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  3. TRingBuffer

TRingBuffer

RingBuffer - an array with a Front and Back pointer and with implicit wraparound to the beginning of the array when reaching the end of the array when iterating from Front to Back Useful for providing O(1) push/pop at the end of the array (for Queue or Stack) while still having high cache coherency during iteration.

API > API/Runtime > API/Runtime/Core > API/Runtime/Core/Containers

References

   
Module Core
Header /Engine/Source/Runtime/Core/Public/Containers/RingBuffer.h
Include #include "Containers/RingBuffer.h"

Syntax

template<typename T, typename AllocatorT>  
class TRingBuffer

Remarks

RingBuffer - an array with a Front and Back pointer and with implicit wraparound to the beginning of the array when reaching the end of the array when iterating from Front to Back Useful for providing O(1) push/pop at the end of the array (for Queue or Stack) while still having high cache coherency during iteration. Not threadsafe; caller must ensure there is no simultaneous access from multiple threads.

Implementation Details: Relies on unsigned arithmetics and ever increasing Front and Back indices to avoid having to store an extra element or maintain explicit empty state. Capacity will always be rounded up to the next power of two, to provide rapid masking of the index.

Constructors

  Type Name Description
Public function   Construct Empty Queue with capacity 0.
Public function  

TRingBuffer ( SizeType InitialCapacity
)

 Construct Empty Queue with the given initial requested capacity.
Public function  

TRingBuffer ( std::initializer_list< ElementType > InitList
)

 Construct a Queue with initial state (from front to back) equal to the given list.
Public function  

TRingBuffer ( TRingBuffer&& Other
)

  
Public function  

TRingBuffer ( const TRingBuffer& Other
)

  

Destructors

  Type Name Description
Public function    

Functions

  Type Name Description
Public function IndexType

Add ( const ElementType& Element
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function IndexType

Add ( ElementType&& Element
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function ElementType &

Add_GetRef ( const ElementType& Element
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function ElementType &

Add_GetRef ( ElementType&& Element
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function IndexType

AddFront ( const ElementType& Element
)

 Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function IndexType

AddFront ( ElementType&& Element
)

 Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function ElementType & Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function ElementType &

AddFront_GetRef ( const ElementType& Element
)

 Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function IndexType Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function ElementType & Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function IndexType Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function ElementType & Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function Const TConstIterator

begin ()

 Begin iterator for const ranged-for
Public function TIterator

begin ()

 Begin iterator for ranged-for
Public function TArrayView< T >

Compact ()

 Shift all elements so that the front pointer's location in memory is less than the back pointer's.
Public function Const IndexType Given a pointer to an Element anywhere in memory, return the index of the element in the RingBuffer, or INDEX_NONE if it is not present.
Public function IndexType

Emplace ( ArgsType&&... Args
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function ElementType &

Emplace_GetRef ( ArgsType&&... Args
)

 Add a new element after the back pointer of the RingBuffer, resizing if necessary.
Public function IndexType

EmplaceFront ( ArgsType&&... Args
)

 Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function ElementType &

EmplaceFront_GetRef ( ArgsType&&... Args
)

 Add a new element before the front pointer of the RingBuffer, resizing if necessary.
Public function void

Empty ( SizeType Capacity
)

 Empty the RingBuffer, destructing any elements and releasing the RingBuffer's storage.
Public function Const TConstIterator

end ()

 End iterator for const ranged-for
Public function TIterator

end ()

 End iterator for ranged-for
Public function Const const ElementType &

First ()

 Return a const reference to the element at the front pointer of the RingBuffer.
Public function ElementType &

First ()

 Return a reference to the element at the front pointer of the RingBuffer.
Public function Const SIZE_T Helper function to return the amount of memory allocated by this container.
Public function ElementType & Unsafely return a writable reference to the value at the given Index.
Public function Const const ElementType & Unsafely return a const reference to the value at the given Index.
Public function Const bool

IsEmpty ()

 Returns true if the RingBuffer is empty.
Public function Const bool Tests if index is valid, i.e. greater than or equal to zero, and less than the number of elements in the array.
Public function Const const ElementType &

Last ()

 Return a const reference to the element at the back pointer of the RingBuffer.
Public function ElementType &

Last ()

 Return a reference to the element at the back pointer of the RingBuffer.
Public function Const IndexType

Max ()

 Current allocated Capacity, note this will always be a power of two, or the special case 0.
Public function void

MoveAppendRange ( ElementType* OtherData,
SizeType OtherNum
)

 Append elements from a range onto the back pointer of the RingBuffer, resizing if necessary.
Public function Const IndexType

Num ()

 Gets the number of elements in the RingBuffer.
Public function void

Pop ( SizeType PopCount
)

 Pop the given number of arguments (default: 1) from the back pointer of the RingBuffer.
Public function void

PopFront ( SizeType PopCount
)

 Pop the given number of elements (default: 1) from the front pointer of the RingBuffer.
Public function void

PopFrontNoCheck ( SizeType PopCount
)

 Unsafely pop the given number of arguments (default: 1) from the front pointer of the RingBuffer.
Public function ElementType Pop one element from the front pointer of the RingBuffer and return the popped value.
Public function void

PopNoCheck ( SizeType PopCount
)

 Pop the given number of elements (default: 1) from the back pointer of the RingBuffer.
Public function ElementType Pop one element from the back pointer of the RingBuffer and return the popped value.
Public function SizeType

Remove ( const ElementType& Item
)

 Removes as many instances of Item as there are in the array, maintaining order but not indices.
Public function SizeType

RemoveAll ( PredicateType Predicate
)

 Removes as many instances of Item as there are in the array, maintaining order but not indices.
Public function void

RemoveAt ( IndexType Index
)

 Remove the value at the given index from the RingBuffer, and shift values ahead or behind it into its location to fill the hole.
Public function void

Reserve ( SizeType RequiredCapacity
)

 Set the capacity to the maximum of the current capacity and the (next power of two greater than or equal to) the given capacity.
Public function void

Reset ()

 Empty the RingBuffer, destructing any elements in the RingBuffer but not releasing the RingBuffer's storage.
Public function void Move the value at the given index into the back pointer of the RingBuffer, and shift all elements behind of it up by one to make room for it.
Public function void Move the value at the given index into the front pointer of the RingBuffer, and shift all elements ahead of it down by one to make room for it.
Public function void

Trim ()

 Set the capacity to the minimum power of two (or 0) greater than or equal to the current number of elements in the RingBuffer.

Operators

  Type Name Description
Public function Const bool

operator!= ( const TRingBuffer< ElementType, OtherAllocator >& Other
)

  
Public function Const const ElementType &

operator[] ( IndexType Index
)

 Return a const reference to the value at the given Index.
Public function ElementType &

operator[] ( IndexType Index
)

 Return a writable reference to the value at the given Index.
Public function TRingBuffer &

operator= ( const TRingBuffer& Other
)

  
Public function TRingBuffer &

operator= ( TRingBuffer&& Other
)

  
Public function Const bool

operator== ( const TRingBuffer< ElementType, OtherAllocator >& Other
)

  

Typedefs

Name Description
Allocator The Allocator type being used
ElementType Type of the Elements in the container.
IndexType Type used to request values at a given index in the container.
SizeType Type used to communicate size and capacity and counts
StorageModuloType Type used for variables that are indexes into the underlying storage.
TConstIterator  
TIterator Iterator type used for ranged-for traversal.

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