Chrono.h

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//===- llvm/Support/Chrono.h - Utilities for Timing Manipulation-*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef WPIUTIL_WPI_CHRONO_H
#define WPIUTIL_WPI_CHRONO_H
 
#include "wpi/Compiler.h"
 
#include <chrono>
#include <ctime>
#include <ratio>
 
namespace wpi {
 
class raw_ostream;
 
namespace sys {
 
/// A time point on the system clock. This is provided for two reasons:
/// - to insulate us against subtle differences in behavior to differences in
///   system clock precision (which is implementation-defined and differs
///   between platforms).
/// - to shorten the type name
/// The default precision is nanoseconds. If you need a specific precision
/// specify it explicitly. If unsure, use the default. If you need a time point
/// on a clock other than the system_clock, use std::chrono directly.
template <typename D = std::chrono::nanoseconds>
using TimePoint = std::chrono::time_point<std::chrono::system_clock, D>;
 
// utc_clock and utc_time are only available since C++20. Add enough code to
// support formatting date/time in UTC.
class UtcClock : public std::chrono::system_clock {};
 
template <typename D = std::chrono::nanoseconds>
using UtcTime = std::chrono::time_point<UtcClock, D>;
 
/// Convert a std::time_t to a UtcTime
inline UtcTime<std::chrono::seconds> toUtcTime(std::time_t T) {
  using namespace std::chrono;
  return UtcTime<seconds>(seconds(T));
}
 
/// Convert a TimePoint to std::time_t
inline std::time_t toTimeT(TimePoint<> TP) {
  using namespace std::chrono;
  return system_clock::to_time_t(
      time_point_cast<system_clock::time_point::duration>(TP));
}
 
/// Convert a UtcTime to std::time_t
inline std::time_t toTimeT(UtcTime<> TP) {
  using namespace std::chrono;
  return system_clock::to_time_t(time_point<system_clock, seconds>(
      duration_cast<seconds>(TP.time_since_epoch())));
}
 
/// Convert a std::time_t to a TimePoint
inline TimePoint<std::chrono::seconds>
toTimePoint(std::time_t T) {
  using namespace std::chrono;
  return time_point_cast<seconds>(system_clock::from_time_t(T));
}
 
/// Convert a std::time_t + nanoseconds to a TimePoint
inline TimePoint<>
toTimePoint(std::time_t T, uint32_t nsec) {
  using namespace std::chrono;
  return time_point_cast<nanoseconds>(system_clock::from_time_t(T))
    + nanoseconds(nsec);
}
 
} // namespace sys
 
raw_ostream &operator<<(raw_ostream &OS, sys::TimePoint<> TP);
raw_ostream &operator<<(raw_ostream &OS, sys::UtcTime<> TP);
 
} // namespace wpi
 
#endif // WPIUTIL_WPI_CHRONO_H