/// <summary>
/// Parses a single line of an TZDB zone info file.
/// </summary>
/// <remarks>
/// <para>
/// TZDB files have a simple line based structure. Each line defines one item. Comments
/// start with a hash or pound sign (#) and continue to the end of the line. Blank lines are
/// ignored. Of the remaining there are four line types which are determined by the first
/// keyword on the line.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Link</c> defines an alias between one time zone and
/// another. Both time zones use the same definition but have different names.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Rule</c> defines a daylight savings time
/// calculation rule.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Zone</c> defines a time zone.
/// </para>
/// <para>
/// A line beginning with leading whitespace (an empty keyword) defines another part of the
/// preceeding time zone. As many lines as necessary to define the time zone can be listed,
/// but they must all be together and only the first line can have a name.
/// </para>
/// </remarks>
/// <param name="line">The line to parse.</param>
/// <param name="database">The database to fill.</param>
/// <return>The zone name just parsed, if any - so that it can be passed into the next call.</return>
private string ParseLine(string line, string previousZone, TzdbDatabase database)
{
// Trim end-of-line comments
int index = line.IndexOf("#", StringComparison.Ordinal);
if (index >= 0)
{
line = line.Substring(0, index);
}
line = line.TrimEnd();
if (line.Length == 0)
{
// We can still continue with the previous zone
return(previousZone);
}
// Okay, everything left in the line should be "real" now.
var tokens = Tokens.Tokenize(line);
var keyword = NextString(tokens, "Keyword");
switch (keyword)
{
case KeywordRule:
database.AddRule(ParseRule(tokens));
return(null);
case KeywordLink:
var alias = ParseLink(tokens);
database.AddAlias(alias.Item1, alias.Item2);
return(null);
case KeywordZone:
var name = NextString(tokens, "GetName");
database.AddZone(ParseZone(name, tokens));
return(name);
default:
if (string.IsNullOrEmpty(keyword))
{
if (previousZone == null)
{
throw new InvalidDataException("Zone continuation provided with no previous zone line");
}
database.AddZone(ParseZone(previousZone, tokens));
return(previousZone);
}
else
{
throw new InvalidDataException($"Unexpected zone database keyword: {keyword}");
}
}
}
/// <summary>
/// Parses a single line of an TZDB zone info file.
/// </summary>
/// <remarks>
/// <para>
/// TZDB files have a simple line based structure. Each line defines one item. Comments
/// start with a hash or pound sign (#) and continue to the end of the line. Blank lines are
/// ignored. Of the remaining there are four line types which are determined by the first
/// keyword on the line.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Link</c> defines an alias between one time zone and
/// another. Both time zones use the same definition but have different names.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Rule</c> defines a daylight savings time
/// calculation rule.
/// </para>
/// <para>
/// A line beginning with the keyword <c>Zone</c> defines a time zone.
/// </para>
/// <para>
/// A line beginning with leading whitespace (an empty keyword) defines another part of the
/// preceeding time zone. As many lines as necessary to define the time zone can be listed,
/// but they must all be together and only the first line can have a name.
/// </para>
/// </remarks>
/// <param name="line">The line to parse.</param>
/// <param name="database">The database to fill.</param>
internal void ParseLine(string line, TzdbDatabase database)
{
int index = line.IndexOf("#", StringComparison.Ordinal);
if (index == 0)
{
return;
}
if (index > 0)
{
line = line.Substring(0, index - 1);
}
line = line.TrimEnd();
if (line.Length == 0)
{
return;
}
var tokens = Tokens.Tokenize(line);
var keyword = NextString(tokens, "Keyword");
switch (keyword)
{
case KeywordRule:
database.AddRule(ParseRule(tokens));
break;
case KeywordLink:
database.AddAlias(ParseLink(tokens));
break;
case KeywordZone:
var name = NextString(tokens, "GetName");
var namedZone = ParseZone(name, tokens);
database.AddZone(namedZone);
break;
default:
if (string.IsNullOrEmpty(keyword))
{
var zone = ParseZone(string.Empty, tokens);
database.AddZone(zone);
}
else
{
throw new InvalidDataException("Unexpected zone database keyword: " + keyword);
}
break;
}
}
