From e688e7fa2210d93e4a9b689859671efdfb470c9b Mon Sep 17 00:00:00 2001
From: Ibraheem Ahmed <ibraheem@ibraheem.ca>
Date: Thu, 18 Jul 2024 20:24:31 -0400
Subject: [PATCH] add `serde` feature

---
 Cargo.toml         |   8 +++-
 src/lib.rs         |   3 ++
 src/serde_impls.rs | 117 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+), 1 deletion(-)
 create mode 100644 src/serde_impls.rs

diff --git a/Cargo.toml b/Cargo.toml
index 7b6f439..e35280d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,8 +11,9 @@ readme = "README.md"
 exclude = ["assets/*"]
 
 [dependencies]
-atomic-wait = "1.1.0"
 seize = "0.4.4"
+atomic-wait = "1.1.0"
+serde = { version = "1.0.204", optional = true }
 
 [dev-dependencies]
 rand = "0.8.5"
@@ -22,6 +23,11 @@ dashmap = "5.5.3"
 criterion = "0.5.1"
 tokio = { version = "1.38.0", features = ["fs", "rt"] }
 num_cpus = "1.16.0"
+serde_json = "1.0.120"
+
+[features]
+default = []
+serde = ["dep:serde"]
 
 [profile.test]
 inherits = "release"
diff --git a/src/lib.rs b/src/lib.rs
index 06b226e..ab65187 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -223,6 +223,9 @@ The `Guard` trait supports both local and owned guards. Note the `'guard` lifeti
 mod map;
 mod raw;
 
+#[cfg(feature = "serde")]
+mod serde_impls;
+
 pub use map::{
     Compute, HashMap, HashMapBuilder, HashMapRef, Iter, Keys, OccupiedError, Operation, ResizeMode,
     Values,
diff --git a/src/serde_impls.rs b/src/serde_impls.rs
new file mode 100644
index 0000000..b16d80a
--- /dev/null
+++ b/src/serde_impls.rs
@@ -0,0 +1,117 @@
+use serde::de::{MapAccess, Visitor};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+use std::fmt::{self, Formatter};
+use std::hash::{BuildHasher, Hash};
+use std::marker::PhantomData;
+
+use crate::{Guard, HashMap, HashMapRef};
+
+struct MapVisitor<K, V, S> {
+    _marker: PhantomData<HashMap<K, V, S>>,
+}
+
+impl<K, V, S, G> Serialize for HashMapRef<'_, K, V, S, G>
+where
+    K: Serialize + Hash + Eq,
+    V: Serialize,
+    G: Guard,
+    S: BuildHasher,
+{
+    fn serialize<Sr>(&self, serializer: Sr) -> Result<Sr::Ok, Sr::Error>
+    where
+        Sr: Serializer,
+    {
+        serializer.collect_map(self)
+    }
+}
+
+impl<K, V, S> Serialize for HashMap<K, V, S>
+where
+    K: Serialize + Hash + Eq,
+    V: Serialize,
+    S: BuildHasher,
+{
+    fn serialize<Sr>(&self, serializer: Sr) -> Result<Sr::Ok, Sr::Error>
+    where
+        Sr: Serializer,
+    {
+        self.pin().serialize(serializer)
+    }
+}
+
+impl<'de, K, V, S> Deserialize<'de> for HashMap<K, V, S>
+where
+    K: Deserialize<'de> + Hash + Eq,
+    V: Deserialize<'de>,
+    S: Default + BuildHasher,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_map(MapVisitor::new())
+    }
+}
+
+impl<K, V, S> MapVisitor<K, V, S> {
+    pub(crate) fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, K, V, S> Visitor<'de> for MapVisitor<K, V, S>
+where
+    K: Deserialize<'de> + Hash + Eq,
+    V: Deserialize<'de>,
+    S: Default + BuildHasher,
+{
+    type Value = HashMap<K, V, S>;
+
+    fn expecting(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(f, "a map")
+    }
+
+    fn visit_map<M>(self, mut access: M) -> Result<Self::Value, M::Error>
+    where
+        M: MapAccess<'de>,
+    {
+        let values = match access.size_hint() {
+            Some(size) => HashMap::with_capacity_and_hasher(size, S::default()),
+            None => HashMap::default(),
+        };
+
+        {
+            let values = values.pin();
+            while let Some((key, value)) = access.next_entry()? {
+                values.insert(key, value);
+            }
+        }
+
+        Ok(values)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::HashMap;
+
+    #[test]
+    fn test_map() {
+        let map: HashMap<u8, u8> = HashMap::new();
+        let guard = map.guard();
+
+        map.insert(0, 4, &guard);
+        map.insert(1, 3, &guard);
+        map.insert(2, 2, &guard);
+        map.insert(3, 1, &guard);
+        map.insert(4, 0, &guard);
+
+        let serialized = serde_json::to_string(&map).unwrap();
+        let deserialized = serde_json::from_str(&serialized).unwrap();
+
+        assert_eq!(map, deserialized);
+    }
+}