53 lines
1.9 KiB
Plaintext
53 lines
1.9 KiB
Plaintext
[/
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/ Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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/
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/ Distributed under the Boost Software License, Version 1.0. (See accompanying
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/ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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/]
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[section:WaitTraits Wait traits requirements]
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The `basic_waitable_timer` template uses wait traits to allow programs to
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customize `wait` and `async_wait` behavior.
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[inline_note Possible uses of wait traits include:\n
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[mdash] To enable timers based on non-realtime clocks.\n
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[mdash] Determining how quickly wallclock-based timers respond to system time
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changes.\n
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[mdash] Correcting for errors or rounding timeouts to boundaries.\n
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[mdash] Preventing duration overflow. That is, a program may set a timer's
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expiry `e` to be `Clock::max()` (meaning never reached) or `Clock::min()`
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(meaning always in the past). As a result, computing the duration until timer
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expiry as `e - Clock::now()` may cause overflow.]
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For a type `Clock` meeting the `Clock` requirements (C++Std
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[time.clock.req]), a type `X` meets the `WaitTraits` requirements if it
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satisfies the requirements listed below.
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In the table below, `t` denotes a (possibly const) value of type
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`Clock::time_point`; and `d` denotes a (possibly const) value of type
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`Clock::duration`.
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[table WaitTraits requirements
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[[expression] [return type] [assertion/note\npre/post-condition]]
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[
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[`X::to_wait_duration(d)`]
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[`Clock::duration`]
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[
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Returns a `Clock::duration` value to be used in a `wait` or `async_wait`
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operation. [inline_note The return value is typically representative of
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the duration `d`.]
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]
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]
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[
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[`X::to_wait_duration(t)`]
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[`Clock::duration`]
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[
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Returns a `Clock::duration` value to be used in a `wait` or `async_wait`
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operation. [inline_note The return value is typically representative of
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the duration from `Clock::now()` until the time point `t`.]
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]
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]
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]
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[endsect]
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