primitives: Refactor AbiEncodeWith::encode_to_slice (#2676)

Author: davidsemakula

CHANGELOG.md

@@ -17,12 +17,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Stabilize `is_contract` - [#2654](https://github.com/use-ink/ink/pull/2654)
 - Extract `sandbox` from `ink_e2e` into a new `ink_sandbox` crate - [#2659](https://github.com/use-ink/ink/pull/2659)
 - Synchronize with `polkadot-sdk/1b1cef306d9ceebf963fd15a04b5c79ee2618bce` ‒ [2675](https://github.com/use-ink/ink/pull/2675)
+- Refactor `AbiEncodeWith::encode_to_slice` - [#2676](https://github.com/use-ink/ink/pull/2676)
 
 ### Fixed
 - Fix decoding of `HostFn::minimum_balance` return value - [#2656](https://github.com/use-ink/ink/pull/2656)
 - Fix handling of `HostFn::code_hash` and `HostFn::weight_to_fee` - [#2672](https://github.com/use-ink/ink/pull/2672)
-
-### Fixed
 - `name` override fixes for message id computation and trait definitions - [#2649](https://github.com/use-ink/ink/pull/2649)
 
 ## Version 6.0.0-alpha.4

crates/primitives/src/abi.rs

@@ -69,6 +69,7 @@ pub trait AbiEncodeWith<Abi> {
 pub trait AbiDecodeWith<Abi>: Sized {
     /// The error type that can occur during decoding.
     type Error: core::fmt::Debug;
+
     /// Decodes the data from a buffer using the provided ABI.
     fn decode_with(buffer: &[u8]) -> Result<Self, Self::Error>;
 }
@@ -79,16 +80,9 @@ impl<T: scale::Encode> AbiEncodeWith<Ink> for T {
     }
 
     fn encode_to_slice(&self, buffer: &mut [u8]) -> usize {
-        let encoded = scale::Encode::encode(self);
-        let len = encoded.len();
-        debug_assert!(
-            len <= buffer.len(),
-            "encode scope buffer overflowed, encoded len is {} but buffer len is {}",
-            len,
-            buffer.len()
-        );
-        buffer[..len].copy_from_slice(&encoded);
-        len
+        let mut sized_output = SizedOutput::from(buffer);
+        scale::Encode::encode_to(self, &mut sized_output);
+        sized_output.len()
     }
 
     fn encode_to_vec(&self, buffer: &mut Vec<u8>) {
@@ -131,7 +125,7 @@ where
     }
 
     fn encode_to_vec(&self, buffer: &mut Vec<u8>) {
-        buffer.extend_from_slice(&T::encode(self));
+        buffer.extend(SolEncode::encode(self));
     }
 
     fn encode_topic<H>(&self, hasher: H) -> [u8; 32]
@@ -148,3 +142,37 @@ impl<T: SolDecode> AbiDecodeWith<Sol> for T {
         T::decode(buffer)
     }
 }
+
+/// A `scale::Output` implementing buffer that tracks the number of bytes written.
+struct SizedOutput<'a> {
+    buffer: &'a mut [u8],
+    offset: usize,
+}
+
+impl<'a> From<&'a mut [u8]> for SizedOutput<'a> {
+    fn from(buffer: &'a mut [u8]) -> Self {
+        Self { buffer, offset: 0 }
+    }
+}
+
+impl<'a> SizedOutput<'a> {
+    /// Returns the number of bytes written to the buffer.
+    pub fn len(&self) -> usize {
+        self.offset
+    }
+}
+
+impl scale::Output for SizedOutput<'_> {
+    fn write(&mut self, bytes: &[u8]) {
+        let start = self.offset;
+        let len = bytes.len();
+        debug_assert!(
+            len <= self.buffer.len(),
+            "output buffer overflowed, encoded len is {} but buffer len is {}",
+            len,
+            self.buffer.len()
+        );
+        self.buffer[start..start.checked_add(len).unwrap()].copy_from_slice(bytes);
+        self.offset = self.offset.checked_add(len).unwrap();
+    }
+}