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std::raw_storage_iterator

From cppreference.com
< cpp‎ | memory
 
 
Dynamic memory management
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Allocators
Garbage collection support
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)



Uninitialized storage
raw_storage_iterator
(until C++20*)
(until C++20*)
 
 
Defined in header <memory>
template< class OutputIt, class T >

class raw_storage_iterator

    : public std::iterator<std::output_iterator_tag, void, void, void, void>;
(until C++17)
template< class OutputIt, class T >
class raw_storage_iterator;
(since C++17)
(deprecated in C++17)
(removed in C++20)

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.

Contents

[edit] Type requirements

-
OutputIt must meet the requirements of LegacyOutputIterator.

[edit] Member functions

creates a new raw_storage_iterator
(public member function) [edit]
constructs an object at the pointed-to location in the buffer
(public member function) [edit]
dereferences the iterator
(public member function) [edit]
advances the iterator
(public member function) [edit]
(since C++17)
provides access to the wrapped iterator
(public member function) [edit]

[edit] Member types

Member type Definition
iterator_category std::output_iterator_tag
value_type void
difference_type

void

(until C++20)

std::ptrdiff_t

(since C++20)
pointer void
reference void

Member types iterator_category, value_type, difference_type, pointer and reference are required to be obtained by inheriting from std::iterator<std::output_iterator_tag, void, void, void, void>.

(until C++17)

[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);
}

Output:

This
is
a
test
.

[edit] See also

provides information about allocator types
(class template) [edit]
implements multi-level allocator for multi-level containers
(class template) [edit]
checks if the specified type supports uses-allocator construction
(class template) [edit]