TDiscardableKeyValueCache | Unreal Engine 5.2 Documentation

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

References


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

Syntax

template<class KeyType, class ValueType>  
class TDiscardableKeyValueCache

Remarks

Implements a thread-safe discardable Key/Value cache by using two maps - a primary and a backfill.

Find() checks the current map first then the backfill. Entries found in the backfill are moved into the primary map.

When Swap is called all items in the backfill are removed and the currentmap & backfill are swapped.

This results in most recently used items being retained and older/unused items being evicted. The more often Swap is called the shorter the lifespan for items

Variables

	Type	Name	Description
	TypedMap *	BackfillMap
	TypedMap *	CurrentMap
	FRWLock	LockObject
	TypedMap	Map1
	TypedMap	Map2

Constructors

	Type	Name	Description
		TDiscardableKeyValueCache ()

Functions

Type	Name	Description
bool	Add ( const KeyType& Key, const ValueType& Value )	Add an entry to the current map.
bool	Add ( const KeyType& Key, const ValueType& Value, const uint32 LockFlags )	Add an entry to the current map.
uint32	ApplyLock ( uint32 CurrentFlags, uint32 NewFlags )
TypedMap &	Backfill ()	Reference to the current map
TypedMap &	Current ()	Reference to the current map
int32	Discard ()	Discard all items left in the backfill and swap the current & backfill pointers
int32	Discard ( DeleteFunc Func )
int32	Discard ( uint32 InCurrentLockFlags, uint32& OutNewLockFlags, DeleteFunc Func )	Discard all items in the backfill and swap the current & backfill pointers
bool	Find ( const KeyType& Key, ValueType& OutType )	Returns true and sets OutType to the value with the associated key if it exists.
bool	Find ( const KeyType& Key, ValueType& OutType, uint32 InCurrentLockFlags, uint32& OutLockFlags )	Externally-lock-aware Find function.
bool	InternalFindWhileLocked ( const KeyType& Key, ValueType& OutType, uint32 InCurrentLockFlags, uint32& OutFlags )	Checks for the entry in our current map, and if not found the backfill.
int32	Num ()	Returns the total number of items in the cache
FRWLock &	RWLock ()	Access to the internal locking object
void	Unlock ( uint32 Flags )

Classes

	Type	Name	Description
	LockFlags	Flags used when calling Find()

Typedefs

Name	Description
TypedMap

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