Change get_shuffling to borrow

src/state/state_transition.rs

@@ -12,14 +12,14 @@ fn get_shift_from_source(source: &[u8], offset: usize) -> u32 {
 // Given entropy in the form of `seed`, return a shuffled list of validators
 // of size `validator_count` or `sample`.
 pub fn get_shuffling(
-    seed: Sha256Digest,
+    seed: &Sha256Digest,
-    validator_count: u32,
+    validator_count: &u32,
-    sample: Option<u32>,
+    sample: &Option<u32>,
-    config: Config) 
+    config: &Config) 
     -> Vec<u32>
 {
     let max_validators = config.max_validators;
-    assert!(validator_count <= max_validators);
+    assert!(*validator_count <= max_validators);
     
     // TODO: figure out why the Python implementation uses
     // this `rand_max` var.
@@ -28,12 +28,12 @@ pub fn get_shuffling(
         Some(x) => x,
         None => validator_count
     };
-    let mut output: Vec<u32> = (0..validator_range).collect();
+    let mut output: Vec<u32> = (0..*validator_range).collect();
     let mut source = Blake2s::new();
     source.input(&seed);
     
     let mut v = 0;
-    while v < validator_range {
+    while v < *validator_range {
         let current_source = source.result();
         let mut source_offset = 0;
         while source_offset < 30 {
@@ -41,7 +41,7 @@ pub fn get_shuffling(
             let shuffled_position = (m % (validator_count - v)) + v;
             output.swap(v as usize, shuffled_position as usize);
             v += 1;
-            if v >= validator_count { break; }
+            if v >= *validator_count { break; }
             source_offset += 3;
         }
         // Re-hash the source
@@ -83,10 +83,10 @@ mod tests {
     #[test]
     fn test_shuffling() {
         let s = get_shuffling(
-            Sha256Digest::zero(),
+            &Sha256Digest::zero(),
-            10,
+            &10,
-            None,
+            &None,
-            Config::standard());
+            &Config::standard());
         assert_eq!(s,
                    vec!(0, 9, 7, 6, 4, 1, 8, 5, 2, 3),
                    "10 validator shuffle was not as expected");