From 98391681ad283a631a9deafa6922eccc2cbf64f1 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Fri, 19 Nov 2021 11:06:02 +0000
Subject: [PATCH 1/2] Extract non-generic part of `push_topic`

---
 crates/env/src/engine/on_chain/impls.rs | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/crates/env/src/engine/on_chain/impls.rs b/crates/env/src/engine/on_chain/impls.rs
index 31a9cd5230..29c6a68e03 100644
--- a/crates/env/src/engine/on_chain/impls.rs
+++ b/crates/env/src/engine/on_chain/impls.rs
@@ -151,6 +151,21 @@ where
     {
         let mut split = self.scoped_buffer.split();
         let encoded = split.take_encoded(topic_value);
+        let result = Self::push_topic_encoded(encoded);
+        self.scoped_buffer.append_encoded(&result);
+    }
+
+    fn output(mut self) -> Self::Output {
+        let encoded_topics = self.scoped_buffer.take_appended();
+        (self.scoped_buffer, encoded_topics)
+    }
+}
+
+impl<'a, E> TopicsBuilder<'a, E>
+where
+    E: Environment,
+{
+    fn push_topic_encoded(encoded: &mut [u8]) -> <E as Environment>::Hash {
         let len_encoded = encoded.len();
         let mut result = <E as Environment>::Hash::clear();
         let len_result = result.as_ref().len();
@@ -162,12 +177,7 @@ where
             let copy_len = core::cmp::min(hash_output.len(), len_result);
             result.as_mut()[0..copy_len].copy_from_slice(&hash_output[0..copy_len]);
         }
-        self.scoped_buffer.append_encoded(&result);
-    }
-
-    fn output(mut self) -> Self::Output {
-        let encoded_topics = self.scoped_buffer.take_appended();
-        (self.scoped_buffer, encoded_topics)
+        result
     }
 }
 

From f73d8c8950e9308a1153f0a21655d073700153ee Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Fri, 19 Nov 2021 12:50:08 +0000
Subject: [PATCH 2/2] Move to inner fn

---
 crates/env/src/engine/on_chain/impls.rs | 37 +++++++++++--------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/crates/env/src/engine/on_chain/impls.rs b/crates/env/src/engine/on_chain/impls.rs
index 29c6a68e03..990cabceb6 100644
--- a/crates/env/src/engine/on_chain/impls.rs
+++ b/crates/env/src/engine/on_chain/impls.rs
@@ -149,9 +149,24 @@ where
     where
         T: scale::Encode,
     {
+        fn inner<E: Environment>(encoded: &mut [u8]) -> <E as Environment>::Hash {
+            let len_encoded = encoded.len();
+            let mut result = <E as Environment>::Hash::clear();
+            let len_result = result.as_ref().len();
+            if len_encoded <= len_result {
+                result.as_mut()[..len_encoded].copy_from_slice(encoded);
+            } else {
+                let mut hash_output = <Blake2x256 as HashOutput>::Type::default();
+                <Blake2x256 as CryptoHash>::hash(encoded, &mut hash_output);
+                let copy_len = core::cmp::min(hash_output.len(), len_result);
+                result.as_mut()[0..copy_len].copy_from_slice(&hash_output[0..copy_len]);
+            }
+            result
+        }
+
         let mut split = self.scoped_buffer.split();
         let encoded = split.take_encoded(topic_value);
-        let result = Self::push_topic_encoded(encoded);
+        let result = inner::<E>(encoded);
         self.scoped_buffer.append_encoded(&result);
     }
 
@@ -161,26 +176,6 @@ where
     }
 }
 
-impl<'a, E> TopicsBuilder<'a, E>
-where
-    E: Environment,
-{
-    fn push_topic_encoded(encoded: &mut [u8]) -> <E as Environment>::Hash {
-        let len_encoded = encoded.len();
-        let mut result = <E as Environment>::Hash::clear();
-        let len_result = result.as_ref().len();
-        if len_encoded <= len_result {
-            result.as_mut()[..len_encoded].copy_from_slice(encoded);
-        } else {
-            let mut hash_output = <Blake2x256 as HashOutput>::Type::default();
-            <Blake2x256 as CryptoHash>::hash(encoded, &mut hash_output);
-            let copy_len = core::cmp::min(hash_output.len(), len_result);
-            result.as_mut()[0..copy_len].copy_from_slice(&hash_output[0..copy_len]);
-        }
-        result
-    }
-}
-
 impl EnvInstance {
     /// Returns a new scoped buffer for the entire scope of the static 16 kB buffer.
     fn scoped_buffer(&mut self) -> ScopedBuffer {