final touches

changelog.md

@@ -101,3 +101,6 @@ hard drive. This means that some major API changes took place:
 * You can also just _try_ to receive items, without the need to `.await` anything. For
 each fo the receiving methods `recv`, `recv_batch` and `recv_until` you now have the
 try versions: `try_recv`, `try_recv_batch`, `try_recv_until`.
+* Solved a bug regarding the rollback of batch transactions when crossing over a segment.
+Older versions will do a complete mess out of this. The side effect: `commit` now returns
+a `Result`, which has to be treated.

src/queue/receiver.rs

@@ -42,12 +42,19 @@ pub(crate) async fn acquire_recv_lock<P: AsRef<Path>>(base: P) -> io::Result<Fil
 /// The receiver part of the queue. This part is asynchronous and therefore
 /// needs an executor that will the poll the futures to completion.
 pub struct Receiver {
+    /// The path to the folder holding the queue.
+    base: PathBuf,
+    /// The acquired receiver lock file for this queue.
     _file_guard: FileGuard,
+    /// The current segment being tailed.
     tail_follower: TailFollower,
+    /// The last header read from the queue.
     maybe_header: Option<[u8; 4]>,
+    /// The current queue state.
     state: QueueState,
+    /// The queue state as it was in the begining of the current transaction.
     initial_state: QueueState,
-    base: PathBuf,
+    /// The queue state saver/loader.
     persistence: QueueStatePersistence,
     /// Use this queue to buffer elements and provide "atomicity in an
     /// asynchronous context".
@@ -501,6 +508,7 @@ impl Receiver {
         predicate(None).await;
 
         // Poor man's do-while (aka. until)
+        // Strategy: fill `read_and_unused` to the brim and then drain at the end.
         loop {
             // Need to fetch from disk?
             if n_read == self.read_and_unused.len() {
@@ -518,6 +526,7 @@ impl Receiver {
 
         // And now, drain!
         let data = self.drain(n_read);
+
         Ok(RecvGuard {
             receiver: self,
             item: Some(data),