chrono::ChHashTable< K, T, H, E > Class Template Reference

#include <CHhashTable.h>

List of all members.

Public Types
typedef unsigned	size_type
typedef K	key_type
typedef T	data_type
typedef T	mapped_type
typedef std::pair< const K, T >	value_type
typedef ch_hash_iterator< K, T, H, E, value_type >	iterator
typedef ch_hash_iterator< K, T, H, E, const value_type >	const_iterator
Public Member Functions
	ChHashTable (unsigned bins=0)
	ChHashTable (const ChHashTable &)
ChHashTable &	operator= (const ChHashTable &)
bool	empty (void) const
unsigned	size (void) const
bool	operator== (const ChHashTable &) const
bool	operator!= (const ChHashTable &) const
void	auto_rehash (void)
void	manual_rehash (void)
void	rehash (unsigned bins=0)
float	loading (void) const
bool	present (const K &key) const
size_type	count (const K &key) const
iterator	insert (const K &key, const T &data)
std::pair< iterator, bool >	insert (const value_type &value)
iterator	insert (const K &key)
bool	erase (const K &key)
void	erase (void)
void	clear (void)
const_iterator	find (const K &key) const
iterator	find (const K &key)
const T &	operator[] (const K &key) const
T &	operator[] (const K &key)
const_iterator	begin (void) const
iterator	begin (void)
const_iterator	end (void) const
iterator	end (void)
Friends
class	hash_element< K, T >
class	ch_hash_iterator< K, T, H, E, std::pair< const K, T > >
class	ch_hash_iterator< K, T, H, E, const std::pair< const K, T > >

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Detailed Description

template<typename K, typename T, class H = HashFunction_Generic<K>, class E = std::equal_to<K>>
class chrono::ChHashTable< K, T, H, E >

The ChHashTable class. This container is most useful when you need a quasi-constant-time retrieval of a value, given its key. In fact, this container stores 'pairs' of values-keys, where keys should be unique (an example: a key could be the credit card number, and the value could be a structure with name, age and address of the credit card owner). When the hash table is filled too much, the performance get worse. Also, when you fill it beyond the initial suggested number of bins, an automatic table resizing (with rehashing) is performed. This may be a time-consuming cpu operation! So, choose initial size as close as possible to the maximum number of elements that you foresee to insert, plus some more space (es: +50%) to avoid performance degradation.

K = key type T = value type H = hash function object with the profile 'unsigned H(const K&)' E = equal function object with the profile 'bool E(const K&, const K&)' defaults to equal_to which in turn calls '=='

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Constructor & Destructor Documentation

template<typename K , typename T , class H , class E >

chrono::ChHashTable< K, T, H, E >::ChHashTable

(

unsigned

bins = 0

)

Construct a ChHashTable table with specified number of bins. The default 0 bins means leave it to the table to decide. Specifying 0 bins also enables auto-rehashing, otherwise auto-rehashing defaults off

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Member Function Documentation

template<typename K , typename T , class H , class E >

ChHashTable< K, T, H, E >::const_iterator chrono::ChHashTable< K, T, H, E >::begin

(

void

)

const

Iterators allow the hash table to be traversed Iterators remain valid unless an item is removed or unless a rehash happens

template<typename K , typename T , class H , class E >

bool chrono::ChHashTable< K, T, H, E >::empty

(

void

)

const

Test for an empty table and for the size of a table Efficient because the size is stored separately from the table contents

template<typename K, typename T , class H , class E >

ChHashTable< K, T, H, E >::const_iterator chrono::ChHashTable< K, T, H, E >::find

(

const K &

key

)

const

Find a key and return an iterator to it The iterator is like a pointer to a pair<const K,T> end() is returned if the find fails

template<typename K , typename T , class H , class E >

float chrono::ChHashTable< K, T, H, E >::loading

(

void

)

const

Test the loading ratio, which is the size divided by the number of bins. Use this if you are doing your own rehashing.

template<typename K, typename T , class H , class E >

const T & chrono::ChHashTable< K, T, H, E >::operator[]

(

const K &

key

)

const

Returns the data corresponding to the key the const version is used by the compiler on const hashes and cannot change the hash, so find failure causes an exception the non-const version is used by the compiler on non-const hashes and is like map - it creates a new key/data pair if find fails

template<typename K , typename T , class H , class E >

void chrono::ChHashTable< K, T, H, E >::rehash

(

unsigned

bins = 0

)

Force a rehash now Default of 0 means implement built-in size calculation for rehashing (recommended - it doubles the number of bins)