dpp::detail::async::async_base< R > Class Template Reference

Base class of dpp::async. More...

#include <async.h>

Inheritance diagram for dpp::detail::async::async_base< R >:

Public Member Functions
template<typename Obj , typename Fun , typename... Args>
	async_base (Obj &&obj, Fun &&fun, Args &&... args)
	Construct an async object wrapping an object method, the call is made immediately by forwarding to std::invoke and can be awaited later to retrieve the result. More...
template<typename Fun , typename... Args>
	async_base (Fun &&fun, Args &&... args)
	Construct an async object wrapping an invokeable object, the call is made immediately by forwarding to std::invoke and can be awaited later to retrieve the result. More...
	async_base () noexcept
	Construct an empty async. Using co_await on an empty async is undefined behavior. More...
	~async_base ()
	Destructor. If any callback is pending it will be aborted. More...
	async_base (const async_base &)=delete
	Copy constructor is disabled. More...
	async_base (async_base &&other) noexcept=default
	Move constructor. More...
async_base &	operator= (const async_base &)=delete
	Copy assignment is disabled. More...
async_base &	operator= (async_base &&other) noexcept=default
	Move assignment operator. More...
bool	await_ready () const noexcept
	Check whether or not co_await-ing this would suspend the caller, i.e. if we have the result or not. More...
bool	await_suspend (detail::std_coroutine::coroutine_handle<> caller) noexcept
	Second function called by the standard library when the object is co-awaited, if await_ready returned false. More...
R &	await_resume () &noexcept
	Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to. More...
const R &	await_resume () const &noexcept
	Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to. More...
R &&	await_resume () &&noexcept
	Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to. More...

Detailed Description

template<typename R>
class dpp::detail::async::async_base< R >

Base class of dpp::async.

Warning

This class should not be used directly by a user, use dpp::async instead.

Note

This class contains all the functions used internally by co_await. It is intentionally opaque and a private base of dpp::async so a user cannot call await_suspend and await_resume directly.

Constructor & Destructor Documentation

async_base() [1/5]

template<typename R >

template<typename Obj , typename Fun , typename... Args>

dpp::detail::async::async_base< R >::async_base ( Obj &&  obj, Fun &&  fun, Args &&...  args  )

inlineexplicit

Construct an async object wrapping an object method, the call is made immediately by forwarding to std::invoke and can be awaited later to retrieve the result.

Parameters

obj	The object to call the method on
fun	The method of the object to call. Its last parameter must be a callback taking a parameter of type R
args	Parameters to pass to the method, excluding the callback

async_base() [2/5]

template<typename R >

template<typename Fun , typename... Args>

dpp::detail::async::async_base< R >::async_base ( Fun &&  fun, Args &&...  args  )

inlineexplicit

Construct an async object wrapping an invokeable object, the call is made immediately by forwarding to std::invoke and can be awaited later to retrieve the result.

Parameters

fun	The object to call using std::invoke. Its last parameter must be a callable taking a parameter of type R
args	Parameters to pass to the object, excluding the callback

async_base() [3/5]

template<typename R >

dpp::detail::async::async_base< R >::async_base ( )

inlinenoexcept

Construct an empty async. Using co_await on an empty async is undefined behavior.

~async_base()

template<typename R >

dpp::detail::async::async_base< R >::~async_base ( )

inline

Destructor. If any callback is pending it will be aborted.

async_base() [4/5]

template<typename R >

dpp::detail::async::async_base< R >::async_base ( const async_base< R > &  )

delete

Copy constructor is disabled.

async_base() [5/5]

template<typename R >

dpp::detail::async::async_base< R >::async_base ( async_base< R > &&  other )

defaultnoexcept

Move constructor.

NOTE: Despite being marked noexcept, this function uses std::lock_guard which may throw. The implementation assumes this can never happen, hence noexcept. Report it if it does, as that would be a bug.

Remarks

Using the moved-from async after this function is undefined behavior.

Parameters

other

The async object to move the data from.

Member Function Documentation

await_ready()

template<typename R >

bool dpp::detail::async::async_base< R >::await_ready ( ) const

inlinenoexcept

Check whether or not co_await-ing this would suspend the caller, i.e. if we have the result or not.

Returns

bool Whether we already have the result of the API call or not

await_resume() [1/3]

template<typename R >

R && dpp::detail::async::async_base< R >::await_resume ( ) &&

inlinenoexcept

Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to.

Remarks

Do not call this manually, use the co_await keyword instead.

Returns

The result of the API call as an rvalue reference.

await_resume() [2/3]

template<typename R >

R & dpp::detail::async::async_base< R >::await_resume ( ) &

inlinenoexcept

Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to.

Remarks

Do not call this manually, use the co_await keyword instead.

Returns

The result of the API call as an lvalue reference.

await_resume() [3/3]

template<typename R >

const R & dpp::detail::async::async_base< R >::await_resume ( ) const &

inlinenoexcept

Function called by the standard library when the async is resumed. Its return value is what the whole co_await expression evaluates to.

Remarks

Do not call this manually, use the co_await keyword instead.

Returns

The result of the API call as a const lvalue reference.

await_suspend()

template<typename R >

bool dpp::detail::async::async_base< R >::await_suspend ( detail::std_coroutine::coroutine_handle<>  caller )

inlinenoexcept

Second function called by the standard library when the object is co-awaited, if await_ready returned false.

Checks again for the presence of the result, if absent, signals to suspend and keep track of the calling coroutine for the callback to resume.

Remarks

Do not call this manually, use the co_await keyword instead.

Parameters

caller

The handle to the coroutine co_await-ing and being suspended

operator=() [1/2]

template<typename R >

async_base & dpp::detail::async::async_base< R >::operator= ( async_base< R > &&  other )

defaultnoexcept

Move assignment operator.

NOTE: Despite being marked noexcept, this function uses std::lock_guard which may throw. The implementation assumes this can never happen, hence noexcept. Report it if it does, as that would be a bug.

Remarks

Using the moved-from async after this function is undefined behavior.

Parameters

other

The async object to move the data from

operator=() [2/2]

template<typename R >

async_base & dpp::detail::async::async_base< R >::operator= ( const async_base< R > &  )

delete

Copy assignment is disabled.