Crate unique_id

A trait and implementations for unique ID generators.

This crate provides four simple traits, starting with Generator. This will return successive unique identifiers, the only requirement of an identifier being that it implements PartialEq.

Each implemented generator is in its own feature, by default all of which are included.

• Generator RandomGenerator, in feature random, provides a random number scheme returning u128 values. Depends on the uuid crate.
• Generator SequenceGenerator, in feature sequence, provides monotonically increasing u64 values in a thread safe manner. Depends on the atomic_refcell and lazy_static crates.
• Generator StringGenerator, in feature string, provides random string values. Depends on the blob-uuid crate.

Example

The following shows an example of the StringGenerator implementation.

use unique_id::Generator;
use unique_id::string::StringGenerator;

let gen = StringGenerator::default();
let mut last = gen.next_id();
for _ in 1..100_000 {
    let next = gen.next_id();
    assert_ne!(last, next);
    last = next;
}

Benchmarks

The cargo bench command will run a comparison benchmark to show the relative performance of all generators. This benchmark is in benches/compare.cs and uses Criterion for report generation.

$ cargo bench

    Finished bench [optimized] target(s) in 17.16s
     Running target/release/deps/unique_id-4944964a39587480

running 3 tests
test random::tests::test_something ... ignored
test sequence::tests::test_something ... ignored
test string::tests::test_something ... ignored

test result: ok. 0 passed; 0 failed; 3 ignored; 0 measured; 0 filtered out

     Running target/release/deps/compare-cfeb3571caa9de30
Compare Implementations/string
                        time:   [928.16 ns 1.0963 us 1.2829 us]
                        change: [+108.47% +224.51% +419.70%] (p = 0.00 < 0.05)
                        Performance has regressed.
Found 3 outliers among 100 measurements (3.00%)
  1 (1.00%) high mild
  2 (2.00%) high severe
Compare Implementations/integer
                        time:   [21.033 ns 21.434 ns 21.885 ns]
                        change: [-4.1097% +0.4756% +5.4467%] (p = 0.84 > 0.05)
                        No change in performance detected.
Found 4 outliers among 100 measurements (4.00%)
  2 (2.00%) high mild
  2 (2.00%) high severe
Compare Implementations/random
                        time:   [36.741 ns 38.285 ns 40.487 ns]
                        change: [-33.414% -24.047% -13.624%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
  2 (2.00%) high mild
  5 (5.00%) high severe

The output can be found in target/criterion/report/index.html.

License

This package and repository is licensed under the MIT license (see file ./LICENSE-MIT) and the Apache License, Version 2.0 (see ./LICENSE-APACHE) and the following:

Copyright 2025 Simon Johnston <johnstonskj@gmail.com>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Changes

Version 0.1.7

• Update the SequenceGenerator implementation from using the lazy_static macro to the standard library's LazyLock and remove the external dependency.

Version 0.1.6

• Relicensed under both MIT as well as Apache-2.0.
• Update dependency versions.

Version 0.1.5

• Simplified implementation of SequenceGenerator.
• Removed atomic_refcell dependency.

Version 0.1.4

• Updated dependencies for uuid and blob-uuid via dependabot.
• Removed PhantomData in generator structures.

Version 0.1.3

• Moved module-specific unit tests into a combined tests/unique.rs.
• Renamed integer to sequence in benchmarks.
• Added more to the documentation.

Version 0.1.2

• Added new RandomGenerator implementation.
• Put each implementation into its own feature.
• Added #[inline] to some functions.

Version 0.1.1

• Added trait GeneratorFromSeed and implementation for SequenceGenerator.
• Added a benchmark to compare the two current implementations.

Version 0.1.0

• Simple traits Generator, GeneratorWithInvalid, and GeneratorFromStr.
• StringGenerator using UUIDs
• SequenceGenerator using i64