std::get_temporary_buffer

 

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Defined in header <memory>
template< class T > std::pair< T*, std::ptrdiff_t > get_temporary_buffer( std::ptrdiff_t count );

Allocates uninitialized contiguous storage, which should be sufficient to store up to count adjacent objects of type T. The request is non-binding and the implementation may allocate less or more than necessary to store count adjacent objects.

Parameters

count

-

the desired number of objects

Return value

An std::pair holding a pointer to the beginning of the allocated storage and the number of objects that fit in the storage that was actually allocated.

If no memory could be allocated, or allocated storage is not enough to store a single element of type T, the first element of the result is a null pointer and the second element is zero.

Exceptions

(none)	(until C++11)
noexcept specification:   noexcept	(since C++11)

Example

Run this code

#include <algorithm>
#include <iostream>
#include <iterator>
#include <memory>
#include <string>
 
int main()
{
    const std::string s[] = {"string", "1", "test", "..."};
    const auto p = std::get_temporary_buffer<std::string>(4);
    // requires that p.first is passed to return_temporary_buffer
    // (beware of early exit points and exceptions), or better use:
    std::unique_ptr<std::string, void(*)(std::string*)> on_exit(p.first,
    [](std::string* p)
    {
        std::cout << "returning temporary buffer...\n";
        std::return_temporary_buffer(p);
    });
 
    std::copy(s, s + p.second,
              std::raw_storage_iterator<std::string*, std::string>(p.first));
    // has same effect as: std::uninitialized_copy(s, s + p.second, p.first);
    // requires that each string in p is individually destroyed
    // (beware of early exit points and exceptions)
 
    std::copy(p.first, p.first + p.second,
              std::ostream_iterator<std::string>{std::cout, "\n"});
 
    std::for_each(p.first, p.first + p.second, [](std::string& e)
    {
        e.~basic_string<char>();
    }); // same as: std::destroy(p.first, p.first + p.second);
 
    // manually reclaim memory if unique_ptr-like technique is not used:
    // std::return_temporary_buffer(p.first);
}

Output:

string
1
test
...
returning temporary buffer...

See also

return_temporary_buffer (deprecated in C++17)(removed in C++20)

frees uninitialized storage (function template)