small_multimap.md

sfl::small_multimap

Table of Contents

• Summary
• Template Parameters
• Public Member Types
• Public Member Classes
  • value_compare
• Public Data Members
  • static_capacity
• Public Member Functions
  • (constructor)
  • (destructor)
  • operator=
  • get_allocator
  • key_comp
  • value_comp
  • begin, cbegin
  • end, cend
  • rbegin, crbegin
  • rend, crend
  • empty
  • size
  • max_size
  • clear
  • emplace
  • emplace_hint
  • insert
  • insert_range
  • erase
  • swap
  • lower_bound
  • upper_bound
  • equal_range
  • find
  • count
  • contains
• Non-member Functions
  • operator==
  • operator!=
  • operator<
  • operator>
  • operator<=
  • operator>=
  • swap
  • erase_if

Summary

Defined in header sfl/small_multimap.hpp:

namespace sfl
{
    template < typename Key,
               typename T,
               std::size_t N,
               typename Compare = std::less<Key>,
               typename Allocator = std::allocator<std::pair<const Key, T>> >
    class small_multimap;
}

sfl::small_multimap is an associative container similar to std::multimap, but it internally holds a small amount of statically allocated memory to avoid dynamic memory management when the number of stored elements is small. Dynamic memory management is used when the number of elements exceeds N. This design provides a compact and cache-friendly representation optimized for small sizes.

The underlying storage is implemented as red-black tree.

The complexity of search, insert, and remove operations is O(log N).

References and pointers to elements are stable: insert and erase operations do not invalidate them unless the referenced element is erased.

Iterators to elements are bidirectional iterators, and they meet the requirements of LegacyBidirectionalIterator.

sfl::small_multimap meets the requirements of Container, AllocatorAwareContainer, ReversibleContainer, and AssociativeContainer.

Template Parameters

1. typename Key
   

   Key type.

2. typename T
   

   Value type.

3. std::size_t N
   

   Size of the internal statically allocated array, i.e. the maximal number of elements that can fit into this array.

   This parameter can be zero.

4. typename Compare
   

   Ordering function for keys.

5. typename Allocator
   

   Allocator used for memory allocation/deallocation and construction/destruction of elements.

   This type must meet the requirements of Allocator.

   The program is ill-formed if Allocator::value_type is not the same as std::pair<const Key, T>.

Public Member Types

Member Type	Definition
allocator_type	Allocator
key_type	Key
mapped_type	T
value_type	std::pair<const Key, T>
size_type	Unsigned integer type
difference_type	Signed integer type
key_compare	Compare
reference	value_type&
const_reference	const value_type&
pointer	Pointer to value_type
const_pointer	Pointer to const value_type
iterator	LegacyBidirectionalIterator to value_type
const_iterator	LegacyBidirectionalIterator to const value_type
reverse_iterator	Reverse LegacyBidirectionalIterator to value_type
const_reverse_iterator	Reverse LegacyBidirectionalIterator to const value_type

Public Member Classes

value_compare

class value_compare
{
public:
    bool operator()(const value_type& x, const value_type& y) const;
};

Public Data Members

static_capacity

static constexpr size_type static_capacity = N;

Public Member Functions

(constructor)

1. small_multimap() noexcept(
       std::is_nothrow_default_constructible<Allocator>::value &&
       std::is_nothrow_default_constructible<Compare>::value
   );
   

2. explicit small_multimap(const Compare& comp) noexcept(
       std::is_nothrow_default_constructible<Allocator>::value &&
       std::is_nothrow_copy_constructible<Compare>::value
   );
   

3. explicit small_multimap(const Allocator& alloc) noexcept(
       std::is_nothrow_copy_constructible<Allocator>::value &&
       std::is_nothrow_default_constructible<Compare>::value
   );
   

4. explicit small_multimap(const Compare& comp, const Allocator& alloc) noexcept(
       std::is_nothrow_copy_constructible<Allocator>::value &&
       std::is_nothrow_copy_constructible<Compare>::value
   );
   

   Effects: Constructs an empty container.

   Complexity: Constant.

   
   
   

5. template <typename InputIt>
   small_multimap(InputIt first, InputIt last);
   

6. template <typename InputIt>
   small_multimap(InputIt first, InputIt last, const Compare& comp);
   

7. template <typename InputIt>
   small_multimap(InputIt first, InputIt last, const Allocator& alloc);
   

8. template <typename InputIt>
   small_multimap(InputIt first, InputIt last, const Compare& comp, const Allocator& alloc);
   

   Effects: Constructs the container with the contents of the range [first, last).

   Note: These overloads participate in overload resolution only if InputIt satisfies requirements of LegacyInputIterator.

   
   
   

9. small_multimap(std::initializer_list<value_type> ilist);
   

10. small_multimap(std::initializer_list<value_type> ilist, const Compare& comp);
    

11. small_multimap(std::initializer_list<value_type> ilist, const Allocator& alloc);
    

12. small_multimap(std::initializer_list<value_type> ilist, const Compare& comp, const Allocator& alloc);
    

    Effects: Constructs the container with the contents of the initializer list ilist.

    
    
    

13. small_multimap(const small_multimap& other);
    

14. small_multimap(const small_multimap& other, const Allocator& alloc);
    

    Effects: Copy constructor. Constructs the container with the copy of the contents of other.

    
    
    

15. small_multimap(small_multimap&& other);
    

16. small_multimap(small_multimap&& other, const Allocator& alloc);
    

    Effects: Move constructor. Constructs the container with the contents of other using move semantics.

    other is not guaranteed to be empty after the move.

    other is in a valid but unspecified state after the move.

    
    
    

17. template <typename Range>
    small_multimap(sfl::from_range_t, Range&& range);
    

18. template <typename Range>
    small_multimap(sfl::from_range_t, Range&& range, const Compare& comp);
    

19. template <typename Range>
    small_multimap(sfl::from_range_t, Range&& range, const Allocator& alloc);
    

20. template <typename Range>
    small_multimap(sfl::from_range_t, Range&& range, const Compare& comp, const Allocator& alloc);
    

    Effects: Constructs the container with the contents of range.

    Note: It is available in C++11. In C++20 are used proper C++20 range concepts.

    
    
    

(destructor)

1. ~small_multimap();
   

   Effects: Destructs the container. The destructors of the elements are called and the used storage is deallocated.

   Complexity: Linear in size().

   
   
   

operator=

1. small_multimap& operator=(const small_multimap& other);
   

   Effects: Copy assignment operator. Replaces the contents with a copy of the contents of other.

   Returns: *this().

   
   
   

2. small_multimap& operator=(small_multimap&& other);
   

   Effects: Move assignment operator. Replaces the contents with those of other using move semantics.

   other is not guaranteed to be empty after the move.

   other is in a valid but unspecified state after the move.

   Returns: *this().

   
   
   

3. small_multimap& operator=(std::initializer_list<value_type> ilist);
   

   Effects: Replaces the contents with those identified by initializer list ilist.

   Returns: *this().

   
   
   

get_allocator

1. allocator_type get_allocator() const noexcept;
   

   Effects: Returns the allocator associated with the container.

   Complexity: Constant.

   
   
   

key_comp

1. key_compare key_comp() const;
   

   Effects: Returns the function object that compares the keys, which is a copy of this container's constructor argument comp.

   Complexity: Constant.

   
   
   

value_comp

1. value_compare value_comp() const;
   

   Effects: Returns a function object that compares objects of type value_type.

   Complexity: Constant.

   
   
   

begin, cbegin

1. iterator begin() noexcept;
   

2. const_iterator begin() const noexcept;
   

3. const_iterator cbegin() const noexcept;
   

   Effects: Returns an iterator to the first element of the container. If the container is empty, the returned iterator will be equal to end().

   Complexity: Constant.

   
   
   

end, cend

1. iterator end() noexcept;
   

2. const_iterator end() const noexcept;
   

3. const_iterator cend() const noexcept;
   

   Effects: Returns an iterator to the element following the last element of the container. This element acts as a placeholder; attempting to access it results in undefined behavior.

   Complexity: Constant.

   
   
   

rbegin, crbegin

1. reverse_iterator rbegin() noexcept;
   

2. const_reverse_iterator rbegin() const noexcept;
   

3. const_reverse_iterator crbegin() const noexcept;
   

   Effects: Returns a reverse iterator to the first element of the reversed container. It corresponds to the last element of the non-reversed container. If the container is empty, the returned iterator is equal to rend().

   Complexity: Constant.

   
   
   

rend, crend

1. reverse_iterator rend() noexcept;
   

2. const_reverse_iterator rend() const noexcept;
   

3. const_reverse_iterator crend() const noexcept;
   

   Effects: Returns a reverse iterator to the element following the last element of the reversed container. It corresponds to the element preceding the first element of the non-reversed container. This element acts as a placeholder, attempting to access it results in undefined behavior.

   Complexity: Constant.

   
   
   

empty

1. bool empty() const noexcept;
   

   Effects: Returns true if the container has no elements, i.e. whether begin() == end().

   Complexity: Constant.

   
   
   

size

1. size_type size() const noexcept;
   

   Effects: Returns the number of elements in the container, i.e. std::distance(begin(), end()).

   Complexity: Constant.

   
   
   

max_size

1. size_type max_size() const noexcept;
   

   Effects: Returns the maximum number of elements the container is able to hold, i.e. std::distance(begin(), end()) for the largest container.

   Complexity: Constant.

   
   
   

clear

1. void clear() noexcept;
   

   Effects: Erases all elements from the container. After this call, size() returns zero and capacity() remains unchanged.

   Complexity: Linear in size().

   
   
   

emplace

1. template <typename... Args>
   iterator emplace(Args&&... args);
   

   Effects: Inserts a new element into the container.

   New element is constructed as value_type(std::forward<Args>(args)...).

   Returns: Iterator to the inserted element.

   
   
   

emplace_hint

1. template <typename... Args>
   iterator emplace_hint(const_iterator hint, Args&&... args);
   

   Effects: Inserts a new element into the container.

   New element is constructed as value_type(std::forward<Args>(args)...).

   Iterator hint is used as a suggestion where to start to search insert position.

   Returns: Iterator to the inserted element.

   
   
   

insert

1. iterator insert(const value_type& value);
   

   Effects: Inserts copy of value.

   Returns: Iterator to the inserted element.

   
   
   

2. iterator insert(value_type&& value);
   

   Effects: Inserts value using move semantics.

   Returns: Iterator to the inserted element.

   
   
   

3. template <typename P>
   iterator insert(P&& value);
   

   Effects: Inserts a new element into the container.

   New element is constructed as value_type(std::forward<P>(value)).

   Note: This overload participates in overload resolution only if std::is_constructible<value_type, P&&>::value is true.

   Returns: Iterator to the inserted element.

   
   
   

4. iterator insert(const_iterator hint, const value_type& value);
   

   Effects: Inserts copy of value.

   Iterator hint is used as a suggestion where to start to search insert position.

   Returns: Iterator to the inserted element.

   
   
   

5. iterator insert(const_iterator hint, value_type&& value);
   

   Effects: Inserts value using move semantics.

   Iterator hint is used as a suggestion where to start to search insert position.

   Returns: Iterator to the inserted element.

   
   
   

6. template <typename P>
   iterator insert(const_iterator hint, P&& value);
   

   Effects: Inserts a new element into the container.

   New element is constructed as value_type(std::forward<P>(value)).

   Iterator hint is used as a suggestion where to start to search insert position.

   Note: This overload participates in overload resolution only if std::is_constructible<value_type, P&&>::value is true.

   Returns: Iterator to the inserted element.

   
   
   

7. template <typename InputIt>
   void insert(InputIt first, InputIt last);
   

   Effects: Inserts elements from range [first, last).

   The call to this function is equivalent to:

   while (first != last)
   {
       insert(*first);
       ++first;
   }
   

   Note: This overload participates in overload resolution only if InputIt satisfies requirements of LegacyInputIterator.

   
   
   

8. void insert(std::initializer_list<value_type> ilist);
   

   Effects: Inserts elements from initializer list ilist.

   The call to this function is equivalent to insert(ilist.begin(), ilist.end()).

   
   
   

insert_range

1. template <typename Range>
   void insert_range(Range&& range);
   

   Effects: Inserts elements from range.

   Note: It is available in C++11. In C++20 are used proper C++20 range concepts.

   
   
   

erase

1. iterator erase(iterator pos);
   

2. iterator erase(const_iterator pos);
   

   Effects: Removes the element at pos.

   Returns: Iterator following the last removed element.

   
   
   

3. iterator erase(const_iterator first, const_iterator last);
   

   Effects: Removes the elements in the range [first, last).

   Returns: Iterator following the last removed element.

   
   
   

4. size_type erase(const Key& key);
   

5. template <typename K>
   size_type erase(K&& x);
   

   Effects: Removes all elements with the key equivalent to key or x.

   Note: Overload (5) participates in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling this function without constructing an instance of Key.

   Returns: Number of elements removed.

   
   
   

swap

1. void swap(small_multimap& other);
   

   Effects: Exchanges the contents of the container with those of other.

   
   
   

lower_bound

1. iterator lower_bound(const Key& key);
   

2. const_iterator lower_bound(const Key& key) const;
   

3. template <typename K>
   iterator lower_bound(const K& x);
   

4. template <typename K>
   const_iterator lower_bound(const K& x) const;
   

   Effects: Returns an iterator pointing to the first element with key that compares not less than key or x. Returns end() if no such element is found.

   Note: Overloads (3) and (4) participate in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling these functions without constructing an instance of Key.

   Complexity: Logarithmic in size().

   
   
   

upper_bound

1. iterator upper_bound(const Key& key);
   

2. const_iterator upper_bound(const Key& key) const;
   

3. template <typename K>
   iterator upper_bound(const K& x);
   

4. template <typename K>
   const_iterator upper_bound(const K& x) const;
   

   Effects: Returns an iterator pointing to the first element with key that compares greater than key or x. Returns end() if no such element is found.

   Note: Overloads (3) and (4) participate in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling these functions without constructing an instance of Key.

   Complexity: Logarithmic in size().

   
   
   

equal_range

1. std::pair<iterator, iterator> equal_range(const Key& key);
   

2. std::pair<const_iterator, const_iterator> equal_range(const Key& key) const;
   

3. template <typename K>
   std::pair<iterator, iterator> equal_range(const K& x);
   

4. template <typename K>
   std::pair<const_iterator, const_iterator> equal_range(const K& x) const;
   

   Effects: Returns a range containing all elements with key that compares equivalent to key or x.

   • The first iterator in pair points to the first element that compares not less than key or x. It is equal to end() if no such element is found.
   • The second iterator in pair points to the first element that compares greater than key or x. It is equal to end() is no such element is found.

   Note: Overloads (3) and (4) participate in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling these functions without constructing an instance of Key.

   Complexity: Logarithmic in size().

   
   
   

find

1. iterator find(const Key& key);
   

2. const_iterator find(const Key& key) const;
   

3. template <typename K>
   iterator find(const K& x);
   

4. template <typename K>
   const_iterator find(const K& x) const;
   

   Effects: Returns an iterator pointing to the element with key equivalent to key or x. Returns end() if no such element is found. If there are several elements with key in the container, any of them may be returned.

   Note: Overloads (3) and (4) participate in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling these functions without constructing an instance of Key.

   Complexity: Logarithmic in size().

   
   
   

count

1. size_type count(const Key& key) const;
   

2. template <typename K>
   size_type count(const K& x) const;
   

   Effects: Returns the number of elements with key equivalent to key or x.

   Note: Overload (2) participates in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling this function without constructing an instance of Key.

   Complexity: Logarithmic in size() plus linear in the number of the elements found.

   
   
   

contains

1. bool contains(const Key& key) const;
   

2. template <typename K>
   bool contains(const K& x) const;
   

   Effects: Returns true if the container contains an element with key equivalent to key or x, otherwise returns false.

   Note: Overload (2) participates in overload resolution only if Compare::is_transparent exists and is a valid type. It allows calling this function without constructing an instance of Key.

   Complexity: Logarithmic in size().

   
   
   

Non-member Functions

operator==

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator==
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Checks if the contents of x and y are equal.

   The contents of x and y are equal if the following conditions hold:

   • x.size() == y.size()
   • Each element in x compares equal with the element in y at the same position.

   The comparison is performed by std::equal. This comparison ignores the container's ordering Compare.

   Returns: Returns true if the contents of the x and y are equal, false otherwise.

   
   
   

operator!=

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator!=
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Checks if the contents of x and y are equal.

   For details see operator==.

   Returns: Returns true if the contents of the x and y are not equal, false otherwise.

   
   
   

operator<

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator<
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Compares the contents of x and y lexicographically. The comparison is performed by a function std::lexicographical_compare. This comparison ignores the container's ordering Compare.

   Returns: true if the contents of the x are lexicographically less than the contents of y, false otherwise.

   
   
   

operator>

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator>
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Compares the contents of lhs and rhs lexicographically.

   The comparison is performed by a function std::lexicographical_compare. This comparison ignores the container's ordering Compare.

   Returns: true if the contents of the x are lexicographically greater than the contents of y, false otherwise.

   
   
   

operator<=

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator<=
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Compares the contents of x and y lexicographically. The comparison is performed by a function std::lexicographical_compare. This comparison ignores the container's ordering Compare.

   Returns: true if the contents of the x are lexicographically less than or equal to the contents of y, false otherwise.

   
   
   

operator>=

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   bool operator>=
   (
       const small_multimap<K, T, N, C, A>& x,
       const small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Compares the contents of x and y lexicographically. The comparison is performed by a function std::lexicographical_compare. This comparison ignores the container's ordering Compare.

   Returns: true if the contents of the x are lexicographically greater than or equal to the contents of y, false otherwise.

   
   
   

swap

1. template <typename K, typename T, std::size_t N, typename C, typename A>
   void swap
   (
       small_multimap<K, T, N, C, A>& x,
       small_multimap<K, T, N, C, A>& y
   );
   

   Effects: Swaps the contents of x and y. Calls x.swap(y).

   
   
   

erase_if

1. template <typename K, typename T, std::size_t N, typename C, typename A, typename Predicate>
   typename small_multimap<K, T, N, C, A>::size_type
       erase_if(small_multimap<K, T, N, C, A>& c, Predicate pred);
   

   Effects: Erases all elements that satisfy the predicate pred from the container.

   pred is unary predicate which returns true if the element should be removed.

   Returns: The number of erased elements.

   
   
   

End of document.