std::uninitialized_move
From cppreference.com
| Defined in header <memory>
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| template< class InputIt, class ForwardIt > ForwardIt uninitialized_move( InputIt first, InputIt last, ForwardIt d_first ); |
(1) | (since C++17) |
| template< class ExecutionPolicy, class InputIt, class ForwardIt > ForwardIt uninitialized_move( ExecutionPolicy&& policy, InputIt first, InputIt last, ForwardIt d_first ); |
(2) | (since C++17) |
1) Moves 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(std::move(*first));
If an exception is thrown during the initialization, some objects in
[first, last) are left in a valid but unspecified state, and the objects already constructed are destroyed in an unspecified order.2) Same as (1), but executed according to
policy. This overload participates in overload resolution only if |
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true. |
(until C++20) |
|
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true. |
(since C++20) |
Contents |
Parameters
| first, last | - | the range of the elements to move |
| 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 LegacyInputIterator.
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-ForwardIt must meet the requirements of LegacyForwardIterator.
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-No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.
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Return value
Iterator to the element past the last element moved.
Complexity
Linear in the distance between first and last.
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 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.
Possible implementation
template<class InputIt, class ForwardIt> ForwardIt uninitialized_move(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(std::move(*first)); } return current; } catch (...) { for (; d_first != current; ++d_first) { d_first->~Value(); } throw; } } |
Example
Run this code
#include <cstdlib> #include <iomanip> #include <iostream> #include <memory> #include <string> void print(auto rem, auto first, auto last) { for (std::cout << rem; first != last; ++first) std::cout << std::quoted(*first) << ' '; std::cout << '\n'; } int main() { std::string in[] { "Home", "Work!" }; print("initially, in: ", std::begin(in), std::end(in)); if ( constexpr auto sz = std::size(in); void* out = std::aligned_alloc(alignof(std::string), sizeof(std::string) * sz) ) { try { auto first {static_cast<std::string*>(out)}; auto last {first + sz}; std::uninitialized_move(std::begin(in), std::end(in), first); print("after move, in: ", std::begin(in), std::end(in)); print("after move, out: ", first, last); std::destroy(first, last); } catch (...) { std::cout << "Exception!\n"; } std::free(out); } }
Possible output:
initially, in: "Home" "Work!" after move, in: "" "" after move, out: "Home" "Work!"
See also
| copies a range of objects to an uninitialized area of memory (function template) | |
| (C++17) |
moves a number of objects to an uninitialized area of memory (function template) |
| (C++20) |
moves a range of objects to an uninitialized area of memory (niebloid) |
