Implement ser/de for reference count types (#27)

* Implement ser/de for reference count types

* fmt

borsh/Cargo.toml

@@ -27,3 +27,4 @@ hashbrown = "0.9.1"
 [features]
 default = ["std"]
 std = []
+rc = []

borsh/src/de/mod.rs

@@ -14,6 +14,9 @@ use crate::maybestd::{
     vec::Vec,
 };
 
+#[cfg(feature = "rc")]
+use std::{rc::Rc, sync::Arc};
+
 mod hint;
 
 const ERROR_NOT_ALL_BYTES_READ: &str = "Not all bytes read";
@@ -556,3 +559,27 @@ impl_tuple!(T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16);
 impl_tuple!(T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17);
 impl_tuple!(T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18);
 impl_tuple!(T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18 T19);
+
+#[cfg(feature = "rc")]
+impl<T, U> BorshDeserialize for Rc<T>
+where
+    U: Into<Rc<T>> + Borrow<T>,
+    T: ToOwned<Owned = U> + ?Sized,
+    T::Owned: BorshDeserialize,
+{
+    fn deserialize(buf: &mut &[u8]) -> Result<Self> {
+        Ok(T::Owned::deserialize(buf)?.into())
+    }
+}
+
+#[cfg(feature = "rc")]
+impl<T, U> BorshDeserialize for Arc<T>
+where
+    U: Into<Arc<T>> + Borrow<T>,
+    T: ToOwned<Owned = U> + ?Sized,
+    T::Owned: BorshDeserialize,
+{
+    fn deserialize(buf: &mut &[u8]) -> Result<Self> {
+        Ok(T::Owned::deserialize(buf)?.into())
+    }
+}

borsh/src/ser/mod.rs

@@ -10,6 +10,9 @@ use crate::maybestd::{
     vec::Vec,
 };
 
+#[cfg(feature = "rc")]
+use std::{rc::Rc, sync::Arc};
+
 const DEFAULT_SERIALIZER_CAPACITY: usize = 1024;
 
 /// A data-structure that can be serialized into binary format by NBOR.
@@ -463,3 +466,17 @@ impl_tuple!(0 T0 1 T1 2 T2 3 T3 4 T4 5 T5 6 T6 7 T7 8 T8 9 T9 10 T10 11 T11 12 T
 impl_tuple!(0 T0 1 T1 2 T2 3 T3 4 T4 5 T5 6 T6 7 T7 8 T8 9 T9 10 T10 11 T11 12 T12 13 T13 14 T14 15 T15 16 T16 17 T17);
 impl_tuple!(0 T0 1 T1 2 T2 3 T3 4 T4 5 T5 6 T6 7 T7 8 T8 9 T9 10 T10 11 T11 12 T12 13 T13 14 T14 15 T15 16 T16 17 T17 18 T18);
 impl_tuple!(0 T0 1 T1 2 T2 3 T3 4 T4 5 T5 6 T6 7 T7 8 T8 9 T9 10 T10 11 T11 12 T12 13 T13 14 T14 15 T15 16 T16 17 T17 18 T18 19 T19);
+
+#[cfg(feature = "rc")]
+impl<T: BorshSerialize + ?Sized> BorshSerialize for Rc<T> {
+    fn serialize<W: Write>(&self, writer: &mut W) -> Result<()> {
+        (**self).serialize(writer)
+    }
+}
+
+#[cfg(feature = "rc")]
+impl<T: BorshSerialize + ?Sized> BorshSerialize for Arc<T> {
+    fn serialize<W: Write>(&self, writer: &mut W) -> Result<()> {
+        (**self).serialize(writer)
+    }
+}

borsh/tests/test_rc.rs

@@ -0,0 +1,20 @@
+#![cfg(feature = "rc")]
+
+use borsh::{BorshDeserialize, BorshSerialize};
+use std::{rc::Rc, sync::Arc};
+
+#[test]
+fn test_rc_roundtrip() {
+    let value = Rc::new(8u8);
+    let serialized = value.try_to_vec().unwrap();
+    let deserialized = Rc::<u8>::try_from_slice(&serialized).unwrap();
+    assert_eq!(value, deserialized);
+}
+
+#[test]
+fn test_arc_roundtrip() {
+    let value = Arc::new(8u8);
+    let serialized = value.try_to_vec().unwrap();
+    let deserialized = Arc::<u8>::try_from_slice(&serialized).unwrap();
+    assert_eq!(value, deserialized);
+}