...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Typedef for the typical usage of a signal set.
typedef basic_signal_set signal_set;
Name |
Description |
---|---|
The type of the executor associated with the object. |
Name |
Description |
---|---|
Add a signal to a signal_set. |
|
Start an asynchronous operation to wait for a signal to be delivered. |
|
Construct a signal set without adding any signals. |
|
Cancel all operations associated with the signal set. |
|
Remove all signals from a signal_set. |
|
Get the executor associated with the object. |
|
Remove a signal from a signal_set. |
|
Destroys the signal set. |
The basic_signal_set
class provides the ability to perform an asynchronous wait for one or more
signals to occur.
Distinct objects: Safe.
Shared objects: Unsafe.
Performing an asynchronous wait:
void handler( const boost::system::error_code& error, int signal_number) { if (!error) { // A signal occurred. } } ... // Construct a signal set registered for process termination. boost::asio::signal_set signals(my_context, SIGINT, SIGTERM); // Start an asynchronous wait for one of the signals to occur. signals.async_wait(handler);
If a signal is registered with a signal_set, and the signal occurs when there are no waiting handlers, then the signal notification is queued. The next async_wait operation on that signal_set will dequeue the notification. If multiple notifications are queued, subsequent async_wait operations dequeue them one at a time. Signal notifications are dequeued in order of ascending signal number.
If a signal number is removed from a signal_set (using the remove
or erase
member functions) then any queued notifications for
that signal are discarded.
The same signal number may be registered with different signal_set objects. When the signal occurs, one handler is called for each signal_set object.
Note that multiple registration only works for signals that are registered
using Asio. The application must not also register a signal handler using
functions such as signal()
or sigaction()
.
POSIX allows signals to be blocked using functions such as sigprocmask()
and pthread_sigmask()
. For signals to be delivered, programs
must ensure that any signals registered using signal_set objects are unblocked
in at least one thread.
Header: boost/asio/signal_set.hpp
Convenience header: boost/asio.hpp