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Provides serialised handler execution.
class strand
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Name |
Description |
|---|---|
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Request the strand to invoke the given handler. |
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Get the io_service associated with the strand. |
|
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Request the strand to invoke the given handler and return immediately. |
|
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Determine whether the strand is running in the current thread. |
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Constructor. |
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Create a new handler that automatically dispatches the wrapped handler on the strand. |
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Destructor. |
The io_service::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: asio/strand.hpp
Convenience header: asio.hpp