[libcxx-commits] [libcxx] [libc++][chrono] Loads tzdata.zi in tzdb. (PR #74928)

[Mark de Wever via libcxx-commits]

================
@@ -109,13 +497,108 @@ static string __parse_version(istream& __input) {
   return chrono::__parse_string(__input);
 }
 
+static void __parse_rule(tzdb& __tzdb, istream& __input) {
+  chrono::__skip_mandatory_whitespace(__input);
+  string __name = chrono::__parse_string(__input);
+
+  if (__tzdb.__rules.empty() || __tzdb.__rules.back().first != __name)
+    __tzdb.__rules.emplace_back(__name, vector<__tz::__rule>{});
+
+  __tz::__rule& __rule = __tzdb.__rules.back().second.emplace_back();
+
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__from = chrono::__parse_year(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__to = chrono::__parse_to(__input, __rule.__from);
+  chrono::__skip_mandatory_whitespace(__input);
+  chrono::__matches(__input, '-');
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__in_month = chrono::__parse_month(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__on = chrono::__parse_on(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__at = __parse_at(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__save = __parse_save(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  __rule.__letters = chrono::__parse_letters(__input);
+  chrono::__skip_line(__input);
+}
+
+static void __parse_zone(tzdb& __tzdb, istream& __input) {
+  chrono::__skip_mandatory_whitespace(__input);
+  vector<__tz::__continuation>& __continuations =
+      __tzdb.zones.emplace_back(chrono::__parse_string(__input)).__continuations();
+  chrono::__skip_mandatory_whitespace(__input);
+
+  do {
+    // The first line must be valid, continuations are optional.
+    __continuations.emplace_back(__parse_continuation(__input));
+    chrono::__skip_line(__input);
+    chrono::__skip_optional_whitespace(__input);
+  } while (std::isdigit(__input.peek()) || __input.peek() == '-');
+}
+
+static void __parse_link(tzdb& __tzdb, istream& __input) {
+  chrono::__skip_mandatory_whitespace(__input);
+  string __target = chrono::__parse_string(__input);
+  chrono::__skip_mandatory_whitespace(__input);
+  string __name = chrono::__parse_string(__input);
+  chrono::__skip_line(__input);
+
+  __tzdb.links.emplace_back(std::move(__name), std::move(__target));
+}
+
+static void __parse_tzdata(tzdb& __db, istream& __input) {
+  while (true) {
+    int __c = std::tolower(__input.get());
+
+    switch (__c) {
+    case istream::traits_type::eof():
+      return;
+
+    case ' ':
+    case '\t':
+    case '\n':
+      break;
+
+    case '#':
+      chrono::__skip_line(__input);
+      break;
+
+    case 'r':
+      chrono::__skip(__input, "ule");
+      chrono::__parse_rule(__db, __input);
+      break;
+
+    case 'z':
----------------
mordante wrote:

actually it's heavily used in the database. Typical there are one or more sets of RULE entries for a "region" followed by one or more "region"s which use the same rules. For example several countries in western Europe currently share the same time zone rule, but there are some historical differences so these countries are not a link.

https://github.com/llvm/llvm-project/pull/74928