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Timer service requirements

A timer service must meet the requirements for an I/O object service, as well as the additional requirements listed below.

In the table below, X denotes a timer service class for time type Time and traits type TimeTraits, a denotes a value of type X, b denotes a value of type X::implementation_type, t denotes a value of type Time, d denotes a value of type TimeTraits::duration_type, e denotes a value of type error_code, and h denotes a value meeting WaitHandler requirements.

Table 36. TimerService requirements

expression

return type

assertion/note
pre/post-condition

a.destroy(b);

From IoObjectService requirements. Implicitly cancels asynchronous wait operations, as if by calling a.cancel(b, e).

a.cancel(b, e);

size_t

Causes any outstanding asynchronous wait operations to complete as soon as possible. Handlers for cancelled operations shall be passed the error code error::operation_aborted. Sets e to indicate success or failure. Returns the number of operations that were cancelled.

a.expires_at(b);

Time

a.expires_at(b, t, e);

size_t

Implicitly cancels asynchronous wait operations, as if by calling a.cancel(b, e). Returns the number of operations that were cancelled.
post: a.expires_at(b) == t.

a.expires_from_now(b);

TimeTraits::duration_type

Returns a value equivalent to TimeTraits::subtract(a.expires_at(b), TimeTraits::now()).

a.expires_from_now(b, d, e);

size_t

Equivalent to a.expires_at(b, TimeTraits::add(TimeTraits::now(), d), e).

a.wait(b, e);

error_code

Sets e to indicate success or failure. Returns e.
post: !!e || !TimeTraits::lt(TimeTraits::now(), a.expires_at(b)).

a.async_wait(b, h);

Initiates an asynchronous wait operation that is performed via the io_service object a.io_service() and behaves according to asynchronous operation requirements.

The handler shall be posted for execution only if the condition !!ec || !TimeTraits::lt(TimeTraits::now(), a.expires_at(b)) holds, where ec is the error code to be passed to the handler.



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