Mercurial > repos > rliterman > csp2

comparison CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/include/kj/timer.h @ 69:33d812a61356

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author jpayne
date Tue, 18 Mar 2025 17:55:14 -0400
parents
children
comparison
equal deleted inserted replaced
67:0e9998148a16 69:33d812a61356
1 // Copyright (c) 2014 Google Inc. (contributed by Remy Blank <rblank@google.com>)
2 // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
3 // Licensed under the MIT License:
4 //
5 // Permission is hereby granted, free of charge, to any person obtaining a copy
6 // of this software and associated documentation files (the "Software"), to deal
7 // in the Software without restriction, including without limitation the rights
8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 // copies of the Software, and to permit persons to whom the Software is
10 // furnished to do so, subject to the following conditions:
11 //
12 // The above copyright notice and this permission notice shall be included in
13 // all copies or substantial portions of the Software.
14 //
15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 // THE SOFTWARE.
22
23 #pragma once
24
25 #include <kj/time.h>
26 #include "async.h"
27
28 KJ_BEGIN_HEADER
29
30 namespace kj {
31
32 class Timer: public MonotonicClock {
33 // Interface to time and timer functionality.
34 //
35 // Each `Timer` may have a different origin, and some `Timer`s may in fact tick at a different
36 // rate than real time (e.g. a `Timer` could represent CPU time consumed by a thread). However,
37 // all `Timer`s are monotonic: time will never appear to move backwards, even if the calendar
38 // date as tracked by the system is manually modified.
39 //
40 // That said, the `Timer` returned by `kj::setupAsyncIo().provider->getTimer()` in particular is
41 // guaranteed to be synchronized with the `MonotonicClock` returned by
42 // `systemPreciseMonotonicClock()` (or, more precisely, is updated to match that clock whenever
43 // the loop waits).
44 //
45 // Note that the value returned by `Timer::now()` only changes each time the
46 // event loop waits for I/O from the system. While the event loop is actively
47 // running, the time stays constant. This is intended to make behavior more
48 // deterministic and reproducible. However, if you need up-to-the-cycle
49 // accurate time, then `Timer::now()` is not appropriate. Instead, use
50 // `systemPreciseMonotonicClock()` directly in this case.
51
52 public:
53 virtual TimePoint now() const = 0;
54 // Returns the current value of a clock that moves steadily forward, independent of any
55 // changes in the wall clock. The value is updated every time the event loop waits,
56 // and is constant in-between waits.
57
58 virtual Promise<void> atTime(TimePoint time) = 0;
59 // Returns a promise that returns as soon as now() >= time.
60
61 virtual Promise<void> afterDelay(Duration delay) = 0;
62 // Equivalent to atTime(now() + delay).
63
64 template <typename T>
65 Promise<T> timeoutAt(TimePoint time, Promise<T>&& promise) KJ_WARN_UNUSED_RESULT;
66 // Return a promise equivalent to `promise` but which throws an exception (and cancels the
67 // original promise) if it hasn't completed by `time`. The thrown exception is of type
68 // "OVERLOADED".
69
70 template <typename T>
71 Promise<T> timeoutAfter(Duration delay, Promise<T>&& promise) KJ_WARN_UNUSED_RESULT;
72 // Return a promise equivalent to `promise` but which throws an exception (and cancels the
73 // original promise) if it hasn't completed after `delay` from now. The thrown exception is of
74 // type "OVERLOADED".
75
76 private:
77 static kj::Exception makeTimeoutException();
78 };
79
80 class TimerImpl final: public Timer {
81 // Implementation of Timer that expects an external caller -- usually, the EventPort
82 // implementation -- to tell it when time has advanced.
83
84 public:
85 TimerImpl(TimePoint startTime);
86 ~TimerImpl() noexcept(false);
87
88 Maybe<TimePoint> nextEvent();
89 // Returns the time at which the next scheduled timer event will occur, or null if no timer
90 // events are scheduled.
91
92 Maybe<uint64_t> timeoutToNextEvent(TimePoint start, Duration unit, uint64_t max);
93 // Convenience method which computes a timeout value to pass to an event-waiting system call to
94 // cause it to time out when the next timer event occurs.
95 //
96 // `start` is the time at which the timeout starts counting. This is typically not the same as
97 // now() since some time may have passed since the last time advanceTo() was called.
98 //
99 // `unit` is the time unit in which the timeout is measured. This is often MILLISECONDS. Note
100 // that this method will fractional values *up*, to guarantee that the returned timeout waits
101 // until just *after* the time the event is scheduled.
102 //
103 // The timeout will be clamped to `max`. Use this to avoid an overflow if e.g. the OS wants a
104 // 32-bit value or a signed value.
105 //
106 // Returns nullptr if there are no future events.
107
108 void advanceTo(TimePoint newTime);
109 // Set the time to `time` and fire any at() events that have been passed.
110
111 // implements Timer ----------------------------------------------------------
112 TimePoint now() const override;
113 Promise<void> atTime(TimePoint time) override;
114 Promise<void> afterDelay(Duration delay) override;
115
116 private:
117 struct Impl;
118 class TimerPromiseAdapter;
119 TimePoint time;
120 Own<Impl> impl;
121 };
122
123 // =======================================================================================
124 // inline implementation details
125
126 template <typename T>
127 Promise<T> Timer::timeoutAt(TimePoint time, Promise<T>&& promise) {
128 return promise.exclusiveJoin(atTime(time).then([]() -> kj::Promise<T> {
129 return makeTimeoutException();
130 }));
131 }
132
133 template <typename T>
134 Promise<T> Timer::timeoutAfter(Duration delay, Promise<T>&& promise) {
135 return promise.exclusiveJoin(afterDelay(delay).then([]() -> kj::Promise<T> {
136 return makeTimeoutException();
137 }));
138 }
139
140 inline TimePoint TimerImpl::now() const { return time; }
141
142 } // namespace kj
143
144 KJ_END_HEADER