/// <inheritdoc />
public override IWireSerialiser Read(WireReader reader)
{
// Read standard properties of a resource record.
Name = reader.ReadDomainName();
Type = (DnsType)reader.ReadUInt16();
Class = (DnsClass)reader.ReadUInt16();
TTL = reader.ReadTimeSpan32();
int length = reader.ReadUInt16();
// Find a specific class for the TYPE or default
// to UnknownRecord.
var specific = ResourceRegistry.Create(Type);
specific.Name = Name;
specific.Type = Type;
specific.Class = Class;
specific.TTL = TTL;
// Read the specific properties of the resource record.
var end = reader.Position + length;
specific.ReadData(reader, length);
if (reader.Position != end)
{
throw new InvalidDataException("Found extra data while decoding RDATA.");
}
return(specific);
}
/// <summary>
/// Read a resource record.
/// </summary>
/// <returns>
/// A <see cref="ResourceRecord"/> or <b>null</b> if no more
/// resource records are available.
/// </returns>
/// <remarks>
/// Processes the "$ORIGIN" and "$TTL" specials that define the
/// <see cref="Origin"/> and a default time-to-live respectively.
/// <para>
/// A domain name can be "@" to refer to the <see cref="Origin"/>.
/// A missing domain name will use the previous record's domain name.
/// </para>
/// <para>
/// Defaults the <see cref="ResourceRecord.Class"/> to <see cref="DnsClass.IN"/>.
/// Defaults the <see cref="ResourceRecord.TTL"/> to either the "$TTL" or
/// the <see cref="ResourceRecord.DefaultTTL"/>.
/// </para>
/// </remarks>
public ResourceRecord ReadResourceRecord()
{
DomainName domainName = defaultDomainName;
DnsClass klass = DnsClass.IN;
TimeSpan? ttl = defaultTTL;
DnsType? type = null;
while (!type.HasValue)
{
var token = ReadToken(ignoreEscape: true);
if (token == "")
{
return(null);
}
// Domain names and directives must be at the start of a line.
if (tokenStartsNewLine)
{
switch (token)
{
case "$ORIGIN":
Origin = ReadDomainName();
break;
case "$TTL":
defaultTTL = ttl = ReadTimeSpan32();
break;
case "@":
domainName = Origin;
defaultDomainName = domainName;
break;
default:
domainName = MakeAbsoluteDomainName(token);
defaultDomainName = domainName;
break;
}
continue;
}
// Is TTL?
if (token.All(c => Char.IsDigit(c)))
{
ttl = TimeSpan.FromSeconds(uint.Parse(token));
continue;
}
// Is TYPE?
if (token.StartsWith("TYPE"))
{
type = (DnsType)ushort.Parse(token.Substring(4), CultureInfo.InvariantCulture);
continue;
}
if (token.ToLowerInvariant() != "any" && Enum.TryParse <DnsType>(token, out DnsType t))
{
type = t;
continue;
}
// Is CLASS?
if (token.StartsWith("CLASS"))
{
klass = (DnsClass)ushort.Parse(token.Substring(5), CultureInfo.InvariantCulture);
continue;
}
if (Enum.TryParse <DnsClass>(token, out DnsClass k))
{
klass = k;
continue;
}
throw new InvalidDataException($"Unknown token '{token}', expected a Class, Type or TTL.");
}
if (domainName == null)
{
throw new InvalidDataException("Missing resource record name.");
}
// Create the specific resource record based on the type.
var resource = ResourceRegistry.Create(type.Value);
resource.Name = domainName;
resource.Type = type.Value;
resource.Class = klass;
if (ttl.HasValue)
{
resource.TTL = ttl.Value;
}
// Read the specific properties of the resource record.
resource.ReadData(this);
return(resource);
}