Space Optimized Circular Buffer

circular_buffer_space_optimized<T, Alloc>

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Contents

Description
Synopsis
Rationale
Header Files
Modelled concepts
Specific Public Types
Constructors and Destructor
Specific Public Member Functions
See also
Acknowledgements
Release Notes

Description

The circular_buffer_space_optimized container is an adaptor of the circular_buffer. The functionality of the circular_buffer_space_optimized is similar to the base circular_buffer except it does not allocate memory at once when created rather it allocates memory as needed. (The predictive memory allocation is similar to typical std::vector implementation.) Moreover the memory is automatically freed as the size of the container decreases.

Space Optimized Circular Buffer
Figure: The memory allocation process of the space optimized circular buffer. The min_capacity() of the capacity controller represents the minimal guaranteed amount of allocated memory. The allocated memory will never drop under this value. The default value of the min_capacity() is set to 0.

Synopsis

Note that some of the links point to the original circular_buffer if the functionality is the same. 

namespace boost {

template <class T, class Alloc>
class circular_buffer_space_optimized
{
public:
   typedef typename Alloc::value_type value_type;
   typedef typename Alloc::pointer pointer;
   typedef typename Alloc::const_pointer const_pointer;
   typedef typename Alloc::reference reference;
   typedef typename Alloc::const_reference const_reference;
   typedef typename Alloc::size_type size_type;
   typedef typename Alloc::difference_type difference_type;
   typedef Alloc allocator_type;
   typedef implementation-defined const_iterator;
   typedef implementation-defined iterator;
   typedef boost::reverse_iterator<const_iterator> const_reverse_iterator;
   typedef boost::reverse_iterator<iterator> reverse_iterator;
   typedef std::pair<pointer, size_type> array_range;
   typedef std::pair<const_pointer, size_type> const_array_range;
   typedef implementation-defined capacity_type;

   explicit circular_buffer_space_optimized(const allocator_type& alloc = allocator_type());
   explicit circular_buffer_space_optimized(capacity_type capacity_ctrl, const allocator_type& alloc = allocator_type());
   circular_buffer_space_optimized(capacity_type capacity_ctrl, const_reference item, const allocator_type& alloc = allocator_type());
   circular_buffer_space_optimized(capacity_type capacity_ctrl, size_type n, const_reference item, const allocator_type& alloc = allocator_type());
   circular_buffer_space_optimized(const circular_buffer_space_optimized<T, Alloc>& cb);
   template <class InputIterator>
      circular_buffer_space_optimized(InputIterator first, InputIterator last, const allocator_type& alloc = allocator_type());
   template <class InputIterator>
      circular_buffer_space_optimized(capacity_type capacity_ctrl, InputIterator first, InputIterator last, const allocator_type& alloc = allocator_type());
   ~circular_buffer_space_optimized();

   allocator_type get_allocator() const;
   allocator_type& get_allocator();
   iterator begin();
   iterator end();
   const_iterator begin() const;
   const_iterator end() const;
   reverse_iterator rbegin();
   reverse_iterator rend();
   const_reverse_iterator rbegin() const;
   const_reverse_iterator rend() const;
   reference operator[](size_type index);
   const_reference operator[](size_type index) const;
   reference at(size_type index);
   const_reference at(size_type index) const;
   reference front();
   reference back();
   const_reference front() const;
   const_reference back() const;
   array_range array_one();
   array_range array_two();
   const_array_range array_one() const;
   const_array_range array_two() const;
   pointer linearize();
   bool is_linearized() const;
   void rotate(const_iterator new_begin);
   size_type size() const;
   size_type max_size() const;
   bool empty() const;
   bool full() const;
   size_type reserve() const;
   const capacity_type& capacity() const;
   void set_capacity(const capacity_type& capacity_ctrl);
   void resize(size_type new_size, const_reference item = value_type());
   void rset_capacity(const capacity_type& capacity_ctrl);
   void rresize(size_type new_size, const_reference item = value_type());
   circular_buffer_space_optimized<T, Alloc>& operator=(const circular_buffer_space_optimized<T, Alloc>& cb);
   void assign(size_type n, const_reference item);
   void assign(capacity_type capacity_ctrl, size_type n, const_reference item);
   template <class InputIterator>
      void assign(InputIterator first, InputIterator last);
   template <class InputIterator>
      void assign(capacity_type capacity_ctrl, InputIterator first, InputIterator last);
   void swap(circular_buffer_space_optimized<T, Alloc>& cb);
   void push_back(const_reference item = value_type());
   void push_front(const_reference item = value_type());
   void pop_back();
   void pop_front();
   iterator insert(iterator pos, const_reference item = value_type());
   void insert(iterator pos, size_type n, const_reference item);
   template <class InputIterator>
      void insert(iterator pos, InputIterator first, InputIterator last);
   iterator rinsert(iterator pos, const_reference item = value_type());
   void rinsert(iterator pos, size_type n, const_reference item);
   template <class InputIterator>
      void rinsert(iterator pos, InputIterator first, InputIterator last);
   iterator erase(iterator pos);
   iterator erase(iterator first, iterator last);
   iterator rerase(iterator pos);
   iterator rerase(iterator first, iterator last);
   void clear();
};

template <class T, class Alloc>
   bool operator==(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   bool operator<(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   bool operator!=(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   bool operator>(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   bool operator<=(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   bool operator>=(const circular_buffer_space_optimized<T, Alloc>& lhs, const circular_buffer_space_optimized<T, Alloc>& rhs);
template <class T, class Alloc>
   void swap(circular_buffer_space_optimized<T, Alloc>& lhs, circular_buffer_space_optimized<T, Alloc>& rhs);

} // namespace boost

Rationale

The auto-resizing mode of the space optimized circular buffer can be useful in situations when the container can possibly store large number of elements but most of its lifetime the container stores just few of them. The usage of the circular_buffer_space_optimized will result in decreased memory consumption and can improve the CPU cache effectiveness.

Header Files

The circular_buffer_space_optimized is defined in the file boost/circular_buffer.hpp. There is also a forward declaration for the circular_buffer_space_optimized in the header file boost/circular_buffer_fwd.hpp.

Modelled concepts

Random Access Container, Front Insertion Sequence and Back Insertion Sequence.

Specific Public Types

Following public types are specific to the circular_buffer_space_optimized. Description of the public types common with the circular_buffer can be found in the circular_buffer's documentation.

Type Description
capacity_type Capacity controller of the space optimized circular buffer. 
class capacity_control {
   size_type m_capacity;
   size_type m_min_capacity;
public:
   capacity_control(size_type capacity, size_type min_capacity = 0) : m_capacity(capacity), m_min_capacity(min_capacity) {};
   size_type capacity() const { return m_capacity; }
   size_type min_capacity() const { return m_min_capacity; }
   operator size_type() const { return m_capacity; }
};
Precondition:
capacity >= min_capacity
The capacity() represents the capacity of the circular_buffer_space_optimized and the min_capacity() determines the minimal allocated size of its internal buffer. The converting constructor of the capacity_control allows implicit conversion from size_type-like types which ensures compatibility of creating an instance of the circular_buffer_space_optimized with other STL containers. On the other hand the operator size_type() provides implicit conversion to the size_type which allows to treat the capacity of the circular_buffer_space_optimized the same way as in the circular_buffer.

Constructors and Destructor

explicit circular_buffer_space_optimized(const allocator_type& alloc = allocator_type());

Create an empty space optimized circular buffer with zero capacity.
Effect:
capacity().capacity() == 0 && capacity().min_capacity() == 0 && size() == 0
Parameter(s):
alloc
The allocator.
Throws:
Nothing.
Complexity:
Constant.
Warning:
Since Boost version 1.36 the behaviour of this constructor has changed. Now it creates a space optimized circular buffer with zero capacity.
explicit circular_buffer_space_optimized(capacity_type capacity_ctrl, const allocator_type& alloc = allocator_type());

Create an empty space optimized circular buffer with the specified capacity.
Effect:
capacity() == capacity_ctrl && size() == 0

The amount of allocated memory in the internal buffer is capacity_ctrl.min_capacity().
Parameter(s):
capacity_ctrl
The capacity controller representing the maximum number of elements which can be stored in the circular_buffer_space_optimized and the minimal allocated size of the internal buffer.
alloc
The allocator.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Complexity:
Constant.
circular_buffer_space_optimized(capacity_type capacity_ctrl, const_reference item, const allocator_type& alloc = allocator_type());

Create a full space optimized circular buffer with the specified capacity filled with capacity_ctrl.capacity() copies of item.
Effect:
capacity() == capacity_ctrl && full() && (*this)[0] == item && (*this)[1] == item && ... && (*this) [capacity_ctrl.capacity() - 1] == item

The amount of allocated memory in the internal buffer is capacity_ctrl.capacity().
Parameter(s):
capacity_ctrl
The capacity controller representing the maximum number of elements which can be stored in the circular_buffer_space_optimized and the minimal allocated size of the internal buffer.
item
The element the created circular_buffer_space_optimized will be filled with.
alloc
The allocator.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Complexity:
Linear (in the capacity_ctrl.capacity()).
circular_buffer_space_optimized(capacity_type capacity_ctrl, size_type n, const_reference item, const allocator_type& alloc = allocator_type());

Create a space optimized circular buffer with the specified capacity filled with n copies of item.
Precondition:
capacity_ctrl.capacity() >= n
Effect:
capacity() == capacity_ctrl && size() == n && (*this)[0] == item && (*this)[1] == item && ... && (*this)[n - 1] == item

The amount of allocated memory in the internal buffer is max[n, capacity_ctrl.min_capacity()].
Parameter(s):
capacity_ctrl
The capacity controller representing the maximum number of elements which can be stored in the circular_buffer_space_optimized and the minimal allocated size of the internal buffer.
n
The number of elements the created circular_buffer_space_optimized will be filled with.
item
The element the created circular_buffer_space_optimized will be filled with.
alloc
The allocator.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Complexity:
Linear (in the n).
circular_buffer_space_optimized(const circular_buffer_space_optimized<T,Alloc>& cb);

The copy constructor.

Creates a copy of the specified circular_buffer_space_optimized.

Effect:
*this == cb

The amount of allocated memory in the internal buffer is cb.size().
Parameter(s):
cb
The circular_buffer_space_optimized to be copied.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Complexity:
Linear (in the size of cb).
template <class InputIterator>
circular_buffer_space_optimized(InputIterator first, InputIterator last, const allocator_type& alloc = allocator_type());

Create a full space optimized circular buffer filled with a copy of the range.
Precondition:
Valid range [first, last).
first and last have to meet the requirements of InputIterator.
Effect:
capacity().capacity() == std::distance(first, last) && capacity().min_capacity() == 0 && full() && (*this)[0]== *first && (*this)[1] == *(first + 1) && ... && (*this)[std::distance(first, last) - 1] == *(last - 1)

The amount of allocated memory in the internal buffer is std::distance(first, last).
Parameter(s):
first
The beginning of the range to be copied.
last
The end of the range to be copied.
alloc
The allocator.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Complexity:
Linear (in the std::distance(first, last)).
template <class InputIterator>
circular_buffer_space_optimized(capacity_type capacity_ctrl, InputIterator first, InputIterator last, const allocator_type& alloc = allocator_type());

Create a space optimized circular buffer with the specified capacity (and the minimal guaranteed amount of allocated memory) filled with a copy of the range.
Precondition:
Valid range [first, last).
first and last have to meet the requirements of InputIterator.
Effect:
capacity() == capacity_ctrl && size() <= std::distance(first, last) && (*this)[0]== (last - capacity_ctrl.capacity()) && (*this)[1] == *(last - capacity_ctrl.capacity() + 1) && ... && (*this)[capacity_ctrl.capacity() - 1] == *(last - 1)

If the number of items to be copied from the range [first, last) is greater than the specified capacity_ctrl.capacity() then only elements from the range [last - capacity_ctrl.capacity(), last) will be copied.

The amount of allocated memory in the internal buffer is max[capacity_ctrl.min_capacity(), min[capacity_ctrl.capacity(), std::distance(first, last)]].
Parameter(s):
capacity_ctrl
The capacity controller representing the maximum number of elements which can be stored in the circular_buffer_space_optimized and the minimal allocated size of the internal buffer.
first
The beginning of the range to be copied.
last
The end of the range to be copied.
alloc
The allocator.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Complexity:
Linear (in std::distance(first, last); in min[capacity_ctrl.capacity(), std::distance(first, last)] if the InputIterator is a RandomAccessIterator).
~circular_buffer_space_optimized();

The destructor.

Destroys the circular_buffer_space_optimized.

Throws:
Nothing.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (including iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
clear()

Specific Public Member Functions

Following public member functions of the circular_buffer_space_optimized have different behaviour from the base circular_buffer. Description of the public member functions with the same behaviour can be found in the circular_buffer's documentation.

bool full() const;

Is the circular_buffer_space_optimized full?
Returns:
true if the number of elements stored in the circular_buffer_space_optimized equals the capacity of the circular_buffer_space_optimized; false otherwise.
Throws:
Nothing.
Exception Safety:
No-throw.
Iterator Invalidation:
Does not invalidate any iterators.
Complexity:
Constant (in the size of the circular_buffer_space_optimized).
See Also:
empty()
size_type reserve() const;

Get the maximum number of elements which can be inserted into the circular_buffer_space_optimized without overwriting any of already stored elements.
Returns:
capacity().capacity() - size()
Throws:
Nothing.
Exception Safety:
No-throw.
Iterator Invalidation:
Does not invalidate any iterators.
Complexity:
Constant (in the size of the circular_buffer_space_optimized).
See Also:
capacity(), size(), max_size()
const capacity_type& capacity() const;

Get the capacity of the circular_buffer_space_optimized.
Returns:
The capacity controller representing the maximum number of elements which can be stored in the circular_buffer_space_optimized and the minimal allocated size of the internal buffer.
Throws:
Nothing.
Exception Safety:
No-throw.
Iterator Invalidation:
Does not invalidate any iterators.
Complexity:
Constant (in the size of the circular_buffer_space_optimized).
See Also:
reserve(), size(), max_size(), set_capacity(const capacity_type&)
void set_capacity(const capacity_type& capacity_ctrl);

Change the capacity (and the minimal guaranteed amount of allocated memory) of the circular_buffer_space_optimized.
Effect:
capacity() == capacity_ctrl && size() <= capacity_ctrl.capacity()

If the current number of elements stored in the circular_buffer_space_optimized is greater than the desired new capacity then number of [size() - capacity_ctrl.capacity()] last elements will be removed and the new size will be equal to capacity_ctrl.capacity().

If the current number of elements stored in the circular_buffer_space_optimized is lower than the new capacity then the amount of allocated memory in the internal buffer may be accommodated as necessary but it will never drop below capacity_ctrl.min_capacity().
Parameter(s):
capacity_ctrl
The new capacity controller.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Strong.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in min[size(), capacity_ctrl.capacity()]).
Note:
To explicitly clear the extra allocated memory use the shrink-to-fit technique:

boost::circular_buffer_space_optimized<int> cb(1000);
...
boost::circular_buffer_space_optimized<int>(cb).swap(cb);

For more information about the shrink-to-fit technique in STL see http://www.gotw.ca/gotw/054.htm.
See Also:
rset_capacity(const capacity_type&), resize(size_type, const_reference)
void resize(size_type new_size, const_reference item = value_type());

Change the size of the circular_buffer_space_optimized.
Effect:
size() == new_size && capacity().capacity() >= new_size

If the new size is greater than the current size, copies of item will be inserted at the back of the of the circular_buffer_space_optimized in order to achieve the desired size. In the case the resulting size exceeds the current capacity the capacity will be set to new_size.

If the current number of elements stored in the circular_buffer_space_optimized is greater than the desired new size then number of [size() - new_size] last elements will be removed. (The capacity will remain unchanged.)

The amount of allocated memory in the internal buffer may be accommodated as necessary.
Parameter(s):
new_size
The new size.
item
The element the circular_buffer_space_optimized will be filled with in order to gain the requested size. (See the Effect.)
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the new size of the circular_buffer_space_optimized).
See Also:
rresize(size_type, const_reference), set_capacity(const capacity_type&)
void rset_capacity(const capacity_type& capacity_ctrl);

Change the capacity (and the minimal guaranteed amount of allocated memory) of the circular_buffer_space_optimized.
Effect:
capacity() == capacity_ctrl && size() <= capacity_ctrl

If the current number of elements stored in the circular_buffer_space_optimized is greater than the desired new capacity then number of [size() - capacity_ctrl.capacity()] first elements will be removed and the new size will be equal to capacity_ctrl.capacity().

If the current number of elements stored in the circular_buffer_space_optimized is lower than the new capacity then the amount of allocated memory in the internal buffer may be accommodated as necessary but it will never drop below capacity_ctrl.min_capacity().
Parameter(s):
capacity_ctrl
The new capacity controller.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Strong.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in min[size(), capacity_ctrl.capacity()]).
See Also:
set_capacity(const capacity_type&), rresize(size_type, const_reference)
void rresize(size_type new_size, const_reference item = value_type());

Change the size of the circular_buffer_space_optimized.
Effect:
size() == new_size && capacity().capacity() >= new_size

If the new size is greater than the current size, copies of item will be inserted at the front of the of the circular_buffer_space_optimized in order to achieve the desired size. In the case the resulting size exceeds the current capacity the capacity will be set to new_size.

If the current number of elements stored in the circular_buffer_space_optimized is greater than the desired new size then number of [size() - new_size] first elements will be removed. (The capacity will remain unchanged.)

The amount of allocated memory in the internal buffer may be accommodated as necessary.
Parameter(s):
new_size
The new size.
item
The element the circular_buffer_space_optimized will be filled with in order to gain the requested size. (See the Effect.)
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the new size of the circular_buffer_space_optimized).
See Also:
resize(size_type, const_reference), rset_capacity(const capacity_type&)
circular_buffer_space_optimized<T,Alloc>& operator=(const circular_buffer_space_optimized<T,Alloc>& cb);

The assign operator.

Makes this circular_buffer_space_optimized to become a copy of the specified circular_buffer_space_optimized.

Effect:
*this == cb

The amount of allocated memory in the internal buffer is cb.size().
Parameter(s):
cb
The circular_buffer_space_optimized to be copied.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Strong.
Iterator Invalidation:
Invalidates all iterators pointing to this circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of cb).
See Also:
assign(size_type, const_reference), assign(capacity_type, size_type, const_reference), assign(InputIterator, InputIterator), assign(capacity_type, InputIterator, InputIterator)
void assign(size_type n, const_reference item);

Assign n items into the space optimized circular buffer.

The content of the circular_buffer_space_optimized will be removed and replaced with n copies of the item.

Effect:
capacity().capacity() == n && capacity().min_capacity() == 0 && size() == n && (*this)[0] == item && (*this)[1] == item && ... && (*this) [n - 1] == item

The amount of allocated memory in the internal buffer is n.
Parameter(s):
n
The number of elements the circular_buffer_space_optimized will be filled with.
item
The element the circular_buffer_space_optimized will be filled with.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the n).
See Also:
operator=, assign(capacity_type, size_type, const_reference), assign(InputIterator, InputIterator), assign(capacity_type, InputIterator, InputIterator)
void assign(capacity_type capacity_ctrl, size_type n, const_reference item);

Assign n items into the space optimized circular buffer specifying the capacity.

The capacity of the circular_buffer_space_optimized will be set to the specified value and the content of the circular_buffer_space_optimized will be removed and replaced with n copies of the item.

Precondition:
capacity_ctrl.capacity() >= n
Effect:
capacity() == capacity_ctrl && size() == n && (*this)[0] == item && (*this)[1] == item && ... && (*this) [n - 1] == item

The amount of allocated memory will be max[n, capacity_ctrl.min_capacity()].
Parameter(s):
capacity_ctrl
The new capacity controller.
n
The number of elements the circular_buffer_space_optimized will be filled with.
item
The element the circular_buffer_space_optimized will be filled with.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the n).
See Also:
operator=, assign(size_type, const_reference), assign(InputIterator, InputIterator), assign(capacity_type, InputIterator, InputIterator)
template <class InputIterator>
void assign(InputIterator first, InputIterator last);

Assign a copy of the range into the space optimized circular buffer.

The content of the circular_buffer_space_optimized will be removed and replaced with copies of elements from the specified range.

Precondition:
Valid range [first, last).
first and last have to meet the requirements of InputIterator.
Effect:
capacity().capacity() == std::distance(first, last) && capacity().min_capacity() == 0 && size() == std::distance(first, last) && (*this)[0]== *first && (*this)[1] == *(first + 1) && ... && (*this)[std::distance(first, last) - 1] == *(last - 1)

The amount of allocated memory in the internal buffer is std::distance(first, last).
Parameter(s):
first
The beginning of the range to be copied.
last
The end of the range to be copied.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the std::distance(first, last)).
See Also:
operator=, assign(size_type, const_reference), assign(capacity_type, size_type, const_reference), assign(capacity_type, InputIterator, InputIterator)
template <class InputIterator>
void assign(capacity_type capacity_ctrl, InputIterator first, InputIterator last);

Assign a copy of the range into the space optimized circular buffer specifying the capacity.

The capacity of the circular_buffer_space_optimized will be set to the specified value and the content of the circular_buffer_space_optimized will be removed and replaced with copies of elements from the specified range.

Precondition:
Valid range [first, last).
first and last have to meet the requirements of InputIterator.
Effect:
capacity() == capacity_ctrl && size() <= std::distance(first, last) && (*this)[0]== *(last - capacity) && (*this)[1] == *(last - capacity + 1) && ... && (*this)[capacity - 1] == *(last - 1)

If the number of items to be copied from the range [first, last) is greater than the specified capacity then only elements from the range [last - capacity, last) will be copied.

The amount of allocated memory in the internal buffer is max[std::distance(first, last), capacity_ctrl.min_capacity()].
Parameter(s):
capacity_ctrl
The new capacity controller.
first
The beginning of the range to be copied.
last
The end of the range to be copied.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in std::distance(first, last); in min[capacity_ctrl.capacity(), std::distance(first, last)] if the InputIterator is a RandomAccessIterator).
See Also:
operator=, assign(size_type, const_reference), assign(capacity_type, size_type, const_reference), assign(InputIterator, InputIterator)
void swap(circular_buffer_space_optimized<T,Alloc>& cb);

Swap the contents of two space optimized circular buffers.
Effect:
this contains elements of cb and vice versa; the capacity and the amount of allocated memory in the internal buffer of this equal to the capacity and the amount of allocated memory of cb and vice versa.
Parameter(s):
cb
The circular_buffer_space_optimized whose content will be swapped.
Throws:
Nothing.
Exception Safety:
No-throw.
Iterator Invalidation:
Invalidates all iterators of both circular_buffer_space_optimized containers. (On the other hand the iterators still point to the same elements but within another container. If you want to rely on this feature you have to turn the Debug Support off otherwise an assertion will report an error if such invalidated iterator is used.)
Complexity:
Constant (in the size of the circular_buffer_space_optimized).
See Also:
swap(circular_buffer_space_optimized<T, Alloc>&, circular_buffer_space_optimized<T, Alloc>&)
void push_back(const_reference item = value_type());

Insert a new element at the end of the space optimized circular buffer.
Effect:
if capacity().capacity() > 0 then back() == item
If the circular_buffer_space_optimized is full, the first element will be removed. If the capacity is 0, nothing will be inserted.

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
item
The element to be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
push_front(const_reference), pop_back(), pop_front()
void push_front(const_reference item = value_type());

Insert a new element at the beginning of the space optimized circular buffer.
Effect:
if capacity().capacity() > 0 then front() == item
If the circular_buffer_space_optimized is full, the last element will be removed. If the capacity is 0, nothing will be inserted.

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
item
The element to be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
push_back(const_reference), pop_back(), pop_front()
void pop_back();

Remove the last element from the space optimized circular buffer.
Precondition:
!empty()
Effect:
The last element is removed from the circular_buffer_space_optimized.

The amount of allocated memory in the internal buffer may be predictively decreased.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
pop_front(), push_back(const_reference), push_front(const_reference)
void pop_front();

Remove the first element from the space optimized circular buffer.
Precondition:
!empty()
Effect:
The first element is removed from the circular_buffer_space_optimized.

The amount of allocated memory in the internal buffer may be predictively decreased.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
pop_back(), push_back(const_reference), push_front(const_reference)
iterator insert(iterator pos, const_reference item = value_type());

Insert an element at the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Effect:
The item will be inserted at the position pos.
If the circular_buffer_space_optimized is full, the first element will be overwritten. If the circular_buffer_space_optimized is full and the pos points to begin(), then the item will not be inserted. If the capacity is 0, nothing will be inserted.

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position where the item will be inserted.
item
The element to be inserted.
Returns:
Iterator to the inserted element or begin() if the item is not inserted. (See the Effect.)
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
insert(iterator, size_type, value_type), insert(iterator, InputIterator, InputIterator), rinsert(iterator, value_type), rinsert(iterator, size_type, value_type), rinsert(iterator, InputIterator, InputIterator)
void insert(iterator pos, size_type n, const_reference item);

Insert n copies of the item at the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Effect:
The number of min[n, (pos - begin()) + reserve()] elements will be inserted at the position pos.
The number of min[pos - begin(), max[0, n - reserve()]] elements will be overwritten at the beginning of the circular_buffer_space_optimized.
(See Example for the explanation.)

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position where the items will be inserted.
n
The number of items the to be inserted.
item
The element whose copies will be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in min[capacity().capacity(), size() + n]).
Example:
Consider a circular_buffer_space_optimized with the capacity of 6 and the size of 4. Its internal buffer may look like the one below.

|1|2|3|4| | |
p ---^

After inserting 5 elements at the position p:

insert(p, (size_t)5, 0);

actually only 4 elements get inserted and elements 1 and 2 are overwritten. This is due to the fact the insert operation preserves the capacity. After insertion the internal buffer looks like this:

|0|0|0|0|3|4|

For comparison if the capacity would not be preserved the internal buffer would then result in |1|2|0|0|0|0|0|3|4|.
See Also:
insert(iterator, value_type), insert(iterator, InputIterator, InputIterator), rinsert(iterator, value_type), rinsert(iterator, size_type, value_type), rinsert(iterator, InputIterator, InputIterator)
template <class InputIterator>
void insert(iterator pos, InputIterator first, InputIterator last);

Insert the range [first, last) at the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Valid range [first, last) where first and last meet the requirements of an InputIterator.
Effect:
Elements from the range [first + max[0, distance(first, last) - (pos - begin()) - reserve()], last) will be inserted at the position pos.
The number of min[pos - begin(), max[0, distance(first, last) - reserve()]] elements will be overwritten at the beginning of the circular_buffer_space_optimized.
(See Example for the explanation.)

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position where the range will be inserted.
first
The beginning of the range to be inserted.
last
The end of the range to be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in [size() + std::distance(first, last)]; in min[capacity().capacity(), size() + std::distance(first, last)] if the InputIterator is a RandomAccessIterator).
Example:
Consider a circular_buffer_space_optimized with the capacity of 6 and the size of 4. Its internal buffer may look like the one below.

|1|2|3|4| | |
p ---^

After inserting a range of elements at the position p:

int array[] = { 5, 6, 7, 8, 9 };
insert(p, array, array + 5);

actually only elements 6, 7, 8 and 9 from the specified range get inserted and elements 1 and 2 are overwritten. This is due to the fact the insert operation preserves the capacity. After insertion the internal buffer looks like this:

|6|7|8|9|3|4|

For comparison if the capacity would not be preserved the internal buffer would then result in |1|2|5|6|7|8|9|3|4|.
See Also:
insert(iterator, value_type), insert(iterator, size_type, value_type), rinsert(iterator, value_type), rinsert(iterator, size_type, value_type), rinsert(iterator, InputIterator, InputIterator)
iterator rinsert(iterator pos, const_reference item = value_type());

Insert an element before the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Effect:
The item will be inserted before the position pos.
If the circular_buffer_space_optimized is full, the last element will be overwritten. If the circular_buffer_space_optimized is full and the pos points to end(), then the item will not be inserted. If the capacity is 0, nothing will be inserted.

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position before which the item will be inserted.
item
The element to be inserted.
Returns:
Iterator to the inserted element or end() if the item is not inserted. (See the Effect.)
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
rinsert(iterator, size_type, value_type), rinsert(iterator, InputIterator, InputIterator), insert(iterator, value_type), insert(iterator, size_type, value_type), insert(iterator, InputIterator, InputIterator)
void rinsert(iterator pos, size_type n, const_reference item);

Insert n copies of the item before the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Effect:
The number of min[n, (end() - pos) + reserve()] elements will be inserted before the position pos.
The number of min[end() - pos, max[0, n - reserve()]] elements will be overwritten at the end of the circular_buffer_space_optimized.
(See Example for the explanation.)

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position where the items will be inserted.
n
The number of items the to be inserted.
item
The element whose copies will be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in min[capacity().capacity(), size() + n]).
Example:
Consider a circular_buffer_space_optimized with the capacity of 6 and the size of 4. Its internal buffer may look like the one below.

|1|2|3|4| | |
p ---^

After inserting 5 elements before the position p:

rinsert(p, (size_t)5, 0);

actually only 4 elements get inserted and elements 3 and 4 are overwritten. This is due to the fact the rinsert operation preserves the capacity. After insertion the internal buffer looks like this:

|1|2|0|0|0|0|

For comparison if the capacity would not be preserved the internal buffer would then result in |1|2|0|0|0|0|0|3|4|.
See Also:
rinsert(iterator, value_type), rinsert(iterator, InputIterator, InputIterator), insert(iterator, value_type), insert(iterator, size_type, value_type), insert(iterator, InputIterator, InputIterator)
template <class InputIterator>
void rinsert(iterator pos, InputIterator first, InputIterator last);

Insert the range [first, last) before the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized or its end.
Valid range [first, last) where first and last meet the requirements of an InputIterator.
Effect:
Elements from the range [first, last - max[0, distance(first, last) - (end() - pos) - reserve()]) will be inserted before the position pos.
The number of min[end() - pos, max[0, distance(first, last) - reserve()]] elements will be overwritten at the end of the circular_buffer.
(See Example for the explanation.)

The amount of allocated memory in the internal buffer may be predictively increased.
Parameter(s):
pos
An iterator specifying the position where the range will be inserted.
first
The beginning of the range to be inserted.
last
The end of the range to be inserted.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::T(const T&) throws.
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in [size() + std::distance(first, last)]; in min[capacity().capacity(), size() + std::distance(first, last)] if the InputIterator is a RandomAccessIterator).
Example:
Consider a circular_buffer_space_optimized with the capacity of 6 and the size of 4. Its internal buffer may look like the one below.

|1|2|3|4| | |
p ---^

After inserting a range of elements before the position p:

int array[] = { 5, 6, 7, 8, 9 };
insert(p, array, array + 5);

actually only elements 5, 6, 7 and 8 from the specified range get inserted and elements 3 and 4 are overwritten. This is due to the fact the rinsert operation preserves the capacity. After insertion the internal buffer looks like this:

|1|2|5|6|7|8|

For comparison if the capacity would not be preserved the internal buffer would then result in |1|2|5|6|7|8|9|3|4|.
See Also:
rinsert(iterator, value_type), rinsert(iterator, size_type, value_type), insert(iterator, value_type), insert(iterator, size_type, value_type), insert(iterator, InputIterator, InputIterator)
iterator erase(iterator pos);

Remove an element at the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized (but not an end()).
Effect:
The element at the position pos is removed.

The amount of allocated memory in the internal buffer may be predictively decreased.
Parameter(s):
pos
An iterator pointing at the element to be removed.
Returns:
Iterator to the first element remaining beyond the removed element or end() if no such element exists.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
erase(iterator, iterator), rerase(iterator), rerase(iterator, iterator), clear()
iterator erase(iterator first, iterator last);

Erase the range [first, last).
Precondition:
Valid range [first, last).
Effect:
The elements from the range [first, last) are removed. (If first == last nothing is removed.)

The amount of allocated memory in the internal buffer may be predictively decreased.
Parameter(s):
first
The beginning of the range to be removed.
last
The end of the range to be removed.
Returns:
Iterator to the first element remaining beyond the removed elements or end() if no such element exists.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
erase(iterator), rerase(iterator), rerase(iterator, iterator), clear()
iterator rerase(iterator pos);

Remove an element at the specified position.
Precondition:
pos is a valid iterator pointing to the circular_buffer_space_optimized (but not an end()).

The amount of allocated memory in the internal buffer may be predictively decreased.
Effect:
The element at the position pos is removed.
Parameter(s):
pos
An iterator pointing at the element to be removed.
Returns:
Iterator to the first element remaining in front of the removed element or begin() if no such element exists.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
Note:
Basically there is no difference between erase(iterator) and this method. It is implemented only for consistency with the base circular_buffer.
See Also:
erase(iterator), erase(iterator, iterator), rerase(iterator, iterator), clear()
iterator rerase(iterator first, iterator last);

Erase the range [first, last).
Precondition:
Valid range [first, last).
Effect:
The elements from the range [first, last) are removed. (If first == last nothing is removed.)

The amount of allocated memory in the internal buffer may be predictively decreased.
Parameter(s):
first
The beginning of the range to be removed.
last
The end of the range to be removed.
Returns:
Iterator to the first element remaining in front of the removed elements or begin() if no such element exists.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Whatever T::operator = (const T&) throws.
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
Note:
Basically there is no difference between erase(iterator, iterator) and this method. It is implemented only for consistency with the base circular_buffer.
See Also:
erase(iterator), erase(iterator, iterator), rerase(iterator), clear()
void clear();

Remove all stored elements from the space optimized circular buffer.
Effect:
size() == 0

The amount of allocated memory in the internal buffer may be predictively decreased.
Throws:
An allocation error if memory is exhausted (std::bad_alloc if the standard allocator is used).
Exception Safety:
Basic.
Iterator Invalidation:
Invalidates all iterators pointing to the circular_buffer_space_optimized (except iterators equal to end()).
Complexity:
Linear (in the size of the circular_buffer_space_optimized).
See Also:
~circular_buffer_space_optimized(), erase(iterator), erase(iterator, iterator), rerase(iterator), rerase(iterator, iterator)

See also

boost::circular_buffer, std::vector

Acknowledgements

The idea of the space optimized circular buffer has been introduced by Pavel Vozenilek.

Release Notes

Boost 1.37

Boost 1.36

Boost 1.35

Copyright © 2003-2008 Jan Gaspar

Use, modification, and distribution is subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)