Reference documentation for deal.II version Git 053e5b2 2017-07-21 22:33:36 -0600
Public Types | Public Member Functions | Private Attributes | Friends | Related Functions | List of all members
ArrayView< ElementType > Class Template Reference

#include <deal.II/base/array_view.h>

Public Types

typedef ElementType value_type
 

Public Member Functions

 ArrayView ()
 
 ArrayView (value_type *starting_element, const std::size_t n_elements)
 
 ArrayView (const ArrayView< typename boost::remove_cv< value_type >::type > &view)
 
std::size_t size () const
 
value_typeoperator[] (const std::size_t i) const
 

Private Attributes

value_type *const starting_element
 
const std::size_t n_elements
 

Friends

class ArrayView< const ElementType >
 

Related Functions

(Note that these are not member functions.)

template<typename ElementType >
ArrayView< ElementType > make_array_view (std::vector< ElementType > &vector)
 
template<typename ElementType >
ArrayView< const ElementType > make_array_view (const std::vector< ElementType > &vector)
 
template<typename ElementType >
ArrayView< ElementType > make_array_view (std::vector< ElementType > &vector, const std::size_t starting_index, const std::size_t size_of_view)
 
template<typename ElementType >
ArrayView< const ElementType > make_array_view (const std::vector< ElementType > &vector, const std::size_t starting_index, const std::size_t size_of_view)
 
template<typename ElementType >
ArrayView< ElementType > make_array_view (Table< 2, ElementType > &table, const typename Table< 2, ElementType >::size_type row)
 
template<typename ElementType >
ArrayView< const ElementType > make_array_view (const Table< 2, ElementType > &table, const typename Table< 2, ElementType >::size_type row)
 
template<typename ElementType >
ArrayView< ElementType > make_array_view (Table< 2, ElementType > &table, const typename Table< 2, ElementType >::size_type row, const typename Table< 2, ElementType >::size_type starting_column, const std::size_t size_of_view)
 
template<typename ElementType >
ArrayView< const ElementType > make_array_view (const Table< 2, ElementType > &table, const typename Table< 2, ElementType >::size_type row, const typename Table< 2, ElementType >::size_type starting_column, const std::size_t size_of_view)
 

Detailed Description

template<typename ElementType>
class ArrayView< ElementType >

A class that represents a window of memory locations of type ElementType and presents it as if it was an array that can be accessed via an operator[]. In essence, this class is nothing more than just a pointer to the first location and an integer that represents the length of the array in elements. The memory remains owned by whoever allocated it, as this class does not take over ownership.

The advantage of using this class is that you don't have to pass around pairs of pointers and that operator[] checks for the validity of the index with which you subscript this array view.

This class can handle views to both non-constant and constant memory locations. If you want to represent a view of a constant array, then the template argument type of this class needs to be const as well. The following code snippet gives an example:

std::vector<int> array = get_data(); // a writable array
ArrayView<int> view (&array[5], 5); // a view of elements 5..9 (inclusive)
view[2] = 42; // array[7] is set to 42
ArrayView<const int> const_view (&array[5], 5); // same view, but read-only
int element_7 = const_view[2]; // returns 42
const_view[2] = 42; // error, can't write into this view

In either case, accessing an element of a view does not change the ArrayView object itself, and consequently ArrayView::operator[] is a const function. This corresponds to the notion that a view simply represents a, well, "view" of memory that is owned by someone else. Thus, accessing elements of the view changes the memory managed by some other object, but not the view itself, allowing us to make ArrayView::operator[] a const member function. This is in contrast to, say, std::vector, which manages the memory it points to and changing an element of the std::vector therefore changes the std::vector object itself – consequently, the std::vector::operator[] is non-const.

Author
Wolfgang Bangerth, 2015

Definition at line 71 of file array_view.h.

Member Typedef Documentation

template<typename ElementType>
typedef ElementType ArrayView< ElementType >::value_type

A typedef that denotes the "value_type" of this container-like class, i.e., the type of the element it "stores" or points to.

Definition at line 78 of file array_view.h.

Constructor & Destructor Documentation

template<typename ElementType >
ArrayView< ElementType >::ArrayView ( )
inline

Default constructor. Creates an invalid view that does not point to anything at all.

Definition at line 158 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType >::ArrayView ( value_type starting_element,
const std::size_t  n_elements 
)
inline

Constructor.

Parameters
[in]starting_elementA pointer to the first element of the array this object should represent.
[in]n_elementsThe length (in elements) of the chunk of memory this object should represent.
Note
The object that is constructed from these arguments has no knowledge how large the object into which it points really is. As a consequence, whenever you call ArrayView::operator[], the array view can check that the given index is within the range of the view, but it can't check that the view is indeed a subset of the valid range of elements of the underlying object that allocated that range. In other words, you need to ensure that the range of the view specified by the two arguments to this constructor is in fact a subset of the elements of the array into which it points. The appropriate way to do this is to use the make_array_view() functions.

Definition at line 168 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType >::ArrayView ( const ArrayView< typename boost::remove_cv< value_type >::type > &  view)
inline

Copy constructor from array views that point to non-const elements. If the current object will point to non-const elements, then this is a straight forward copy constructor. On the other hand, if the current type's ElementType template argument is a const qualified type, then the current constructor is a conversion constructor that converts a non-const view to a const view, akin to converting a non-const pointer to a const pointer.

Definition at line 179 of file array_view.h.

Member Function Documentation

template<typename ElementType >
std::size_t ArrayView< ElementType >::size ( ) const
inline

Return the size (in elements) of the view of memory this object represents.

Definition at line 190 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType >::value_type & ArrayView< ElementType >::operator[] ( const std::size_t  i) const
inline

Return a reference to the \(i\)th element of the range represented by the current object.

This function is marked as const because it does not change the view object. It may however return a reference to a non-const memory location depending on whether the template type of the class is const or not.

Definition at line 199 of file array_view.h.

Friends And Related Function Documentation

template<typename ElementType >
ArrayView< ElementType > make_array_view ( std::vector< ElementType > &  vector)
related

Create a view to an entire std::vector object. This is equivalent to initializing an ArrayView object with a pointer to the first element and the size of the given argument.

This function is used for non-const references to objects of vector type. Such objects contain elements that can be written to. Consequently, the return type of this function is a view to a set of writable objects.

Parameters
[in]vectorThe vector for which we want to have an array view object. The array view corresponds to the entire vector.

Definition at line 224 of file array_view.h.

template<typename ElementType >
ArrayView< const ElementType > make_array_view ( const std::vector< ElementType > &  vector)
related

Create a view to an entire std::vector object. This is equivalent to initializing an ArrayView object with a pointer to the first element and the size of the given argument.

This function is used for const references to objects of vector type because they contain immutable elements. Consequently, the return type of this function is a view to a set of const objects.

Parameters
[in]vectorThe vector for which we want to have an array view object. The array view corresponds to the entire vector.

Definition at line 248 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType > make_array_view ( std::vector< ElementType > &  vector,
const std::size_t  starting_index,
const std::size_t  size_of_view 
)
related

Create a view to a part of a std::vector object. This is equivalent to initializing the ArrayView object with a pointer to the starting_index- th element and the size_of_view as the length of the view.

This function is used for non-const references to objects of vector type. Such objects contain elements that can be written to. Consequently, the return type of this function is a view to a set of writable objects.

Parameters
[in]vectorThe vector for which we want to have an array view object.
[in]starting_indexThe index of the first element of the vector that will be part of this view.
[in]size_of_view
Precondition
starting_index + size_of_view <= vector.size()

Definition at line 277 of file array_view.h.

template<typename ElementType >
ArrayView< const ElementType > make_array_view ( const std::vector< ElementType > &  vector,
const std::size_t  starting_index,
const std::size_t  size_of_view 
)
related

Create a view to a part of a std::vector object. This is equivalent to initializing the ArrayView object with a pointer to the starting_index- th element and the size_of_view as the length of the view.

This function is used for const references to objects of vector type because they contain immutable elements. Consequently, the return type of this function is a view to a set of const objects.

Parameters
[in]vectorThe vector for which we want to have an array view object.
[in]starting_indexThe index of the first element of the vector that will be part of this view.
[in]size_of_view
Precondition
starting_index + size_of_view <= vector.size()

Definition at line 312 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType > make_array_view ( Table< 2, ElementType > &  table,
const typename Table< 2, ElementType >::size_type  row 
)
related

Create a view to an entire row of a Table<2> object. This is equivalent to initializing an ArrayView object with a pointer to the first element of the given row, and the length of the row as the length of the view.

This function is used for non-const references to objects of Table type. Such objects contain elements that can be written to. Consequently, the return type of this function is a view to a set of writable objects.

Parameters
[in]tableThe Table for which we want to have an array view object. The array view corresponds to an entire row.
[in]rowThe index of the row into the table to which this view should correspond.

Definition at line 344 of file array_view.h.

template<typename ElementType >
ArrayView< const ElementType > make_array_view ( const Table< 2, ElementType > &  table,
const typename Table< 2, ElementType >::size_type  row 
)
related

Create a view to an entire row of a Table<2> object. This is equivalent to initializing an ArrayView object with a pointer to the first element of the given row, and the length of the row as the length of the view.

This function is used for const references to objects of Table type because they contain immutable elements. Consequently, the return type of this function is a view to a set of const objects.

Parameters
[in]tableThe Table for which we want to have an array view object. The array view corresponds to an entire row.
[in]rowThe index of the row into the table to which this view should correspond.

Definition at line 372 of file array_view.h.

template<typename ElementType >
ArrayView< ElementType > make_array_view ( Table< 2, ElementType > &  table,
const typename Table< 2, ElementType >::size_type  row,
const typename Table< 2, ElementType >::size_type  starting_column,
const std::size_t  size_of_view 
)
related

Create a view to (a part of) a row of a Table<2> object.

This function is used for non-const references to objects of Table type. Such objects contain elements that can be written to. Consequently, the return type of this function is a view to a set of writable objects.

Parameters
[in]tableThe Table for which we want to have an array view object. The array view corresponds to an entire row.
[in]rowThe index of the row into the table to which this view should correspond.
[in]starting_columnThe index of the column into the given row of the table that corresponds to the first element of this view.
[in]size_of_viewThe number of elements this view should have. This corresponds to the number of columns in the current row to which the view should correspond.

Definition at line 403 of file array_view.h.

template<typename ElementType >
ArrayView< const ElementType > make_array_view ( const Table< 2, ElementType > &  table,
const typename Table< 2, ElementType >::size_type  row,
const typename Table< 2, ElementType >::size_type  starting_column,
const std::size_t  size_of_view 
)
related

Create a view to (a part of) a row of a Table<2> object.

This function is used for const references to objects of Table type because they contain immutable elements. Consequently, the return type of this function is a view to a set of const objects.

Parameters
[in]tableThe Table for which we want to have an array view object. The array view corresponds to an entire row.
[in]rowThe index of the row into the table to which this view should correspond.
[in]starting_columnThe index of the column into the given row of the table that corresponds to the first element of this view.
[in]size_of_viewThe number of elements this view should have. This corresponds to the number of columns in the current row to which the view should correspond.

Definition at line 441 of file array_view.h.

Member Data Documentation

template<typename ElementType>
value_type* const ArrayView< ElementType >::starting_element
private

A pointer to the first element of the range of locations in memory that this object represents.

Definition at line 141 of file array_view.h.

template<typename ElementType>
const std::size_t ArrayView< ElementType >::n_elements
private

The length of the array this object represents.

Definition at line 146 of file array_view.h.


The documentation for this class was generated from the following file: