Remove inherent method in favor of DST

ff/src/fields/field_hashers/expander/mod.rs

@@ -63,25 +63,6 @@ pub(super) struct ExpanderXof<H: ExtendableOutput + Clone + Default> {
     pub(super) k: usize,
 }
 
-impl<H: ExtendableOutput + Clone + Default> ExpanderXof<H> {
-    fn update_dst_prime(&self, h: &mut H) {
-        if self.dst.len() > MAX_DST_LENGTH {
-            let mut long = H::default();
-            long.update(&LONG_DST_PREFIX.clone());
-            long.update(&self.dst);
-
-            let mut new_dst = [0u8; MAX_DST_LENGTH];
-            let new_dst = &mut new_dst[0..((2 * self.k + 7) >> 3)];
-            long.finalize_xof_into(new_dst);
-            h.update(new_dst);
-            h.update(&[new_dst.len() as u8]);
-        } else {
-            h.update(&self.dst);
-            h.update(&[self.dst.len() as u8]);
-        }
-    }
-}
-
 impl<H: ExtendableOutput + Clone + Default> Expander for ExpanderXof<H> {
     fn expand(&self, msg: &[u8], n: usize) -> Vec<u8> {
         let mut xofer = self.xofer.clone();
@@ -92,7 +73,6 @@ impl<H: ExtendableOutput + Clone + Default> Expander for ExpanderXof<H> {
         xofer.update(&lib_str);
 
         DST::new_xof::<H>(self.dst.as_ref(), self.k).update(&mut xofer);
-        // self.update_dst_prime(&mut xofer);
         xofer.finalize_boxed(n).to_vec()
     }
 }