www.pudn.com > jnp-src.rar > DNSInputStream.java

/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.io.*; 
import java.util.*; 
 
public class DNSInputStream extends ByteArrayInputStream { 
  protected DataInputStream dataIn; 
 
  public DNSInputStream (byte[] data, int off, int len) { 
    super (data, off, len); 
    dataIn = new DataInputStream (this); 
  } 
 
  public int readByte () throws IOException { 
    return dataIn.readUnsignedByte (); 
  } 
 
  public int readShort () throws IOException { 
    return dataIn.readUnsignedShort (); 
  } 
 
  public long readInt () throws IOException { 
    return dataIn.readInt () & 0xffffffffL; 
  } 
 
  public String readString () throws IOException { 
    int len = readByte (); 
    if (len == 0) { 
      return ""; 
    } else { 
      byte[] buffer = new byte[len]; 
      dataIn.readFully (buffer); 
      return new String (buffer, "latin1"); 
    } 
  } 
 
  public String readDomainName () throws IOException { 
    if (pos >= count) 
      throw new EOFException ("EOF reading domain name"); 
    if ((buf[pos] & 0xc0) == 0) { 
      String label = readString (); 
      if (label.length () > 0) { 
        String tail = readDomainName (); 
        if (tail.length () > 0) 
          label = label + '.' + tail; 
      } 
      return label; 
    } else { 
      if ((buf[pos] & 0xc0) != 0xc0) 
        throw new IOException ("Invalid domain name compression offset"); 
      int offset = readShort () & 0x3fff; 
      DNSInputStream dnsIn = 
        new DNSInputStream (buf, offset, buf.length - offset); 
      return dnsIn.readDomainName (); 
    } 
  } 
 
  public DNSRR readRR () throws IOException { 
    String rrName = readDomainName (); 
    int rrType = readShort (); 
    int rrClass = readShort (); 
    long rrTTL = readInt (); 
    int rrDataLen = readShort (); 
    DNSInputStream rrDNSIn = new DNSInputStream (buf, pos, rrDataLen); 
    pos += rrDataLen; 
    try { 
      String myName = getClass ().getName (); 
      int periodIndex = myName.lastIndexOf ('.'); 
      String myPackage = myName.substring (0, 1 + periodIndex); 
      Class theClass = Class.forName 
        (myPackage + "record." + DNS.typeName (rrType)); 
      DNSRR rr = (DNSRR) theClass.newInstance (); 
      rr.init (rrName, rrType, rrClass, rrTTL, rrDNSIn); 
      return rr; 
    } catch (ClassNotFoundException ex) { 
      throw new IOException ("Unknown DNSRR (type " + 
                             DNS.typeName (rrType) + " (" + rrType + "))"); 
    } catch (IllegalAccessException ex) { 
      throw new IOException ("Access error creating DNSRR (type " + 
                             DNS.typeName (rrType) + ')'); 
    } catch (InstantiationException ex) { 
      throw new IOException ("Instantiation error creating DNSRR (type " + 
                             DNS.typeName (rrType) + ')'); 
    } 
  } 
}