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- [/
- / Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
- /
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- /]
- [section:timers Timers]
- Long running I/O operations will often have a deadline by which they must have
- completed. These deadlines may be expressed as absolute times, but are often
- calculated relative to the current time.
- As a simple example, to perform a synchronous wait operation on a timer using a
- relative time one may write:
- io_context i;
- ...
- deadline_timer t(i);
- t.expires_from_now(boost::posix_time::seconds(5));
- t.wait();
- More commonly, a program will perform an asynchronous wait operation on a
- timer:
- void handler(boost::system::error_code ec) { ... }
- ...
- io_context i;
- ...
- deadline_timer t(i);
- t.expires_from_now(boost::posix_time::milliseconds(400));
- t.async_wait(handler);
- ...
- i.run();
- The deadline associated with a timer may also be obtained as a relative time:
- boost::posix_time::time_duration time_until_expiry
- = t.expires_from_now();
- or as an absolute time to allow composition of timers:
- deadline_timer t2(i);
- t2.expires_at(t.expires_at() + boost::posix_time::seconds(30));
- [heading See Also]
- [link boost_asio.reference.basic_deadline_timer basic_deadline_timer],
- [link boost_asio.reference.deadline_timer deadline_timer],
- [link boost_asio.tutorial.tuttimer1 timer tutorials].
- [endsect]
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