ferroid

ferroid is a Rust crate for generating and parsing Snowflake and ULID identifiers.

Features

• 📌 Bit-level compatibility with major Snowflake and ULID formats
• 🧩 Pluggable clocks and RNGs via TimeSource and RandSource
• 🧵 Lock-free, lock-based, and single-threaded generators
• 📐 Custom layouts via define_snowflake_id! and define_ulid! macros
• 🔢 Crockford base32 support with base32 feature flag

📦 Supported Layouts

Snowflake

Ulid

ULIDs offer high-entropy, time-sortable IDs without coordination, but are not strictly monotonic.

🔧 Generator Comparison

[⚠️]: Uses thread-local RNG with no global locks, but not strictly lock-free in the atomic/CAS sense.

Snowflake IDs are always unique and strictly ordered. ULIDs are globally sortable but only monotonic per timestamp interval.

🚀 Usage

Generate an ID

Synchronous

Calling next_id() may yield Pending if the current sequence is exhausted. In that case, you can spin, yield, or sleep depending on your environment:

#[cfg(feature = "snowflake")]
{
    use ferroid::{MonotonicClock, TWITTER_EPOCH, BasicSnowflakeGenerator, SnowflakeTwitterId, IdGenStatus};

    let clock = MonotonicClock::with_epoch(TWITTER_EPOCH);
    let generator = BasicSnowflakeGenerator::new(0, clock);

    let id: SnowflakeTwitterId = loop {
        match generator.next_id() {
            IdGenStatus::Ready { id } => break id,
            IdGenStatus::Pending { yield_for } => {
                println!("Exhausted; wait for: {}ms", yield_for);
                core::hint::spin_loop();
                // Use `core::hint::spin_loop()` for single-threaded or per-thread generators.
                // Use `std::thread::yield_now()` when sharing a generator across multiple threads.
                // Use `std::thread::sleep(Duration::from_millis(yield_for.to_u64().unwrap())` to sleep.
            }
        }
    };
}

#[cfg(feature = "ulid")]
{
    use ferroid::{MonotonicClock, IdGenStatus, TWITTER_EPOCH, ThreadRandom, BasicUlidGenerator, ULID};

    let clock = MonotonicClock::with_epoch(TWITTER_EPOCH);
    let rand = ThreadRandom::default();
    let generator = BasicUlidGenerator::new(clock, rand);

    let id: ULID = match generator.next_id() {
        IdGenStatus::Ready { id } => id,
        IdGenStatus::Pending { .. } =>  unreachable!()
    };

    println!("Generated ID: {}", id);
}

Asynchronous

If you're in an async context (e.g., using Tokio or Smol), you can enable one of the following features:

• async-tokio
• async-smol

#[cfg(feature = "async-tokio")]
{
    use ferroid::{Result, MonotonicClock, MASTODON_EPOCH};

    #[tokio::main]
    async fn main() -> Result<()> {
        #[cfg(feature = "snowflake")]
        {
            use ferroid::{
                AtomicSnowflakeGenerator, SnowflakeMastodonId,
                SnowflakeGeneratorAsyncTokioExt
            };

            let clock = MonotonicClock::with_epoch(MASTODON_EPOCH);
            let generator = AtomicSnowflakeGenerator::new(0, clock);

            let id: SnowflakeMastodonId = generator.try_next_id_async().await?;
            println!("Generated ID: {}", id);
        }

        #[cfg(feature = "ulid")]
        {
            use ferroid::{ThreadRandom, UlidGeneratorAsyncTokioExt, BasicUlidGenerator, ULID};

            let clock = MonotonicClock::with_epoch(MASTODON_EPOCH);
            let rand = ThreadRandom::default();
            let generator = BasicUlidGenerator::new(clock, rand);

            let id: ULID = generator.try_next_id_async().await?;
            println!("Generated ID: {}", id);
        }
        Ok(())
    }
}

#[cfg(feature = "async-smol")]
{
    use ferroid::{Result, MonotonicClock, CUSTOM_EPOCH};

    fn main() -> Result<()> {
        smol::block_on(async {
            #[cfg(feature = "snowflake")]
            {
                use ferroid::{
                    AtomicSnowflakeGenerator, SnowflakeMastodonId,
                    SnowflakeGeneratorAsyncSmolExt
                };

                let clock = MonotonicClock::with_epoch(CUSTOM_EPOCH);
                let generator = AtomicSnowflakeGenerator::new(0, clock);

                let id: SnowflakeMastodonId = generator.try_next_id_async().await?;
                println!("Generated ID: {}", id);
            }

            #[cfg(feature = "ulid")]
            {
                use ferroid::{ThreadRandom, UlidGeneratorAsyncSmolExt, BasicUlidGenerator, ULID};

                let clock = MonotonicClock::with_epoch(CUSTOM_EPOCH);
                let rand = ThreadRandom::default();
                let generator = BasicUlidGenerator::new(clock, rand);

                let id: ULID = generator.try_next_id_async().await?;
                println!("Generated ID: {}", id);
            }

            Ok(())
        })
    }
}

Custom Layouts

To define a custom layouts, use the define_* macros:

#[cfg(feature = "snowflake")]
{
    use ferroid::{define_snowflake_id};

    // Example: a 64-bit Twitter-like ID layout
    //
    //  Bit Index:  63           63 62            22 21             12 11             0
    //              +--------------+----------------+-----------------+---------------+
    //  Field:      | reserved (1) | timestamp (41) | machine ID (10) | sequence (12) |
    //              +--------------+----------------+-----------------+---------------+
    //              |<----------- MSB ---------- 64 bits ----------- LSB ------------>|
    define_snowflake_id!(
        MyCustomId, u64,
        reserved: 1,
        timestamp: 41,
        machine_id: 10,
        sequence: 12
    );


    // Example: a 128-bit extended ID layout
    //
    //  Bit Index:  127                88 87            40 39             20 19             0
    //              +--------------------+----------------+-----------------+---------------+
    //  Field:      | reserved (40 bits) | timestamp (48) | machine ID (20) | sequence (20) |
    //              +--------------------+----------------+-----------------+---------------+
    //              |<------- HI 64 bits ------->|<--------------- LO 64 bits ------------->|
    //              |<----- MSB ------ LSB ----->|<----- MSB ------ 64 bits ----- LSB ----->|
    define_snowflake_id!(
        MyCustomLongId, u128,
        reserved: 40,
        timestamp: 48,
        machine_id: 20,
        sequence: 20
    );
}

#[cfg(feature = "ulid")]
{
    use ferroid::define_ulid;

    // Example: a 128-bit ULID using the Ulid layout
    //
    // - 0 bits reserved
    // - 48 bits timestamp
    // - 80 bits random
    //
    //  Bit Index:  127            80 79           0
    //              +----------------+-------------+
    //  Field:      | timestamp (48) | random (80) |
    //              +----------------+-------------+
    //              |<-- MSB -- 128 bits -- LSB -->|
    define_ulid!(
        MyULID, u128,
        reserved: 0,
        timestamp: 48,
        random: 80
    );
}

⚠️ Note: All four sections (reserved, timestamp, machine_id, and sequence) must be specified in the snowflake macro, even if a section uses 0 bits. reserved bits are always stored as zero and can be used for future expansion. Similarly, the ulid macro requries (reserved, timestamp, random) fields.

Behavior

Snowflake:

• If the clock advances: reset sequence to 0 → IdGenStatus::Ready
• If the clock is unchanged: increment sequence → IdGenStatus::Ready
• If the clock goes backward: return IdGenStatus::Pending
• If the sequence overflows: return IdGenStatus::Pending

Ulid:

• Always returns → IdGenStatus::Ready to have a Compatable API with Snowflake.

Serialize as padded string

Use .to_padded_string() or .encode() for sortable string representations:

#[cfg(feature = "snowflake")]
{
    use ferroid::{Snowflake, SnowflakeTwitterId};

    let id = SnowflakeTwitterId::from(123456, 1, 42);
    println!("default: {id}");
    // > default: 517811998762

    println!("padded: {}", id.to_padded_string());
    // > padded: 00000000517811998762

    #[cfg(feature = "base32")]
    {
        use ferroid::Base32Ext;

        let encoded = id.encode();
        println!("base32: {encoded}");
        // > base32: 00000Y4G0082M

        let decoded = SnowflakeTwitterId::decode(&encoded).expect("decode should succeed");
        assert_eq!(id, decoded);
    }
}

#[cfg(feature = "ulid")]
{
    use ferroid::{Ulid, ULID};

    let id = ULID::from(123456, 42);
    println!("default: {id}");
    // > default: 149249145986343659392525664298

    println!("padded: {}", id.to_padded_string());
    // > padded: 000000000149249145986343659392525664298
    #[cfg(feature = "base32")]
    {
        use ferroid::Base32Ext;

        let encoded = id.encode();
        println!("base32: {encoded}");
        // > base32: 000000F2800000000000000058

        let decoded = ULID::decode(&encoded).expect("decode should succeed");
        assert_eq!(id, decoded);
    }
}

📈 Benchmarks

Snowflake ID generation is theoretically capped by:

max IDs/sec = 2^sequence_bits × 1000ms

For example, Twitter-style IDs (12 sequence bits) allow:

4096 IDs/ms × 1000 ms/sec = ~4M IDs/sec

To benchmark this, we generate IDs in chunks of 4096, which aligns with the sequence limit per millisecond.

• Sync Snowflake: Benchmarks the hot path without yielding to the clock.
• Async Snowflake: Also uses 4096-ID batches, but may yield (sequence exhaustion/CAS failure) or await due to task scheduling, reducing throughput.
• ULID: Benchmarked using the same chunk size, but performance is primarily limited by random number generation, not sequence or clock behavior.

Tests were ran on an M1 Macbook Pro 14", 32GB, 10 cores (8 perf, 2 efficiency).

Synchronous Generators

Async (Tokio Runtime)

Async (Smol Runtime)

To run all benchmarks:

cargo criterion --all-features

🧪 Testing

Run all tests with:

cargo test --all-features

📄 License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT License (LICENSE-MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.