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| Categories: allocators, iterators, adaptors | Component type: type |
In C++, the operator
new allocates memory for an object and then creates an object at that location by calling a constructor. Occasionally, however, it is useful to separate those two operations.
[1] If
i is an iterator that points to a region of uninitialized memory, then you can use
construct to create an object in the location pointed to by
i.
Raw_storage_iterator is an adaptor that makes this procedure more convenient. If
r is a
raw_storage_iterator, then it has some underlying iterator
i. The expression
*r = x is equivalent to
construct(&*i, x).
class Int {
public:
Int(int x) : val(x) {}
int get() { return val; }
private:
int val;
};
int main()
{
int A1[] = {1, 2, 3, 4, 5, 6, 7};
const int N = sizeof(A1) / sizeof(int);
Int* A2 = (Int*) malloc(N * sizeof(Int));
transform(A1, A1 + N,
raw_storage_iterator<Int*, int>(A2),
negate<int>());
}
Defined in the standard header
memory, and in the nonstandard backward-compatibility header
iterator.h.
| Parameter | Description | Default |
| OutputIterator | The type of the raw_storage_iterator's underlying iterator. | |
T | The type that will be used as the argument to the constructor. | |
OutputIterator
-
ForwardIterator is a model of ForwardIterator
-
ForwardIterator's value type has a constructor that takes a single argument of type T.
None.
| Member | Where defined | Description |
raw_storage_iterator(ForwardIterator x) | raw_storage_iterator | See below. |
raw_storage_iterator(const raw_storage_iterator&) | trivial | The copy constructor |
raw_storage_iterator& operator=(const raw_storage_iterator&) | trivial | The assignment operator |
raw_storage_iterator& operator*() | OutputIterator | Used to implement the OutputIterator expression *i = x. [2] |
raw_storage_iterator& operator=(const Sequence::value_type&) | OutputIterator | Used to implement the OutputIterator expression *i = x. [2] |
raw_storage_iterator& operator++() | OutputIterator | Preincrement. |
raw_storage_iterator& operator++(int) | OutputIterator | Postincrement. |
output_iterator_tag iterator_category(const raw_storage_iterator&) | iterator_tags | Returns the iterator's category. This is a global function, not a member. |
These members are not defined in the
OutputIterator requirements, but are specific to
raw_storage_iterator.
| Function | Description |
raw_storage_iterator(ForwardIterator i) | Creates a raw_storage_iterator whose underlying iterator is i. |
raw_storage_iterator& operator=(const T& val) | Constructs an object of ForwardIterator's value type at the location pointed to by the iterator, using val as the constructor's argument. |
[1] In particular, this sort of low-level memory management is used in the implementation of some container classes.
[2] Note how assignment through a raw_storage_iterator is implemented. In general, unary operator* must be defined so that it returns a proxy object, where the proxy object defines operator= to perform the insert operation. In this case, for the sake of simplicity, the proxy object is the raw_storage_iterator itself. That is, *i returns i, and *i = t is equivalent to i = t. You should not, however, rely on this behavior. It is an implementation detail, and it is not guaranteed to remain the same in future versions.
Allocators,
construct,
destroy,
uninitialized_copy uninitialized_fill,
uninitialized_fill_n,
