optim: k-adicity utility

Author: shramee

ff/src/fields/utils.rs

@@ -1,31 +1,30 @@
 use num_bigint::BigUint;
+use num_traits::Zero;
 
 /// Calculates the k-adicity of n, i.e., the number of trailing 0s in a base-k
 /// representation.
 pub const fn k_adicity(k: u64, mut n: u64) -> u32 {
+    if n == 0 {
+        return 0;
+    }
     let mut r = 0;
-    while n > 1 {
-        if n % k == 0 {
-            r += 1;
-            n /= k;
-        } else {
-            return r;
-        }
+    while n % k == 0 {
+        r += 1;
+        n /= k;
     }
     r
 }
 
 /// Calculates the k-adicity of n, i.e., the number of trailing 0s in a base-k
 /// representation.
 pub fn k_adicity_big_int(k: BigUint, mut n: BigUint) -> u32 {
+    if n.is_zero() {
+        return 0;
+    }
     let mut r = 0;
-    while &n > &1_u8.into() {
-        if &n % &k == 0_u8.into() {
-            r += 1;
-            n /= &k;
-        } else {
-            return r;
-        }
+    while (&n % &k).is_zero() {
+        r += 1;
+        n /= &k;
     }
     r
 }