Add shrink_to

Author: cuviper

RELEASES.md

@@ -15,7 +15,9 @@
     `MutableKeys::get_index_mut2` to access the former behavior.
 
   - `IterMut` and `ValuesMut` now implement `Debug`.
-    
+
+  - The new `IndexMap::shrink_to` and `IndexSet::shrink_to` methods shrink
+    the capacity with a lower bound.
 
 - 1.8.0
 

src/map.rs

@@ -332,7 +332,14 @@ where
     ///
     /// Computes in **O(n)** time.
     pub fn shrink_to_fit(&mut self) {
-        self.core.shrink_to_fit();
+        self.core.shrink_to(0);
+    }
+
+    /// Shrink the capacity of the map with a lower limit.
+    ///
+    /// Computes in **O(n)** time.
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.core.shrink_to(min_capacity);
     }
 
     fn hash<Q: ?Sized + Hash>(&self, key: &Q) -> HashValue {

src/map/core.rs

@@ -201,10 +201,10 @@ impl<K, V> IndexMapCore<K, V> {
         self.entries.reserve_exact(additional);
     }
 
-    /// Shrink the capacity of the map as much as possible.
-    pub(crate) fn shrink_to_fit(&mut self) {
-        self.indices.shrink_to(0, get_hash(&self.entries));
-        self.entries.shrink_to_fit();
+    /// Shrink the capacity of the map with a lower bound
+    pub(crate) fn shrink_to(&mut self, min_capacity: usize) {
+        self.indices.shrink_to(min_capacity, get_hash(&self.entries));
+        self.entries.shrink_to(min_capacity);
     }
 
     /// Remove the last key-value pair

src/set.rs

@@ -268,6 +268,13 @@ where
         self.map.shrink_to_fit();
     }
 
+    /// Shrink the capacity of the set with a lower limit.
+    ///
+    /// Computes in **O(n)** time.
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.map.shrink_to(min_capacity);
+    }
+
     /// Insert the value into the set.
     ///
     /// If an equivalent item already exists in the set, it returns