Difference between revisions of "cpp/memory/uninitialized move n"

Revision as of 05:35, 6 July 2018

for ( ; n > 0; ++d_first, (void) ++first, --n)
   ::new (static_cast<void*>(std::addressof(*d_first)))
      typename std::iterator_traits<ForwardIt>::value_type(std::move(*first));

Parameters

Return value

A pair whose first element is an iterator to the element past the last element moved in the source range, and whose second element is an iterator to the element past the last element moved in the destination range.

Complexity

Linear in count.

Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

template<class InputIt, class Size, class ForwardIt>
std::pair<InputIt, ForwardIt> uninitialized_move_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, (void) ++current, --count) {
            ::new (static_cast<void*>(std::addressof(*current))) Value(std::move(*first));
        }
    } catch (...) {
        for (; d_first != current; ++d_first) {
            d_first->~Value();
        }
        throw;
    }
    return {first, current};
}

Example

See also