hint to using writers for serde serialization types, remove requirement of returning written bytes amount

Author: antonilol

heed-traits/src/lib.rs

@@ -47,8 +47,7 @@ pub trait BytesEncode<'a> {
     /// Encode the given item as bytes.
     fn bytes_encode(item: &'a Self::EItem) -> Result<Self::ReturnBytes, Self::Error>;
 
-    /// Encode the given item as bytes and write it into the writer. Returns the amount of bytes
-    /// that were written.
+    /// Encode the given item as bytes and write it into the writer.
     ///
     /// When implementing this, also take a look at [`zero_copy`][BytesEncode::zero_copy]'s
     /// documentation.
@@ -57,13 +56,12 @@ pub trait BytesEncode<'a> {
     fn bytes_encode_into_writer<W: io::Write>(
         item: &'a Self::EItem,
         writer: &mut W,
-    ) -> Result<usize, BoxedError> {
+    ) -> Result<(), BoxedError> {
         let bytes = Self::bytes_encode(item)?;
-        let bytes = bytes.as_ref();
 
-        writer.write_all(bytes)?;
+        writer.write_all(bytes.as_ref())?;
 
-        Ok(bytes.len())
+        Ok(())
     }
 }
 

heed-types/src/serde_bincode.rs

@@ -16,9 +16,21 @@ where
 
     type Error = bincode::Error;
 
+    fn zero_copy(_item: &Self::EItem) -> bool {
+        false
+    }
+
     fn bytes_encode(item: &Self::EItem) -> Result<Self::ReturnBytes, Self::Error> {
         bincode::serialize(item)
     }
+
+    fn bytes_encode_into_writer<W: std::io::Write>(
+        item: &'a Self::EItem,
+        writer: &mut W,
+    ) -> Result<(), BoxedError> {
+        bincode::serialize_into(writer, item)?;
+        Ok(())
+    }
 }
 
 impl<'a, T: 'a> BytesDecode<'a> for SerdeBincode<T>

heed-types/src/serde_json.rs

@@ -16,9 +16,21 @@ where
 
     type Error = serde_json::Error;
 
+    fn zero_copy(_item: &Self::EItem) -> bool {
+        false
+    }
+
     fn bytes_encode(item: &Self::EItem) -> Result<Self::ReturnBytes, Self::Error> {
         serde_json::to_vec(item)
     }
+
+    fn bytes_encode_into_writer<W: std::io::Write>(
+        item: &'a Self::EItem,
+        writer: &mut W,
+    ) -> Result<(), BoxedError> {
+        serde_json::to_writer(writer, item)?;
+        Ok(())
+    }
 }
 
 impl<'a, T: 'a> BytesDecode<'a> for SerdeJson<T>

heed-types/src/serde_rmp.rs

@@ -16,9 +16,21 @@ where
 
     type Error = rmp_serde::encode::Error;
 
+    fn zero_copy(_item: &Self::EItem) -> bool {
+        false
+    }
+
     fn bytes_encode(item: &Self::EItem) -> Result<Self::ReturnBytes, Self::Error> {
         rmp_serde::to_vec(item)
     }
+
+    fn bytes_encode_into_writer<W: std::io::Write>(
+        item: &'a Self::EItem,
+        writer: &mut W,
+    ) -> Result<(), BoxedError> {
+        rmp_serde::encode::write(writer, item)?;
+        Ok(())
+    }
 }
 
 impl<'a, T: 'a> BytesDecode<'a> for SerdeRmp<T>