BucketType)) / sizeof(BucketType);
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auto* old_buckets = m_buckets;
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auto old_capacity = m_capacity;
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Iterator old_iter = begin();
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auto* new_buckets = kmalloc(size_in_bytes(new_capacity));
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if (!new_buckets)
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return Error::from_errno(ENOMEM);
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m_buckets = (BucketType*)new_buckets;
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__builtin_memset(m_buckets, 0, size_in_bytes(new_capacity));
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m_capacity = new_capacity;
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m_deleted_count = 0;
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if constexpr (IsOrdered)
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m_collection_data = { nullptr, nullptr };
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else
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m_buckets[m_capacity].end = true;
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if (!old_buckets)
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return {};
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for (auto it = move(old_iter); it != end(); ++it) {
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insert_during_rehash(move(*it));
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it->~T();
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}
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kfree_sized(old_buckets, size_in_bytes(old_capacity));
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return {};
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}
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void rehash(size_t new_capacity)
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{
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MUST(try_rehash(new_capacity));
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}
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template<typename TUnaryPredicate>
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[[nodiscard]] BucketType* lookup_with_hash(unsigned hash, TUnaryPredicate predicate) const
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{
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if (is_empty())
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return nullptr;
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for (;;) {
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auto& bucket = m_buckets[hash % m_capacity];
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if (bucket.used && predicate(*bucket.slot()))
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return &bucket;
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if (!bucket.used && !bucket.deleted)
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return nullptr;
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hash = double_hash(hash);
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}
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}
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ErrorOr<BucketType*> try_lookup_for_writing(T const& value)
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{
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// FIXME: Maybe overrun the "allowed" load factor to avoid OOM
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// If we are allowed to do that, separate that logic from
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// the normal lookup_for_writing
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if (should_grow())
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TRY(try_rehash(capacity() * 2));
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auto hash = TraitsForT::hash(value);
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BucketType* first_empty_bucket = nullptr;
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for (;;) {
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auto& bucket = m_buckets[hash % m_capacity];
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if (bucket.used && TraitsForT::equals(*bucket.slot(), value))
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return &bucket;
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if (!bucket.used) {
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if (!first_empty_bucket)
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first_empty_bucket = &bucket;
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if (!bucket.deleted)
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return const_cast<BucketType*>(first_empty_bucket);
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}
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hash = double_hash(hash);
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}
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}
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[[nodiscard]] BucketType& lookup_for_writing(T const& value)
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{
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return *MUST(try_lookup_for_writing(value));
|
|
}
|
|
|
|
[[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); }
|
|
|
|
void delete_bucket(auto& bucket)
|
|
{
|
|
bucket.slot()->~T();
|
|
bucket.used = false;
|
|
bucket.deleted = true;
|
|
|
|
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;
|
|
}
|
|
}
|
|
|
|
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;
|