juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse > Class Template Reference

Detailed Description

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>
class juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >

Holds a set of mappings between some key/value pairs.

The types of the key and value objects are set as template parameters. You can also specify a class to supply a hash function that converts a key value into an hashed integer. This class must have the form:

struct MyHashGenerator
{
    int generateHash (MyKeyType key, int upperLimit) const
    {
        // The function must return a value 0 <= x < upperLimit
        return someFunctionOfMyKeyType (key) % upperLimit;
    }
};

Like the Array class, the key and value types are expected to be copy-by-value types, so if you define them to be pointer types, this class won't delete the objects that they point to.

If you don't supply a class for the HashFunctionType template parameter, the default one provides some simple mappings for strings and ints.

HashMap<int, String> hash;
hash.set (1, "item1");
hash.set (2, "item2");
 
DBG (hash [1]); // prints "item1"
DBG (hash [2]); // prints "item2"
 
// This iterates the map, printing all of its key -> value pairs..
for (HashMap<int, String>::Iterator i (hash); i.next();)
    DBG (i.getKey() << " -> " << i.getValue());

Template Parameters

HashFunctionType

The class of hash function, which must be copy-constructible.

See also

CriticalSection, DefaultHashFunctions, NamedValueSet, SortedSet

Classes
struct	Iterator
	Iterates over the items in a HashMap. More...

Public Types
using	ScopedLockType = typename TypeOfCriticalSectionToUse::ScopedLockType
	Returns the type of scoped lock to use for locking this array.

Public Member Functions
	HashMap (int numberOfSlots=defaultHashTableSize, HashFunctionType hashFunction=HashFunctionType())
	Creates an empty hash-map.
	~HashMap ()
	Destructor.
void	clear ()
	Removes all values from the map.
int	size () const noexcept
	Returns the current number of items in the map.
ValueType	operator[] (KeyTypeParameter keyToLookFor) const
	Returns the value corresponding to a given key.
ValueType &	getReference (KeyTypeParameter keyToLookFor)
	Returns a reference to the value corresponding to a given key.
bool	contains (KeyTypeParameter keyToLookFor) const
	Returns true if the map contains an item with the specified key.
bool	containsValue (ValueTypeParameter valueToLookFor) const
	Returns true if the hash contains at least one occurrence of a given value.
void	set (KeyTypeParameter newKey, ValueTypeParameter newValue)
	Adds or replaces an element in the hash-map.
void	remove (KeyTypeParameter keyToRemove)
	Removes an item with the given key.
void	removeValue (ValueTypeParameter valueToRemove)
	Removes all items with the given value.
void	remapTable (int newNumberOfSlots)
	Remaps the hash-map to use a different number of slots for its hash function.
int	getNumSlots () const noexcept
	Returns the number of slots which are available for hashing.
template<class OtherHashMapType>
void	swapWith (OtherHashMapType &otherHashMap) noexcept
	Efficiently swaps the contents of two hash-maps.
const TypeOfCriticalSectionToUse &	getLock () const noexcept
	Returns the CriticalSection that locks this structure.
Iterator	begin () const noexcept
	Returns a start iterator for the values in this tree.
Iterator	end () const noexcept
	Returns an end iterator for the values in this tree.

Member Typedef Documentation

ScopedLockType

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

using juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::ScopedLockType = typename TypeOfCriticalSectionToUse::ScopedLockType

Returns the type of scoped lock to use for locking this array.

Constructors and Destructors

HashMap()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::HashMap ( int numberOfSlots = defaultHashTableSize, HashFunctionType hashFunction = HashFunctionType() )

explicit

Creates an empty hash-map.

Parameters

numberOfSlots	Specifies the number of hash entries the map will use. This will be the "upperLimit" parameter that is passed to your generateHash() function. The number of hash slots will grow automatically if necessary, or it can be remapped manually using remapTable().
hashFunction	An instance of HashFunctionType, which will be copied and stored to use with the HashMap. This parameter can be omitted if HashFunctionType has a default constructor.

Referenced by juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::Iterator::Iterator().

~HashMap()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::~HashMap

(

)

Destructor.

References clear().

Member Functions

clear()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::clear

(

)

Removes all values from the map.

Note that this will clear the content, but won't affect the number of slots (see remapTable and getNumSlots).

References getLock().

Referenced by ~HashMap().

size()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

int juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::size ( ) const

noexcept

Returns the current number of items in the map.

operator[]()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

ValueType juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::operator[]

(

KeyTypeParameter

keyToLookFor

)

const

Returns the value corresponding to a given key.

If the map doesn't contain the key, a default instance of the value type is returned.

Parameters

keyToLookFor

the key of the item being requested

References getLock().

getReference()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

ValueType & juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::getReference

(

KeyTypeParameter

keyToLookFor

)

Returns a reference to the value corresponding to a given key.

If the map doesn't contain the key, a default instance of the value type is added to the map and a reference to this is returned.

Parameters

keyToLookFor

the key of the item being requested

References getLock(), getNumSlots(), and remapTable().

Referenced by set().

contains()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

bool juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::contains

(

KeyTypeParameter

keyToLookFor

)

const

Returns true if the map contains an item with the specified key.

References getLock().

containsValue()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

bool juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::containsValue

(

ValueTypeParameter

valueToLookFor

)

const

Returns true if the hash contains at least one occurrence of a given value.

References getLock(), and getNumSlots().

set()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::set	(	KeyTypeParameter	newKey,
		ValueTypeParameter	newValue )

Adds or replaces an element in the hash-map.

If there's already an item with the given key, this will replace its value. Otherwise, a new item will be added to the map.

References getReference().

remove()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::remove

(

KeyTypeParameter

keyToRemove

)

Removes an item with the given key.

References getLock(), and getNumSlots().

removeValue()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::removeValue

(

ValueTypeParameter

valueToRemove

)

Removes all items with the given value.

References getLock(), and getNumSlots().

remapTable()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::remapTable

(

int

newNumberOfSlots

)

Remaps the hash-map to use a different number of slots for its hash function.

Each slot corresponds to a single hash-code, and each one can contain multiple items.

See also

getNumSlots()

References getLock(), getNumSlots(), juce::Array< ElementType, TypeOfCriticalSectionToUse, minimumAllocatedSize >::getUnchecked(), juce::Array< ElementType, TypeOfCriticalSectionToUse, minimumAllocatedSize >::insertMultiple(), and juce::Array< ElementType, TypeOfCriticalSectionToUse, minimumAllocatedSize >::set().

Referenced by getReference().

getNumSlots()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

int juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::getNumSlots ( ) const

noexcept

Returns the number of slots which are available for hashing.

Each slot corresponds to a single hash-code, and each one can contain multiple items.

See also

getNumSlots()

Referenced by containsValue(), getReference(), remapTable(), remove(), and removeValue().

swapWith()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

template<class OtherHashMapType>

void juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::swapWith ( OtherHashMapType & otherHashMap )

noexcept

Efficiently swaps the contents of two hash-maps.

References getLock().

getLock()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

const TypeOfCriticalSectionToUse & juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::getLock ( ) const

noexcept

Returns the CriticalSection that locks this structure.

To lock, you can call getLock().enter() and getLock().exit(), or preferably use an object of ScopedLockType as an RAII lock for it.

Referenced by clear(), contains(), containsValue(), getReference(), operator[](), remapTable(), remove(), removeValue(), and swapWith().

begin()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

Iterator juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::begin ( ) const

noexcept

Returns a start iterator for the values in this tree.

References juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::Iterator::next().

end()

template<typename KeyType, typename ValueType, class HashFunctionType = DefaultHashFunctions, class TypeOfCriticalSectionToUse = DummyCriticalSection>

Iterator juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::end ( ) const

noexcept

Returns an end iterator for the values in this tree.

References juce::HashMap< KeyType, ValueType, HashFunctionType, TypeOfCriticalSectionToUse >::Iterator::resetToEnd().