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/*
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* Copyright 1996-2008 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package java.rmi.dgc;
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import java.io.*;
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import java.net.*;
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import java.rmi.server.UID;
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import java.security.*;
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/**
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* A VMID is a identifier that is unique across all Java virtual
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* machines. VMIDs are used by the distributed garbage collector
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* to identify client VMs.
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*
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* @author Ann Wollrath
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* @author Peter Jones
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*/
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public final class VMID implements java.io.Serializable {
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/** array of bytes uniquely identifying this host */
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private static byte[] localAddr = computeAddressHash();
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/**
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* @serial array of bytes uniquely identifying host created on
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*/
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private byte[] addr;
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/**
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* @serial unique identifier with respect to host created on
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*/
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private UID uid;
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/** indicate compatibility with JDK 1.1.x version of class */
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private static final long serialVersionUID = -538642295484486218L;
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/**
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* Create a new VMID. Each new VMID returned from this constructor
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* is unique for all Java virtual machines under the following
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* conditions: a) the conditions for uniqueness for objects of
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* the class <code>java.rmi.server.UID</code> are satisfied, and b) an
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* address can be obtained for this host that is unique and constant
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* for the lifetime of this object. <p>
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*/
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public VMID() {
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addr = localAddr;
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uid = new UID();
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}
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/**
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* Return true if an accurate address can be determined for this
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* host. If false, reliable VMID cannot be generated from this host
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* @return true if host address can be determined, false otherwise
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* @deprecated
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*/
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@Deprecated
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public static boolean isUnique() {
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return true;
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}
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/**
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* Compute hash code for this VMID.
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*/
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public int hashCode() {
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return uid.hashCode();
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}
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/**
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* Compare this VMID to another, and return true if they are the
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* same identifier.
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*/
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public boolean equals(Object obj) {
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if (obj instanceof VMID) {
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VMID vmid = (VMID) obj;
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if (!uid.equals(vmid.uid))
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return false;
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if ((addr == null) ^ (vmid.addr == null))
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return false;
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if (addr != null) {
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if (addr.length != vmid.addr.length)
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return false;
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for (int i = 0; i < addr.length; ++ i)
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if (addr[i] != vmid.addr[i])
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return false;
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}
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return true;
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} else {
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return false;
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}
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}
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/**
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* Return string representation of this VMID.
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*/
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public String toString() {
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StringBuffer result = new StringBuffer();
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if (addr != null)
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for (int i = 0; i < addr.length; ++ i) {
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int x = (int) (addr[i] & 0xFF);
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result.append((x < 0x10 ? "0" : "") +
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Integer.toString(x, 16));
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}
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result.append(':');
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result.append(uid.toString());
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return result.toString();
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}
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/**
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* Compute the hash an IP address. The hash is the first 8 bytes
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* of the SHA digest of the IP address.
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*/
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private static byte[] computeAddressHash() {
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/*
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* Get the local host's IP address.
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*/
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byte[] addr = java.security.AccessController.doPrivileged(
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new PrivilegedAction<byte[]>() {
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public byte[] run() {
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try {
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return InetAddress.getLocalHost().getAddress();
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} catch (Exception e) {
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}
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return new byte[] { 0, 0, 0, 0 };
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}
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});
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byte[] addrHash;
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final int ADDR_HASH_LENGTH = 8;
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try {
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/*
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* Calculate message digest of IP address using SHA.
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*/
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MessageDigest md = MessageDigest.getInstance("SHA");
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ByteArrayOutputStream sink = new ByteArrayOutputStream(64);
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DataOutputStream out = new DataOutputStream(
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new DigestOutputStream(sink, md));
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out.write(addr, 0, addr.length);
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out.flush();
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byte digest[] = md.digest();
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int hashlength = Math.min(ADDR_HASH_LENGTH, digest.length);
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addrHash = new byte[hashlength];
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System.arraycopy(digest, 0, addrHash, 0, hashlength);
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} catch (IOException ignore) {
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/* can't happen, but be deterministic anyway. */
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addrHash = new byte[0];
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} catch (NoSuchAlgorithmException complain) {
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throw new InternalError(complain.toString());
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}
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return addrHash;
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}
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}
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