FNV-1a

FNV-1a hash algorithm in C#

This small project is an implementation of the FNV-1a hash algorithm for 32-, 64-, 128-, 256-, 512- and 1024-bit variants. All implemented classes descend from the System.IO.Hashing's NonCryptographicHashAlgorithm, which should make for easy adoption.

Example:

namespace Fnv1aTest
{
    using System;
    using System.Globalization;
    using System.IO.Hashing;
    using System.Text;
    
    using Fnv1a;
    
    public static class Program
    {
        public static void Main()
        {
            NonCryptographicHashAlgorithm alg = new Fnv1a64();

            alg.Append(Encoding.UTF8.GetBytes("foobar"));
            Console.WriteLine(((ulong)BitConverter.ToInt64(alg.GetCurrentHash(), 0)).ToString("X8", CultureInfo.InvariantCulture));
        }
    }
}

This will output 85944171F73967E8 as the FNV-1A 64-bit hash of the string "foobar".

Benchmark Results

BenchmarkDotNet v0.15.6, Linux Ubuntu 24.04.3 LTS (Noble Numbat)
AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores
.NET SDK 10.0.100
  [Host]     : .NET 10.0.0 (10.0.0, 10.0.25.52411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.0 (10.0.0, 10.0.25.52411), X64 RyuJIT x86-64-v3

Method	Mean	Error	StdDev
Fnv1A32	179.9 μs	0.07 μs	0.06 μs
Fnv1A64	150.0 μs	0.04 μs	0.03 μs
Fnv1A128	1,189.1 μs	24.71 μs	72.85 μs
Fnv1A256	5,621.3 μs	4.06 μs	3.39 μs
Fnv1A512	19,311.2 μs	20.70 μs	18.35 μs
Fnv1A1024	88,004.9 μs	841.03 μs	786.70 μs

Special thanks to crookseta for the missing-values project which allowed for the 256- and 512-bit variants to not have to use BigInteger, which was very slow.