code: function blake2bFinal(ctx) {
      ctx.t += ctx.c; // mark last block offset
      while (ctx.c < 128) { // fill up with zeros
          ctx.b[ctx.c++] = 0;
      }
      blake2bCompress(ctx, true); // final block flag = 1
      // little endian convert and store
      var out = new Uint8Array(ctx.outlen);
      for (var i = 0; i < ctx.outlen; i++) {
          out[i] = ctx.h[i >> 2] >> (8 * (i & 3));
      }
      return out;
  }
docs: Completes a BLAKE2b streaming hash Returns a Uint8Array containing the message digest