concurrent_vector Class

Artikel
08/03/2021

The concurrent_vector class is a sequence container class that allows random access to any element. It enables concurrency-safe append, element access, iterator access, and iterator traversal operations. Here, concurrency-safe means pointers or iterators are always valid. It's not a guarantee of element initialization, or of a particular traversal order.

Syntax

template<typename T, class _Ax>
class concurrent_vector: protected details::_Allocator_base<T,
    _Ax>,
private details::_Concurrent_vector_base_v4;

Parameters

T
The data type of the elements to be stored in the vector.

_Ax
The type that represents the stored allocator object that encapsulates details about the allocation and deallocation of memory for the concurrent vector. This argument is optional and the default value is allocator<T>.

Members

Public Typedefs

Name	Description
`allocator_type`	A type that represents the allocator class for the concurrent vector.
`const_iterator`	A type that provides a random-access iterator that can read a `const` element in a concurrent vector.
`const_pointer`	A type that provides a pointer to a `const` element in a concurrent vector.
`const_reference`	A type that provides a reference to a `const` element stored in a concurrent vector for reading and performing `const` operations.
`const_reverse_iterator`	A type that provides a random-access iterator that can read any `const` element in the concurrent vector.
`difference_type`	A type that provides the signed distance between two elements in a concurrent vector.
`iterator`	A type that provides a random-access iterator that can read any element in a concurrent vector. Modification of an element using the iterator is not concurrency-safe.
`pointer`	A type that provides a pointer to an element in a concurrent vector.
`reference`	A type that provides a reference to an element stored in a concurrent vector.
`reverse_iterator`	A type that provides a random-access iterator that can read any element in a reversed concurrent vector. Modification of an element using the iterator is not concurrency-safe.
`size_type`	A type that counts the number of elements in a concurrent vector.
`value_type`	A type that represents the data type stored in a concurrent vector.

Public Constructors

Name	Description
concurrent_vector	Overloaded. Constructs a concurrent vector.
~concurrent_vector Destructor	Erases all elements and destroys this concurrent vector.

Public Methods

Name	Description
assign	Overloaded. Erases the elements of the concurrent vector and assigns to it either `_N` copies of `_Item`, or values specified by the iterator range [ `_Begin`, `_End`). This method is not concurrency-safe.
at	Overloaded. Provides access to the element at the given index in the concurrent vector. This method is concurrency-safe for read operations, and also while growing the vector, as long as you have ensured that the value `_Index` is less than the size of the concurrent vector.
back	Overloaded. Returns a reference or a `const` reference to the last element in the concurrent vector. If the concurrent vector is empty, the return value is undefined. This method is concurrency-safe.
begin	Overloaded. Returns an iterator of type `iterator` or `const_iterator` to the beginning of the concurrent vector. This method is concurrency-safe.
capacity	Returns the maximum size to which the concurrent vector can grow without having to allocate more memory. This method is concurrency-safe.
cbegin	Returns an iterator of type `const_iterator` to the beginning of the concurrent vector. This method is concurrency-safe.
cend	Returns an iterator of type `const_iterator` to the end of the concurrent vector. This method is concurrency-safe.
clear	Erases all elements in the concurrent vector. This method is not concurrency-safe.
crbegin	Returns an iterator of type `const_reverse_iterator` to the beginning of the concurrent vector. This method is concurrency-safe.
crend	Returns an iterator of type `const_reverse_iterator` to the end of the concurrent vector. This method is concurrency-safe.
empty	Tests if the concurrent vector is empty at the time this method is called. This method is concurrency-safe.
end	Overloaded. Returns an iterator of type `iterator` or `const_iterator` to the end of the concurrent vector. This method is concurrency-safe.
front	Overloaded. Returns a reference or a `const` reference to the first element in the concurrent vector. If the concurrent vector is empty, the return value is undefined. This method is concurrency-safe.
get_allocator	Returns a copy of the allocator used to construct the concurrent vector. This method is concurrency-safe.
grow_by	Overloaded. Grows this concurrent vector by `_Delta` elements. This method is concurrency-safe.
grow_to_at_least	Grows this concurrent vector until it has at least `_N` elements. This method is concurrency-safe.
max_size	Returns the maximum number of elements the concurrent vector can hold. This method is concurrency-safe.
push_back	Overloaded. Appends the given item to the end of the concurrent vector. This method is concurrency-safe.
rbegin	Overloaded. Returns an iterator of type `reverse_iterator` or `const_reverse_iterator` to the beginning of the concurrent vector. This method is concurrency-safe.
rend	Overloaded. Returns an iterator of type `reverse_iterator` or `const_reverse_iterator` to the end of the concurrent vector. This method is concurrency-safe.
reserve	Allocates enough space to grow the concurrent vector to size `_N` without having to allocate more memory later. This method is not concurrency-safe.
resize	Overloaded. Changes the size of the concurrent vector to the requested size, deleting or adding elements as necessary. This method is not concurrency-safe.
shrink_to_fit	Compacts the internal representation of the concurrent vector to reduce fragmentation and optimize memory usage. This method is not concurrency-safe.
size	Returns the number of elements in the concurrent vector. This method is concurrency-safe.
swap	Swaps the contents of two concurrent vectors. This method is not concurrency-safe.

Public Operators

Name	Description
operator[]	Overloaded. Provides access to the element at the given index in the concurrent vector. This method is concurrency-safe for read operations, and also while growing the vector, as long as the you have ensured that the value `_Index` is less than the size of the concurrent vector.
operator=	Overloaded. Assigns the contents of another `concurrent_vector` object to this one. This method is not concurrency-safe.

Remarks

For detailed information on the concurrent_vector class, see Parallel Containers and Objects.

Inheritance Hierarchy

_Concurrent_vector_base_v4

_Allocator_base

concurrent_vector

Requirements

Header: concurrent_vector.h

Namespace: concurrency

assign

Erases the elements of the concurrent vector and assigns to it either _N copies of _Item, or values specified by the iterator range [ _Begin, _End). This method is not concurrency-safe.

void assign(
    size_type _N,
    const_reference _Item);

template<class _InputIterator>
void assign(_InputIterator _Begin,
    _InputIterator _End);

Parameters

_InputIterator
The type of the specified iterator.

_N
The number of items to copy into the concurrent vector.

_Item
Reference to a value used to fill the concurrent vector.

_Begin
An iterator to the first element of the source range.

_End
An iterator to one past the last element of the source range.

Remarks

assign is not concurrency-safe. You must ensure that no other threads are invoking methods on the concurrent vector when you call this method.

at

Provides access to the element at the given index in the concurrent vector. This method is concurrency-safe for read operations, and also while growing the vector, as long as you have ensured that the value _Index is less than the size of the concurrent vector.

reference at(size_type _Index);

const_reference at(size_type _Index) const;

Parameters

_Index
The index of the element to be retrieved.

Return Value

A reference to the item at the given index.

Remarks

The version of the function at that returns a non- const reference cannot be used to concurrently write to the element from different threads. A different synchronization object should be used to synchronize concurrent read and write operations to the same data element.

The method throws out_of_range if _Index is greater than or equal to the size of the concurrent vector, and range_error if the index is for a broken portion of the vector. For details on how a vector can become broken, see Parallel Containers and Objects.

back

Returns a reference or a const reference to the last element in the concurrent vector. If the concurrent vector is empty, the return value is undefined. This method is concurrency-safe.

reference back();

const_reference back() const;

Return Value

A reference or a const reference to the last element in the concurrent vector.

begin

Returns an iterator of type iterator or const_iterator to the beginning of the concurrent vector. This method is concurrency-safe.

iterator begin();

const_iterator begin() const;

Return Value

An iterator of type iterator or const_iterator to the beginning of the concurrent vector.

capacity

Returns the maximum size to which the concurrent vector can grow without having to allocate more memory. This method is concurrency-safe.

size_type capacity() const;

Return Value

The maximum size to which the concurrent vector can grow without having to allocate more memory.

Remarks

Unlike a C++ Standard Library vector, a concurrent_vector object does not move existing elements if it allocates more memory.

cbegin

Returns an iterator of type const_iterator to the beginning of the concurrent vector. This method is concurrency-safe.

const_iterator cbegin() const;

Return Value

An iterator of type const_iterator to the beginning of the concurrent vector.

cend

Returns an iterator of type const_iterator to the end of the concurrent vector. This method is concurrency-safe.

const_iterator cend() const;

Return Value

An iterator of type const_iterator to the end of the concurrent vector.

clear

Erases all elements in the concurrent vector. This method is not concurrency-safe.

void clear();

Remarks

clear is not concurrency-safe. You must ensure that no other threads are invoking methods on the concurrent vector when you call this method. clear does not free internal arrays. To free internal arrays, call the function shrink_to_fit after clear.

concurrent_vector

Constructs a concurrent vector.

explicit concurrent_vector(
    const allocator_type& _Al = allocator_type());

concurrent_vector(
    const concurrent_vector& _Vector);

template<class M>
concurrent_vector(
    const concurrent_vector<T,
    M>& _Vector,
    const allocator_type& _Al = allocator_type());

concurrent_vector(
    concurrent_vector&& _Vector);

explicit concurrent_vector(
    size_type _N);

concurrent_vector(
    size_type _N,
    const_reference _Item,
    const allocator_type& _Al = allocator_type());

template<class _InputIterator>
concurrent_vector(_InputIterator _Begin,
    _InputIterator _End,
    const allocator_type& _Al = allocator_type());

Parameters

M
The allocator type of the source vector.

_InputIterator
The type of the input iterator.

_Al
The allocator class to use with this object.

_Vector
The source concurrent_vector object to copy or move elements from.

_N
The initial capacity of the concurrent_vector object.

_Item
The value of elements in the constructed object.

_Begin
Position of the first element in the range of elements to be copied.

_End
Position of the first element beyond the range of elements to be copied.

Remarks

All constructors store an allocator object _Al and initialize the vector.

The first constructor specify an empty initial vector and explicitly specifies the allocator type. to be used.

The second and third constructors specify a copy of the concurrent vector _Vector.

The fourth constructor specifies a move of the concurrent vector _Vector.

The fifth constructor specifies a repetition of a specified number ( _N) of elements of the default value for class T.

The sixth constructor specifies a repetition of ( _N) elements of value _Item.

The last constructor specifies values supplied by the iterator range [ _Begin, _End).

~concurrent_vector

Erases all elements and destroys this concurrent vector.

~concurrent_vector();

crbegin

Returns an iterator of type const_reverse_iterator to the beginning of the concurrent vector. This method is concurrency-safe.

const_reverse_iterator crbegin() const;

Return Value

An iterator of type const_reverse_iterator to the beginning of the concurrent vector.

crend

Returns an iterator of type const_reverse_iterator to the end of the concurrent vector. This method is concurrency-safe.

const_reverse_iterator crend() const;

Return Value

An iterator of type const_reverse_iterator to the end of the concurrent vector.

empty

Tests if the concurrent vector is empty at the time this method is called. This method is concurrency-safe.

bool empty() const;

Return Value

true if the vector was empty at the moment the function was called, false otherwise.

end

Returns an iterator of type iterator or const_iterator to the end of the concurrent vector. This method is concurrency-safe.

iterator end();

const_iterator end() const;

Return Value

An iterator of type iterator or const_iterator to the end of the concurrent vector.

front

Returns a reference or a const reference to the first element in the concurrent vector. If the concurrent vector is empty, the return value is undefined. This method is concurrency-safe.

reference front();

const_reference front() const;

Return Value

A reference or a const reference to the first element in the concurrent vector.

get_allocator

Returns a copy of the allocator used to construct the concurrent vector. This method is concurrency-safe.

allocator_type get_allocator() const;

Return Value

A copy of the allocator used to construct the concurrent_vector object.

grow_by

Grows this concurrent vector by _Delta elements. This method is concurrency-safe.

iterator grow_by(
    size_type _Delta);

iterator grow_by(
    size_type _Delta,
    const_reference _Item);

Parameters

_Delta
The number of elements to append to the object.

_Item
The value to initialize the new elements with.

Return Value

An iterator to first item appended.

Remarks

If _Item is not specified, the new elements are default constructed.

grow_to_at_least

Grows this concurrent vector until it has at least _N elements. This method is concurrency-safe.

iterator grow_to_at_least(size_type _N);

Parameters

_N
The new minimum size for the concurrent_vector object.

Return Value

An iterator that points to beginning of appended sequence, or to the element at index _N if no elements were appended.

max_size

Returns the maximum number of elements the concurrent vector can hold. This method is concurrency-safe.

size_type max_size() const;

Return Value

The maximum number of elements the concurrent_vector object can hold.

operator=

Assigns the contents of another concurrent_vector object to this one. This method is not concurrency-safe.

concurrent_vector& operator= (
    const concurrent_vector& _Vector);

template<class M>
concurrent_vector& operator= (
    const concurrent_vector<T, M>& _Vector);

concurrent_vector& operator= (
    concurrent_vector&& _Vector);

Parameters

M
The allocator type of the source vector.

_Vector
The source concurrent_vector object.

Return Value

A reference to this concurrent_vector object.

operator[]

Provides access to the element at the given index in the concurrent vector. This method is concurrency-safe for read operations, and also while growing the vector, as long as the you have ensured that the value _Index is less than the size of the concurrent vector.

reference operator[](size_type _index);

const_reference operator[](size_type _index) const;

Parameters

_Index
The index of the element to be retrieved.

Return Value

A reference to the item at the given index.

Remarks

The version of operator [] that returns a non- const reference cannot be used to concurrently write to the element from different threads. A different synchronization object should be used to synchronize concurrent read and write operations to the same data element.

No bounds checking is performed to ensure that _Index is a valid index into the concurrent vector.

push_back

Appends the given item to the end of the concurrent vector. This method is concurrency-safe.

iterator push_back(const_reference _Item);

iterator push_back(T&& _Item);

Parameters

_Item
The value to be appended.

Return Value

An iterator to item appended.

rbegin

Returns an iterator of type reverse_iterator or const_reverse_iterator to the beginning of the concurrent vector. This method is concurrency-safe.

reverse_iterator rbegin();

const_reverse_iterator rbegin() const;

Return Value

An iterator of type reverse_iterator or const_reverse_iterator to the beginning of the concurrent vector.

rend

Returns an iterator of type reverse_iterator or const_reverse_iterator to the end of the concurrent vector. This method is concurrency-safe.

reverse_iterator rend();

const_reverse_iterator rend() const;

Return Value

An iterator of type reverse_iterator or const_reverse_iterator to the end of the concurrent vector.

reserve

Allocates enough space to grow the concurrent vector to size _N without having to allocate more memory later. This method is not concurrency-safe.

void reserve(size_type _N);

Parameters

_N
The number of elements to reserve space for.

Remarks

reserve is not concurrency-safe. You must ensure that no other threads are invoking methods on the concurrent vector when you call this method. The capacity of the concurrent vector after the method returns may be bigger than the requested reservation.

resize

Changes the size of the concurrent vector to the requested size, deleting or adding elements as necessary. This method is not concurrency-safe.

void resize(
    size_type _N);

void resize(
    size_type _N,
    const T& val);

Parameters

_N
The new size of the concurrent_vector.

val
The value of new elements added to the vector if the new size is larger than the original size. If the value is omitted, the new objects are assigned the default value for their type.

Remarks

If the size of the container is less than the requested size, elements are added to the vector until it reaches the requested size. If the size of the container is larger than the requested size, the elements closest to the end of the container are deleted until the container reaches the size _N. If the present size of the container is the same as the requested size, no action is taken.

resize is not concurrency safe. You must ensure that no other threads are invoking methods on the concurrent vector when you call this method.

shrink_to_fit

Compacts the internal representation of the concurrent vector to reduce fragmentation and optimize memory usage. This method is not concurrency-safe.

void shrink_to_fit();

Remarks

This method will internally re-allocate memory move elements around, invalidating all the iterators. shrink_to_fit is not concurrency-safe. You must ensure that no other threads are invoking methods on the concurrent vector when you call this function.

size

Returns the number of elements in the concurrent vector. This method is concurrency-safe.

size_type size() const;

Return Value

The number of elements in this concurrent_vector object.

Remarks

The returned size is guaranteed to include all elements appended by calls to the function push_back, or grow operations that have completed prior to invoking this method. However, it may also include elements that are allocated but still under construction by concurrent calls to any of the growth methods.

swap

Swaps the contents of two concurrent vectors. This method is not concurrency-safe.

void swap(concurrent_vector& _Vector);

Parameters

_Vector
The concurrent_vector object to swap contents with.

Dela via

concurrent_vector Class

Syntax

Parameters

Members

Public Typedefs

Public Constructors

Public Methods

Public Operators

Remarks

Inheritance Hierarchy

Requirements

assign

Parameters

Remarks

at

Parameters

Return Value

Remarks

back

Return Value

begin

Return Value

capacity

Return Value

Remarks

cbegin

Return Value

cend

Return Value

clear

Remarks

concurrent_vector

Parameters

Remarks

~concurrent_vector

crbegin

Return Value

crend

Return Value

empty

Return Value

end

Return Value

front

Return Value

get_allocator

Return Value

grow_by

Parameters

Return Value

Remarks

grow_to_at_least

Parameters

Return Value

max_size

Return Value

operator=

Parameters

Return Value

operator[]

Parameters

Return Value

Remarks

push_back

Parameters

Return Value

rbegin

Return Value

rend

Return Value

reserve

Parameters

Remarks

resize

Parameters

Remarks

shrink_to_fit

Remarks

size