Compose appended request messages

internal/domain/message.go

@@ -59,20 +59,24 @@ func NormalizeCacheControl(control *CacheControl) (*CacheControl, error) {
 // CloneRenderedMessages returns a deep copy of rendered messages.
 func CloneRenderedMessages(messages []RenderedMessage) []RenderedMessage {
 	cloned := make([]RenderedMessage, len(messages))
-	for index, message := range messages {
-		cloned[index] = message
-		if message.CacheControl != nil {
-			cacheControl := *message.CacheControl
-			cloned[index].CacheControl = &cacheControl
-		}
-	}
+	copyRenderedMessages(cloned, messages)
 	return cloned
 }
 
 // ConcatRenderedMessages returns an independently owned concatenation of messages.
 func ConcatRenderedMessages(prefix, suffix []RenderedMessage) []RenderedMessage {
-	messages := make([]RenderedMessage, 0, len(prefix)+len(suffix))
-	messages = append(messages, CloneRenderedMessages(prefix)...)
-	messages = append(messages, CloneRenderedMessages(suffix)...)
+	messages := make([]RenderedMessage, len(prefix)+len(suffix))
+	copyRenderedMessages(messages, prefix)
+	copyRenderedMessages(messages[len(prefix):], suffix)
 	return messages
 }
+
+func copyRenderedMessages(destination, source []RenderedMessage) {
+	for index, message := range source {
+		destination[index] = message
+		if message.CacheControl != nil {
+			cacheControl := *message.CacheControl
+			destination[index].CacheControl = &cacheControl
+		}
+	}
+}