poco/Foundation/include/Poco/SimpleHashTable.h

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//
// SimpleHashTable.h
//
// $Id: //poco/1.4/Foundation/include/Poco/SimpleHashTable.h#1 $
//
// Library: Foundation
// Package: Hashing
// Module: SimpleHashTable
//
// Definition of the SimpleHashTable class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
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//
#ifndef Foundation_SimpleHashTable_INCLUDED
#define Foundation_SimpleHashTable_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/HashFunction.h"
#include "Poco/HashStatistic.h"
#include <vector>
#include <map>
#include <cstddef>
#include <algorithm>
namespace Poco {
//@ deprecated
template <class Key, class Value, class KeyHashFunction = HashFunction<Key> >
class SimpleHashTable
/// A SimpleHashTable stores a key value pair that can be looked up via a hashed key.
///
/// In comparision to a HashTable, this class handles collisions by sequentially searching the next
/// free location. This also means that the maximum size of this table is limited, i.e. if the hash table
/// is full, it will throw an exception and that this class does not support remove operations.
/// On the plus side it is faster than the HashTable.
///
/// This class is NOT thread safe.
{
public:
class HashEntry
{
public:
Key key;
Value value;
HashEntry(const Key k, const Value v): key(k), value(v)
{
}
};
typedef std::vector<HashEntry*> HashTableVector;
SimpleHashTable(UInt32 capacity = 251): _entries(capacity, 0), _size(0), _capacity(capacity)
/// Creates the SimpleHashTable.
{
}
SimpleHashTable(const SimpleHashTable& ht):
_size(ht._size),
_capacity(ht._capacity)
{
_entries.reserve(ht._capacity);
for (typename HashTableVector::iterator it = ht._entries.begin(); it != ht._entries.end(); ++it)
{
if (*it)
_entries.push_back(new HashEntry(*it));
else
_entries.push_back(0);
}
}
~SimpleHashTable()
/// Destroys the SimpleHashTable.
{
clear();
}
SimpleHashTable& operator = (const SimpleHashTable& ht)
{
if (this != &ht)
{
SimpleHashTable tmp(ht);
swap(tmp);
}
return *this;
}
void swap(SimpleHashTable& ht)
{
using std::swap;
swap(_entries, ht._entries);
swap(_size, ht._size);
swap(_capacity, ht._capacity);
}
void clear()
{
for (typename HashTableVector::iterator it = _entries.begin(); it != _entries.end(); ++it)
{
delete *it;
*it = 0;
}
_size = 0;
}
UInt32 insert(const Key& key, const Value& value)
/// Returns the hash value of the inserted item.
/// Throws an exception if the entry was already inserted
{
UInt32 hsh = hash(key);
insertRaw(key, hsh, value);
return hsh;
}
Value& insertRaw(const Key& key, UInt32 hsh, const Value& value)
/// Returns the hash value of the inserted item.
/// Throws an exception if the entry was already inserted
{
UInt32 pos = hsh;
if (!_entries[pos])
_entries[pos] = new HashEntry(key, value);
else
{
UInt32 origHash = hsh;
while (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
throw ExistsException();
if (hsh - origHash > _capacity)
throw PoolOverflowException("SimpleHashTable full");
hsh++;
}
pos = hsh % _capacity;
_entries[pos] = new HashEntry(key, value);
}
_size++;
return _entries[pos]->value;
}
UInt32 update(const Key& key, const Value& value)
/// Returns the hash value of the inserted item.
/// Replaces an existing entry if it finds one
{
UInt32 hsh = hash(key);
updateRaw(key, hsh, value);
return hsh;
}
void updateRaw(const Key& key, UInt32 hsh, const Value& value)
/// Returns the hash value of the inserted item.
/// Replaces an existing entry if it finds one
{
if (!_entries[hsh])
_entries[hsh] = new HashEntry(key, value);
else
{
UInt32 origHash = hsh;
while (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
_entries[hsh % _capacity]->value = value;
return;
}
if (hsh - origHash > _capacity)
throw PoolOverflowException("SimpleHashTable full");
hsh++;
}
_entries[hsh % _capacity] = new HashEntry(key, value);
}
_size++;
}
UInt32 hash(const Key& key) const
{
return _hash(key, _capacity);
}
const Value& get(const Key& key) const
/// Throws an exception if the value does not exist
{
UInt32 hsh = hash(key);
return getRaw(key, hsh);
}
const Value& getRaw(const Key& key, UInt32 hsh) const
/// Throws an exception if the value does not exist
{
UInt32 origHash = hsh;
while (true)
{
if (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
return _entries[hsh % _capacity]->value;
}
}
else
throw InvalidArgumentException("value not found");
if (hsh - origHash > _capacity)
throw InvalidArgumentException("value not found");
hsh++;
}
}
Value& get(const Key& key)
/// Throws an exception if the value does not exist
{
UInt32 hsh = hash(key);
return const_cast<Value&>(getRaw(key, hsh));
}
const Value& operator [] (const Key& key) const
{
return get(key);
}
Value& operator [] (const Key& key)
{
UInt32 hsh = hash(key);
UInt32 origHash = hsh;
while (true)
{
if (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
return _entries[hsh % _capacity]->value;
}
}
else return insertRaw(key, hsh, Value());
if (hsh - origHash > _capacity)
return insertRaw(key, hsh, Value());
hsh++;
}
}
const Key& getKeyRaw(const Key& key, UInt32 hsh)
/// Throws an exception if the key does not exist. returns a reference to the internally
/// stored key. Useful when someone does an insert and wants for performance reason only to store
/// a pointer to the key in another collection
{
UInt32 origHash = hsh;
while (true)
{
if (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
return _entries[hsh % _capacity]->key;
}
}
else
throw InvalidArgumentException("key not found");
if (hsh - origHash > _capacity)
throw InvalidArgumentException("key not found");
hsh++;
}
}
bool get(const Key& key, Value& v) const
/// Sets v to the found value, returns false if no value was found
{
UInt32 hsh = hash(key);
return getRaw(key, hsh, v);
}
bool getRaw(const Key& key, UInt32 hsh, Value& v) const
/// Sets v to the found value, returns false if no value was found
{
UInt32 origHash = hsh;
while (true)
{
if (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
v = _entries[hsh % _capacity]->value;
return true;
}
}
else
return false;
if (hsh - origHash > _capacity)
return false;
hsh++;
}
}
bool exists(const Key& key) const
{
UInt32 hsh = hash(key);
return existsRaw(key, hsh);
}
bool existsRaw(const Key& key, UInt32 hsh) const
{
UInt32 origHash = hsh;
while (true)
{
if (_entries[hsh % _capacity])
{
if (_entries[hsh % _capacity]->key == key)
{
return true;
}
}
else
return false;
if (hsh - origHash > _capacity)
return false;
hsh++;
}
}
std::size_t size() const
/// Returns the number of elements already inserted into the SimpleHashTable
{
return _size;
}
UInt32 capacity() const
{
return _capacity;
}
void resize(UInt32 newSize)
/// Resizes the hashtable, rehashes all existing entries. Expensive!
{
if (_capacity != newSize)
{
SimpleHashTable tmp(newSize);
swap(tmp);
for (typename HashTableVector::const_iterator it = tmp._entries.begin(); it != tmp._entries.end(); ++it)
{
if (*it)
{
insertRaw((*it)->key, hash((*it)->key), (*it)->value);
}
}
}
}
HashStatistic currentState(bool details = false) const
/// Returns the current internal state
{
UInt32 numberOfEntries = (UInt32)_size;
UInt32 numZeroEntries = 0;
UInt32 maxEntriesPerHash = 0;
std::vector<UInt32> detailedEntriesPerHash;
#ifdef _DEBUG
UInt32 totalSize = 0;
#endif
for (int i=0; i < _capacity; ++i)
{
if (_entries[i])
{
maxEntriesPerHash = 1;
UInt32 size = 1;
if (details)
detailedEntriesPerHash.push_back(size);
#ifdef _DEBUG
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totalSize += size;
#endif
}
else
{
numZeroEntries++;
if (details)
detailedEntriesPerHash.push_back(0);
}
}
#ifdef _DEBUG
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poco_assert_dbg(totalSize == numberOfEntries);
#endif
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return HashStatistic(_capacity, numberOfEntries, numZeroEntries, maxEntriesPerHash, detailedEntriesPerHash);
}
private:
HashTableVector _entries;
std::size_t _size;
UInt32 _capacity;
KeyHashFunction _hash;
};
} // namespace Poco
#endif // Foundation_HashTable_INCLUDED