multimap get_allocator() function in C++ STL

C++Server Side ProgrammingProgramming

In this article we will be discussing the working, syntax, and examples of multimap::get_allocator() function in C++ STL.

What is Multimap in C++ STL?

Multimaps are the associative containers, which are similar to map containers. It also facilitates to store the elements formed by a combination of key-value and mapped value in a specific order. In a multimap container there can be multiple elements associated with the same key. The data is internally always sorted with the help of its associated keys.

What is multimap::get_allocator()?

multimap::get_allocator() function is an inbuilt function in C++ STL, which is defined in <map> header file. get_allocator() is used to allocate the memory chunks to a multimap container. This function returns a copy of the allocator object of the container associated with it.

An allocator is an object which is responsible for dynamically memory allocation of a container.

Syntax

multi_name.get_allocator();

Parameters

The function accepts no parameter.

Return value

This function returns the allocator of the container associated.

Input 

int *Ptr;
std::multimap<int> newmap;
newmap.insert(make_pair(‘A’, 22));
newmap.insert(make_pair(‘B’, 78));
newmap.insert(make_pair(‘C’, 66));
newmap.insert(make_pair(‘D’, 81));
Ptr = mymap.get_allocator().allocate(4);

Output 

ptr = A:22 B:78 C:66 D:81

Example

 Live Demo

#include <iostream>
#include <map>
using namespace std;
int main(){
   int arrsize;
   multimap<char, int> mul;
   pair<const char, int>* pr;
   pr = mul.get_allocator().allocate(15);
   // assign some values to array
   arrsize = sizeof(multimap<char, int>::value_type) * 10;
   cout << "Size of the allocated array is: "<< arrsize << " bytes.\n";
   mul.get_allocator().deallocate(pr, 5);
   return 0;
}

Output

If we run the above code it will generate the following output −

Size of the allocated array is: 80 bytes.

Example

 Live Demo

#include <iostream>
#include <map>
using namespace std;
int main(){
   int arrsize;
   multimap<char, int> mul;
   pair<const char, int>* pr;
   pr = mul.get_allocator().allocate(2);
   // assign some values to array
   arrsize = sizeof(multimap<char, int>::value_type) * 5;
   cout << "Size of the allocated array is: "<< arrsize << " bytes.\n";
   mul.get_allocator().deallocate(pr, 5);
   return 0;
}

Output

If we run the above code it will generate the following output −

Size of the allocated array is: 40 bytes.
raja
Published on 22-Apr-2020 12:10:11
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