[libc++][chrono] Loads tzdata.zi in tzdb. (#74928)

This implements the loading of the tzdata.zi file and store its contents
in the tzdb struct.

This adds all required members except:
- the leap seconds,
- the locate_zone, and
- current_zone.

The class time_zone is incomplete and only contains the parts needed for
storing the parsed data.

The class time_zone_link is fully implemented including its non-member
functions.

Implements parts of:
- P0355 Extending <chrono> to Calendars and Time Zones
- P1614 The Mothership has Landed

Implements:
- P1982 Rename link to time_zone_link

1 files changed, 0 insertions, 146 deletions

diff --git a/libcxx/src/tz.cpp b/libcxx/src/tz.cpp
deleted file mode 100644
index 4425f0e..0000000
--- a/libcxx/src/tz.cpp
+++ /dev/null
@@ -1,146 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-// For information see https://libcxx.llvm.org/DesignDocs/TimeZone.html
-
-#include <chrono>
-#include <filesystem>
-#include <fstream>
-#include <stdexcept>
-#include <string>
-
-// Contains a parser for the IANA time zone data files.
-//
-// These files can be found at https://data.iana.org/time-zones/ and are in the
-// public domain. Information regarding the input can be found at
-// https://data.iana.org/time-zones/tz-how-to.html and
-// https://man7.org/linux/man-pages/man8/zic.8.html.
-//
-// As indicated at https://howardhinnant.github.io/date/tz.html#Installation
-// For Windows another file seems to be required
-// https://raw.githubusercontent.com/unicode-org/cldr/master/common/supplemental/windowsZones.xml
-// This file seems to contain the mapping of Windows time zone name to IANA
-// time zone names.
-//
-// However this article mentions another way to do the mapping on Windows
-// https://devblogs.microsoft.com/oldnewthing/20210527-00/?p=105255
-// This requires Windows 10 Version 1903, which was released in May of 2019
-// and considered end of life in December 2020
-// https://learn.microsoft.com/en-us/lifecycle/announcements/windows-10-1903-end-of-servicing
-//
-// TODO TZDB Implement the Windows mapping in tzdb::current_zone
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-namespace chrono {
-
-// This function is weak so it can be overriden in the tests. The
-// declaration is in the test header test/support/test_tzdb.h
-_LIBCPP_WEAK string_view __libcpp_tzdb_directory() {
-#if defined(__linux__)
-  return "/usr/share/zoneinfo/";
-#else
-#  error "unknown path to the IANA Time Zone Database"
-#endif
-}
-
-[[nodiscard]] static bool __is_whitespace(int __c) { return __c == ' ' || __c == '\t'; }
-
-static void __skip_optional_whitespace(istream& __input) {
-  while (chrono::__is_whitespace(__input.peek()))
-    __input.get();
-}
-
-static void __skip_mandatory_whitespace(istream& __input) {
-  if (!chrono::__is_whitespace(__input.get()))
-    std::__throw_runtime_error("corrupt tzdb: expected whitespace");
-
-  chrono::__skip_optional_whitespace(__input);
-}
-
-static void __matches(istream& __input, char __expected) {
-  if (std::tolower(__input.get()) != __expected)
-    std::__throw_runtime_error((string("corrupt tzdb: expected character '") + __expected + '\'').c_str());
-}
-
-static void __matches(istream& __input, string_view __expected) {
-  for (auto __c : __expected)
-    if (std::tolower(__input.get()) != __c)
-      std::__throw_runtime_error((string("corrupt tzdb: expected string '") + string(__expected) + '\'').c_str());
-}
-
-[[nodiscard]] static string __parse_string(istream& __input) {
-  string __result;
-  while (true) {
-    int __c = __input.get();
-    switch (__c) {
-    case ' ':
-    case '\t':
-    case '\n':
-      __input.unget();
-      [[fallthrough]];
-    case istream::traits_type::eof():
-      if (__result.empty())
-        std::__throw_runtime_error("corrupt tzdb: expected a string");
-
-      return __result;
-
-    default:
-      __result.push_back(__c);
-    }
-  }
-}
-
-static string __parse_version(istream& __input) {
-  // The first line in tzdata.zi contains
-  //    # version YYYYw
-  // The parser expects this pattern
-  // #\s*version\s*\(.*)
-  // This part is not documented.
-  chrono::__matches(__input, '#');
-  chrono::__skip_optional_whitespace(__input);
-  chrono::__matches(__input, "version");
-  chrono::__skip_mandatory_whitespace(__input);
-  return chrono::__parse_string(__input);
-}
-
-static tzdb __make_tzdb() {
-  tzdb __result;
-
-  filesystem::path __root = chrono::__libcpp_tzdb_directory();
-  ifstream __tzdata{__root / "tzdata.zi"};
-
-  __result.version = chrono::__parse_version(__tzdata);
-  return __result;
-}
-
-//===----------------------------------------------------------------------===//
-//                           Public API
-//===----------------------------------------------------------------------===//
-
-_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI tzdb_list& get_tzdb_list() {
-  static tzdb_list __result{chrono::__make_tzdb()};
-  return __result;
-}
-
-_LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const tzdb& reload_tzdb() {
-  if (chrono::remote_version() == chrono::get_tzdb().version)
-    return chrono::get_tzdb();
-
-  return chrono::get_tzdb_list().__emplace_front(chrono::__make_tzdb());
-}
-
-_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI string remote_version() {
-  filesystem::path __root = chrono::__libcpp_tzdb_directory();
-  ifstream __tzdata{__root / "tzdata.zi"};
-  return chrono::__parse_version(__tzdata);
-}
-
-} // namespace chrono
-
-_LIBCPP_END_NAMESPACE_STD