A high-performance, fully compliant .NET implementation of ULIDs (Universally Unique Lexicographically Sortable Identifiers), adhering to the official ULID specification.

Table of Contents

• Introduction
• Features
• Installation
• Usage
• API
• Integration with Other Libraries
• Benchmarking
• Prior Art
• Contributing
• License

Introduction

ULIDs are universally unique, lexicographically sortable identifiers, ideal for distributed systems and time-ordered data due to their sortability and human-readability—advantages GUIDs lack. This library offers a robust, fully compliant .NET implementation, addressing limitations found in other ULID solutions.

This implementation addresses a potential OverflowException that can occur when generating multiple ULIDs within the same millisecond due to the "random" part overflowing. To ensure dependable, unique ULID generation, our solution increments the timestamp component upon random part overflow, eliminating such exceptions. This behavior aligns with discussions in ULID specification issue #39.

This library uniquely addresses the predictability of monotonic ULIDs generated within the same millisecond by allowing random increments to the random component. This mitigates enumeration attack vulnerabilities, as discussed in ULID specification issue #105. You can configure the random increment with a random value ranging from 1-byte (1–256) to 4-bytes (1–4,294,967,296), enhancing randomness while preserving lexicographical sortability.

For most modern systems, ULIDs offer a superior alternative to both GUIDs and integer IDs. While GUIDs provide uniqueness, they lack sortability and readability, impacting indexing and querying efficiency. Integer IDs are sortable but not universally unique, leading to potential conflicts in distributed environments. ULIDs combine universal uniqueness with lexicographical sortability, making them the optimal choice for scalable and efficient identifier generation in modern applications. This library provides a robust, reliable, and compliant ULID implementation, enabling your application to leverage these benefits without compromising performance or adherence to the official specification.

Features

• Universally Unique: Ensures global uniqueness across systems.
• Sortable: Lexicographically ordered for time-based sorting.
• Fast and Efficient: Optimized for high performance and low memory usage.
• Specification-Compliant: Fully adheres to the ULID specification.
• Interoperable: Includes conversion methods to and from GUIDs, Crockford's Base32 strings, and byte arrays.
• Ahead-of-Time (AoT) Compilation Compatible: Fully compatible with AoT compilation for improved startup performance and smaller binary sizes.
• Error-Free Generation: Prevents OverflowException by incrementing the timestamp component when the random part overflows, ensuring continuous unique ULID generation.

These features collectively make ByteAether.Ulid a robust and efficient choice for managing unique identifiers in your .NET applications.

Installation

Install the latest stable package via NuGet:

dotnet add package ByteAether.Ulid

To install a specific preview version, use the --version option:

dotnet add package ByteAether.Ulid --version <VERSION_NUMBER>

Usage

Here is a basic example of how to use the ULID implementation:

using System;
using ByteAether.Ulid;

// Create a new ULID
var ulid = Ulid.New();

// Convert to byte array and back
byte[] byteArray = ulid.ToByteArray();
var ulidFromByteArray = Ulid.New(byteArray);

// Convert to GUID and back
Guid guid = ulid.ToGuid();
var ulidFromGuid = Ulid.New(guid);

// Convert to string and back
string ulidString = ulid.ToString();
var ulidFromString = Ulid.Parse(ulidString);

Console.WriteLine($"ULID: {ulid}, GUID: {guid}, String: {ulidString}");

Advanced Generation

You can customize ULID generation by providing GenerationOptions. This allows you to control monotonicity and the source of randomness.

Example: Monotonic ULID with Random Increments

To generate ULIDs that are monotonically increasing with a random increment, you can specify the Monotonicity option.

using System;
using ByteAether.Ulid;
using static ByteAether.Ulid.Ulid.GenerationOptions;

// Configure options for a 2-byte random increment
var options = new Ulid.GenerationOptions
{
	Monotonicity = MonotonicityOptions.MonotonicRandom2Byte
};

// Generate a ULID with the specified options
var ulid = Ulid.New(options);

Console.WriteLine($"ULID with random increment: {ulid}");

Example: Setting Default Generation Options

You can set default generation options for the entire application. This is useful for consistently applying specific behaviors, such as prioritizing performance over cryptographic security.

using System;
using ByteAether.Ulid;
using static ByteAether.Ulid.Ulid.GenerationOptions;

// Set default generation options for the entire application
Ulid.DefaultGenerationOptions = new()
{
	Monotonicity = MonotonicityOptions.MonotonicIncrement,
	InitialRandomSource = new PseudoRandomProvider(),
	IncrementRandomSource = new PseudoRandomProvider()
};

// Now, any subsequent call to Ulid.New() will use these options
var ulid = Ulid.New();

Console.WriteLine($"ULID from pseudo-random source: {ulid}");

API

The Ulid implementation provides the following properties and methods:

Creation

• Ulid.New(GenerationOptions? options = null)
  Generates a new ULID using default generation options. Accepts an optional GenerationOptions parameter to customize the generation behavior.
• Ulid.New(DateTimeOffset dateTimeOffset, GenerationOptions? options = null)
  Generates a new ULID using the specified DateTimeOffset and default generation options. Accepts an optional GenerationOptions parameter to customize the generation behavior.
• Ulid.New(long timestamp, GenerationOptions? options = null)
  Generates a new ULID using the specified Unix timestamp in milliseconds (long) and default generation options. Accepts an optional GenerationOptions parameter to customize the generation behavior.
• Ulid.New(DateTimeOffset dateTimeOffset, ReadOnlySpan<byte> random)
  Generates a new ULID using the specified DateTimeOffset and a pre-existing random byte array.
• Ulid.New(long timestamp, ReadOnlySpan<byte> random)
  Generates a new ULID using the specified Unix timestamp in milliseconds (long) and a pre-existing random byte array.
• Ulid.New(ReadOnlySpan<byte> bytes)
  Creates a ULID from an existing byte array.
• Ulid.New(Guid guid)
  Create from existing Guid.

Checking Validity

• Ulid.IsValid(string ulidString)
  Validates if the given string is a valid ULID.
• Ulid.IsValid(ReadOnlySpan<char> ulidString)
  Validates if the given span of characters is a valid ULID.
• Ulid.IsValid(ReadOnlySpan<byte> ulidBytes)
  Validates if the given byte array represents a valid ULID.

Parsing

• Ulid.Parse(ReadOnlySpan<char> chars, IFormatProvider? provider = null)
  Parses a ULID from a character span in canonical format. The IFormatProvider is ignored.
• Ulid.TryParse(ReadOnlySpan<char> s, IFormatProvider? provider, out Ulid result)
  Tries to parse a ULID from a character span in canonical format. Returns true if successful.
• Ulid.Parse(string s, IFormatProvider? provider = null)
  Parses a ULID from a string in canonical format. The IFormatProvider is ignored.
• Ulid.TryParse(string? s, IFormatProvider? provider, out Ulid result)
  Tries to parse a ULID from a string in canonical format. Returns true if successful.

Properties

• Ulid.Empty
  Represents an empty ULID, equivalent to default(Ulid) and Ulid.New(new byte[16]).
• Ulid.DefaultGenerationOptions
  Default configuration for ULID generation when no options are provided by the Ulid.New(...) call.
• .Time
  Gets the timestamp component of the ULID as a DateTimeOffset.
• .TimeBytes
  Gets the time component of the ULID as a ReadOnlySpan<byte>.
• .Random
  Gets the random component of the ULID as a ReadOnlySpan<byte>.

Conversion Methods

• .AsByteSpan()
  Provides a ReadOnlySpan<byte> representing the contents of the ULID.
• .ToByteArray()
  Converts the ULID to a byte array.
• .ToGuid()
  Converts the ULID to a Guid.
• .ToString(string? format = null, IFormatProvider? formatProvider = null)
  Converts the ULID to a canonical string representation. Format arguments are ignored.

Comparison Operators

• Supports all comparison operators:
  ==, !=, <, <=, >, >=.
• Implements standard comparison and equality methods:
  CompareTo, Equals, GetHashCode.
• Provides implicit operators to and from Guid.

GenerationOptions

The GenerationOptions class provides detailed configuration for ULID generation, with the following key properties:

• Monotonicity
  Controls the behavior of ULID generation when multiple identifiers are created within the same millisecond. It determines whether ULIDs are strictly increasing or allow for random ordering within that millisecond. Available options include: NonMonotonic, MonotonicIncrement (default), MonotonicRandom1Byte, MonotonicRandom2Byte, MonotonicRandom3Byte, MonotonicRandom4Byte.

• InitialRandomSource
  An IRandomProvider for generating the random bytes of a ULID. The default CryptographicallySecureRandomProvider ensures robust, unpredictable ULIDs using a cryptographically secure generator.

• IncrementRandomSource
  An IRandomProvider that provides randomness for monotonic random increments. The default PseudoRandomProvider is a faster, non-cryptographically secure source optimized for this specific purpose.

This library comes with two default IRandomProvider implementations:

• CryptographicallySecureRandomProvider
  Utilizes System.Security.Cryptography.RandomNumberGenerator for high-quality, cryptographically secure random data.
• PseudoRandomProvider
  A faster, non-cryptographically secure option based on System.Random, ideal for performance-critical scenarios where cryptographic security is not required for random increments.

Custom IRandomProvider implementations can also be created.

Integration with Other Libraries

ASP.NET Core

Supports seamless integration as a route or query parameter with built-in TypeConverter.

System.Text.Json (.NET 5.0+)

Includes a JsonConverter for easy serialization and deserialization.

EF Core Integration

To use ULIDs as primary keys or properties in Entity Framework Core, you can create a custom ValueConverter to handle the conversion between Ulid and byte[]. Here's how to do it:

1. Create a custom ValueConverter to convert Ulid to byte[] and vice versa:

public class UlidToBytesConverter : ValueConverter<Ulid, byte[]>
{
	private static readonly ConverterMappingHints DefaultHints = new(size: 16);

	public UlidToBytesConverter() : this(defaultHints) { }

	public UlidToBytesConverter(ConverterMappingHints? mappingHints = null) : base(
		convertToProviderExpression: x => x.ToByteArray(),
		convertFromProviderExpression: x => Ulid.New(x),
		mappingHints: defaultHints.With(mappingHints)
	)
	{ }
}

2. Register the Converter in ConfigureConventions

Once the converter is created, you need to register it in your DbContext's ConfigureConventions virtual method to apply it to Ulid properties:

protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
{
	// ...
	configurationBuilder
		.Properties<Ulid>()
		.HaveConversion<UlidToBytesConverter>();
	// ...
}

Dapper Integration

To use ULIDs with Dapper, you can create a custom TypeHandler to convert between Ulid and byte[]. Here's how to set it up:

1. Create the ULID Type Handler

using Dapper;
using System.Data;

public class UlidTypeHandler : SqlMapper.TypeHandler<Ulid>
{
	public override void SetValue(IDbDataParameter parameter, Ulid value)
	{
		parameter.Value = value.ToByteArray();
	}

	public override Ulid Parse(object value)
	{
		return Ulid.New((byte[])value);
	}
}

2. Register the Type Handler

After creating the UlidTypeHandler, you need to register it with Dapper. You can do this during application startup (e.g., in the Main method or ConfigureServices for ASP.NET Core).

Dapper.SqlMapper.AddTypeHandler(new UlidTypeHandler());

MessagePack Integration

To use ULIDs with MessagePack, you can create a custom MessagePackResolver to handle the serialization and deserialization of Ulid as byte[]. Here's how to set it up:

1. Create the Custom Formatter

First, create a custom formatter for Ulid to handle its conversion to and from byte[]:

using MessagePack;
using MessagePack.Formatters;

public class UlidFormatter : IMessagePackFormatter<Ulid>
{
	public Ulid Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options)
	{
		var bytes = reader.ReadByteArray();
		return Ulid.New(bytes);
	}

	public void Serialize(ref MessagePackWriter writer, Ulid value, MessagePackSerializerOptions options)
	{
		writer.Write(value.ToByteArray());
	}
}

2. Register the Formatter

Once the UlidFormatter is created, you need to register it with the MessagePackSerializer to handle the Ulid type.

MessagePack.Resolvers.CompositeResolver.Register(
	new IMessagePackFormatter[] { new UlidFormatter() },
	MessagePack.Resolvers.StandardResolver.GetFormatterWithVerify<Ulid>()
);

Alternatively, you can register the formatter globally when configuring MessagePack options:

MessagePackSerializer.DefaultOptions = MessagePackSerializer.DefaultOptions
	.WithResolver(MessagePack.Resolvers.CompositeResolver.Create(
		new IMessagePackFormatter[] { new UlidFormatter() },
		MessagePack.Resolvers.StandardResolver.Instance
	));

Newtonsoft.Json Integration

To use ULIDs with Newtonsoft.Json, you need to create a custom JsonConverter to handle the serialization and deserialization of ULID values. Here's how to set it up:

1. Create the Custom JsonConverter

First, create a custom JsonConverter for Ulid to serialize and deserialize it as a string:

using Newtonsoft.Json;
using System;

public class UlidJsonConverter : JsonConverter<Ulid>
{
	public override Ulid ReadJson(JsonReader reader, Type objectType, Ulid existingValue, bool hasExistingValue, JsonSerializer serializer)
	{
		var value = (string)reader.Value;
		return Ulid.Parse(value);
	}

	public override void WriteJson(JsonWriter writer, Ulid value, JsonSerializer serializer)
	{
		writer.WriteValue(value.ToString());
	}
}

2. Register the JsonConverter

Once the UlidJsonConverter is created, you need to register it with Newtonsoft.Json to handle Ulid serialization and deserialization. You can register the converter globally when configuring your JSON settings:

using Newtonsoft.Json;
using System.Collections.Generic;

JsonConvert.DefaultSettings = () => new JsonSerializerSettings
{
	Converters = new List<JsonConverter> { new UlidJsonConverter() }
};

Alternatively, you can specify the converter explicitly in individual serialization or deserialization calls:

var settings = new JsonSerializerSettings();
settings.Converters.Add(new UlidJsonConverter());

var json = JsonConvert.SerializeObject(myObject, settings);
var deserializedObject = JsonConvert.DeserializeObject<MyObject>(json, settings);

Benchmarking

Benchmarking was performed using BenchmarkDotNet to demonstrate the performance and efficiency of this ULID implementation. Comparisons include NetUlid 2.1.0, Ulid 1.3.4, NUlid 1.7.3, and Guid for overlapping functionalities like creation, parsing, and byte conversions.

Benchmark scenarios also include comparisons against Guid, where functionality overlaps, such as creation, parsing, and byte conversions.

Note:

• ByteAetherUlidR1Bc & ByteAetherUlidR4Bc are configured to use a cryptographically secure random increment of 1 byte and 4 bytes, respectively, during monotonic ULID generation.
• ByteAetherUlidR1Bp & ByteAetherUlidR4Bp are configured to use a pseudo-random increment of 1 byte and 4 bytes, respectively, during monotonic ULID generation.
• ByteAetherUlidP is configured to use a pseudo-random source for the random component during non-monotonic ULID generation.

The following benchmarks were performed:

BenchmarkDotNet v0.15.2, Windows 10 (10.0.19044.6216/21H2/November2021Update)
AMD Ryzen 7 3700X 3.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET SDK 9.0.304
  [Host]     : .NET 9.0.8 (9.0.825.36511), X64 RyuJIT AVX2
  DefaultJob : .NET 9.0.8 (9.0.825.36511), X64 RyuJIT AVX2

Job=DefaultJob

| Type            | Method             | Mean        | Error     | Gen0   | Allocated |
|---------------- |------------------- |------------:|----------:|-------:|----------:|
| Generate        | ByteAetherUlid     |  49.8213 ns | 0.9882 ns |      - |         - |
| Generate        | ByteAetherUlidR1Bp |  57.9895 ns | 1.1243 ns |      - |         - |
| Generate        | ByteAetherUlidR4Bp |  61.2364 ns | 1.1938 ns |      - |         - |
| Generate        | ByteAetherUlidR1Bc | 103.1759 ns | 2.0739 ns |      - |         - |
| Generate        | ByteAetherUlidR4Bc | 110.4977 ns | 2.0647 ns |      - |         - |
| Generate        | NetUlid *(1)       | 173.9626 ns | 3.4647 ns | 0.0095 |      80 B |
| Generate        | NUlid *(2)         |  63.4684 ns | 1.2116 ns |      - |         - |

| GenerateNonMono | ByteAetherUlid     | 100.3030 ns | 1.9431 ns |      - |         - |
| GenerateNonMono | ByteAetherUlidP    |  48.5570 ns | 0.9774 ns |      - |         - |
| GenerateNonMono | Ulid *(3,4)        |  45.5564 ns | 0.3956 ns |      - |         - |
| GenerateNonMono | NUlid              | 102.3512 ns | 2.0692 ns |      - |         - |
| GenerateNonMono | Guid *(5)          |  50.4565 ns | 0.9795 ns |      - |         - |
| GenerateNonMono | GuidV7 *(3,5)      |  85.8855 ns | 1.7043 ns |      - |         - |

| FromByteArray   | ByteAetherUlid     |   0.0132 ns | 0.0166 ns |      - |         - |
| FromByteArray   | NetUlid            |   0.7006 ns | 0.0280 ns |      - |         - |
| FromByteArray   | Ulid               |   7.2749 ns | 0.1728 ns |      - |         - |
| FromByteArray   | NUlid              |   2.0677 ns | 0.0350 ns |      - |         - |
| FromByteArray   | Guid               |   0.0096 ns | 0.0098 ns |      - |         - |

| FromGuid        | ByteAetherUlid     |   1.4945 ns | 0.0241 ns |      - |         - |
| FromGuid        | NetUlid            |   5.1354 ns | 0.0806 ns | 0.0048 |      40 B |
| FromGuid        | Ulid               |   1.7319 ns | 0.0624 ns |      - |         - |
| FromGuid        | NUlid              |   4.3828 ns | 0.1125 ns |      - |         - |

| FromString      | ByteAetherUlid     |  15.6314 ns | 0.3041 ns |      - |         - |
| FromString      | NetUlid            |  27.8379 ns | 0.5770 ns |      - |         - |
| FromString      | Ulid               |  15.4837 ns | 0.3308 ns |      - |         - |
| FromString      | NUlid              |  63.1436 ns | 1.1317 ns | 0.0124 |     104 B |
| FromString      | Guid               |  23.5391 ns | 0.4718 ns |      - |         - |

| ToByteArray     | ByteAetherUlid     |   3.9866 ns | 0.1315 ns | 0.0048 |      40 B |
| ToByteArray     | NetUlid            |  10.5484 ns | 0.2627 ns | 0.0048 |      40 B |
| ToByteArray     | Ulid               |   4.0185 ns | 0.1314 ns | 0.0048 |      40 B |
| ToByteArray     | NUlid              |   7.0865 ns | 0.1908 ns | 0.0048 |      40 B |

| ToGuid          | ByteAetherUlid     |   0.3066 ns | 0.0361 ns |      - |         - |
| ToGuid          | NetUlid            |  12.7650 ns | 0.2810 ns | 0.0048 |      40 B |
| ToGuid          | Ulid               |   0.7936 ns | 0.0454 ns |      - |         - |
| ToGuid          | NUlid              |   0.2509 ns | 0.0286 ns |      - |         - |

| ToString        | ByteAetherUlid     |  20.1908 ns | 0.4528 ns | 0.0095 |      80 B |
| ToString        | NetUlid            |  26.1708 ns | 0.5517 ns | 0.0095 |      80 B |
| ToString        | Ulid               |  20.6022 ns | 0.4536 ns | 0.0095 |      80 B |
| ToString        | NUlid              |  28.4933 ns | 0.6250 ns | 0.0095 |      80 B |
| ToString        | Guid               |  13.2287 ns | 0.3185 ns | 0.0115 |      96 B |

| CompareTo       | ByteAetherUlid     |   0.0000 ns | 0.0000 ns |      - |         - |
| CompareTo       | NetUlid            |   3.3984 ns | 0.0210 ns |      - |         - |
| CompareTo       | Ulid               |   2.1589 ns | 0.0365 ns |      - |         - |
| CompareTo       | NUlid              |   9.6859 ns | 0.2093 ns | 0.0048 |      40 B |

| Equals          | ByteAetherUlid     |   0.0113 ns | 0.0110 ns |      - |         - |
| Equals          | NetUlid            |   0.9295 ns | 0.0461 ns |      - |         - |
| Equals          | Ulid               |   0.0000 ns | 0.0000 ns |      - |         - |
| Equals          | NUlid              |   0.0000 ns | 0.0000 ns |      - |         - |
| Equals          | Guid               |   0.0106 ns | 0.0117 ns |      - |         - |

| GetHashCode     | ByteAetherUlid     |   0.0029 ns | 0.0087 ns |      - |         - |
| GetHashCode     | NetUlid            |  10.2202 ns | 0.2350 ns |      - |         - |
| GetHashCode     | Ulid               |   0.0028 ns | 0.0095 ns |      - |         - |
| GetHashCode     | NUlid              |   8.2156 ns | 0.1880 ns |      - |         - |
| GetHashCode     | Guid               |   0.0434 ns | 0.0172 ns |      - |         - |

Existing competitive libraries exhibit various deviations from the official ULID specification or present drawbacks:

1. NetUlid: Only supports monotonicity within a single thread.
2. NUlid: Requires custom wrappers and state management for monotonic generation.
3. Ulid & GuidV7: Do not implement monotonicity.
4. Ulid: Utilizes a cryptographically non-secure XOR-Shift for random value generation, with only the initial seed being cryptographically secure.
5. Guid & GuidV7: The Guid documentation explicitly states that its random component may not be generated using a cryptographically secure random number generator (RNG), and that Guid values should not be used for cryptographic purposes.

Furthermore, both NetUlid and NUlid, despite offering monotonicity, are susceptible to OverflowException due to random-part overflow.

This implementation demonstrates performance comparable to or exceeding its closest competitors. Crucially, it provides the most complete adherence to the official ULID specification, ensuring superior reliability and robustness for your applications compared to other libraries.

Prior Art

Much of this implementation is either based on or inspired by existing works. This library is standing on the shoulders of giants.

• NetUlid
• Ulid
• NUlid
• Official ULID specification
• Crockford's Base32

Contributing

We welcome all contributions! You can:

• Open a Pull Request: Fork the repository, create a branch, make your changes, and submit a pull request to the main branch.
• Report Issues: Found a bug or have a suggestion? Open an issue with details.

Thank you for helping improve the project!

License

This project is licensed under the MIT License. See the LICENSE file for details.