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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef PLATFORM_BASE_TRIVIAL_CLOCK_TRAITS_H_
#define PLATFORM_BASE_TRIVIAL_CLOCK_TRAITS_H_
#include <chrono>
#include <ostream>
namespace openscreen {
// The Open Screen monotonic clock traits description, providing all the C++14
// requirements of a TrivialClock, for use with STL <chrono>.
class TrivialClockTraits {
public:
// TrivialClock named requirements: std::chrono templates can/may use these.
// NOTE: unless you are specifically integrating with the clock, you probably
// don't want to use these types, and instead should reference the std::chrono
// types directly.
using duration = std::chrono::microseconds;
using rep = duration::rep;
using period = duration::period;
using time_point = std::chrono::time_point<TrivialClockTraits, duration>;
static constexpr bool is_steady = true;
// Helper method for named requirements.
template <typename D>
static constexpr duration to_duration(D d) {
return std::chrono::duration_cast<duration>(d);
}
// Time point values from the clock use microsecond precision, as a reasonably
// high-resolution clock is required. The time source must tick forward at
// least 10000 times per second.
using kRequiredResolution = std::ratio<1, 10000>;
// In <chrono>, a clock type is just some type properties plus a static now()
// function. So, there's nothing to instantiate here.
TrivialClockTraits() = delete;
~TrivialClockTraits() = delete;
// "Trivially copyable" is necessary for using the time types in
// std::atomic<>.
static_assert(std::is_trivially_copyable<duration>(),
"duration is not trivially copyable");
static_assert(std::is_trivially_copyable<time_point>(),
"time_point is not trivially copyable");
};
// Convenience type definition, for injecting time sources into classes (e.g.,
// &Clock::now versus something else for testing).
using ClockNowFunctionPtr = TrivialClockTraits::time_point (*)();
// Logging convenience for durations. Outputs a string of the form "123µs".
std::ostream& operator<<(std::ostream& os,
const TrivialClockTraits::duration& d);
// Logging convenience for time points. Outputs a string of the form
// "123µs-ticks".
std::ostream& operator<<(std::ostream& os,
const TrivialClockTraits::time_point& tp);
// Logging (and gtest pretty-printing) for several commonly-used chrono types.
std::ostream& operator<<(std::ostream& out, const std::chrono::hours&);
std::ostream& operator<<(std::ostream& out, const std::chrono::minutes&);
std::ostream& operator<<(std::ostream& out, const std::chrono::seconds&);
std::ostream& operator<<(std::ostream& out, const std::chrono::milliseconds&);
// Note: The ostream output operator for std::chrono::microseconds is handled by
// the one for TrivialClockTraits::duration above since they are the same type.
} // namespace openscreen
#endif // PLATFORM_BASE_TRIVIAL_CLOCK_TRAITS_H_
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