org.apache.cassandra.utils

Class UUIDGen

java.lang.Object

org.apache.cassandra.utils.UUIDGen

public class UUIDGen
extends java.lang.Object

The goods are here: www.ietf.org/rfc/rfc4122.txt.

Method Summary

Modifier and Type	Method and Description
static byte[]	decompose(java.util.UUID uuid) decomposes a uuid into raw bytes.
static long	getAdjustedTimestamp(java.util.UUID uuid) Returns a milliseconds-since-epoch value for a type-1 UUID.
static java.util.UUID	getRandomTimeUUIDFromMicros(long whenInMicros) Similar to getTimeUUIDFromMicros, but randomize (using SecureRandom) the clock and sequence.
static java.util.UUID	getTimeUUID() Creates a type 1 UUID (time-based UUID).
static java.util.UUID	getTimeUUID(long when) Creates a type 1 UUID (time-based UUID) with the timestamp of @param when, in milliseconds.
static java.util.UUID	getTimeUUID(long when, long nanos)
static java.util.UUID	getTimeUUID(long when, long nanos, long clockSeqAndNode)
static byte[]	getTimeUUIDBytes() Returns a 16 byte representation of a type 1 UUID (a time-based UUID), based on the current system time.
static byte[]	getTimeUUIDBytes(long timeMillis, int nanos) Converts a 100-nanoseconds precision timestamp into the 16 byte representation of a type 1 UUID (a time-based UUID).
static java.util.UUID	getTimeUUIDFromMicros(long whenInMicros) Returns a version 1 UUID using the provided timestamp and the local clock and sequence.
static java.util.UUID	getUUID(java.nio.ByteBuffer raw) creates a type 1 uuid from raw bytes.
static java.util.UUID	maxTimeUUID(long timestamp) Returns the biggest possible type 1 UUID having the provided timestamp.
static long	microsTimestamp(java.util.UUID uuid)
static java.util.UUID	minTimeUUID(long timestamp) Returns the smaller possible type 1 UUID having the provided timestamp.
static long	unixTimestamp(java.util.UUID uuid)
static int	unixTimestampInSec(java.util.UUID uuid)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getTimeUUID

public static java.util.UUID getTimeUUID()

Creates a type 1 UUID (time-based UUID).

Returns:

a UUID instance

getTimeUUID

public static java.util.UUID getTimeUUID(long when)

Creates a type 1 UUID (time-based UUID) with the timestamp of @param when, in milliseconds.

Returns:

a UUID instance

getTimeUUIDFromMicros

public static java.util.UUID getTimeUUIDFromMicros(long whenInMicros)

Returns a version 1 UUID using the provided timestamp and the local clock and sequence.

Note that this method is generally only safe to use if you can guarantee that the provided parameter is unique across calls (otherwise the returned UUID won't be unique accross calls).

Parameters:

whenInMicros - a unix time in microseconds.

Returns:

a new UUID id such that microsTimestamp(id) == whenInMicros. Please not that multiple calls to this method with the same value of whenInMicros will return the same UUID.

getRandomTimeUUIDFromMicros

public static java.util.UUID getRandomTimeUUIDFromMicros(long whenInMicros)

Similar to getTimeUUIDFromMicros, but randomize (using SecureRandom) the clock and sequence.

If you can guarantee that the whenInMicros argument is unique (for this JVM instance) for every call, then you should prefer getTimeUUIDFromMicros which is faster. If you can't guarantee this however, this method will ensure the returned UUID are still unique (accross calls) through randomization.

Parameters:

whenInMicros - a unix time in microseconds.

Returns:

a new UUID id such that microsTimestamp(id) == whenInMicros. The UUID returned by different calls will be unique even if whenInMicros is not.

getTimeUUID

public static java.util.UUID getTimeUUID(long when,
                                         long nanos)

getTimeUUID

public static java.util.UUID getTimeUUID(long when,
                                         long nanos,
                                         long clockSeqAndNode)

getUUID

public static java.util.UUID getUUID(java.nio.ByteBuffer raw)

creates a type 1 uuid from raw bytes.

decompose

public static byte[] decompose(java.util.UUID uuid)

decomposes a uuid into raw bytes.

getTimeUUIDBytes

public static byte[] getTimeUUIDBytes()

Returns a 16 byte representation of a type 1 UUID (a time-based UUID), based on the current system time.

Returns:

a type 1 UUID represented as a byte[]

minTimeUUID

public static java.util.UUID minTimeUUID(long timestamp)

Returns the smaller possible type 1 UUID having the provided timestamp. Warning: this method should only be used for querying as this doesn't at all guarantee the uniqueness of the resulting UUID.

maxTimeUUID

public static java.util.UUID maxTimeUUID(long timestamp)

Returns the biggest possible type 1 UUID having the provided timestamp. Warning: this method should only be used for querying as this doesn't at all guarantee the uniqueness of the resulting UUID.

unixTimestamp

public static long unixTimestamp(java.util.UUID uuid)

Parameters:

uuid -

Returns:

milliseconds since Unix epoch

unixTimestampInSec

public static int unixTimestampInSec(java.util.UUID uuid)

Parameters:

uuid -

Returns:

seconds since Unix epoch

microsTimestamp

public static long microsTimestamp(java.util.UUID uuid)

Parameters:

uuid -

Returns:

microseconds since Unix epoch

getTimeUUIDBytes

public static byte[] getTimeUUIDBytes(long timeMillis,
                                      int nanos)

Converts a 100-nanoseconds precision timestamp into the 16 byte representation of a type 1 UUID (a time-based UUID). To specify a 100-nanoseconds precision timestamp, one should provide a milliseconds timestamp and a number 0 <= n < 10000 such that n*100 is the number of nanoseconds within that millisecond.

Warning: This method is not guaranteed to return unique UUIDs; Multiple invocations using identical timestamps will result in identical UUIDs.

Returns:

a type 1 UUID represented as a byte[]

getAdjustedTimestamp

public static long getAdjustedTimestamp(java.util.UUID uuid)

Returns a milliseconds-since-epoch value for a type-1 UUID.

Parameters:

uuid - a type-1 (time-based) UUID

Returns:

the number of milliseconds since the unix epoch

Throws:

java.lang.IllegalArgumentException - if the UUID is not version 1