/// <summary>
/// Construct the question reading from a DNS Server response. Consult RFC1035 4.1.2
/// for byte-wise details of this structure in byte array form
/// </summary>
/// <param name="pointer"> a logical pointer to the Question in byte array form </param>
public Question(Pointer pointer)
{
// extract from the message
this._domain = pointer.ReadDomain();
this._dnsType = (DnsType)pointer.ReadShort();
this._dnsClass = (DnsClass)pointer.ReadShort();
}
/// <summary>
/// Construct the question reading from a DNS Server response. Consult RFC1035 4.1.2
/// for byte-wise details of this structure in byte array form
/// </summary>
/// <param name="pointer"> a logical pointer to the Question in byte array form </param>
public Question(Pointer pointer)
{
// extract from the message
this._domain = pointer.ReadDomain();
this._dnsType = (DnsType) pointer.ReadShort();
this._dnsClass = (DnsClass) pointer.ReadShort();
}
/// <summary>
/// Reads a domain name from the byte array. The method by which this works is described
/// in RFC1035 - 4.1.4. Essentially to minimise the size of the message, if part of a domain
/// name already been seen in the message, rather than repeating it, a pointer to the existing
/// definition is used. Each word in a domain name is a label, and is preceded by its length
///
/// eg. bigdevelopments.co.uk
///
/// is [15] (size of bigdevelopments) + "bigdevelopments"
/// [2] "co"
/// [2] "uk"
/// [1] 0 (NULL)
/// </summary>
/// <returns> the byte at the pointer </returns>
public string ReadDomain()
{
StringBuilder domain = new StringBuilder();
int length = 0;
// get the length of the first label
while ((length = this.ReadByte()) != 0)
{
// top 2 bits set denotes domain name compression and to reference elsewhere
if ((length & 0xc0) == 0xc0)
{
// work out the existing domain name, copy this pointer
Pointer newPointer = this.Copy();
// and move it to where specified here
newPointer.SetPosition((length & 0x3f) << 8 | this.ReadByte());
// repeat call recursively
domain.Append(newPointer.ReadDomain());
return(domain.ToString());
}
// if not using compression, copy a char at a time to the domain name
while (length > 0)
{
domain.Append(this.ReadChar());
length--;
}
// if size of next label isn't null (end of domain name) add a period ready for next label
if (this.Peek() != 0)
{
domain.Append('.');
}
}
// and return
return(domain.ToString());
}
/// <summary>
/// Constructs an MX record by reading bytes from a return message
/// </summary>
/// <param name="pointer"> A logical pointer to the bytes holding the record </param>
public MXRecord(Pointer pointer)
{
this._preference = pointer.ReadShort();
this._domainName = pointer.ReadDomain();
}
/// <summary>
/// Constructs an MX record by reading bytes from a return message
/// </summary>
/// <param name="pointer"> A logical pointer to the bytes holding the record </param>
public MXRecord(Pointer pointer)
{
this._preference = pointer.ReadShort();
this._domainName = pointer.ReadDomain();
}