Implement Readable/Writeable for Events

As noted in the docs, Events don't round-trip fully, but round-trip
in a way that is useful for ChannelManagers, specifically some events
don't make sense anymore after a restart.

Author: TheBlueMatt

lightning/src/chain/keysinterface.rs

@@ -88,6 +88,57 @@ pub enum SpendableOutputDescriptor {
 	}
 }
 
+impl Writeable for SpendableOutputDescriptor {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+		match self {
+			&SpendableOutputDescriptor::StaticOutput { ref outpoint, ref output } => {
+				0u8.write(writer)?;
+				outpoint.write(writer)?;
+				output.write(writer)?;
+			},
+			&SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref key, ref witness_script, ref to_self_delay, ref output } => {
+				1u8.write(writer)?;
+				outpoint.write(writer)?;
+				key.write(writer)?;
+				witness_script.write(writer)?;
+				to_self_delay.write(writer)?;
+				output.write(writer)?;
+			},
+			&SpendableOutputDescriptor::DynamicOutputP2WPKH { ref outpoint, ref key, ref output } => {
+				2u8.write(writer)?;
+				outpoint.write(writer)?;
+				key.write(writer)?;
+				output.write(writer)?;
+			},
+		}
+		Ok(())
+	}
+}
+
+impl<R: ::std::io::Read> Readable<R> for SpendableOutputDescriptor {
+	fn read(reader: &mut R) -> Result<Self, DecodeError> {
+		match Readable::read(reader)? {
+			0u8 => Ok(SpendableOutputDescriptor::StaticOutput {
+				outpoint: Readable::read(reader)?,
+				output: Readable::read(reader)?,
+			}),
+			1u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WSH {
+				outpoint: Readable::read(reader)?,
+				key: Readable::read(reader)?,
+				witness_script: Readable::read(reader)?,
+				to_self_delay: Readable::read(reader)?,
+				output: Readable::read(reader)?,
+			}),
+			2u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WPKH {
+				outpoint: Readable::read(reader)?,
+				key: Readable::read(reader)?,
+				output: Readable::read(reader)?,
+			}),
+			_ => Err(DecodeError::InvalidValue),
+		}
+	}
+}
+
 /// A trait to describe an object which can get user secrets and key material.
 pub trait KeysInterface: Send + Sync {
 	/// A type which implements ChannelKeys which will be returned by get_channel_keys.

lightning/src/util/events.rs

@@ -16,6 +16,7 @@ use ln::msgs;
 use ln::channelmanager::{PaymentPreimage, PaymentHash};
 use chain::transaction::OutPoint;
 use chain::keysinterface::SpendableOutputDescriptor;
+use util::ser::{Writeable, Writer, MaybeReadable, Readable};
 
 use bitcoin::blockdata::script::Script;
 
@@ -24,6 +25,10 @@ use secp256k1::key::PublicKey;
 use std::time::Duration;
 
 /// An Event which you should probably take some action in response to.
+///
+/// Note that while Writeable and Readable are implemented for Event, you probably shouldn't use
+/// them directly as they don't round-trip exactly (for example FundingGenerationReady is never
+/// written as it makes no sense to respond to it after reconnecting to peers).
 pub enum Event {
 	/// Used to indicate that the client should generate a funding transaction with the given
 	/// parameters and then call ChannelManager::funding_transaction_generated.
@@ -108,6 +113,91 @@ pub enum Event {
 	},
 }
 
+impl Writeable for Event {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+		match self {
+			&Event::FundingGenerationReady { .. } => {
+				0u8.write(writer)?;
+				// We never write out FundingGenerationReady events as, upon disconnection, peers
+				// drop any channels which have not yet exchanged funding_signed.
+			},
+			&Event::FundingBroadcastSafe { ref funding_txo, ref user_channel_id } => {
+				1u8.write(writer)?;
+				funding_txo.write(writer)?;
+				user_channel_id.write(writer)?;
+			},
+			&Event::PaymentReceived { ref payment_hash, ref amt } => {
+				2u8.write(writer)?;
+				payment_hash.write(writer)?;
+				amt.write(writer)?;
+			},
+			&Event::PaymentSent { ref payment_preimage } => {
+				3u8.write(writer)?;
+				payment_preimage.write(writer)?;
+			},
+			&Event::PaymentFailed { ref payment_hash, ref rejected_by_dest,
+				#[cfg(test)]
+				ref error_code,
+			} => {
+				4u8.write(writer)?;
+				payment_hash.write(writer)?;
+				rejected_by_dest.write(writer)?;
+				#[cfg(test)]
+				error_code.write(writer)?;
+			},
+			&Event::PendingHTLCsForwardable { time_forwardable: _ } => {
+				5u8.write(writer)?;
+				// We don't write the time_fordwardable out at all, as we presume when the user
+				// deserializes us at least that much time has elapsed.
+			},
+			&Event::SpendableOutputs { ref outputs } => {
+				6u8.write(writer)?;
+				(outputs.len() as u64).write(writer)?;
+				for output in outputs.iter() {
+					output.write(writer)?;
+				}
+			},
+		}
+		Ok(())
+	}
+}
+impl<R: ::std::io::Read> MaybeReadable<R> for Event {
+	fn read(reader: &mut R) -> Result<Option<Self>, msgs::DecodeError> {
+		match Readable::read(reader)? {
+			0u8 => Ok(None),
+			1u8 => Ok(Some(Event::FundingBroadcastSafe {
+					funding_txo: Readable::read(reader)?,
+					user_channel_id: Readable::read(reader)?,
+				})),
+			2u8 => Ok(Some(Event::PaymentReceived {
+					payment_hash: Readable::read(reader)?,
+					amt: Readable::read(reader)?,
+				})),
+			3u8 => Ok(Some(Event::PaymentSent {
+					payment_preimage: Readable::read(reader)?,
+				})),
+			4u8 => Ok(Some(Event::PaymentFailed {
+					payment_hash: Readable::read(reader)?,
+					rejected_by_dest: Readable::read(reader)?,
+					#[cfg(test)]
+					error_code: Readable::read(reader)?,
+				})),
+			5u8 => Ok(Some(Event::PendingHTLCsForwardable {
+					time_forwardable: Duration::from_secs(0)
+				})),
+			6u8 => {
+				let outputs_len: u64 = Readable::read(reader)?;
+				let mut outputs = Vec::new();
+				for _ in 0..outputs_len {
+					outputs.push(Readable::read(reader)?);
+				}
+				Ok(Some(Event::SpendableOutputs { outputs }))
+			},
+			_ => Err(msgs::DecodeError::InvalidValue)
+		}
+	}
+}
+
 /// An event generated by ChannelManager which indicates a message should be sent to a peer (or
 /// broadcast to most peers).
 /// These events are handled by PeerManager::process_events if you are using a PeerManager.

lightning/src/util/ser.rs

@@ -11,7 +11,7 @@ use std::cmp;
 use secp256k1::Signature;
 use secp256k1::key::{PublicKey, SecretKey};
 use bitcoin::blockdata::script::Script;
-use bitcoin::blockdata::transaction::{OutPoint, Transaction};
+use bitcoin::blockdata::transaction::{OutPoint, Transaction, TxOut};
 use bitcoin::consensus;
 use bitcoin::consensus::Encodable;
 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
@@ -191,6 +191,15 @@ pub trait ReadableArgs<R, P>
 	fn read(reader: &mut R, params: P) -> Result<Self, DecodeError>;
 }
 
+/// A trait that various rust-lightning types implement allowing them to (maybe) be read in from a Read
+pub trait MaybeReadable<R>
+	where Self: Sized,
+	      R: Read
+{
+	/// Reads a Self in from the given Read
+	fn read(reader: &mut R) -> Result<Option<Self>, DecodeError>;
+}
+
 pub(crate) struct U48(pub u64);
 impl Writeable for U48 {
 	#[inline]
@@ -627,26 +636,32 @@ impl<R: Read> Readable<R> for OutPoint {
 	}
 }
 
-impl Writeable for Transaction {
-	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
-		match self.consensus_encode(WriterWriteAdaptor(writer)) {
-			Ok(_) => Ok(()),
-			Err(consensus::encode::Error::Io(e)) => Err(e),
-			Err(_) => panic!("We shouldn't get a consensus::encode::Error unless our Write generated an std::io::Error"),
+macro_rules! impl_consensus_ser {
+	($bitcoin_type: ty) => {
+		impl Writeable for $bitcoin_type {
+			fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+				match self.consensus_encode(WriterWriteAdaptor(writer)) {
+					Ok(_) => Ok(()),
+					Err(consensus::encode::Error::Io(e)) => Err(e),
+					Err(_) => panic!("We shouldn't get a consensus::encode::Error unless our Write generated an std::io::Error"),
+				}
+			}
 		}
-	}
-}
 
-impl<R: Read> Readable<R> for Transaction {
-	fn read(r: &mut R) -> Result<Self, DecodeError> {
-		match consensus::encode::Decodable::consensus_decode(r) {
-			Ok(t) => Ok(t),
-			Err(consensus::encode::Error::Io(ref e)) if e.kind() == ::std::io::ErrorKind::UnexpectedEof => Err(DecodeError::ShortRead),
-			Err(consensus::encode::Error::Io(e)) => Err(DecodeError::Io(e)),
-			Err(_) => Err(DecodeError::InvalidValue),
+		impl<R: Read> Readable<R> for $bitcoin_type {
+			fn read(r: &mut R) -> Result<Self, DecodeError> {
+				match consensus::encode::Decodable::consensus_decode(r) {
+					Ok(t) => Ok(t),
+					Err(consensus::encode::Error::Io(ref e)) if e.kind() == ::std::io::ErrorKind::UnexpectedEof => Err(DecodeError::ShortRead),
+					Err(consensus::encode::Error::Io(e)) => Err(DecodeError::Io(e)),
+					Err(_) => Err(DecodeError::InvalidValue),
+				}
+			}
 		}
 	}
 }
+impl_consensus_ser!(Transaction);
+impl_consensus_ser!(TxOut);
 
 impl<R: Read, T: Readable<R>> Readable<R> for Mutex<T> {
 	fn read(r: &mut R) -> Result<Self, DecodeError> {