256be56344
-- 00d42e3d5433aaf29c2ed293520b2ba178ae8bdb by Greg Falcon <gfalcon@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 238061818 -- 867a7ca318fac2991ea9a4107dbae3cc9fbf974a by Abseil Team <absl-team@google.com>: Added a IWYU export pragma when including a standard header for the purpose of aliasing its symbols. PiperOrigin-RevId: 238022277 -- 17047745058f2f151cd986ea9f649512542d3876 by Matt Armstrong <marmstrong@google.com>: Clarify the comment discouraging WrapUnique<T>(x) calls. PiperOrigin-RevId: 237873803 -- 3dcb2e4968243d33ca0ce53280c445df50f4a7ec by Samuel Benzaquen <sbenza@google.com>: Workaround clang bug https://bugs.llvm.org/show_bug.cgi?id=38289 PiperOrigin-RevId: 237873551 -- f348d2dc7087a990cbdfb95aa51fd7ff478ae40e by Samuel Benzaquen <sbenza@google.com>: Reduce minimum capacity to 1. This reduces memory usage for small tables. A flat_hash_set<int> of 1 element goes from 92 bytes to 24. A flat_hash_set<string> of 1 element goes from 512 bytes to 56. PiperOrigin-RevId: 237859811 -- 9c8125be5e4e5d22a7bb62bdec8c323338385c1b by Jon Cohen <cohenjon@google.com>: Bump to CMake 3.5. This is the oldest modern cmake being included by default in most popular OS distributions according to https://repology.org/project/cmake/versions. Specifically, Ubuntu LTS 16.04 uses cmake 3.5 (https://packages.ubuntu.com/xenial/cmake) PiperOrigin-RevId: 237859345 -- 07638d672e0a4dced986a62750cfd8318ed36ffa by Derek Mauro <dmauro@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 237714597 GitOrigin-RevId: 00d42e3d5433aaf29c2ed293520b2ba178ae8bdb Change-Id: I5faecc45add4a5a774d4f9baf06e5519091f2ccc
108 lines
3.3 KiB
C++
108 lines
3.3 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 <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 "time_zone_fixed.h"
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namespace absl {
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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 time_zone_mutex;
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} // namespace
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time_zone time_zone::Impl::UTC() {
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return time_zone(UTCImpl());
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}
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bool time_zone::Impl::LoadTimeZone(const std::string& name, time_zone* tz) {
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const time_zone::Impl* const utc_impl = UTCImpl();
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// First 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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// Then check, under a shared lock, whether the time zone has already
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// been loaded. This is the common path. TODO: Move to shared_mutex.
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{
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std::lock_guard<std::mutex> lock(time_zone_mutex);
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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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// Now check again, under an exclusive lock.
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std::lock_guard<std::mutex> lock(time_zone_mutex);
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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) {
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// The first thread in loads the new time zone.
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Impl* new_impl = new Impl(name);
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new_impl->zone_ = TimeZoneIf::Load(new_impl->name_);
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if (new_impl->zone_ == nullptr) {
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delete new_impl; // free the nascent Impl
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impl = utc_impl; // and fallback to UTC
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} else {
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impl = new_impl; // install new time zone
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}
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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(time_zone_mutex);
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if (time_zone_map != nullptr) {
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// Existing time_zone::Impl* entries are in the wild, so we simply
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// leak them. Future requests will result in reloading the data.
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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) : name_(name) {}
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const time_zone::Impl* time_zone::Impl::UTCImpl() {
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static Impl* utc_impl = [] {
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Impl* impl = new Impl("UTC");
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impl->zone_ = TimeZoneIf::Load(impl->name_); // never fails
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return impl;
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}();
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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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} // namespace absl
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