Crate ferroid

Expand description

§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

Platform	Timestamp Bits	Machine ID Bits	Sequence Bits	Epoch
Twitter	41	10	12	2010-11-04 01:42:54.657
Discord	42	10	12	2015-01-01 00:00:00.000
Instagram	41	13	10	2011-01-01 00:00:00.000
Mastodon	48	0	16	1970-01-01 00:00:00.000

§Ulid

Platform	Timestamp Bits	Random Bits	Epoch
ULID	48	80	1970-01-01 00:00:00.000

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

§🔧 Generator Comparison

Generator	Thread-Safe	Lock-Free	Throughput	Use Case
`BasicSnowflakeGenerator`	❌	❌	Highest	Sharded / single-threaded
`LockSnowflakeGenerator`	✅	❌	Medium	Fair multithreaded access
`AtomicSnowflakeGenerator`	✅	✅	High	Fast concurrent generation (less fair)
`BasicUlidGenerator`	✅	⚠️	Lower	Scalable, zero-coordination ULID generation

[⚠️]: 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

Generator	Time per IDs	Throughput
BasicSnowflakeGenerator	~2.8 ns	~353M IDs/sec
LockSnowflakeGenerator	~8.9 ns	~111M IDs/sec
AtomicSnowflakeGenerator	~3.1 ns	~320M IDs/sec
BasicUlidGenerator	~22.9 ns	~43M IDs/sec

§Async (Tokio Runtime)

Generator	Generators	Time per 4M IDs	Throughput
LockSnowflakeGenerator	1024	~6.95 ms	~604M IDs/sec
AtomicSnowflakeGenerator	1024	~3.82 ms	~1.09B IDs/sec
BasicUlidGenerator	128	~17.3 ms	~242M IDs/sec

§Async (Smol Runtime)

Generator	Generators	Time per 4M IDs	Throughput
LockSnowflakeGenerator	1024	~8.10 ms	~517M IDs/sec
AtomicSnowflakeGenerator	512	~4.31 ms	~973M IDs/sec
BasicUlidGenerator	128	~14.3 ms	~294M IDs/sec

To run all benchmarks:

cargo criterion --all-features

§🧪 Testing

Run all tests with:

cargo test --all-features

§📄 License

Licensed under either of:

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.

Macros§

define_snowflake_id: Field Ordering Semantics
define_ulid: Declares a Ulid-compatible type with custom timestamp and random bit layouts.

Structs§

AtomicSnowflakeGenerator: A lock-free Snowflake ID generator suitable for multi-threaded environments.
BasicSnowflakeGenerator: A non-concurrent Snowflake ID generator suitable for single-threaded environments.
BasicUlidGenerator: A ULID-style ID generator suitable for single- or multi-threaded environments.
LockSnowflakeGenerator: A lock-based Snowflake ID generator suitable for multi-threaded environments.
MonotonicClock: A monotonic time source that returns elapsed time since process start, offset from a user-defined epoch.
SmolSleep: An implementation of SleepProvider using Smol’s timer.
SmolSleepFuture: Internal future returned by SmolSleep::sleep_for.
SmolYield: An implementation of SleepProvider using Smol’s yield.
SnowflakeDiscordId: A 64-bit Snowflake ID using the Discord layout
SnowflakeGeneratorFuture: A future that polls a SnowflakeGenerator until it is ready to produce an ID.
SnowflakeInstagramId: A 64-bit Snowflake ID using the Instagram layout
SnowflakeLongId: A 128-bit Snowflake ID using a hybrid layout.
SnowflakeMastodonId: A 64-bit Snowflake ID using the Mastodon layout
SnowflakeTwitterId: A 64-bit Snowflake ID using the Twitter layout
ThreadRandom: A RandSource that uses the thread-local RNG (rand::thread_rng()).
TokioSleep: An implementation of SleepProvider using Tokio’s timer.
TokioYield: An implementation of SleepProvider using Tokio’s yield.
ULID: A 128-bit Ulid using the ULID layout
UlidGeneratorFuture: A future that polls a UlidGenerator until it is ready to produce an ID.

Enums§

Error
IdGenStatus: Represents the result of attempting to generate a new Snowflake ID.

Constants§

CUSTOM_EPOCH: Custom epoch: Wednesday, January 1, 2025 00:00:00 UTC
DISCORD_EPOCH: Discord epoch: Thursday, January 1, 2015 00:00:00 UTC
INSTAGRAM_EPOCH: Instagram epoch: Saturday, January 1, 2011 00:00:00 UTC
MASTODON_EPOCH: Mastodon epoch: Thursday, January 1, 1970 00:00:00 UTC
TWITTER_EPOCH: Twitter epoch: Thursday, November 4, 2010 1:42:54.657 UTC

Traits§

Base32Ext: A trait for types that can be encoded to and decoded from base32 (crockford) strings.
BeBytes: A trait for types that can be encoded to and decoded from big-endian bytes.
Id
RandSource: A trait for random sources that return a random byte integers.
SleepProvider: A trait that abstracts over how to sleep for a given Duration in async contexts.
Snowflake: A trait representing a layout-compatible Snowflake ID generator.
SnowflakeGenerator: A minimal interface for generating Snowflake IDs
SnowflakeGeneratorAsyncExt: Extension trait for asynchronously generating Snowflake IDs.
SnowflakeGeneratorAsyncSmolExt: Extension trait for asynchronously generating Snowflake IDs using the smol async runtime.
SnowflakeGeneratorAsyncTokioExt: Extension trait for asynchronously generating Snowflake IDs using the tokio async runtime.
TimeSource: A trait for time sources that return a monotonic or wall-clock timestamp.
ToU64: Trait for converting numeric-like values into a u64.
Ulid: Trait for layout-compatible ULID-style identifiers.
UlidGenerator: A minimal interface for generating Ulid IDs
UlidGeneratorAsyncExt: Extension trait for asynchronously generating ULIDs.
UlidGeneratorAsyncSmolExt: Extension trait for asynchronously generating ULIDs using the smol async runtime.
UlidGeneratorAsyncTokioExt: Extension trait for asynchronously generating ULIDs using the tokio async runtime.

Type Aliases§

Result

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