Add new ChannelId struct, unused

lightning/src/ln/channel.rs

@@ -602,6 +602,78 @@ impl_writeable_tlv_based!(PendingChannelMonitorUpdate, {
 	(0, update, required),
 });
 
+/// A unique 32-byte identifier for a channel.
+/// Depending on how the ID is generated, several varieties are distinguished (but all are stored as 32 bytes):
+/// - v1: generated based on funding tx outpoint (txid&index)
+/// - temporary: generated randomly
+/// (later planned v2: based on revocation point)
+/// The variety (context) is not stored, it is relevant only at creation.
+/// This is not exported to bindings users as we just use [u8; 32] directly
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct ChannelId {
+	// The 32-byte data of the ID
+	data: [u8; 32],
+}
+
+impl ChannelId {
+	/// Create v1 channel ID based on a funding TX ID and output index
+	pub fn v1_from_funding_txid(txid: &[u8; 32], output_index: u16) -> Self {
+		let mut res = [0; 32];
+		res[..].copy_from_slice(&txid[..]);
+		res[30] ^= ((output_index >> 8) & 0xff) as u8;
+		res[31] ^= ((output_index >> 0) & 0xff) as u8;
+		Self::from_bytes(res)
+	}
+
+	/// Create a temporary channel ID randomly, based on an entropy source.
+	pub fn temporary_from_entropy_source<ES: Deref>(entropy_source: &ES) -> Self
+	where ES::Target: EntropySource {
+		Self::from_bytes(entropy_source.get_secure_random_bytes())
+	}
+
+	/// Generic constructor; create a new channel ID from the provided data.
+	/// Use a more specific *from_* constructor when possible.
+	/// This constructor is useful for tests, and internally, e.g. when the channel ID is being deserialized.
+	pub fn from_bytes(data: [u8; 32]) -> Self {
+		Self{data}
+	}
+
+	/// Create a channel ID consisting of all-zeros data (placeholder).
+	pub fn new_zero() -> Self {
+		Self::from_bytes([0; 32])
+	}
+
+	/// Accessor for the channel ID data
+	pub fn bytes(&self) -> &[u8; 32] {
+		&self.data
+	}
+}
+
+impl Writeable for ChannelId {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.data.write(w)
+	}
+}
+
+impl Readable for ChannelId {
+	fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
+		let buf: [u8; 32] = Readable::read(r)?;
+		Ok(ChannelId::from_bytes(buf))
+	}
+}
+
+impl ToHex for ChannelId {
+	fn to_hex(&self) -> String {
+		self.data.to_hex()
+	}
+}
+
+impl fmt::Display for ChannelId {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		crate::util::logger::DebugBytes(&self.data).fmt(f)
+	}
+}
+
 /// Contains all state common to unfunded inbound/outbound channels.
 pub(super) struct UnfundedChannelContext {
 	/// A counter tracking how many ticks have elapsed since this unfunded channel was