Move active_validators into own crate

beacon_chain/utils/active-validators/src/lib.rs

@@ -0,0 +1,26 @@
+extern crate types;
+
+use types::{
+    ValidatorRecord,
+    ValidatorStatus,
+};
+
+pub fn validator_is_active(v: &ValidatorRecord) -> bool {
+    v.status == ValidatorStatus::Active as u8
+}
+
+/// Returns the indicies of each active validator in a given vec of validators.
+pub fn active_validator_indices(validators: &[ValidatorRecord])
+    -> Vec<usize>
+{
+    validators.iter()
+        .enumerate()
+        .filter_map(|(i, validator)| {
+            if validator_is_active(&validator) {
+                Some(i)
+            } else {
+                None
+            }
+        })
+        .collect()
+}