std::uninitialized_copy
Defined in header <memory> |
||
---|---|---|
template< class InputIt, class NoThrowForwardIt > NoThrowForwardIt uninitialized_copy( InputIt first, InputIt last, NoThrowForwardIt d_first ); |
(1) | |
template< class ExecutionPolicy, class ForwardIt, class NoThrowForwardIt > NoThrowForwardIt uninitialized_copy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, NoThrowForwardIt 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 (/*VOIDIFY*/(*d_first)) typename std::iterator_traits<NoThrowForwardIt>::value_type(*first);
where /*VOIDIFY*/(e)
is:
static_cast<void*>(&e) |
(until C++11) |
static_cast<void*>(std::addressof(e)) |
(since C++11) (until C++20) |
const_cast<void*>(static_cast<const volatile void*>(std::addressof(e))) |
(since C++20) |
If an exception is thrown during the initialization, the objects already constructed are destroyed in an unspecified order.
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>>
(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(since C++20) is true.
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 LegacyInputIterator. |
||
-ForwardIt must meet the requirements of LegacyForwardIterator. |
||
-NoThrowForwardIt must meet the requirements of LegacyForwardIterator. |
||
-No increment, assignment, comparison, or indirection through valid instances of NoThrowForwardIt may throw exceptions. Applying &* to a NoThrowForwardIt value must yield a pointer to its value type. (until C++11) |
Return value
Iterator to the element past the last element copied.
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
ExecutionPolicy
is 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 NoThrowForwardIt> NoThrowForwardIt uninitialized_copy(InputIt first, InputIt last, NoThrowForwardIt d_first) { using T = typename std::iterator_traits<NoThrowForwardIt>::value_type; NoThrowForwardIt current = d_first; try { for (; first != last; ++first, (void) ++current) { ::new (const_cast<void*>(static_cast<const volatile void*>( std::addressof(*current)))) T(*first); } return current; } catch (...) { for (; d_first != current; ++d_first) { d_first->~T(); } throw; } } |
Example
#include <iostream> #include <memory> #include <cstdlib> #include <string> int main() { const char *v[] = {"This", "is", "an", "example"}; auto sz = std::size(v); if(void *pbuf = std::aligned_alloc(alignof(std::string), sizeof(std::string) * sz)) { try { auto first = static_cast<std::string*>(pbuf); auto last = std::uninitialized_copy(std::begin(v), std::end(v), first); for (auto it = first; it != last; ++it) std::cout << *it << '_'; std::cout << '\n'; std::destroy(first, last); } catch(...) {} std::free(pbuf); } }
Output:
This_is_an_example_
See also
(C++11)
|
copies a number of objects to an uninitialized area of memory (function template) |
(C++20)
|
copies a range of objects to an uninitialized area of memory (niebloid) |
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