gum::HashFuncSmallCastKey< Key > Class Template Reference

Generic hash functions for keys castable as Size and whose size is strictly smaller than that of Size. More...

#include <agrum/core/hashFunc.h>

Inheritance diagram for gum::HashFuncSmallCastKey< Key >:

Collaboration diagram for gum::HashFuncSmallCastKey< Key >:

Public Member Functions
	HashFuncSmallCastKey ()
	Class constructor. More...
virtual Size	operator() (const Key &key) const override final
	Computes the hashed value of a key. More...
void	resize (const Size new_size)
	Update the hash function to take into account a resize of the hash table. More...
Size	size () const
	Returns the hash table size as known by the hash function. More...

Static Public Member Functions
static Size	castToSize (const Key &key)
	Returns the value of a key as a Size. More...

Protected Attributes
Size	_hash_size {Size(0)}
	The size of the hash table. More...
unsigned int	_hash_log2_size {0}
	Log of the number of slots of the hash table in base 2. More...
Size	_hash_mask {Size(0)}
	performing y = x & _hash_mask guarantees that y is a slot index of the hash table More...
unsigned int	_right_shift {0}
	performing y = x >> _right_shift guarantees that y is a slot index of the hash table More...

Static Protected Attributes
static constexpr Size	_small_key_mask
	An additional mask to ensure that keys with fewer bits than Size are cast correctly. More...

Detailed Description

template<typename Key>
class gum::HashFuncSmallCastKey< Key >

Generic hash functions for keys castable as Size and whose size is strictly smaller than that of Size.

Template Parameters

Key	The type hashed by this hash function.

Definition at line 274 of file hashFunc.h.

Constructor & Destructor Documentation

HashFuncSmallCastKey()

template<typename Key >

gum::HashFuncSmallCastKey< Key >::HashFuncSmallCastKey

(

)

Class constructor.

Member Function Documentation

castToSize()

template<typename Key >

static Size gum::HashFuncSmallCastKey< Key >::castToSize ( const Key &  key )

static

Returns the value of a key as a Size.

Parameters

key	The value to return as a Size.

Returns

Returns the value of a key as a Size.

operator()()

template<typename Key >

virtual Size gum::HashFuncSmallCastKey< Key >::operator() ( const Key &  key ) const

finaloverridevirtual

Computes the hashed value of a key.

Parameters

key	The key to compute the hashed value.

Returns

Returns the hashed value of a key.

Implements gum::HashFuncBase< Key >.

resize()

template<typename Key>

void gum::HashFuncBase< Key >::resize ( const Size  new_size )

inherited

Update the hash function to take into account a resize of the hash table.

When the user wishes to resize the gum::HashTable so that the array is of size s, the gum::HashTable resizes itself to the smallest power of 2 greater than or equal to s. This new size is computed by function gum::HashFuncBase::resize(gum::Size). Hence, s should be the size of the array of lists, not the number of elements stored into the gum::HashTable.

Parameters

new_size

The hashtable's size wished by the user. Actually, a hashtable of size n is an array of n lists.

Exceptions

SizeError

Raised if s is too small.

size()

template<typename Key>

Size gum::HashFuncBase< Key >::size ( ) const

inherited

Returns the hash table size as known by the hash function.

Returns

Returns the size of the hash table, i.e., the number of slots (lists) it contains.

Member Data Documentation

_hash_log2_size

template<typename Key>

unsigned int gum::HashFuncBase< Key >::_hash_log2_size {0}

protectedinherited

Log of the number of slots of the hash table in base 2.

Definition at line 204 of file hashFunc.h.

_hash_mask

template<typename Key>

Size gum::HashFuncBase< Key >::_hash_mask {Size(0)}

protectedinherited

performing y = x & _hash_mask guarantees that y is a slot index of the hash table

To transform a Size x into a slot index of the hash table, you can either use x & _hash_mask or x >> _right_shift depending on whether you want to exploit the least significant bits of x (&) or the most significant one (>>).

Definition at line 215 of file hashFunc.h.

_hash_size

template<typename Key>

Size gum::HashFuncBase< Key >::_hash_size {Size(0)}

protectedinherited

The size of the hash table.

Definition at line 201 of file hashFunc.h.

_right_shift

template<typename Key>

unsigned int gum::HashFuncBase< Key >::_right_shift {0}

protectedinherited

performing y = x >> _right_shift guarantees that y is a slot index of the hash table

To transform a Size x into a slot index of the hash table, you can either use x & _hash_mask or x >> _right_shift depending on whether you want to exploit the least significant bits of x (&) or the most significant one (>>).

Definition at line 226 of file hashFunc.h.

_small_key_mask

template<typename Key >

constexpr Size gum::HashFuncSmallCastKey< Key >::_small_key_mask

staticprotected

Initial value:

{(Size(1) << (8 * sizeof(Key)))
                                          - Size(1)}

An additional mask to ensure that keys with fewer bits than Size are cast correctly.

Definition at line 300 of file hashFunc.h.

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The documentation for this class was generated from the following file:

• agrum/core/hashFunc.h