Merge pull request #3 from seekstar/with-capacity

with_capacity

src/lib.rs

@@ -64,6 +64,23 @@ impl<T> IndexList<T> {
     pub fn new() -> Self {
         Default::default()
     }
+    /// Creates an empty `IndexList` with at least the specified capacity.
+    ///
+    /// Example:
+    /// ```rust
+    /// use index_list::IndexList;
+    /// let list = IndexList::<u64>::with_capacity(233);
+    /// ```
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> Self {
+        IndexList {
+            elems: Vec::with_capacity(capacity),
+            nodes: Vec::with_capacity(capacity),
+            used: ListEnds::new(),
+            free: ListEnds::new(),
+            size: 0,
+        }
+    }
     /// Returns the current capacity of the list.
     ///
     /// This value is always greater than or equal to the length.

tests/test.rs

@@ -164,7 +164,7 @@ fn test_single_element() {
 fn insert_remove_variants() {
     let count = 256;
     let mut rng = rand::thread_rng();
-    let mut list = IndexList::<u64>::new();
+    let mut list = IndexList::<u64>::with_capacity(count);
     let mut numbers: HashSet<u64> = HashSet::with_capacity(count);
     let mut indexes: Vec<u32> = Vec::with_capacity(count);
     for _ in 0..8 {