Exception on empty input

[Alezy80]

When input is empty array/span all hashes throws an exception.

var bytes = new byte[0];
var hash = xxHash3.ComputeHash(bytes, bytes.Length); //exception

var span = bytes.AsSpan();
var hash2 = xxHash3.ComputeHash(span, span.Length); //exception

In all hash functions must be guard clause like this

if (data.Length == 0)
    return ComputeEmptyHash(seed);
...
private static unsafe uint ComputeEmptyHash(uint seed)
{
    var pData = stackalloc byte[1]; //doesn't work with zero
    return UnsafeComputeHash(pData, 0, seed);
}

[Alezy80]

Another variant is to delegate all work to ReadOnlySpan version (Span overload is excessive) and get reference as

fixed (byte* pData = &MemoryMarshal.GetReference(data))
{
    return UnsafeComputeHash(pData, data.Length, seed);
}