001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.util;
018
019import java.nio.ByteBuffer;
020import java.security.SecureRandom;
021import java.util.Random;
022import java.util.UUID;
023import java.util.concurrent.atomic.AtomicInteger;
024
025import org.apache.logging.log4j.Logger;
026import org.apache.logging.log4j.status.StatusLogger;
027import org.apache.logging.log4j.util.PropertiesUtil;
028
029/**
030 * Generates a unique ID. The generated UUID will be unique for approximately 8,925 years so long as
031 * less than 10,000 IDs are generated per millisecond on the same device (as identified by its MAC address).
032 */
033public final class UuidUtil {
034    /**
035     * System property that may be used to seed the UUID generation with an integer value.
036     */
037    public static final String UUID_SEQUENCE = "org.apache.logging.log4j.uuidSequence";
038
039    private static final Logger LOGGER = StatusLogger.getLogger();
040
041    private static final String ASSIGNED_SEQUENCES = "org.apache.logging.log4j.assignedSequences";
042
043    private static final AtomicInteger COUNT = new AtomicInteger(0);
044    private static final long TYPE1 = 0x1000L;
045    private static final byte VARIANT = (byte) 0x80;
046    private static final int SEQUENCE_MASK = 0x3FFF;
047    private static final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH = 0x01b21dd213814000L;
048    private static final long INITIAL_UUID_SEQNO = PropertiesUtil.getProperties().getLongProperty(UUID_SEQUENCE, 0);
049
050    private static final long LOW_MASK = 0xffffffffL;
051    private static final long MID_MASK = 0xffff00000000L;
052    private static final long HIGH_MASK = 0xfff000000000000L;
053    private static final int NODE_SIZE = 8;
054    private static final int SHIFT_2 = 16;
055    private static final int SHIFT_4 = 32;
056    private static final int SHIFT_6 = 48;
057    private static final int HUNDRED_NANOS_PER_MILLI = 10000;
058
059    private static final long LEAST = initialize(NetUtils.getMacAddress());
060
061    /* This class cannot be instantiated */
062    private UuidUtil() {
063    }
064
065    /**
066     * Initializes this class
067     * 
068     * @param mac MAC address
069     * @return Least
070     */
071    static long initialize(byte[] mac) {
072        final Random randomGenerator = new SecureRandom();
073        if (mac == null || mac.length == 0) {
074            mac = new byte[6];
075            randomGenerator.nextBytes(mac);
076        }
077        final int length = mac.length >= 6 ? 6 : mac.length;
078        final int index = mac.length >= 6 ? mac.length - 6 : 0;
079        final byte[] node = new byte[NODE_SIZE];
080        node[0] = VARIANT;
081        node[1] = 0;
082        for (int i = 2; i < NODE_SIZE; ++i) {
083            node[i] = 0;
084        }
085        System.arraycopy(mac, index, node, 2, length);
086        final ByteBuffer buf = ByteBuffer.wrap(node);
087        long rand = INITIAL_UUID_SEQNO;
088        String assigned = PropertiesUtil.getProperties().getStringProperty(ASSIGNED_SEQUENCES);
089        long[] sequences;
090        if (assigned == null) {
091            sequences = new long[0];
092        } else {
093            final String[] array = assigned.split(Patterns.COMMA_SEPARATOR);
094            sequences = new long[array.length];
095            int i = 0;
096            for (final String value : array) {
097                sequences[i] = Long.parseLong(value);
098                ++i;
099            }
100        }
101        if (rand == 0) {
102            rand = randomGenerator.nextLong();
103        }
104        rand &= SEQUENCE_MASK;
105        boolean duplicate;
106        do {
107            duplicate = false;
108            for (final long sequence : sequences) {
109                if (sequence == rand) {
110                    duplicate = true;
111                    break;
112                }
113            }
114            if (duplicate) {
115                rand = (rand + 1) & SEQUENCE_MASK;
116            }
117        } while (duplicate);
118        assigned = assigned == null ? Long.toString(rand) : assigned + ',' + Long.toString(rand);
119        System.setProperty(ASSIGNED_SEQUENCES, assigned);
120
121        return buf.getLong() | rand << SHIFT_6;
122    }
123
124    /**
125     * Generates Type 1 UUID. The time contains the number of 100NS intervals that have occurred
126     * since 00:00:00.00 UTC, 10 October 1582. Each UUID on a particular machine is unique to the 100NS interval
127     * until they rollover around 3400 A.D.
128     * <ol>
129     * <li>Digits 1-12 are the lower 48 bits of the number of 100 ns increments since the start of the UUID
130     * epoch.</li>
131     * <li>Digit 13 is the version (with a value of 1).</li>
132     * <li>Digits 14-16 are a sequence number that is incremented each time a UUID is generated.</li>
133     * <li>Digit 17 is the variant (with a value of binary 10) and 10 bits of the sequence number</li>
134     * <li>Digit 18 is final 16 bits of the sequence number.</li>
135     * <li>Digits 19-32 represent the system the application is running on.</li>
136     * </ol>
137     *
138     * @return universally unique identifiers (UUID)
139     */
140    public static UUID getTimeBasedUuid() {
141
142        final long time = ((System.currentTimeMillis() * HUNDRED_NANOS_PER_MILLI) +
143            NUM_100NS_INTERVALS_SINCE_UUID_EPOCH) + (COUNT.incrementAndGet() % HUNDRED_NANOS_PER_MILLI);
144        final long timeLow = (time & LOW_MASK) << SHIFT_4;
145        final long timeMid = (time & MID_MASK) >> SHIFT_2;
146        final long timeHi = (time & HIGH_MASK) >> SHIFT_6;
147        final long most = timeLow | timeMid | TYPE1 | timeHi;
148        return new UUID(most, LEAST);
149    }
150}
151