fix(encoding): set correct frame limit (#963)

* fix(encoding): set correct frame limit

* bugfix for `TranscriptRefs::len`

* use current frame limit as cushion room

crates/tlsn/src/commit/transcript.rs

@@ -28,6 +28,14 @@ impl TranscriptRefs {
         &self.recv
     }
 
+    /// Returns the transcript lengths.
+    pub(crate) fn len(&self) -> (usize, usize) {
+        let sent = self.sent.iter().map(|v| v.len()).sum();
+        let recv = self.recv.iter().map(|v| v.len()).sum();
+
+        (sent, recv)
+    }
+
     /// Returns VM references for the given direction and index, otherwise
     /// `None` if the index is out of bounds.
     pub(crate) fn get(&self, direction: Direction, idx: &Idx) -> Option<Vec<Vector<U8>>> {

crates/tlsn/src/encoding.rs

@@ -88,7 +88,12 @@ pub(crate) async fn transfer<'a>(
         .zip(recv_keys)
         .for_each(|(enc, key)| *enc ^= key);
 
+    // Set frame limit and add some extra bytes cushion room.
+    let (sent, recv) = refs.len();
+    let frame_limit = ENCODING_SIZE * (sent + recv) + ctx.io().limit();
+
     ctx.io_mut()
+        .with_limit(frame_limit)
         .send(Encodings {
             sent: sent_encoding,
             recv: recv_encoding,
@@ -114,7 +119,12 @@ pub(crate) async fn receive<'a>(
     f: impl Fn(Vector<U8>) -> &'a [Mac],
     idxs: impl IntoIterator<Item = &(Direction, Idx)>,
 ) -> Result<(EncodingCommitment, EncodingTree), EncodingError> {
-    let Encodings { mut sent, mut recv } = ctx.io_mut().expect_next().await?;
+    // Set frame limit and add some extra bytes cushion room.
+    let (sent, recv) = refs.len();
+    let frame_limit = ENCODING_SIZE * (sent + recv) + ctx.io().limit();
+
+    let Encodings { mut sent, mut recv } =
+        ctx.io_mut().with_limit(frame_limit).expect_next().await?;
 
     let sent_macs: Vec<u8> = refs
         .sent()