std::uninitialized_copy_n - cppreference.com

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# std::uninitialized_copy_n

From cppreference.com
< cpp‎ | memory

Defined in header `<memory>` |  |
template< class InputIt, class Size, class ForwardIt > ForwardIt uninitialized_copy_n( InputIt first, Size count, ForwardIt d_first); |  | (since C++11)

Copies `count` elements from a range beginning at `first` to an uninitialized memory area beginning at `d_first`.

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

### [edit] Parameters

first | - | the beginning of 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`.

### [edit] Return value

Iterator to the element past the last element copied.

### [edit] Complexity

Linear in `count`.

### [edit] Possible implementation

    template<class InputIt, class Size, class ForwardIt>
    ForwardIt uninitialized_copy_n(InputIt first, Size count, ForwardIt d_first)
    {
        typedef typename std::iterator_traits<ForwardIt>::value_type Value;
        ForwardIt current = d_first;
        try {
            for (; count > 0; ++first, ++current, --count) {
                ::new (static_cast<void*>(&*current)) Value(*first);
            }
        } catch (...) {
            for (; d_first != current; ++d_first) {
                d_first->~Value();
            }
            throw;
        }
        return current;
    }

### [edit] 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_n(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

### [edit] See also

uninitialized_copy | copies a range of objects to an uninitialized area of memory (function template) [edit]

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