Serde support

.travis.yml

@@ -3,12 +3,13 @@ sudo: false
 matrix:
     include:
         - rust: beta
+          env: FEATURES="serde_impl"
         - rust: nightly
-          env: FEATURES="--features nightly"
+          env: FEATURES="serde_impl nightly"
 script:
-    - cargo build $FEATURES
-    - cargo test $FEATURES
-    - cargo doc --no-deps $FEATURES
+    - cargo build --features "$FEATURES"
+    - cargo test --features "$FEATURES"
+    - cargo doc --no-deps --features "$FEATURES"
 after_success: |
     [ $TRAVIS_RUST_VERSION = nightly ] &&
     [ $TRAVIS_BRANCH = master ] &&

Cargo.toml

@@ -17,3 +17,8 @@ readme = "README.md"
 
 [features]
 nightly = []
+serde_impl = ["serde", "serde_json"]
+
+[dependencies]
+serde = { version = "^0.7", optional = true }
+serde_json = { version = "^0.7", optional = true }

src/lib.rs

@@ -31,6 +31,10 @@
 #![cfg_attr(feature = "nightly", feature(hashmap_public_hasher))]
 #![cfg_attr(all(feature = "nightly", test), feature(test))]
 
+// Optional Serde support
+#[cfg(feature = "serde_impl")]
+mod serde;
+
 use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::collections::hash_map::{self, HashMap};

src/serde.rs

@@ -0,0 +1,86 @@
+//! An optional implementation of serialization/deserialization. Reference
+//! implementations used:
+//!
+//! - [Serialize][1].
+//! - [Deserialize][2].
+//!
+//! [1]: https://github.com/serde-rs/serde/blob/97856462467db2e90cf368e407c7ebcc726a01a9/serde/src/ser/impls.rs#L601-L611
+//! [2]: https://github.com/serde-rs/serde/blob/97856462467db2e90cf368e407c7ebcc726a01a9/serde/src/de/impls.rs#L694-L746
+
+extern crate serde;
+
+use std::marker::PhantomData;
+use std::hash::{BuildHasher, Hash};
+
+use super::LinkedHashMap;
+
+use self::serde::{Serialize, Serializer, Deserialize, Deserializer};
+use self::serde::ser::impls::MapIteratorVisitor;
+use self::serde::de::{Visitor, MapVisitor, Error};
+
+impl<K, V, S> Serialize for LinkedHashMap<K, V, S>
+    where K: Serialize + Eq + Hash,
+          V: Serialize,
+          S: BuildHasher
+{
+    #[inline]
+    fn serialize<T>(&self, serializer: &mut T) -> Result<(), T::Error>
+        where T: Serializer,
+    {
+        serializer.serialize_map(MapIteratorVisitor::new(self.iter(), Some(self.len())))
+    }
+}
+
+/// `serde::de::Visitor` for a linked hash map.
+pub struct LinkedHashMapVisitor<K, V> {
+    marker: PhantomData<LinkedHashMap<K, V>>,
+}
+
+impl<K, V> LinkedHashMapVisitor<K, V> {
+    /// Creates a new visitor for a linked hash map.
+    pub fn new() -> Self {
+        LinkedHashMapVisitor {
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<K, V> Visitor for LinkedHashMapVisitor<K, V>
+    where K: Deserialize + Eq + Hash,
+          V: Deserialize,
+{
+    type Value = LinkedHashMap<K, V>;
+
+    #[inline]
+    fn visit_unit<E>(&mut self) -> Result<Self::Value, E>
+        where E: Error,
+    {
+        Ok(LinkedHashMap::new())
+    }
+
+    #[inline]
+    fn visit_map<Visitor>(&mut self, mut visitor: Visitor) -> Result<Self::Value, Visitor::Error>
+        where Visitor: MapVisitor,
+    {
+        let mut values = LinkedHashMap::with_capacity(visitor.size_hint().0);
+
+        while let Some((key, value)) = try!(visitor.visit()) {
+            values.insert(key, value);
+        }
+
+        try!(visitor.end());
+
+        Ok(values)
+    }
+}
+
+impl<K, V> Deserialize for LinkedHashMap<K, V>
+    where K: Deserialize + Eq + Hash,
+          V: Deserialize,
+{
+    fn deserialize<D>(deserializer: &mut D) -> Result<LinkedHashMap<K, V>, D::Error>
+        where D: Deserializer,
+    {
+        deserializer.deserialize_map(LinkedHashMapVisitor::new())
+    }
+}

tests/serde.rs

@@ -0,0 +1,44 @@
+#![cfg(feature = "serde_impl")]
+
+extern crate linked_hash_map;
+extern crate serde;
+extern crate serde_json;
+
+use linked_hash_map::LinkedHashMap;
+
+#[test]
+fn test_ser_empty() {
+    let map = LinkedHashMap::<String, u32>::new();
+    let j = serde_json::to_string(&map).unwrap();
+    let expected = "{}";
+    assert_eq!(j, expected);
+}
+
+#[test]
+fn test_ser() {
+    let mut map = LinkedHashMap::new();
+    map.insert("b", 20);
+    map.insert("a", 10);
+    map.insert("c", 30);
+
+    let j = serde_json::to_string(&map).unwrap();
+    let expected = r#"{"b":20,"a":10,"c":30}"#;
+    assert_eq!(j, expected);
+}
+
+#[test]
+fn test_de_empty() {
+    let j = "{}";
+    let map: LinkedHashMap<String, u32> = serde_json::from_str(j).unwrap();
+    assert_eq!(map.len(), 0);
+}
+
+#[test]
+fn test_de() {
+    let j = r#"{"b":20,"a":10,"c":30}"#;
+    let map: LinkedHashMap<String, u32> = serde_json::from_str(j).unwrap();
+    let items: Vec<_> = map.iter().map(|(k, v)| (k.clone(), *v)).collect();
+    assert_eq!(items, [("b".to_owned(), 20),
+                       ("a".to_owned(), 10),
+                       ("c".to_owned(), 30)]);
+}