1 files changed, 12 insertions, 13 deletions

diff --git a/src/document/changes.rs b/src/document/changes.rs
index 33029fc..92b7744 100644
--- a/src/document/changes.rs
+++ b/src/document/changes.rs
@@ -6,11 +6,10 @@ use std::collections::{HashMap, HashSet};
 
 use anyhow::{Context, Result, anyhow, bail};
 
-use super::{Change, ChangeHash, Document};
+use super::{Change, ChangeHash, Document, ReadDoc};
 
-/// Those of `heads` that `doc` doesn't have. (Looking a change up needs the document
-/// mutably.)
-pub(crate) fn missing(doc: &mut Document, heads: &[ChangeHash]) -> Vec<ChangeHash> {
+/// Those of `heads` that `doc` doesn't have.
+pub(crate) fn missing(doc: &impl ReadDoc, heads: &[ChangeHash]) -> Vec<ChangeHash> {
     heads
         .iter()
         .copied()
@@ -19,8 +18,8 @@ pub(crate) fn missing(doc: &mut Document, heads: &[ChangeHash]) -> Vec<ChangeHas
 }
 
 /// When the changes after `since` were committed, in Unix milliseconds by their
-/// writers' clocks (`Replica::commit`); changes without a time (snapshots) left out.
-pub(crate) fn commit_times(doc: &mut Document, since: &[ChangeHash]) -> Vec<i64> {
+/// writers' clocks (`Replica::transact`); changes without a time (snapshots) left out.
+pub(crate) fn commit_times(doc: &Document, since: &[ChangeHash]) -> Vec<i64> {
     doc.get_changes(since)
         .iter()
         .map(|change| change.timestamp())
@@ -29,7 +28,7 @@ pub(crate) fn commit_times(doc: &mut Document, since: &[ChangeHash]) -> Vec<i64>
 }
 
 /// The change `hash` as the document encodes it; None if `doc` doesn't have it.
-pub(crate) fn change_bytes(doc: &mut Document, hash: &ChangeHash) -> Option<Vec<u8>> {
+pub(crate) fn change_bytes(doc: &Document, hash: &ChangeHash) -> Option<Vec<u8>> {
     doc.get_change_by_hash(hash)
         .map(|change| change.raw_bytes().to_vec())
 }
@@ -49,7 +48,7 @@ pub(crate) fn change_from_bytes(bytes: Vec<u8>, hash: ChangeHash) -> Result<Chan
 /// (`load_delta` reads that). The same on every node holding `to`, whatever else it
 /// has. None if `doc` lacks part of `to`.
 pub(crate) fn delta_bytes(
-    doc: &mut Document,
+    doc: &Document,
     from: &[ChangeHash],
     to: &[ChangeHash],
 ) -> Option<Vec<u8>> {
@@ -147,8 +146,8 @@ mod tests {
             // Beyond `to`: must stay out of the delta.
             random_write(rng, &mut two);
 
-            let bytes = delta_bytes(&mut one, &from, &to).unwrap();
-            assert_eq!(delta_bytes(&mut two, &from, &to).unwrap(), bytes);
+            let bytes = delta_bytes(&one, &from, &to).unwrap();
+            assert_eq!(delta_bytes(&two, &from, &to).unwrap(), bytes);
 
             let mut behind = base.fork();
             load_delta(&mut behind, &bytes).unwrap();
@@ -160,7 +159,7 @@ mod tests {
     fn no_delta_without_its_heads() {
         let mut doc = Document::new();
         change(&mut doc, |doc| doc.put(ROOT, "k", 1_i64).unwrap());
-        assert!(delta_bytes(&mut doc, &[], &[ChangeHash([7; 32])]).is_none());
+        assert!(delta_bytes(&doc, &[], &[ChangeHash([7; 32])]).is_none());
     }
 
     /// A change loads from its bytes only as the change it was asked for.
@@ -169,9 +168,9 @@ mod tests {
         let mut doc = Document::new();
         change(&mut doc, |doc| doc.put(ROOT, "k", 1_i64).unwrap());
         let hash = doc.get_heads()[0];
-        let bytes = change_bytes(&mut doc, &hash).unwrap();
+        let bytes = change_bytes(&doc, &hash).unwrap();
         assert_eq!(change_from_bytes(bytes.clone(), hash).unwrap().hash(), hash);
         assert!(change_from_bytes(bytes, ChangeHash([7; 32])).is_err());
-        assert!(change_bytes(&mut doc, &ChangeHash([7; 32])).is_none());
+        assert!(change_bytes(&doc, &ChangeHash([7; 32])).is_none());
     }
 }