8f2828c4b4
ccdbb5941 Export of internal Abseil changes 01f5f81f9 Export of internal Abseil changes 2c92bdc7c Export of internal Abseil changes e7ebf9803 Export of internal Abseil changes 2eba343b5 Export of internal Abseil changes a8b03d90e Export of internal Abseil changes 1d31b5c36 Export of internal Abseil changes da3a87690 Export of internal Abseil changes 8faf20461 Exclude empty directories (#697) 2069dc796 Export of internal Abseil changes 4832bf6bf Added a BUILD file in root to expose license. (#695) af8f994af Export of internal Abseil changes 33caf1097 Export of internal Abseil changes cf1a02e2d Export of internal Abseil changes git-subtree-dir: third_party/abseil_cpp git-subtree-split: ccdbb5941f992fabda7eae3ce72f55efc17c826a
113 lines
3.6 KiB
C++
113 lines
3.6 KiB
C++
// Copyright 2016 Google Inc. All Rights Reserved.
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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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// https://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 "time_zone_impl.h"
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#include <deque>
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#include <memory>
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#include <mutex>
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#include <string>
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#include <unordered_map>
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#include <utility>
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#include "absl/base/config.h"
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#include "time_zone_fixed.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace time_internal {
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namespace cctz {
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namespace {
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// time_zone::Impls are linked into a map to support fast lookup by name.
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using TimeZoneImplByName =
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std::unordered_map<std::string, const time_zone::Impl*>;
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TimeZoneImplByName* time_zone_map = nullptr;
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// Mutual exclusion for time_zone_map.
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std::mutex& TimeZoneMutex() {
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// This mutex is intentionally "leaked" to avoid the static deinitialization
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// order fiasco (std::mutex's destructor is not trivial on many platforms).
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static std::mutex* time_zone_mutex = new std::mutex;
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return *time_zone_mutex;
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}
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} // namespace
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time_zone time_zone::Impl::UTC() { return time_zone(UTCImpl()); }
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bool time_zone::Impl::LoadTimeZone(const std::string& name, time_zone* tz) {
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const Impl* const utc_impl = UTCImpl();
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// Check for UTC (which is never a key in time_zone_map).
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auto offset = seconds::zero();
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if (FixedOffsetFromName(name, &offset) && offset == seconds::zero()) {
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*tz = time_zone(utc_impl);
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return true;
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}
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// Check whether the time zone has already been loaded.
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{
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std::lock_guard<std::mutex> lock(TimeZoneMutex());
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if (time_zone_map != nullptr) {
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TimeZoneImplByName::const_iterator itr = time_zone_map->find(name);
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if (itr != time_zone_map->end()) {
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*tz = time_zone(itr->second);
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return itr->second != utc_impl;
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}
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}
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}
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// Load the new time zone (outside the lock).
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std::unique_ptr<const Impl> new_impl(new Impl(name));
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// Add the new time zone to the map.
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std::lock_guard<std::mutex> lock(TimeZoneMutex());
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if (time_zone_map == nullptr) time_zone_map = new TimeZoneImplByName;
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const Impl*& impl = (*time_zone_map)[name];
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if (impl == nullptr) { // this thread won any load race
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impl = new_impl->zone_ ? new_impl.release() : utc_impl;
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}
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*tz = time_zone(impl);
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return impl != utc_impl;
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}
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void time_zone::Impl::ClearTimeZoneMapTestOnly() {
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std::lock_guard<std::mutex> lock(TimeZoneMutex());
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if (time_zone_map != nullptr) {
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// Existing time_zone::Impl* entries are in the wild, so we can't delete
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// them. Instead, we move them to a private container, where they are
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// logically unreachable but not "leaked". Future requests will result
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// in reloading the data.
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static auto* cleared = new std::deque<const time_zone::Impl*>;
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for (const auto& element : *time_zone_map) {
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cleared->push_back(element.second);
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}
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time_zone_map->clear();
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}
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}
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time_zone::Impl::Impl(const std::string& name)
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: name_(name), zone_(TimeZoneIf::Load(name_)) {}
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const time_zone::Impl* time_zone::Impl::UTCImpl() {
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static const Impl* utc_impl = new Impl("UTC"); // never fails
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return utc_impl;
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}
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} // namespace cctz
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} // namespace time_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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