A class that represents an immutable universally unique identifier (UUID).
A UUID represents a 128-bit value.
There exist different variants of these global identifiers. The methods
of this class are for manipulating the Leach-Salz variant, although the
constructors allow the creation of any variant of UUID (described below).
The layout of a variant 2 (Leach-Salz) UUID is as follows:
The most significant long consists of the following unsigned fields:
0xFFFFFFFF00000000 time_low
0x00000000FFFF0000 time_mid
0x000000000000F000 version
0x0000000000000FFF time_hi
The least significant long consists of the following unsigned fields:
0xC000000000000000 variant
0x3FFF000000000000 clock_seq
0x0000FFFFFFFFFFFF node
The variant field contains a value which identifies the layout of
the UUID. The bit layout described above is valid only for
a UUID with a variant value of 2, which indicates the
Leach-Salz variant.
The version field holds a value that describes the type of this
UUID. There are four different basic types of UUIDs: time-based,
DCE security, name-based, and randomly generated UUIDs. These types
have a version value of 1, 2, 3 and 4, respectively.
For more information including algorithms used to create UUIDs,
see
RFC 4122: A Universally Unique IDentifier (UUID) URN
Namespace, section 4.2 "Algorithms for Creating a Time-Based
UUID".