Write Weight bytes directly to buffer

Author: cmichi

crates/env/src/engine/on_chain/pallet_revive.rs

@@ -272,8 +272,8 @@ fn solidity_encode_bytes(
 ///
 /// # Developer Note
 ///
-// The implementation does not use `.div_ceil()`, as that function is more complex
-// and would use up more stack space.
+/// The implementation does not use `.div_ceil()`, as that function is more complex
+/// and would use up more stack space.
 #[allow(clippy::manual_div_ceil)]
 #[inline(always)]
 const fn solidity_padded_len(len: usize) -> usize {
@@ -1382,11 +1382,12 @@ impl TypedEnvBackend for EnvInstance {
         // 96 because 64 for `Weight` and 32 for `bytes` offset
         let n = solidity_encode_bytes(enc_msg, 96, 0, &mut buffer[4..]);
 
-        let mut weight_bytes = [0u8; 64];
-        weight_bytes[24..32].copy_from_slice(&weight.ref_time().to_be_bytes());
-        weight_bytes[56..64].copy_from_slice(&weight.proof_size().to_be_bytes());
         // put the `Weight` after the `bytes` offset word
-        buffer[4 + 32..4 + 32 + 64].copy_from_slice(&weight_bytes[..]);
+        // 4 bytes for the selector + 32 bytes for the `bytes` offset word
+        buffer[4 + 32 + 24..4 + 32 + 32]
+            .copy_from_slice(&weight.ref_time().to_be_bytes()[..]);
+        buffer[4 + 32 + 32 + 24..4 + 32 + 32 + 32]
+            .copy_from_slice(&weight.proof_size().to_be_bytes()[..]);
 
         let _call_result = ext::call(
             CallFlags::empty(),