mcs/class/System/Mono.Dns/DnsPacket.cs

   1 //
   2 // Mono.Dns.DnsPacket
   3 //
   4 // Authors:
   5 //      Gonzalo Paniagua Javier (gonzalo.mono@gmail.com)
   6 //
   7 // Copyright 2011 Gonzalo Paniagua Javier
   8 //
   9 // Licensed under the Apache License, Version 2.0 (the "License");
  10 // you may not use this file except in compliance with the License.
  11 // You may obtain a copy of the License at
  12 //
  13 // http://www.apache.org/licenses/LICENSE-2.0
  14 //
  15 // Unless required by applicable law or agreed to in writing, software
  16 // distributed under the License is distributed on an "AS IS" BASIS,
  17 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  18 // See the License for the specific language governing permissions and
  19 // limitations under the License.
  20 //
  21 using System;
  22 using System.Collections.Generic;
  23 using System.Text;
  24 using System.IO;
  25
  26 namespace Mono.Dns {
  27 #if !NET_2_0
  28         public
  29 #endif
  30         abstract class DnsPacket {
  31                 protected byte [] packet;
  32                 protected int position;
  33                 protected DnsHeader header;
  34
  35                 protected DnsPacket ()
  36                 {
  37                         // Caller has to initialize packet, position and header
  38                 }
  39
  40                 protected DnsPacket (int length)
  41                         : this (new byte [length], length)
  42                 {
  43                 }
  44
  45                 protected DnsPacket (byte [] buffer, int length)
  46                 {
  47                         if (buffer == null)
  48                                 throw new ArgumentNullException("buffer");
  49                         if (length <= 0)
  50                                 throw new ArgumentOutOfRangeException("length", "Must be greater than zero.");
  51
  52                         packet = buffer;
  53                         position = length;
  54                         header = new DnsHeader(new ArraySegment<byte>(packet, 0, 12));
  55                 }
  56
  57                 public byte [] Packet {
  58                         get { return packet; }
  59                 }
  60
  61                 public int Length {
  62                         get { return position; }
  63                 }
  64
  65                 public DnsHeader Header {
  66                         get { return header; }
  67                 }
  68
  69                 protected void WriteUInt16 (ushort v)
  70                 {
  71                         packet [position++] = (byte) ((v & 0x0ff00) >> 8);
  72                         packet [position++] = (byte) (v & 0x0ff);
  73                 }
  74
  75                 protected void WriteStringBytes (string str, int offset, int count)
  76                 {
  77                         for (int i = offset, c = 0; c < count; c++, i++)
  78                                 packet [position++] = (byte) str [i]; // Don't care about encoding.
  79                 }
  80
  81                 protected void WriteLabel (string str, int offset, int count)
  82                 {
  83                         packet [position++] = (byte) count;
  84                         WriteStringBytes (str, offset, count);
  85                 }
  86
  87                 protected void WriteDnsName (string name)
  88                 {
  89                         if (!DnsUtil.IsValidDnsName (name))
  90                                 throw new ArgumentException ("Invalid DNS name");
  91
  92                         if (!String.IsNullOrEmpty (name)) {
  93                                 int len = name.Length;
  94                                 int label_start = 0;
  95                                 int label_len = 0;
  96                                 for (int i = 0; i < len; i++) {
  97                                         char c = name [i];
  98                                         if (c != '.') {
  99                                                 label_len++;
 100                                         } else {
 101                                                 if (i == 0)
 102                                                         break; // "."
 103                                                 WriteLabel (name, label_start, label_len);
 104                                                 label_start += label_len + 1; // Skip the dot
 105                                                 label_len = 0;
 106                                         }
 107                                 }
 108                                 if (label_len > 0)
 109                                         WriteLabel (name, label_start, label_len);
 110                         }
 111
 112                         packet [position++] = 0;
 113                 }
 114
 115                 protected internal string ReadName (ref int offset)
 116                 {
 117                         return DnsUtil.ReadName (packet, ref offset);
 118                 }
 119
 120                 protected internal static string ReadName (byte [] buffer, ref int offset)
 121                 {
 122                         return DnsUtil.ReadName (buffer, ref offset);
 123                 }
 124
 125                 protected internal ushort ReadUInt16 (ref int offset)
 126                 {
 127                         return (ushort)((packet[offset++] << 8) + packet[offset++]);
 128                 }
 129
 130                 protected internal int ReadInt32 (ref int offset)
 131                 {
 132                         return (packet [offset++] << 24) + (packet [offset++] << 16) + (packet [offset++] << 8) + packet [offset++];
 133                 }
 134         }
 135 }
 136