Deduplicate gallop

Author: lqd

src/treefrog.rs

@@ -89,8 +89,8 @@ impl<Key: Ord, Val: Ord> RelationLeaper<Key, Val> for Relation<(Key, Val)> {
 }
 
 mod extend_with {
-
-    use super::{Relation, Leaper, gallop, binary_search};
+    use join::gallop;
+    use super::{Relation, Leaper, binary_search};
 
     /// Wraps a Relation<Tuple> as a leaper.
     pub struct ExtendWith<'a, Key: Ord+'a, Val: Ord+'a, Tuple: Ord, Func: Fn(&Tuple)->Key> {
@@ -139,8 +139,8 @@ mod extend_with {
 }
 
 mod extend_anti {
-
-    use super::{Relation, Leaper, gallop, binary_search};
+    use join::gallop;
+    use super::{Relation, Leaper, binary_search};
 
     /// Wraps a Relation<Tuple> as a leaper.
     pub struct ExtendAnti<'a, Key: Ord+'a, Val: Ord+'a, Tuple: Ord, Func: Fn(&Tuple)->Key> {
@@ -283,26 +283,3 @@ fn binary_search<T>(slice: &[T], mut cmp: impl FnMut(&T)->bool) -> usize {
     }
     lo
 }
-
-fn gallop<T>(mut slice: &[T], mut cmp: impl FnMut(&T)->bool) -> &[T] {
-    // if empty slice, or already >= element, return
-    if slice.len() > 0 && cmp(&slice[0]) {
-        let mut step = 1;
-        while step < slice.len() && cmp(&slice[step]) {
-            slice = &slice[step..];
-            step = step << 1;
-        }
-
-        step = step >> 1;
-        while step > 0 {
-            if step < slice.len() && cmp(&slice[step]) {
-                slice = &slice[step..];
-            }
-            step = step >> 1;
-        }
-
-        slice = &slice[1..]; // advance one, as we always stayed < value
-    }
-
-    return slice;
-}