dpp::awaitable< T > Class Template Reference

Generic awaitable class, represents a future value that can be co_await-ed on. More...

#include <awaitable.h>

Inheritance diagram for dpp::awaitable< T >:

Collaboration diagram for dpp::awaitable< T >:

Classes
struct	awaiter
	Awaiter returned by co_await. More...

Public Member Functions
	awaitable ()=default
	Construct an empty awaitable.
	awaitable (awaitable &&rhs) noexcept
	Move from another awaitable.
	awaitable (const awaitable &)=delete
	Copy construction is disabled.
	~awaitable ()
	Destructor.
bool	await_ready () const
	Check whether or not co_await-ing this would suspend the caller, i.e. if we have the result or not.
void	if_this_causes_an_invalid_read_your_promise_was_destroyed_before_your_awaitable____check_your_promise_lifetime ()
	Title :).
awaitable &	operator= (awaitable &&rhs) noexcept
	Move from another awaitable.
awaitable &	operator= (const awaitable &)=delete
	Copy assignment is disabled.
auto	sync_wait ()
	Blocks this thread and waits for the awaitable to finish.
auto	sync_wait_for (const std::chrono::duration< Rep, Period > &duration)
	Blocks this thread and waits for the awaitable to finish.
auto	sync_wait_until (const std::chrono::time_point< Clock, Duration > &time)
	Blocks this thread and waits for the awaitable to finish.
bool	valid () const noexcept
	Check whether this awaitable refers to a valid promise.

Protected Types
using	result_type = T
	The type of the result produced by this task.
using	shared_state = detail::promise::promise_base<T>
using	state_flags = detail::promise::state_flags

Protected Member Functions
	awaitable (shared_state *promise) noexcept
	Construct from a promise.
uint8_t	abandon ()
	Abandons the promise.
auto	sync_wait_impl (auto &&do_wait)
	Implementation for sync_wait. This is code used by sync_wait, sync_wait_for, sync_wait_until.

Protected Attributes
shared_state *	state_ptr = nullptr
	Non-owning pointer to the promise, which must be kept alive for the entire lifetime of the awaitable.

Friends
class	detail::promise::promise_base< T >
template<typename Derived> requires (std::is_base_of_v<awaitable, std::remove_cv_t<Derived>>)
awaiter< Derived && >	operator co_await (Derived &&obj) noexcept
	Overload of the co_await operator. Returns an awaiter referencing this awaitable.
template<typename Derived> requires (std::is_base_of_v<awaitable, std::remove_cv_t<Derived>>)
awaiter< Derived & >	operator co_await (Derived &obj) noexcept
	Overload of the co_await operator.

Detailed Description

template<typename T>
class dpp::awaitable< T >

Generic awaitable class, represents a future value that can be co_await-ed on.

Roughly equivalent of std::future for coroutines, with the crucial distinction that the future does not own a reference to a "shared state". It holds a non-owning reference to the promise, which must be kept alive for the entire lifetime of the awaitable.

Template Parameters

T	Type of the asynchronous value

See also

promise

Member Typedef Documentation

result_type

template<typename T>

using dpp::awaitable< T >::result_type = T

protected

The type of the result produced by this task.

shared_state

template<typename T>

using dpp::awaitable< T >::shared_state = detail::promise::promise_base<T>

protected

state_flags

template<typename T>

using dpp::awaitable< T >::state_flags = detail::promise::state_flags

protected

Constructor & Destructor Documentation

awaitable() [1/4]

template<typename T>

dpp::awaitable< T >::awaitable ( shared_state * promise )

inlineprotectednoexcept

Construct from a promise.

Parameters

promise

The promise to refer to.

awaitable() [2/4]

template<typename T>

dpp::awaitable< T >::awaitable ( )

default

Construct an empty awaitable.

Such an awaitable must be assigned a promise before it can be awaited.

awaitable() [3/4]

template<typename T>

dpp::awaitable< T >::awaitable ( const awaitable< T > & )

delete

Copy construction is disabled.

awaitable() [4/4]

template<typename T>

dpp::awaitable< T >::awaitable ( awaitable< T > && rhs )

inlinenoexcept

Move from another awaitable.

Parameters

rhs	The awaitable to move from, left in an unspecified state after this.

~awaitable()

template<typename T>

dpp::awaitable< T >::~awaitable

(

)

Destructor.

May signal to the promise that it was destroyed.

Member Function Documentation

abandon()

template<typename T>

auto dpp::awaitable< T >::abandon ( )

protected

Abandons the promise.

Set the promise's state to broken and unlinks this awaitable.

Returns

uint8_t Flags previously held before setting them to broken

await_ready()

template<typename T>

bool dpp::awaitable< T >::await_ready

(

)

const

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 or not

if_this_causes_an_invalid_read_your_promise_was_destroyed_before_your_awaitable____check_your_promise_lifetime()

template<typename T>

void dpp::awaitable< T >::if_this_causes_an_invalid_read_your_promise_was_destroyed_before_your_awaitable____check_your_promise_lifetime ( )

inline

Title :).

We use this in the destructor

operator=() [1/2]

template<typename T>

awaitable & dpp::awaitable< T >::operator= ( awaitable< T > && rhs )

inlinenoexcept

Move from another awaitable.

Parameters

rhs	The awaitable to move from, left in an unspecified state after this.

Returns

*this

operator=() [2/2]

template<typename T>

awaitable & dpp::awaitable< T >::operator= ( const awaitable< T > & )

delete

Copy assignment is disabled.

sync_wait()

auto dpp::basic_awaitable< Derived >::sync_wait ( )

inlineinherited

Blocks this thread and waits for the awaitable to finish.

Attention

This will BLOCK THE THREAD. It is likely you want to use co_await instead.

Returns

If T is void, returns a boolean for which true means the awaitable completed, false means it timed out.

If T is non-void, returns a std::optional<T> for which an absence of value means timed out.

sync_wait_for()

auto dpp::basic_awaitable< Derived >::sync_wait_for ( const std::chrono::duration< Rep, Period > & duration )

inlineinherited

Blocks this thread and waits for the awaitable to finish.

Attention

This will BLOCK THE THREAD. It is likely you want to use co_await instead.

Parameters

duration

Maximum duration to wait for

Returns

If T is void, returns a boolean for which true means the awaitable completed, false means it timed out.

If T is non-void, returns a std::optional<T> for which an absence of value means timed out.

sync_wait_impl()

auto dpp::basic_awaitable< Derived >::sync_wait_impl ( auto && do_wait )

inlineprotectedinherited

Implementation for sync_wait. This is code used by sync_wait, sync_wait_for, sync_wait_until.

Template Parameters

Timed

Whether the wait function times out or not

Parameters

do_wait

Function to do the actual wait on the cv

Returns

If T is void, returns a boolean for which true means the awaitable completed, false means it timed out.

If T is non-void, returns a std::optional<T> for which an absence of value means timed out.

sync_wait_until()

auto dpp::basic_awaitable< Derived >::sync_wait_until ( const std::chrono::time_point< Clock, Duration > & time )

inlineinherited

Blocks this thread and waits for the awaitable to finish.

Attention

This will BLOCK THE THREAD. It is likely you want to use co_await instead.

Parameters

time	Maximum time point to wait for

Returns

If T is void, returns a boolean for which true means the awaitable completed, false means it timed out.

If T is non-void, returns a std::optional<T> for which an absence of value means timed out.

valid()

template<typename T>

bool dpp::awaitable< T >::valid ( ) const

noexcept

Check whether this awaitable refers to a valid promise.

Returns

bool Whether this awaitable refers to a valid promise or not

Friends And Related Symbol Documentation

detail::promise::promise_base< T >

template<typename T>

friend class detail::promise::promise_base< T >

friend

operator co_await [1/2]

template<typename T>

template<typename Derived>
requires (std::is_base_of_v<awaitable, std::remove_cv_t<Derived>>)

awaiter< Derived && > operator co_await ( Derived && obj )

friend

Overload of the co_await operator. Returns an awaiter referencing this awaitable.

Returns

Returns an awaiter referencing this awaitable.

operator co_await [2/2]

template<typename T>

template<typename Derived>
requires (std::is_base_of_v<awaitable, std::remove_cv_t<Derived>>)

awaiter< Derived & > operator co_await ( Derived & obj )

friend

Overload of the co_await operator.

Returns

Returns an awaiter referencing this awaitable.

Member Data Documentation

state_ptr

template<typename T>

shared_state* dpp::awaitable< T >::state_ptr = nullptr

protected

Non-owning pointer to the promise, which must be kept alive for the entire lifetime of the awaitable.