Added MutableBitmap::shrink_to_fit (#468)

src/bitmap/mutable.rs

@@ -208,6 +208,12 @@ impl MutableBitmap {
     pub fn set(&mut self, index: usize, value: bool) {
         set_bit(&mut self.buffer.as_mut_slice(), index, value)
     }
+
+    /// Shrinks the capacity of the [`MutableBitmap`] to fit its current length.
+    /// When the feature `cache_aligned`, the new capacity will be a multiple of 64 bytes.
+    pub fn shrink_to_fit(&mut self) {
+        self.buffer.shrink_to_fit();
+    }
 }
 
 impl MutableBitmap {

tests/it/bitmap/mutable.rs

@@ -329,3 +329,11 @@ fn extend_bitmap_other() {
         ])
     );
 }
+
+#[test]
+fn shrink_to_fit() {
+    let mut a = MutableBitmap::with_capacity(1025);
+    a.push(false);
+    a.shrink_to_fit();
+    assert!(a.capacity() < 1025);
+}