inetaddress.java

gcc的组建

	    
	    if (empty)
	      {
		if (i == 10 && x == 0xFFFF)
		  { // IPv4-mapped IPv6 address.
		    sb.append (":FFFF:");
		    break;  // Continue as IPv4 address;
		  }
		else if (i == 12)
		  { // IPv4-compatible IPv6 address.
		    sb.append (':');
		    break;  // Continue as IPv4 address.
		  }
		else if (i > 0)
		  sb.append ("::");
	      }
	    else
	      sb.append (':');
	    
	    if (x != 0 || i >= 14)
	      sb.append (Integer.toHexString (x).toUpperCase());
	  }
      }
    
    for ( ; ; )
      {
        sb.append(addr[i] & 0xff);
        i++;
	
        if (i == len)
          break;
	
        sb.append('.');
      }

    return sb.toString();
  }

  /**
   * Returns a hash value for this address.  Useful for creating hash
   * tables.  Overrides Object.hashCode()
   *
   * @return A hash value for this address.
   */
  public int hashCode()
  {
    // There hashing algorithm is not specified, but a simple experiment
    // shows that it is equal to the address, as a 32-bit big-endian integer.
    int hash = 0;
    int len = addr.length;
    int i = len > 4 ? len - 4 : 0;

    for (; i < len; i++)
      hash = (hash << 8) | (addr[i] & 0xff);

    return hash;
  }

  /**
   * Tests this address for equality against another InetAddress.  The two
   * addresses are considered equal if they contain the exact same octets.
   * This implementation overrides Object.equals()
   *
   * @param obj The address to test for equality
   *
   * @return true if the passed in object's address is equal to this one's,
   * false otherwise
   */
  public boolean equals(Object obj)
  {
    if (! (obj instanceof InetAddress))
      return false;

    // "The Java Class Libraries" 2nd edition says "If a machine has
    // multiple names instances of InetAddress for different name of
    // that same machine are not equal.  This is because they have
    // different host names."  This violates the description in the
    // JDK 1.2 API documentation.  A little experimentation
    // shows that the latter is correct.
    byte[] addr2 = ((InetAddress) obj).addr;

    if (addr.length != addr2.length)
      return false;

    for (int i = 0; i < addr.length; i++)
      if (addr[i] != addr2[i])
	return false;

    return true;
  }

  /**
   * Converts this address to a String.  This string contains the IP in
   * dotted decimal form. For example: "127.0.0.1"  This method is equivalent
   * to getHostAddress() and overrides Object.toString()
   *
   * @return This address in String form
   */
  public String toString()
  {
    String addr = getHostAddress();
    String host = (hostName != null) ? hostName : "";
    return host + "/" + addr;
  }

  /**
   * Returns an InetAddress object given the raw IP address.
   *
   * The argument is in network byte order: the highest order byte of the
   * address is in getAddress()[0].
   *
   * @param addr The IP address to create the InetAddress object from
   *
   * @exception UnknownHostException If IP address has illegal length
   *
   * @since 1.4
   */
  public static InetAddress getByAddress(byte[] addr)
    throws UnknownHostException
  {
    return getByAddress(null, addr);
  }

  /**
   * Creates an InetAddress based on the provided host name and IP address.
   * No name service is checked for the validity of the address.
   *
   * @param host The hostname of the InetAddress object to create
   * @param addr The IP address to create the InetAddress object from
   *
   * @exception UnknownHostException If IP address is of illegal length
   *
   * @since 1.4
   */
  public static InetAddress getByAddress(String host, byte[] addr)
    throws UnknownHostException
  {
    if (addr.length == 4)
      return new Inet4Address(addr, host);

    if (addr.length == 16)
      return new Inet6Address(addr, host);

    throw new UnknownHostException("IP address has illegal length");
  }

  /**
   * If hostname is a valid numeric IP address, return the numeric address.
   * Otherwise, return null.
   *
   * @param hostname the name of the host
   */
  private static native byte[] aton(String hostname);

  /**
   * Looks up all addresses of a given host.
   *
   * @param hostname the host to lookup
   * @param ipaddr the IP address to lookup
   * @param all return all known addresses for one host
   *
   * @return an array with all found addresses
   */
  private static native InetAddress[] lookup (String hostname,
		                              InetAddress ipaddr, boolean all);

  /**
   * Returns tha family type of an IP address.
   *
   * @param addr the IP address
   *
   * @return the family
   */
  private static native int getFamily (byte[] ipaddr);

  /**
   * Returns an InetAddress object representing the IP address of the given
   * hostname.  This name can be either a hostname such as "www.urbanophile.com"
   * or an IP address in dotted decimal format such as "127.0.0.1".  If the
   * hostname is null or "", the hostname of the local machine is supplied by
   * default.  This method is equivalent to returning the first element in
   * the InetAddress array returned from GetAllByName.
   *
   * @param hostname The name of the desired host, or null for the local 
   * loopback address.
   *
   * @return The address of the host as an InetAddress object.
   *
   * @exception UnknownHostException If no IP address for the host could
   * be found
   * @exception SecurityException If a security manager exists and its
   * checkConnect method doesn't allow the operation
   */
  public static InetAddress getByName(String hostname)
    throws UnknownHostException
  {
    // If null or the empty string is supplied, the loopback address
    // is returned. Note that this is permitted without a security check.
    if (hostname == null || hostname.length() == 0)
      return loopback;

    SecurityManager s = System.getSecurityManager();
    if (s != null)
      s.checkConnect(hostname, -1);

    // Assume that the host string is an IP address
    byte[] address = aton(hostname);
    if (address != null)
      {
        if (address.length == 4)
          return new Inet4Address (address, null);
        else if (address.length == 16)
          {
	    if ((address [10] == 0xFF) && (address [11] == 0xFF))
	      {
		byte[] ip4addr = new byte [4];
		ip4addr [0] = address [12];
		ip4addr [1] = address [13];
		ip4addr [2] = address [14];
		ip4addr [3] = address [15];
		return new Inet4Address (ip4addr, null);
	      }
            return new Inet6Address (address, null);
	  }
	else
          throw new UnknownHostException ("Address has invalid length");
      }

    // Try to resolve the host by DNS
    InetAddress result = new InetAddress(null, null);
    lookup (hostname, result, false);
    return result;
  }

  /**
   * Returns an array of InetAddress objects representing all the host/ip
   * addresses of a given host, given the host's name.  This name can be
   * either a hostname such as "www.urbanophile.com" or an IP address in
   * dotted decimal format such as "127.0.0.1".  If the value is null, the
   * hostname of the local machine is supplied by default.
   *
   * @param hostname The name of the desired host, or null for the
   * local loopback address.
   *
   * @return All addresses of the host as an array of InetAddress objects.
   *
   * @exception UnknownHostException If no IP address for the host could
   * be found
   * @exception SecurityException If a security manager exists and its
   * checkConnect method doesn't allow the operation
   */
  public static InetAddress[] getAllByName(String hostname)
    throws UnknownHostException
  {
    // If null or the empty string is supplied, the loopback address
    // is returned. Note that this is permitted without a security check.
    if (hostname == null || hostname.length() == 0)
      return new InetAddress[] {loopback};

    SecurityManager s = System.getSecurityManager();
    if (s != null)
      s.checkConnect(hostname, -1);

    // Check if hostname is an IP address
    byte[] address = aton (hostname);
    if (address != null)
      {
	InetAddress[] result = new InetAddress [1];
	result [0] = new InetAddress (address, null);
	return result;
      }

    // Try to resolve the hostname by DNS
    return lookup (hostname, null, true);
  }

  /**
   * This native method looks up the hostname of the local machine
   * we are on.  If the actual hostname cannot be determined, then the
   * value "localhost" will be used.  This native method wrappers the
   * "gethostname" function.
   *
   * @return The local hostname.
   */
  private static native String getLocalHostname();

  /**
   * Returns an InetAddress object representing the address of the current
   * host.
   *
   * @return The local host's address
   *
   * @exception UnknownHostException If no IP address for the host could
   * be found
   */
  public static InetAddress getLocalHost() throws UnknownHostException
  {
    SecurityManager s = System.getSecurityManager();
    
    // Experimentation shows that JDK1.2 does cache the result.
    // However, if there is a security manager, and the cached result
    // is other than "localhost", we need to check again.
    if (localhost == null
	|| (s != null && ! localhost.isLoopbackAddress()))
      getLocalHost (s);
    
    return localhost;
  }

  private static synchronized void getLocalHost (SecurityManager s)
    throws UnknownHostException
  {
    // Check the localhost cache again, now that we've synchronized.
    if (s == null && localhost != null)
      return;
    
    String hostname = getLocalHostname();
    
    if (s != null)
      {
	// "The Java Class Libraries" suggests that if the security
	// manager disallows getting the local host name, then
	// we use the loopback host.
	// However, the JDK 1.2 API claims to throw SecurityException,
	// which seems to suggest SecurityException is *not* caught.
	// In this case, experimentation shows that former is correct.
	try
	  {
	    // This is wrong, if the name returned from getLocalHostname()
	    // is not a fully qualified name.  FIXME.
	    s.checkConnect (hostname, -1);
	  }
	catch (SecurityException ex)
	  {
	    hostname = null;
	  }
      }
    
    if (hostname != null && hostname.length() != 0)
      {
	try
	  {
	    localhost = new InetAddress (null, null);
	    lookup (hostname, localhost, false);
	  }
	catch (Exception ex)
	  {
	  }
      }
    else
      throw new UnknownHostException();
    
    if (localhost == null)
      localhost = new InetAddress (loopbackAddress, "localhost");
  }

  /**
   * Needed for serialization
   */
  private void readResolve() throws ObjectStreamException
  {
    // FIXME: implement this
  }

  private void readObject(ObjectInputStream ois)
    throws IOException, ClassNotFoundException
  {
    ois.defaultReadObject();
    addr = new byte[4];
    addr[3] = (byte) address;

    for (int i = 2; i >= 0; --i)
      addr[i] = (byte) (address >>= 8);

    // Ignore family from serialized data.  Since the saved address is 32 bits
    // the deserialized object will have an IPv4 address i.e. AF_INET family.
    // FIXME: An alternative is to call the aton method on the deserialized
    // hostname to get a new address.  The Serialized Form doc is silent
    // on how these fields are used.
    family = getFamily (addr);
  }

  private void writeObject(ObjectOutputStream oos) throws IOException
  {
    // Build a 32 bit address from the last 4 bytes of a 4 byte IPv4 address
    // or a 16 byte IPv6 address.
    int len = addr.length;
    int i = len - 4;

    for (; i < len; i++)
      address = address << 8 | (((int) addr[i]) & 0xFF);

    oos.defaultWriteObject();
  }
}