UuidHelper.java

/*
 * The MIT License
 *
 * Copyright (c) 2011 Dominic Williams, Daniel Washusen and contributors.
 *
 * 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 org.scale7.cassandra.pelops;

import java.util.Calendar;
import java.util.Date;
import java.util.UUID;

import org.joda.time.DateTime;

public class UuidHelper {
    /*
      Magic number obtained from #cassandra's thobbs, who
      claims to have stolen it from a Python library.
    */
    static final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH = 0x01b21dd213814000L;

	/**
	 * Generate a new time UUID insatnce.
	 * @return							A new time UUID object
	 */
	public static java.util.UUID newTimeUuid() {
		return java.util.UUID.fromString(new com.eaio.uuid.UUID().toString());
	}

    /**
     * @see #nonUniqueTimeUuidForDate(long)
     */
    public static java.util.UUID nonUniqueTimeUuidForDate(Date d) {
        return nonUniqueTimeUuidForDate(d.getTime());
    }

    /**
     * @see #nonUniqueTimeUuidForDate(long)
     */
    public static java.util.UUID nonUniqueTimeUuidForDate(Calendar c) {
        return nonUniqueTimeUuidForDate(c.getTime());
    }

    /**
     * @see #nonUniqueTimeUuidForDate(long)
     * <p>Note: the use of the class required the *optional* joda-time dependency.</p>
     */
    public static java.util.UUID nonUniqueTimeUuidForDate(DateTime d) {
        return nonUniqueTimeUuidForDate(d.getMillis());
    }

    /**
     * <p>This method is useful to create a <b>*non-unique*</b> TimeUUID instance from some time other than the present.
     * For example, to use as the lower bound in a SlicePredicate to retrieve all columns whose TimeUUID comes
     * after time X.
     *
     * <p><b>WARNING:</b> Never assume such a UUID is unique, use it only as a marker for a specific time.
     * <p>Note: This method and it's doco is taken (almost verbatim) from the Cassandra WIKI
     * (http://wiki.apache.org/cassandra/FAQ#working_with_timeuuid_in_java).
     * @param millis Gets the milliseconds of the datetime instant from the Java epoch of 1970-01-01T00:00:00Z
     * @return return
     */
    public static java.util.UUID nonUniqueTimeUuidForDate(long millis) {
        long time = millis * 10000 + NUM_100NS_INTERVALS_SINCE_UUID_EPOCH;
        long timeLow = time &       0xffffffffL;
        long timeMid = time &   0xffff00000000L;
        long timeHi = time & 0xfff000000000000L;
        long upperLong = (timeLow << 32) | (timeMid >> 16) | (1 << 12) | (timeHi >> 48) ;
        return new java.util.UUID(upperLong, 0xC000000000000000L);
    }

    /**
     * <p>Extracts the millis from the Java epoch of 1970-01-01T00:00:00Z.</p>
     * @param uuid the time uuid
     * @return the millis since Java epoch
     */
    public static long millisFromTimeUuid(UUID uuid) {
        return (uuid.timestamp() - NUM_100NS_INTERVALS_SINCE_UUID_EPOCH) / 10000;
    }
}