std::uninitialized_copy
From cppreference.com
| Defined in header <memory>
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| template< class InputIt, class ForwardIt > ForwardIt uninitialized_copy( InputIt first, InputIt last, ForwardIt d_first ); |
(1) | |
| template< class ExecutionPolicy, class InputIt, class ForwardIt > ForwardIt uninitialized_copy( ExecutionPolicy&& policy, InputIt first, InputIt last, ForwardIt d_first ); |
(2) | (since C++17) |
1) 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 std::iterator_traits<ForwardIt>::value_type(*first);
If an exception is thrown during the initialization, the function has no effects.
2) Same as (1), but executed according to
policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueContents |
[edit] Parameters
| first, last | - | the range of the elements to copy |
| d_first | - | the beginning of the destination range |
| policy | - | the execution policy to use. See execution policy for details. |
| Type requirements | ||
-InputIt must meet the requirements of InputIterator.
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-ForwardIt must meet the requirements of ForwardIterator.
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-No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.
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[edit] Return value
Iterator to the element past the last element copied.
[edit] Complexity
Linear in the distance between first and last
[edit] 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
ExecutionPolicyis one of the three standard policies, std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
[edit] 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; } } |
[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(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
[edit] See also
| (C++11) |
copies a number of objects to an uninitialized area of memory (function template) |