uuidgen.java

uuid的实现

/* 
 * UUIDGen.java
 * 
 * Created on 09.08.2003.
 *
 * eaio: UUID - an implementation of the UUID specification
 * Copyright (c) 2003, 2004 Johann Burkard (<mailto:[e-mail]>)
 * <http://eaio.com>
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 
 */
package com.eaio.uuid;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.StringTokenizer;

import com.eaio.util.lang.Hex;

/**
 * This class contains methods to generate UUID fields. These methods have been
 * refactored out of {@link com.eaio.uuid.UUID} because of the problems certain
 * application servers have with static fields.
 * <p>
 * Starting with version 2, this implementation tries to obtain the MAC address
 * of the network card. Under Microsoft Windows, the <code>ifconfig</code>
 * command is used which may pop up a command window in Java Virtual Machines
 * prior to 1.4 once this class is initialized. The command window is closed
 * automatically.
 * <p>
 * The MAC address code has been tested extensively in Microsoft Windows,
 * Linux and Solaris 8, but should work in MacOS X and BSDs, too.
 * 
 * @author <a href="mailto:[e-mail]">Johann Burkard</a>
 * @version 2.1.1
 * @see com.eaio.uuid.UUID
 */
public final class UUIDGen {

    /**
     * No instances needed.
     */
    private UUIDGen() {}

    /**
     * The last time value. Used to remove duplicate UUIDs.
     */
    private static long lastTime = Long.MIN_VALUE;

    /**
     * The current clock and node value.
     */
    private static long clockSeqAndNode = 0x8000000000000000L;

    static {

        String macAddress = null;

        Process p = null;
        BufferedReader in = null;

        try {
            String osname = System.getProperty("os.name");

            if (osname.startsWith("Windows")) {
                p = Runtime.getRuntime().exec(
                        new String[] { "ipconfig", "/all" }, null);
            }
            // Solaris code must appear before the generic code 
            else if (osname.startsWith("Solaris") || osname.startsWith("SunOS")) {
                String hostName = getFirstLineOfCommand(new String[] { "uname",
                        "-n" });
                if (hostName != null) {
                    p = Runtime.getRuntime().exec(
                            new String[] { "/usr/sbin/arp", hostName }, null);
                }
            }
            else if (new File("/sbin/ifconfig").exists()) {
                p = Runtime.getRuntime().exec(
                        new String[] { "/sbin/ifconfig", "-a" }, null);
            }

            in = new BufferedReader(new InputStreamReader(p.getInputStream()),
                    128);
            String l = null;
            while ((l = in.readLine()) != null) {
                macAddress = MACAddressParser.parse(l);
                if (macAddress != null && Hex.parseShort(macAddress) != 0xff) break;
            }

        }
        catch (SecurityException ex) {}
        catch (IOException ex) {}
        finally {
            try {
                in.close();
            }
            catch (Exception ex) {}
            try {
                p.destroy();
            }
            catch (Exception ex) {}
        }

        if (macAddress != null) {
            StringTokenizer tokenizer = new StringTokenizer(macAddress, ":");
            for (int i = 5; i >= 0; --i) {
                String tk = tokenizer.nextToken();
                long l = Hex.parseShort(tk);
                clockSeqAndNode |= l << (i << 3);
            }
        }
        else {
            try {
                byte[] local = InetAddress.getLocalHost().getAddress();
                clockSeqAndNode |= (local[0] << 24) & 0xFF000000L;
                clockSeqAndNode |= (local[1] << 16) & 0xFF0000;
                clockSeqAndNode |= (local[2] << 8) & 0xFF00;
                clockSeqAndNode |= local[3] & 0xFF;
            }
            catch (UnknownHostException ex) {
                clockSeqAndNode |= (long) (Math.random() * 0x7FFFFFFF);
                ex.printStackTrace();
            }
        }

        // Skip the clock sequence generation process and use random instead.

        clockSeqAndNode |= (long) (Math.random() * 0x3FFF) << 48;

    }

    /**
     * Returns the current clockSeqAndNode value.
     * 
     * @return the clockSeqAndNode value
     * @see UUID#getClockSeqAndNode()
     */
    public static long getClockSeqAndNode() {
        return clockSeqAndNode;
    }

    /**
     * Generates a new time field. Each time field is unique and larger than the
     * previously generated time field.
     * 
     * @return a new time value
     * @see UUID#getTime()
     */
    public static synchronized long newTime() {

        long time;

        // UTC time

        long timeMillis = (System.currentTimeMillis() * 10000) + 0x01B21DD213814000L;

        if (timeMillis > lastTime) {
            lastTime = timeMillis;
        }
        else {
            timeMillis = ++lastTime;
        }

        // time low

        time = timeMillis << 32;

        // time mid

        time |= (timeMillis & 0xFFFF00000000L) >> 16;

        // time hi and version

        time |= 0x1000 | ((timeMillis >> 48) & 0x0FFF); // version 1

        return time;

    }

    /**
     * Returns the first line of the shell command.
     * 
     * @param commands the commands to run
     * @return the first line of the command
     * @throws IOException
     */
    static String getFirstLineOfCommand(String[] commands) throws IOException {

        Process p = null;
        BufferedReader reader = null;

        try {
            p = Runtime.getRuntime().exec(commands);
            reader = new BufferedReader(new InputStreamReader(
                    p.getInputStream()), 128);

            return reader.readLine();
        }
        finally {
            if (reader != null) {
                try {
                    reader.close();
                }
                catch (IOException ex) {}
            }
            if (p != null) {
                p.destroy();
            }
        }

    }

}