...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Provides serialised handler execution.
class strand
Name |
Description |
---|---|
Obtain the underlying execution context. |
|
Request the strand to invoke the given function object. |
|
Request the strand to invoke the given function object. (Deprecated: Use boost::asio::dispatch().) Request the strand to invoke the given handler. |
|
(Deprecated: Use context().) Get the io_context associated with the strand. |
|
(Deprecated: Use context().) Get the io_context associated with the strand. |
|
Inform the strand that some work is no longer outstanding. |
|
Inform the strand that it has some outstanding work to do. |
|
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. |
|
Determine whether the strand is running in the current thread. |
|
Constructor. |
|
(Deprecated: Use boost::asio::bind_executor().) Create a new handler that automatically dispatches the wrapped handler on the strand. |
|
Destructor. |
Name |
Description |
---|---|
Compare two strands for inequality. |
|
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.
Given:
s
a
meeting completion handler requirements
a1
which is an arbitrary copy of a
made by the implementation
b
meeting completion handler requirements
b1
which is an arbitrary copy of b
made by the implementation
if any of the following conditions are true:
s.post(a)
happens-before s.post(b)
s.post(a)
happens-before s.dispatch(b)
, where
the latter is performed outside the strand
s.dispatch(a)
happens-before s.post(b)
, where
the former is performed outside the strand
s.dispatch(a)
happens-before s.dispatch(b)
,
where both are performed outside the strand
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.
The implementation makes no guarantee that handlers posted or dispatched
through different strand
objects will be invoked concurrently.
Distinct objects: Safe.
Shared objects: Safe.
Header: boost/asio/io_context_strand.hpp
Convenience header: boost/asio.hpp