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# asio::basic_deadline_timer< Time, TimeTraits, TimerService > Class Template Reference

Inherits asio::basic_io_object< TimerService >.

Inheritance diagram for asio::basic_deadline_timer< Time, TimeTraits, TimerService >:

List of all members.

## Detailed Description

### template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>
class asio::basic_deadline_timer< Time, TimeTraits, TimerService >

Provides waitable timer functionality.

The basic_deadline_timer class template provides the ability to perform a blocking or asynchronous wait for a timer to expire.

Most applications will use the asio::deadline_timer typedef.

Thread Safety
  Distinct objects: Safe.
  Shared objects: Unsafe.

Examples
  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 an active deadline_timer's expiry time

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.
       }
     }

- The 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.

- If a wait handler is cancelled, the asio::error_code passed to it contains the value asio::error::operation_aborted.

## Public Types

typedef TimeTraits | traits_type
| The time traits type.
typedef traits_type::time_type | time_type
| The time type.
typedef traits_type::duration_type | duration_type
| The duration type.
typedef TimerService | service_type
| The type of the service that will be used to provide I/O operations.
typedef service_type::implementation_type | implementation_type
| The underlying implementation type of I/O object.

## Public Member Functions

| basic_deadline_timer (asio::io_service &io_service)
| Constructor.
| basic_deadline_timer (asio::io_service &io_service, const time_type &expiry_time)
| Constructor to set a particular expiry time as an absolute time.
| basic_deadline_timer (asio::io_service &io_service, const duration_type &expiry_time)
| Constructor to set a particular expiry time relative to now.
std::size_t | cancel ()
| Cancel any asynchronous operations that are waiting on the timer.
std::size_t | cancel (asio::error_code &ec)
| Cancel any asynchronous operations that are waiting on the timer.
time_type | expires_at () const
| Get the timer's expiry time as an absolute time.
std::size_t | expires_at (const time_type &expiry_time)
| Set the timer's expiry time as an absolute time.
std::size_t | expires_at (const time_type &expiry_time, asio::error_code &ec)
| Set the timer's expiry time as an absolute time.
duration_type | expires_from_now () const
| Get the timer's expiry time relative to now.
std::size_t | expires_from_now (const duration_type &expiry_time)
| Set the timer's expiry time relative to now.
std::size_t | expires_from_now (const duration_type &expiry_time, asio::error_code &ec)
| Set the timer's expiry time relative to now.
void | wait ()
| Perform a blocking wait on the timer.
void | wait (asio::error_code &ec)
| Perform a blocking wait on the timer.
template<typename WaitHandler>
void | async_wait (WaitHandler handler)
| Start an asynchronous wait on the timer.
asio::io_service & | io_service ()
| Get the io_service associated with the object.

## Member Typedef Documentation

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

typedef TimeTraits asio::basic_deadline_timer< Time, TimeTraits, TimerService >::traits_type

The time traits type.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

typedef traits_type::time_type asio::basic_deadline_timer< Time, TimeTraits, TimerService >::time_type

The time type.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

typedef traits_type::duration_type asio::basic_deadline_timer< Time, TimeTraits, TimerService >::duration_type

The duration type.

typedef TimerService asio::basic_io_object< TimerService >::service_type`[inherited]`

The type of the service that will be used to provide I/O operations.

typedef service_type::implementation_type asio::basic_io_object< TimerService >::implementation_type`[inherited]`

The underlying implementation type of I/O object.

## Constructor & Destructor Documentation

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

asio::basic_deadline_timer< Time, TimeTraits, TimerService >::basic_deadline_timer | ( | asio::io_service & | io_service | ) | `[explicit]`

Constructor.

This constructor creates a timer without setting an expiry time. The expires_at() or expires_from_now() functions must be called to set an expiry time before the timer can be waited on.

Parameters:

  | io_service | The io_service object that the timer will use to dispatch handlers for any asynchronous operations performed on the timer.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

asio::basic_deadline_timer< Time, TimeTraits, TimerService >::basic_deadline_timer | ( | asio::io_service & | io_service,
|  | const time_type & | expiry_time |
| ) |  |  |

Constructor to set a particular expiry time as an absolute time.

This constructor creates a timer and sets the expiry time.

Parameters:

  | io_service | The io_service object that the timer will use to dispatch handlers for any asynchronous operations performed on the timer.
  | expiry_time | The expiry time to be used for the timer, expressed as an absolute time.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

asio::basic_deadline_timer< Time, TimeTraits, TimerService >::basic_deadline_timer | ( | asio::io_service & | io_service,
|  | const duration_type & | expiry_time |
| ) |  |  |

Constructor to set a particular expiry time relative to now.

This constructor creates a timer and sets the expiry time.

Parameters:

  | io_service | The io_service object that the timer will use to dispatch handlers for any asynchronous operations performed on the timer.
  | expiry_time | The expiry time to be used for the timer, relative to now.

## Member Function Documentation

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::cancel | ( |  | ) |

Cancel any asynchronous operations that are waiting on the timer.

This function forces the completion of any pending asynchronous wait operations against the timer. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Cancelling the timer does not change the expiry time.

Returns:
  The number of asynchronous operations that were cancelled.

Exceptions:

  | asio::system_error | Thrown on failure.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::cancel | ( | asio::error_code & | ec | ) |

Cancel any asynchronous operations that are waiting on the timer.

This function forces the completion of any pending asynchronous wait operations against the timer. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Cancelling the timer does not change the expiry time.

Parameters:

  | ec | Set to indicate what error occurred, if any.

Returns:
  The number of asynchronous operations that were cancelled.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

time_type asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_at | ( |  | ) | const

Get the timer's expiry time as an absolute time.

This function may be used to obtain the timer's current expiry time. Whether the timer has expired or not does not affect this value.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_at | ( | const time_type & | expiry_time | ) |

Set the timer's expiry time as an absolute time.

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Parameters:

  | expiry_time | The expiry time to be used for the timer.

Returns:
  The number of asynchronous operations that were cancelled.

Exceptions:

  | asio::system_error | Thrown on failure.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_at | ( | const time_type & | expiry_time,
|  | asio::error_code & | ec |
| ) |  |  |

Set the timer's expiry time as an absolute time.

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Parameters:

  | expiry_time | The expiry time to be used for the timer.
  | ec | Set to indicate what error occurred, if any.

Returns:
  The number of asynchronous operations that were cancelled.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

duration_type asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_from_now | ( |  | ) | const

Get the timer's expiry time relative to now.

This function may be used to obtain the timer's current expiry time. Whether the timer has expired or not does not affect this value.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_from_now | ( | const duration_type & | expiry_time | ) |

Set the timer's expiry time relative to now.

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Parameters:

  | expiry_time | The expiry time to be used for the timer.

Returns:
  The number of asynchronous operations that were cancelled.

Exceptions:

  | asio::system_error | Thrown on failure.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

std::size_t asio::basic_deadline_timer< Time, TimeTraits, TimerService >::expires_from_now | ( | const duration_type & | expiry_time,
|  | asio::error_code & | ec |
| ) |  |  |

Set the timer's expiry time relative to now.

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Parameters:

  | expiry_time | The expiry time to be used for the timer.
  | ec | Set to indicate what error occurred, if any.

Returns:
  The number of asynchronous operations that were cancelled.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

void asio::basic_deadline_timer< Time, TimeTraits, TimerService >::wait | ( |  | ) |

Perform a blocking wait on the timer.

This function is used to wait for the timer to expire. This function blocks and does not return until the timer has expired.

Exceptions:

  | asio::system_error | Thrown on failure.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>

void asio::basic_deadline_timer< Time, TimeTraits, TimerService >::wait | ( | asio::error_code & | ec | ) |

Perform a blocking wait on the timer.

This function is used to wait for the timer to expire. This function blocks and does not return until the timer has expired.

Parameters:

  | ec | Set to indicate what error occurred, if any.

template<typename Time, typename TimeTraits = asio::time_traits<Time>, typename TimerService = deadline_timer_service<Time, TimeTraits>>
template<typename WaitHandler>

void asio::basic_deadline_timer< Time, TimeTraits, TimerService >::async_wait | ( | WaitHandler | handler | ) |

Start an asynchronous wait on the timer.

This function may be used to initiate an asynchronous wait against the timer. It always returns immediately.

For each call to async_wait(), the supplied handler will be called exactly once. The handler will be called when:

- The timer has expired.

- The timer was cancelled, in which case the handler is passed the error code asio::error::operation_aborted.

Parameters:

  | handler | The handler to be called when the timer expires. Copies will be made of the handler as required. The function signature of the handler must be:
       void handler(
         const asio::error_code& error // Result of operation.
       );
  Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using asio::io_service::post().

asio::io_service& asio::basic_io_object< TimerService >::io_service | ( |  | ) | `[inherited]`

Get the io_service associated with the object.

This function may be used to obtain the io_service object that the I/O object uses to dispatch handlers for asynchronous operations.

Returns:
  A reference to the io_service object that the I/O object will use to dispatch handlers. Ownership is not transferred to the caller.

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