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370 lines
8.4 KiB
C++
370 lines
8.4 KiB
C++
//
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// HashTable.h
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//
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// Library: Foundation
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// Package: Hashing
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// Module: HashTable
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//
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// Definition of the HashTable class.
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//
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// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_HashTable_INCLUDED
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#define Foundation_HashTable_INCLUDED
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#include "Poco/Foundation.h"
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#include "Poco/Exception.h"
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#include "Poco/HashFunction.h"
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#include "Poco/HashStatistic.h"
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#include <vector>
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#include <map>
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#include <cstddef>
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#include <cstring>
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namespace Poco {
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//@ deprecated
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template <class Key, class Value, class KeyHashFunction = HashFunction<Key>>
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class HashTable
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/// A HashTable stores a key value pair that can be looked up via a hashed key.
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///
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/// Collision handling is done via overflow maps(!). With small hash tables performance of this
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/// data struct will be closer to that a map than a hash table, i.e. slower. On the plus side,
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/// this class offers remove operations. Also HashTable full errors are not possible. If a fast
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/// HashTable implementation is needed and the remove operation is not required, use SimpleHashTable
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/// instead.
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///
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/// This class is NOT thread safe.
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{
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public:
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typedef std::map<Key, Value> HashEntryMap;
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typedef HashEntryMap** HashTableVector;
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typedef typename HashEntryMap::const_iterator ConstIterator;
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typedef typename HashEntryMap::iterator Iterator;
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HashTable(UInt32 initialSize = 251):
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_entries(0),
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_size(0),
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_maxCapacity(initialSize)
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/// Creates the HashTable.
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{
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_entries = new HashEntryMap*[initialSize];
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memset(_entries, '\0', sizeof(HashEntryMap*)*initialSize);
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}
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HashTable(const HashTable& ht):
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_entries(new HashEntryMap*[ht._maxCapacity]),
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_size(ht._size),
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_maxCapacity(ht._maxCapacity)
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{
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for (UInt32 i = 0; i < _maxCapacity; ++i)
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{
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if (ht._entries[i])
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_entries[i] = new HashEntryMap(ht._entries[i]->begin(), ht._entries[i]->end());
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else
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_entries[i] = 0;
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}
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}
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~HashTable()
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/// Destroys the HashTable.
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{
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clear();
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}
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HashTable& operator = (const HashTable& ht)
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{
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if (this != &ht)
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{
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clear();
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_maxCapacity = ht._maxCapacity;
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poco_assert_dbg (_entries == 0);
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_entries = new HashEntryMap*[_maxCapacity];
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_size = ht._size;
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for (UInt32 i = 0; i < _maxCapacity; ++i)
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{
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if (ht._entries[i])
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_entries[i] = new HashEntryMap(ht._entries[i]->begin(), ht._entries[i]->end());
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else
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_entries[i] = 0;
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}
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}
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return *this;
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}
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void clear()
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{
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if (!_entries)
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return;
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for (UInt32 i = 0; i < _maxCapacity; ++i)
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{
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delete _entries[i];
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}
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delete[] _entries;
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_entries = 0;
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_size = 0;
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_maxCapacity = 0;
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}
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UInt32 insert(const Key& key, const Value& value)
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/// Returns the hash value of the inserted item.
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/// Throws an exception if the entry was already inserted
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{
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UInt32 hsh = hash(key);
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insertRaw(key, hsh, value);
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return hsh;
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}
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Value& insertRaw(const Key& key, UInt32 hsh, const Value& value)
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/// Returns the hash value of the inserted item.
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/// Throws an exception if the entry was already inserted
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{
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if (!_entries[hsh])
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_entries[hsh] = new HashEntryMap();
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std::pair<typename HashEntryMap::iterator, bool> res(_entries[hsh]->insert(std::make_pair(key, value)));
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if (!res.second)
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throw InvalidArgumentException("HashTable::insert, key already exists.");
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_size++;
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return res.first->second;
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}
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UInt32 update(const Key& key, const Value& value)
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/// Returns the hash value of the inserted item.
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/// Replaces an existing entry if it finds one
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{
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UInt32 hsh = hash(key);
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updateRaw(key, hsh, value);
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return hsh;
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}
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void updateRaw(const Key& key, UInt32 hsh, const Value& value)
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/// Returns the hash value of the inserted item.
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/// Replaces an existing entry if it finds one
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{
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if (!_entries[hsh])
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_entries[hsh] = new HashEntryMap();
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std::pair<Iterator, bool> res = _entries[hsh]->insert(std::make_pair(key, value));
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if (res.second == false)
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res.first->second = value;
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else
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_size++;
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}
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void remove(const Key& key)
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{
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UInt32 hsh = hash(key);
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removeRaw(key, hsh);
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}
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void removeRaw(const Key& key, UInt32 hsh)
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/// Performance version, allows to specify the hash value
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{
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if (_entries[hsh])
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{
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_size -= _entries[hsh]->erase(key);
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}
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}
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UInt32 hash(const Key& key) const
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{
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return _hash(key, _maxCapacity);
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}
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const Value& get(const Key& key) const
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/// Throws an exception if the value does not exist
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{
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UInt32 hsh = hash(key);
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return getRaw(key, hsh);
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}
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const Value& getRaw(const Key& key, UInt32 hsh) const
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/// Throws an exception if the value does not exist
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{
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if (!_entries[hsh])
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throw InvalidArgumentException("key not found");
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ConstIterator it = _entries[hsh]->find(key);
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if (it == _entries[hsh]->end())
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throw InvalidArgumentException("key not found");
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return it->second;
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}
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Value& get(const Key& key)
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/// Throws an exception if the value does not exist
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{
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UInt32 hsh = hash(key);
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return const_cast<Value&>(getRaw(key, hsh));
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}
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const Value& operator [] (const Key& key) const
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{
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return get(key);
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}
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Value& operator [] (const Key& key)
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{
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UInt32 hsh = hash(key);
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if (!_entries[hsh])
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return insertRaw(key, hsh, Value());
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ConstIterator it = _entries[hsh]->find(key);
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if (it == _entries[hsh]->end())
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return insertRaw(key, hsh, Value());
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return it->second;
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}
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const Key& getKeyRaw(const Key& key, UInt32 hsh)
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/// Throws an exception if the key does not exist. returns a reference to the internally
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/// stored key. Useful when someone does an insert and wants for performance reason only to store
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/// a pointer to the key in another collection
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{
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if (!_entries[hsh])
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throw InvalidArgumentException("key not found");
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ConstIterator it = _entries[hsh]->find(key);
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if (it == _entries[hsh]->end())
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throw InvalidArgumentException("key not found");
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return it->first;
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}
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bool get(const Key& key, Value& v) const
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/// Sets v to the found value, returns false if no value was found
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{
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UInt32 hsh = hash(key);
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return getRaw(key, hsh, v);
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}
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bool getRaw(const Key& key, UInt32 hsh, Value& v) const
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/// Sets v to the found value, returns false if no value was found
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{
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if (!_entries[hsh])
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return false;
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ConstIterator it = _entries[hsh]->find(key);
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if (it == _entries[hsh]->end())
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return false;
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v = it->second;
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return true;
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}
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bool exists(const Key& key)
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{
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UInt32 hsh = hash(key);
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return existsRaw(key, hsh);
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}
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bool existsRaw(const Key& key, UInt32 hsh)
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{
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return _entries[hsh] && (_entries[hsh]->end() != _entries[hsh]->find(key));
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}
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std::size_t size() const
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/// Returns the number of elements already inserted into the HashTable
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{
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return _size;
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}
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UInt32 maxCapacity() const
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{
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return _maxCapacity;
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}
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void resize(UInt32 newSize)
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/// Resizes the hashtable, rehashes all existing entries. Expensive!
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{
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if (_maxCapacity != newSize)
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{
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HashTableVector cpy = _entries;
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_entries = 0;
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UInt32 oldSize = _maxCapacity;
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_maxCapacity = newSize;
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_entries = new HashEntryMap*[_maxCapacity];
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memset(_entries, '\0', sizeof(HashEntryMap*)*_maxCapacity);
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if (_size == 0)
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{
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// no data was yet inserted
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delete[] cpy;
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return;
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}
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_size = 0;
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for (UInt32 i = 0; i < oldSize; ++i)
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{
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if (cpy[i])
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{
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ConstIterator it = cpy[i]->begin();
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ConstIterator itEnd = cpy[i]->end();
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for (; it != itEnd; ++it)
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{
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insert(it->first, it->second);
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}
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delete cpy[i];
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}
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}
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delete[] cpy;
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}
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}
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HashStatistic currentState(bool details = false) const
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/// Returns the current internal state
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{
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UInt32 numberOfEntries = (UInt32)_size;
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UInt32 numZeroEntries = 0;
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UInt32 maxEntriesPerHash = 0;
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std::vector<UInt32> detailedEntriesPerHash;
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#ifdef _DEBUG
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UInt32 totalSize = 0;
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#endif
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for (UInt32 i = 0; i < _maxCapacity; ++i)
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{
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if (_entries[i])
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{
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UInt32 size = (UInt32)_entries[i]->size();
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poco_assert_dbg(size != 0);
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if (size > maxEntriesPerHash)
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maxEntriesPerHash = size;
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if (details)
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detailedEntriesPerHash.push_back(size);
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#ifdef _DEBUG
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totalSize += size;
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#endif
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}
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else
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{
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numZeroEntries++;
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if (details)
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detailedEntriesPerHash.push_back(0);
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}
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}
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#ifdef _DEBUG
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poco_assert_dbg(totalSize == numberOfEntries);
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#endif
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return HashStatistic(_maxCapacity, numberOfEntries, numZeroEntries, maxEntriesPerHash, detailedEntriesPerHash);
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}
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private:
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HashTableVector _entries;
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std::size_t _size;
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UInt32 _maxCapacity;
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KeyHashFunction _hash;
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};
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} // namespace Poco
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#endif // Foundation_HashTable_INCLUDED
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