Implement serde for BoxedUint

Adapted from #587

Author: wawwior

Cargo.lock

@@ -38,6 +38,7 @@ num-modular = { version = "0.6", features = ["num-bigint", "num-integer", "num-t
 proptest = "1.5"
 rand_core = { version = "0.9", features = ["std", "os_rng"] }
 rand_chacha = "0.9"
+serde_json = { version = "1.0.140", features = ["alloc"] }
 
 
 [features]

Cargo.toml

@@ -5,6 +5,9 @@ use crate::{DecodeError, Limb, Word, uint::encoding};
 use alloc::{boxed::Box, string::String, vec::Vec};
 use subtle::{Choice, CtOption};
 
+#[cfg(feature = "serde")]
+mod serde;
+
 impl BoxedUint {
     /// Create a new [`BoxedUint`] from the provided big endian bytes.
     ///

src/uint/boxed/encoding.rs

@@ -0,0 +1,72 @@
+use serdect::serde::{Deserialize, Deserializer, Serialize, Serializer, de::Error};
+
+use crate::BoxedUint;
+
+impl<'de> Deserialize<'de> for BoxedUint {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let slice = serdect::slice::deserialize_hex_or_bin_vec(deserializer)?;
+        Self::from_le_slice(&slice, slice.len() as u32 * 8).map_err(Error::custom)
+    }
+}
+
+impl Serialize for BoxedUint {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serdect::slice::serialize_hex_lower_or_bin(&self.to_le_bytes(), serializer)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::BoxedUint;
+
+    #[test]
+    fn serde_roundabout() {
+        let n = BoxedUint::from(11223344u64);
+        let ser = serde_json::to_string(&n).unwrap();
+        let de: BoxedUint = serde_json::from_str(&ser).unwrap();
+        assert_eq!(n, de);
+    }
+
+    #[test]
+    #[cfg(target_pointer_width = "64")]
+    fn serde() {
+        let test: BoxedUint = BoxedUint::from_be_hex("7711223344556600", 64).unwrap();
+
+        let serialized = bincode::serialize(&test).unwrap();
+        let deserialized: BoxedUint = bincode::deserialize(&serialized).unwrap();
+
+        assert_eq!(test, deserialized);
+    }
+
+    #[test]
+    #[cfg(target_pointer_width = "64")]
+    fn serde_owned() {
+        let test: BoxedUint = BoxedUint::from_be_hex("7711223344556600", 64).unwrap();
+
+        let serialized = bincode::serialize(&test).unwrap();
+        let deserialized: BoxedUint = bincode::deserialize_from(serialized.as_slice()).unwrap();
+
+        assert_eq!(test, deserialized);
+    }
+
+    #[test]
+    #[cfg(target_pointer_width = "32")]
+    fn from_le_slice_eq_test() {
+        let bytes = hex!("7766554433221100");
+        let box_uint = BoxedUint::from_le_slice(&bytes, 64).unwrap();
+
+        let serialized = bincode::serialize(&box_uint).unwrap();
+        let deserialized: BoxedUint = bincode::deserialize_from(serialized.as_slice()).unwrap();
+
+        assert_eq!(
+            deserialized.as_limbs(),
+            &[Limb(0x44556677), Limb(0x00112233)]
+        );
+    }
+}