uuid

func Must ¶

func Must(u UUID, err error) UUID

func NewV7 ¶

func NewV7() (UUID, error)

NewV7 This is an implementation of a UUIDv7-compatible ID generator. The reference used was the latest version of the draft IETF RFC4122bis specification at

https://www.ietf.org/archive/id/draft-ietf-uuidrev-rfc4122bis-14.html

The UUIDv7 bit layout is

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           unix_ts_ms                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          unix_ts_ms           |  ver  |       rand_a          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|var|                        rand_b                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            rand_b                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The fields are to be filled as follows:

1. unix_ts_ms: a 48-bit Unix millisecond timestamp.
2. ver: the 4-bit literal value 0b0111 (7) denoting the UUID version.
3. rand_a: a 12-bit pseudo-random value.
4. var: the 2-bit literal value 0b10 (2) denoting the UUID variant.
5. rand_b: a 62-bit pseudo-random value.

The specification allows for additional monotonicity guarantees within the millisecond by incrementing the value of rand_b by a random integer of any desired length for additional UUIDs generated within a single timestamp tick. This may become relevant in future. For now, we generate a new 74-bit pseudo-random value for every generated UUID.