A C++ template library for embedded applications
MIT licensed
Designed and
maintained by
John Wellbelove

unordered_map / unordered_multimap

A fixed capacity map.
Uses std::less as the default key comparison method.
STL equivalent: std::unordered_map / std::unordered_multimap

This page just describes etl::unordered_map.

template <typename TKey,
          typename TValue,
          size_t   MAX_SIZE,
          size_t   MAX_BUCKETS = MAX_SIZE,
          typename THash = etl::hash<TKey>,
          typename TKeyEqual = etl::equal_to<TKey>>
class unordered_map

Inherits from iunordered_map<TKey, TValue, THash, TKeyEqual>
etl::iunordered_map may be used as a size independent pointer or reference type for any etl::unordered_map
instance.
____________________________________________________________________________________________________
Template deduction guides
C++17 and above

template <typename... TPairs>
etl::unordered_map(TPairs...)

Example
etl::unordered_map data{ etl::pair{0, 1}, etl::pair{2, 3}, etl::pair{4, 5}, etl::pair{6, 7} };
Defines data as an map of int/int pairs, of length 4, containing the supplied data.
____________________________________________________________________________________________________
Make template
C++11 and above
template <typename TKey,
          typename TValue,
          typename THash       = etl::hash<TKey>,
          typename TKeyEqual   = etl::equal_to<TKey>
          typename... TPairs>
constexpr auto make_unordered_map(TValues&&... values)

Example
auto data = etl::make_unordered_map<int, int>(etl::pair{0, 1}, etl::pair{2, 3},
                                              etl::pair{4, 5}, etl::pair{6, 7});
____________________________________________________________________________________________________
Member types

value_type              pair<const TKey, T>
key_type                The type of the key value
mapped_type             The type of the mapped value
hasher                  The type used to hash the key
key_equal               The functor used to compare keys
reference               A reference to a value_type
const_reference         A reference to a const value_type
pointer                 A pointer to a value_type
const_pointer           A pointer to a const value_type
size_type               The type used for size information
iterator                Random access iterator
const_iterator          Constant random access iterator
local_iterator          Iterator to a bucket
local_const_iterator    A const iterator to a bucket
____________________________________________________________________________________________________
Constructor

unordered_map()
Default constructor

unordered_map(const unordered_map& other)
Copy constructor

template <typename TIterator>
unordered_map(TIterator begin, TIterator end);
Construct from a range
____________________________________________________________________________________________________
Element access

mapped_type& at(key_parameter_t key)
const mapped_type& at(key_parameter_t key) const
Returns a reference or const reference to the indexed element.
Emits an etl::map_out_of_range if the key is not in the table. If assert or exceptions are not enabled then undefined
behaviour occurs.
____________________________________________________________________________________________________
mapped_type& operator[](key_parameter_t key)
Returns a reference to the indexed element.
If the key does not exist then one is created using the default constructor. If the map is full then emits an
etl::map_full. If asserts or exceptions are not enabled then undefined behaviour occurs.
____________________________________________________________________________________________________
iterator find(key_parameter_t key);
const_iterator find (key_parameter_t key) const;
Searches the container for an element with a key equivalent to key and returns an iterator to it if found, otherwise it
returns an iterator to etl::map::end()
____________________________________________________________________________________________________
size_type count(key_parameter_t key) const;
Count elements with a specific key.
Searches the container for elements with a key equivalent to key and returns the number of matches
____________________________________________________________________________________________________
iterator lower_bound(key_parameter_t key);
const_iterator lower_bound(key_parameter_t key) const;
Returns the iterator to the lower bound.
Returns an iterator pointing to the first element in the container whose key is not considered to go before key (i.e.,
either it is equivalent or goes after).
____________________________________________________________________________________________________
iterator upper_bound(key_parameter_t key);
const_iterator upper_bound(key_parameter_t key) const;
Return the iterator to the upper bound.
Returns an iterator pointing to the first element in the container whose key is considered to go after key.
____________________________________________________________________________________________________
pair<iterator, iterator> equal_range(key_parameter_t key);
pair<const_iterator, const_iterator> equal_range(key_parameter_t key) const;
Get the range of equal elements.
Returns the bounds of a range that includes all the elements in the container which have a key equivalent to key.
____________________________________________________________________________________________________
Iterators

iterator begin()
const_iterator begin() const
const_iterator cbegin() const
Returns an iterator to the beginning of the map.
____________________________________________________________________________________________________
iterator end()
const_iterator end() const
const_iterator cend() const
Returns an iterator to the end of the map.
____________________________________________________________________________________________________
Capacity

bool empty() const
Returns true if the size of the map is zero, otherwise false.
____________________________________________________________________________________________________
bool full() const
Returns true if the size of the map is SIZE, otherwise false.
____________________________________________________________________________________________________
size_t size() const
Returns the size of the map.
____________________________________________________________________________________________________
size_t max_size() const
Returns the maximum possible size of the map.
____________________________________________________________________________________________________
size_t available() const
Returns the remaining available capacity in the map.
____________________________________________________________________________________________________
size_type get_bucket_index(key_parameter_t key) const
Returns the bucket index for the key.
____________________________________________________________________________________________________
size_type bucket_size(key_parameter_t key) const
Returns the size of the bucket key.
____________________________________________________________________________________________________
size_type max_bucket_count() const
Returns the maximum number of the buckets the container can hold.
____________________________________________________________________________________________________
float load_factor() const
Returns the load factor = size / bucket_count
____________________________________________________________________________________________________
hasher hash_function() const
Returns the function that hashes the keys.
____________________________________________________________________________________________________
key_equal key_eq() const
Returns the function that compares the keys.
____________________________________________________________________________________________________
Modifiers

template <typename TIterator>
void assign(TIterator first, TIterator last)
Assigns elements from a range.
Clears the container before assigning.
____________________________________________________________________________________________________
pair<iterator, bool> insert(const value_type& key_value_pair)
iterator insert(const_iterator, const value_type& key_value_pair)
____________
template <template TIterator>
void insert(TIterator first, TIterator last)
Inserts values in to the map.
If the map is full then emits an etl::unordered_map_full error. If asserts or exceptions are not enabled then
undefined behaviour occurs.
____________________________________________________________________________________________________
size_t erase(key_parameter_t key)
____________
iterator erase(const_iterator ielement)
____________
iterator erase(const_iterator first, const_iterator last)
Erases values in the map.
Iterator are not checked for validity.
____________________________________________________________________________________________________
void clear();
Clears the map to a size of zero.
____________________________________________________________________________________________________
Non-member functions

==  true if the contents of the maps are equal, otherwise false.
!=  true if the contents of the maps are not equal, otherwise false.
unordered_map.h / unordered_multimap.h