libstdc++
std::deque Class Reference
Inheritance diagram for std::deque:

List of all members.

Public Types

Public Member Functions

Protected Types

Protected Member Functions

Static Protected Member Functions

Protected Attributes


Detailed Description

A standard container using fixed-size memory allocation and constant-time manipulation of elements at either end.

Meets the requirements of a container, a reversible container, and a sequence, including the optional sequence requirements.

In previous HP/SGI versions of deque, there was an extra template parameter so users could control the node size. This extension turned out to violate the C++ standard (it can be detected using template template parameters), and it was removed.

Here's how a deque<Tp> manages memory. Each deque has 4 members:

  • Tp** _M_map
  • size_t _M_map_size
  • iterator _M_start, _M_finish

map_size is at least 8. map is an array of map_size pointers-to-. (The name map has nothing to do with the std::map class, and nodes should not be confused with std::list's usage of node.)

A node has no specific type name as such, but it is referred to as node in this file. It is a simple array-of-Tp. If Tp is very large, there will be one Tp element per node (i.e., an array of one). For non-huge Tp's, node size is inversely related to Tp size: the larger the Tp, the fewer Tp's will fit in a node. The goal here is to keep the total size of a node relatively small and constant over different Tp's, to improve allocator efficiency.

Not every pointer in the map array will point to a node. If the initial number of elements in the deque is small, the /middle/ map pointers will be valid, and the ones at the edges will be unused. This same situation will arise as the map grows: available map pointers, if any, will be on the ends. As new nodes are created, only a subset of the map's pointers need to be copied outward.

Class invariants:

  • For any nonsingular iterator i:
    • i.node points to a member of the map array. (Yes, you read that correctly: i.node does not actually point to a node.) The member of the map array is what actually points to the node.
    • i.first == *(i.node) (This points to the node (first Tp element).)
    • i.last == i.first + node_size
    • i.cur is a pointer in the range [i.first, i.last). NOTE: the implication of this is that i.cur is always a dereferenceable pointer, even if i is a past-the-end iterator.
  • Start and Finish are always nonsingular iterators. NOTE: this means that an empty deque must have one node, a deque with <N elements (where N is the node buffer size) must have one node, a deque with N through (2N-1) elements must have two nodes, etc.
  • For every node other than start.node and finish.node, every element in the node is an initialized object. If start.node == finish.node, then [start.cur, finish.cur) are initialized objects, and the elements outside that range are uninitialized storage. Otherwise, [start.cur, start.last) and [finish.first, finish.cur) are initialized objects, and [start.first, start.cur) and [finish.cur, finish.last) are uninitialized storage.
  • [map, map + map_size) is a valid, non-empty range.
  • [start.node, finish.node] is a valid range contained within [map, map + map_size).
  • A pointer in the range [map, map + map_size) points to an allocated node if and only if the pointer is in the range [start.node, finish.node].

Here's the magic: nothing in deque is aware of the discontiguous storage!

The memory setup and layout occurs in the parent, _Base, and the iterator class is entirely responsible for leaping from one node to the next. All the implementation routines for deque itself work only through the start and finish iterators. This keeps the routines simple and sane, and we can use other standard algorithms as well.


Constructor & Destructor Documentation

std::deque::deque ( ) [inline]

Default constructor creates no elements.

Definition at line 771 of file stl_deque.h.

std::deque::deque ( const allocator_type &  __a) [inline, explicit]

Creates a deque with no elements.

Parameters:
aAn allocator object.

Definition at line 779 of file stl_deque.h.

std::deque::deque ( size_type  __n) [inline, explicit]

Creates a deque with default constructed elements.

Parameters:
nThe number of elements to initially create.

This constructor fills the deque with n default constructed elements.

Definition at line 791 of file stl_deque.h.

std::deque::deque ( size_type  __n,
const value_type &  __value,
const allocator_type &  __a = allocator_type() 
) [inline]

Creates a deque with copies of an exemplar element.

Parameters:
nThe number of elements to initially create.
valueAn element to copy.
aAn allocator.

This constructor fills the deque with n copies of value.

Definition at line 803 of file stl_deque.h.

std::deque::deque ( const deque __x) [inline]

Deque copy constructor.

Parameters:
xA deque of identical element and allocator types.

The newly-created deque uses a copy of the allocation object used by x.

Definition at line 830 of file stl_deque.h.

std::deque::deque ( deque &&  __x) [inline]

Deque move constructor.

Parameters:
xA deque of identical element and allocator types.

The newly-created deque contains the exact contents of x. The contents of x are a valid, but unspecified deque.

Definition at line 844 of file stl_deque.h.

std::deque::deque ( initializer_list< value_type >  __l,
const allocator_type &  __a = allocator_type() 
) [inline]

Builds a deque from an initializer list.

Parameters:
lAn initializer_list.
aAn allocator object.

Create a deque consisting of copies of the elements in the initializer_list l.

This will call the element type's copy constructor N times (where N is l.size()) and do no memory reallocation.

Definition at line 858 of file stl_deque.h.

template<typename _InputIterator >
std::deque::deque ( _InputIterator  __first,
_InputIterator  __last,
const allocator_type &  __a = allocator_type() 
) [inline]

Builds a deque from a range.

Parameters:
firstAn input iterator.
lastAn input iterator.
aAn allocator object.

Create a deque consisting of copies of the elements from [first, last).

If the iterators are forward, bidirectional, or random-access, then this will call the elements' copy constructor N times (where N is distance(first,last)) and do no memory reallocation. But if only input iterators are used, then this will do at most 2N calls to the copy constructor, and logN memory reallocations.

Definition at line 883 of file stl_deque.h.

std::deque::~deque ( ) [inline]

The dtor only erases the elements, and note that if the elements themselves are pointers, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

Definition at line 897 of file stl_deque.h.

References std::begin(), and std::end().


Member Function Documentation

void deque::_M_fill_initialize ( const value_type &  __value) [protected]

Fills the deque with copies of value.

Parameters:
valueInitial value.
Returns:
Nothing.
Precondition:
_M_start and _M_finish have already been initialized, but none of the deque's elements have yet been constructed.

This function is called only when the user provides an explicit size (with or without an explicit exemplar value).

Definition at line 335 of file deque.tcc.

References std::_Destroy().

void deque::_M_new_elements_at_back ( size_type  __new_elements) [protected]

Memory-handling helpers for the previous internal insert functions.

Definition at line 829 of file deque.tcc.

References std::size().

void deque::_M_new_elements_at_front ( size_type  __new_elements) [protected]

Memory-handling helpers for the previous internal insert functions.

Definition at line 804 of file deque.tcc.

References std::size().

void deque::_M_pop_back_aux ( ) [protected]

Helper functions for push_* and pop_*.

Definition at line 485 of file deque.tcc.

void deque::_M_pop_front_aux ( ) [protected]

Helper functions for push_* and pop_*.

Definition at line 500 of file deque.tcc.

template<typename... _Args>
void deque::_M_push_back_aux ( _Args &&...  __args) [protected]

Helper functions for push_* and pop_*.

Definition at line 419 of file deque.tcc.

template<typename... _Args>
void deque::_M_push_front_aux ( _Args &&...  __args) [protected]

Helper functions for push_* and pop_*.

Definition at line 453 of file deque.tcc.

void std::deque::_M_range_check ( size_type  __n) const [inline, protected]

Safety check used only from at().

Definition at line 1237 of file stl_deque.h.

References std::size().

template<typename _InputIterator >
void deque::_M_range_initialize ( _InputIterator  __first,
_InputIterator  __last,
std::input_iterator_tag   
) [protected]

Fills the deque with whatever is in [first,last).

Parameters:
firstAn input iterator.
lastAn input iterator.
Returns:
Nothing.

If the iterators are actually forward iterators (or better), then the memory layout can be done all at once. Else we move forward using push_back on each value from the iterator.

Definition at line 361 of file deque.tcc.

template<typename _ForwardIterator >
void deque::_M_range_initialize ( _ForwardIterator  __first,
_ForwardIterator  __last,
std::forward_iterator_tag   
) [protected]

Fills the deque with whatever is in [first,last).

Parameters:
firstAn input iterator.
lastAn input iterator.
Returns:
Nothing.

If the iterators are actually forward iterators (or better), then the memory layout can be done all at once. Else we move forward using push_back on each value from the iterator.

Definition at line 381 of file deque.tcc.

References std::distance(), std::advance(), and std::_Destroy().

void deque::_M_reallocate_map ( size_type  __nodes_to_add,
bool  __add_at_front 
) [protected]

Memory-handling helpers for the major map.

Makes sure the _M_map has space for new nodes. Does not actually add the nodes. Can invalidate _M_map pointers. (And consequently, deque iterators.)

Definition at line 854 of file deque.tcc.

References std::max().

iterator std::deque::_M_reserve_elements_at_back ( size_type  __n) [inline, protected]

Memory-handling helpers for the previous internal insert functions.

Definition at line 1858 of file stl_deque.h.

iterator std::deque::_M_reserve_elements_at_front ( size_type  __n) [inline, protected]

Memory-handling helpers for the previous internal insert functions.

Definition at line 1848 of file stl_deque.h.

void std::deque::_M_reserve_map_at_back ( size_type  __nodes_to_add = 1) [inline, protected]

Memory-handling helpers for the major map.

Makes sure the _M_map has space for new nodes. Does not actually add the nodes. Can invalidate _M_map pointers. (And consequently, deque iterators.)

Definition at line 1884 of file stl_deque.h.

void std::deque::_M_reserve_map_at_front ( size_type  __nodes_to_add = 1) [inline, protected]

Memory-handling helpers for the major map.

Makes sure the _M_map has space for new nodes. Does not actually add the nodes. Can invalidate _M_map pointers. (And consequently, deque iterators.)

Definition at line 1892 of file stl_deque.h.

void std::deque::assign ( size_type  __n,
const value_type &  __val 
) [inline]

Assigns a given value to a deque.

Parameters:
nNumber of elements to be assigned.
valValue to be assigned.

This function fills a deque with n copies of the given value. Note that the assignment completely changes the deque and that the resulting deque's size is the same as the number of elements assigned. Old data may be lost.

Definition at line 958 of file stl_deque.h.

template<typename _InputIterator >
void std::deque::assign ( _InputIterator  __first,
_InputIterator  __last 
) [inline]

Assigns a range to a deque.

Parameters:
firstAn input iterator.
lastAn input iterator.

This function fills a deque with copies of the elements in the range [first,last).

Note that the assignment completely changes the deque and that the resulting deque's size is the same as the number of elements assigned. Old data may be lost.

Definition at line 975 of file stl_deque.h.

void std::deque::assign ( initializer_list< value_type >  __l) [inline]

Assigns an initializer list to a deque.

Parameters:
lAn initializer_list.

This function fills a deque with copies of the elements in the initializer_list l.

Note that the assignment completely changes the deque and that the resulting deque's size is the same as the number of elements assigned. Old data may be lost.

Definition at line 994 of file stl_deque.h.

References assign().

Referenced by assign().

reference std::deque::at ( size_type  __n) [inline]

Provides access to the data contained in the deque.

Parameters:
nThe index of the element for which data should be accessed.
Returns:
Read/write reference to data.
Exceptions:
std::out_of_rangeIf n is an invalid index.

This function provides for safer data access. The parameter is first checked that it is in the range of the deque. The function throws out_of_range if the check fails.

Definition at line 1256 of file stl_deque.h.

const_reference std::deque::at ( size_type  __n) const [inline]

Provides access to the data contained in the deque.

Parameters:
nThe index of the element for which data should be accessed.
Returns:
Read-only (constant) reference to data.
Exceptions:
std::out_of_rangeIf n is an invalid index.

This function provides for safer data access. The parameter is first checked that it is in the range of the deque. The function throws out_of_range if the check fails.

Definition at line 1274 of file stl_deque.h.

reference std::deque::back ( ) [inline]

Returns a read/write reference to the data at the last element of the deque.

Definition at line 1301 of file stl_deque.h.

References std::end().

const_reference std::deque::back ( ) const [inline]

Returns a read-only (constant) reference to the data at the last element of the deque.

Definition at line 1313 of file stl_deque.h.

References std::end().

iterator std::deque::begin ( ) [inline]

Returns a read/write iterator that points to the first element in the deque. Iteration is done in ordinary element order.

Definition at line 1009 of file stl_deque.h.

Referenced by operator=().

const_iterator std::deque::begin ( ) const [inline]

Returns a read-only (constant) iterator that points to the first element in the deque. Iteration is done in ordinary element order.

Definition at line 1017 of file stl_deque.h.

const_iterator std::deque::cbegin ( ) const [inline]

Returns a read-only (constant) iterator that points to the first element in the deque. Iteration is done in ordinary element order.

Definition at line 1080 of file stl_deque.h.

const_iterator std::deque::cend ( ) const [inline]

Returns a read-only (constant) iterator that points one past the last element in the deque. Iteration is done in ordinary element order.

Definition at line 1089 of file stl_deque.h.

void std::deque::clear ( ) [inline]

Erases all the elements. Note that this function only erases the elements, and that if the elements themselves are pointers, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

Definition at line 1579 of file stl_deque.h.

References std::begin().

const_reverse_iterator std::deque::crbegin ( ) const [inline]

Returns a read-only (constant) reverse iterator that points to the last element in the deque. Iteration is done in reverse element order.

Definition at line 1098 of file stl_deque.h.

const_reverse_iterator std::deque::crend ( ) const [inline]

Returns a read-only (constant) reverse iterator that points to one before the first element in the deque. Iteration is done in reverse element order.

Definition at line 1107 of file stl_deque.h.

template<typename... _Args>
deque< _Tp, _Alloc >::iterator deque::emplace ( iterator  __position,
_Args &&...  __args 
)

Inserts an object in deque before specified iterator.

Parameters:
positionAn iterator into the deque.
argsArguments.
Returns:
An iterator that points to the inserted data.

This function will insert an object of type T constructed with T(std::forward<Args>(args)...) before the specified location.

Definition at line 174 of file deque.tcc.

bool std::deque::empty ( ) const [inline]

Returns true if the deque is empty. (Thus begin() would equal end().)

Definition at line 1200 of file stl_deque.h.

iterator std::deque::end ( ) [inline]

Returns a read/write iterator that points one past the last element in the deque. Iteration is done in ordinary element order.

Definition at line 1026 of file stl_deque.h.

Referenced by operator=().

const_iterator std::deque::end ( ) const [inline]

Returns a read-only (constant) iterator that points one past the last element in the deque. Iteration is done in ordinary element order.

Definition at line 1035 of file stl_deque.h.

deque< _Tp, _Alloc >::iterator deque::erase ( iterator  __position)

Remove element at given position.

Parameters:
positionIterator pointing to element to be erased.
Returns:
An iterator pointing to the next element (or end()).

This function will erase the element at the given position and thus shorten the deque by one.

The user is cautioned that this function only erases the element, and that if the element is itself a pointer, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

Definition at line 196 of file deque.tcc.

References std::begin(), std::size(), and std::end().

deque< _Tp, _Alloc >::iterator deque::erase ( iterator  __first,
iterator  __last 
)

Remove a range of elements.

Parameters:
firstIterator pointing to the first element to be erased.
lastIterator pointing to one past the last element to be erased.
Returns:
An iterator pointing to the element pointed to by last prior to erasing (or end()).

This function will erase the elements in the range [first,last) and shorten the deque accordingly.

The user is cautioned that this function only erases the elements, and that if the elements themselves are pointers, the pointed-to memory is not touched in any way. Managing the pointer is the user's responsibility.

Definition at line 219 of file deque.tcc.

References std::begin(), std::end(), and std::size().

reference std::deque::front ( ) [inline]

Returns a read/write reference to the data at the first element of the deque.

Definition at line 1285 of file stl_deque.h.

References std::begin().

const_reference std::deque::front ( ) const [inline]

Returns a read-only (constant) reference to the data at the first element of the deque.

Definition at line 1293 of file stl_deque.h.

References std::begin().

allocator_type std::deque::get_allocator ( ) const [inline]

Get a copy of the memory allocation object.

Reimplemented from std::_Deque_base< _Tp, _Alloc >.

Definition at line 1000 of file stl_deque.h.

deque< _Tp, _Alloc >::iterator deque::insert ( iterator  __position,
const value_type &  __x 
)

Inserts given value into deque before specified iterator.

Parameters:
positionAn iterator into the deque.
xData to be inserted.
Returns:
An iterator that points to the inserted data.

This function will insert a copy of the given value before the specified location.

Definition at line 151 of file deque.tcc.

iterator std::deque::insert ( iterator  __position,
value_type &&  __x 
) [inline]

Inserts given rvalue into deque before specified iterator.

Parameters:
positionAn iterator into the deque.
xData to be inserted.
Returns:
An iterator that points to the inserted data.

This function will insert a copy of the given rvalue before the specified location.

Definition at line 1464 of file stl_deque.h.

void std::deque::insert ( iterator  __p,
initializer_list< value_type >  __l 
) [inline]

Inserts an initializer list into the deque.

Parameters:
pAn iterator into the deque.
lAn initializer_list.

This function will insert copies of the data in the initializer_list l into the deque before the location specified by p. This is known as list insert.

Definition at line 1477 of file stl_deque.h.

References insert().

Referenced by insert().

void std::deque::insert ( iterator  __position,
size_type  __n,
const value_type &  __x 
) [inline]

Inserts a number of copies of given data into the deque.

Parameters:
positionAn iterator into the deque.
nNumber of elements to be inserted.
xData to be inserted.

This function will insert a specified number of copies of the given data before the location specified by position.

Definition at line 1491 of file stl_deque.h.

template<typename _InputIterator >
void std::deque::insert ( iterator  __position,
_InputIterator  __first,
_InputIterator  __last 
) [inline]

Inserts a range into the deque.

Parameters:
positionAn iterator into the deque.
firstAn input iterator.
lastAn input iterator.

This function will insert copies of the data in the range [first,last) into the deque before the location specified by pos. This is known as range insert.

Definition at line 1506 of file stl_deque.h.

size_type std::deque::max_size ( ) const [inline]

Returns the size() of the largest possible deque.

Definition at line 1119 of file stl_deque.h.

deque< _Tp, _Alloc > & deque::operator= ( const deque __x)

Deque assignment operator.

Parameters:
xA deque of identical element and allocator types.

All the elements of x are copied, but unlike the copy constructor, the allocator object is not copied.

Definition at line 95 of file deque.tcc.

References std::size(), size(), begin(), and end().

deque& std::deque::operator= ( deque &&  __x) [inline]

Deque move assignment operator.

Parameters:
xA deque of identical element and allocator types.

The contents of x are moved into this deque (without copying). x is a valid, but unspecified deque.

Definition at line 919 of file stl_deque.h.

deque& std::deque::operator= ( initializer_list< value_type >  __l) [inline]

Assigns an initializer list to a deque.

Parameters:
lAn initializer_list.

This function fills a deque with copies of the elements in the initializer_list l.

Note that the assignment completely changes the deque and that the resulting deque's size is the same as the number of elements assigned. Old data may be lost.

Definition at line 940 of file stl_deque.h.

reference std::deque::operator[] ( size_type  __n) [inline]

Subscript access to the data contained in the deque.

Parameters:
nThe index of the element for which data should be accessed.
Returns:
Read/write reference to data.

This operator allows for easy, array-style, data access. Note that data access with this operator is unchecked and out_of_range lookups are not defined. (For checked lookups see at().)

Definition at line 1216 of file stl_deque.h.

const_reference std::deque::operator[] ( size_type  __n) const [inline]

Subscript access to the data contained in the deque.

Parameters:
nThe index of the element for which data should be accessed.
Returns:
Read-only (constant) reference to data.

This operator allows for easy, array-style, data access. Note that data access with this operator is unchecked and out_of_range lookups are not defined. (For checked lookups see at().)

Definition at line 1231 of file stl_deque.h.

void std::deque::pop_back ( ) [inline]

Removes last element.

This is a typical stack operation. It shrinks the deque by one.

Note that no data is returned, and if the last element's data is needed, it should be retrieved before pop_back() is called.

Definition at line 1414 of file stl_deque.h.

void std::deque::pop_front ( ) [inline]

Removes first element.

This is a typical stack operation. It shrinks the deque by one.

Note that no data is returned, and if the first element's data is needed, it should be retrieved before pop_front() is called.

Definition at line 1393 of file stl_deque.h.

void std::deque::push_back ( const value_type &  __x) [inline]

Add data to the end of the deque.

Parameters:
xData to be added.

This is a typical stack operation. The function creates an element at the end of the deque and assigns the given data to it. Due to the nature of a deque this operation can be done in constant time.

Definition at line 1362 of file stl_deque.h.

void std::deque::push_front ( const value_type &  __x) [inline]

Add data to the front of the deque.

Parameters:
xData to be added.

This is a typical stack operation. The function creates an element at the front of the deque and assigns the given data to it. Due to the nature of a deque this operation can be done in constant time.

Definition at line 1331 of file stl_deque.h.

reverse_iterator std::deque::rbegin ( ) [inline]

Returns a read/write reverse iterator that points to the last element in the deque. Iteration is done in reverse element order.

Definition at line 1044 of file stl_deque.h.

const_reverse_iterator std::deque::rbegin ( ) const [inline]

Returns a read-only (constant) reverse iterator that points to the last element in the deque. Iteration is done in reverse element order.

Definition at line 1053 of file stl_deque.h.

reverse_iterator std::deque::rend ( ) [inline]

Returns a read/write reverse iterator that points to one before the first element in the deque. Iteration is done in reverse element order.

Definition at line 1062 of file stl_deque.h.

const_reverse_iterator std::deque::rend ( ) const [inline]

Returns a read-only (constant) reverse iterator that points to one before the first element in the deque. Iteration is done in reverse element order.

Definition at line 1071 of file stl_deque.h.

void std::deque::resize ( size_type  __new_size) [inline]

Resizes the deque to the specified number of elements.

Parameters:
new_sizeNumber of elements the deque should contain.

This function will resize the deque to the specified number of elements. If the number is smaller than the deque's current size the deque is truncated, otherwise default constructed elements are appended.

Definition at line 1133 of file stl_deque.h.

References std::size().

void std::deque::resize ( size_type  __new_size,
const value_type &  __x 
) [inline]

Resizes the deque to the specified number of elements.

Parameters:
new_sizeNumber of elements the deque should contain.
xData with which new elements should be populated.

This function will resize the deque to the specified number of elements. If the number is smaller than the deque's current size the deque is truncated, otherwise the deque is extended and new elements are populated with given data.

Definition at line 1155 of file stl_deque.h.

References std::size().

void std::deque::shrink_to_fit ( ) [inline]

A non-binding request to reduce memory use.

Definition at line 1191 of file stl_deque.h.

size_type std::deque::size ( ) const [inline]

Returns the number of elements in the deque.

Definition at line 1114 of file stl_deque.h.

Referenced by operator=().

void std::deque::swap ( deque __x) [inline]

Swaps data with another deque.

Parameters:
xA deque of the same element and allocator types.

This exchanges the elements between two deques in constant time. (Four pointers, so it should be quite fast.) Note that the global std::swap() function is specialized such that std::swap(d1,d2) will feed to this function.

Definition at line 1559 of file stl_deque.h.


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