Define TlvStream::skip_signatures

Provide a helper for skipping signature TLV records from a TLV stream.
This prevents needing to duplicate the check for signature TLV records
when writing a TLV stream without signatures in an upcoming commit.

diff --git a/lightning/src/offers/merkle.rs b/lightning/src/offers/merkle.rs
index 9031e0eb540f0c358a21f3480f503486ca21fba1..1a505aae8f018e07ee0230b7da01b1ef3939e4ab 100644 (file)
--- a/lightning/src/offers/merkle.rs
+++ b/lightning/src/offers/merkle.rs
@@ -75,22 +75,21 @@ fn message_digest(tag: &str, bytes: &[u8]) -> Message {
 /// Computes a merkle root hash for the given data, which must be a well-formed TLV stream
 /// containing at least one TLV record.
 fn root_hash(data: &[u8]) -> sha256::Hash {
-       let mut tlv_stream = TlvStream::new(&data[..]).peekable();
        let nonce_tag = tagged_hash_engine(sha256::Hash::from_engine({
+               let first_tlv_record = TlvStream::new(&data[..]).next().unwrap();
                let mut engine = sha256::Hash::engine();
                engine.input("LnNonce".as_bytes());
-               engine.input(tlv_stream.peek().unwrap().record_bytes);
+               engine.input(first_tlv_record.record_bytes);
                engine
        }));
        let leaf_tag = tagged_hash_engine(sha256::Hash::hash("LnLeaf".as_bytes()));
        let branch_tag = tagged_hash_engine(sha256::Hash::hash("LnBranch".as_bytes()));
 
        let mut leaves = Vec::new();
-       for record in tlv_stream {
-               if !SIGNATURE_TYPES.contains(&record.r#type) {
-                       leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
-                       leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
-               }
+       let tlv_stream = TlvStream::new(&data[..]);
+       for record in tlv_stream.skip_signatures() {
+               leaves.push(tagged_hash_from_engine(leaf_tag.clone(), &record.record_bytes));
+               leaves.push(tagged_hash_from_engine(nonce_tag.clone(), &record.type_bytes));
        }
 
        // Calculate the merkle root hash in place.
@@ -154,6 +153,10 @@ impl<'a> TlvStream<'a> {
                        data: io::Cursor::new(data),
                }
        }
+
+       fn skip_signatures(self) -> core::iter::Filter<TlvStream<'a>, fn(&TlvRecord) -> bool> {
+               self.filter(|record| !SIGNATURE_TYPES.contains(&record.r#type))
+       }
 }
 
 /// A slice into a [`TlvStream`] for a record.