TimeUUIDUtils.java

package me.prettyprint.cassandra.utils;

import java.nio.ByteBuffer;
import java.util.UUID;

import com.eaio.uuid.UUIDGen;

import me.prettyprint.cassandra.service.clock.MicrosecondsSyncClockResolution;
import me.prettyprint.hector.api.ClockResolution;

/**
 * Utilitary class to generate TimeUUID (type 1)
 *
 * @author Patricio Echague (pechague@gmail.com)
 *
 */
public final class TimeUUIDUtils {
	
  static final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH = 0x01b21dd213814000L;

  /**
   * Gets a new and unique time uuid in milliseconds. It is useful to use in a TimeUUIDType sorted column family.
   *
   * @return the time uuid
   */
  public static java.util.UUID getUniqueTimeUUIDinMillis() {
    return new java.util.UUID(UUIDGen.newTime(), UUIDGen.getClockSeqAndNode());
  }

  /**
   * Gets a new time uuid using {@link ClockResolution#createClock()} as a time generator.
   * It is useful to use in a TimeUUIDType sorted column family.
   *
   * @param clock a ClockResolution
   * @return the time uuid
   */
  public static java.util.UUID getTimeUUID(ClockResolution clock) {
    return getTimeUUID(clock.createClock());
  }

  /**
   * Gets a new time uuid based on <code>time<code>.
   * NOTE: this algorithm does not resolve duplicates. To avoid duplicates use
   * {@link getTimeUUID(ClockResolution clock)} with an implementaion that provides unique timestamp resolution, like
   * {@link MicrosecondsSyncClockResolution}
   * It is useful to use in a TimeUUIDType sorted column family.
   *
   * @param clock a ClockResolution
   * @return the time uuid
   */
  public static java.util.UUID getTimeUUID(long time) {
    return new java.util.UUID(createTime(time), UUIDGen.getClockSeqAndNode());
  }

  private static long createTime(long currentTime) {
    long time;

    // UTC time
    long timeToUse = (currentTime * 10000) + NUM_100NS_INTERVALS_SINCE_UUID_EPOCH;

    // time low
    time = timeToUse << 32;

    // time mid
    time |= (timeToUse & 0xFFFF00000000L) >> 16;

    // time hi and version
    time |= 0x1000 | ((timeToUse >> 48) & 0x0FFF); // version 1
    return time;
  }


  /**
   * Returns an instance of uuid. Useful for when you read out of cassandra
   * you are getting a byte[] that needs to be converted into a TimeUUID.
   *
   * @param uuid the uuid
   * @return the java.util.uuid
   */
  public static java.util.UUID toUUID(byte[] uuid) {
    return uuid(uuid, 0);
  }

  /**
   * Retrieves the time as long based on the byte[] representation of a UUID.
   *
   * @param uuid byte[] uuid representation
   * @return a long representing the time
   */
  public static long getTimeFromUUID(byte[] uuid) {
    return getTimeFromUUID(TimeUUIDUtils.toUUID(uuid));
  }
  
  public static long getTimeFromUUID(UUID uuid) {
    return (uuid.timestamp() - NUM_100NS_INTERVALS_SINCE_UUID_EPOCH) / 10000;
  }

  /**
   * As byte array.
   * This method is often used in conjunction with @link {@link #getTimeUUID()}
   *
   * @param uuid the uuid
   *
   * @return the byte[]
   */
  public static byte[] asByteArray(java.util.UUID uuid) {
    long msb = uuid.getMostSignificantBits();
    long lsb = uuid.getLeastSignificantBits();
    byte[] buffer = new byte[16];

    for (int i = 0; i < 8; i++) {
      buffer[i] = (byte) (msb >>> 8 * (7 - i));
    }

    for (int i = 8; i < 16; i++) {
      buffer[i] = (byte) (lsb >>> 8 * (7 - i));
    }

    return buffer;
  }

  /**
   * Coverts a java.util.UUID into a ByteBuffer.
   * @param uuid a java.util.UUID
   * @return a ByteBuffer representaion of the param UUID
   */
  public static ByteBuffer asByteBuffer(java.util.UUID uuid) {
    if (uuid == null) {
      return null;
    }

    return ByteBuffer.wrap(asByteArray(uuid));
  }


  public static UUID uuid(byte[] uuid, int offset) {
    ByteBuffer bb = ByteBuffer.wrap(uuid, offset, 16);
    return new UUID(bb.getLong(), bb.getLong());
  }

  /**
   * Converts a ByteBuffer containing a UUID into a java.util.UUID
   * @param bb a ByteBuffer containing a UUID
   * @return a java.util.UUID
   */
  public static UUID uuid(ByteBuffer bb) {
    bb = bb.slice();
    return new UUID(bb.getLong(), bb.getLong());
  }

}