lightning 0.0.121

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! ChannelId definition.

use crate::ln::msgs::DecodeError;
use crate::sign::EntropySource;
use crate::util::ser::{Readable, Writeable, Writer};

use crate::io;
use core::fmt;
use core::ops::Deref;

/// 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_ and _temporary_.
/// A _v1_ channel ID is generated based on funding tx outpoint (txid & index).
/// A _temporary_ ID is generated randomly.
/// (Later revocation-point-based _v2_ is a possibility.)
/// 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(pub [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(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(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.
	pub fn from_bytes(data: [u8; 32]) -> Self {
		Self(data)
	}

	/// Create a channel ID consisting of all-zeros data (e.g. when uninitialized or a placeholder).
	pub fn new_zero() -> Self {
		Self([0; 32])
	}

	/// Check whether ID is consisting of all zeros (uninitialized)
	pub fn is_zero(&self) -> bool {
		self.0[..] == [0; 32]
	}
}

impl Writeable for ChannelId {
	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
		self.0.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(buf))
	}
}

impl fmt::Display for ChannelId {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		crate::util::logger::DebugBytes(&self.0).fmt(f)
	}
}

#[cfg(test)]
mod tests {
	use hex::DisplayHex;

	use crate::ln::ChannelId;
	use crate::util::ser::{Readable, Writeable};
	use crate::util::test_utils;
	use crate::prelude::*;
	use crate::io;

	#[test]
	fn test_channel_id_v1_from_funding_txid() {
		let channel_id = ChannelId::v1_from_funding_txid(&[2; 32], 1);
		assert_eq!(channel_id.0.as_hex().to_string(), "0202020202020202020202020202020202020202020202020202020202020203");
	}

	#[test]
	fn test_channel_id_new_from_data() {
		let data: [u8; 32] = [2; 32];
		let channel_id = ChannelId::from_bytes(data.clone());
		assert_eq!(channel_id.0, data);
	}

	#[test]
	fn test_channel_id_equals() {
		let channel_id11 = ChannelId::v1_from_funding_txid(&[2; 32], 2);
		let channel_id12 = ChannelId::v1_from_funding_txid(&[2; 32], 2);
		let channel_id21 = ChannelId::v1_from_funding_txid(&[2; 32], 42);
		assert_eq!(channel_id11, channel_id12);
		assert_ne!(channel_id11, channel_id21);
	}

	#[test]
	fn test_channel_id_write_read() {
		let data: [u8; 32] = [2; 32];
		let channel_id = ChannelId::from_bytes(data.clone());

		let mut w = test_utils::TestVecWriter(Vec::new());
		channel_id.write(&mut w).unwrap();

		let channel_id_2 = ChannelId::read(&mut io::Cursor::new(&w.0)).unwrap();
		assert_eq!(channel_id_2, channel_id);
		assert_eq!(channel_id_2.0, data);
	}

	#[test]
	fn test_channel_id_display() {
		let channel_id = ChannelId::v1_from_funding_txid(&[2; 32], 1);
		assert_eq!(format!("{}", &channel_id), "0202020202020202020202020202020202020202020202020202020202020203");
	}
}