Add clone impl.

src/lib.rs

@@ -59,6 +59,21 @@ pub struct DashMap<K, V, S = FxBuildHasher> {
     hasher: S,
 }
 
+impl<K: Eq + Hash + Clone, V: Clone, S: Clone> Clone for DashMap<K, V, S> {
+    fn clone(&self) -> Self {
+        let mut inner_shards = Vec::new();
+        for shard in self.shards.iter() {
+            let shard = shard.read();
+            inner_shards.push(RwLock::new((*shard).clone()));
+        }
+        Self {
+            ncb: self.ncb,
+            shards: inner_shards.into_boxed_slice(),
+            hasher: self.hasher.clone(),
+        }
+    }
+}
+
 impl<K, V> Default for DashMap<K, V>
 where
     K: Eq + Hash,

src/util.rs

@@ -40,19 +40,28 @@ pub unsafe fn change_lifetime_mut<'a, 'b, T>(x: &'a mut T) -> &'b mut T {
 }
 
 /// A simple wrapper around `T`
-/// 
+///
 /// This is to prevent UB when using `HashMap::get_key_value`, because
 /// `HashMap` doesn't expose an api to get the key and value, where
 /// the value is a `&mut T`.
-/// 
+///
 /// See [#10](https://github.com/xacrimon/dashmap/issues/10) for details
-/// 
+///
 /// This type is meant to be an implementation detail, but must be exposed due to the `Dashmap::shards`
 #[repr(transparent)]
 pub struct SharedValue<T> {
     value: UnsafeCell<T>,
 }
 
+impl<T: Clone> Clone for SharedValue<T> {
+    fn clone(&self) -> Self {
+        let inner = self.get().clone();
+        Self {
+            value: UnsafeCell::new(inner),
+        }
+    }
+}
+
 unsafe impl<T: Send> Send for SharedValue<T> {}
 unsafe impl<T: Sync> Sync for SharedValue<T> {}