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TMapBase

The base class of maps from keys to values.

API > API/Runtime > API/Runtime/Core

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.

   
Name TMapBase
Type class
Header File /Engine/Source/Runtime/Core/Public/Containers/Map.h
Include Path #include "Containers/Map.h"

Syntax

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

Derived Classes

Constructors

Name Remarks Include Path Unreal Specifiers

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

 Constructor for moving elements from a TMap with a different SetAllocator Containers/Map.h  

TMapBase ( const TMapBase&
)

   Containers/Map.h  
  Containers/Map.h  
  Containers/Map.h  

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

 Constructor for copying elements from a TMap with a different SetAllocator Containers/Map.h  
  Containers/Map.h  

Classes

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

Typedefs

Name Type Remarks Include Path
ElementSetType TSet< ElementType, KeyFuncs, SetAllocator >   Containers/Map.h
ElementType TPair< KeyType, ValueType >   Containers/Map.h
IntrusiveUnsetOptionalStateType TMapBase   Containers/Map.h
KeyConstPointerType TTypeTraits< KeyType >::ConstPointerType   Containers/Map.h
KeyInitType TTypeTraits< KeyType >::ConstInitType   Containers/Map.h
TRangedForConstIterator TBaseIterator< true, true >   Containers/Map.h
TRangedForIterator TBaseIterator< false, true >   Containers/Map.h
ValueInitType TTypeTraits< ValueType >::ConstInitType   Containers/Map.h

Constants

Name Type Remarks Include Path
bHasIntrusiveUnsetOptionalState bool Start - intrusive TOptional state //. Containers/Map.h

Functions

Public

Name Remarks Include Path Unreal Specifiers

ValueType & Add ( const KeyType& InKey
)

 Set a default value associated with a key. Containers/Map.h  

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

 Set the value associated with a key. Containers/Map.h  

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

   Containers/Map.h  

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

 Set the value associated with a key. Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

ValueType & Add ( KeyType&& InKey
)

   Containers/Map.h  

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

 See Add() and class documentation section on ByHash() functions Containers/Map.h  

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

 See Add() and class documentation section on ByHash() functions Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

TArray< ElementType > Array()

 Copy the key/value pairs in this map into an array. Containers/Map.h  

TRangedForIterator begin ()

 DO NOT USE DIRECTLY STL-like iterators to enable range-based for loop support. Containers/Map.h  

TRangedForConstIterator begin ()

   Containers/Map.h  

void Compact()

 Compacts the pair set to remove holes Containers/Map.h  

void CompactStable()

 Compacts the pair set to remove holes. Does not change the iteration order of the elements. Containers/Map.h  

bool Contains ( KeyConstPointerType Key
) const

 Check if map contains the specified key. Containers/Map.h  

bool ContainsByHash ( uint32 KeyHash,
const ComparableKey& Key
) const

 See Contains() and class documentation section on ByHash() functions Containers/Map.h  

void CopyUnfrozen ( const FMemoryUnfreezeContent& Context,
void* Dst
) const

   Containers/Map.h  

void CountBytes ( FArchive& Ar
) const

 Track the container's memory use through an archive. Containers/Map.h  

TConstIterator CreateConstIterator()

 Creates a const iterator over all the pairs in this map Containers/Map.h  

TConstKeyIterator CreateConstKeyIterator ( typename TConstKeyIterator::KeyArgumentType InKey
) const

 Creates a const iterator over the values associated with a specified key in a map Containers/Map.h  

TIterator CreateIterator()

 Creates an iterator over all the pairs in this map Containers/Map.h  

TKeyIterator CreateKeyIterator ( typename TKeyIterator::KeyArgumentType InKey
)

 Creates an iterator over the values associated with a specified key in a map Containers/Map.h  

void Dump ( FOutputDevice& Ar
)

 Describes the map's contents through an output device. Containers/Map.h  

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

 Sets the value associated with a key. Containers/Map.h  

ValueType & Emplace ( InitKeyType&& InKey
)

 Set a default value associated with a key. Containers/Map.h  

ValueType & EmplaceByHash ( uint32 KeyHash,
InitKeyType&& InKey
)

 See Emplace() and class documentation section on ByHash() functions Containers/Map.h  

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

 See Emplace() and class documentation section on ByHash() functions Containers/Map.h  

void Empty ( int32 ExpectedNumElements
)

 Removes all elements from the map. Containers/Map.h  

TRangedForIterator end ()

   Containers/Map.h  

TRangedForConstIterator end ()

   Containers/Map.h  

TMap< KeyType, ValueType, SetAllocator, KeyFuncs > FilterByPredicate ( Predicate Pred
) const

 Filters the elements in the map based on a predicate functor. Containers/Map.h  

ValueType * Find ( KeyConstPointerType Key
)

 Find the value associated with a specified key. Containers/Map.h  

const ValueType * Find ( KeyConstPointerType Key
) const

   Containers/Map.h  

const ElementType * FindArbitraryElement ()

   Containers/Map.h  

ElementType * FindArbitraryElement ()

 Finds any pair in the map and returns a pointer to it. Containers/Map.h  

const ValueType * FindByHash ( uint32 KeyHash,
const ComparableKey& Key
) const

   Containers/Map.h  

ValueType * FindByHash ( uint32 KeyHash,
const ComparableKey& Key
)

 See Find() and class documentation section on ByHash() functions Containers/Map.h  

const ValueType & FindByHashChecked ( uint32 KeyHash,
const ComparableKey& Key
) const

   Containers/Map.h  

ValueType & FindByHashChecked ( uint32 KeyHash,
const ComparableKey& Key
)

   Containers/Map.h  

ValueType & FindChecked ( KeyConstPointerType Key
)

 Find a reference to the value associated with a specified key. Containers/Map.h  

const ValueType & FindChecked ( KeyConstPointerType Key
) const

 Find a reference to the value associated with a specified key. Containers/Map.h  

FSetElementId FindId ( KeyInitType Key
) const

 Finds the index of the first element that is assigned to the specified key. Containers/Map.h  

FSetElementId FindIdByHash ( uint32 KeyHash,
const ComparableKey& Key
) const

 See FindId() and class documentation section on ByHash() functions Containers/Map.h  

const KeyType * FindKey ( ValueInitType Value
) const

 Find the key associated with the specified value.The time taken is O(N) in the number of pairs. Containers/Map.h  

ValueType & FindOrAdd ( const KeyType& Key
)

 Find the value associated with a specified key, or if none exists, adds a value using the default constructor. Containers/Map.h  

ValueType & FindOrAdd ( KeyType&& Key
)

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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. Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

   Containers/Map.h  

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

 See FindOrAdd() and class documentation section on ByHash() functions Containers/Map.h  

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

 See FindOrAdd() and class documentation section on ByHash() functions Containers/Map.h  

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

   Containers/Map.h  

ValueType FindRef ( KeyConstPointerType Key
) const

 Find the value associated with a specified key. Containers/Map.h  

ValueType FindRef ( KeyConstPointerType Key,
ValueType DefaultValue
) const

 Find the value associated with a specified key. Containers/Map.h  

void GenerateKeyArray ( TArray< KeyType, Allocator >& OutArray
) const

 Generate an array from the keys in this map. Containers/Map.h  

void GenerateValueArray ( TArray< ValueType, Allocator >& OutArray
) const

 Generate an array from the values in this map. Containers/Map.h  

const ElementType & Get ( FSetElementId Id
) const

 Return a mapped pair by internal identifier. Element must be valid (see @IsValidId). Containers/Map.h  

ElementType & Get ( FSetElementId Id
)

 Return a mapped pair by internal identifier. Element must be valid (see @IsValidId). Containers/Map.h  

SIZE_T GetAllocatedSize ()

 Helper function to return the amount of memory allocated by this container . Containers/Map.h  

int32 GetKeys ( TArray< KeyType, Allocator >& OutKeys
) const

 Get the unique keys contained within this map. Containers/Map.h  

int32 GetKeys ( TSet< KeyType, InSetKeyFuncs, InSetAllocator >& OutKeys
) const

 Get the unique keys contained within this map. Containers/Map.h  

int32 GetMaxIndex()

   Containers/Map.h  

bool IsEmpty ()

 Returns true if the map is empty and contains no elements. Containers/Map.h  

bool IsValidId ( FSetElementId Id
) const

 Checks whether an element id is valid. Containers/Map.h  

int32 Num()

   Containers/Map.h  

bool OrderIndependentCompareEqual ( const TMapBase& Other
) const

 Compare this map with another for equality. Containers/Map.h  

int32 Remove ( KeyConstPointerType InKey
)

 Remove all value associations for a key. Containers/Map.h  

void Remove ( FSetElementId Id
)

 Removes the element at the specified index. The caller has to ensure that the index is valid. Containers/Map.h  

int32 RemoveByHash ( uint32 KeyHash,
const ComparableKey& Key
)

 See Remove() and class documentation section on ByHash() functions Containers/Map.h  

void Reserve ( int32 Number
)

 Preallocates enough memory to contain Number elements Containers/Map.h  

void Reset()

 Efficiently empties out the map but preserves all allocations and capacities Containers/Map.h  

void Shrink()

 Shrinks the pair set to avoid slack. Containers/Map.h  

void WriteMemoryImage ( FMemoryImageWriter& Writer
) const

   Containers/Map.h  

Protected

Static

Name Remarks Include Path Unreal Specifiers

static void AppendHash ( const FPlatformTypeLayoutParameters& LayoutParams,
FSHA1& Hasher
)

   Containers/Map.h  

static uint32 HashKey ( const KeyType& Key
)

   Containers/Map.h  

Operators

Name Remarks Include Path Unreal Specifiers

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

 Assignment operator for copying elements from a TMap with a different SetAllocator Containers/Map.h  

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

 End - intrusive TOptional state //. Containers/Map.h  

TMapBase & operator= ( const TMapBase&
)

   Containers/Map.h  
  Containers/Map.h  

bool operator== ( FIntrusiveUnsetOptionalState Tag
) const

   Containers/Map.h  

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