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std::uninitialized_fill_n

From cppreference.com
< cpp‎ | memory
 
 
 
 
Defined in header <memory>
template< class ForwardIt, class Size, class T >
void uninitialized_fill_n( ForwardIt first, Size count, const T& value )

Copies the given value value to the first count elements in an uninitialized memory area beginning at first. The elements in the uninitialized area are constructed using copy constructor.

Contents

[edit] Parameters

first - the beginning of the range of the elements to initialize
count - number of elements to construct
value - the value to construct the elements with
Type requirements
-
ForwardIt must meet the requirements of ForwardIterator.

[edit] Return value

Iterator to the element past the last element copied.

[edit] Complexity

Linear in count

[edit] Possible implementation

template< class ForwardIt, class Size, class T >
void uninitialized_fill_n(ForwardIt first, Size count
                          const T& value)
{
    typedef typename std::iterator_traits<ForwardIt>::value_type Value;
    for (; count > 0; ++first, --count) {
        ::new (static_cast<void*>(&*first)) Value(value);
    }
    return first;
}

[edit] Example

#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_n(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
(function template) [edit]