Difference between revisions of "cpp/memory/raw storage iterator"

Latest revision as of 01:09, 23 October 2023

The output iterator std::raw_storage_iterator makes it possible for standard algorithms to store results in uninitialized memory. Whenever the algorithm writes an object of type T to the dereferenced iterator, the object is copy-constructed into the location in the uninitialized storage pointed to by the iterator. The template parameter OutputIt is any type that meets the requirements of LegacyOutputIterator and has operator* defined to return an object, for which operator& returns an object of type T*. Usually, the type T* is used as OutputIt.

[edit] Type requirements

[edit] Member functions

[edit] Member types

[edit] Note

std::raw_storage_iterator was deprecated primarily because of its exception-unsafe behavior. Unlike std::uninitialized_copy, it doesn't handle exceptions during operations like std::copy safely, potentially leading to resource leaks due to a lack of tracking the number of successfully constructed objects and their proper destruction in the presence of exceptions.

[edit] Example

#include <algorithm>
#include <iostream>
#include <memory>
#include <string>
 
int main()
{
    const std::string s[] = {"This", "is", "a", "test", "."};
    std::string* p = std::allocator<std::string>().allocate(5);
 
    std::copy(std::begin(s), std::end(s),
              std::raw_storage_iterator<std::string*, std::string>(p));
 
    for (std::string* i = p; i != p + 5; ++i)
    {
        std::cout << *i << '\n';
        i->~basic_string<char>();
    }
    std::allocator<std::string>().deallocate(p, 5);
}

This
is
a
test
.

[edit] See also