std::uninitialized_fill
From cppreference.com
Defined in header
<memory>
|
||
template< class ForwardIt, class T >
void uninitialized_fill( ForwardIt first, ForwardIt last, const T& value ); |
(1) | |
template< class ExecutionPolicy, class ForwardIt, class T >
void uninitialized_fill( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, const T& value ); |
(2) | (since C++17) |
1) Copies the given
value
to an uninitialized memory area, defined by the range [first, last)
as if by
for (; first != last; ++first) ::new (static_cast<void*>(std::addressof(*first))) typename iterator_traits<ForwardIterator>::value_type(x);
If an exception is thrown during the initialization, the function has no effects.
{{{1}}}
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 true
Contents |
[edit] Parameters
first, last | - | the range of the elements to initialize |
value | - | the value to construct the elements with |
policy | - | the execution policy to use. See execution policy for details. |
Type requirements | ||
-
ForwardIt must meet the requirements of ForwardIterator .
|
[edit] Return value
(none)
[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,
-
- if
policy
is std::parallel_vector_execution_policy, std::terminate is called - if
policy
is std::sequential_execution_policy or std::parallel_execution_policy, the algorithm exits with an std::exception_list containing all uncaught exceptions. If there was only one uncaught exception, the algorithm may rethrow it without wrapping in std::exception_list. It is unspecified how much work the algorithm will perform before returning after the first exception was encountered. - if
policy
is some other type, the behavior is implementation-defined
- if
- If the algorithm fails to allocate memory (either for itself or to construct an std::exception_list when handling a user exception), std::bad_alloc is thrown.
[edit] Possible implementation
template<class ForwardIt, class T> void uninitialized_fill(ForwardIt first, ForwardIt last, const T& value) { typedef typename std::iterator_traits<ForwardIt>::value_type Value; ForwardIt current = first; try { for (; current != last; ++current) { ::new (static_cast<void*>(std::addressof(*current))) Value(value); } } catch (...) { for (; first != current; ++first) { first->~Value(); } throw; } } |
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <memory> #include <string> #include <tuple> int main() { std::string* p; std::size_t sz; std::tie(p, sz) = std::get_temporary_buffer<std::string>(4); std::uninitialized_fill(p, p+sz, "Example"); for (std::string* i = p; i != p+sz; ++i) { std::cout << *i << '\n'; i->~basic_string<char>(); } std::return_temporary_buffer(p); }
Output:
Example Example Example Example
[edit] See also
copies an object to an uninitialized area of memory, defined by a start and a count (function template) |
|
(parallelism TS)
|
parallelized version of std::uninitialized_fill (function template) |