Add new _init_and_read_tlv_stream ser macro

Useful for when you want to use _init_and_read_len_prefixed_tlv_fields but there is no
length byte at the start of the TLV stream.

Author: valentinewallace

lightning/src/onion_message/packet.rs

@@ -274,19 +274,16 @@ pub(crate) enum ControlTlvs {
 }
 
 impl Readable for ControlTlvs {
-	fn read<R: Read>(mut r: &mut R) -> Result<Self, DecodeError> {
-		let mut _padding: Option<Padding> = None;
-		let mut _short_channel_id: Option<u64> = None;
-		let mut next_node_id: Option<PublicKey> = None;
-		let mut path_id: Option<[u8; 32]> = None;
-		let mut next_blinding_override: Option<PublicKey> = None;
-		decode_tlv_stream!(&mut r, {
+	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
+		_init_and_read_tlv_stream!(r, {
 			(1, _padding, option),
 			(2, _short_channel_id, option),
 			(4, next_node_id, option),
 			(6, path_id, option),
 			(8, next_blinding_override, option),
 		});
+		let _padding: Option<Padding> = _padding;
+		let _short_channel_id: Option<u64> = _short_channel_id;
 
 		let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 		let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();

lightning/src/util/ser_macros.rs

@@ -809,6 +809,23 @@ macro_rules! _init_and_read_len_prefixed_tlv_fields {
 	}
 }
 
+/// Equivalent to running [`_init_tlv_field_var`] then [`decode_tlv_stream`].
+///
+/// This is exported for use by other exported macros, do not use directly.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! _init_and_read_tlv_stream {
+	($reader: ident, {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}) => {
+		$(
+			$crate::_init_tlv_field_var!($field, $fieldty);
+		)*
+
+		$crate::decode_tlv_stream!($reader, {
+			$(($type, $field, $fieldty)),*
+		});
+	}
+}
+
 /// Implements [`Readable`]/[`Writeable`] for a struct storing it as a set of TLVs
 /// If `$fieldty` is `required`, then `$field` is a required field that is not an [`Option`] nor a [`Vec`].
 /// If `$fieldty` is `(default_value, $default)`, then `$field` will be set to `$default` if not present.