// Copyright 2017 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

// -----------------------------------------------------------------------------

// File: time.h

// -----------------------------------------------------------------------------

//

// This header file defines abstractions for computing with absolute points

// in time, durations of time, and formatting and parsing time within a given

// time zone. The following abstractions are defined:

//

//  * `absl::Time` defines an absolute, specific instance in time

//  * `absl::Duration` defines a signed, fixed-length span of time

//  * `absl::TimeZone` defines geopolitical time zone regions (as collected

//     within the IANA Time Zone database (https://www.iana.org/time-zones)).

//

// Note: Absolute times are distinct from civil times, which refer to the

// human-scale time commonly represented by `YYYY-MM-DD hh:mm:ss`. The mapping

// between absolute and civil times can be specified by use of time zones

// (`absl::TimeZone` within this API). That is:

//

//   Civil Time = F(Absolute Time, Time Zone)

//   Absolute Time = G(Civil Time, Time Zone)

//

// See civil_time.h for abstractions related to constructing and manipulating

// civil time.

//

// Example:

//

//   absl::TimeZone nyc;

//   // LoadTimeZone() may fail so it's always better to check for success.

//   if (!absl::LoadTimeZone("America/New_York", &nyc)) {

//      // handle error case

//   }

//

//   // My flight leaves NYC on Jan 2, 2017 at 03:04:05

//   absl::CivilSecond cs(2017, 1, 2, 3, 4, 5);

//   absl::Time takeoff = absl::FromCivil(cs, nyc);

//

//   absl::Duration flight_duration = absl::Hours(21) + absl::Minutes(35);

//   absl::Time landing = takeoff + flight_duration;

//

//   absl::TimeZone syd;

//   if (!absl::LoadTimeZone("Australia/Sydney", &syd)) {

//      // handle error case

//   }

//   std::string s = absl::FormatTime(

//       "My flight will land in Sydney on %Y-%m-%d at %H:%M:%S",

//       landing, syd);

#ifndef ABSL_TIME_TIME_H_

#define ABSL_TIME_TIME_H_

#if !defined(_MSC_VER)

#include <sys/time.h>

#else

// We don't include `winsock2.h` because it drags in `windows.h` and friends,

// and they define conflicting macros like OPAQUE, ERROR, and more. This has the

// potential to break Abseil users.

//

// Instead we only forward declare `timeval` and require Windows users include

// `winsock2.h` themselves. This is both inconsistent and troublesome, but so is

// including 'windows.h' so we are picking the lesser of two evils here.

struct timeval;

#endif

#include <chrono>  // NOLINT(build/c++11)

#include <cmath>

#include <cstdint>

#include <ctime>

#include <limits>

#include <ostream>

#include <string>

#include <type_traits>

#include <utility>

#include "absl/base/config.h"

#include "absl/base/macros.h"

#include "absl/strings/string_view.h"

#include "absl/time/civil_time.h"

#include "absl/time/internal/cctz/include/cctz/time_zone.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

class Duration;  // Defined below

class Time;      // Defined below

class TimeZone;  // Defined below

namespace time_internal {

int64_t IDivDuration(bool satq, Duration num, Duration den, Duration* rem);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixDuration(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration ToUnixDuration(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr int64_t GetRepHi(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr uint32_t GetRepLo(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration MakeDuration(int64_t hi,

                                                              uint32_t lo);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration MakeDuration(int64_t hi,

                                                              int64_t lo);

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration MakePosDoubleDuration(double n);

constexpr int64_t kTicksPerNanosecond = 4;

constexpr int64_t kTicksPerSecond = 1000 * 1000 * 1000 * kTicksPerNanosecond;

template <std::intmax_t N>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration FromInt64(int64_t v,

                                                           std::ratio<1, N>);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration FromInt64(int64_t v,

                                                           std::ratio<60>);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration FromInt64(int64_t v,

                                                           std::ratio<3600>);

template <typename T>

using EnableIfIntegral = typename std::enable_if<

    std::is_integral<T>::value || std::is_enum<T>::value, int>::type;

template <typename T>

using EnableIfFloat =

    typename std::enable_if<std::is_floating_point<T>::value, int>::type;

}  // namespace time_internal

// Duration

//

// The `absl::Duration` class represents a signed, fixed-length amount of time.

// A `Duration` is generated using a unit-specific factory function, or is

// the result of subtracting one `absl::Time` from another. Durations behave

// like unit-safe integers and they support all the natural integer-like

// arithmetic operations. Arithmetic overflows and saturates at +/- infinity.

// `Duration` should be passed by value rather than const reference.

//

// Factory functions `Nanoseconds()`, `Microseconds()`, `Milliseconds()`,

// `Seconds()`, `Minutes()`, `Hours()` and `InfiniteDuration()` allow for

// creation of constexpr `Duration` values

//

// Examples:

//

//   constexpr absl::Duration ten_ns = absl::Nanoseconds(10);

//   constexpr absl::Duration min = absl::Minutes(1);

//   constexpr absl::Duration hour = absl::Hours(1);

//   absl::Duration dur = 60 * min;  // dur == hour

//   absl::Duration half_sec = absl::Milliseconds(500);

//   absl::Duration quarter_sec = 0.25 * absl::Seconds(1);

//

// `Duration` values can be easily converted to an integral number of units

// using the division operator.

//

// Example:

//

//   constexpr absl::Duration dur = absl::Milliseconds(1500);

//   int64_t ns = dur / absl::Nanoseconds(1);   // ns == 1500000000

//   int64_t ms = dur / absl::Milliseconds(1);  // ms == 1500

//   int64_t sec = dur / absl::Seconds(1);    // sec == 1 (subseconds truncated)

//   int64_t min = dur / absl::Minutes(1);    // min == 0

//

// See the `IDivDuration()` and `FDivDuration()` functions below for details on

// how to access the fractional parts of the quotient.

//

// Alternatively, conversions can be performed using helpers such as

// `ToInt64Microseconds()` and `ToDoubleSeconds()`.

class Duration {

 public:

  // Value semantics.

  constexpr Duration() : rep_hi_(0), rep_lo_(0) {}  // zero-length duration

  // Copyable.

#if !defined(__clang__) && defined(_MSC_VER) && _MSC_VER < 1930

  // Explicitly defining the constexpr copy constructor avoids an MSVC bug.

  constexpr Duration(const Duration& d)

      : rep_hi_(d.rep_hi_), rep_lo_(d.rep_lo_) {}

#else

  constexpr Duration(const Duration& d) = default;

#endif

  Duration& operator=(const Duration& d) = default;

  // Compound assignment operators.

  Duration& operator+=(Duration d);

  Duration& operator-=(Duration d);

  Duration& operator*=(int64_t r);

  Duration& operator*=(double r);

  Duration& operator/=(int64_t r);

  Duration& operator/=(double r);

  Duration& operator%=(Duration rhs);

  // Overloads that forward to either the int64_t or double overloads above.

  // Integer operands must be representable as int64_t. Integer division is

  // truncating, so values less than the resolution will be returned as zero.

  // Floating-point multiplication and division is rounding (halfway cases

  // rounding away from zero), so values less than the resolution may be

  // returned as either the resolution or zero.  In particular, `d / 2.0`

  // can produce `d` when it is the resolution and "even".

  template <typename T, time_internal::EnableIfIntegral<T> = 0>

  Duration& operator*=(T r) {

    int64_t x = r;

    return *this *= x;

  }

  template <typename T, time_internal::EnableIfIntegral<T> = 0>

  Duration& operator/=(T r) {

    int64_t x = r;

    return *this /= x;

  }

  template <typename T, time_internal::EnableIfFloat<T> = 0>

  Duration& operator*=(T r) {

    double x = r;

    return *this *= x;

  }

  template <typename T, time_internal::EnableIfFloat<T> = 0>

  Duration& operator/=(T r) {

    double x = r;

    return *this /= x;

  }

  template <typename H>

  friend H AbslHashValue(H h, Duration d) {

    return H::combine(std::move(h), d.rep_hi_.Get(), d.rep_lo_);

  }

 private:

  friend constexpr int64_t time_internal::GetRepHi(Duration d);

  friend constexpr uint32_t time_internal::GetRepLo(Duration d);

  friend constexpr Duration time_internal::MakeDuration(int64_t hi,

                                                        uint32_t lo);

  constexpr Duration(int64_t hi, uint32_t lo) : rep_hi_(hi), rep_lo_(lo) {}

  // We store `rep_hi_` 4-byte rather than 8-byte aligned to avoid 4 bytes of

  // tail padding.

  class HiRep {

   public:

    // Default constructor default-initializes `hi_`, which has the same

    // semantics as default-initializing an `int64_t` (undetermined value).

    HiRep() = default;

    HiRep(const HiRep&) = default;

    HiRep& operator=(const HiRep&) = default;

    explicit constexpr HiRep(const int64_t value)

        :  // C++17 forbids default-initialization in constexpr contexts. We can

           // remove this in C++20.

#if defined(ABSL_IS_BIG_ENDIAN) && ABSL_IS_BIG_ENDIAN

          hi_(0),

          lo_(0)

#else

          lo_(0),

          hi_(0)

#endif

    {

      *this = value;

    }

    constexpr int64_t Get() const {

      const uint64_t unsigned_value =

          (static_cast<uint64_t>(hi_) << 32) | static_cast<uint64_t>(lo_);

      // `static_cast<int64_t>(unsigned_value)` is implementation-defined

      // before c++20. On all supported platforms the behaviour is that mandated

      // by c++20, i.e. "If the destination type is signed, [...] the result is

      // the unique value of the destination type equal to the source value

      // modulo 2^n, where n is the number of bits used to represent the

      // destination type."

      static_assert(

          (static_cast<int64_t>((std::numeric_limits<uint64_t>::max)()) ==

           int64_t{-1}) &&

              (static_cast<int64_t>(static_cast<uint64_t>(

                                        (std::numeric_limits<int64_t>::max)()) +

                                    1) ==

               (std::numeric_limits<int64_t>::min)()),

          "static_cast<int64_t>(uint64_t) does not have c++20 semantics");

      return static_cast<int64_t>(unsigned_value);

    }

    constexpr HiRep& operator=(const int64_t value) {

      // "If the destination type is unsigned, the resulting value is the

      // smallest unsigned value equal to the source value modulo 2^n

      // where `n` is the number of bits used to represent the destination

      // type".

      const auto unsigned_value = static_cast<uint64_t>(value);

      hi_ = static_cast<uint32_t>(unsigned_value >> 32);

      lo_ = static_cast<uint32_t>(unsigned_value);

      return *this;

    }

   private:

    // Notes:

    //  - Ideally we would use a `char[]` and `std::bitcast`, but the latter

    //    does not exist (and is not constexpr in `absl`) before c++20.

    //  - Order is optimized depending on endianness so that the compiler can

    //    turn `Get()` (resp. `operator=()`) into a single 8-byte load (resp.

    //    store).

#if defined(ABSL_IS_BIG_ENDIAN) && ABSL_IS_BIG_ENDIAN

    uint32_t hi_;

    uint32_t lo_;

#else

    uint32_t lo_;

    uint32_t hi_;

#endif

  };

  HiRep rep_hi_;

  uint32_t rep_lo_;

};

// Relational Operators

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator<(Duration lhs,

                                                       Duration rhs);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator>(Duration lhs,

                                                       Duration rhs) {

  return rhs < lhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator>=(Duration lhs,

                                                        Duration rhs) {

  return !(lhs < rhs);

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator<=(Duration lhs,

                                                        Duration rhs) {

  return !(rhs < lhs);

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator==(Duration lhs,

                                                        Duration rhs);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator!=(Duration lhs,

                                                        Duration rhs) {

  return !(lhs == rhs);

}

// Additive Operators

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration operator-(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration operator+(Duration lhs,

                                                        Duration rhs) {

  return lhs += rhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration operator-(Duration lhs,

                                                        Duration rhs) {

  return lhs -= rhs;

}

// Multiplicative Operators

// Integer operands must be representable as int64_t.

template <typename T>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration operator*(Duration lhs, T rhs) {

  return lhs *= rhs;

}

template <typename T>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration operator*(T lhs, Duration rhs) {

  return rhs *= lhs;

}

Unexecuted instantiation: absl::Duration absl::operator*<int>(int, absl::Duration)

Unexecuted instantiation: absl::Duration absl::operator*<long>(long, absl::Duration)

Unexecuted instantiation: absl::Duration absl::operator*<double>(double, absl::Duration)

template <typename T>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration operator/(Duration lhs, T rhs) {

  return lhs /= rhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline int64_t operator/(Duration lhs,

                                                       Duration rhs) {

  return time_internal::IDivDuration(true, lhs, rhs,

                                     &lhs);  // trunc towards zero

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration operator%(Duration lhs,

                                                        Duration rhs) {

  return lhs %= rhs;

}

// IDivDuration()

//

// Divides a numerator `Duration` by a denominator `Duration`, returning the

// quotient and remainder. The remainder always has the same sign as the

// numerator. The returned quotient and remainder respect the identity:

//

//   numerator = denominator * quotient + remainder

//

// Returned quotients are capped to the range of `int64_t`, with the difference

// spilling into the remainder to uphold the above identity. This means that the

// remainder returned could differ from the remainder returned by

// `Duration::operator%` for huge quotients.

//

// See also the notes on `InfiniteDuration()` below regarding the behavior of

// division involving zero and infinite durations.

//

// Example:

//

//   constexpr absl::Duration a =

//       absl::Seconds(std::numeric_limits<int64_t>::max());  // big

//   constexpr absl::Duration b = absl::Nanoseconds(1);       // small

//

//   absl::Duration rem = a % b;

//   // rem == absl::ZeroDuration()

//

//   // Here, q would overflow int64_t, so rem accounts for the difference.

//   int64_t q = absl::IDivDuration(a, b, &rem);

//   // q == std::numeric_limits<int64_t>::max(), rem == a - b * q

inline int64_t IDivDuration(Duration num, Duration den, Duration* rem) {

  return time_internal::IDivDuration(true, num, den,

                                     rem);  // trunc towards zero

}

// FDivDuration()

//

// Divides a `Duration` numerator into a fractional number of units of a

// `Duration` denominator.

//

// See also the notes on `InfiniteDuration()` below regarding the behavior of

// division involving zero and infinite durations.

//

// Example:

//

//   double d = absl::FDivDuration(absl::Milliseconds(1500), absl::Seconds(1));

//   // d == 1.5

ABSL_ATTRIBUTE_CONST_FUNCTION double FDivDuration(Duration num, Duration den);

// ZeroDuration()

//

// Returns a zero-length duration. This function behaves just like the default

// constructor, but the name helps make the semantics clear at call sites.

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration ZeroDuration() {

  return Duration();

}

// AbsDuration()

//

// Returns the absolute value of a duration.

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration AbsDuration(Duration d) {

  return (d < ZeroDuration()) ? -d : d;

}

// Trunc()

//

// Truncates a duration (toward zero) to a multiple of a non-zero unit.

//

// Example:

//

//   absl::Duration d = absl::Nanoseconds(123456789);

//   absl::Duration a = absl::Trunc(d, absl::Microseconds(1));  // 123456us

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Trunc(Duration d, Duration unit);

// Floor()

//

// Floors a duration using the passed duration unit to its largest value not

// greater than the duration.

//

// Example:

//

//   absl::Duration d = absl::Nanoseconds(123456789);

//   absl::Duration b = absl::Floor(d, absl::Microseconds(1));  // 123456us

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Floor(Duration d, Duration unit);

// Ceil()

//

// Returns the ceiling of a duration using the passed duration unit to its

// smallest value not less than the duration.

//

// Example:

//

//   absl::Duration d = absl::Nanoseconds(123456789);

//   absl::Duration c = absl::Ceil(d, absl::Microseconds(1));   // 123457us

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Ceil(Duration d, Duration unit);

// InfiniteDuration()

//

// Returns an infinite `Duration`.  To get a `Duration` representing negative

// infinity, use `-InfiniteDuration()`.

//

// Duration arithmetic overflows to +/- infinity and saturates. In general,

// arithmetic with `Duration` infinities is similar to IEEE 754 infinities

// except where IEEE 754 NaN would be involved, in which case +/-

// `InfiniteDuration()` is used in place of a "nan" Duration.

//

// Examples:

//

//   constexpr absl::Duration inf = absl::InfiniteDuration();

//   const absl::Duration d = ... any finite duration ...

//

//   inf == inf + inf

//   inf == inf + d

//   inf == inf - inf

//   -inf == d - inf

//

//   inf == d * 1e100

//   inf == inf / 2

//   0 == d / inf

//   INT64_MAX == inf / d

//

//   d < inf

//   -inf < d

//

//   // Division by zero returns infinity, or INT64_MIN/MAX where appropriate.

//   inf == d / 0

//   INT64_MAX == d / absl::ZeroDuration()

//

// The examples involving the `/` operator above also apply to `IDivDuration()`

// and `FDivDuration()`.

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration InfiniteDuration();

// Nanoseconds()

// Microseconds()

// Milliseconds()

// Seconds()

// Minutes()

// Hours()

//

// Factory functions for constructing `Duration` values from an integral number

// of the unit indicated by the factory function's name. The number must be

// representable as int64_t.

//

// NOTE: no "Days()" factory function exists because "a day" is ambiguous.

// Civil days are not always 24 hours long, and a 24-hour duration often does

// not correspond with a civil day. If a 24-hour duration is needed, use

// `absl::Hours(24)`. If you actually want a civil day, use absl::CivilDay

// from civil_time.h.

//

// Example:

//

//   absl::Duration a = absl::Seconds(60);

//   absl::Duration b = absl::Minutes(1);  // b == a

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Nanoseconds(T n) {

  return time_internal::FromInt64(n, std::nano{});

}

Unexecuted instantiation: absl::Duration absl::Nanoseconds<int, 0>(int)

Unexecuted instantiation: absl::Duration absl::Nanoseconds<long, 0>(long)

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Microseconds(T n) {

  return time_internal::FromInt64(n, std::micro{});

}

Unexecuted instantiation: absl::Duration absl::Microseconds<int, 0>(int)

Unexecuted instantiation: absl::Duration absl::Microseconds<long, 0>(long)

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Milliseconds(T n) {

  return time_internal::FromInt64(n, std::milli{});

}

Unexecuted instantiation: absl::Duration absl::Milliseconds<int, 0>(int)

Unexecuted instantiation: absl::Duration absl::Milliseconds<long, 0>(long)

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Seconds(T n) {

  return time_internal::FromInt64(n, std::ratio<1>{});

}

Unexecuted instantiation: absl::Duration absl::Seconds<long, 0>(long)

Unexecuted instantiation: absl::Duration absl::Seconds<int, 0>(int)

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Minutes(T n) {

  return time_internal::FromInt64(n, std::ratio<60>{});

}

template <typename T, time_internal::EnableIfIntegral<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Duration Hours(T n) {

  return time_internal::FromInt64(n, std::ratio<3600>{});

}

// Factory overloads for constructing `Duration` values from a floating-point

// number of the unit indicated by the factory function's name. These functions

// exist for convenience, but they are not as efficient as the integral

// factories, which should be preferred.

//

// Example:

//

//   auto a = absl::Seconds(1.5);        // OK

//   auto b = absl::Milliseconds(1500);  // BETTER

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Nanoseconds(T n) {

  return n * Nanoseconds(1);

}

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Microseconds(T n) {

  return n * Microseconds(1);

}

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Milliseconds(T n) {

  return n * Milliseconds(1);

}

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Seconds(T n) {

  if (n >= 0) {  // Note: `NaN >= 0` is false.

    if (n >= static_cast<T>((std::numeric_limits<int64_t>::max)())) {

      return InfiniteDuration();

    }

    return time_internal::MakePosDoubleDuration(n);

  } else {

    if (std::isnan(n))

      return std::signbit(n) ? -InfiniteDuration() : InfiniteDuration();

    if (n <= (std::numeric_limits<int64_t>::min)()) return -InfiniteDuration();

    return -time_internal::MakePosDoubleDuration(-n);

  }

}

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Minutes(T n) {

  return n * Minutes(1);

}

template <typename T, time_internal::EnableIfFloat<T> = 0>

ABSL_ATTRIBUTE_CONST_FUNCTION Duration Hours(T n) {

  return n * Hours(1);

}

// ToInt64Nanoseconds()

// ToInt64Microseconds()

// ToInt64Milliseconds()

// ToInt64Seconds()

// ToInt64Minutes()

// ToInt64Hours()

//

// Helper functions that convert a Duration to an integral count of the

// indicated unit. These return the same results as the `IDivDuration()`

// function, though they usually do so more efficiently; see the

// documentation of `IDivDuration()` for details about overflow, etc.

//

// Example:

//

//   absl::Duration d = absl::Milliseconds(1500);

//   int64_t isec = absl::ToInt64Seconds(d);  // isec == 1

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Nanoseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Microseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Milliseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Seconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Minutes(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Hours(Duration d);

// ToDoubleNanoseconds()

// ToDoubleMicroseconds()

// ToDoubleMilliseconds()

// ToDoubleSeconds()

// ToDoubleMinutes()

// ToDoubleHours()

//

// Helper functions that convert a Duration to a floating point count of the

// indicated unit. These functions are shorthand for the `FDivDuration()`

// function above; see its documentation for details about overflow, etc.

//

// Example:

//

//   absl::Duration d = absl::Milliseconds(1500);

//   double dsec = absl::ToDoubleSeconds(d);  // dsec == 1.5

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleNanoseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleMicroseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleMilliseconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleSeconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleMinutes(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToDoubleHours(Duration d);

// FromChrono()

//

// Converts any of the pre-defined std::chrono durations to an absl::Duration.

//

// Example:

//

//   std::chrono::milliseconds ms(123);

//   absl::Duration d = absl::FromChrono(ms);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::nanoseconds& d);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::microseconds& d);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::milliseconds& d);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::seconds& d);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::minutes& d);

ABSL_ATTRIBUTE_PURE_FUNCTION constexpr Duration FromChrono(

    const std::chrono::hours& d);

// ToChronoNanoseconds()

// ToChronoMicroseconds()

// ToChronoMilliseconds()

// ToChronoSeconds()

// ToChronoMinutes()

// ToChronoHours()

//

// Converts an absl::Duration to any of the pre-defined std::chrono durations.

// If overflow would occur, the returned value will saturate at the min/max

// chrono duration value instead.

//

// Example:

//

//   absl::Duration d = absl::Microseconds(123);

//   auto x = absl::ToChronoMicroseconds(d);

//   auto y = absl::ToChronoNanoseconds(d);  // x == y

//   auto z = absl::ToChronoSeconds(absl::InfiniteDuration());

//   // z == std::chrono::seconds::max()

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::nanoseconds ToChronoNanoseconds(

    Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::microseconds ToChronoMicroseconds(

    Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::milliseconds ToChronoMilliseconds(

    Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::seconds ToChronoSeconds(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::minutes ToChronoMinutes(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::hours ToChronoHours(Duration d);

// FormatDuration()

//

// Returns a string representing the duration in the form "72h3m0.5s".

// Returns "inf" or "-inf" for +/- `InfiniteDuration()`.

ABSL_ATTRIBUTE_CONST_FUNCTION std::string FormatDuration(Duration d);

// Output stream operator.

inline std::ostream& operator<<(std::ostream& os, Duration d) {

  return os << FormatDuration(d);

}

// Support for StrFormat(), StrCat() etc.

template <typename Sink>

void AbslStringify(Sink& sink, Duration d) {

  sink.Append(FormatDuration(d));

}

// ParseDuration()

//

// Parses a duration string consisting of a possibly signed sequence of

// decimal numbers, each with an optional fractional part and a unit

// suffix.  The valid suffixes are "ns", "us" "ms", "s", "m", and "h".

// Simple examples include "300ms", "-1.5h", and "2h45m".  Parses "0" as

// `ZeroDuration()`. Parses "inf" and "-inf" as +/- `InfiniteDuration()`.

bool ParseDuration(absl::string_view dur_string, Duration* d);

// AbslParseFlag()

//

// Parses a command-line flag string representation `text` into a Duration

// value. Duration flags must be specified in a format that is valid input for

// `absl::ParseDuration()`.

bool AbslParseFlag(absl::string_view text, Duration* dst, std::string* error);

// AbslUnparseFlag()

//

// Unparses a Duration value into a command-line string representation using

// the format specified by `absl::ParseDuration()`.

std::string AbslUnparseFlag(Duration d);

ABSL_DEPRECATED("Use AbslParseFlag() instead.")

bool ParseFlag(const std::string& text, Duration* dst, std::string* error);

ABSL_DEPRECATED("Use AbslUnparseFlag() instead.")

std::string UnparseFlag(Duration d);

// Time

//

// An `absl::Time` represents a specific instant in time. Arithmetic operators

// are provided for naturally expressing time calculations. Instances are

// created using `absl::Now()` and the `absl::From*()` factory functions that

// accept the gamut of other time representations. Formatting and parsing

// functions are provided for conversion to and from strings.  `absl::Time`

// should be passed by value rather than const reference.

//

// `absl::Time` assumes there are 60 seconds in a minute, which means the

// underlying time scales must be "smeared" to eliminate leap seconds.

// See https://developers.google.com/time/smear.

//

// Even though `absl::Time` supports a wide range of timestamps, exercise

// caution when using values in the distant past. `absl::Time` uses the

// Proleptic Gregorian calendar, which extends the Gregorian calendar backward

// to dates before its introduction in 1582.

// See https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar

// for more information. Use the ICU calendar classes to convert a date in

// some other calendar (http://userguide.icu-project.org/datetime/calendar).

//

// Similarly, standardized time zones are a reasonably recent innovation, with

// the Greenwich prime meridian being established in 1884. The TZ database

// itself does not profess accurate offsets for timestamps prior to 1970. The

// breakdown of future timestamps is subject to the whim of regional

// governments.

//

// The `absl::Time` class represents an instant in time as a count of clock

// ticks of some granularity (resolution) from some starting point (epoch).

//

// `absl::Time` uses a resolution that is high enough to avoid loss in

// precision, and a range that is wide enough to avoid overflow, when

// converting between tick counts in most Google time scales (i.e., resolution

// of at least one nanosecond, and range +/-100 billion years).  Conversions

// between the time scales are performed by truncating (towards negative

// infinity) to the nearest representable point.

//

// Examples:

//

//   absl::Time t1 = ...;

//   absl::Time t2 = t1 + absl::Minutes(2);

//   absl::Duration d = t2 - t1;  // == absl::Minutes(2)

//

class Time {

 public:

  // Value semantics.

  // Returns the Unix epoch.  However, those reading your code may not know

  // or expect the Unix epoch as the default value, so make your code more

  // readable by explicitly initializing all instances before use.

  //

  // Example:

  //   absl::Time t = absl::UnixEpoch();

  //   absl::Time t = absl::Now();

  //   absl::Time t = absl::TimeFromTimeval(tv);

  //   absl::Time t = absl::InfinitePast();

  constexpr Time() = default;

  // Copyable.

  constexpr Time(const Time& t) = default;

  Time& operator=(const Time& t) = default;

  // Assignment operators.

  Time& operator+=(Duration d) {

    rep_ += d;

    return *this;

  }

  Time& operator-=(Duration d) {

    rep_ -= d;

    return *this;

  }

  // Time::Breakdown

  //

  // The calendar and wall-clock (aka "civil time") components of an

  // `absl::Time` in a certain `absl::TimeZone`. This struct is not

  // intended to represent an instant in time. So, rather than passing

  // a `Time::Breakdown` to a function, pass an `absl::Time` and an

  // `absl::TimeZone`.

  //

  // Deprecated. Use `absl::TimeZone::CivilInfo`.

  struct ABSL_DEPRECATED("Use `absl::TimeZone::CivilInfo`.") Breakdown {

    int64_t year;        // year (e.g., 2013)

    int month;           // month of year [1:12]

    int day;             // day of month [1:31]

    int hour;            // hour of day [0:23]

    int minute;          // minute of hour [0:59]

    int second;          // second of minute [0:59]

    Duration subsecond;  // [Seconds(0):Seconds(1)) if finite

    int weekday;         // 1==Mon, ..., 7=Sun

    int yearday;         // day of year [1:366]

    // Note: The following fields exist for backward compatibility

    // with older APIs.  Accessing these fields directly is a sign of

    // imprudent logic in the calling code.  Modern time-related code

    // should only access this data indirectly by way of FormatTime().

    // These fields are undefined for InfiniteFuture() and InfinitePast().

    int offset;             // seconds east of UTC

    bool is_dst;            // is offset non-standard?

    const char* zone_abbr;  // time-zone abbreviation (e.g., "PST")

  };

  // Time::In()

  //

  // Returns the breakdown of this instant in the given TimeZone.

  //

  // Deprecated. Use `absl::TimeZone::At(Time)`.

  ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING

  ABSL_DEPRECATED("Use `absl::TimeZone::At(Time)`.")

  Breakdown In(TimeZone tz) const;

  ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING

  template <typename H>

  friend H AbslHashValue(H h, Time t) {

    return H::combine(std::move(h), t.rep_);

  }

 private:

  friend constexpr Time time_internal::FromUnixDuration(Duration d);

  friend constexpr Duration time_internal::ToUnixDuration(Time t);

  friend constexpr bool operator<(Time lhs, Time rhs);

  friend constexpr bool operator==(Time lhs, Time rhs);

  friend Duration operator-(Time lhs, Time rhs);

  friend constexpr Time UniversalEpoch();

  friend constexpr Time InfiniteFuture();

  friend constexpr Time InfinitePast();

  constexpr explicit Time(Duration rep) : rep_(rep) {}

  Duration rep_;

};

// Relational Operators

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator<(Time lhs, Time rhs) {

  return lhs.rep_ < rhs.rep_;

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator>(Time lhs, Time rhs) {

  return rhs < lhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator>=(Time lhs, Time rhs) {

  return !(lhs < rhs);

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator<=(Time lhs, Time rhs) {

  return !(rhs < lhs);

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator==(Time lhs, Time rhs) {

  return lhs.rep_ == rhs.rep_;

}

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr bool operator!=(Time lhs, Time rhs) {

  return !(lhs == rhs);

}

// Additive Operators

ABSL_ATTRIBUTE_CONST_FUNCTION inline Time operator+(Time lhs, Duration rhs) {

  return lhs += rhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline Time operator+(Duration lhs, Time rhs) {

  return rhs += lhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline Time operator-(Time lhs, Duration rhs) {

  return lhs -= rhs;

}

ABSL_ATTRIBUTE_CONST_FUNCTION inline Duration operator-(Time lhs, Time rhs) {

  return lhs.rep_ - rhs.rep_;

}

// UnixEpoch()

//

// Returns the `absl::Time` representing "1970-01-01 00:00:00.0 +0000".

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time UnixEpoch() { return Time(); }

// UniversalEpoch()

//

// Returns the `absl::Time` representing "0001-01-01 00:00:00.0 +0000", the

// epoch of the ICU Universal Time Scale.

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time UniversalEpoch() {

  // 719162 is the number of days from 0001-01-01 to 1970-01-01,

  // assuming the Gregorian calendar.

  return Time(

      time_internal::MakeDuration(-24 * 719162 * int64_t{3600}, uint32_t{0}));

}

// InfiniteFuture()

//

// Returns an `absl::Time` that is infinitely far in the future.

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time InfiniteFuture() {

  return Time(time_internal::MakeDuration((std::numeric_limits<int64_t>::max)(),

                                          ~uint32_t{0}));

}

// InfinitePast()

//

// Returns an `absl::Time` that is infinitely far in the past.

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time InfinitePast() {

  return Time(time_internal::MakeDuration((std::numeric_limits<int64_t>::min)(),

                                          ~uint32_t{0}));

}

// FromUnixNanos()

// FromUnixMicros()

// FromUnixMillis()

// FromUnixSeconds()

// FromTimeT()

// FromUDate()

// FromUniversal()

//

// Creates an `absl::Time` from a variety of other representations.  See

// https://unicode-org.github.io/icu/userguide/datetime/universaltimescale.html

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixNanos(int64_t ns);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixMicros(int64_t us);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixMillis(int64_t ms);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromUnixSeconds(int64_t s);

ABSL_ATTRIBUTE_CONST_FUNCTION constexpr Time FromTimeT(time_t t);

ABSL_ATTRIBUTE_CONST_FUNCTION Time FromUDate(double udate);

ABSL_ATTRIBUTE_CONST_FUNCTION Time FromUniversal(int64_t universal);

// ToUnixNanos()

// ToUnixMicros()

// ToUnixMillis()

// ToUnixSeconds()

// ToTimeT()

// ToUDate()

// ToUniversal()

//

// Converts an `absl::Time` to a variety of other representations.  See

// https://unicode-org.github.io/icu/userguide/datetime/universaltimescale.html

//

// Note that these operations round down toward negative infinity where

// necessary to adjust to the resolution of the result type.  Beware of

// possible time_t over/underflow in ToTime{T,val,spec}() on 32-bit platforms.

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixNanos(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixMicros(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixMillis(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUnixSeconds(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION time_t ToTimeT(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION double ToUDate(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToUniversal(Time t);

// DurationFromTimespec()

// DurationFromTimeval()

// ToTimespec()

// ToTimeval()

// TimeFromTimespec()

// TimeFromTimeval()

// ToTimespec()

// ToTimeval()

//

// Some APIs use a timespec or a timeval as a Duration (e.g., nanosleep(2)

// and select(2)), while others use them as a Time (e.g. clock_gettime(2)

// and gettimeofday(2)), so conversion functions are provided for both cases.

// The "to timespec/val" direction is easily handled via overloading, but

// for "from timespec/val" the desired type is part of the function name.

ABSL_ATTRIBUTE_CONST_FUNCTION Duration DurationFromTimespec(timespec ts);

ABSL_ATTRIBUTE_CONST_FUNCTION Duration DurationFromTimeval(timeval tv);

ABSL_ATTRIBUTE_CONST_FUNCTION timespec ToTimespec(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION timeval ToTimeval(Duration d);

ABSL_ATTRIBUTE_CONST_FUNCTION Time TimeFromTimespec(timespec ts);

ABSL_ATTRIBUTE_CONST_FUNCTION Time TimeFromTimeval(timeval tv);

ABSL_ATTRIBUTE_CONST_FUNCTION timespec ToTimespec(Time t);

ABSL_ATTRIBUTE_CONST_FUNCTION timeval ToTimeval(Time t);

// FromChrono()

//

// Converts a std::chrono::system_clock::time_point to an absl::Time.

//

// Example:

//

//   auto tp = std::chrono::system_clock::from_time_t(123);

//   absl::Time t = absl::FromChrono(tp);

//   // t == absl::FromTimeT(123)

ABSL_ATTRIBUTE_PURE_FUNCTION Time

FromChrono(const std::chrono::system_clock::time_point& tp);

// ToChronoTime()

//

// Converts an absl::Time to a std::chrono::system_clock::time_point. If

// overflow would occur, the returned value will saturate at the min/max time

// point value instead.

//

// Example:

//

//   absl::Time t = absl::FromTimeT(123);

//   auto tp = absl::ToChronoTime(t);

//   // tp == std::chrono::system_clock::from_time_t(123);

ABSL_ATTRIBUTE_CONST_FUNCTION std::chrono::system_clock::time_point

    ToChronoTime(Time);

// AbslParseFlag()

//

// Parses the command-line flag string representation `text` into a Time value.

// Time flags must be specified in a format that matches absl::RFC3339_full.

//

// For example:

//

//   --start_time=2016-01-02T03:04:05.678+08:00

//

// Note: A UTC offset (or 'Z' indicating a zero-offset from UTC) is required.

//

// Additionally, if you'd like to specify a time as a count of

// seconds/milliseconds/etc from the Unix epoch, use an absl::Duration flag

// and add that duration to absl::UnixEpoch() to get an absl::Time.

bool AbslParseFlag(absl::string_view text, Time* t, std::string* error);

// AbslUnparseFlag()

//

// Unparses a Time value into a command-line string representation using

// the format specified by `absl::ParseTime()`.

std::string AbslUnparseFlag(Time t);

ABSL_DEPRECATED("Use AbslParseFlag() instead.")

bool ParseFlag(const std::string& text, Time* t, std::string* error);

ABSL_DEPRECATED("Use AbslUnparseFlag() instead.")

std::string UnparseFlag(Time t);

// TimeZone

//

// The `absl::TimeZone` is an opaque, small, value-type class representing a

// geo-political region within which particular rules are used for converting

// between absolute and civil times (see https://git.io/v59Ly). `absl::TimeZone`

// values are named using the TZ identifiers from the IANA Time Zone Database,

// such as "America/Los_Angeles" or "Australia/Sydney". `absl::TimeZone` values

// are created from factory functions such as `absl::LoadTimeZone()`. Note:

// strings like "PST" and "EDT" are not valid TZ identifiers. Prefer to pass by

// value rather than const reference.

//

// For more on the fundamental concepts of time zones, absolute times, and civil

// times, see https://github.com/google/cctz#fundamental-concepts

//

// Examples:

//

//   absl::TimeZone utc = absl::UTCTimeZone();

//   absl::TimeZone pst = absl::FixedTimeZone(-8 * 60 * 60);

//   absl::TimeZone loc = absl::LocalTimeZone();

//   absl::TimeZone lax;

//   if (!absl::LoadTimeZone("America/Los_Angeles", &lax)) {

//     // handle error case

//   }

//

// See also:

// - https://github.com/google/cctz

// - https://www.iana.org/time-zones

// - https://en.wikipedia.org/wiki/Zoneinfo

class TimeZone {

 public:

  explicit TimeZone(time_internal::cctz::time_zone tz) : cz_(tz) {}

  TimeZone() = default;  // UTC, but prefer UTCTimeZone() to be explicit.

  // Copyable.

  TimeZone(const TimeZone&) = default;

  TimeZone& operator=(const TimeZone&) = default;

  explicit operator time_internal::cctz::time_zone() const { return cz_; }

  std::string name() const { return cz_.name(); }

  // TimeZone::CivilInfo

  //

  // Information about the civil time corresponding to an absolute time.

  // This struct is not intended to represent an instant in time. So, rather

  // than passing a `TimeZone::CivilInfo` to a function, pass an `absl::Time`

  // and an `absl::TimeZone`.

  struct CivilInfo {

    CivilSecond cs;

    Duration subsecond;

    // Note: The following fields exist for backward compatibility

    // with older APIs.  Accessing these fields directly is a sign of

    // imprudent logic in the calling code.  Modern time-related code

    // should only access this data indirectly by way of FormatTime().

    // These fields are undefined for InfiniteFuture() and InfinitePast().

    int offset;             // seconds east of UTC

    bool is_dst;            // is offset non-standard?

    const char* zone_abbr;  // time-zone abbreviation (e.g., "PST")

  };