Macro impl_packed_field_pow_2 

macro_rules! impl_packed_field_pow_2 {
    (
        $type:ty
        $(, ($type_param:ty, $param_name:ty))?
        ; [ $( ($block_len:expr, $func:ident) ),* $(,)? ],
        $width:expr
    ) => { ... };
}

A macro to implement the PackedFieldPow2 trait for PackedFields. The macro assumes that the PackedFields have a to_vector and from_vector method, which convert between the PackedField and a packed vector.

Arguments:

• $type: The type of the PackedField.
• ($type_param, $param_name): Optional type parameter if one is needed and a name for it.
• ; [ ($block_len, $func), ... ]: A list of block lengths and their corresponding interleaving functions.
• $width: The width of the PackedField, corresponding to the largest possible block length.

For example, calling this macro with:

impl_packed_field_pow_2!(
   PackedMontyField31Neon, (FieldParameters, FP);
   [
       (1, interleave_u32),
       (2, interleave_u64),
  ],
   4
);

crates the code:

impl<FP: FieldParameters> PackedFieldPow2 for PackedMontyField31Neon<FP> {
    #[inline]
    fn interleave(&self, other: Self, block_len: usize) -> (Self, Self) {
        let (v0, v1) = (self.to_vector(), other.to_vector());
        let (res0, res1) = match block_len {
            1 => interleave_u32(v0, v1),
            2 => interleave_u64(v0, v1),
            4 => (v0, v1),
            _ => panic!("unsupported block_len"),
        };
        unsafe {
            // Safety: We haven't changed any values, just moved data around
            // so all entries still represent valid field elements.
            (Self::from_vector(res0), Self::from_vector(res1))
        }
    }
}