Hash table implementation with separate chaining. More...

#include <hashTable.h>

Collaboration diagram for original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >:

Classes
class	hashNode
	Internal node type for hash table storage. More...

class	Iterator
	Forward iterator for hashTable. More...

Public Types
using	rebind_alloc_node = ALLOC::template rebind_alloc< hashNode >
	Rebound allocator type for node storage.

using	rebind_alloc_pointer = ALLOC::template rebind_alloc< hashNode * >
	Rebound allocator type for pointer storage.

using	buckets_type = vector< hashNode *, rebind_alloc_pointer >
	Type representing the hash table buckets container.

Public Member Functions
buckets_type	bucketsCopy (const buckets_type &old_buckets) const
	Creates a deep copy of the hash table's bucket array.

hashNode *	createNode (const K_TYPE &key=K_TYPE{}, const V_TYPE &value=V_TYPE{}, hashNode *next=nullptr) const
	Creates a new hash node.

void	destroyNode (hashNode *node) noexcept
	Destroys a hash node.

u_integer	getHashCode (const K_TYPE &key) const
	Computes hash code for a key.

u_integer	getBucketCount () const
	Gets current number of buckets.

hashNode *	getBucket (const K_TYPE &key) const
	Gets bucket head for a key.

floating	loadFactor () const
	Calculates current load factor.

u_integer	getNextSize () const
	Gets next appropriate bucket size for expansion.

u_integer	getPrevSize () const
	Gets previous appropriate bucket size for shrinking.

void	rehash (u_integer new_bucket_count)
	Rehashes table to new bucket count.

void	adjust ()
	Adjusts table size based on load factor.

	hashTable (HASH hash=HASH{})
	Constructs empty hashTable.

hashNode *	find (const K_TYPE &key) const
	Finds node for given key.

bool	modify (const K_TYPE &key, const V_TYPE &value)
	Modifies value for existing key.

bool	insert (const K_TYPE &key, const V_TYPE &value)
	Inserts new key-value pair.

bool	erase (const K_TYPE &key)
	Removes key-value pair.

virtual	~hashTable ()
	Destroys hashTable.

Public Attributes
u_integer	size_

buckets_type	buckets

HASH	hash_

rebind_alloc_node	rebind_alloc {}

Static Public Attributes
static constexpr floating	LOAD_FACTOR_MIN = 0.25
	Minimum load factor before shrinking.

static constexpr floating	LOAD_FACTOR_MAX = 0.75
	Maximum load factor before expanding.

static constexpr u_integer	BUCKETS_SIZES_COUNT = 30
	Size of BUCKETS_SIZES BUCKETS_SIZES.

static constexpr u_integer	BUCKETS_SIZES []
	Predefined bucket sizes for hash table resizing.

Detailed Description

template<typename K_TYPE, typename V_TYPE, typename ALLOC = allocator<K_TYPE>, typename HASH = hash<K_TYPE>>
class original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >

Hash table implementation with separate chaining.

Template Parameters

K_TYPE	Key type (must be hashable)
V_TYPE	Value type
ALLOC	Allocator type (default: allocator<K_TYPE>)
HASH	Hash function type (default: hash<K_TYPE>)

This class provides a generic hash table implementation that serves as the base for hash-based containers. It implements:

Key-value pair storage
Dynamic resizing
Basic hash table operations

Performance Characteristics:

Insertion: Average O(1), Worst O(n)
Lookup: Average O(1), Worst O(n)
Deletion: Average O(1), Worst O(n)

The implementation guarantees:

Unique keys (no duplicates)
Automatic resizing when load factor thresholds are crossed
Exception safety (basic guarantee)

Constructor & Destructor Documentation

◆ hashTable()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::hashTable ( HASH hash = HASH{} )

explicit

Constructs empty hashTable.

Parameters

hash	Hash function to use

◆ ~hashTable()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::~hashTable ( )

virtual

Destroys hashTable.

Cleans up all nodes and buckets

Member Function Documentation

◆ adjust()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

void original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::adjust ( )

Adjusts table size based on load factor.

Checks current load factor and resizes if:

loadFactor() >= LOAD_FACTOR_MAX: expands table
loadFactor() <= LOAD_FACTOR_MIN: shrinks table

◆ bucketsCopy()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::buckets_type original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::bucketsCopy ( const buckets_type & old_buckets ) const

Creates a deep copy of the hash table's bucket array.

Parameters

old_buckets The original old_buckets array to copy

Returns: A new old_buckets array with cloned nodes

This function performs a deep copy of the entire old_buckets array used by the hash table, including the internal linked list in each bucket (used for separate chaining).

Copying strategy:

For each bucket index, traverse the linked list of hash nodes
Use createNode() to allocate a new node for each entry
Preserve the order of elements within each bucket's chain

This method is typically used in:

Copy constructors
Copy assignment operators

The function ensures that:

The original and copied hash tables do not share memory
All keys and values are copied correctly
Iterator validity is preserved for the new structure

Note: This function assumes the original old_buckets are well-formed (no cycles).; Uses allocator rebound to allocate memory for the new nodes.

◆ createNode()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::hashNode * original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::createNode	(	const K_TYPE &	key = `K_TYPE{}`,
		const V_TYPE &	value = `V_TYPE{}`,
		hashNode *	next = `nullptr`
	)		const

Creates a new hash node.

Parameters

key	Key for new node
value	Value for new node
next	Next node in chain

Returns: Pointer to newly created node

Note: Uses the rebound allocator for memory management

◆ destroyNode()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

void original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::destroyNode ( hashNode * node )

noexcept

Destroys a hash node.

Parameters

node	Node to destroy

Note: Safely handles nullptr and uses rebound allocator

◆ erase()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

bool original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::erase ( const K_TYPE & key )

Removes key-value pair.

Parameters

key	Key to remove

Returns: true if key existed and was removed

Note: Automatically adjusts table size if needed

◆ find()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::hashNode * original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::find ( const K_TYPE & key ) const

Finds node for given key.

Parameters

key	Key to search for

Returns: Pointer to node if found, nullptr otherwise

◆ getBucket()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::hashNode * original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::getBucket ( const K_TYPE & key ) const

Gets bucket head for a key.

Parameters

key	Key to lookup

Returns: Pointer to first node in bucket's chain

◆ getBucketCount()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::u_integer original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::getBucketCount ( ) const

Gets current number of buckets.

Returns: Current bucket count

◆ getHashCode()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::u_integer original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::getHashCode ( const K_TYPE & key ) const

Computes hash code for a key.

Parameters

key	Key to hash

Returns: Computed bucket index

◆ getNextSize()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::u_integer original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::getNextSize ( ) const

Gets next appropriate bucket size for expansion.

Returns: Next larger bucket size from predefined primes

Exceptions

outOfBoundError if already at maximum size

◆ getPrevSize()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::u_integer original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::getPrevSize ( ) const

Gets previous appropriate bucket size for shrinking.

Returns: Next smaller bucket size from predefined primes

◆ insert()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

bool original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::insert	(	const K_TYPE &	key,
		const V_TYPE &	value
	)

Inserts new key-value pair.

Parameters

key	Key to insert
value	Value to associate

Returns: true if inserted, false if key already existed

Note: Automatically adjusts table size if needed

◆ loadFactor()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

original::floating original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::loadFactor ( ) const

Calculates current load factor.

Returns: Current elements/buckets ratio

◆ modify()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

bool original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::modify	(	const K_TYPE &	key,
		const V_TYPE &	value
	)

Modifies value for existing key.

Parameters

key	Key to modify
value	New value

Returns: true if key existed and was modified

◆ rehash()

template<typename K_TYPE , typename V_TYPE , typename ALLOC , typename HASH >

void original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::rehash ( u_integer new_bucket_count )

Rehashes table to new bucket count.

Parameters

new_bucket_count New number of buckets

Rebuilds the hash table with new bucket count:

Allocates new buckets vector
Rehashes all elements
Maintains element order within buckets
Note
Invalidates all iterators

Member Data Documentation

◆ BUCKETS_SIZES

template<typename K_TYPE , typename V_TYPE , typename ALLOC = allocator<K_TYPE>, typename HASH = hash<K_TYPE>>

constexpr u_integer original::hashTable< K_TYPE, V_TYPE, ALLOC, HASH >::BUCKETS_SIZES[]

staticconstexpr

Initial value:

= {
                17,          29,          53,          97,          193,
                389,         769,         1543,        3079,        6151,
                12289,       24593,       49157,       98317,       196613,
 
                393241,      786433,      1572869,     3145739,     6291469,
                12582917,    25165843,    50331653,    100663319,   201326611,
 
                402653189,   805306457,   1610612741,  3221225473,  4294967291
        }

Predefined bucket sizes for hash table resizing.

An array of prime numbers carefully selected for hash table bucket sizes. These primes are used during table resizing to maintain optimal performance characteristics.

Key Properties:

All values are prime numbers to reduce hash collisions
Each size is approximately double the previous (with some variance)
Covers a wide range from small to very large tables
Specifically chosen to avoid common modulo patterns

Selection Criteria:

Primes spaced roughly exponentially (growth factor ~1.8-2.2)
Avoid primes close to powers of 2 to prevent clustering
Sufficient gaps between sizes to justify resize operations
Includes sizes suitable for both small and large datasets

Performance Impact:

Larger sizes reduce collisions but increase memory usage
Smaller sizes conserve memory but may increase collisions
The growth factor balances between resize frequency and memory overhead

The sequence continues until reaching sizes suitable for maximum practical in-memory hash tables (over 100 million buckets).

Note: The actual resize operation only occurs when the load factor exceeds thresholds, not necessarily at every size transition.

See also: LOAD_FACTOR_MIN; LOAD_FACTOR_MAX

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

src/core/hashTable.h

Classes

Public Types

Public Member Functions

Public Attributes

Static Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ hashTable()

◆ ~hashTable()

Member Function Documentation

◆ adjust()

◆ bucketsCopy()

◆ createNode()

◆ destroyNode()

◆ erase()

◆ find()

◆ getBucket()

◆ getBucketCount()

◆ getHashCode()

◆ getNextSize()

◆ getPrevSize()

◆ insert()

◆ loadFactor()

◆ modify()

◆ rehash()

Member Data Documentation

◆ BUCKETS_SIZES