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// 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 <memory>
#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 Impl* const utc_impl = UTCImpl();
// 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;
}
// Check whether the time zone has already been loaded.
{
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;
}
}
}
// Load the new time zone (outside the lock).
std::unique_ptr<const Impl> new_impl(new Impl(name));
// Add the new time zone to the map.
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) { // this thread won any load race
impl = new_impl->zone_ ? new_impl.release() : utc_impl;
}
*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), zone_(TimeZoneIf::Load(name_)) {}
const time_zone::Impl* time_zone::Impl::UTCImpl() {
static const Impl* utc_impl = new Impl("UTC"); // never fails
return utc_impl;
}
} // namespace cctz
} // namespace time_internal
ABSL_NAMESPACE_END
} // namespace absl
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