chore(3p/abseil_cpp): unvendor abseil_cpp r/3786

we weren't actually using these sources anymore, okay?

Change-Id: If701571d9716de308d3512e1eb22c35db0877a66
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5248
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: tazjin <tazjin@tvl.su>

1 files changed, 0 insertions, 1581 deletions

diff --git a/third_party/abseil_cpp/absl/time/time.h b/third_party/abseil_cpp/absl/time/time.h
deleted file mode 100644
index 72508031acd6..000000000000
--- a/third_party/abseil_cpp/absl/time/time.h
+++ /dev/null
@@ -1,1581 +0,0 @@
-// 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 <ostream>
-#include <string>
-#include <type_traits>
-#include <utility>
-
-#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);
-constexpr Time FromUnixDuration(Duration d);
-constexpr Duration ToUnixDuration(Time t);
-constexpr int64_t GetRepHi(Duration d);
-constexpr uint32_t GetRepLo(Duration d);
-constexpr Duration MakeDuration(int64_t hi, uint32_t lo);
-constexpr Duration MakeDuration(int64_t hi, int64_t lo);
-inline Duration MakePosDoubleDuration(double n);
-constexpr int64_t kTicksPerNanosecond = 4;
-constexpr int64_t kTicksPerSecond = 1000 * 1000 * 1000 * kTicksPerNanosecond;
-template <std::intmax_t N>
-constexpr Duration FromInt64(int64_t v, std::ratio<1, N>);
-constexpr Duration FromInt64(int64_t v, std::ratio<60>);
-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 span 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 < 1910
-  // 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.
-  template <typename T>
-  Duration& operator*=(T r) {
-    int64_t x = r;
-    return *this *= x;
-  }
-  template <typename T>
-  Duration& operator/=(T r) {
-    int64_t x = r;
-    return *this /= x;
-  }
-  Duration& operator*=(float r) { return *this *= static_cast<double>(r); }
-  Duration& operator/=(float r) { return *this /= static_cast<double>(r); }
-
-  template <typename H>
-  friend H AbslHashValue(H h, Duration d) {
-    return H::combine(std::move(h), d.rep_hi_, 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) {}
-  int64_t rep_hi_;
-  uint32_t rep_lo_;
-};
-
-// Relational Operators
-constexpr bool operator<(Duration lhs, Duration rhs);
-constexpr bool operator>(Duration lhs, Duration rhs) { return rhs < lhs; }
-constexpr bool operator>=(Duration lhs, Duration rhs) { return !(lhs < rhs); }
-constexpr bool operator<=(Duration lhs, Duration rhs) { return !(rhs < lhs); }
-constexpr bool operator==(Duration lhs, Duration rhs);
-constexpr bool operator!=(Duration lhs, Duration rhs) { return !(lhs == rhs); }
-
-// Additive Operators
-constexpr Duration operator-(Duration d);
-inline Duration operator+(Duration lhs, Duration rhs) { return lhs += rhs; }
-inline Duration operator-(Duration lhs, Duration rhs) { return lhs -= rhs; }
-
-// Multiplicative Operators
-// Integer operands must be representable as int64_t.
-template <typename T>
-Duration operator*(Duration lhs, T rhs) {
-  return lhs *= rhs;
-}
-template <typename T>
-Duration operator*(T lhs, Duration rhs) {
-  return rhs *= lhs;
-}
-template <typename T>
-Duration operator/(Duration lhs, T rhs) {
-  return lhs /= rhs;
-}
-inline int64_t operator/(Duration lhs, Duration rhs) {
-  return time_internal::IDivDuration(true, lhs, rhs,
-                                     &lhs);  // trunc towards zero
-}
-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
-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.
-constexpr Duration ZeroDuration() { return Duration(); }
-
-// AbsDuration()
-//
-// Returns the absolute value of a duration.
-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
-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
-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
-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()`.
-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
-constexpr Duration Nanoseconds(int64_t n);
-constexpr Duration Microseconds(int64_t n);
-constexpr Duration Milliseconds(int64_t n);
-constexpr Duration Seconds(int64_t n);
-constexpr Duration Minutes(int64_t n);
-constexpr Duration Hours(int64_t n);
-
-// 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>
-Duration Nanoseconds(T n) {
-  return n * Nanoseconds(1);
-}
-template <typename T, time_internal::EnableIfFloat<T> = 0>
-Duration Microseconds(T n) {
-  return n * Microseconds(1);
-}
-template <typename T, time_internal::EnableIfFloat<T> = 0>
-Duration Milliseconds(T n) {
-  return n * Milliseconds(1);
-}
-template <typename T, time_internal::EnableIfFloat<T> = 0>
-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>
-Duration Minutes(T n) {
-  return n * Minutes(1);
-}
-template <typename T, time_internal::EnableIfFloat<T> = 0>
-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 functions are shorthand for the `IDivDuration()`
-// function above; see its documentation for details about overflow, etc.
-//
-// Example:
-//
-//   absl::Duration d = absl::Milliseconds(1500);
-//   int64_t isec = absl::ToInt64Seconds(d);  // isec == 1
-int64_t ToInt64Nanoseconds(Duration d);
-int64_t ToInt64Microseconds(Duration d);
-int64_t ToInt64Milliseconds(Duration d);
-int64_t ToInt64Seconds(Duration d);
-int64_t ToInt64Minutes(Duration d);
-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
-double ToDoubleNanoseconds(Duration d);
-double ToDoubleMicroseconds(Duration d);
-double ToDoubleMilliseconds(Duration d);
-double ToDoubleSeconds(Duration d);
-double ToDoubleMinutes(Duration d);
-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);
-constexpr Duration FromChrono(const std::chrono::nanoseconds& d);
-constexpr Duration FromChrono(const std::chrono::microseconds& d);
-constexpr Duration FromChrono(const std::chrono::milliseconds& d);
-constexpr Duration FromChrono(const std::chrono::seconds& d);
-constexpr Duration FromChrono(const std::chrono::minutes& d);
-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()
-std::chrono::nanoseconds ToChronoNanoseconds(Duration d);
-std::chrono::microseconds ToChronoMicroseconds(Duration d);
-std::chrono::milliseconds ToChronoMilliseconds(Duration d);
-std::chrono::seconds ToChronoSeconds(Duration d);
-std::chrono::minutes ToChronoMinutes(Duration d);
-std::chrono::hours ToChronoHours(Duration d);
-
-// FormatDuration()
-//
-// Returns a string representing the duration in the form "72h3m0.5s".
-// Returns "inf" or "-inf" for +/- `InfiniteDuration()`.
-std::string FormatDuration(Duration d);
-
-// Output stream operator.
-inline std::ostream& operator<<(std::ostream& os, Duration d) {
-  return os << 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);
-
-// Support for flag values of type Duration. 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);
-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
-      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)`.
-  Breakdown In(TimeZone tz) const;
-
-  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
-constexpr bool operator<(Time lhs, Time rhs) { return lhs.rep_ < rhs.rep_; }
-constexpr bool operator>(Time lhs, Time rhs) { return rhs < lhs; }
-constexpr bool operator>=(Time lhs, Time rhs) { return !(lhs < rhs); }
-constexpr bool operator<=(Time lhs, Time rhs) { return !(rhs < lhs); }
-constexpr bool operator==(Time lhs, Time rhs) { return lhs.rep_ == rhs.rep_; }
-constexpr bool operator!=(Time lhs, Time rhs) { return !(lhs == rhs); }
-
-// Additive Operators
-inline Time operator+(Time lhs, Duration rhs) { return lhs += rhs; }
-inline Time operator+(Duration lhs, Time rhs) { return rhs += lhs; }
-inline Time operator-(Time lhs, Duration rhs) { return lhs -= rhs; }
-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".
-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.
-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}, 0U));
-}
-
-// InfiniteFuture()
-//
-// Returns an `absl::Time` that is infinitely far in the future.
-constexpr Time InfiniteFuture() {
-  return Time(
-      time_internal::MakeDuration((std::numeric_limits<int64_t>::max)(), ~0U));
-}
-
-// InfinitePast()
-//
-// Returns an `absl::Time` that is infinitely far in the past.
-constexpr Time InfinitePast() {
-  return Time(
-      time_internal::MakeDuration((std::numeric_limits<int64_t>::min)(), ~0U));
-}
-
-// FromUnixNanos()
-// FromUnixMicros()
-// FromUnixMillis()
-// FromUnixSeconds()
-// FromTimeT()
-// FromUDate()
-// FromUniversal()
-//
-// Creates an `absl::Time` from a variety of other representations.
-constexpr Time FromUnixNanos(int64_t ns);
-constexpr Time FromUnixMicros(int64_t us);
-constexpr Time FromUnixMillis(int64_t ms);
-constexpr Time FromUnixSeconds(int64_t s);
-constexpr Time FromTimeT(time_t t);
-Time FromUDate(double udate);
-Time FromUniversal(int64_t universal);
-
-// ToUnixNanos()
-// ToUnixMicros()
-// ToUnixMillis()
-// ToUnixSeconds()
-// ToTimeT()
-// ToUDate()
-// ToUniversal()
-//
-// Converts an `absl::Time` to a variety of other representations.  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.
-int64_t ToUnixNanos(Time t);
-int64_t ToUnixMicros(Time t);
-int64_t ToUnixMillis(Time t);
-int64_t ToUnixSeconds(Time t);
-time_t ToTimeT(Time t);
-double ToUDate(Time t);
-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.
-Duration DurationFromTimespec(timespec ts);
-Duration DurationFromTimeval(timeval tv);
-timespec ToTimespec(Duration d);
-timeval ToTimeval(Duration d);
-Time TimeFromTimespec(timespec ts);
-Time TimeFromTimeval(timeval tv);
-timespec ToTimespec(Time t);
-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)
-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);
-std::chrono::system_clock::time_point ToChronoTime(Time);
-
-// Support for flag values of type Time. 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);
-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")
-  };
-
-  // TimeZone::At(Time)
-  //
-  // Returns the civil time for this TimeZone at a certain `absl::Time`.
-  // If the input time is infinite, the output civil second will be set to
-  // CivilSecond::max() or min(), and the subsecond will be infinite.
-  //
-  // Example:
-  //
-  //   const auto epoch = lax.At(absl::UnixEpoch());
-  //   // epoch.cs == 1969-12-31 16:00:00
-  //   // epoch.subsecond == absl::ZeroDuration()
-  //   // epoch.offset == -28800
-  //   // epoch.is_dst == false
-  //   // epoch.abbr == "PST"
-  CivilInfo At(Time t) const;
-
-  // TimeZone::TimeInfo
-  //
-  // Information about the absolute times corresponding to a civil time.
-  // (Subseconds must be handled separately.)
-  //
-  // It is possible for a caller to pass a civil-time value that does
-  // not represent an actual or unique instant in time (due to a shift
-  // in UTC offset in the TimeZone, which results in a discontinuity in
-  // the civil-time components). For example, a daylight-saving-time
-  // transition skips or repeats civil times---in the United States,
-  // March 13, 2011 02:15 never occurred, while November 6, 2011 01:15
-  // occurred twice---so requests for such times are not well-defined.
-  // To account for these possibilities, `absl::TimeZone::TimeInfo` is
-  // richer than just a single `absl::Time`.
-  struct TimeInfo {
-    enum CivilKind {
-      UNIQUE,    // the civil time was singular (pre == trans == post)
-      SKIPPED,   // the civil time did not exist (pre >= trans > post)
-      REPEATED,  // the civil time was ambiguous (pre < trans <= post)
-    } kind;
-    Time pre;    // time calculated using the pre-transition offset
-    Time trans;  // when the civil-time discontinuity occurred
-    Time post;   // time calculated using the post-transition offset
-  };
-
-  // TimeZone::At(CivilSecond)
-  //
-  // Returns an `absl::TimeInfo` containing the absolute time(s) for this
-  // TimeZone at an `absl::CivilSecond`. When the civil time is skipped or
-  // repeated, returns times calculated using the pre-transition and post-
-  // transition UTC offsets, plus the transition time itself.
-  //
-  // Examples:
-  //
-  //   // A unique civil time
-  //   const auto jan01 = lax.At(absl::CivilSecond(2011, 1, 1, 0, 0, 0));
-  //   // jan01.kind == TimeZone::TimeInfo::UNIQUE
-  //   // jan01.pre    is 2011-01-01 00:00:00 -0800
-  //   // jan01.trans  is 2011-01-01 00:00:00 -0800
-  //   // jan01.post   is 2011-01-01 00:00:00 -0800
-  //
-  //   // A Spring DST transition, when there is a gap in civil time
-  //   const auto mar13 = lax.At(absl::CivilSecond(2011, 3, 13, 2, 15, 0));
-  //   // mar13.kind == TimeZone::TimeInfo::SKIPPED
-  //   // mar13.pre   is 2011-03-13 03:15:00 -0700
-  //   // mar13.trans is 2011-03-13 03:00:00 -0700
-  //   // mar13.post  is 2011-03-13 01:15:00 -0800
-  //
-  //   // A Fall DST transition, when civil times are repeated
-  //   const auto nov06 = lax.At(absl::CivilSecond(2011, 11, 6, 1, 15, 0));
-  //   // nov06.kind == TimeZone::TimeInfo::REPEATED
-  //   // nov06.pre   is 2011-11-06 01:15:00 -0700
-  //   // nov06.trans is 2011-11-06 01:00:00 -0800
-  //   // nov06.post  is 2011-11-06 01:15:00 -0800
-  TimeInfo At(CivilSecond ct) const;
-
-  // TimeZone::NextTransition()
-  // TimeZone::PrevTransition()
-  //
-  // Finds the time of the next/previous offset change in this time zone.
-  //
-  // By definition, `NextTransition(t, &trans)` returns false when `t` is
-  // `InfiniteFuture()`, and `PrevTransition(t, &trans)` returns false
-  // when `t` is `InfinitePast()`. If the zone has no transitions, the
-  // result will also be false no matter what the argument.
-  //
-  // Otherwise, when `t` is `InfinitePast()`, `NextTransition(t, &trans)`
-  // returns true and sets `trans` to the first recorded transition. Chains
-  // of calls to `NextTransition()/PrevTransition()` will eventually return
-  // false, but it is unspecified exactly when `NextTransition(t, &trans)`
-  // jumps to false, or what time is set by `PrevTransition(t, &trans)` for
-  // a very distant `t`.
-  //
-  // Note: Enumeration of time-zone transitions is for informational purposes
-  // only. Modern time-related code should not care about when offset changes
-  // occur.
-  //
-  // Example:
-  //   absl::TimeZone nyc;
-  //   if (!absl::LoadTimeZone("America/New_York", &nyc)) { ... }
-  //   const auto now = absl::Now();
-  //   auto t = absl::InfinitePast();
-  //   absl::TimeZone::CivilTransition trans;
-  //   while (t <= now && nyc.NextTransition(t, &trans)) {
-  //     // transition: trans.from -> trans.to
-  //     t = nyc.At(trans.to).trans;
-  //   }
-  struct CivilTransition {
-    CivilSecond from;  // the civil time we jump from
-    CivilSecond to;    // the civil time we jump to
-  };
-  bool NextTransition(Time t, CivilTransition* trans) const;
-  bool PrevTransition(Time t, CivilTransition* trans) const;
-
-  template <typename H>
-  friend H AbslHashValue(H h, TimeZone tz) {
-    return H::combine(std::move(h), tz.cz_);
-  }
-
- private:
-  friend bool operator==(TimeZone a, TimeZone b) { return a.cz_ == b.cz_; }
-  friend bool operator!=(TimeZone a, TimeZone b) { return a.cz_ != b.cz_; }
-  friend std::ostream& operator<<(std::ostream& os, TimeZone tz) {
-    return os << tz.name();
-  }
-
-  time_internal::cctz::time_zone cz_;
-};
-
-// LoadTimeZone()
-//
-// Loads the named zone. May perform I/O on the initial load of the named
-// zone. If the name is invalid, or some other kind of error occurs, returns
-// `false` and `*tz` is set to the UTC time zone.
-inline bool LoadTimeZone(absl::string_view name, TimeZone* tz) {
-  if (name == "localtime") {
-    *tz = TimeZone(time_internal::cctz::local_time_zone());
-    return true;
-  }
-  time_internal::cctz::time_zone cz;
-  const bool b = time_internal::cctz::load_time_zone(std::string(name), &cz);
-  *tz = TimeZone(cz);
-  return b;
-}
-
-// FixedTimeZone()
-//
-// Returns a TimeZone that is a fixed offset (seconds east) from UTC.
-// Note: If the absolute value of the offset is greater than 24 hours
-// you'll get UTC (i.e., no offset) instead.
-inline TimeZone FixedTimeZone(int seconds) {
-  return TimeZone(
-      time_internal::cctz::fixed_time_zone(std::chrono::seconds(seconds)));
-}
-
-// UTCTimeZone()
-//
-// Convenience method returning the UTC time zone.
-inline TimeZone UTCTimeZone() {
-  return TimeZone(time_internal::cctz::utc_time_zone());
-}
-
-// LocalTimeZone()
-//
-// Convenience method returning the local time zone, or UTC if there is
-// no configured local zone.  Warning: Be wary of using LocalTimeZone(),
-// and particularly so in a server process, as the zone configured for the
-// local machine should be irrelevant.  Prefer an explicit zone name.
-inline TimeZone LocalTimeZone() {
-  return TimeZone(time_internal::cctz::local_time_zone());
-}
-
-// ToCivilSecond()
-// ToCivilMinute()
-// ToCivilHour()
-// ToCivilDay()
-// ToCivilMonth()
-// ToCivilYear()
-//
-// Helpers for TimeZone::At(Time) to return particularly aligned civil times.
-//
-// Example:
-//
-//   absl::Time t = ...;
-//   absl::TimeZone tz = ...;
-//   const auto cd = absl::ToCivilDay(t, tz);
-inline CivilSecond ToCivilSecond(Time t, TimeZone tz) {
-  return tz.At(t).cs;  // already a CivilSecond
-}
-inline CivilMinute ToCivilMinute(Time t, TimeZone tz) {
-  return CivilMinute(tz.At(t).cs);
-}
-inline CivilHour ToCivilHour(Time t, TimeZone tz) {
-  return CivilHour(tz.At(t).cs);
-}
-inline CivilDay ToCivilDay(Time t, TimeZone tz) {
-  return CivilDay(tz.At(t).cs);
-}
-inline CivilMonth ToCivilMonth(Time t, TimeZone tz) {
-  return CivilMonth(tz.At(t).cs);
-}
-inline CivilYear ToCivilYear(Time t, TimeZone tz) {
-  return CivilYear(tz.At(t).cs);
-}
-
-// FromCivil()
-//
-// Helper for TimeZone::At(CivilSecond) that provides "order-preserving
-// semantics." If the civil time maps to a unique time, that time is
-// returned. If the civil time is repeated in the given time zone, the
-// time using the pre-transition offset is returned. Otherwise, the
-// civil time is skipped in the given time zone, and the transition time
-// is returned. This means that for any two civil times, ct1 and ct2,
-// (ct1 < ct2) => (FromCivil(ct1) <= FromCivil(ct2)), the equal case
-// being when two non-existent civil times map to the same transition time.
-//
-// Note: Accepts civil times of any alignment.
-inline Time FromCivil(CivilSecond ct, TimeZone tz) {
-  const auto ti = tz.At(ct);
-  if (ti.kind == TimeZone::TimeInfo::SKIPPED) return ti.trans;
-  return ti.pre;
-}
-
-// TimeConversion
-//
-// An `absl::TimeConversion` represents the conversion of year, month, day,
-// hour, minute, and second values (i.e., a civil time), in a particular
-// `absl::TimeZone`, to a time instant (an absolute time), as returned by
-// `absl::ConvertDateTime()`. Legacy version of `absl::TimeZone::TimeInfo`.
-//
-// Deprecated. Use `absl::TimeZone::TimeInfo`.
-struct
-    TimeConversion {
-  Time pre;    // time calculated using the pre-transition offset
-  Time trans;  // when the civil-time discontinuity occurred
-  Time post;   // time calculated using the post-transition offset
-
-  enum Kind {
-    UNIQUE,    // the civil time was singular (pre == trans == post)
-    SKIPPED,   // the civil time did not exist
-    REPEATED,  // the civil time was ambiguous
-  };
-  Kind kind;
-
-  bool normalized;  // input values were outside their valid ranges
-};
-
-// ConvertDateTime()
-//
-// Legacy version of `absl::TimeZone::At(absl::CivilSecond)` that takes
-// the civil time as six, separate values (YMDHMS).
-//
-// The input month, day, hour, minute, and second values can be outside
-// of their valid ranges, in which case they will be "normalized" during
-// the conversion.
-//
-// Example:
-//
-//   // "October 32" normalizes to "November 1".
-//   absl::TimeConversion tc =
-//       absl::ConvertDateTime(2013, 10, 32, 8, 30, 0, lax);
-//   // tc.kind == TimeConversion::UNIQUE && tc.normalized == true
-//   // absl::ToCivilDay(tc.pre, tz).month() == 11
-//   // absl::ToCivilDay(tc.pre, tz).day() == 1
-//
-// Deprecated. Use `absl::TimeZone::At(CivilSecond)`.
-TimeConversion ConvertDateTime(int64_t year, int mon, int day, int hour,
-                               int min, int sec, TimeZone tz);
-
-// FromDateTime()
-//
-// A convenience wrapper for `absl::ConvertDateTime()` that simply returns
-// the "pre" `absl::Time`.  That is, the unique result, or the instant that
-// is correct using the pre-transition offset (as if the transition never
-// happened).
-//
-// Example:
-//
-//   absl::Time t = absl::FromDateTime(2017, 9, 26, 9, 30, 0, lax);
-//   // t = 2017-09-26 09:30:00 -0700
-//
-// Deprecated. Use `absl::FromCivil(CivilSecond, TimeZone)`. Note that the
-// behavior of `FromCivil()` differs from `FromDateTime()` for skipped civil
-// times. If you care about that see `absl::TimeZone::At(absl::CivilSecond)`.
-inline Time FromDateTime(int64_t year, int mon, int day, int hour,
-                         int min, int sec, TimeZone tz) {
-  return ConvertDateTime(year, mon, day, hour, min, sec, tz).pre;
-}
-
-// FromTM()
-//
-// Converts the `tm_year`, `tm_mon`, `tm_mday`, `tm_hour`, `tm_min`, and
-// `tm_sec` fields to an `absl::Time` using the given time zone. See ctime(3)
-// for a description of the expected values of the tm fields. If the indicated
-// time instant is not unique (see `absl::TimeZone::At(absl::CivilSecond)`
-// above), the `tm_isdst` field is consulted to select the desired instant
-// (`tm_isdst` > 0 means DST, `tm_isdst` == 0 means no DST, `tm_isdst` < 0
-// means use the post-transition offset).
-Time FromTM(const struct tm& tm, TimeZone tz);
-
-// ToTM()
-//
-// Converts the given `absl::Time` to a struct tm using the given time zone.
-// See ctime(3) for a description of the values of the tm fields.
-struct tm ToTM(Time t, TimeZone tz);
-
-// RFC3339_full
-// RFC3339_sec
-//
-// FormatTime()/ParseTime() format specifiers for RFC3339 date/time strings,
-// with trailing zeros trimmed or with fractional seconds omitted altogether.
-//
-// Note that RFC3339_sec[] matches an ISO 8601 extended format for date and
-// time with UTC offset.  Also note the use of "%Y": RFC3339 mandates that
-// years have exactly four digits, but we allow them to take their natural
-// width.
-ABSL_DLL extern const char RFC3339_full[];  // %Y-%m-%d%ET%H:%M:%E*S%Ez
-ABSL_DLL extern const char RFC3339_sec[];   // %Y-%m-%d%ET%H:%M:%S%Ez
-
-// RFC1123_full
-// RFC1123_no_wday
-//
-// FormatTime()/ParseTime() format specifiers for RFC1123 date/time strings.
-ABSL_DLL extern const char RFC1123_full[];     // %a, %d %b %E4Y %H:%M:%S %z
-ABSL_DLL extern const char RFC1123_no_wday[];  // %d %b %E4Y %H:%M:%S %z
-
-// FormatTime()
-//
-// Formats the given `absl::Time` in the `absl::TimeZone` according to the
-// provided format string. Uses strftime()-like formatting options, with
-// the following extensions:
-//
-//   - %Ez  - RFC3339-compatible numeric UTC offset (+hh:mm or -hh:mm)
-//   - %E*z - Full-resolution numeric UTC offset (+hh:mm:ss or -hh:mm:ss)
-//   - %E#S - Seconds with # digits of fractional precision
-//   - %E*S - Seconds with full fractional precision (a literal '*')
-//   - %E#f - Fractional seconds with # digits of precision
-//   - %E*f - Fractional seconds with full precision (a literal '*')
-//   - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999)
-//   - %ET  - The RFC3339 "date-time" separator "T"
-//
-// Note that %E0S behaves like %S, and %E0f produces no characters.  In
-// contrast %E*f always produces at least one digit, which may be '0'.
-//
-// Note that %Y produces as many characters as it takes to fully render the
-// year.  A year outside of [-999:9999] when formatted with %E4Y will produce
-// more than four characters, just like %Y.
-//
-// We recommend that format strings include the UTC offset (%z, %Ez, or %E*z)
-// so that the result uniquely identifies a time instant.
-//
-// Example:
-//
-//   absl::CivilSecond cs(2013, 1, 2, 3, 4, 5);
-//   absl::Time t = absl::FromCivil(cs, lax);
-//   std::string f = absl::FormatTime("%H:%M:%S", t, lax);  // "03:04:05"
-//   f = absl::FormatTime("%H:%M:%E3S", t, lax);  // "03:04:05.000"
-//
-// Note: If the given `absl::Time` is `absl::InfiniteFuture()`, the returned
-// string will be exactly "infinite-future". If the given `absl::Time` is
-// `absl::InfinitePast()`, the returned string will be exactly "infinite-past".
-// In both cases the given format string and `absl::TimeZone` are ignored.
-//
-std::string FormatTime(absl::string_view format, Time t, TimeZone tz);
-
-// Convenience functions that format the given time using the RFC3339_full
-// format.  The first overload uses the provided TimeZone, while the second
-// uses LocalTimeZone().
-std::string FormatTime(Time t, TimeZone tz);
-std::string FormatTime(Time t);
-
-// Output stream operator.
-inline std::ostream& operator<<(std::ostream& os, Time t) {
-  return os << FormatTime(t);
-}
-
-// ParseTime()
-//
-// Parses an input string according to the provided format string and
-// returns the corresponding `absl::Time`. Uses strftime()-like formatting
-// options, with the same extensions as FormatTime(), but with the
-// exceptions that %E#S is interpreted as %E*S, and %E#f as %E*f.  %Ez
-// and %E*z also accept the same inputs, which (along with %z) includes
-// 'z' and 'Z' as synonyms for +00:00.  %ET accepts either 'T' or 't'.
-//
-// %Y consumes as many numeric characters as it can, so the matching data
-// should always be terminated with a non-numeric.  %E4Y always consumes
-// exactly four characters, including any sign.
-//
-// Unspecified fields are taken from the default date and time of ...
-//
-//   "1970-01-01 00:00:00.0 +0000"
-//
-// For example, parsing a string of "15:45" (%H:%M) will return an absl::Time
-// that represents "1970-01-01 15:45:00.0 +0000".
-//
-// Note that since ParseTime() returns time instants, it makes the most sense
-// to parse fully-specified date/time strings that include a UTC offset (%z,
-// %Ez, or %E*z).
-//
-// Note also that `absl::ParseTime()` only heeds the fields year, month, day,
-// hour, minute, (fractional) second, and UTC offset.  Other fields, like
-// weekday (%a or %A), while parsed for syntactic validity, are ignored
-// in the conversion.
-//
-// Date and time fields that are out-of-range will be treated as errors
-// rather than normalizing them like `absl::CivilSecond` does.  For example,
-// it is an error to parse the date "Oct 32, 2013" because 32 is out of range.
-//
-// A leap second of ":60" is normalized to ":00" of the following minute
-// with fractional seconds discarded.  The following table shows how the
-// given seconds and subseconds will be parsed:
-//
-//   "59.x" -> 59.x  // exact
-//   "60.x" -> 00.0  // normalized
-//   "00.x" -> 00.x  // exact
-//
-// Errors are indicated by returning false and assigning an error message
-// to the "err" out param if it is non-null.
-//
-// Note: If the input string is exactly "infinite-future", the returned
-// `absl::Time` will be `absl::InfiniteFuture()` and `true` will be returned.
-// If the input string is "infinite-past", the returned `absl::Time` will be
-// `absl::InfinitePast()` and `true` will be returned.
-//
-bool ParseTime(absl::string_view format, absl::string_view input, Time* time,
-               std::string* err);
-
-// Like ParseTime() above, but if the format string does not contain a UTC
-// offset specification (%z/%Ez/%E*z) then the input is interpreted in the
-// given TimeZone.  This means that the input, by itself, does not identify a
-// unique instant.  Being time-zone dependent, it also admits the possibility
-// of ambiguity or non-existence, in which case the "pre" time (as defined
-// by TimeZone::TimeInfo) is returned.  For these reasons we recommend that
-// all date/time strings include a UTC offset so they're context independent.
-bool ParseTime(absl::string_view format, absl::string_view input, TimeZone tz,
-               Time* time, std::string* err);
-
-// ============================================================================
-// Implementation Details Follow
-// ============================================================================
-
-namespace time_internal {
-
-// Creates a Duration with a given representation.
-// REQUIRES: hi,lo is a valid representation of a Duration as specified
-// in time/duration.cc.
-constexpr Duration MakeDuration(int64_t hi, uint32_t lo = 0) {
-  return Duration(hi, lo);
-}
-
-constexpr Duration MakeDuration(int64_t hi, int64_t lo) {
-  return MakeDuration(hi, static_cast<uint32_t>(lo));
-}
-
-// Make a Duration value from a floating-point number, as long as that number
-// is in the range [ 0 .. numeric_limits<int64_t>::max ), that is, as long as
-// it's positive and can be converted to int64_t without risk of UB.
-inline Duration MakePosDoubleDuration(double n) {
-  const int64_t int_secs = static_cast<int64_t>(n);
-  const uint32_t ticks = static_cast<uint32_t>(
-      (n - static_cast<double>(int_secs)) * kTicksPerSecond + 0.5);
-  return ticks < kTicksPerSecond
-             ? MakeDuration(int_secs, ticks)
-             : MakeDuration(int_secs + 1, ticks - kTicksPerSecond);
-}
-
-// Creates a normalized Duration from an almost-normalized (sec,ticks)
-// pair. sec may be positive or negative.  ticks must be in the range
-// -kTicksPerSecond < *ticks < kTicksPerSecond.  If ticks is negative it
-// will be normalized to a positive value in the resulting Duration.
-constexpr Duration MakeNormalizedDuration(int64_t sec, int64_t ticks) {
-  return (ticks < 0) ? MakeDuration(sec - 1, ticks + kTicksPerSecond)
-                     : MakeDuration(sec, ticks);
-}
-
-// Provide access to the Duration representation.
-constexpr int64_t GetRepHi(Duration d) { return d.rep_hi_; }
-constexpr uint32_t GetRepLo(Duration d) { return d.rep_lo_; }
-
-// Returns true iff d is positive or negative infinity.
-constexpr bool IsInfiniteDuration(Duration d) { return GetRepLo(d) == ~0U; }
-
-// Returns an infinite Duration with the opposite sign.
-// REQUIRES: IsInfiniteDuration(d)
-constexpr Duration OppositeInfinity(Duration d) {
-  return GetRepHi(d) < 0
-             ? MakeDuration((std::numeric_limits<int64_t>::max)(), ~0U)
-             : MakeDuration((std::numeric_limits<int64_t>::min)(), ~0U);
-}
-
-// Returns (-n)-1 (equivalently -(n+1)) without avoidable overflow.
-constexpr int64_t NegateAndSubtractOne(int64_t n) {
-  // Note: Good compilers will optimize this expression to ~n when using
-  // a two's-complement representation (which is required for int64_t).
-  return (n < 0) ? -(n + 1) : (-n) - 1;
-}
-
-// Map between a Time and a Duration since the Unix epoch.  Note that these
-// functions depend on the above mentioned choice of the Unix epoch for the
-// Time representation (and both need to be Time friends).  Without this
-// knowledge, we would need to add-in/subtract-out UnixEpoch() respectively.
-constexpr Time FromUnixDuration(Duration d) { return Time(d); }
-constexpr Duration ToUnixDuration(Time t) { return t.rep_; }
-
-template <std::intmax_t N>
-constexpr Duration FromInt64(int64_t v, std::ratio<1, N>) {
-  static_assert(0 < N && N <= 1000 * 1000 * 1000, "Unsupported ratio");
-  // Subsecond ratios cannot overflow.
-  return MakeNormalizedDuration(
-      v / N, v % N * kTicksPerNanosecond * 1000 * 1000 * 1000 / N);
-}
-constexpr Duration FromInt64(int64_t v, std::ratio<60>) {
-  return (v <= (std::numeric_limits<int64_t>::max)() / 60 &&
-          v >= (std::numeric_limits<int64_t>::min)() / 60)
-             ? MakeDuration(v * 60)
-             : v > 0 ? InfiniteDuration() : -InfiniteDuration();
-}
-constexpr Duration FromInt64(int64_t v, std::ratio<3600>) {
-  return (v <= (std::numeric_limits<int64_t>::max)() / 3600 &&
-          v >= (std::numeric_limits<int64_t>::min)() / 3600)
-             ? MakeDuration(v * 3600)
-             : v > 0 ? InfiniteDuration() : -InfiniteDuration();
-}
-
-// IsValidRep64<T>(0) is true if the expression `int64_t{std::declval<T>()}` is
-// valid. That is, if a T can be assigned to an int64_t without narrowing.
-template <typename T>
-constexpr auto IsValidRep64(int) -> decltype(int64_t{std::declval<T>()} == 0) {
-  return true;
-}
-template <typename T>
-constexpr auto IsValidRep64(char) -> bool {
-  return false;
-}
-
-// Converts a std::chrono::duration to an absl::Duration.
-template <typename Rep, typename Period>
-constexpr Duration FromChrono(const std::chrono::duration<Rep, Period>& d) {
-  static_assert(IsValidRep64<Rep>(0), "duration::rep is invalid");
-  return FromInt64(int64_t{d.count()}, Period{});
-}
-
-template <typename Ratio>
-int64_t ToInt64(Duration d, Ratio) {
-  // Note: This may be used on MSVC, which may have a system_clock period of
-  // std::ratio<1, 10 * 1000 * 1000>
-  return ToInt64Seconds(d * Ratio::den / Ratio::num);
-}
-// Fastpath implementations for the 6 common duration units.
-inline int64_t ToInt64(Duration d, std::nano) {
-  return ToInt64Nanoseconds(d);
-}
-inline int64_t ToInt64(Duration d, std::micro) {
-  return ToInt64Microseconds(d);
-}
-inline int64_t ToInt64(Duration d, std::milli) {
-  return ToInt64Milliseconds(d);
-}
-inline int64_t ToInt64(Duration d, std::ratio<1>) {
-  return ToInt64Seconds(d);
-}
-inline int64_t ToInt64(Duration d, std::ratio<60>) {
-  return ToInt64Minutes(d);
-}
-inline int64_t ToInt64(Duration d, std::ratio<3600>) {
-  return ToInt64Hours(d);
-}
-
-// Converts an absl::Duration to a chrono duration of type T.
-template <typename T>
-T ToChronoDuration(Duration d) {
-  using Rep = typename T::rep;
-  using Period = typename T::period;
-  static_assert(IsValidRep64<Rep>(0), "duration::rep is invalid");
-  if (time_internal::IsInfiniteDuration(d))
-    return d < ZeroDuration() ? (T::min)() : (T::max)();
-  const auto v = ToInt64(d, Period{});
-  if (v > (std::numeric_limits<Rep>::max)()) return (T::max)();
-  if (v < (std::numeric_limits<Rep>::min)()) return (T::min)();
-  return T{v};
-}
-
-}  // namespace time_internal
-
-constexpr Duration Nanoseconds(int64_t n) {
-  return time_internal::FromInt64(n, std::nano{});
-}
-constexpr Duration Microseconds(int64_t n) {
-  return time_internal::FromInt64(n, std::micro{});
-}
-constexpr Duration Milliseconds(int64_t n) {
-  return time_internal::FromInt64(n, std::milli{});
-}
-constexpr Duration Seconds(int64_t n) {
-  return time_internal::FromInt64(n, std::ratio<1>{});
-}
-constexpr Duration Minutes(int64_t n) {
-  return time_internal::FromInt64(n, std::ratio<60>{});
-}
-constexpr Duration Hours(int64_t n) {
-  return time_internal::FromInt64(n, std::ratio<3600>{});
-}
-
-constexpr bool operator<(Duration lhs, Duration rhs) {
-  return time_internal::GetRepHi(lhs) != time_internal::GetRepHi(rhs)
-             ? time_internal::GetRepHi(lhs) < time_internal::GetRepHi(rhs)
-         : time_internal::GetRepHi(lhs) == (std::numeric_limits<int64_t>::min)()
-             ? time_internal::GetRepLo(lhs) + 1 <
-                   time_internal::GetRepLo(rhs) + 1
-             : time_internal::GetRepLo(lhs) < time_internal::GetRepLo(rhs);
-}
-
-constexpr bool operator==(Duration lhs, Duration rhs) {
-  return time_internal::GetRepHi(lhs) == time_internal::GetRepHi(rhs) &&
-         time_internal::GetRepLo(lhs) == time_internal::GetRepLo(rhs);
-}
-
-constexpr Duration operator-(Duration d) {
-  // This is a little interesting because of the special cases.
-  //
-  // If rep_lo_ is zero, we have it easy; it's safe to negate rep_hi_, we're
-  // dealing with an integral number of seconds, and the only special case is
-  // the maximum negative finite duration, which can't be negated.
-  //
-  // Infinities stay infinite, and just change direction.
-  //
-  // Finally we're in the case where rep_lo_ is non-zero, and we can borrow
-  // a second's worth of ticks and avoid overflow (as negating int64_t-min + 1
-  // is safe).
-  return time_internal::GetRepLo(d) == 0
-             ? time_internal::GetRepHi(d) ==
-                       (std::numeric_limits<int64_t>::min)()
-                   ? InfiniteDuration()
-                   : time_internal::MakeDuration(-time_internal::GetRepHi(d))
-             : time_internal::IsInfiniteDuration(d)
-                   ? time_internal::OppositeInfinity(d)
-                   : time_internal::MakeDuration(
-                         time_internal::NegateAndSubtractOne(
-                             time_internal::GetRepHi(d)),
-                         time_internal::kTicksPerSecond -
-                             time_internal::GetRepLo(d));
-}
-
-constexpr Duration InfiniteDuration() {
-  return time_internal::MakeDuration((std::numeric_limits<int64_t>::max)(),
-                                     ~0U);
-}
-
-constexpr Duration FromChrono(const std::chrono::nanoseconds& d) {
-  return time_internal::FromChrono(d);
-}
-constexpr Duration FromChrono(const std::chrono::microseconds& d) {
-  return time_internal::FromChrono(d);
-}
-constexpr Duration FromChrono(const std::chrono::milliseconds& d) {
-  return time_internal::FromChrono(d);
-}
-constexpr Duration FromChrono(const std::chrono::seconds& d) {
-  return time_internal::FromChrono(d);
-}
-constexpr Duration FromChrono(const std::chrono::minutes& d) {
-  return time_internal::FromChrono(d);
-}
-constexpr Duration FromChrono(const std::chrono::hours& d) {
-  return time_internal::FromChrono(d);
-}
-
-constexpr Time FromUnixNanos(int64_t ns) {
-  return time_internal::FromUnixDuration(Nanoseconds(ns));
-}
-
-constexpr Time FromUnixMicros(int64_t us) {
-  return time_internal::FromUnixDuration(Microseconds(us));
-}
-
-constexpr Time FromUnixMillis(int64_t ms) {
-  return time_internal::FromUnixDuration(Milliseconds(ms));
-}
-
-constexpr Time FromUnixSeconds(int64_t s) {
-  return time_internal::FromUnixDuration(Seconds(s));
-}
-
-constexpr Time FromTimeT(time_t t) {
-  return time_internal::FromUnixDuration(Seconds(t));
-}
-
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#endif  // ABSL_TIME_TIME_H_