C++

Reference

<memory>

function template
<memory>

std::uninitialized_fill_n

template <class ForwardIterator, class Size, class T> void uninitialized_fill_n (ForwardIterator first, Size n, const T& x);
template <class ForwardIterator, class Size, class T> ForwardIterator uninitialized_fill_n (ForwardIterator first, Size n, const T& x);
Fill block of memory
Constructs n elements in the array pointed by first, initializing them to a value of x.

Unlike algorithm fill_n, uninitialized_fill_n constructs the objects in-place, instead of just copying the value to them. This allows to obtain fully constructed copies into a range of uninitialized memory, such as a memory block obtained by a call to get_temporary_buffer or malloc.

The behavior of this function template is equivalent to:
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template < class ForwardIterator, class Size, class T > void uninitialized_fill_n ( ForwardIterator first, Size n, const T& x ) { for (; n--; ++first) new (static_cast<void*>(&*first)) typename iterator_traits<ForwardIterator>::value_type(x); }
The behavior of this function template is equivalent to:
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template < class ForwardIterator, class Size, class T > ForwardIterator uninitialized_fill_n ( ForwardIterator first, Size n, const T& x ) { for (; n--; ++first) new (static_cast<void*>(&*first)) typename iterator_traits<ForwardIterator>::value_type(x); return first; }

Parameters

first
Forward iterator to the initial position in an uninitialized sequence of at least n elements.
n
Number of elements to initialize
Size is expected to be a numeric type.
x
Value to be used to fill the range.

Return value

none
An iterator to the last element of the destination sequence where elements have been initialized.

Example

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// uninitialized_fill_n example #include <iostream> #include <memory> #include <string> int main () { // get block of uninitialized memory: std::pair <std::string*,std::ptrdiff_t> result = std::get_temporary_buffer<std::string>(3); if (result.second>0) { std::uninitialized_fill_n ( result.first, result.second, "c++ rocks!" ); for (int i=0; i<result.second; i++) std::cout << result.first[i] << '\n'; std::return_temporary_buffer(result.first); } return 0; }

Output:
c++ rocks! c++ rocks! c++ rocks!


Complexity

Linear: Constructs (copy constructor) n objects.

See also

fill_n
Fill sequence with value (function template)
uninitialized_copy
Copy block of memory (function template)
uninitialized_fill
Fill block of memory (function template)
get_temporary_buffer
Get block of temporary memory (function template)