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io_context::strand

Provides serialised handler execution.

class strand
Member Functions

Name

Description

context

Obtain the underlying execution context.

defer

Request the strand to invoke the given function object.

dispatch

Request the strand to invoke the given function object.

(Deprecated: Use boost::asio::dispatch().) Request the strand to invoke the given handler.

get_io_context

(Deprecated: Use context().) Get the io_context associated with the strand.

get_io_service

(Deprecated: Use context().) Get the io_context associated with the strand.

on_work_finished

Inform the strand that some work is no longer outstanding.

on_work_started

Inform the strand that it has some outstanding work to do.

post

Request the strand to invoke the given function object.

(Deprecated: Use boost::asio::post().) Request the strand to invoke the given handler and return immediately.

running_in_this_thread

Determine whether the strand is running in the current thread.

strand

Constructor.

wrap

(Deprecated: Use boost::asio::bind_executor().) Create a new handler that automatically dispatches the wrapped handler on the strand.

~strand

Destructor.

Friends

Name

Description

operator!=

Compare two strands for inequality.

operator==

Compare two strands for equality.

The io_context::strand class provides the ability to post and dispatch handlers with the guarantee that none of those handlers will execute concurrently.

Order of handler invocation

Given:

if any of the following conditions are true:

then asio_handler_invoke(a1, &a1) happens-before asio_handler_invoke(b1, &b1).

Note that in the following case:

async_op_1(..., s.wrap(a));
async_op_2(..., s.wrap(b));

the completion of the first async operation will perform s.dispatch(a), and the second will perform s.dispatch(b), but the order in which those are performed is unspecified. That is, you cannot state whether one happens-before the other. Therefore none of the above conditions are met and no ordering guarantee is made.

Remarks

The implementation makes no guarantee that handlers posted or dispatched through different strand objects will be invoked concurrently.

Thread Safety

Distinct objects: Safe.

Shared objects: Safe.

Requirements

Header: boost/asio/io_context_strand.hpp

Convenience header: boost/asio.hpp


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