ladybird/AK/HashTable.h

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#pragma once
#include "Assertions.h"
#include "DoublyLinkedList.h"
#include "Traits.h"
#include <cstdlib>
#include <utility>
//#define HASHTABLE_DEBUG
namespace AK {
template<typename T, typename = Traits<T>> class HashTable;
template<typename T, typename TraitsForT>
class HashTable {
private:
struct Bucket {
DoublyLinkedList<T> chain;
};
public:
HashTable() { }
explicit HashTable(HashTable&& other)
: m_buckets(other.m_buckets)
, m_size(other.m_size)
, m_capacity(other.m_capacity)
{
other.m_size = 0;
other.m_capacity = 0;
other.m_buckets = nullptr;
}
HashTable& operator=(HashTable&& other)
{
if (this != &other) {
m_buckets = other.m_buckets;
m_size = other.m_size;
m_capacity = other.m_capacity;
other.m_size = 0;
other.m_capacity = 0;
other.m_buckets = nullptr;
}
return *this;
}
~HashTable() { clear(); }
bool isEmpty() const { return !m_size; }
unsigned size() const { return m_size; }
unsigned capacity() const { return m_capacity; }
void set(T&&);
bool contains(const T&) const;
void clear();
void dump() const;
class Iterator {
public:
bool operator!=(const Iterator& other)
{
if (m_isEnd && other.m_isEnd)
return false;
return &m_table != &other.m_table
|| m_isEnd != other.m_isEnd
|| m_bucketIndex != other.m_bucketIndex
|| m_bucketIterator != other.m_bucketIterator;
}
T& operator*()
{
#ifdef HASHTABLE_DEBUG
printf("retrieve { bucketIndex: %u, isEnd: %u }\n", m_bucketIndex, m_isEnd);
#endif
return *m_bucketIterator;
}
Iterator& operator++()
{
skipToNext();
return *this;
}
void skipToNext()
{
#ifdef HASHTABLE_DEBUG
unsigned pass = 0;
#endif
while (!m_isEnd) {
#ifdef HASHTABLE_DEBUG
++pass;
printf("skipToNext pass %u, m_bucketIndex=%u\n", pass, m_bucketIndex);
#endif
if (m_bucketIterator.isEnd()) {
++m_bucketIndex;
if (m_bucketIndex >= m_table.capacity()) {
m_isEnd = true;
return;
}
m_bucketIterator = m_table.m_buckets[m_bucketIndex].chain.begin();
} else {
++m_bucketIterator;
}
if (!m_bucketIterator.isEnd())
return;
}
}
private:
friend class HashTable;
explicit Iterator(HashTable& table, bool isEnd, typename DoublyLinkedList<T>::Iterator bucketIterator = DoublyLinkedList<T>::Iterator::universalEnd())
: m_table(table)
, m_isEnd(isEnd)
, m_bucketIterator(bucketIterator)
{
if (!isEnd && !m_table.isEmpty() && !(m_bucketIterator != DoublyLinkedList<T>::Iterator::universalEnd())) {
#ifdef HASHTABLE_DEBUG
printf("bucket iterator init!\n");
#endif
m_bucketIterator = m_table.m_buckets[0].chain.begin();
if (m_bucketIterator.isEnd())
skipToNext();
}
}
HashTable& m_table;
unsigned m_bucketIndex { 0 };
bool m_isEnd { false };
typename DoublyLinkedList<T>::Iterator m_bucketIterator;
};
Iterator begin() { return Iterator(*this, false); }
Iterator end() { return Iterator(*this, true); }
class ConstIterator {
public:
bool operator!=(const ConstIterator& other)
{
if (m_isEnd && other.m_isEnd)
return false;
return &m_table != &other.m_table
|| m_isEnd != other.m_isEnd
|| m_bucketIndex != other.m_bucketIndex
|| m_bucketIterator != other.m_bucketIterator;
}
const T& operator*() const
{
#ifdef HASHTABLE_DEBUG
printf("retrieve { bucketIndex: %u, isEnd: %u }\n", m_bucketIndex, m_isEnd);
#endif
return *m_bucketIterator;
}
ConstIterator& operator++()
{
skipToNext();
return *this;
}
void skipToNext()
{
#ifdef HASHTABLE_DEBUG
unsigned pass = 0;
#endif
while (!m_isEnd) {
#ifdef HASHTABLE_DEBUG
++pass;
printf("skipToNext pass %u, m_bucketIndex=%u\n", pass, m_bucketIndex);
#endif
if (m_bucketIterator.isEnd()) {
++m_bucketIndex;
if (m_bucketIndex >= m_table.capacity()) {
m_isEnd = true;
return;
}
const DoublyLinkedList<T>& chain = m_table.m_buckets[m_bucketIndex].chain;
m_bucketIterator = chain.begin();
} else {
++m_bucketIterator;
}
if (!m_bucketIterator.isEnd())
return;
}
}
private:
friend class HashTable;
ConstIterator(const HashTable& table, bool isEnd, typename DoublyLinkedList<T>::ConstIterator bucketIterator = DoublyLinkedList<T>::ConstIterator::universalEnd())
: m_table(table)
, m_isEnd(isEnd)
, m_bucketIterator(bucketIterator)
{
if (!isEnd && !m_table.isEmpty() && !(m_bucketIterator != DoublyLinkedList<T>::ConstIterator::universalEnd())) {
#ifdef HASHTABLE_DEBUG
printf("bucket iterator init!\n");
#endif
const DoublyLinkedList<T>& chain = m_table.m_buckets[0].chain;
m_bucketIterator = chain.begin();
skipToNext();
}
}
const HashTable& m_table;
unsigned m_bucketIndex { 0 };
bool m_isEnd { false };
typename DoublyLinkedList<T>::ConstIterator m_bucketIterator;
};
ConstIterator begin() const { return ConstIterator(*this, false); }
ConstIterator end() const { return ConstIterator(*this, true); }
Iterator find(const T&);
ConstIterator find(const T&) const;
private:
Bucket& lookup(const T&);
const Bucket& lookup(const T&) const;
void rehash(unsigned capacity);
void insert(T&&);
Bucket* m_buckets { nullptr };
unsigned m_size { 0 };
unsigned m_capacity { 0 };
};
template<typename T, typename TraitsForT>
void HashTable<T, TraitsForT>::set(T&& value)
{
if (!m_capacity)
rehash(1);
auto& bucket = lookup(value);
for (auto& e : bucket.chain) {
if (e == value)
return;
}
if (size() >= capacity()) {
rehash(size() + 1);
insert(std::move(value));
} else {
bucket.chain.append(std::move(value));
}
m_size++;
}
template<typename T, typename TraitsForT>
void HashTable<T, TraitsForT>::rehash(unsigned newCapacity)
{
newCapacity *= 2;
#ifdef HASHTABLE_DEBUG
printf("rehash to %u buckets\n", newCapacity);
#endif
auto* newBuckets = new Bucket[newCapacity];
auto* oldBuckets = m_buckets;
unsigned oldCapacity = m_capacity;
m_buckets = newBuckets;
m_capacity = newCapacity;
#ifdef HASHTABLE_DEBUG
printf("reinsert %u buckets\n", oldCapacity);
#endif
for (unsigned i = 0; i < oldCapacity; ++i) {
for (auto& value : oldBuckets[i].chain) {
insert(std::move(value));
}
}
delete [] oldBuckets;
}
template<typename T, typename TraitsForT>
void HashTable<T, TraitsForT>::clear()
{
delete [] m_buckets;
m_capacity = 0;
m_size = 0;
}
template<typename T, typename TraitsForT>
void HashTable<T, TraitsForT>::insert(T&& value)
{
auto& bucket = lookup(value);
bucket.chain.append(std::move(value));
}
template<typename T, typename TraitsForT>
bool HashTable<T, TraitsForT>::contains(const T& value) const
{
if (isEmpty())
return false;
auto& bucket = lookup(value);
for (auto& e : bucket.chain) {
if (e == value)
return true;
}
return false;
}
template<typename T, typename TraitsForT>
auto HashTable<T, TraitsForT>::find(const T& value) -> Iterator
{
if (isEmpty())
return end();
auto& bucket = lookup(value);
auto bucketIterator = bucket.chain.find(value);
if (bucketIterator != bucket.chain.end())
return Iterator(*this, false, bucketIterator);
return end();
}
template<typename T, typename TraitsForT>
auto HashTable<T, TraitsForT>::find(const T& value) const -> ConstIterator
{
if (isEmpty())
return end();
auto& bucket = lookup(value);
auto bucketIterator = bucket.chain.find(value);
if (bucketIterator != bucket.chain.end())
return ConstIterator(*this, false, bucketIterator);
return end();
}
template<typename T, typename TraitsForT>
typename HashTable<T, TraitsForT>::Bucket& HashTable<T, TraitsForT>::lookup(const T& value)
{
unsigned hash = TraitsForT::hash(value);
#ifdef HASHTABLE_DEBUG
printf("hash for ");
TraitsForT::dump(value);
printf(" is %u\n", hash);
#endif
return m_buckets[hash % m_capacity];
}
template<typename T, typename TraitsForT>
const typename HashTable<T, TraitsForT>::Bucket& HashTable<T, TraitsForT>::lookup(const T& value) const
{
unsigned hash = TraitsForT::hash(value);
#ifdef HASHTABLE_DEBUG
printf("hash for ");
TraitsForT::dump(value);
printf(" is %u\n", hash);
#endif
return m_buckets[hash % m_capacity];
}
template<typename T, typename TraitsForT>
void HashTable<T, TraitsForT>::dump() const
{
printf("HashTable{%p} m_size=%u, m_capacity=%u, m_buckets=%p\n", this, m_size, m_capacity, m_buckets);
for (unsigned i = 0; i < m_capacity; ++i) {
auto& bucket = m_buckets[i];
printf("Bucket %u\n", i);
for (auto& e : bucket.chain) {
printf(" > ");
TraitsForT::dump(e);
printf("\n");
}
}
}
}
using AK::HashTable;