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Diffstat (limited to 'third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc')
-rw-r--r-- | third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc new file mode 100644 index 000000000000..030ae0e19e07 --- /dev/null +++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc @@ -0,0 +1,121 @@ +// 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. + +#include "time_zone_impl.h" + +#include <deque> +#include <mutex> +#include <string> +#include <unordered_map> +#include <utility> + +#include "absl/base/config.h" +#include "time_zone_fixed.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace time_internal { +namespace cctz { + +namespace { + +// time_zone::Impls are linked into a map to support fast lookup by name. +using TimeZoneImplByName = + std::unordered_map<std::string, const time_zone::Impl*>; +TimeZoneImplByName* time_zone_map = nullptr; + +// Mutual exclusion for time_zone_map. +std::mutex& TimeZoneMutex() { + // This mutex is intentionally "leaked" to avoid the static deinitialization + // order fiasco (std::mutex's destructor is not trivial on many platforms). + static std::mutex* time_zone_mutex = new std::mutex; + return *time_zone_mutex; +} + +} // namespace + +time_zone time_zone::Impl::UTC() { return time_zone(UTCImpl()); } + +bool time_zone::Impl::LoadTimeZone(const std::string& name, time_zone* tz) { + const time_zone::Impl* const utc_impl = UTCImpl(); + + // First check for UTC (which is never a key in time_zone_map). + auto offset = seconds::zero(); + if (FixedOffsetFromName(name, &offset) && offset == seconds::zero()) { + *tz = time_zone(utc_impl); + return true; + } + + // Then check, under a shared lock, whether the time zone has already + // been loaded. This is the common path. TODO: Move to shared_mutex. + { + std::lock_guard<std::mutex> lock(TimeZoneMutex()); + if (time_zone_map != nullptr) { + TimeZoneImplByName::const_iterator itr = time_zone_map->find(name); + if (itr != time_zone_map->end()) { + *tz = time_zone(itr->second); + return itr->second != utc_impl; + } + } + } + + // Now check again, under an exclusive lock. + std::lock_guard<std::mutex> lock(TimeZoneMutex()); + if (time_zone_map == nullptr) time_zone_map = new TimeZoneImplByName; + const Impl*& impl = (*time_zone_map)[name]; + if (impl == nullptr) { + // The first thread in loads the new time zone. + Impl* new_impl = new Impl(name); + new_impl->zone_ = TimeZoneIf::Load(new_impl->name_); + if (new_impl->zone_ == nullptr) { + delete new_impl; // free the nascent Impl + impl = utc_impl; // and fallback to UTC + } else { + impl = new_impl; // install new time zone + } + } + *tz = time_zone(impl); + return impl != utc_impl; +} + +void time_zone::Impl::ClearTimeZoneMapTestOnly() { + std::lock_guard<std::mutex> lock(TimeZoneMutex()); + if (time_zone_map != nullptr) { + // Existing time_zone::Impl* entries are in the wild, so we can't delete + // them. Instead, we move them to a private container, where they are + // logically unreachable but not "leaked". Future requests will result + // in reloading the data. + static auto* cleared = new std::deque<const time_zone::Impl*>; + for (const auto& element : *time_zone_map) { + cleared->push_back(element.second); + } + time_zone_map->clear(); + } +} + +time_zone::Impl::Impl(const std::string& name) : name_(name) {} + +const time_zone::Impl* time_zone::Impl::UTCImpl() { + static Impl* utc_impl = [] { + Impl* impl = new Impl("UTC"); + impl->zone_ = TimeZoneIf::Load(impl->name_); // never fails + return impl; + }(); + return utc_impl; +} + +} // namespace cctz +} // namespace time_internal +ABSL_NAMESPACE_END +} // namespace absl |