f78f93bc9f
This is the first step to implement time zone support in libc++. This adds the complete tzdb_list class and a minimal tzdb class. The tzdb class only contains the version, which is used by reload_tzdb. Next to these classes it contains documentation and build system support needed for time zone support. The code depends on the IANA Time Zone Database, which should be available on the platform used or provided by the libc++ vendors. The code is labeled as experimental since there will be ABI breaks during development; the tzdb class needs to have the standard headers. Implements parts of: - P0355 Extending <chrono> to Calendars and Time Zones Addresses: - LWG3319 Properly reference specification of IANA time zone database Reviewed By: #libc, ldionne Differential Revision: https://reviews.llvm.org/D154282
114 lines
3.4 KiB
C++
114 lines
3.4 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// For information see https://libcxx.llvm.org/DesignDocs/TimeZone.html
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#include <chrono>
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#include <__mutex/unique_lock.h>
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#include <forward_list>
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// When threads are not available the locking is not required.
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#ifndef _LIBCPP_HAS_NO_THREADS
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# include <shared_mutex>
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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namespace chrono {
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//===----------------------------------------------------------------------===//
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// Private API
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//===----------------------------------------------------------------------===//
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class tzdb_list::__impl {
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public:
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explicit __impl(tzdb&& __tzdb) { __tzdb_.push_front(std::move(__tzdb)); }
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using const_iterator = tzdb_list::const_iterator;
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const tzdb& front() const noexcept {
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#ifndef _LIBCPP_HAS_NO_THREADS
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shared_lock __lock{__mutex_};
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#endif
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return __tzdb_.front();
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}
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const_iterator erase_after(const_iterator __p) {
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#ifndef _LIBCPP_HAS_NO_THREADS
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unique_lock __lock{__mutex_};
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#endif
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return __tzdb_.erase_after(__p);
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}
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tzdb& __emplace_front(tzdb&& __tzdb) {
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#ifndef _LIBCPP_HAS_NO_THREADS
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unique_lock __lock{__mutex_};
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#endif
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return __tzdb_.emplace_front(std::move(__tzdb));
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}
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const_iterator begin() const noexcept {
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#ifndef _LIBCPP_HAS_NO_THREADS
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shared_lock __lock{__mutex_};
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#endif
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return __tzdb_.begin();
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}
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const_iterator end() const noexcept {
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// forward_list<T>::end does not access the list, so no need to take a lock.
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return __tzdb_.end();
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}
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const_iterator cbegin() const noexcept { return begin(); }
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const_iterator cend() const noexcept { return end(); }
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private:
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#ifndef _LIBCPP_HAS_NO_THREADS
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mutable shared_mutex __mutex_;
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#endif
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forward_list<tzdb> __tzdb_;
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};
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//===----------------------------------------------------------------------===//
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// Public API
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//===----------------------------------------------------------------------===//
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_LIBCPP_EXPORTED_FROM_ABI tzdb_list::tzdb_list(tzdb&& __tzdb) : __impl_{new __impl(std::move(__tzdb))} {}
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_LIBCPP_EXPORTED_FROM_ABI tzdb_list::~tzdb_list() { delete __impl_; }
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_LIBCPP_NODISCARD_EXT _LIBCPP_EXPORTED_FROM_ABI const tzdb& tzdb_list::front() const noexcept {
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return __impl_->front();
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}
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_LIBCPP_EXPORTED_FROM_ABI tzdb_list::const_iterator tzdb_list::erase_after(const_iterator __p) {
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return __impl_->erase_after(__p);
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}
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_LIBCPP_EXPORTED_FROM_ABI tzdb& tzdb_list::__emplace_front(tzdb&& __tzdb) {
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return __impl_->__emplace_front(std::move(__tzdb));
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}
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_LIBCPP_NODISCARD_EXT _LIBCPP_EXPORTED_FROM_ABI tzdb_list::const_iterator tzdb_list::begin() const noexcept {
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return __impl_->begin();
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}
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_LIBCPP_NODISCARD_EXT _LIBCPP_EXPORTED_FROM_ABI tzdb_list::const_iterator tzdb_list::end() const noexcept {
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return __impl_->end();
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}
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_LIBCPP_NODISCARD_EXT _LIBCPP_EXPORTED_FROM_ABI tzdb_list::const_iterator tzdb_list::cbegin() const noexcept {
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return __impl_->cbegin();
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}
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_LIBCPP_NODISCARD_EXT _LIBCPP_EXPORTED_FROM_ABI tzdb_list::const_iterator tzdb_list::cend() const noexcept {
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return __impl_->cend();
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}
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} // namespace chrono
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_LIBCPP_END_NAMESPACE_STD
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