signatures: with sync messages

Sync messages carry, for each actor's writes, the latest signature the
sender checked; the receiver checks it once it holds the change.

Auth plan M5.

1 files changed, 7 insertions, 21 deletions

diff --git a/src/document/file.rs b/src/document/file.rs
index 33f7934..2d588ee 100644
--- a/src/document/file.rs
+++ b/src/document/file.rs
@@ -6,8 +6,8 @@
 //! each a little-endian `u32` length and that many bytes, the first of them its kind
 //! (`Record`): first a full save of the document, then increments (the changes after
 //! the heads written before), and the signatures of its changes
-//! (`document::signatures`), those the file holds none of yet, each a change hash
-//! (32 bytes) and its signature (64). A record cut short by a crash is dropped when
+//! (`document::signatures`), those the file holds none of yet, as
+//! `signatures::pack` packs them. A record cut short by a crash is dropped when
 //! reading. A file of `continuum-document/1` has records of the document alone,
 //! without their kind: a full save, then increments.
 //!
@@ -46,9 +46,6 @@ enum Record {
     Signatures = 2,
 }
 
-/// A signature as a record holds it: the change's hash, then the signature.
-const SIGNATURE_BYTES: usize = 32 + 64;
-
 #[derive(Debug, Default, Serialize, Deserialize)]
 struct Header {
     /// Hex actor IDs.
@@ -146,16 +143,10 @@ fn parse(bytes: &[u8]) -> Result<(Loaded, usize)> {
             (Record::Increment, Some(doc)) => {
                 doc.load_incremental(record).context("an increment")?;
             }
-            (Record::Signatures, Some(_)) => {
-                if record.len() % SIGNATURE_BYTES != 0 {
-                    bail!("signatures of {} bytes", record.len());
-                }
-                for entry in record.chunks_exact(SIGNATURE_BYTES) {
-                    let (hash, signature) = entry.split_at(32);
-                    let hash = ChangeHash(hash.try_into().expect("32 bytes"));
-                    signatures.push((hash, signature.try_into().expect("64 bytes")));
-                }
-            }
+            (Record::Signatures, Some(_)) => signatures.extend(
+                super::signatures::unpack(record)
+                    .ok_or_else(|| anyhow!("signatures of {} bytes", record.len()))?,
+            ),
             (_, None) => bail!("a record before the full save"),
         }
         records = after;
@@ -184,12 +175,7 @@ fn signatures_record(signatures: &[(ChangeHash, [u8; 64])]) -> Vec<u8> {
     if signatures.is_empty() {
         return Vec::new();
     }
-    let mut bytes = Vec::with_capacity(signatures.len() * SIGNATURE_BYTES);
-    for (hash, signature) in signatures {
-        bytes.extend_from_slice(&hash.0);
-        bytes.extend_from_slice(signature);
-    }
-    record(Record::Signatures, &bytes)
+    record(Record::Signatures, &super::signatures::pack(signatures))
 }
 
 /// A whole file: header, one full save, and the signatures.