From 0804a16e24d2c8e0ed5e466df195fc358bb91b48 Mon Sep 17 00:00:00 2001
From: Tiago Carvalho <sugoiuguu@tfwno.gf>
Date: Tue, 20 Feb 2024 11:33:19 +0000
Subject: [PATCH] Implement `borsh` serialization routines

---
 src/borsh.rs | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs   |  6 ++++
 2 files changed, 102 insertions(+)
 create mode 100644 src/borsh.rs

diff --git a/src/borsh.rs b/src/borsh.rs
new file mode 100644
index 00000000..9338f435
--- /dev/null
+++ b/src/borsh.rs
@@ -0,0 +1,96 @@
+#![cfg_attr(docsrs, doc(cfg(feature = "borsh")))]
+
+use alloc::vec::Vec;
+use core::hash::BuildHasher;
+use core::hash::Hash;
+use core::iter::ExactSizeIterator;
+use core::mem::size_of;
+
+use borsh::error::ERROR_ZST_FORBIDDEN;
+use borsh::io::{Error, ErrorKind, Read, Result, Write};
+use borsh::{BorshDeserialize, BorshSerialize};
+
+use crate::map::IndexMap;
+use crate::set::IndexSet;
+
+impl<K, V, H> BorshSerialize for IndexMap<K, V, H>
+where
+    K: BorshSerialize,
+    V: BorshSerialize,
+    H: BuildHasher,
+{
+    #[inline]
+    fn serialize<W: Write>(&self, writer: &mut W) -> Result<()> {
+        check_zst::<K>()?;
+
+        let iterator = self.iter();
+
+        u32::try_from(iterator.len())
+            .map_err(|_| ErrorKind::InvalidData)?
+            .serialize(writer)?;
+
+        for (key, value) in iterator {
+            key.serialize(writer)?;
+            value.serialize(writer)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl<K, V, H> BorshDeserialize for IndexMap<K, V, H>
+where
+    K: BorshDeserialize + Eq + Hash,
+    V: BorshDeserialize,
+    H: BuildHasher + Default,
+{
+    #[inline]
+    fn deserialize_reader<R: Read>(reader: &mut R) -> Result<Self> {
+        check_zst::<K>()?;
+        let vec = <Vec<(K, V)>>::deserialize_reader(reader)?;
+        Ok(vec.into_iter().collect::<IndexMap<K, V, H>>())
+    }
+}
+
+impl<T, H> BorshSerialize for IndexSet<T, H>
+where
+    T: BorshSerialize,
+    H: BuildHasher,
+{
+    #[inline]
+    fn serialize<W: Write>(&self, writer: &mut W) -> Result<()> {
+        check_zst::<T>()?;
+
+        let iterator = self.iter();
+
+        u32::try_from(iterator.len())
+            .map_err(|_| ErrorKind::InvalidData)?
+            .serialize(writer)?;
+
+        for item in iterator {
+            item.serialize(writer)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl<T, H> BorshDeserialize for IndexSet<T, H>
+where
+    T: BorshDeserialize + Eq + Hash,
+    H: BuildHasher + Default,
+{
+    #[inline]
+    fn deserialize_reader<R: Read>(reader: &mut R) -> Result<Self> {
+        check_zst::<T>()?;
+        let vec = <Vec<T>>::deserialize_reader(reader)?;
+        Ok(vec.into_iter().collect::<IndexSet<T, H>>())
+    }
+}
+
+fn check_zst<T>() -> Result<()> {
+    if size_of::<T>() == 0 {
+        return Err(Error::new(ErrorKind::InvalidData, ERROR_ZST_FORBIDDEN));
+    }
+    Ok(())
+}
diff --git a/src/lib.rs b/src/lib.rs
index b88c1bce..d6d3ede9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -35,6 +35,8 @@
 //!   to [`IndexMap`] and [`IndexSet`]. Alternative implementations for
 //!   (de)serializing [`IndexMap`] as an ordered sequence are available in the
 //!   [`map::serde_seq`] module.
+//! * `borsh`: Adds implementations for [`BorshSerialize`] and [`BorshDeserialize`]
+//!   to [`IndexMap`] and [`IndexSet`].
 //! * `arbitrary`: Adds implementations for the [`arbitrary::Arbitrary`] trait
 //!   to [`IndexMap`] and [`IndexSet`].
 //! * `quickcheck`: Adds implementations for the [`quickcheck::Arbitrary`] trait
@@ -46,6 +48,8 @@
 //! [`no_std`]: #no-standard-library-targets
 //! [`Serialize`]: `::serde::Serialize`
 //! [`Deserialize`]: `::serde::Deserialize`
+//! [`BorshSerialize`]: `::borsh::BorshSerialize`
+//! [`BorshDeserialize`]: `::borsh::BorshDeserialize`
 //! [`arbitrary::Arbitrary`]: `::arbitrary::Arbitrary`
 //! [`quickcheck::Arbitrary`]: `::quickcheck::Arbitrary`
 //!
@@ -110,6 +114,8 @@ use alloc::vec::{self, Vec};
 mod arbitrary;
 #[macro_use]
 mod macros;
+#[cfg(feature = "borsh")]
+mod borsh;
 mod mutable_keys;
 #[cfg(feature = "serde")]
 mod serde;