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TMapBase

The base class of maps from keys to values.

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

Inheritance Hierarchy

References

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

Syntax

template<typename KeyType, typename ValueType, typename SetAllocator, typename KeyFuncs>  
class TMapBase

Remarks

The base class of maps from keys to values. Implemented using a TSet of key-value pairs with a custom KeyFuncs, with the same O(1) addition, removal, and finding.

The ByHash() functions are somewhat dangerous but particularly useful in two scenarios: Heterogeneous lookup to avoid creating expensive keys like FString when looking up by const TCHAR*. You must ensure the hash is calculated in the same way as ElementType is hashed. If possible put both ComparableKey and ElementType hash functions next to each other in the same header to avoid bugs when the ElementType hash function is changed. Reducing contention around hash tables protected by a lock. It is often important to incur the cache misses of reading key data and doing the hashing before acquiring the lock.

Variables

  Type Name Description
Protected variable ElementSetType Pairs A set of the key-value pairs in the map.

Constructors

  Type Name Description
Protected function    
Protected function    
Protected function  

TMapBase ( const TMapBase&
)

  
Protected function  

TMapBase ( TMapBase< KeyType, ValueType, OtherSetAllocator, KeyFuncs >&& Other
)

 Constructor for moving elements from a TMap with a different SetAllocator
Protected function  

TMapBase ( const TMapBase< KeyType, ValueType, OtherSetAllocator, KeyFuncs >& Other
)

 Constructor for copying elements from a TMap with a different SetAllocator

Functions

  Type Name Description
Public function ValueType &

Add ( KeyType&& InKey,
ValueType&& InValue
)

  
Public function ValueType &

Add ( KeyType&& InKey,
const ValueType& InValue
)

  
Public function ValueType &

Add ( const KeyType& InKey,
ValueType&& InValue
)

  
Public function ValueType &

Add ( const KeyType& InKey,
const ValueType& InValue
)

 Set the value associated with a key.
Public function ValueType &

Add ( TTuple< KeyType, ValueType >&& InKeyValue
)

  
Public function ValueType &

Add ( const TTuple< KeyType, ValueType >& InKeyValue
)

 Set the value associated with a key.
Public function ValueType &

Add ( KeyType&& InKey
)

  
Public function ValueType &

Add ( const KeyType& InKey
)

 Set a default value associated with a key.
Public function ValueType &

AddByHash ( uint32 KeyHash,
const KeyType& InKey,
const ValueType& InValue
)

 See Add() and class documentation section on ByHash() functions
Public function ValueType &

AddByHash ( uint32 KeyHash,
KeyType&& InKey,
ValueType&& InValue
)

  
Public function ValueType &

AddByHash ( uint32 KeyHash,
KeyType&& InKey,
const ValueType& InValue
)

  
Public function ValueType &

AddByHash ( uint32 KeyHash,
const KeyType& InKey,
ValueType&& InValue
)

  
Public function ValueType &

AddByHash ( uint32 KeyHash,
KeyType&& InKey
)

  
Public function ValueType &

AddByHash ( uint32 KeyHash,
const KeyType& InKey
)

 See Add() and class documentation section on ByHash() functions
Public function Static void

AppendHash ( const FPlatformTypeLayoutParameters& LayoutParams,
FSHA1& Hasher
)

  
Public function Const TArray< ElementType >

Array ()

 Copy the key/value pairs in this map into an array.
Public function Const TRangedForConstIterator

begin ()

  
Public function TRangedForIterator

begin ()

 DO NOT USE DIRECTLY STL-like iterators to enable range-based for loop support.
Public function void

Compact ()

 Compacts the pair set to remove holes
Public function void Compacts the pair set to remove holes. Does not change the iteration order of the elements.
Public function Const bool Check if map contains the specified key.
Public function Const bool

ContainsByHash ( uint32 KeyHash,
const ComparableKey& Key
)

 See Contains() and class documentation section on ByHash() functions
Public function Const void

CopyUnfrozen ( const FMemoryUnfreezeContent& Context,
void* Dst
)

  
Public function Const void Track the container's memory use through an archive.
Public function Const TConstIterator Creates a const iterator over all the pairs in this map
Public function Const TConstKeyIterator Creates a const iterator over the values associated with a specified key in a map
Public function TIterator Creates an iterator over all the pairs in this map
Public function TKeyIterator Creates an iterator over the values associated with a specified key in a map
Public function void Describes the map's contents through an output device.
Public function ValueType &

Emplace ( InitKeyType&& InKey,
InitValueType&& InValue
)

 Sets the value associated with a key.
Public function ValueType &

Emplace ( InitKeyType&& InKey
)

 Set a default value associated with a key.
Public function ValueType &

EmplaceByHash ( uint32 KeyHash,
InitKeyType&& InKey
)

 See Emplace() and class documentation section on ByHash() functions
Public function ValueType &

EmplaceByHash ( uint32 KeyHash,
InitKeyType&& InKey,
InitValueType&& InValue
)

 See Emplace() and class documentation section on ByHash() functions
Public function void

Empty ( int32 ExpectedNumElements
)

 Removes all elements from the map.
Public function TRangedForIterator

end ()

  
Public function Const TRangedForConstIterator

end ()

  
Public function Const TMap< KeyType, ValueType, SetAllocator, KeyFuncs >

FilterByPredicate ( Predicate Pred
)

 Filters the elements in the map based on a predicate functor.
Public function ValueType * Find the value associated with a specified key.
Public function Const const ValueType *  
Public function Const const ValueType *

FindByHash ( uint32 KeyHash,
const ComparableKey& Key
)

  
Public function ValueType *

FindByHash ( uint32 KeyHash,
const ComparableKey& Key
)

 See Find() and class documentation section on ByHash() functions
Public function ValueType & Find a reference to the value associated with a specified key.
Public function Const const ValueType & Find a reference to the value associated with a specified key.
Public function Const const KeyType * Find the key associated with the specified value.The time taken is O(N) in the number of pairs.
Public function ValueType &

FindOrAdd ( KeyType&& Key,
const ValueType& Value
)

  
Public function ValueType &

FindOrAdd ( KeyType&& Key,
ValueType&& Value
)

  
Public function ValueType &

FindOrAdd ( const KeyType& Key,
ValueType&& Value
)

  
Public function ValueType &

FindOrAdd ( KeyType&& Key
)

  
Public function ValueType &

FindOrAdd ( const KeyType& Key
)

 Find the value associated with a specified key, or if none exists, adds a value using the default constructor.
Public function ValueType &

FindOrAdd ( const KeyType& Key,
const ValueType& Value
)

 Find the value associated with a specified key, or if none exists, adds a value using the default constructor.
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
const KeyType& Key,
ValueType&& Value
)

  
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
KeyType&& Key
)

  
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
const KeyType& Key
)

 See FindOrAdd() and class documentation section on ByHash() functions
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
KeyType&& Key,
const ValueType& Value
)

  
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
KeyType&& Key,
ValueType&& Value
)

  
Public function ValueType &

FindOrAddByHash ( uint32 KeyHash,
const KeyType& Key,
const ValueType& Value
)

 See FindOrAdd() and class documentation section on ByHash() functions
Public function Const ValueType Find the value associated with a specified key.
Public function Const void

GenerateKeyArray ( TArray< KeyType, Allocator >& OutArray
)

 Generate an array from the keys in this map.
Public function Const void

GenerateValueArray ( TArray< ValueType, Allocator >& OutArray
)

 Generate an array from the values in this map.
Public function ElementType & Return a mapped pair by internal identifier. Element must be valid (see ).
Public function Const const ElementType & Return a mapped pair by internal identifier. Element must be valid (see ).
Public function Const SIZE_T Helper function to return the amount of memory allocated by this container .
Public function Const int32

GetKeys ( TSet< KeyType, Allocator >& OutKeys
)

 Get the unique keys contained within this map.
Public function Const int32

GetKeys ( TArray< KeyType, Allocator >& OutKeys
)

 Get the unique keys contained within this map.
Public function Const int32  
Public function Const bool

IsEmpty ()

 Returns true if the map is empty and contains no elements.
Public function Const bool Checks whether an element id is valid.
Public function Const int32

Num ()

  
Public function Const bool Compare this map with another for equality.
Public function int32 Remove all value associations for a key.
Public function int32

RemoveByHash ( uint32 KeyHash,
const ComparableKey& Key
)

 See Remove() and class documentation section on ByHash() functions
Public function void

Reserve ( int32 Number
)

 Preallocates enough memory to contain Number elements
Public function void

Reset ()

 Efficiently empties out the map but preserves all allocations and capacities
Public function void

Shrink ()

 Shrinks the pair set to avoid slack.
Public function Const void  

Operators

  Type Name Description
Protected function TMapBase &

operator= ( TMapBase< KeyType, ValueType, OtherSetAllocator, KeyFuncs >&& Other
)

 Assignment operator for moving elements from a TMap with a different SetAllocator
Protected function TMapBase &

operator= ( const TMapBase&
)

  
Protected function TMapBase &  
Protected function TMapBase &

operator= ( const TMapBase< KeyType, ValueType, OtherSetAllocator, KeyFuncs >& Other
)

 Assignment operator for copying elements from a TMap with a different SetAllocator

Classes

  Type Name Description
Protected class TBaseIterator The base of TMapBase iterators.  
Protected class TBaseKeyIterator The base type of iterators that iterate over the values associated with a specified key.  
Public class TConstIterator Const map iterator.  
Public class TConstKeyIterator Iterates over values associated with a specified key in a const map.  
Public class TIterator Map iterator.  
Public class TKeyIterator Iterates over values associated with a specified key in a map.  

Typedefs

Name Description
ElementSetType  
ElementType  
KeyConstPointerType  
KeyInitType  
TRangedForConstIterator  
TRangedForIterator  
ValueInitType  

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