raw_storage_iterator<ForwardIterator, T>




Categories: allocators, iterators, adaptors	Component type: type

Description

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).

Example

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>());
}

Definition

Defined in the standard header memory, and in the nonstandard backward-compatibility header iterator.h.

Template parameters

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.

Model of

Output Iterator

Type requirements

ForwardIterator is a model of Forward Iterator
ForwardIterator's value type has a constructor that takes a single argument of type T.

Public base classes

None.

Members

Member	Where defined	Description
`raw_storage_iterator(ForwardIterator x)`	`raw_storage_iterator`	See below.
`raw_storage_iterator(const raw_storage_iterator&)`	trivial iterator	The copy constructor
`raw_storage_iterator& operator=(const raw_storage_iterator&)`	trivial iterator	The assignment operator
`raw_storage_iterator& operator*()`	Output Iterator	Used to implement the output iterator expression `*i = x`. [2]
`raw_storage_iterator& operator=(const Sequence::value_type&)`	Output Iterator	Used to implement the output iterator expression `*i = x`. [2]
`raw_storage_iterator& operator++()`	Output Iterator	Preincrement.
`raw_storage_iterator& operator++(int)`	Output Iterator	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.

New members

These members are not defined in the Output Iterator 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.

Notes

[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.

Using this site means you accept its terms of use \| privacy policy	\|	trademark information
Copyright © 1993-2003 Silicon Graphics, Inc. All rights reserved.	\|	contact us