dpp::async< R > Class Template Reference

A co_await-able object handling an API call in parallel with the caller. More...

#include <coro/async.h>

Inheritance diagram for dpp::async< R >:

Collaboration diagram for dpp::async< R >:

Public Member Functions
template<typename Obj , typename Fun , typename... Args>
	async (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 (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 () noexcept
	Construct an empty async. Using co_await on an empty async is undefined behavior. More...
	~async ()
	Destructor. If any callback is pending it will be aborted. More...
	async (const async &)
	Copy constructor is disabled. More...
	async (async &&other) noexcept=default
	Move constructor. More...
async &	operator= (const async &)=delete
	Copy assignment is disabled. More...
async &	operator= (async &&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...
auto &	operator co_await () &noexcept
	Suspend the caller until the request completes. More...
const auto &	operator co_await () const &noexcept
	Suspend the caller until the request completes. More...
auto &&	operator co_await () &&noexcept
	Suspend the caller until the request completes. More...

Friends
class	detail::async::async_base< R >
	Internal use only base class. It serves to prevent await_suspend and await_resume from being used directly. More...

Detailed Description

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

A co_await-able object handling an API call in parallel with the caller.

This class is the return type of the dpp::cluster::co_* methods, but it can also be created manually to wrap any async call.

Remarks

- The coroutine may be resumed in another thread, do not rely on thread_local variables.

Warning

- This feature is EXPERIMENTAL. The API may change at any time and there may be bugs. Please report any to GitHub issues or to the D++ Discord server.

Template Parameters

R	The return type of the API call. Defaults to confirmation_callback_t

Constructor & Destructor Documentation

async() [1/5]

template<typename R >

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

dpp::async< R >::async ( 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() [2/5]

template<typename R >

template<typename Fun , typename... Args>

dpp::async< R >::async ( 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() [3/5]

template<typename R >

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

noexcept

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

~async()

template<typename R >

dpp::async< R >::~async

(

)

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

async() [4/5]

template<typename R >

dpp::async< R >::async

(

const async< R > &

)

Copy constructor is disabled.

async() [5/5]

template<typename R >

dpp::async< R >::async ( async< 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::async< R >::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.

Returns

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

operator co_await() [1/3]

template<typename R >

auto && dpp::async< R >::operator co_await ( ) &&

inlinenoexcept

Suspend the caller until the request completes.

Returns

On resumption, this expression evaluates to the result object of type R, as an rvalue reference.

operator co_await() [2/3]

template<typename R >

auto & dpp::async< R >::operator co_await ( ) &

inlinenoexcept

Suspend the caller until the request completes.

Returns

On resumption, this expression evaluates to the result object of type R, as a reference.

operator co_await() [3/3]

template<typename R >

const auto & dpp::async< R >::operator co_await ( ) const &

inlinenoexcept

Suspend the caller until the request completes.

Returns

On resumption, this expression evaluates to the result object of type R, as a const reference.

operator=() [1/2]

template<typename R >

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

delete

Copy assignment is disabled.

Friends And Related Function Documentation

detail::async::async_base< R >

template<typename R >

friend class detail::async::async_base< R >

friend

Internal use only base class. It serves to prevent await_suspend and await_resume from being used directly.

Warning

For internal use only, do not use.

See also

operator co_await()