Macro blake2_impl 

macro_rules! blake2_impl {
    (
        $name:ident, $alg_name:expr, $word:ident, $vec:ident, $bytes:ident,
        $block_size:ident, $R1:expr, $R2:expr, $R3:expr, $R4:expr, $IV:expr,
        $vardoc:expr, $doc:expr,
    ) => { ... };
}