forked from mirror/OpenTTD
(svn r8092) -Codechange: header files with miscellaneous template classes (smart pointers, blob, array, hashtable, etc.) moved from src/yapf to src/misc as they can now be used anywhere.
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KUDr
240
src/misc/hashtable.hpp
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240
src/misc/hashtable.hpp
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/* $Id$ */
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#ifndef HASHTABLE_HPP
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#define HASHTABLE_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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CHashTableSlotT() : m_pFirst(NULL) {}
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/** hash table slot helper - clears the slot by simple forgetting its items */
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FORCEINLINE void Clear() {m_pFirst = NULL;}
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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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FORCEINLINE const Titem_* Find(const Key& key) const
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{
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for (const Titem_* pItem = m_pFirst; pItem != NULL; 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 NULL;
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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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FORCEINLINE Titem_* Find(const Key& key)
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{
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for (Titem_* pItem = m_pFirst; pItem != NULL; 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 NULL;
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}
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/** hash table slot helper - add new item to the slot */
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FORCEINLINE void Attach(Titem_& new_item)
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{
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assert(new_item.GetHashNext() == NULL);
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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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FORCEINLINE 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(NULL);
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return true;
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}
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Titem_* pItem = m_pFirst;
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while (true) {
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if (pItem == NULL) {
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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(NULL);
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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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FORCEINLINE 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 == NULL) {
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return NULL;
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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(NULL);
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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 != NULL; 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(NULL);
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return pItem;
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}
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}
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return NULL;
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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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/** 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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typedef CHashTableSlotT<Titem_> Slot;
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Slot* m_slots; // 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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FORCEINLINE CHashTableT()
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{
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// construct all slots
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m_slots = new Slot[Tcapacity];
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m_num_items = 0;
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}
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~CHashTableT() {delete [] m_slots; m_num_items = 0; m_slots = NULL;}
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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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FORCEINLINE static int CalcHash(const Tkey& key)
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{
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int32 hash = key.CalcHash();
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if ((8 * Thash_bits) < 32) hash ^= hash >> (min(8 * Thash_bits, 31));
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if ((4 * Thash_bits) < 32) hash ^= hash >> (min(4 * Thash_bits, 31));
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if ((2 * Thash_bits) < 32) hash ^= hash >> (min(2 * Thash_bits, 31));
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if ((1 * Thash_bits) < 32) hash ^= hash >> (min(1 * Thash_bits, 31));
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hash &= (1 << Thash_bits) - 1;
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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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FORCEINLINE static int CalcHash(const Titem_& item) {return CalcHash(item.GetKey());}
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public:
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/** item count */
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FORCEINLINE int Count() const {return m_num_items;}
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/** simple clear - forget all items - used by CSegmentCostCacheT.Flush() */
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FORCEINLINE void Clear() const {for (int i = 0; i < Tcapacity; i++) m_slots[i].Clear();}
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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 != NULL) {
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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 != NULL);
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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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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()) == NULL);
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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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