// 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. #ifndef ABSL_TIME_INTERNAL_CCTZ_ZONE_INFO_SOURCE_H_ #define ABSL_TIME_INTERNAL_CCTZ_ZONE_INFO_SOURCE_H_ #include <cstddef> #include <functional> #include <memory> #include <string> #include "absl/base/config.h" namespace absl { ABSL_NAMESPACE_BEGIN namespace time_internal { namespace cctz { // A stdio-like interface for providing zoneinfo data for a particular zone. class ZoneInfoSource { … }; } // namespace cctz } // namespace time_internal ABSL_NAMESPACE_END } // namespace absl namespace absl { ABSL_NAMESPACE_BEGIN namespace time_internal { namespace cctz_extension { // A function-pointer type for a factory that returns a ZoneInfoSource // given the name of a time zone and a fallback factory. Returns null // when the data for the named zone cannot be found. ZoneInfoSourceFactory; // The user can control the mapping of zone names to zoneinfo data by // providing a definition for cctz_extension::zone_info_source_factory. // For example, given functions my_factory() and my_other_factory() that // can return a ZoneInfoSource for a named zone, we could inject them into // cctz::load_time_zone() with: // // namespace cctz_extension { // namespace { // std::unique_ptr<cctz::ZoneInfoSource> CustomFactory( // const std::string& name, // const std::function<std::unique_ptr<cctz::ZoneInfoSource>( // const std::string& name)>& fallback_factory) { // if (auto zip = my_factory(name)) return zip; // if (auto zip = fallback_factory(name)) return zip; // if (auto zip = my_other_factory(name)) return zip; // return nullptr; // } // } // namespace // ZoneInfoSourceFactory zone_info_source_factory = CustomFactory; // } // namespace cctz_extension // // This might be used, say, to use zoneinfo data embedded in the program, // or read from a (possibly compressed) file archive, or both. // // cctz_extension::zone_info_source_factory() will be called: // (1) from the same thread as the cctz::load_time_zone() call, // (2) only once for any zone name, and // (3) serially (i.e., no concurrent execution). // // The fallback factory obtains zoneinfo data by reading files in ${TZDIR}, // and it is used automatically when no zone_info_source_factory definition // is linked into the program. extern ZoneInfoSourceFactory zone_info_source_factory; } // namespace cctz_extension } // namespace time_internal ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_TIME_INTERNAL_CCTZ_ZONE_INFO_SOURCE_H_