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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/rmi/dgc/VMID.java | |
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Diffstat (limited to 'libjava/classpath/java/rmi/dgc/VMID.java')
-rw-r--r-- | libjava/classpath/java/rmi/dgc/VMID.java | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/libjava/classpath/java/rmi/dgc/VMID.java b/libjava/classpath/java/rmi/dgc/VMID.java new file mode 100644 index 000000000..925c1bfb1 --- /dev/null +++ b/libjava/classpath/java/rmi/dgc/VMID.java @@ -0,0 +1,191 @@ +/* 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 gnu.java.lang.CPStringBuilder; + +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 () + { + CPStringBuilder buf = new CPStringBuilder ("[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(); + } +} |