std::uninitialized_copy_n
From cppreference.com
Defined in header
<memory>
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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
as if by
for ( ; n > 0; ++d_first, ++first, --n) ::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.
Contents |
[edit] Parameters
first | - | the beginning of the range of the elements to copy |
d_first | - | the beginning of the destination range |
Type requirements | ||
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InputIt must meet the requirements of InputIterator .
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ForwardIt must meet the requirements of ForwardIterator .
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[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*>(std::addressof(*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
copies a range of objects to an uninitialized area of memory (function template) |
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(parallelism TS)
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parallelized version of std::uninitialized_copy_n (function template) |