Take iterator in calculate_hash()

Avoids unnecessary allocations.

src/utils.rs

@@ -106,9 +106,18 @@ where
 }
 
 #[tracing::instrument(skip(keys))]
-pub(crate) fn calculate_hash(keys: &[&[u8]]) -> Vec<u8> {
-    // We only hash the pdu's event ids, not the whole pdu
-    let bytes = keys.join(&0xFF);
+pub(crate) fn calculate_hash<'a, I, T>(keys: I) -> Vec<u8>
+where
+    I: IntoIterator<Item = T>,
+    T: AsRef<[u8]>,
+{
+    let mut bytes = Vec::new();
+    for (i, key) in keys.into_iter().enumerate() {
+        if i != 0 {
+            bytes.push(0xFF);
+        }
+        bytes.extend_from_slice(key.as_ref());
+    }
     let hash = digest::digest(&digest::SHA256, &bytes);
     hash.as_ref().to_owned()
 }