// Copyright 2016 Google Inc. All Rights Reserved.
//
// 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.
// A library for translating between absolute times (represented by
// std::chrono::time_points of the std::chrono::system_clock) and civil
// times (represented by cctz::civil_second) using the rules defined by
// a time zone (cctz::time_zone).
#ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_
#define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_
#include <chrono>
#include <cstdint>
#include <string>
#include <utility>
#include "absl/base/config.h"
#include "absl/time/internal/cctz/include/cctz/civil_time.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace time_internal {
namespace cctz {
// Convenience aliases. Not intended as public API points.
template <typename D>
using time_point = std::chrono::time_point<std::chrono::system_clock, D>;
using seconds = std::chrono::duration<std::int_fast64_t>;
using sys_seconds = seconds; // Deprecated. Use cctz::seconds instead.
namespace detail {
template <typename D>
inline std::pair<time_point<seconds>, D> split_seconds(
const time_point<D>& tp) {
auto sec = std::chrono::time_point_cast<seconds>(tp);
auto sub = tp - sec;
if (sub.count() < 0) {
sec -= seconds(1);
sub += seconds(1);
}
return {sec, std::chrono::duration_cast<D>(sub)};
}
inline std::pair<time_point<seconds>, seconds> split_seconds(
const time_point<seconds>& tp) {
return {tp, seconds::zero()};
}
} // namespace detail
// cctz::time_zone is an opaque, small, value-type class representing a
// geo-political region within which particular rules are used for mapping
// between absolute and civil times. Time zones are named using the TZ
// identifiers from the IANA Time Zone Database, such as "America/Los_Angeles"
// or "Australia/Sydney". Time zones are created from factory functions such
// as load_time_zone(). Note: strings like "PST" and "EDT" are not valid TZ
// identifiers.
//
// Example:
// cctz::time_zone utc = cctz::utc_time_zone();
// cctz::time_zone pst = cctz::fixed_time_zone(std::chrono::hours(-8));
// cctz::time_zone loc = cctz::local_time_zone();
// cctz::time_zone lax;
// if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... }
//
// See also:
// - http://www.iana.org/time-zones
// - https://en.wikipedia.org/wiki/Zoneinfo
class time_zone {
public:
time_zone() : time_zone(nullptr) {} // Equivalent to UTC
time_zone(const time_zone&) = default;
time_zone& operator=(const time_zone&) = default;
std::string name() const;
// An absolute_lookup represents the civil time (cctz::civil_second) within
// this time_zone at the given absolute time (time_point). There are
// additionally a few other fields that may be useful when working with
// older APIs, such as std::tm.
//
// Example:
// const cctz::time_zone tz = ...
// const auto tp = std::chrono::system_clock::now();
// const cctz::time_zone::absolute_lookup al = tz.lookup(tp);
struct absolute_lookup {
civil_second cs;
// 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 cctz::format().
int offset; // civil seconds east of UTC
bool is_dst; // is offset non-standard?
const char* abbr; // time-zone abbreviation (e.g., "PST")
};
absolute_lookup lookup(const time_point<seconds>& tp) const;
template <typename D>
absolute_lookup lookup(const time_point<D>& tp) const {
return lookup(detail::split_seconds(tp).first);
}
// A civil_lookup represents the absolute time(s) (time_point) that
// correspond to the given civil time (cctz::civil_second) within this
// time_zone. Usually the given civil time represents a unique instant
// in time, in which case the conversion is unambiguous. However,
// within this time zone, the given civil time may be skipped (e.g.,
// during a positive UTC offset shift), or repeated (e.g., during a
// negative UTC offset shift). To account for these possibilities,
// civil_lookup is richer than just a single time_point.
//
// In all cases the civil_lookup::kind enum will indicate the nature
// of the given civil-time argument, and the pre, trans, and post
// members will give the absolute time answers using the pre-transition
// offset, the transition point itself, and the post-transition offset,
// respectively (all three times are equal if kind == UNIQUE). If any
// of these three absolute times is outside the representable range of a
// time_point<seconds> the field is set to its maximum/minimum value.
//
// Example:
// cctz::time_zone lax;
// if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... }
//
// // A unique civil time.
// auto jan01 = lax.lookup(cctz::civil_second(2011, 1, 1, 0, 0, 0));
// // jan01.kind == cctz::time_zone::civil_lookup::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.
// auto mar13 = lax.lookup(cctz::civil_second(2011, 3, 13, 2, 15, 0));
// // mar13.kind == cctz::time_zone::civil_lookup::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.
// auto nov06 = lax.lookup(cctz::civil_second(2011, 11, 6, 1, 15, 0));
// // nov06.kind == cctz::time_zone::civil_lookup::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
struct civil_lookup {
enum civil_kind {
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_point<seconds> pre; // uses the pre-transition offset
time_point<seconds> trans; // instant of civil-offset change
time_point<seconds> post; // uses the post-transition offset
};
civil_lookup lookup(const civil_second& cs) const;
// Finds the time of the next/previous offset change in this time zone.
//
// By definition, next_transition(tp, &trans) returns false when tp has
// its maximum value, and prev_transition(tp, &trans) returns false
// when tp has its minimum value. If the zone has no transitions, the
// result will also be false no matter what the argument.
//
// Otherwise, when tp has its minimum value, next_transition(tp, &trans)
// returns true and sets trans to the first recorded transition. Chains
// of calls to next_transition()/prev_transition() will eventually return
// false, but it is unspecified exactly when next_transition(tp, &trans)
// jumps to false, or what time is set by prev_transition(tp, &trans) for
// a very distant tp.
//
// Note: Enumeration of time-zone transitions is for informational purposes
// only. Modern time-related code should not care about when offset changes
// occur.
//
// Example:
// cctz::time_zone nyc;
// if (!cctz::load_time_zone("America/New_York", &nyc)) { ... }
// const auto now = std::chrono::system_clock::now();
// auto tp = cctz::time_point<cctz::seconds>::min();
// cctz::time_zone::civil_transition trans;
// while (tp <= now && nyc.next_transition(tp, &trans)) {
// // transition: trans.from -> trans.to
// tp = nyc.lookup(trans.to).trans;
// }
struct civil_transition {
civil_second from; // the civil time we jump from
civil_second to; // the civil time we jump to
};
bool next_transition(const time_point<seconds>& tp,
civil_transition* trans) const;
template <typename D>
bool next_transition(const time_point<D>& tp, civil_transition* trans) const {
return next_transition(detail::split_seconds(tp).first, trans);
}
bool prev_transition(const time_point<seconds>& tp,
civil_transition* trans) const;
template <typename D>
bool prev_transition(const time_point<D>& tp, civil_transition* trans) const {
return prev_transition(detail::split_seconds(tp).first, trans);
}
// version() and description() provide additional information about the
// time zone. The content of each of the returned strings is unspecified,
// however, when the IANA Time Zone Database is the underlying data source
// the version() string will be in the familar form (e.g, "2018e") or
// empty when unavailable.
//
// Note: These functions are for informational or testing purposes only.
std::string version() const; // empty when unknown
std::string description() const;
// Relational operators.
friend bool operator==(time_zone lhs, time_zone rhs) {
return &lhs.effective_impl() == &rhs.effective_impl();
}
friend bool operator!=(time_zone lhs, time_zone rhs) { return !(lhs == rhs); }
template <typename H>
friend H AbslHashValue(H h, time_zone tz) {
return H::combine(std::move(h), &tz.effective_impl());
}
class Impl;
private:
explicit time_zone(const Impl* impl) : impl_(impl) {}
const Impl& effective_impl() const; // handles implicit UTC
const Impl* impl_;
};
// Loads the named time zone. May perform I/O on the initial load.
// If the name is invalid, or some other kind of error occurs, returns
// false and "*tz" is set to the UTC time zone.
bool load_time_zone(const std::string& name, time_zone* tz);
// Returns a time_zone representing UTC. Cannot fail.
time_zone utc_time_zone();
// Returns a time zone 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., zero offset) instead.
time_zone fixed_time_zone(const seconds& offset);
// Returns a time zone representing the local time zone. Falls back to UTC.
// Note: local_time_zone.name() may only be something like "localtime".
time_zone local_time_zone();
// Returns the civil time (cctz::civil_second) within the given time zone at
// the given absolute time (time_point). Since the additional fields provided
// by the time_zone::absolute_lookup struct should rarely be needed in modern
// code, this convert() function is simpler and should be preferred.
template <typename D>
inline civil_second convert(const time_point<D>& tp, const time_zone& tz) {
return tz.lookup(tp).cs;
}
// Returns the absolute time (time_point) that corresponds to the given civil
// time within the given time zone. If the civil time is not unique (i.e., if
// it was either repeated or non-existent), then the returned time_point is
// the best estimate that preserves relative order. That is, this function
// guarantees that if cs1 < cs2, then convert(cs1, tz) <= convert(cs2, tz).
inline time_point<seconds> convert(const civil_second& cs,
const time_zone& tz) {
const time_zone::civil_lookup cl = tz.lookup(cs);
if (cl.kind == time_zone::civil_lookup::SKIPPED) return cl.trans;
return cl.pre;
}
namespace detail {
using femtoseconds = std::chrono::duration<std::int_fast64_t, std::femto>;
std::string format(const std::string&, const time_point<seconds>&,
const femtoseconds&, const time_zone&);
bool parse(const std::string&, const std::string&, const time_zone&,
time_point<seconds>*, femtoseconds*, std::string* err = nullptr);
} // namespace detail
// Formats the given time_point in the given cctz::time_zone 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.
//
// Tip: Format strings should include the UTC offset (e.g., %z, %Ez, or %E*z)
// so that the resulting string uniquely identifies an absolute time.
//
// Example:
// cctz::time_zone lax;
// if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... }
// auto tp = cctz::convert(cctz::civil_second(2013, 1, 2, 3, 4, 5), lax);
// std::string f = cctz::format("%H:%M:%S", tp, lax); // "03:04:05"
// f = cctz::format("%H:%M:%E3S", tp, lax); // "03:04:05.000"
template <typename D>
inline std::string format(const std::string& fmt, const time_point<D>& tp,
const time_zone& tz) {
const auto p = detail::split_seconds(tp);
const auto n = std::chrono::duration_cast<detail::femtoseconds>(p.second);
return detail::format(fmt, p.first, n, tz);
}
// Parses an input string according to the provided format string and
// returns the corresponding time_point. Uses strftime()-like formatting
// options, with the same extensions as cctz::format(), 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 a time_point
// that represents "1970-01-01 15:45:00.0 +0000".
//
// Note that parse() returns time instants, so it makes most sense to parse
// fully-specified date/time strings that include a UTC offset (%z, %Ez, or
// %E*z).
//
// Note also that parse() 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 cctz::civil_second() would do. For example, it
// is an error to parse the date "Oct 32, 2013" because 32 is out of range.
//
// A 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.
//
// Example:
// const cctz::time_zone tz = ...
// std::chrono::system_clock::time_point tp;
// if (cctz::parse("%Y-%m-%d", "2015-10-09", tz, &tp)) {
// ...
// }
template <typename D>
inline bool parse(const std::string& fmt, const std::string& input,
const time_zone& tz, time_point<D>* tpp) {
time_point<seconds> sec;
detail::femtoseconds fs;
const bool b = detail::parse(fmt, input, tz, &sec, &fs);
if (b) {
// TODO: Return false if unrepresentable as a time_point<D>.
*tpp = std::chrono::time_point_cast<D>(sec);
*tpp += std::chrono::duration_cast<D>(fs);
}
return b;
}
} // namespace cctz
} // namespace time_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_
