Provides waitable timer functionality.
template< typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>> class basic_deadline_timer : public basic_io_object< TimerService >
Name |
Description |
---|---|
The duration type. |
|
The underlying implementation type of I/O object. |
|
The type of the service that will be used to provide I/O operations. |
|
The time type. |
|
The time traits type. |
Name |
Description |
---|---|
Start an asynchronous wait on the timer. |
|
Constructor. Constructor to set a particular expiry time as an absolute time. Constructor to set a particular expiry time relative to now. |
|
Cancel any asynchronous operations that are waiting on the timer. |
|
Cancels one asynchronous operation that is waiting on the timer. |
|
Get the timer's expiry time as an absolute time. Set the timer's expiry time as an absolute time. |
|
Get the timer's expiry time relative to now. Set the timer's expiry time relative to now. |
|
Get the io_service associated with the object. |
|
Perform a blocking wait on the timer. |
Name |
Description |
---|---|
Get the underlying implementation of the I/O object. |
|
Get the service associated with the I/O object. |
Name |
Description |
---|---|
(Deprecated: Use get_implementation().) The underlying implementation of the I/O object. |
|
(Deprecated: Use get_service().) The service associated with the I/O object. |
The basic_deadline_timer
class template provides the ability to perform a blocking or asynchronous
wait for a timer to expire.
A deadline timer is always in one of two states: "expired" or "not
expired". If the wait()
or async_wait()
function is called on an expired timer,
the wait operation will complete immediately.
Most applications will use the deadline_timer
typedef.
Distinct objects: Safe.
Shared objects: Unsafe.
Performing a blocking wait:
// Construct a timer without setting an expiry time. asio::deadline_timer timer(io_service); // Set an expiry time relative to now. timer.expires_from_now(boost::posix_time::seconds(5)); // Wait for the timer to expire. timer.wait();
Performing an asynchronous wait:
void handler(const asio::error_code& error) { if (!error) { // Timer expired. } } ... // Construct a timer with an absolute expiry time. asio::deadline_timer timer(io_service, boost::posix_time::time_from_string("2005-12-07 23:59:59.000")); // Start an asynchronous wait. timer.async_wait(handler);
Changing the expiry time of a timer while there are pending asynchronous waits causes those wait operations to be cancelled. To ensure that the action associated with the timer is performed only once, use something like this: used:
void on_some_event() { if (my_timer.expires_from_now(seconds(5)) > 0) { // We managed to cancel the timer. Start new asynchronous wait. my_timer.async_wait(on_timeout); } else { // Too late, timer has already expired! } } void on_timeout(const asio::error_code& e) { if (e != asio::error::operation_aborted) { // Timer was not cancelled, take necessary action. } }
asio::basic_deadline_timer::expires_from_now()
function cancels any pending asynchronous waits, and returns the number
of asynchronous waits that were cancelled. If it returns 0 then you were
too late and the wait handler has already been executed, or will soon
be executed. If it returns 1 then the wait handler was successfully cancelled.
error_code
passed to it contains
the value asio::error::operation_aborted
.
Header: asio/basic_deadline_timer.hpp
Convenience header: asio.hpp