| /* VMID.java -- The object ID, unique between all virtual machines. |
| Copyright (c) 1996, 1997, 1998, 1999, 2006 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.rmi.dgc; |
| |
| import java.io.Serializable; |
| import java.net.InetAddress; |
| import java.net.UnknownHostException; |
| import java.rmi.server.UID; |
| import java.util.Arrays; |
| |
| /** |
| * An identifier that is unique accross the all virtual machines. This class is |
| * used by distributed garbage collector to identify the virtual machine of |
| * the client, but may also be used in various other cases, when such identifier |
| * is required. This class separately stores and transfers the host IP |
| * address, but will try to do its best also for the case if it failed to |
| * determine it. The alternative algorithms are used in {@link UID} that is |
| * part of this class. The VMID's, created on the same host, but in the two |
| * separately (parallely) running virtual machines are different. |
| */ |
| public final class VMID implements Serializable |
| { |
| /** |
| * Use SVUID for interoperability. |
| */ |
| static final long serialVersionUID = -538642295484486218L; |
| |
| /** |
| * If true, the IP of this host can ve reliably determined. |
| */ |
| static boolean areWeUnique; |
| |
| /** |
| * The IP address of the local host. |
| */ |
| static byte[] localAddr; |
| |
| /** |
| * The IP address of the local host. |
| */ |
| private byte[] addr; |
| |
| /** |
| * The cached hash code. |
| */ |
| transient int hash; |
| |
| /** |
| * The UID of this VMID. |
| */ |
| private UID uid; |
| |
| static |
| { |
| // This "local host" value usually indicates that the local |
| // IP address cannot be reliably determined. |
| byte[] localHost = new byte[] { 127, 0, 0, 1 }; |
| |
| try |
| { |
| localAddr = InetAddress.getLocalHost().getAddress(); |
| areWeUnique = !Arrays.equals(localHost, localAddr); |
| } |
| catch (UnknownHostException uhex) |
| { |
| localAddr = localHost; |
| areWeUnique = false; |
| } |
| } |
| |
| /** |
| * Create the new VMID. All VMID's are unique accross tha all virtual |
| * machines. |
| */ |
| public VMID() |
| { |
| addr = localAddr; |
| uid = new UID(); |
| } |
| |
| /** |
| * Return true if it is possible to get the accurate address of this host. |
| * If false is returned, the created VMID's are less reliable, but the |
| * starting time and possibly the memory allocation are also taken into |
| * consideration in the incorporated UID. Hence the VMID's, created on the |
| * different virtual machines, still should be different. |
| * |
| * @deprecated VMID's are more or less always reliable. |
| * |
| * @return false if the local host ip address is 127.0.0.1 or unknown, |
| * true otherwise. |
| */ |
| public static boolean isUnique () |
| { |
| return areWeUnique; |
| } |
| |
| /** |
| * Get the hash code of this VMID. |
| */ |
| public int hashCode () |
| { |
| if (hash==0) |
| { |
| for (int i = 0; i < localAddr.length; i++) |
| hash += addr[i]; |
| hash = hash ^ uid.hashCode(); |
| } |
| return hash; |
| } |
| |
| /** |
| * Returns true if the passed parameter is also VMID and it is equal to this |
| * VMID. The VMID should only be equal to itself (also if the passed value is |
| * another instance, cloned by serialization). |
| */ |
| public boolean equals(Object obj) |
| { |
| if (obj instanceof VMID) |
| { |
| VMID other = (VMID) obj; |
| |
| // The UID's are compared faster than arrays. |
| return uid.equals(other.uid) && Arrays.equals(addr, other.addr); |
| } |
| else |
| return false; |
| |
| } |
| |
| /** |
| * Get the string representation of this VMID. |
| */ |
| public String toString () |
| { |
| StringBuffer buf = new StringBuffer ("[VMID: "); |
| |
| for (int i = 0; i < addr.length; i++) |
| { |
| if (i > 0) |
| { |
| buf.append ("."); |
| } |
| |
| buf.append (Integer.toString (addr [i])); |
| } |
| |
| buf.append (" "); |
| buf.append (uid.toString ()); |
| buf.append ("]"); |
| |
| return buf.toString(); |
| } |
| } |