feat: add serde feature

Cargo.toml

@@ -38,6 +38,9 @@ std = []
 # "signature" crate.)
 traits-preview = ["digest"]
 
+# Adds serialization and deserialization abilities to `Hash`
+serde = ["dep:serde"]
+
 # ---------- Features below this line are undocumented and unstable. ----------
 # The following features are mainly intended for testing and benchmarking, and
 # they might change or disappear at any time without a major version bump.
@@ -91,6 +94,7 @@ rayon = { version = "1.2.1", optional = true }
 cfg-if = "1.0.0"
 digest = { version = "0.10.1", features = [ "mac" ], optional = true }
 zeroize_crate = { package = "zeroize", version = "1", default-features = false, features = ["zeroize_derive"], optional = true }
+serde = { version = "1.0.213", optional = true }
 
 [dev-dependencies]
 hex = "0.4.2"
@@ -99,6 +103,8 @@ rand = "0.8.0"
 rand_chacha = "0.3.0"
 reference_impl = { path = "./reference_impl" }
 hmac = "0.12.0"
+postcard = { version = "1.0.10", features = ["use-std"] }
+serde_json = "1.0.132"
 
 [build-dependencies]
 cc = "1.0.4"

src/lib.rs

@@ -73,6 +73,9 @@ extern crate zeroize_crate as zeroize; // Needed because `zeroize::Zeroize` assu
 #[cfg(test)]
 mod test;
 
+#[cfg(feature = "serde")]
+mod serde;
+
 // The guts module is for incremental use cases like the `bao` crate that need
 // to explicitly compute chunk and parent chaining values. It is semi-stable
 // and likely to keep working, but largely undocumented and not intended for

src/serde.rs

@@ -0,0 +1,58 @@
+use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
+
+use super::Hash;
+
+impl Serialize for Hash {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        if serializer.is_human_readable() {
+            serializer.serialize_str(self.to_string().as_str())
+        } else {
+            self.as_bytes().serialize(serializer)
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for Hash {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        if deserializer.is_human_readable() {
+            let s = String::deserialize(deserializer)?;
+            s.parse().map_err(de::Error::custom)
+        } else {
+            let data: [u8; 32] = Deserialize::deserialize(deserializer)?;
+            Ok(Hash::from(data))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::hash;
+
+    #[test]
+    fn test_hash_postcard() {
+        let hash = hash(b"hello");
+        let ser = postcard::to_stdvec(&hash).unwrap();
+        let de: Hash = postcard::from_bytes(&ser).unwrap();
+        assert_eq!(hash, de);
+
+        assert_eq!(ser.len(), 32);
+    }
+
+    #[test]
+    fn test_hash_json() {
+        let hash = hash(b"hello");
+        let ser = serde_json::to_string(&hash).unwrap();
+        let de: Hash = serde_json::from_str(&ser).unwrap();
+        assert_eq!(hash, de);
+        // 64 bytes of hex + 2 quotes
+        assert_eq!(ser.len(), 66);
+    }
+}