Struct AtomicMonoUlidGenerator 

pub struct AtomicMonoUlidGenerator<ID, T, R>
where
    ID: UlidId<Ty = u128>,
    T: TimeSource<ID::Ty>,
    R: RandSource<ID::Ty>,
{ /* private fields */ }

Available on crate feature ulid and crate feature atomic and target_has_atomic=128 only.

A lock-free monotonic ULID-style ID generator suitable for single-threaded environments.

This generator stores the ULID in an AtomicU128, allowing safe shared use across threads.

Features

• ✅ Thread-safe
• ✅ Probabilistically unique (no coordination required)
• ✅ Time-ordered (monotonically increasing per millisecond)

Caveats

This implementation uses an AtomicU128 internally, so it only supports ID layouts where the underlying type is u128. You cannot use layouts with larger or smaller representations (i.e., ID::Ty must be u128).

Recommended When

• You’re in a multi-threaded environment
• You need require monotonically increasing IDs (ID generated within the same millisecond increment a sequence counter)

See Also

• BasicUlidGenerator
• BasicMonoUlidGenerator
• LockMonoUlidGenerator

Implementations

impl<ID, T, R> AtomicMonoUlidGenerator<ID, T, R>

where ID: UlidId<Ty = u128>, T: TimeSource<ID::Ty>, R: RandSource<ID::Ty>,

pub fn new(time: T, rng: R) -> Self

Available on crate features snowflake or ulid only.

Creates a new AtomicMonoUlidGenerator with the provided time source and RNG.

Parameters

• time: A TimeSource used to retrieve the current timestamp
• rng: A RandSource used to generate random bits

Returns

A ready-to-use ULID generator suitable for producing unique, sortable IDs.

Example

use ferroid::{AtomicMonoUlidGenerator, IdGenStatus, ULID, MonotonicClock, ThreadRandom};

let generator = AtomicMonoUlidGenerator::new(MonotonicClock::default(), ThreadRandom::default());

let id: ULID = loop {
    match generator.next_id() {
        IdGenStatus::Ready { id } => break id,
        IdGenStatus::Pending { .. } => core::hint::spin_loop(),
    }
};

pub fn from_components( timestamp: ID::Ty, random: ID::Ty, time: T, rng: R, ) -> Self

Available on crate features snowflake or ulid only.

Creates a new ID generator from explicit component values.

This constructor is primarily useful for advanced use cases such as restoring state from persistent storage or controlling the starting point of the generator manually.

Parameters

• timestamp: The initial timestamp component (usually in milliseconds)
• machine_id: The machine or worker identifier
• sequence: The initial sequence number
• time: A TimeSource implementation used to fetch the current time

Returns

A new generator instance preloaded with the given state.

⚠️ Note

In typical use cases, you should prefer Self::new to let the generator initialize itself from the current time.

pub fn next_id(&self) -> IdGenStatus<ID>

Available on crate features snowflake or ulid only.

Generates a new ULID.

Internally calls Self::try_next_id and unwraps the result. This method will panic on error, so prefer the fallible version if you want explicit control over error handling.

Panics

This method currently has no fallible code paths, but may panic if an internal error occurs in future implementations. For explicitly fallible behavior, use Self::try_next_id instead.

Example

use ferroid::{AtomicMonoUlidGenerator, IdGenStatus, ULID, MonotonicClock, ThreadRandom};

let generator = AtomicMonoUlidGenerator::new(MonotonicClock::default(), ThreadRandom::default());

let id: ULID = loop {
    match generator.next_id() {
        IdGenStatus::Ready { id } => break id,
        IdGenStatus::Pending { .. } => std::thread::yield_now(),
    }
};

pub fn try_next_id(&self) -> Result<IdGenStatus<ID>>

Available on crate features snowflake or ulid only.

Attempts to generate a new ULID with fallible error handling.

Combines the current timestamp with a freshly generated random value to produce a unique identifier. Returns IdGenStatus::Ready on success.

Returns

• Ok(IdGenStatus::Ready { id }): A new ID is available
• Ok(IdGenStatus::Pending { yield_for }): The time to wait (in milliseconds) before trying again
• Err(_): infallible for this generator

Errors

• This method currently does not return any errors and always returns Ok. It is marked as fallible to allow for future extensibility

Example

use ferroid::{AtomicMonoUlidGenerator, IdGenStatus, ULID, ToU64, MonotonicClock, ThreadRandom};

let generator = AtomicMonoUlidGenerator::new(MonotonicClock::default(), ThreadRandom::default());

// Attempt to generate a new ID
let id: ULID = loop {
    match generator.try_next_id() {
        Ok(IdGenStatus::Ready { id }) => break id,
        Ok(IdGenStatus::Pending { yield_for }) => {
            std::thread::sleep(core::time::Duration::from_millis(yield_for.to_u64()));
        }
        Err(_) => unreachable!(),
    }
};

Trait Implementations

impl<ID, T, R> UlidGenerator<ID, T, R> for AtomicMonoUlidGenerator<ID, T, R>

where ID: UlidId<Ty = u128>, T: TimeSource<ID::Ty>, R: RandSource<ID::Ty>,

Available on crate features snowflake or ulid only.

type Err = Infallible

fn new(time: T, rng: R) -> Self

fn next_id(&self) -> IdGenStatus<ID>

Returns the next available ID

fn try_next_id(&self) -> Result<IdGenStatus<ID>, Self::Err>

A fallible version of Self::next_id that returns a Result.