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Diffstat (limited to 'absl/time/internal/cctz/src/time_zone_info.cc')
| -rw-r--r-- | absl/time/internal/cctz/src/time_zone_info.cc | 956 |
1 files changed, 956 insertions, 0 deletions
diff --git a/absl/time/internal/cctz/src/time_zone_info.cc b/absl/time/internal/cctz/src/time_zone_info.cc new file mode 100644 index 000000000000..20bba28b363b --- /dev/null +++ b/absl/time/internal/cctz/src/time_zone_info.cc @@ -0,0 +1,956 @@ +// 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 +// +// http://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. + +// This file implements the TimeZoneIf interface using the "zoneinfo" +// data provided by the IANA Time Zone Database (i.e., the only real game +// in town). +// +// TimeZoneInfo represents the history of UTC-offset changes within a time +// zone. Most changes are due to daylight-saving rules, but occasionally +// shifts are made to the time-zone's base offset. The database only attempts +// to be definitive for times since 1970, so be wary of local-time conversions +// before that. Also, rule and zone-boundary changes are made at the whim +// of governments, so the conversion of future times needs to be taken with +// a grain of salt. +// +// For more information see tzfile(5), http://www.iana.org/time-zones, or +// http://en.wikipedia.org/wiki/Zoneinfo. +// +// Note that we assume the proleptic Gregorian calendar and 60-second +// minutes throughout. + +#include "time_zone_info.h" + +#include <algorithm> +#include <cassert> +#include <chrono> +#include <cstdint> +#include <cstdio> +#include <cstdlib> +#include <cstring> +#include <functional> +#include <iostream> +#include <memory> +#include <sstream> +#include <string> + +#include "absl/time/internal/cctz/include/cctz/civil_time.h" +#include "time_zone_fixed.h" +#include "time_zone_posix.h" + +namespace absl { +namespace time_internal { +namespace cctz { + +namespace { + +inline bool IsLeap(year_t year) { + return (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0); +} + +// The number of days in non-leap and leap years respectively. +const std::int_least32_t kDaysPerYear[2] = {365, 366}; + +// The day offsets of the beginning of each (1-based) month in non-leap and +// leap years respectively (e.g., 335 days before December in a leap year). +const std::int_least16_t kMonthOffsets[2][1 + 12 + 1] = { + {-1, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365}, + {-1, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}, +}; + +// We reject leap-second encoded zoneinfo and so assume 60-second minutes. +const std::int_least32_t kSecsPerDay = 24 * 60 * 60; + +// 400-year chunks always have 146097 days (20871 weeks). +const std::int_least64_t kSecsPer400Years = 146097LL * kSecsPerDay; + +// Like kDaysPerYear[] but scaled up by a factor of kSecsPerDay. +const std::int_least32_t kSecsPerYear[2] = { + 365 * kSecsPerDay, + 366 * kSecsPerDay, +}; + +// Single-byte, unsigned numeric values are encoded directly. +inline std::uint_fast8_t Decode8(const char* cp) { + return static_cast<std::uint_fast8_t>(*cp) & 0xff; +} + +// Multi-byte, numeric values are encoded using a MSB first, +// twos-complement representation. These helpers decode, from +// the given address, 4-byte and 8-byte values respectively. +// Note: If int_fastXX_t == intXX_t and this machine is not +// twos complement, then there will be at least one input value +// we cannot represent. +std::int_fast32_t Decode32(const char* cp) { + std::uint_fast32_t v = 0; + for (int i = 0; i != (32 / 8); ++i) v = (v << 8) | Decode8(cp++); + const std::int_fast32_t s32max = 0x7fffffff; + const auto s32maxU = static_cast<std::uint_fast32_t>(s32max); + if (v <= s32maxU) return static_cast<std::int_fast32_t>(v); + return static_cast<std::int_fast32_t>(v - s32maxU - 1) - s32max - 1; +} + +std::int_fast64_t Decode64(const char* cp) { + std::uint_fast64_t v = 0; + for (int i = 0; i != (64 / 8); ++i) v = (v << 8) | Decode8(cp++); + const std::int_fast64_t s64max = 0x7fffffffffffffff; + const auto s64maxU = static_cast<std::uint_fast64_t>(s64max); + if (v <= s64maxU) return static_cast<std::int_fast64_t>(v); + return static_cast<std::int_fast64_t>(v - s64maxU - 1) - s64max - 1; +} + +// Generate a year-relative offset for a PosixTransition. +std::int_fast64_t TransOffset(bool leap_year, int jan1_weekday, + const PosixTransition& pt) { + std::int_fast64_t days = 0; + switch (pt.date.fmt) { + case PosixTransition::J: { + days = pt.date.j.day; + if (!leap_year || days < kMonthOffsets[1][3]) days -= 1; + break; + } + case PosixTransition::N: { + days = pt.date.n.day; + break; + } + case PosixTransition::M: { + const bool last_week = (pt.date.m.week == 5); + days = kMonthOffsets[leap_year][pt.date.m.month + last_week]; + const std::int_fast64_t weekday = (jan1_weekday + days) % 7; + if (last_week) { + days -= (weekday + 7 - 1 - pt.date.m.weekday) % 7 + 1; + } else { + days += (pt.date.m.weekday + 7 - weekday) % 7; + days += (pt.date.m.week - 1) * 7; + } + break; + } + } + return (days * kSecsPerDay) + pt.time.offset; +} + +inline time_zone::civil_lookup MakeUnique(const time_point<sys_seconds>& tp) { + time_zone::civil_lookup cl; + cl.kind = time_zone::civil_lookup::UNIQUE; + cl.pre = cl.trans = cl.post = tp; + return cl; +} + +inline time_zone::civil_lookup MakeUnique(std::int_fast64_t unix_time) { + return MakeUnique(FromUnixSeconds(unix_time)); +} + +inline time_zone::civil_lookup MakeSkipped(const Transition& tr, + const civil_second& cs) { + time_zone::civil_lookup cl; + cl.kind = time_zone::civil_lookup::SKIPPED; + cl.pre = FromUnixSeconds(tr.unix_time - 1 + (cs - tr.prev_civil_sec)); + cl.trans = FromUnixSeconds(tr.unix_time); + cl.post = FromUnixSeconds(tr.unix_time - (tr.civil_sec - cs)); + return cl; +} + +inline time_zone::civil_lookup MakeRepeated(const Transition& tr, + const civil_second& cs) { + time_zone::civil_lookup cl; + cl.kind = time_zone::civil_lookup::REPEATED; + cl.pre = FromUnixSeconds(tr.unix_time - 1 - (tr.prev_civil_sec - cs)); + cl.trans = FromUnixSeconds(tr.unix_time); + cl.post = FromUnixSeconds(tr.unix_time + (cs - tr.civil_sec)); + return cl; +} + +inline civil_second YearShift(const civil_second& cs, year_t shift) { + return civil_second(cs.year() + shift, cs.month(), cs.day(), + cs.hour(), cs.minute(), cs.second()); +} + +} // namespace + +// What (no leap-seconds) UTC+seconds zoneinfo would look like. +bool TimeZoneInfo::ResetToBuiltinUTC(const sys_seconds& offset) { + transition_types_.resize(1); + TransitionType& tt(transition_types_.back()); + tt.utc_offset = static_cast<std::int_least32_t>(offset.count()); + tt.is_dst = false; + tt.abbr_index = 0; + + // We temporarily add some redundant, contemporary (2012 through 2021) + // transitions for performance reasons. See TimeZoneInfo::LocalTime(). + // TODO: Fix the performance issue and remove the extra transitions. + transitions_.clear(); + transitions_.reserve(12); + for (const std::int_fast64_t unix_time : { + -(1LL << 59), // BIG_BANG + 1325376000LL, // 2012-01-01T00:00:00+00:00 + 1356998400LL, // 2013-01-01T00:00:00+00:00 + 1388534400LL, // 2014-01-01T00:00:00+00:00 + 1420070400LL, // 2015-01-01T00:00:00+00:00 + 1451606400LL, // 2016-01-01T00:00:00+00:00 + 1483228800LL, // 2017-01-01T00:00:00+00:00 + 1514764800LL, // 2018-01-01T00:00:00+00:00 + 1546300800LL, // 2019-01-01T00:00:00+00:00 + 1577836800LL, // 2020-01-01T00:00:00+00:00 + 1609459200LL, // 2021-01-01T00:00:00+00:00 + 2147483647LL, // 2^31 - 1 + }) { + Transition& tr(*transitions_.emplace(transitions_.end())); + tr.unix_time = unix_time; + tr.type_index = 0; + tr.civil_sec = LocalTime(tr.unix_time, tt).cs; + tr.prev_civil_sec = tr.civil_sec - 1; + } + + default_transition_type_ = 0; + abbreviations_ = FixedOffsetToAbbr(offset); + abbreviations_.append(1, '\0'); // add NUL + future_spec_.clear(); // never needed for a fixed-offset zone + extended_ = false; + + tt.civil_max = LocalTime(sys_seconds::max().count(), tt).cs; + tt.civil_min = LocalTime(sys_seconds::min().count(), tt).cs; + + transitions_.shrink_to_fit(); + return true; +} + +// Builds the in-memory header using the raw bytes from the file. +bool TimeZoneInfo::Header::Build(const tzhead& tzh) { + std::int_fast32_t v; + if ((v = Decode32(tzh.tzh_timecnt)) < 0) return false; + timecnt = static_cast<std::size_t>(v); + if ((v = Decode32(tzh.tzh_typecnt)) < 0) return false; + typecnt = static_cast<std::size_t>(v); + if ((v = Decode32(tzh.tzh_charcnt)) < 0) return false; + charcnt = static_cast<std::size_t>(v); + if ((v = Decode32(tzh.tzh_leapcnt)) < 0) return false; + leapcnt = static_cast<std::size_t>(v); + if ((v = Decode32(tzh.tzh_ttisstdcnt)) < 0) return false; + ttisstdcnt = static_cast<std::size_t>(v); + if ((v = Decode32(tzh.tzh_ttisgmtcnt)) < 0) return false; + ttisgmtcnt = static_cast<std::size_t>(v); + return true; +} + +// How many bytes of data are associated with this header. The result +// depends upon whether this is a section with 4-byte or 8-byte times. +std::size_t TimeZoneInfo::Header::DataLength(std::size_t time_len) const { + std::size_t len = 0; + len += (time_len + 1) * timecnt; // unix_time + type_index + len += (4 + 1 + 1) * typecnt; // utc_offset + is_dst + abbr_index + len += 1 * charcnt; // abbreviations + len += (time_len + 4) * leapcnt; // leap-time + TAI-UTC + len += 1 * ttisstdcnt; // UTC/local indicators + len += 1 * ttisgmtcnt; // standard/wall indicators + return len; +} + +// Check that the TransitionType has the expected offset/is_dst/abbreviation. +void TimeZoneInfo::CheckTransition(const std::string& name, + const TransitionType& tt, + std::int_fast32_t offset, bool is_dst, + const std::string& abbr) const { + if (tt.utc_offset != offset || tt.is_dst != is_dst || + &abbreviations_[tt.abbr_index] != abbr) { + std::clog << name << ": Transition" + << " offset=" << tt.utc_offset << "/" + << (tt.is_dst ? "DST" : "STD") + << "/abbr=" << &abbreviations_[tt.abbr_index] + << " does not match POSIX spec '" << future_spec_ << "'\n"; + } +} + +// zic(8) can generate no-op transitions when a zone changes rules at an +// instant when there is actually no discontinuity. So we check whether +// two transitions have equivalent types (same offset/is_dst/abbr). +bool TimeZoneInfo::EquivTransitions(std::uint_fast8_t tt1_index, + std::uint_fast8_t tt2_index) const { + if (tt1_index == tt2_index) return true; + const TransitionType& tt1(transition_types_[tt1_index]); + const TransitionType& tt2(transition_types_[tt2_index]); + if (tt1.is_dst != tt2.is_dst) return false; + if (tt1.utc_offset != tt2.utc_offset) return false; + if (tt1.abbr_index != tt2.abbr_index) return false; + return true; +} + +// Use the POSIX-TZ-environment-variable-style std::string to handle times +// in years after the last transition stored in the zoneinfo data. +void TimeZoneInfo::ExtendTransitions(const std::string& name, + const Header& hdr) { + extended_ = false; + bool extending = !future_spec_.empty(); + + PosixTimeZone posix; + if (extending && !ParsePosixSpec(future_spec_, &posix)) { + std::clog << name << ": Failed to parse '" << future_spec_ << "'\n"; + extending = false; + } + + if (extending && posix.dst_abbr.empty()) { // std only + // The future specification should match the last/default transition, + // and that means that handling the future will fall out naturally. + std::uint_fast8_t index = default_transition_type_; + if (hdr.timecnt != 0) index = transitions_[hdr.timecnt - 1].type_index; + const TransitionType& tt(transition_types_[index]); + CheckTransition(name, tt, posix.std_offset, false, posix.std_abbr); + extending = false; + } + + if (extending && hdr.timecnt < 2) { + std::clog << name << ": Too few transitions for POSIX spec\n"; + extending = false; + } + + if (!extending) { + // Ensure that there is always a transition in the second half of the + // time line (the BIG_BANG transition is in the first half) so that the + // signed difference between a civil_second and the civil_second of its + // previous transition is always representable, without overflow. + const Transition& last(transitions_.back()); + if (last.unix_time < 0) { + const std::uint_fast8_t type_index = last.type_index; + Transition& tr(*transitions_.emplace(transitions_.end())); + tr.unix_time = 2147483647; // 2038-01-19T03:14:07+00:00 + tr.type_index = type_index; + } + return; // last transition wins + } + + // Extend the transitions for an additional 400 years using the + // future specification. Years beyond those can be handled by + // mapping back to a cycle-equivalent year within that range. + // zic(8) should probably do this so that we don't have to. + // TODO: Reduce the extension by the number of compatible + // transitions already in place. + transitions_.reserve(hdr.timecnt + 400 * 2 + 1); + transitions_.resize(hdr.timecnt + 400 * 2); + extended_ = true; + + // The future specification should match the last two transitions, + // and those transitions should have different is_dst flags. Note + // that nothing says the UTC offset used by the is_dst transition + // must be greater than that used by the !is_dst transition. (See + // Europe/Dublin, for example.) + const Transition* tr0 = &transitions_[hdr.timecnt - 1]; + const Transition* tr1 = &transitions_[hdr.timecnt - 2]; + const TransitionType* tt0 = &transition_types_[tr0->type_index]; + const TransitionType* tt1 = &transition_types_[tr1->type_index]; + const TransitionType& dst(tt0->is_dst ? *tt0 : *tt1); + const TransitionType& std(tt0->is_dst ? *tt1 : *tt0); + CheckTransition(name, dst, posix.dst_offset, true, posix.dst_abbr); + CheckTransition(name, std, posix.std_offset, false, posix.std_abbr); + + // Add the transitions to tr1 and back to tr0 for each extra year. + last_year_ = LocalTime(tr0->unix_time, *tt0).cs.year(); + bool leap_year = IsLeap(last_year_); + const civil_day jan1(last_year_, 1, 1); + std::int_fast64_t jan1_time = civil_second(jan1) - civil_second(); + int jan1_weekday = (static_cast<int>(get_weekday(jan1)) + 1) % 7; + Transition* tr = &transitions_[hdr.timecnt]; // next trans to fill + if (LocalTime(tr1->unix_time, *tt1).cs.year() != last_year_) { + // Add a single extra transition to align to a calendar year. + transitions_.resize(transitions_.size() + 1); + assert(tr == &transitions_[hdr.timecnt]); // no reallocation + const PosixTransition& pt1(tt0->is_dst ? posix.dst_end : posix.dst_start); + std::int_fast64_t tr1_offset = TransOffset(leap_year, jan1_weekday, pt1); + tr->unix_time = jan1_time + tr1_offset - tt0->utc_offset; + tr++->type_index = tr1->type_index; + tr0 = &transitions_[hdr.timecnt]; + tr1 = &transitions_[hdr.timecnt - 1]; + tt0 = &transition_types_[tr0->type_index]; + tt1 = &transition_types_[tr1->type_index]; + } + const PosixTransition& pt1(tt0->is_dst ? posix.dst_end : posix.dst_start); + const PosixTransition& pt0(tt0->is_dst ? posix.dst_start : posix.dst_end); + for (const year_t limit = last_year_ + 400; last_year_ < limit;) { + last_year_ += 1; // an additional year of generated transitions + jan1_time += kSecsPerYear[leap_year]; + jan1_weekday = (jan1_weekday + kDaysPerYear[leap_year]) % 7; + leap_year = !leap_year && IsLeap(last_year_); + std::int_fast64_t tr1_offset = TransOffset(leap_year, jan1_weekday, pt1); + tr->unix_time = jan1_time + tr1_offset - tt0->utc_offset; + tr++->type_index = tr1->type_index; + std::int_fast64_t tr0_offset = TransOffset(leap_year, jan1_weekday, pt0); + tr->unix_time = jan1_time + tr0_offset - tt1->utc_offset; + tr++->type_index = tr0->type_index; + } + assert(tr == &transitions_[0] + transitions_.size()); +} + +bool TimeZoneInfo::Load(const std::string& name, ZoneInfoSource* zip) { + // Read and validate the header. + tzhead tzh; + if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) + return false; + if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0) + return false; + Header hdr; + if (!hdr.Build(tzh)) + return false; + std::size_t time_len = 4; + if (tzh.tzh_version[0] != '\0') { + // Skip the 4-byte data. + if (zip->Skip(hdr.DataLength(time_len)) != 0) + return false; + // Read and validate the header for the 8-byte data. + if (zip->Read(&tzh, sizeof(tzh)) != sizeof(tzh)) + return false; + if (strncmp(tzh.tzh_magic, TZ_MAGIC, sizeof(tzh.tzh_magic)) != 0) + return false; + if (tzh.tzh_version[0] == '\0') + return false; + if (!hdr.Build(tzh)) + return false; + time_len = 8; + } + if (hdr.typecnt == 0) + return false; + if (hdr.leapcnt != 0) { + // This code assumes 60-second minutes so we do not want + // the leap-second encoded zoneinfo. We could reverse the + // compensation, but the "right" encoding is rarely used + // so currently we simply reject such data. + return false; + } + if (hdr.ttisstdcnt != 0 && hdr.ttisstdcnt != hdr.typecnt) + return false; + if (hdr.ttisgmtcnt != 0 && hdr.ttisgmtcnt != hdr.typecnt) + return false; + + // Read the data into a local buffer. + std::size_t len = hdr.DataLength(time_len); + std::vector<char> tbuf(len); + if (zip->Read(tbuf.data(), len) != len) + return false; + const char* bp = tbuf.data(); + + // Decode and validate the transitions. + transitions_.reserve(hdr.timecnt + 2); // We might add a couple. + transitions_.resize(hdr.timecnt); + for (std::size_t i = 0; i != hdr.timecnt; ++i) { + transitions_[i].unix_time = (time_len == 4) ? Decode32(bp) : Decode64(bp); + bp += time_len; + if (i != 0) { + // Check that the transitions are ordered by time (as zic guarantees). + if (!Transition::ByUnixTime()(transitions_[i - 1], transitions_[i])) + return false; // out of order + } + } + bool seen_type_0 = false; + for (std::size_t i = 0; i != hdr.timecnt; ++i) { + transitions_[i].type_index = Decode8(bp++); + if (transitions_[i].type_index >= hdr.typecnt) + return false; + if (transitions_[i].type_index == 0) + seen_type_0 = true; + } + + // Decode and validate the transition types. + transition_types_.resize(hdr.typecnt); + for (std::size_t i = 0; i != hdr.typecnt; ++i) { + transition_types_[i].utc_offset = + static_cast<std::int_least32_t>(Decode32(bp)); + if (transition_types_[i].utc_offset >= kSecsPerDay || + transition_types_[i].utc_offset <= -kSecsPerDay) + return false; + bp += 4; + transition_types_[i].is_dst = (Decode8(bp++) != 0); + transition_types_[i].abbr_index = Decode8(bp++); + if (transition_types_[i].abbr_index >= hdr.charcnt) + return false; + } + + // Determine the before-first-transition type. + default_transition_type_ = 0; + if (seen_type_0 && hdr.timecnt != 0) { + std::uint_fast8_t index = 0; + if (transition_types_[0].is_dst) { + index = transitions_[0].type_index; + while (index != 0 && transition_types_[index].is_dst) + --index; + } + while (index != hdr.typecnt && transition_types_[index].is_dst) + ++index; + if (index != hdr.typecnt) + default_transition_type_ = index; + } + + // Copy all the abbreviations. + abbreviations_.assign(bp, hdr.charcnt); + bp += hdr.charcnt; + + // Skip the unused portions. We've already dispensed with leap-second + // encoded zoneinfo. The ttisstd/ttisgmt indicators only apply when + // interpreting a POSIX spec that does not include start/end rules, and + // that isn't the case here (see "zic -p"). + bp += (8 + 4) * hdr.leapcnt; // leap-time + TAI-UTC + bp += 1 * hdr.ttisstdcnt; // UTC/local indicators + bp += 1 * hdr.ttisgmtcnt; // standard/wall indicators + assert(bp == tbuf.data() + tbuf.size()); + + future_spec_.clear(); + if (tzh.tzh_version[0] != '\0') { + // Snarf up the NL-enclosed future POSIX spec. Note + // that version '3' files utilize an extended format. + auto get_char = [](ZoneInfoSource* zip) -> int { + unsigned char ch; // all non-EOF results are positive + return (zip->Read(&ch, 1) == 1) ? ch : EOF; + }; + if (get_char(zip) != '\n') + return false; + for (int c = get_char(zip); c != '\n'; c = get_char(zip)) { + if (c == EOF) + return false; + future_spec_.push_back(static_cast<char>(c)); + } + } + + // We don't check for EOF so that we're forwards compatible. + + // Trim redundant transitions. zic may have added these to work around + // differences between the glibc and reference implementations (see + // zic.c:dontmerge) and the Qt library (see zic.c:WORK_AROUND_QTBUG_53071). + // For us, they just get in the way when we do future_spec_ extension. + while (hdr.timecnt > 1) { + if (!EquivTransitions(transitions_[hdr.timecnt - 1].type_index, + transitions_[hdr.timecnt - 2].type_index)) { + break; + } + hdr.timecnt -= 1; + } + transitions_.resize(hdr.timecnt); + + // Ensure that there is always a transition in the first half of the + // time line (the second half is handled in ExtendTransitions()) so that + // the signed difference between a civil_second and the civil_second of + // its previous transition is always representable, without overflow. + // A contemporary zic will usually have already done this for us. + if (transitions_.empty() || transitions_.front().unix_time >= 0) { + Transition& tr(*transitions_.emplace(transitions_.begin())); + tr.unix_time = -(1LL << 59); // see tz/zic.c "BIG_BANG" + tr.type_index = default_transition_type_; + hdr.timecnt += 1; + } + + // Extend the transitions using the future specification. + ExtendTransitions(name, hdr); + + // Compute the local civil time for each transition and the preceding + // second. These will be used for reverse conversions in MakeTime(). + const TransitionType* ttp = &transition_types_[default_transition_type_]; + for (std::size_t i = 0; i != transitions_.size(); ++i) { + Transition& tr(transitions_[i]); + tr.prev_civil_sec = LocalTime(tr.unix_time, *ttp).cs - 1; + ttp = &transition_types_[tr.type_index]; + tr.civil_sec = LocalTime(tr.unix_time, *ttp).cs; + if (i != 0) { + // Check that the transitions are ordered by civil time. Essentially + // this means that an offset change cannot cross another such change. + // No one does this in practice, and we depend on it in MakeTime(). + if (!Transition::ByCivilTime()(transitions_[i - 1], tr)) + return false; // out of order + } + } + + // Compute the maximum/minimum civil times that can be converted to a + // time_point<sys_seconds> for each of the zone's transition types. + for (auto& tt : transition_types_) { + tt.civil_max = LocalTime(sys_seconds::max().count(), tt).cs; + tt.civil_min = LocalTime(sys_seconds::min().count(), tt).cs; + } + + transitions_.shrink_to_fit(); + return true; +} + +namespace { + +// fopen(3) adaptor. +inline FILE* FOpen(const char* path, const char* mode) { +#if defined(_MSC_VER) + FILE* fp; + if (fopen_s(&fp, path, mode) != 0) fp = nullptr; + return fp; +#else + return fopen(path, mode); // TODO: Enable the close-on-exec flag. +#endif +} + +// A stdio(3)-backed implementation of ZoneInfoSource. +class FileZoneInfoSource : public ZoneInfoSource { + public: + static std::unique_ptr<ZoneInfoSource> Open(const std::string& name); + + std::size_t Read(void* ptr, std::size_t size) override { + size = std::min(size, len_); + std::size_t nread = fread(ptr, 1, size, fp_.get()); + len_ -= nread; + return nread; + } + int Skip(std::size_t offset) override { + offset = std::min(offset, len_); + int rc = fseek(fp_.get(), static_cast<long>(offset), SEEK_CUR); + if (rc == 0) len_ -= offset; + return rc; + } + + protected: + explicit FileZoneInfoSource( + FILE* fp, std::size_t len = std::numeric_limits<std::size_t>::max()) + : fp_(fp, fclose), len_(len) {} + + private: + std::unique_ptr<FILE, int(*)(FILE*)> fp_; + std::size_t len_; +}; + +std::unique_ptr<ZoneInfoSource> FileZoneInfoSource::Open( + const std::string& name) { + // Use of the "file:" prefix is intended for testing purposes only. + if (name.compare(0, 5, "file:") == 0) return Open(name.substr(5)); + + // Map the time-zone name to a path name. + std::string path; + if (name.empty() || name[0] != '/') { + const char* tzdir = "/usr/share/zoneinfo"; + char* tzdir_env = nullptr; +#if defined(_MSC_VER) + _dupenv_s(&tzdir_env, nullptr, "TZDIR"); +#else + tzdir_env = std::getenv("TZDIR"); +#endif + if (tzdir_env && *tzdir_env) tzdir = tzdir_env; + path += tzdir; + path += '/'; +#if defined(_MSC_VER) + free(tzdir_env); +#endif + } + path += name; + + // Open the zoneinfo file. + FILE* fp = FOpen(path.c_str(), "rb"); + if (fp == nullptr) return nullptr; + std::size_t length = 0; + if (fseek(fp, 0, SEEK_END) == 0) { + long pos = ftell(fp); + if (pos >= 0) { + length = static_cast<std::size_t>(pos); + } + rewind(fp); + } + return std::unique_ptr<ZoneInfoSource>(new FileZoneInfoSource(fp, length)); +} + +#if defined(__ANDROID__) +class AndroidZoneInfoSource : public FileZoneInfoSource { + public: + static std::unique_ptr<ZoneInfoSource> Open(const std::string& name); + + private: + explicit AndroidZoneInfoSource(FILE* fp, std::size_t len) + : FileZoneInfoSource(fp, len) {} +}; + +std::unique_ptr<ZoneInfoSource> AndroidZoneInfoSource::Open( + const std::string& name) { + // Use of the "file:" prefix is intended for testing purposes only. + if (name.compare(0, 5, "file:") == 0) return Open(name.substr(5)); + + // See Android's libc/tzcode/bionic.cpp for additional information. + for (const char* tzdata : {"/data/misc/zoneinfo/current/tzdata", + "/system/usr/share/zoneinfo/tzdata"}) { + std::unique_ptr<FILE, int (*)(FILE*)> fp(FOpen(tzdata, "rb"), fclose); + if (fp.get() == nullptr) continue; + + char hbuf[24]; // covers header.zonetab_offset too + if (fread(hbuf, 1, sizeof(hbuf), fp.get()) != sizeof(hbuf)) continue; + if (strncmp(hbuf, "tzdata", 6) != 0) continue; + const std::int_fast32_t index_offset = Decode32(hbuf + 12); + const std::int_fast32_t data_offset = Decode32(hbuf + 16); + if (index_offset < 0 || data_offset < index_offset) continue; + if (fseek(fp.get(), static_cast<long>(index_offset), SEEK_SET) != 0) + continue; + + char ebuf[52]; // covers entry.unused too + const std::size_t index_size = + static_cast<std::size_t>(data_offset - index_offset); + const std::size_t zonecnt = index_size / sizeof(ebuf); + if (zonecnt * sizeof(ebuf) != index_size) continue; + for (std::size_t i = 0; i != zonecnt; ++i) { + if (fread(ebuf, 1, sizeof(ebuf), fp.get()) != sizeof(ebuf)) break; + const std::int_fast32_t start = data_offset + Decode32(ebuf + 40); + const std::int_fast32_t length = Decode32(ebuf + 44); + if (start < 0 || length < 0) break; + ebuf[40] = '\0'; // ensure zone name is NUL terminated + if (strcmp(name.c_str(), ebuf) == 0) { + if (fseek(fp.get(), static_cast<long>(start), SEEK_SET) != 0) break; + return std::unique_ptr<ZoneInfoSource>(new AndroidZoneInfoSource( + fp.release(), static_cast<std::size_t>(length))); + } + } + } + return nullptr; +} +#endif + +} // namespace + +bool TimeZoneInfo::Load(const std::string& name) { + // We can ensure that the loading of UTC or any other fixed-offset + // zone never fails because the simple, fixed-offset state can be + // internally generated. Note that this depends on our choice to not + // accept leap-second encoded ("right") zoneinfo. + auto offset = sys_seconds::zero(); + if (FixedOffsetFromName(name, &offset)) { + return ResetToBuiltinUTC(offset); + } + + // Find and use a ZoneInfoSource to load the named zone. + auto zip = cctz_extension::zone_info_source_factory( + name, [](const std::string& name) -> std::unique_ptr<ZoneInfoSource> { + if (auto zip = FileZoneInfoSource::Open(name)) return zip; +#if defined(__ANDROID__) + if (auto zip = AndroidZoneInfoSource::Open(name)) return zip; +#endif + return nullptr; + }); + return zip != nullptr && Load(name, zip.get()); +} + +// BreakTime() translation for a particular transition type. +time_zone::absolute_lookup TimeZoneInfo::LocalTime( + std::int_fast64_t unix_time, const TransitionType& tt) const { + // A civil time in "+offset" looks like (time+offset) in UTC. + // Note: We perform two additions in the civil_second domain to + // sidestep the chance of overflow in (unix_time + tt.utc_offset). + return {(civil_second() + unix_time) + tt.utc_offset, + tt.utc_offset, tt.is_dst, &abbreviations_[tt.abbr_index]}; +} + +// BreakTime() translation for a particular transition. +time_zone::absolute_lookup TimeZoneInfo::LocalTime( + std::int_fast64_t unix_time, const Transition& tr) const { + const TransitionType& tt = transition_types_[tr.type_index]; + // Note: (unix_time - tr.unix_time) will never overflow as we + // have ensured that there is always a "nearby" transition. + return {tr.civil_sec + (unix_time - tr.unix_time), // TODO: Optimize. + tt.utc_offset, tt.is_dst, &abbreviations_[tt.abbr_index]}; +} + +// MakeTime() translation with a conversion-preserving +N * 400-year shift. +time_zone::civil_lookup TimeZoneInfo::TimeLocal(const civil_second& cs, + year_t c4_shift) const { + assert(last_year_ - 400 < cs.year() && cs.year() <= last_year_); + time_zone::civil_lookup cl = MakeTime(cs); + if (c4_shift > sys_seconds::max().count() / kSecsPer400Years) { + cl.pre = cl.trans = cl.post = time_point<sys_seconds>::max(); + } else { + const auto offset = sys_seconds(c4_shift * kSecsPer400Years); + const auto limit = time_point<sys_seconds>::max() - offset; + for (auto* tp : {&cl.pre, &cl.trans, &cl.post}) { + if (*tp > limit) { + *tp = time_point<sys_seconds>::max(); + } else { + *tp += offset; + } + } + } + return cl; +} + +time_zone::absolute_lookup TimeZoneInfo::BreakTime( + const time_point<sys_seconds>& tp) const { + std::int_fast64_t unix_time = ToUnixSeconds(tp); + const std::size_t timecnt = transitions_.size(); + assert(timecnt != 0); // We always add a transition. + + if (unix_time < transitions_[0].unix_time) { + return LocalTime(unix_time, transition_types_[default_transition_type_]); + } + if (unix_time >= transitions_[timecnt - 1].unix_time) { + // After the last transition. If we extended the transitions using + // future_spec_, shift back to a supported year using the 400-year + // cycle of calendaric equivalence and then compensate accordingly. + if (extended_) { + const std::int_fast64_t diff = + unix_time - transitions_[timecnt - 1].unix_time; + const year_t shift = diff / kSecsPer400Years + 1; + const auto d = sys_seconds(shift * kSecsPer400Years); + time_zone::absolute_lookup al = BreakTime(tp - d); + al.cs = YearShift(al.cs, shift * 400); + return al; + } + return LocalTime(unix_time, transitions_[timecnt - 1]); + } + + const std::size_t hint = local_time_hint_.load(std::memory_order_relaxed); + if (0 < hint && hint < timecnt) { + if (transitions_[hint - 1].unix_time <= unix_time) { + if (unix_time < transitions_[hint].unix_time) { + return LocalTime(unix_time, transitions_[hint - 1]); + } + } + } + + const Transition target = {unix_time, 0, civil_second(), civil_second()}; + const Transition* begin = &transitions_[0]; + const Transition* tr = std::upper_bound(begin, begin + timecnt, target, + Transition::ByUnixTime()); + local_time_hint_.store(static_cast<std::size_t>(tr - begin), + std::memory_order_relaxed); + return LocalTime(unix_time, *--tr); +} + +time_zone::civil_lookup TimeZoneInfo::MakeTime(const civil_second& cs) const { + const std::size_t timecnt = transitions_.size(); + assert(timecnt != 0); // We always add a transition. + + // Find the first transition after our target civil time. + const Transition* tr = nullptr; + const Transition* begin = &transitions_[0]; + const Transition* end = begin + timecnt; + if (cs < begin->civil_sec) { + tr = begin; + } else if (cs >= transitions_[timecnt - 1].civil_sec) { + tr = end; + } else { + const std::size_t hint = time_local_hint_.load(std::memory_order_relaxed); + if (0 < hint && hint < timecnt) { + if (transitions_[hint - 1].civil_sec <= cs) { + if (cs < transitions_[hint].civil_sec) { + tr = begin + hint; + } + } + } + if (tr == nullptr) { + const Transition target = {0, 0, cs, civil_second()}; + tr = std::upper_bound(begin, end, target, Transition::ByCivilTime()); + time_local_hint_.store(static_cast<std::size_t>(tr - begin), + std::memory_order_relaxed); + } + } + + if (tr == begin) { + if (tr->prev_civil_sec >= cs) { + // Before first transition, so use the default offset. + const TransitionType& tt(transition_types_[default_transition_type_]); + if (cs < tt.civil_min) return MakeUnique(time_point<sys_seconds>::min()); + return MakeUnique(cs - (civil_second() + tt.utc_offset)); + } + // tr->prev_civil_sec < cs < tr->civil_sec + return MakeSkipped(*tr, cs); + } + + if (tr == end) { + if (cs > (--tr)->prev_civil_sec) { + // After the last transition. If we extended the transitions using + // future_spec_, shift back to a supported year using the 400-year + // cycle of calendaric equivalence and then compensate accordingly. + if (extended_ && cs.year() > last_year_) { + const year_t shift = (cs.year() - last_year_ - 1) / 400 + 1; + return TimeLocal(YearShift(cs, shift * -400), shift); + } + const TransitionType& tt(transition_types_[tr->type_index]); + if (cs > tt.civil_max) return MakeUnique(time_point<sys_seconds>::max()); + return MakeUnique(tr->unix_time + (cs - tr->civil_sec)); + } + // tr->civil_sec <= cs <= tr->prev_civil_sec + return MakeRepeated(*tr, cs); + } + + if (tr->prev_civil_sec < cs) { + // tr->prev_civil_sec < cs < tr->civil_sec + return MakeSkipped(*tr, cs); + } + + if (cs <= (--tr)->prev_civil_sec) { + // tr->civil_sec <= cs <= tr->prev_civil_sec + return MakeRepeated(*tr, cs); + } + + // In between transitions. + return MakeUnique(tr->unix_time + (cs - tr->civil_sec)); +} + +std::string TimeZoneInfo::Description() const { + std::ostringstream oss; + // TODO: It would nice if the zoneinfo data included the zone name. + // TODO: It would nice if the zoneinfo data included the tzdb version. + oss << "#trans=" << transitions_.size(); + oss << " #types=" << transition_types_.size(); + oss << " spec='" << future_spec_ << "'"; + return oss.str(); +} + +bool TimeZoneInfo::NextTransition(time_point<sys_seconds>* tp) const { + if (transitions_.empty()) return false; + const Transition* begin = &transitions_[0]; + const Transition* end = begin + transitions_.size(); + if (begin->unix_time <= -(1LL << 59)) { + // Do not report the BIG_BANG found in recent zoneinfo data as it is + // really a sentinel, not a transition. See tz/zic.c. + ++begin; + } + std::int_fast64_t unix_time = ToUnixSeconds(*tp); + const Transition target = { unix_time }; + const Transition* tr = std::upper_bound(begin, end, target, + Transition::ByUnixTime()); + if (tr != begin) { // skip no-op transitions + for (; tr != end; ++tr) { + if (!EquivTransitions(tr[-1].type_index, tr[0].type_index)) break; + } + } + // When tr == end we return false, ignoring future_spec_. + if (tr == end) return false; + *tp = FromUnixSeconds(tr->unix_time); + return true; +} + +bool TimeZoneInfo::PrevTransition(time_point<sys_seconds>* tp) const { + if (transitions_.empty()) return false; + const Transition* begin = &transitions_[0]; + const Transition* end = begin + transitions_.size(); + if (begin->unix_time <= -(1LL << 59)) { + // Do not report the BIG_BANG found in recent zoneinfo data as it is + // really a sentinel, not a transition. See tz/zic.c. + ++begin; + } + std::int_fast64_t unix_time = ToUnixSeconds(*tp); + if (FromUnixSeconds(unix_time) != *tp) { + if (unix_time == std::numeric_limits<std::int_fast64_t>::max()) { + if (end == begin) return false; // Ignore future_spec_. + *tp = FromUnixSeconds((--end)->unix_time); + return true; + } + unix_time += 1; // ceils + } + const Transition target = { unix_time }; + const Transition* tr = std::lower_bound(begin, end, target, + Transition::ByUnixTime()); + if (tr != begin) { // skip no-op transitions + for (; tr - 1 != begin; --tr) { + if (!EquivTransitions(tr[-2].type_index, tr[-1].type_index)) break; + } + } + // When tr == end we return the "last" transition, ignoring future_spec_. + if (tr == begin) return false; + *tp = FromUnixSeconds((--tr)->unix_time); + return true; +} + +} // namespace cctz +} // namespace time_internal +} // namespace absl |