llvm/llvm/include/llvm/Support/Chrono.h

//===- 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 LLVM_SUPPORT_CHRONO_H
#define LLVM_SUPPORT_CHRONO_H

#include "llvm/Support/Compiler.h"
#include "llvm/Support/FormatProviders.h"

#include <chrono>
#include <ctime>
#include <ratio>

namespace llvm {

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.
TimePoint;

// 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 { … };

UtcTime;

/// Convert a std::time_t to a UtcTime
inline UtcTime<std::chrono::seconds> toUtcTime(std::time_t T) { … }

/// Convert a TimePoint to std::time_t
inline std::time_t toTimeT(TimePoint<> TP) { … }

/// Convert a UtcTime to std::time_t
inline std::time_t toTimeT(UtcTime<> TP) { … }

/// Convert a std::time_t to a TimePoint
inline TimePoint<std::chrono::seconds>
toTimePoint(std::time_t T) { … }

/// Convert a std::time_t + nanoseconds to a TimePoint
inline TimePoint<>
toTimePoint(std::time_t T, uint32_t nsec) { … }

} // namespace sys

raw_ostream &operator<<(raw_ostream &OS, sys::TimePoint<> TP);
raw_ostream &operator<<(raw_ostream &OS, sys::UtcTime<> TP);

/// Format provider for TimePoint<>
///
/// The options string is a strftime format string, with extensions:
///   - %L is millis: 000-999
///   - %f is micros: 000000-999999
///   - %N is nanos: 000000000 - 999999999
///
/// If no options are given, the default format is "%Y-%m-%d %H:%M:%S.%N".
template <>
struct format_provider<sys::TimePoint<>> { … };

template <> struct format_provider<sys::UtcTime<std::chrono::seconds>> { … };

namespace detail {
template <typename Period> struct unit { … };
template <typename Period> const char unit<Period>::value[] = …;

template <> struct unit<std::ratio<3600>> { … };
template <> struct unit<std::ratio<60>> { … };
template <> struct unit<std::ratio<1>> { … };
template <> struct unit<std::milli> { … };
template <> struct unit<std::micro> { … };
template <> struct unit<std::nano> { … };
} // namespace detail

/// Implementation of format_provider<T> for duration types.
///
/// The options string of a duration type has the grammar:
///
///   duration_options  ::= [unit][show_unit [number_options]]
///   unit              ::= `h`|`m`|`s`|`ms|`us`|`ns`
///   show_unit         ::= `+` | `-`
///   number_options    ::= options string for a integral or floating point type
///
///   Examples
///   =================================
///   |  options  | Input | Output    |
///   =================================
///   | ""        | 1s    | 1 s       |
///   | "ms"      | 1s    | 1000 ms   |
///   | "ms-"     | 1s    | 1000      |
///   | "ms-n"    | 1s    | 1,000     |
///   | ""        | 1.0s  | 1.00 s    |
///   =================================
///
///  If the unit of the duration type is not one of the units specified above,
///  it is still possible to format it, provided you explicitly request a
///  display unit or you request that the unit is not displayed.

format_provider<std::chrono::duration<Rep, Period>>;

} // namespace llvm

#endif // LLVM_SUPPORT_CHRONO_H