This class represents a thread-safe handle to a promised future result of an asynchronous operation, providing methods to query its status and result as well as register callbacks for this future's completion. More...

#include "asyncFuture.h"

Inheritance diagram for AsyncFuture:

Public Types
typedef pvector< PT(AsyncFuture)>	Futures

Public Member Functions
	AsyncFuture ()
	Initializes the future in the pending state. More...

virtual	~AsyncFuture ()
	Destroys the future. More...

bool	add_waiting_task (AsyncTask *task)
	Indicates that the given task is waiting for this future to complete. More...

virtual bool	cancel ()
	Cancels the future. More...

bool	cancelled () const
	Returns true if the future was cancelled. More...

bool	done () const
	Returns true if the future is done or has been cancelled. More...

virtual TypeHandle	force_init_type ()

const std::string &	get_done_event () const

TypedObject *	get_result () const
	Returns this future's result. More...

void	get_result (TypedObject &ptr, ReferenceCount &ref_ptr) const
	Returns this future's result as a pair of TypedObject, ReferenceCount pointers. More...

virtual TypeHandle	get_type () const

virtual bool	is_task () const

void	notify_done (bool clean_exit)
	Schedules the done callbacks. More...

virtual void	output (std::ostream &out) const

void	set_done_event (const std::string &done_event)

void	set_result (std::nullptr_t)
	Sets this future's result. More...

void	set_result (TypedObject *result)

void	set_result (TypedReferenceCount *result)

void	set_result (TypedWritableReferenceCount *result)

void	set_result (const EventParameter &result)

void	set_result (TypedObject ptr, ReferenceCount ref_ptr)
	Sets this future's result. More...

void	wait ()
	Waits until the future is done. More...

void	wait (double timeout)
	Waits until the future is done, or until the timeout is reached. More...

Public Member Functions inherited from TypedReferenceCount
	TypedReferenceCount (const TypedReferenceCount &copy)

void	operator= (const TypedReferenceCount &copy)

Public Member Functions inherited from TypedObject
	TypedObject (const TypedObject &copy)=default

TypedObject *	as_typed_object ()
	Returns the object, upcast (if necessary) to a TypedObject pointer. More...

const TypedObject *	as_typed_object () const
	Returns the object, upcast (if necessary) to a TypedObject pointer. More...

int	get_best_parent_from_Set (const std::set< int > &) const

int	get_type_index () const
	Returns the internal index number associated with this object's TypeHandle, a unique number for each different type. More...

bool	is_exact_type (TypeHandle handle) const
	Returns true if the current object is the indicated type exactly. More...

bool	is_of_type (TypeHandle handle) const
	Returns true if the current object is or derives from the indicated type. More...

TypedObject &	operator= (const TypedObject &copy)=default

Public Member Functions inherited from ReferenceCount
int	get_ref_count () const

WeakReferenceList *	get_weak_list () const
	Returns the WeakReferenceList associated with this ReferenceCount object. More...

bool	has_weak_list () const
	Returns true if this particular ReferenceCount object has a WeakReferenceList created, false otherwise. More...

void	local_object ()
	This function should be called, once, immediately after creating a new instance of some ReferenceCount-derived object on the stack. More...

void	ref () const
	Explicitly increments the reference count. More...

bool	ref_if_nonzero () const
	Atomically increases the reference count of this object if it is not zero. More...

bool	test_ref_count_integrity () const
	Does some easy checks to make sure that the reference count isn't completely bogus. More...

bool	test_ref_count_nonzero () const
	Does some easy checks to make sure that the reference count isn't zero, or completely bogus. More...

virtual bool	unref () const
	Explicitly decrements the reference count. More...

WeakReferenceList *	weak_ref ()
	Adds the indicated PointerToVoid as a weak reference to this object. More...

void	weak_unref ()
	Removes the indicated PointerToVoid as a weak reference to this object. More...

Static Public Member Functions
static AsyncFuture *	gather (Futures futures)
	Creates a new future that returns `done()` when all of the contained futures are done. More...

static TypeHandle	get_class_type ()

static void	init_type ()

Static Public Member Functions inherited from TypedReferenceCount
static TypeHandle	get_class_type ()

static void	init_type ()

Static Public Member Functions inherited from TypedObject
static TypeHandle	get_class_type ()

static void	init_type ()
	This function is declared non-inline to work around a compiler bug in g++ 2.96. More...

Static Public Member Functions inherited from ReferenceCount
static TypeHandle	get_class_type ()

static void	init_type ()

Public Attributes
	get_done_event
	Returns the event name that will be triggered when the future finishes. More...

	set_done_event
	Sets the event name that will be triggered when the future finishes. More...

Public Attributes inherited from TypedObject
	get_type

Public Attributes inherited from ReferenceCount
	get_ref_count
	Returns the current reference count. More...

Friends
class	AsyncGatheringFuture

class	AsyncTaskChain

class	PythonTask

Detailed Description

This class represents a thread-safe handle to a promised future result of an asynchronous operation, providing methods to query its status and result as well as register callbacks for this future's completion.

An AsyncFuture can be awaited from within a coroutine or task. It keeps track of tasks waiting for this future and automatically reactivates them upon this future's completion.

A task itself is also a subclass of AsyncFuture. Other subclasses are not generally necessary, except to override the function of `cancel()`.

Until the future is done, it is "owned" by the resolver thread, though it's still legal for other threads to query its state. When the resolver thread resolves this future using `set_result()`, or any thread calls `cancel()`, it instantly enters the "done" state, after which the result becomes a read-only field that all threads can access.

When the future returns true for done(), a thread can use cancelled() to determine whether the future was cancelled or get_result() to access the result of the operation. Not all operations define a meaningful result value, so some will always return nullptr.

In Python, the `cancelled()`, `wait()` and `get_result()` methods are wrapped up into a single `result()` method which waits for the future to complete before either returning the result or throwing an exception if the future was cancelled. However, it is preferable to use the `await` keyword when running from a coroutine, which only suspends the current task and not the entire thread.

This API aims to mirror and be compatible with Python's Future class.

Since: 1.10.0

Definition at line 61 of file asyncFuture.h.

Constructor & Destructor Documentation

◆ AsyncFuture()

AsyncFuture::AsyncFuture ( )

inline

Initializes the future in the pending state.

Definition at line 18 of file asyncFuture.I.

Referenced by gather().

◆ ~AsyncFuture()

AsyncFuture::~AsyncFuture ( )

virtual

Destroys the future.

Assumes notify_done() has already been called.

Definition at line 29 of file asyncFuture.cxx.

Member Function Documentation

◆ add_waiting_task()

bool AsyncFuture::add_waiting_task ( AsyncTask * task )

Indicates that the given task is waiting for this future to complete.

When the future is done, it will reactivate the given task. If this is called while the future is already done, schedules the task immediately. Assumes the manager's lock is not held.

Returns: true if the future was pending, false if it was already done.

Definition at line 219 of file asyncFuture.cxx.

◆ cancel()

bool AsyncFuture::cancel ( )

virtual

Cancels the future.

Returns true if it was cancelled, or false if the future was already done. Either way, done() will return true after this call returns.

In the case of a task, this is equivalent to remove().

Reimplemented in PreparedGraphicsObjects::EnqueuedObject, and AsyncGatheringFuture.

Definition at line 43 of file asyncFuture.cxx.

References notify_done().

Referenced by AsyncGatheringFuture::cancel().

◆ cancelled()

bool AsyncFuture::cancelled ( ) const

inline

Returns true if the future was cancelled.

It is always safe to call this.

Definition at line 37 of file asyncFuture.I.

References AtomicAdjustDummyImpl::get().

◆ done()

bool AsyncFuture::done ( ) const

inline

Returns true if the future is done or has been cancelled.

It is always safe to call this.

Definition at line 29 of file asyncFuture.I.

References AtomicAdjustDummyImpl::get().

Referenced by AsyncGatheringFuture::cancel(), and wait().

◆ gather()

AsyncFuture * AsyncFuture::gather ( Futures futures )

inlinestatic

Creates a new future that returns `done()` when all of the contained futures are done.

Calling `cancel()` on the returned future will result in all contained futures that have not yet finished to be cancelled.

Definition at line 124 of file asyncFuture.I.

References AsyncFuture().

◆ get_result() [1/2]

TypedObject * AsyncFuture::get_result ( ) const

inline

Returns this future's result.

Can only be called if done() returns true.

Definition at line 65 of file asyncFuture.I.

◆ get_result() [2/2]

void AsyncFuture::get_result	(	TypedObject *&	ptr,
		ReferenceCount *&	ref_ptr
	)		const

inline

Returns this future's result as a pair of TypedObject, ReferenceCount pointers.

Can only be called if done() returns true.

Definition at line 77 of file asyncFuture.I.

◆ notify_done()

void AsyncFuture::notify_done ( bool clean_exit )

Schedules the done callbacks.

Called after the future has just entered the 'done' state.

Parameters

clean_exit true if finished successfully, false if cancelled.

Definition at line 132 of file asyncFuture.cxx.

Referenced by cancel(), AsyncGatheringFuture::cancel(), and set_result().

◆ set_result() [1/2]

void AsyncFuture::set_result ( std::nullptr_t )

inline

Sets this future's result.

Can only be called if done() returns false.

Definition at line 92 of file asyncFuture.I.

◆ set_result() [2/2]

void AsyncFuture::set_result	(	TypedObject *	ptr,
		ReferenceCount *	ref_ptr
	)

Sets this future's result.

Can only be done while the future is not done. Calling this marks the future as done and schedules the done callbacks.

This variant takes two pointers; the second one is only set if this object inherits from ReferenceCount, so that a reference can be held.

Assumes the manager's lock is *not* held.

Definition at line 176 of file asyncFuture.cxx.

References Thread::force_yield(), and notify_done().

◆ wait() [1/2]

void AsyncFuture::wait ( )

Waits until the future is done.

Definition at line 82 of file asyncFuture.cxx.

References done(), and Thread::force_yield().

◆ wait() [2/2]

void AsyncFuture::wait ( double timeout )

Waits until the future is done, or until the timeout is reached.

Definition at line 105 of file asyncFuture.cxx.

References done(), Thread::force_yield(), ClockObject::get_global_clock(), and ClockObject::get_real_time.

Member Data Documentation

◆ get_done_event

const std::string & AsyncFuture::get_done_event

inline

Returns the event name that will be triggered when the future finishes.

See set_done_event().

Definition at line 77 of file asyncFuture.h.

◆ set_done_event

void AsyncFuture::set_done_event

inline

Sets the event name that will be triggered when the future finishes.

Will not be triggered if the future is cancelled, but it will be triggered for a coroutine task that exits with an exception.

Definition at line 77 of file asyncFuture.h.

The documentation for this class was generated from the following files:

panda/src/event/asyncFuture.h
panda/src/event/asyncFuture.cxx
panda/src/event/asyncFuture.I

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ AsyncFuture()

◆ ~AsyncFuture()

Member Function Documentation

◆ add_waiting_task()

◆ cancel()

◆ cancelled()

◆ done()

◆ gather()

◆ get_result() [1/2]

◆ get_result() [2/2]

◆ notify_done()

◆ set_result() [1/2]

◆ set_result() [2/2]

◆ wait() [1/2]

◆ wait() [2/2]

Member Data Documentation

◆ get_done_event

◆ set_done_event