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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.

If an exception is thrown during the initialization, the function has no effects.

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;
    ForwardIt current = first;
    try {
        for (; count > 0; ++current, --count) {
            ::new (static_cast<void*>(&*current)) Value(value);
        }
    } catch (...) {
        for (; first != current; ++first) {
            first->~Value();
        }
        throw;
    }
}

[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]