com.carmatech.cassandra.CorbaTimeUUID.java Source code

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Here is the source code for com.carmatech.cassandra.CorbaTimeUUID.java

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/*******************************************************************************
 * Copyright 2013 Marc CARRE
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package com.carmatech.cassandra;

import java.util.Date;

import org.joda.time.DateTime;

import com.eaio.uuid.UUID;
import com.eaio.uuid.UUIDGen;

public final class CorbaTimeUUID {
    private CorbaTimeUUID() {
        // Pure utility class, do NOT instantiate.
    }

    private static final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH = 0x01b21dd213814000L;
    private static long lastTimestamp = Long.MIN_VALUE;

    /**
     * WARNING: Use only for testing purposes, as it may lead to duplicate UUIDs. Re-initialize the value of the last timestamp seen.
     */
    public static synchronized void reset() {
        lastTimestamp = Long.MIN_VALUE;
    }

    /**
     * Generate a new, unique UUID based on current timestamp.
     */
    public static UUID createUUID() {
        return createUUID(System.currentTimeMillis());
    }

    /**
     * Generate a new, unique UUID based on the provided date-time.
     * 
     * @param dateTime
     *            date-time used for the "time" component of the UUID.
     */
    public static UUID createUUID(final DateTime dateTime) {
        return createUUID(dateTime.getMillis());
    }

    /**
     * Generate a new, unique UUID based on the provided date.
     * 
     * @param javaDate
     *            date used for the "time" component of the UUID.
     */
    public static UUID createUUID(final Date javaDate) {
        return createUUID(javaDate.getTime());
    }

    /**
     * Generate a new, unique UUID based on the provided timestamp.
     * 
     * @param timestamp
     *            timestamp used for the "time" component of the UUID.
     */
    public static UUID createUUID(final long timestamp) {
        final long timestampIn100Ns = to100Ns(timestamp);
        final long uniqueTimestampIn100Ns = makeUnique(timestampIn100Ns);
        return new com.eaio.uuid.UUID(toUUIDTime(uniqueTimestampIn100Ns), UUIDGen.getClockSeqAndNode());
    }

    private static long to100Ns(final long timestampInMs) {
        return (timestampInMs * 10000) + NUM_100NS_INTERVALS_SINCE_UUID_EPOCH;
    }

    private static synchronized long makeUnique(final long timestamp) {
        if (timestamp > lastTimestamp) {
            lastTimestamp = timestamp;
            return timestamp;
        } else {
            return ++lastTimestamp;
        }
    }

    private static long toUUIDTime(final long timestampIn100Ns) {
        // Example:
        // Lowest 16 bits and version 1: 0123 4567 89AB CDEF -> 89AB CDEF 0000 0000 -> 89AB CDEF 0000 1000
        // Middle 32 bits: 0123 4567 89AB CDEF -> 0000 4567 0000 0000 -> 0000 0000 4567 0000 -> 89AB CDEF 4567 1000
        // Highest 16 bits: 0123 4567 89AB CDEF -> 0123 0000 0000 0000 -> 0000 0000 0000 0123 -> 89AB CDEF 4567 1123

        long uuidTime = (timestampIn100Ns << 32) | 0x0000000000001000L;
        uuidTime |= (timestampIn100Ns & 0x0000FFFF00000000L) >>> 16;
        uuidTime |= (timestampIn100Ns & 0xFFFF000000000000L) >>> 48;
        return uuidTime;
    }

    /**
     * WARNING: returned UUID is not unique. Get the UUID corresponding to the provided date-time and the clock sequence, which depends on the IP and MAC
     * addresses of the current machine, and a random component per process/JVM.
     * 
     * @param dateTime
     *            date-time used for the "time" component of the UUID.
     */
    public static UUID toUUID(final DateTime dateTime) {
        return toUUID(dateTime.getMillis());
    }

    /**
     * WARNING: returned UUID is not unique. Get the UUID corresponding to the provided date and the clock sequence, which depends on the IP and MAC addresses
     * of the current machine, and a random component per process/JVM.
     * 
     * @param javaDate
     *            date used for the "time" component of the UUID.
     */
    public static UUID toUUID(final Date javaDate) {
        return toUUID(javaDate.getTime());
    }

    /**
     * WARNING: returned UUID is not unique. Get the UUID corresponding to the provided timestamp and the clock sequence, which depends on the IP and MAC
     * addresses of the current machine, and a random component per process/JVM.
     * 
     * @param timestamp
     *            timestamp used for the "time" component of the UUID.
     */
    public static UUID toUUID(final long timestamp) {
        final long timestampIn100Ns = to100Ns(timestamp);
        return new com.eaio.uuid.UUID(toUUIDTime(timestampIn100Ns), UUIDGen.getClockSeqAndNode());
    }

    /**
     * Extract the "time" component of the provided UUID.
     * 
     * @param uuid
     *            UUID to extract timestamp from.
     * @return Timestamp in milliseconds.
     */
    public static long toMillis(final UUID uuid) {
        return from100Ns(fromUUIDTime(uuid.getTime()));
    }

    private static long from100Ns(long timestampIn100Ns) {
        return (timestampIn100Ns - NUM_100NS_INTERVALS_SINCE_UUID_EPOCH) / 10000;
    }

    private static long fromUUIDTime(final long uuidTime) {
        // Example:
        // Lowest 16 bits: 89AB CDEF 4567 1123 -> 0000 0000 89AB CDEF
        // Middle 32 bits: 89AB CDEF 4567 1123 -> 0000 0000 4567 0000 -> 0000 4567 0000 0000 -> 0000 4567 89AB CDEF
        // Highest 16 bits and version 1: 89AB CDEF 4567 1123 -> 0000 0000 0000 0123 -> 0123 0000 0000 0000 -> 0123 4567 89AB CDEF

        long timestampIn100Ns = uuidTime >>> 32;
        timestampIn100Ns |= (uuidTime & 0x00000000FFFF0000L) << 16;
        timestampIn100Ns |= (uuidTime & 0x0000000000000FFFL) << 48;
        return timestampIn100Ns;
    }
}