1 files changed, 22 insertions, 0 deletions
diff --git a/src/document/changes.rs b/src/document/changes.rs
index 92b7744..faba895 100644
--- a/src/document/changes.rs
+++ b/src/document/changes.rs
@@ -27,6 +27,28 @@ pub(crate) fn commit_times(doc: &Document, since: &[ChangeHash]) -> Vec<i64> {
         .collect()
 }
 
+/// Who wrote the changes after `since`: the authors their writers set (a node's ID,
+/// `replica::authored`), each once; and whether any change has none (a snapshot, or a
+/// change of a node that set none).
+pub(crate) fn authors_since(doc: &Document, since: &[ChangeHash]) -> (Vec<String>, bool) {
+    let mut authors: Vec<String> = Vec::new();
+    let mut unknown = false;
+    for change in doc.get_changes_meta(since) {
+        match change
+            .author
+            .as_ref()
+            .and_then(|author| std::str::from_utf8(author.as_bytes()).ok())
+        {
+            Some(author) if !authors.iter().any(|known| known == author) => {
+                authors.push(author.to_owned());
+            }
+            Some(_) => {}
+            None => unknown = true,
+        }
+    }
+    (authors, unknown)
+}
+
 /// The change `hash` as the document encodes it; None if `doc` doesn't have it.
 pub(crate) fn change_bytes(doc: &Document, hash: &ChangeHash) -> Option<Vec<u8>> {
     doc.get_change_by_hash(hash)