inetaddress.java

gcc的组建

/* InetAddress.java -- Class to model an Internet address
   Copyright (C) 1998, 1999, 2002, 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.net;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.util.HashMap;
import java.util.StringTokenizer;

/**
 * This class models an Internet address.  It does not have a public
 * constructor.  Instead, new instances of this objects are created
 * using the static methods getLocalHost(), getByName(), and
 * getAllByName().
 *
 * <p>This class fulfills the function of the C style functions gethostname(),
 * gethostbyname(), and gethostbyaddr().  It resolves Internet DNS names
 * into their corresponding numeric addresses and vice versa.</p>
 *
 * @author Aaron M. Renn ([e-mail])
 * @author Per Bothner
 *
 * @specnote This class is not final since JK 1.4
 */
public class InetAddress implements Serializable
{
  private static final long serialVersionUID = 3286316764910316507L;

  /**
   * The default DNS hash table size,
   * Use a prime number happy with hash table.
   */
  private static final int DEFAULT_CACHE_SIZE = 89;

  /**
   * The default caching period in minutes.
   */
  private static final int DEFAULT_CACHE_PERIOD = 4 * 60;

  /**
   * Percentage of cache entries to purge when the table gets full.
   */
  private static final int DEFAULT_CACHE_PURGE_PCT = 30;

  /**
   * The special IP address INADDR_ANY.
   */
  private static InetAddress inaddr_any;

  /**
   * Dummy InetAddress, used to bind socket to any (all) network interfaces.
   */
  static InetAddress ANY_IF;

  /**
   * Stores static localhost address object.
   */
  static InetAddress LOCALHOST;

  /**
   * The size of the cache.
   */
  private static int cache_size = 0;

  /**
   * The length of time we will continue to read the address from cache
   * before forcing another lookup.
   */
  private static int cache_period = 0;

  /**
   * What percentage of the cache we will purge if it gets full.
   */
  private static int cache_purge_pct = 0;

  /**
   * HashMap to use as DNS lookup cache.
   * Use HashMap because all accesses to cache are already synchronized.
   */
  private static HashMap cache;

  static
  {
    // Look for properties that override default caching behavior
    cache_size =
      Integer.getInteger("gnu.java.net.dns_cache_size", DEFAULT_CACHE_SIZE)
             .intValue();
    cache_period =
      Integer.getInteger("gnu.java.net.dns_cache_period",
                         DEFAULT_CACHE_PERIOD * 60 * 1000).intValue();

    cache_purge_pct =
      Integer.getInteger("gnu.java.net.dns_cache_purge_pct",
                         DEFAULT_CACHE_PURGE_PCT).intValue();

    // Fallback to  defaults if necessary
    if ((cache_purge_pct < 1) || (cache_purge_pct > 100))
      cache_purge_pct = DEFAULT_CACHE_PURGE_PCT;

    // Create the cache
    if (cache_size != 0)
      cache = new HashMap(cache_size);

    // precompute the ANY_IF address
    try
      {
        ANY_IF = getInaddrAny();

	byte[] ip_localhost = { 127, 0, 0, 1 };
	LOCALHOST = new Inet4Address(ip_localhost, "localhost");
      }
    catch (UnknownHostException uhe)
      {
        // Hmmm, make one up and hope that it works.
        byte[] zeros = { 0, 0, 0, 0 };
        ANY_IF = new Inet4Address(zeros, "0.0.0.0");
      }
  }

  /**
   * The Serialized Form specifies that an int 'address' is saved/restored.
   * This class uses a byte array internally so we'll just do the conversion
   * at serialization time and leave the rest of the algorithm as is.
   */
  private int address;

  /**
   * An array of octets representing an IP address.
   */
  transient byte[] addr;

  /**
   * The name of the host for this address.
   */
  String hostName;

  /**
   * The time this address was looked up.
   */
  transient long lookup_time;

  /**
   * The field 'family' seems to be the AF_ value.
   * FIXME: Much of the code in the other java.net classes does not make
   * use of this family field.  A better implementation would be to make
   * use of getaddrinfo() and have other methods just check the family
   * field rather than examining the length of the address each time.
   */
  int family;

  /**
   * Initializes this object's addr instance variable from the passed in
   * byte array.  Note that this constructor is protected and is called
   * only by static methods in this class.
   *
   * @param ipaddr The IP number of this address as an array of bytes
   * @param hostname The hostname of this IP address.
   */
  InetAddress(byte[] ipaddr, String hostname)
  {
    addr = (null == ipaddr) ? null : (byte[]) ipaddr.clone();
    hostName = hostname;
    
    lookup_time = System.currentTimeMillis();

    family = 2; /* AF_INET */
  }

  /**
   * Returns true if this address is a multicast address, false otherwise.
   * An address is multicast if the high four bits are "1110".  These are
   * also known as "Class D" addresses.
   *
   * @return true if mulitcast, false if not
   *
   * @since 1.1
   */
  public boolean isMulticastAddress()
  {
    // Mask against high order bits of 1110
    if (addr.length == 4)
      return (addr[0] & 0xf0) == 0xe0;

    return false;
  }

  /**
   * Utility routine to check if the InetAddress in a wildcard address
   *
   * @since 1.4
   */
  public boolean isAnyLocalAddress()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    return equals(ANY_IF);
  }

  /**
   * Utility routine to check if the InetAddress is a loopback address
   *
   * @since 1.4
   */
  public boolean isLoopbackAddress()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    return (addr[0] & 0xff) == 0x7f;
  }

  /**
   * Utility routine to check if InetAddress is a link local address
   *
   * @since 1.4
   */
  public boolean isLinkLocalAddress()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    // XXX: This seems to not exist with IPv4 addresses
    return false;
  }

  /**
   * Utility routine to check if InetAddress is a site local address
   *
   * @since 1.4
   */
  public boolean isSiteLocalAddress()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.

    // 10.0.0.0/8
    if ((addr[0] & 0xff) == 0x0a)
      return true;

    // 172.16.0.0/12
    if ((addr[0] & 0xff) == 0xac && (addr[1] & 0xf0) == 0x10)
      return true;

    // 192.168.0.0/16
    if ((addr[0] & 0xff) == 0xc0 && (addr[1] & 0xff) == 0xa8)
      return true;

    // XXX: Do we need to check more addresses here ?
    return false;
  }

  /**
   * Utility routine to check if InetAddress is a global multicast address
   *
   * @since 1.4
   */
  public boolean isMCGlobal()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    // XXX: This seems to not exist with IPv4 addresses
    return false;
  }

  /**
   * Utility routine to check if InetAddress is a node local multicast address.
   *
   * @since 1.4
   */
  public boolean isMCNodeLocal()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    // XXX: This seems to not exist with IPv4 addresses
    return false;
  }

  /**
   * Utility routine to check if InetAddress is a link local multicast address.
   *
   * @since 1.4
   */
  public boolean isMCLinkLocal()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    if (! isMulticastAddress())
      return false;

    return ((addr[0] & 0xff) == 0xe0
	    && (addr[1] & 0xff)  == 0x00
	    && (addr[2] & 0xff)  == 0x00);
  }

  /**
   * Utility routine to check if InetAddress is a site local multicast address.
   *
   * @since 1.4
   */
  public boolean isMCSiteLocal()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    // XXX: This seems to not exist with IPv4 addresses
    return false;
  }

  /**
   * Utility routine to check if InetAddress is a organization local
   * multicast address.
   *
   * @since 1.4
   */
  public boolean isMCOrgLocal()
  {
    // This is the IPv4 implementation.
    // Any class derived from InetAddress should override this.
    // XXX: This seems to not exist with IPv4 addresses
    return false;
  }

  /**
   * Returns the hostname for this address.  This will return the IP address
   * as a String if there is no hostname available for this address
   *
   * @return The hostname for this address
   */
  public String getHostName()
  {
    if (hostName != null)
      return hostName;

    try
      {
	hostName = VMInetAddress.getHostByAddr(addr);
	return hostName;
      }
    catch (UnknownHostException e)
      {
	return getHostAddress();
      }
  }

  /**
   * Returns the canonical hostname represented by this InetAddress
   * 
   * @since 1.4
   */
  public String getCanonicalHostName()
  {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null)
      {
        try
	  {
            sm.checkConnect(hostName, -1);
	  }
	catch (SecurityException e)
	  {
	    return getHostAddress();
	  }
      }

    // Try to find the FDQN now
    InetAddress address;
    byte[] ipaddr = getAddress();

    if (ipaddr.length == 16)
      address = new Inet6Address(getAddress(), null);
    else