/*

 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.rmi.dgc;

import java.rmi.server.UID;

import java.security.SecureRandom;

/**

 * A VMID is a identifier that is unique across all Java virtual

 * machines.  VMIDs are used by the distributed garbage collector

 * to identify client VMs.

 *

 * @author      Ann Wollrath

 * @author      Peter Jones

 */

public final class VMID implements java.io.Serializable {

    /** Array of bytes uniquely identifying this host */

    private static final byte[] randomBytes;

    /**

     * @serial array of bytes uniquely identifying host created on

     */

    private byte[] addr;

    /**

     * @serial unique identifier with respect to host created on

     */

    private UID uid;

    /** indicate compatibility with JDK 1.1.x version of class */

    private static final long serialVersionUID = -538642295484486218L;

    static {

        // Generate 8 bytes of random data.

        SecureRandom secureRandom = new SecureRandom();

        byte bytes[] = new byte[8];

        secureRandom.nextBytes(bytes);

        randomBytes = bytes;

    }

    /**

     * Create a new VMID.  Each new VMID returned from this constructor

     * is unique for all Java virtual machines under the following

     * conditions: a) the conditions for uniqueness for objects of

     * the class <code>java.rmi.server.UID</code> are satisfied, and b) an

     * address can be obtained for this host that is unique and constant

     * for the lifetime of this object.

     */

    public VMID() {

        addr = randomBytes;

        uid = new UID();

    }

    /**

     * Return true if an accurate address can be determined for this

     * host.  If false, reliable VMID cannot be generated from this host

     * @return true if host address can be determined, false otherwise

     * @deprecated

     */

    @Deprecated

    public static boolean isUnique() {

        return true;

    }

    /**

     * Compute hash code for this VMID.

     */

    public int hashCode() {

        return uid.hashCode();

    }

    /**

     * Compare this VMID to another, and return true if they are the

     * same identifier.

     */

    public boolean equals(Object obj) {

        if (obj instanceof VMID) {

            VMID vmid = (VMID) obj;

            if (!uid.equals(vmid.uid))

                return false;

            if ((addr == null) ^ (vmid.addr == null))

                return false;

            if (addr != null) {

                if (addr.length != vmid.addr.length)

                    return false;

                for (int i = 0; i < addr.length; ++ i)

                    if (addr[i] != vmid.addr[i])

                        return false;

            }

            return true;

        } else {

            return false;

        }

    }

    /**

     * Return string representation of this VMID.

     */

    public String toString() {

        StringBuilder sb = new StringBuilder();

        if (addr != null)

            for (int i = 0; i < addr.length; ++ i) {

                int x = addr[i] & 0xFF;

                sb.append((x < 0x10 ? "0" : "") +

                          Integer.toString(x, 16));

            }

        sb.append(':');

        sb.append(uid.toString());

        return sb.toString();

    }

}