Don't consume readers with FixedLengthReader

We can't always assume that we're done reading after using a
FixedLengthReader. In some cases, we may need to read a set of
length-prefixed objects one at a time, and we'd like to do so without
incurring an additional allocation by reading a number of bytes first to
then deserialize them.

Author: wpaulino

lightning/src/crypto/streams.rs

@@ -151,7 +151,7 @@ mod tests {
 				let writeable_len = $obj.serialized_length() as u64 + 16;
 				let write_adapter = ChaChaPolyWriteAdapter::new(rho, &$obj);
 				let encrypted_writeable_bytes = write_adapter.encode();
-				let encrypted_writeable = &encrypted_writeable_bytes[..];
+				let encrypted_writeable = &mut &encrypted_writeable_bytes[..];
 
 				// Now deserialize the object back and make sure it matches the original.
 				let mut rd = FixedLengthReader::new(encrypted_writeable, writeable_len);

lightning/src/events/mod.rs

@@ -1294,7 +1294,7 @@ impl MaybeReadable for Event {
 			// Note that we do not write a length-prefixed TLV for FundingGenerationReady events.
 			0u8 => Ok(None),
 			1u8 => {
-				let f = || {
+				let mut f = || {
 					let mut payment_hash = PaymentHash([0; 32]);
 					let mut payment_preimage = None;
 					let mut payment_secret = None;
@@ -1342,7 +1342,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			2u8 => {
-				let f = || {
+				let mut f = || {
 					let mut payment_preimage = PaymentPreimage([0; 32]);
 					let mut payment_hash = None;
 					let mut payment_id = None;
@@ -1366,7 +1366,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			3u8 => {
-				let f = || {
+				let mut f = || {
 					#[cfg(test)]
 					let error_code = Readable::read(reader)?;
 					#[cfg(test)]
@@ -1409,7 +1409,7 @@ impl MaybeReadable for Event {
 			},
 			4u8 => Ok(None),
 			5u8 => {
-				let f = || {
+				let mut f = || {
 					let mut outputs = WithoutLength(Vec::new());
 					let mut channel_id: Option<ChannelId> = None;
 					read_tlv_fields!(reader, {
@@ -1445,7 +1445,7 @@ impl MaybeReadable for Event {
 				}))
 			},
 			7u8 => {
-				let f = || {
+				let mut f = || {
 					let mut prev_channel_id = None;
 					let mut next_channel_id = None;
 					let mut prev_user_channel_id = None;
@@ -1473,7 +1473,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			9u8 => {
-				let f = || {
+				let mut f = || {
 					let mut channel_id = ChannelId::new_zero();
 					let mut reason = UpgradableRequired(None);
 					let mut user_channel_id_low_opt: Option<u64> = None;
@@ -1503,7 +1503,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			11u8 => {
-				let f = || {
+				let mut f = || {
 					let mut channel_id = ChannelId::new_zero();
 					let mut transaction = Transaction{ version: 2, lock_time: LockTime::ZERO, input: Vec::new(), output: Vec::new() };
 					read_tlv_fields!(reader, {
@@ -1515,7 +1515,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			13u8 => {
-				let f = || {
+				let mut f = || {
 					_init_and_read_len_prefixed_tlv_fields!(reader, {
 						(0, payment_id, required),
 						(2, payment_hash, option),
@@ -1531,7 +1531,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			15u8 => {
-				let f = || {
+				let mut f = || {
 					let mut payment_hash = PaymentHash([0; 32]);
 					let mut payment_id = PaymentId([0; 32]);
 					let mut reason = None;
@@ -1553,7 +1553,7 @@ impl MaybeReadable for Event {
 				Ok(None)
 			},
 			19u8 => {
-				let f = || {
+				let mut f = || {
 					let mut payment_hash = PaymentHash([0; 32]);
 					let mut purpose = UpgradableRequired(None);
 					let mut amount_msat = 0;
@@ -1580,7 +1580,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			21u8 => {
-				let f = || {
+				let mut f = || {
 					_init_and_read_len_prefixed_tlv_fields!(reader, {
 						(0, payment_id, required),
 						(2, payment_hash, required),
@@ -1596,7 +1596,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			23u8 => {
-				let f = || {
+				let mut f = || {
 					_init_and_read_len_prefixed_tlv_fields!(reader, {
 						(0, payment_id, required),
 						(2, payment_hash, required),
@@ -1614,7 +1614,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			25u8 => {
-				let f = || {
+				let mut f = || {
 					let mut prev_channel_id = ChannelId::new_zero();
 					let mut failed_next_destination_opt = UpgradableRequired(None);
 					read_tlv_fields!(reader, {
@@ -1630,7 +1630,7 @@ impl MaybeReadable for Event {
 			},
 			27u8 => Ok(None),
 			29u8 => {
-				let f = || {
+				let mut f = || {
 					let mut channel_id = ChannelId::new_zero();
 					let mut user_channel_id: u128 = 0;
 					let mut counterparty_node_id = RequiredWrapper(None);
@@ -1652,7 +1652,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			31u8 => {
-				let f = || {
+				let mut f = || {
 					let mut channel_id = ChannelId::new_zero();
 					let mut user_channel_id: u128 = 0;
 					let mut former_temporary_channel_id = None;
@@ -1680,7 +1680,7 @@ impl MaybeReadable for Event {
 				f()
 			},
 			33u8 => {
-				let f = || {
+				let mut f = || {
 					_init_and_read_len_prefixed_tlv_fields!(reader, {
 						(0, payment_id, required),
 					});

lightning/src/util/ser.rs

@@ -108,14 +108,14 @@ impl Writer for LengthCalculatingWriter {
 /// forward to ensure we always consume exactly the fixed length specified.
 ///
 /// This is not exported to bindings users as manual TLV building is not currently supported in bindings
-pub struct FixedLengthReader<R: Read> {
-	read: R,
+pub struct FixedLengthReader<'a, R: Read> {
+	read: &'a mut R,
 	bytes_read: u64,
 	total_bytes: u64,
 }
-impl<R: Read> FixedLengthReader<R> {
+impl<'a, R: Read> FixedLengthReader<'a, R> {
 	/// Returns a new [`FixedLengthReader`].
-	pub fn new(read: R, total_bytes: u64) -> Self {
+	pub fn new(read: &'a mut R, total_bytes: u64) -> Self {
 		Self { read, bytes_read: 0, total_bytes }
 	}
 
@@ -136,7 +136,7 @@ impl<R: Read> FixedLengthReader<R> {
 		}
 	}
 }
-impl<R: Read> Read for FixedLengthReader<R> {
+impl<'a, R: Read> Read for FixedLengthReader<'a, R> {
 	#[inline]
 	fn read(&mut self, dest: &mut [u8]) -> Result<usize, io::Error> {
 		if self.total_bytes == self.bytes_read {
@@ -154,7 +154,7 @@ impl<R: Read> Read for FixedLengthReader<R> {
 	}
 }
 
-impl<R: Read> LengthRead for FixedLengthReader<R> {
+impl<'a, R: Read> LengthRead for FixedLengthReader<'a, R> {
 	#[inline]
 	fn total_bytes(&self) -> u64 {
 		self.total_bytes

lightning/src/util/ser_macros.rs

@@ -1033,7 +1033,7 @@ macro_rules! impl_writeable_tlv_based_enum {
 					$($variant_id => {
 						// Because read_tlv_fields creates a labeled loop, we cannot call it twice
 						// in the same function body. Instead, we define a closure and call it.
-						let f = || {
+						let mut f = || {
 							$crate::_init_and_read_len_prefixed_tlv_fields!(reader, {
 								$(($type, $field, $fieldty)),*
 							});
@@ -1087,7 +1087,7 @@ macro_rules! impl_writeable_tlv_based_enum_upgradable {
 					$($variant_id => {
 						// Because read_tlv_fields creates a labeled loop, we cannot call it twice
 						// in the same function body. Instead, we define a closure and call it.
-						let f = || {
+						let mut f = || {
 							$crate::_init_and_read_len_prefixed_tlv_fields!(reader, {
 								$(($type, $field, $fieldty)),*
 							});