C++ Memory Library - allocator
Description
It defines the memory models to be used by some parts of the Standard Library, and most specifically, by STL containers.
Declaration
Following is the declaration for std::allocator function.
template <class T> class allocator;
C++11
template <class T> class allocator;
Parameters
T − It contains information about types of elements.
Member types
| Type |
Definition |
value_type |
T |
pointer (deprecated in C++17) |
T* |
const_pointer (deprecated in C++17) |
const T* |
reference (deprecated in C++17) |
T& |
const_reference (deprecated in C++17) |
const T& |
size_type (deprecated in C++17) |
std::size_t |
difference_type(deprecated in C++17) |
std::ptrdiff_t |
propagate_on_container_move_assignment (C++14) |
std::true_type |
rebind (deprecated in C++17) |
template<class U >struct rebind { typedef allocator<U>other;}; |
is_always_equal(C++17) |
std::true_type |
Example
In below example explains about std::allocator function.
#include <memory>
#include <iostream>
#include <string>
int main() {
std::allocator<int> a1;
int* a = a1.allocate(10);
a[9] = 7;
std::cout << a[9] << '\n';
a1.deallocate(a, 10);
std::allocator<std::string> a2;
decltype(a1)::rebind<std::string>::other a2_1;
std::allocator_traits<decltype(a1)>::rebind_alloc<std::string> a2_2;
std::string* s = a2.allocate(2);
a2.construct(s, "foo");
a2.construct(s + 1, "bar");
std::cout << s[0] << ' ' << s[1] << '\n';
a2.destroy(s);
a2.destroy(s + 1);
a2.deallocate(s, 2);
}
Let us compile and run the above program, this will produce the following result −
7
foo bar
memory.htm
