feat: add ReadOnlyView::par_iter() and ReadOnlyView::into_par_iter() (#223)

src/lib.rs

@@ -16,6 +16,7 @@ mod util;
 #[cfg(feature = "rayon")]
 pub mod rayon {
     pub mod map;
+    pub mod read_only;
     pub mod set;
 }
 

src/rayon/map.rs

@@ -80,7 +80,7 @@ where
 }
 
 pub struct OwningIter<K, V, S = RandomState> {
-    shards: Box<[RwLock<HashMap<K, V, S>>]>,
+    pub(super) shards: Box<[RwLock<HashMap<K, V, S>>]>,
 }
 
 impl<K, V, S> ParallelIterator for OwningIter<K, V, S>
@@ -125,7 +125,7 @@ where
 }
 
 pub struct Iter<'a, K, V, S = RandomState> {
-    shards: &'a [RwLock<HashMap<K, V, S>>],
+    pub(super) shards: &'a [RwLock<HashMap<K, V, S>>],
 }
 
 impl<'a, K, V, S> ParallelIterator for Iter<'a, K, V, S>

src/rayon/read_only.rs

@@ -0,0 +1,96 @@
+use crate::mapref::multiple::RefMulti;
+use crate::rayon::map::Iter;
+use crate::ReadOnlyView;
+use core::hash::{BuildHasher, Hash};
+use rayon::iter::IntoParallelIterator;
+
+impl<K, V, S> IntoParallelIterator for ReadOnlyView<K, V, S>
+where
+    K: Send + Eq + Hash,
+    V: Send,
+    S: Send + Clone + BuildHasher,
+{
+    type Iter = super::map::OwningIter<K, V, S>;
+    type Item = (K, V);
+
+    fn into_par_iter(self) -> Self::Iter {
+        super::map::OwningIter {
+            shards: self.map.shards,
+        }
+    }
+}
+
+// This impl also enables `IntoParallelRefIterator::par_iter`
+impl<'a, K, V, S> IntoParallelIterator for &'a ReadOnlyView<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Iter = Iter<'a, K, V, S>;
+    type Item = RefMulti<'a, K, V, S>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        Iter {
+            shards: &self.map.shards,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashMap;
+    use rayon::iter::{IntoParallelIterator, IntoParallelRefIterator, ParallelIterator};
+
+    fn construct_sample_map() -> DashMap<i32, String> {
+        let map = DashMap::new();
+
+        map.insert(1, "one".to_string());
+
+        map.insert(10, "ten".to_string());
+
+        map.insert(27, "twenty seven".to_string());
+
+        map.insert(45, "forty five".to_string());
+
+        map
+    }
+
+    #[test]
+    fn test_par_iter() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        view.par_iter().for_each(|entry| {
+            let key = *entry.key();
+
+            assert!(view.contains_key(&key));
+
+            let map_entry = map.get(&key).unwrap();
+
+            assert_eq!(view.get(&key).unwrap(), map_entry.value());
+
+            let key_value: (&i32, &String) = view.get_key_value(&key).unwrap();
+
+            assert_eq!(key_value.0, map_entry.key());
+
+            assert_eq!(key_value.1, map_entry.value());
+        });
+    }
+
+    #[test]
+    fn test_into_par_iter() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        view.into_par_iter().for_each(|(key, value)| {
+            let map_entry = map.get(&key).unwrap();
+
+            assert_eq!(&key, map_entry.key());
+
+            assert_eq!(&value, map_entry.value());
+        });
+    }
+}

src/read_only.rs

@@ -7,7 +7,7 @@ use std::collections::hash_map::RandomState;
 
 /// A read-only view into a `DashMap`. Allows to obtain raw references to the stored values.
 pub struct ReadOnlyView<K, V, S = RandomState> {
-    map: DashMap<K, V, S>,
+    pub(crate) map: DashMap<K, V, S>,
 }
 
 impl<K: Eq + Hash + Clone, V: Clone, S: Clone> Clone for ReadOnlyView<K, V, S> {