std::uninitialized_copy

 

C++

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Low level memory management

 

Defined in header <memory>
template< class InputIt, class ForwardIt > ForwardIt uninitialized_copy( InputIt first, InputIt last, ForwardIt d_first );

Copies elements from the range [first, last) to an uninitialized memory area beginning at d_first as if by

for (; first != last; ++d_first, (void) ++first)
   ::new (static_cast<void*>(std::addressof(*d_first)))
      typename iterator_traits<ForwardIterator>::value_type(*first);

If an exception is thrown during the initialization, the function has no effects.

Parameters

first, last	-	the range of the elements to copy
d_first	-	the beginning of the destination range
Type requirements
- InputIt must meet the requirements of InputIterator.
- ForwardIt must meet the requirements of ForwardIterator.

Return value

Iterator to the element past the last element copied.

Complexity

Linear in the distance between first and last

Possible implementation

template<class InputIt, class ForwardIt> ForwardIt uninitialized_copy(InputIt first, InputIt last, ForwardIt d_first) { typedef typename std::iterator_traits<ForwardIt>::value_type Value; ForwardIt current = d_first; try { for (; first != last; ++first, (void) ++current) { ::new (static_cast<void*>(std::addressof(*current))) Value(*first); } return current; } catch (...) { for (; d_first != current; ++d_first) { d_first->~Value(); } throw; } }

Example

Run this code

#include <algorithm>
#include <iostream>
#include <memory>
#include <string>
#include <tuple>
#include <vector>
 
int main()
{
    std::vector<std::string> v = {"This", "is", "an", "example"};
 
    std::string* p;
    std::size_t sz;
    std::tie(p, sz)  = std::get_temporary_buffer<std::string>(v.size());
    sz = std::min(sz, v.size());
 
    std::uninitialized_copy(v.begin(), v.begin() + sz, p);
 
    for (std::string* i = p; i != p+sz; ++i) {
        std::cout << *i << ' ';
        i->~basic_string<char>();
    }
    std::return_temporary_buffer(p);
}

Output:

This is an example

See also

uninitialized_copy_n (C++11)	copies a number of objects to an uninitialized area of memory (function template)
std::experimental::parallel::uninitialized_copy (parallelism TS)	parallelized version of std::uninitialized_copy (function template)