io_service object's event processing
function blocks until all work has finished and there are no more handlers
to be dispatched, or until the
io_service has been stopped.
Multiple threads may call the
run() function to set up a pool of threads
from which the
io_service may execute handlers.
All threads that are waiting in the pool are equivalent and the
may choose any one of them to invoke a handler.
function may be safely called again once it has completed only after
a call to
The number of handlers that were executed.
Thrown on failure.
function must not be called from a thread that is currently calling one
on the same
function may also be used to dispatch ready handlers, but without blocking.