I should be including the version number as a string (enum) for diagnostic and printing purposes.

Also because I don't have to manually type it in version pages and the like.

Like

enum BLAKE2D_VERSION_STRING = "0.1.1";

While the Digest API uses std.digest.hmac.HMAC for HMAC, which adds a secret hashed key using the template API, the way BLAKE2 does is just... Weird.

At initiation:

• Parameter block index 0 byte 1 (little-endian) sets key size in bytes.
• Key is XOR'd with state alongside IV (ulong for b, uint for s, see the inner_t alias).

Which is simply not possible with the HMAC structure template. Unless there's a hack I don't know of.

Should be using std or core multi-threading functions.

Waiting on: #2

Options:

1. core.simd -- Supported everywhere, I think.
2. intel-intrinsics DUB package -- Somewhat supports all compilers.
3. Inlined assembly -- If all fails, at least x86 users would benefit. But limited to AVX/AV2 and not SSE* at best (because DMD).

Versions: Blake2dUseSIMD or Blake2dUseIntrinsics (user will have to manually assign version)

Currently, because of the (rather silly) use of an enum for a structure template parameter, I cannot make inner_t types available outside the scope for compile-time keyed input.

The new idea would be:

• struct BLAKE2b(uint digestSize = 512, ulong[8] key = null) defining inner parameters
• struct BLAKE2s(uint digestSize = 256, uint[8] key = null) defining inner parameters
• template BLAKE2Impl(T, ...) called from either (and possible p variants)

I think you get the idea. I'll do this on my free time.

The Digest API does not support keyed algorithms. Thankfully, WrapperDigest (OOP API) is a class template and I hope to inherit it to add a key function already found in the structure template (Template API).

Key can still be given to template structure anyway when initiating the class template.

This adds the key function to the Digest OOP API.

Concept

class WrapperDigestKeyed(T) if (isDigest!T) : WrapperDigest!T
{
    void key(ubyte[] input)
    {
        _digest.key(input);
    }
}