A Rust implementation of the proposed UUID Version 7
```rust let uuid = uuid7::uuid7(); println!("{uuid}"); // e.g. "01809424-3e59-7c05-9219-566f82fff672" println!("{:?}", uuid.as_bytes()); // as 16-byte big-endian array
let uuidstring: String = uuid7::uuid7().tostring(); ```
See draft-ietf-uuidrev-rfc4122bis-03.
This implementation produces identifiers with the following bit layout:
text
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 | counter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|var| counter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| rand |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
unix_ts_ms field is dedicated to the Unix timestamp in
milliseconds.ver field is set at 0111.counter field accommodates a counter that ensures the increasing
order of IDs generated within a millisecond. The counter is incremented by one
for each new ID and is reset to a random number when the unix_ts_ms changes.var field is set at 10.rand bits are filled with a cryptographically strong random
number.The 42-bit counter is sufficiently large, so you do not usually need to worry
about overflow, but in an extremely rare circumstance where it overflows, this
library increments the unix_ts_ms field. As a result, the unix_ts_ms may
have a greater value than that of the system's real-time clock.
UUIDv7, by design, heavily relies on the system's wall clock to guarantee the
monotonically increasing order of generated IDs. A generator may not be able to
produce a monotonic sequence if the system clock goes backwards. This library
ignores a clock rollback and freezes the previously used unix_ts_ms unless the
clock rollback is considered significant (by default, ten seconds or more). If
such a significant rollback takes place, this library resets the generator and
thus breaks the monotonic order of generated IDs.
Default features:
std enables the primary uuid7() function. Without std, this crate
provides limited functionality available under no_std environments.Optional features:
serde enables the serialization and deserialization of Uuid objects.uuid (together with std) enables the new_v7() function that returns the
popular uuid crate's Uuid objects.This library also supports the generation of UUID version 4:
rust
let uuid = uuid7::uuid4();
println!("{uuid}"); // e.g. "2ca4b2ce-6c13-40d4-bccf-37d222820f6f"
V7Generator provides an interface that allows finer control over the various
aspects of the UUIDv7 generation:
```rust use uuid7::V7Generator;
let mut g = V7Generator::new(rand::rngs::OsRng); let customunixtsms = 0x012345678901u64; let x = g.generateorresetcore(customunixtsms, 10000); println!("{x}");
let y = g .generateorabortcore(customunixtsms, 10000) .expect("clock went backwards by 10000 milliseconds or more"); println!("{y}"); ```
Licensed under the Apache License, Version 2.0.