mirror of https://github.com/OpenTTD/OpenTTD.git
258 lines
7.1 KiB
C++
258 lines
7.1 KiB
C++
/*
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* This file is part of OpenTTD.
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* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
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* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @file hashtable.hpp Hash table support. */
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#ifndef HASHTABLE_HPP
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#define HASHTABLE_HPP
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#include "../core/math_func.hpp"
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template <class Titem_>
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struct CHashTableSlotT
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{
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typedef typename Titem_::Key Key; // make Titem_::Key a property of HashTable
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Titem_ *m_pFirst;
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inline CHashTableSlotT() : m_pFirst(nullptr) {}
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/** hash table slot helper - clears the slot by simple forgetting its items */
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inline void Clear()
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{
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m_pFirst = nullptr;
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}
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/** hash table slot helper - linear search for item with given key through the given blob - const version */
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inline const Titem_ *Find(const Key &key) const
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{
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for (const Titem_ *pItem = m_pFirst; pItem != nullptr; pItem = pItem->GetHashNext()) {
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if (pItem->GetKey() == key) {
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/* we have found the item, return it */
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return pItem;
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}
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}
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return nullptr;
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}
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/** hash table slot helper - linear search for item with given key through the given blob - non-const version */
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inline Titem_ *Find(const Key &key)
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{
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for (Titem_ *pItem = m_pFirst; pItem != nullptr; pItem = pItem->GetHashNext()) {
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if (pItem->GetKey() == key) {
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/* we have found the item, return it */
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return pItem;
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}
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}
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return nullptr;
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}
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/** hash table slot helper - add new item to the slot */
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inline void Attach(Titem_ &new_item)
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{
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assert(new_item.GetHashNext() == nullptr);
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new_item.SetHashNext(m_pFirst);
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m_pFirst = &new_item;
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}
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/** hash table slot helper - remove item from a slot */
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inline bool Detach(Titem_ &item_to_remove)
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{
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if (m_pFirst == &item_to_remove) {
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m_pFirst = item_to_remove.GetHashNext();
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item_to_remove.SetHashNext(nullptr);
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return true;
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}
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Titem_ *pItem = m_pFirst;
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for (;;) {
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if (pItem == nullptr) {
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return false;
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}
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Titem_ *pNextItem = pItem->GetHashNext();
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if (pNextItem == &item_to_remove) break;
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pItem = pNextItem;
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}
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pItem->SetHashNext(item_to_remove.GetHashNext());
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item_to_remove.SetHashNext(nullptr);
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return true;
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}
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/** hash table slot helper - remove and return item from a slot */
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inline Titem_ *Detach(const Key &key)
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{
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/* do we have any items? */
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if (m_pFirst == nullptr) {
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return nullptr;
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}
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/* is it our first item? */
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if (m_pFirst->GetKey() == key) {
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Titem_ &ret_item = *m_pFirst;
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m_pFirst = m_pFirst->GetHashNext();
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ret_item.SetHashNext(nullptr);
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return &ret_item;
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}
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/* find it in the following items */
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Titem_ *pPrev = m_pFirst;
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for (Titem_ *pItem = m_pFirst->GetHashNext(); pItem != nullptr; pPrev = pItem, pItem = pItem->GetHashNext()) {
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if (pItem->GetKey() == key) {
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/* we have found the item, unlink and return it */
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pPrev->SetHashNext(pItem->GetHashNext());
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pItem->SetHashNext(nullptr);
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return pItem;
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}
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}
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return nullptr;
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}
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};
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/**
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* class CHashTableT<Titem, Thash_bits> - simple hash table
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* of pointers allocated elsewhere.
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*
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* Supports: Add/Find/Remove of Titems.
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*
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* Your Titem must meet some extra requirements to be CHashTableT
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* compliant:
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* - its constructor/destructor (if any) must be public
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* - if the copying of item requires an extra resource management,
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* you must define also copy constructor
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* - must support nested type (struct, class or typedef) Titem::Key
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* that defines the type of key class for that item
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* - must support public method:
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* const Key& GetKey() const; // return the item's key object
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*
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* In addition, the Titem::Key class must support:
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* - public method that calculates key's hash:
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* int CalcHash() const;
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* - public 'equality' operator to compare the key with another one
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* bool operator==(const Key &other) const;
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*/
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template <class Titem_, int Thash_bits_>
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class CHashTableT {
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public:
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typedef Titem_ Titem; // make Titem_ visible from outside of class
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typedef typename Titem_::Key Tkey; // make Titem_::Key a property of HashTable
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static const int Thash_bits = Thash_bits_; // publish num of hash bits
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static const int Tcapacity = 1 << Thash_bits; // and num of slots 2^bits
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protected:
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/**
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* each slot contains pointer to the first item in the list,
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* Titem contains pointer to the next item - GetHashNext(), SetHashNext()
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*/
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typedef CHashTableSlotT<Titem_> Slot;
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Slot m_slots[Tcapacity]; // here we store our data (array of blobs)
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int m_num_items; // item counter
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public:
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/* default constructor */
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inline CHashTableT() : m_num_items(0)
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{
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}
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protected:
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/** static helper - return hash for the given key modulo number of slots */
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inline static int CalcHash(const Tkey &key)
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{
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uint32_t hash = key.CalcHash();
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hash -= (hash >> 17); // hash * 131071 / 131072
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hash -= (hash >> 5); // * 31 / 32
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hash &= (1 << Thash_bits) - 1; // modulo slots
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return hash;
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}
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/** static helper - return hash for the given item modulo number of slots */
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inline static int CalcHash(const Titem_ &item)
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{
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return CalcHash(item.GetKey());
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}
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public:
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/** item count */
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inline int Count() const
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{
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return m_num_items;
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}
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/** simple clear - forget all items - used by CSegmentCostCacheT.Flush() */
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inline void Clear()
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{
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for (int i = 0; i < Tcapacity; i++) m_slots[i].Clear();
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}
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/** const item search */
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const Titem_ *Find(const Tkey &key) const
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{
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int hash = CalcHash(key);
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const Slot &slot = m_slots[hash];
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const Titem_ *item = slot.Find(key);
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return item;
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}
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/** non-const item search */
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Titem_ *Find(const Tkey &key)
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{
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int hash = CalcHash(key);
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Slot &slot = m_slots[hash];
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Titem_ *item = slot.Find(key);
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return item;
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}
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/** non-const item search & optional removal (if found) */
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Titem_ *TryPop(const Tkey &key)
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{
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int hash = CalcHash(key);
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Slot &slot = m_slots[hash];
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Titem_ *item = slot.Detach(key);
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if (item != nullptr) {
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m_num_items--;
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}
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return item;
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}
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/** non-const item search & removal */
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Titem_ &Pop(const Tkey &key)
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{
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Titem_ *item = TryPop(key);
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assert(item != nullptr);
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return *item;
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}
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/** non-const item search & optional removal (if found) */
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bool TryPop(Titem_ &item)
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{
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const Tkey &key = item.GetKey();
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int hash = CalcHash(key);
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Slot &slot = m_slots[hash];
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bool ret = slot.Detach(item);
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if (ret) {
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m_num_items--;
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}
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return ret;
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}
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/** non-const item search & removal */
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void Pop(Titem_ &item)
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{
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[[maybe_unused]] bool ret = TryPop(item);
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assert(ret);
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}
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/** add one item - copy it from the given item */
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void Push(Titem_ &new_item)
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{
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int hash = CalcHash(new_item);
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Slot &slot = m_slots[hash];
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assert(slot.Find(new_item.GetKey()) == nullptr);
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slot.Attach(new_item);
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m_num_items++;
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}
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};
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#endif /* HASHTABLE_HPP */
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