1. Epic GamesDeveloper
  3. FTaskBase

FTaskBase

An abstract base class for task implementation.

API > API/Runtime > API/Runtime/Core

An abstract base class for task implementation. Implements internal logic of task prerequisites, nested tasks and deep task retraction. Implements intrusive ref-counting and so can be used with TRefCountPtr. It doesn't store task body, instead it expects a derived class to provide a task body as a parameter to `TryExecute_ method.

   
Name FTaskBase
Type class
Header File /Engine/Source/Runtime/Core/Public/Tasks/TaskPrivate.h
Include Path #include "Tasks/TaskPrivate.h"

Syntax

class FTaskBase : private UE::FInheritedContextBase

Inheritance Hierarchy

Derived Classes

FTaskBase derived class hierarchy

Constructors

Name Remarks Include Path Unreal Specifiers
  Tasks/TaskPrivate.h  

FTaskBase ( const FTaskBase&
)

   Tasks/TaskPrivate.h  

FTaskBase ( uint32 InitRefCount,
bool bUnlockPrerequisites
)

   Tasks/TaskPrivate.h  

Destructors

Name Remarks Include Path Unreal Specifiers

virtual ~FTaskBase()

   Tasks/TaskPrivate.h  

Classes

Name Remarks
FPrerequisites Stores backlinks to prerequsites, either execution prerequisites or nested tasks (completion prerequisites).
FSubsequents The task is completed when its subsequents list is closed and no more can be added

Constants

Name Type Remarks Include Path
ExecutionFlag uint32 ExecutionFlag_ is set at the beginning of execution as the most significant bit of NumLocks_ and indicates a switch of `NumLocks_ from "execution prerequisites" (a number of uncompleted prerequisites that block task execution) to "completion prerequisites" (a number of nested uncompleted tasks that block task completion) Tasks/TaskPrivate.h
NumInitialLocks uint32 The number of times that the task should be unlocked before it can be scheduled or completed initial count is 1 for launching the task (it can't be scheduled before it's launched) reaches 0 the task is scheduled for execution. Tasks/TaskPrivate.h

Variables

Protected

Name Type Remarks Include Path Unreal Specifiers
ExecutingThreadId std::atomic< uint32 >   Tasks/TaskPrivate.h  
ExtendedPriority EExtendedTaskPriority   Tasks/TaskPrivate.h  
LowLevelTask LowLevelTasks::FTask   Tasks/TaskPrivate.h  
NumLocks std::atomic< uint32 >   Tasks/TaskPrivate.h  
Pipe FPipe *   Tasks/TaskPrivate.h  
Prerequisites FPrerequisites< TInlineAllocator< 1 > >   Tasks/TaskPrivate.h  
RefCount std::atomic< uint32 >   Tasks/TaskPrivate.h  
StateChangeEvent FEventCount   Tasks/TaskPrivate.h  
Subsequents FSubsequents< TInlineAllocator< 1 > >   Tasks/TaskPrivate.h  
TaskTriggered std::atomic< bool > Note: Only ever set when the task is launched from Trigger() Tasks/TaskPrivate.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

void AddNested ( FTaskBase& Nested
)

 Adds a nested task that must be completed before the parent (this) is completed Tasks/TaskPrivate.h  

bool AddPrerequisites ( const HigherLevelTaskType& Prerequisite
)

 The task will be executed only when all prerequisites are completed. Tasks/TaskPrivate.h  

void AddPrerequisites ( const PrerequisiteCollectionType& InPrerequisites
)

 The task will be executed only when all prerequisites are completed. Tasks/TaskPrivate.h  

bool AddPrerequisites ( const HigherLevelTaskType& Prerequisite
)

 The task will be executed only when all prerequisites are completed. Tasks/TaskPrivate.h  

bool AddPrerequisites ( FTaskBase& Prerequisite
)

 The task will be executed only when all prerequisites are completed. Tasks/TaskPrivate.h  

void AddRef()

 Ref-count Tasks/TaskPrivate.h  

bool AddSubsequent ( FTaskBase& Subsequent
)

 The task unlocks all its subsequents on completion. Tasks/TaskPrivate.h  

EExtendedTaskPriority GetExtendedPriority()

   Tasks/TaskPrivate.h  

FPipe * GetPipe()

   Tasks/TaskPrivate.h  

ETaskPriority GetPriority()

   Tasks/TaskPrivate.h  

uint32 GetRefCount ( std::memory_order MemoryOrder
) const

   Tasks/TaskPrivate.h  

TaskTrace::FId GetTraceId()

   Tasks/TaskPrivate.h  

bool IsAwaitable ()

 Returns true if it's valid to wait for the task completion. Tasks/TaskPrivate.h  

bool IsCompleted()

   Tasks/TaskPrivate.h  

bool IsNamedThreadTask()

   Tasks/TaskPrivate.h  

void Release()

   Tasks/TaskPrivate.h  
Releases internal reference and maintains low-level task state. Tasks/TaskPrivate.h  

void SetPipe ( FPipe& InPipe
)

 A piped task is executed after the previous task from this pipe is completed. Tasks/TaskPrivate.h  

bool Trigger ( uint64 TaskSize
)

 Tries to schedule task execution but has additional tracking to ensure a task is not scheduled more than once. Tasks/TaskPrivate.h  

bool TryLaunch ( uint64 TaskSize
)

 Tries to schedule task execution. Tasks/TaskPrivate.h  

bool TryRetractAndExecute ( FTimeout Timeout,
uint32 RecursionDepth
)

 Tries to pull out the task from the system and execute it. Tasks/TaskPrivate.h  

void Wait ()

 Waits for task's completion. Tasks/TaskPrivate.h  

bool Wait ( FTimeout Timeout
)

 Waits for task's completion, with optional timeout. Tasks/TaskPrivate.h  

void WaitWithNamedThreadsSupport()

 Mimics the old tasks (TaskGraph) behaviour on named threads: waiting for a task on a named thread pulls other tasks from this named thread queue and executes them Tasks/TaskPrivate.h  

Protected

Name Remarks Include Path Unreal Specifiers

void AddPrerequisites ( const PrerequisiteCollectionType& InPrerequisites,
bool bLockPrerequisite
)

 The task will be executed only when all prerequisites are completed. Tasks/TaskPrivate.h  

void ClearPipe()

   Tasks/TaskPrivate.h  

void Close()

 Closes task by unlocking its subsequents and flagging it as completed Tasks/TaskPrivate.h  

void ExecuteTask()

   Tasks/TaskPrivate.h  

void Init ( const TCHAR* InDebugName,
ETaskPriority InPriority,
EExtendedTaskPriority InExtendedPriority,
ETaskFlags Flags
)

   Tasks/TaskPrivate.h  

bool TryExecuteTask ()

 Tries to get execution permission and if successful, executes given task body and completes the task if there're no pending nested tasks. Tasks/TaskPrivate.h  

void UnlockPrerequisites()

   Tasks/TaskPrivate.h  

Operators

Name Remarks Include Path Unreal Specifiers
  Tasks/TaskPrivate.h  
  Tasks/TaskPrivate.h  

See Also

Ask questions and help your peers Developer Forums

Write your own tutorials or read those from others Learning Library

On this page