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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:WaitTraits Wait traits requirements]
- The `basic_waitable_timer` template uses wait traits to allow programs to
- customize `wait` and `async_wait` behavior.
- [inline_note Possible uses of wait traits include:\n
- [mdash] To enable timers based on non-realtime clocks.\n
- [mdash] Determining how quickly wallclock-based timers respond to system time
- changes.\n
- [mdash] Correcting for errors or rounding timeouts to boundaries.\n
- [mdash] Preventing duration overflow. That is, a program may set a timer's
- expiry `e` to be `Clock::max()` (meaning never reached) or `Clock::min()`
- (meaning always in the past). As a result, computing the duration until timer
- expiry as `e - Clock::now()` may cause overflow.]
- For a type `Clock` meeting the `Clock` requirements (C++Std
- [time.clock.req]), a type `X` meets the `WaitTraits` requirements if it
- satisfies the requirements listed below.
- In the table below, `t` denotes a (possibly const) value of type
- `Clock::time_point`; and `d` denotes a (possibly const) value of type
- `Clock::duration`.
- [table WaitTraits requirements
- [[expression] [return type] [assertion/note\npre/post-condition]]
- [
- [`X::to_wait_duration(d)`]
- [`Clock::duration`]
- [
- Returns a `Clock::duration` value to be used in a `wait` or `async_wait`
- operation. [inline_note The return value is typically representative of
- the duration `d`.]
- ]
- ]
- [
- [`X::to_wait_duration(t)`]
- [`Clock::duration`]
- [
- Returns a `Clock::duration` value to be used in a `wait` or `async_wait`
- operation. [inline_note The return value is typically representative of
- the duration from `Clock::now()` until the time point `t`.]
- ]
- ]
- ]
- [endsect]
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