/*
* Copyright 2004-2006 Luke Quinane and Daniel Frampton
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
using System;
using NDns.Message;
namespace NDns.Message.Records{
/// <summary>
/// A DNS Mail eXchanger record.
/// </summary>
public class MXRecord : Record, IComparable
{
/// <summary>
/// The preference associated with this MX record.
/// </summary>
protected ushort preference;
/// <summary>
/// The name of the MX server.
/// </summary>
protected string mxName;
/// <summary>
/// Creates a MX record from the given string and preference.
/// </summary>
/// <param name="mxName">The string of the MX record.</param>
/// <param name="perference">The preference of the MX record.</param>
public MXRecord(string mxName, ushort perference)
{
this.mxName = mxName;
this.preference = perference;
}
/// <summary>
/// Creates a MX record from the given byte data.
/// </summary>
/// <param name="data">The data to create the MX record from.</param>
/// <param name="start">The position to start reading the byte array from.</param>
/// <param name="length">The number of bytes read from the byte array.</param>
/// <param name="coder">The coder to use when parsing the data.</param>
public MXRecord(byte[] data, ushort start, out ushort length, DomainCoder coder)
{
// get the preference
ushort position = start;
this.preference = (ushort) (data[position++] << 8);
this.preference |= data[position++];
// get the answer name
ushort dataLength;
this.mxName = coder.DecodeDomain(data, position, out dataLength);
position += dataLength;
this.type = QType.MX;
length = (ushort) (position - start);
}
/// <summary>
/// Returns the MX string for this record.
/// </summary>
public string MX
{
get
{
return this.mxName;
}
}
/// <summary>
/// Returns the preference for this record.
/// </summary>
public int Preference
{
get
{
return this.preference;
}
}
/// <summary>
/// The data associated with this record as a user readable string.
/// </summary>
public override string Data {
get {
return this.mxName + " " + this.preference;
}
}
#region IComparable Members
/// <summary>
/// Compares this MX record to another MX record, sorting by perference.
/// </summary>
/// <param name="obj">The other MX to compare to.</param>
/// <returns>-1 if this MX is perferable, 1 otherwise.</returns>
public int CompareTo(object obj) {
MXRecord otherMX = (MXRecord) obj;
if (this.preference > otherMX.preference) {
return 1;
} else if (this.preference < otherMX.preference) {
return -1;
} else {
// Choose a random record for MXs with equal perference.
Random r = new Random();
int i = r.Next(2);
if (i == 0) {
return -1;
}else {
return 1;
}
}
}
#endregion
}
}
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