121 lines
4.5 KiB
C++
121 lines
4.5 KiB
C++
// Copyright 2017 The Crashpad Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "snapshot/posix/timezone.h"
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#include <stddef.h>
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#include <time.h>
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#include <iterator>
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#include "base/check.h"
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#include "base/logging.h"
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#include "build/build_config.h"
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namespace crashpad {
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namespace internal {
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void TimeZone(const timeval& snapshot_time,
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SystemSnapshot::DaylightSavingTimeStatus* dst_status,
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int* standard_offset_seconds,
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int* daylight_offset_seconds,
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std::string* standard_name,
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std::string* daylight_name) {
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tzset();
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tm local;
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PCHECK(localtime_r(&snapshot_time.tv_sec, &local)) << "localtime_r";
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*standard_name = tzname[0];
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bool found_transition = false;
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long probe_gmtoff = local.tm_gmtoff;
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#if BUILDFLAG(IS_ANDROID)
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// Some versions of the timezone database on Android have incorrect
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// information (e.g. Asia/Kolkata and Pacific/Honolulu). These timezones set
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// daylight to a non-zero value and return incorrect, >= 0 values for tm_isdst
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// in the probes below. If tzname[1] is set to a bogus value, assume the
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// timezone does not actually use daylight saving time.
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if (daylight && strncmp(tzname[1], "_TZif", 5) != 0) {
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#else
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if (daylight) {
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#endif
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// Scan forward and backward, one month at a time, looking for an instance
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// when the observance of daylight saving time is different than it is in
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// |local|. It’s possible that no such instance will be found even with
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// |daylight| set. This can happen in locations where daylight saving time
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// was once observed or is expected to be observed in the future, but where
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// no transitions to or from daylight saving time occurred or will occur
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// within a year of the current date. Arizona, which last observed daylight
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// saving time in 1967, is an example.
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static constexpr int kMonthDeltas[] =
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{0, 1, -1, 2, -2, 3, -3, 4, -4, 5, -5, 6, -6,
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7, -7, 8, -8, 9, -9, 10, -10, 11, -11, 12, -12};
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for (size_t index = 0; index < std::size(kMonthDeltas) && !found_transition;
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++index) {
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// Look at a day of each month at local noon. Set tm_isdst to -1 to avoid
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// giving mktime() any hints about whether to consider daylight saving
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// time in effect. mktime() accepts values of tm_mon that are outside of
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// its normal range and behaves as expected: if tm_mon is -1, it
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// references December of the preceding year, and if it is 12, it
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// references January of the following year.
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tm probe_tm = {};
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probe_tm.tm_hour = 12;
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probe_tm.tm_mday = std::min(local.tm_mday, 28);
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probe_tm.tm_mon = local.tm_mon + kMonthDeltas[index];
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probe_tm.tm_year = local.tm_year;
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probe_tm.tm_isdst = -1;
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if (mktime(&probe_tm) == -1) {
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PLOG(WARNING) << "mktime";
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continue;
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}
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if (probe_tm.tm_isdst < 0 || local.tm_isdst < 0) {
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LOG(WARNING) << "dst status not available";
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continue;
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}
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if (probe_tm.tm_isdst != local.tm_isdst) {
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found_transition = true;
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probe_gmtoff = probe_tm.tm_gmtoff;
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}
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}
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}
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if (found_transition) {
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*daylight_name = tzname[1];
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if (!local.tm_isdst) {
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*dst_status = SystemSnapshot::kObservingStandardTime;
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*standard_offset_seconds = local.tm_gmtoff;
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*daylight_offset_seconds = probe_gmtoff;
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} else {
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*dst_status = SystemSnapshot::kObservingDaylightSavingTime;
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*standard_offset_seconds = probe_gmtoff;
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*daylight_offset_seconds = local.tm_gmtoff;
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}
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} else {
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*daylight_name = tzname[0];
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*dst_status = SystemSnapshot::kDoesNotObserveDaylightSavingTime;
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#if BUILDFLAG(IS_ANDROID)
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// timezone is more reliably set correctly on Android.
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*standard_offset_seconds = -timezone;
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*daylight_offset_seconds = -timezone;
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#else
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*standard_offset_seconds = local.tm_gmtoff;
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*daylight_offset_seconds = local.tm_gmtoff;
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#endif // BUILDFLAG(IS_ANDROID)
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}
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}
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} // namespace internal
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} // namespace crashpad
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