AI-Studio/app/SharedTools/FNVHash.cs

// ReSharper disable MemberCanBePrivate.Global
namespace SharedTools;

/// <summary>
/// Implements the Fowler–Noll–Vo hash function for 32-bit and 64-bit hashes.
/// </summary>
public static class FNVHash
{
    private const uint FNV_OFFSET_BASIS_32_BIT = 2_166_136_261;
    private const ulong FNV_OFFSET_BASIS_64_BIT = 14_695_981_039_346_656_037;
    
    private const uint FNV_PRIME_32_BIT = 16_777_619;
    private const ulong FNV_PRIME_64_BIT = 1_099_511_628_211;

    /// <summary>
    /// Computes the 32bit FNV-1a hash of a string.
    /// </summary>
    /// <param name="text">The string to hash.</param>
    /// <returns>The 32bit FNV-1a hash of the string.</returns>
    public static uint ToFNV32(this string text) => ToFNV32(text.AsSpan());

    /// <summary>
    /// Computes the 32bit FNV-1a hash of a string.
    /// </summary>
    /// <param name="text">The string to hash.</param>
    /// <returns>The 32bit FNV-1a hash of the string.</returns>
    public static uint ToFNV32(this ReadOnlySpan<char> text)
    {
        var hash = FNV_OFFSET_BASIS_32_BIT;
        foreach (var c in text)
        {
            hash ^= c;
            hash *= FNV_PRIME_32_BIT;
        }

        return hash;
    }
    
    /// <summary>
    /// Computes the 64bit FNV-1a hash of a string.
    /// </summary>
    /// <param name="text">The string to hash.</param>
    /// <returns>The 64bit FNV-1a hash of the string.</returns>
    public static ulong ToFNV64(this string text) => ToFNV64(text.AsSpan());
    
    /// <summary>
    /// Computes the 64bit FNV-1a hash of a string.
    /// </summary>
    /// <param name="text">The string to hash.</param>
    /// <returns>The 64bit FNV-1a hash of the string.</returns>
    public static ulong ToFNV64(this ReadOnlySpan<char> text)
    {
        var hash = FNV_OFFSET_BASIS_64_BIT;
        foreach (var c in text)
        {
            hash ^= c;
            hash *= FNV_PRIME_64_BIT;
        }

        return hash;
    }
}