Expand description

Serial (or auto-increment) integers make great unique identifers. They do not need to be large (i.e. using more memory) to prevent collisions and they are always unique until they reach their max value, mimicking the behavior of PostgreSQL’s SERIAL data type. Creating serial values has minimal performance impact because it relies on simple adding rather than hashing or randomizing.

This crate provides a generator (that is also an iterator) that outputs serial values. By default, any unsigned integer from the standard library can be generated. This is essentially a counter, a simple iterator for integers. This crate is appropriately tiny.

For safety and stability, the generator “saturates” the values instead of overflowing. This guarantees that the output values are unique to that generator (except for the greatest possible value, e.g. u8::MAX or u32::MAX).




A simple example.

let mut gen = SerialGenerator::<u32>::new();

assert_eq!(0, gen.generate());
assert_eq!(1, gen.generate());

Using the “serde_impl” feature

Serialize a generator with Serde.

let mut gen = SerialGenerator::<u8>::new();


let gen_string = toml::to_string(&gen).unwrap();

assert_eq!("value = 2\n", gen_string);

Deserialize a generator with Serde.

let gen = SerialGenerator::<u8>::new();
let gen_from_toml =
    toml::from_str::<SerialGenerator<u8>>("value = 0\n").unwrap();

assert_eq!(gen_from_toml, gen);

Using no_std

No feature flags are needed.


fn main() {
    let mut gen = SerialGenerator::<u8>::new();
    let serial_ids = [gen.generate(), gen.generate()];

    assert_eq!([0, 1], serial_ids);


A complex example showing the use of static and concurrency

fn main() {
    let users_mutex = Arc::new(Mutex::new(Vec::new()));
    let users_clone = Arc::clone(&users_mutex);

    let handle = thread::spawn(move || {
        let alice = User::new("alice@domain.xyz");
        let mary = User::new("mary@domain.xyz");
        let mut users = users_clone.lock().unwrap();



    let bob = User::new("bob@domain.xyz");
    let fred = User::new("fred@domain.xyz");
    let mut users = users_mutex.lock().unwrap();


    assert_eq!(0, users[0].id);
    assert_eq!(1, users[1].id);
    assert_eq!(2, users[2].id);
    assert_eq!(3, users[3].id);

lazy_static! {
    static ref USER_ID_GEN: Mutex<SerialGenerator>
        = Mutex::new(SerialGenerator::new());

struct User {
    id: u32,
    email: String,

impl User {
    pub fn new(email: &str) -> Self {
        User {
            id: USER_ID_GEN.lock().unwrap().generate(),
            email: email.to_string(),


A generator that creates instances of a Serial type.


Defines how a type is used by SerialGenerator.