Merge pull request #819 from TheBlueMatt/2021-03-810-rebased

[rust-lightning] / lightning-block-sync / src / init.rs

diff --git a/lightning-block-sync/src/init.rs b/lightning-block-sync/src/init.rs
index da9895ae7213f0a529aa7d77f4d84f8ca8d077fd..59c057157ef14bd6332d0bad1c2207b2919e741c 100644 (file)
--- a/lightning-block-sync/src/init.rs
+++ b/lightning-block-sync/src/init.rs
@@ -7,6 +7,18 @@ use bitcoin::network::constants::Network;
 
 use lightning::chain;
 
+/// Returns a validated block header of the source's best chain tip.
+///
+/// Upon success, the returned header can be used to initialize [`SpvClient`]. Useful during a fresh
+/// start when there are no chain listeners to sync yet.
+pub async fn validate_best_block_header<B: BlockSource>(block_source: &mut B) ->
+BlockSourceResult<ValidatedBlockHeader> {
+       let (best_block_hash, best_block_height) = block_source.get_best_block().await?;
+       block_source
+               .get_header(&best_block_hash, best_block_height).await?
+               .validate(best_block_hash)
+}
+
 /// Performs a one-time sync of chain listeners using a single *trusted* block source, bringing each
 /// listener's view of the chain from its paired block hash to `block_source`'s best chain tip.
 ///
@@ -38,7 +50,6 @@ use lightning::chain;
 ///
 /// use lightning_block_sync::*;
 ///
-/// use std::cell::RefCell;
 /// use std::io::Cursor;
 ///
 /// async fn init_sync<
@@ -62,12 +73,12 @@ use lightning::chain;
 /// ) {
 ///    // Read a serialized channel monitor paired with the block hash when it was persisted.
 ///    let serialized_monitor = "...";
-///    let (monitor_block_hash, mut monitor) = <(BlockHash, ChannelMonitor<S>)>::read(
+///    let (monitor_block_hash_option, mut monitor) = <(Option<BlockHash>, ChannelMonitor<S>)>::read(
 ///            &mut Cursor::new(&serialized_monitor), keys_manager).unwrap();
 ///
 ///    // Read the channel manager paired with the block hash when it was persisted.
 ///    let serialized_manager = "...";
-///    let (manager_block_hash, mut manager) = {
+///    let (manager_block_hash_option, mut manager) = {
 ///            let read_args = ChannelManagerReadArgs::new(
 ///                    keys_manager,
 ///                    fee_estimator,
@@ -77,22 +88,25 @@ use lightning::chain;
 ///                    config,
 ///                    vec![&mut monitor],
 ///            );
-///            <(BlockHash, ChannelManager<S, &ChainMonitor<S, &C, &T, &F, &L, &P>, &T, &K, &F, &L>)>::read(
+///            <(Option<BlockHash>, ChannelManager<S, &ChainMonitor<S, &C, &T, &F, &L, &P>, &T, &K, &F, &L>)>::read(
 ///                    &mut Cursor::new(&serialized_manager), read_args).unwrap()
 ///    };
 ///
 ///    // Synchronize any channel monitors and the channel manager to be on the best block.
 ///    let mut cache = UnboundedCache::new();
-///    let mut monitor_listener = (RefCell::new(monitor), &*tx_broadcaster, &*fee_estimator, &*logger);
-///    let listeners = vec![
-///            (monitor_block_hash, &mut monitor_listener as &mut dyn chain::Listen),
-///            (manager_block_hash, &mut manager as &mut dyn chain::Listen),
-///    ];
+///    let mut monitor_listener = (monitor, &*tx_broadcaster, &*fee_estimator, &*logger);
+///    let mut listeners = vec![];
+///    if let Some(monitor_block_hash) = monitor_block_hash_option {
+///            listeners.push((monitor_block_hash, &mut monitor_listener as &mut dyn chain::Listen))
+///    }
+///    if let Some(manager_block_hash) = manager_block_hash_option {
+///            listeners.push((manager_block_hash, &mut manager as &mut dyn chain::Listen))
+///    }
 ///    let chain_tip = init::synchronize_listeners(
 ///            block_source, Network::Bitcoin, &mut cache, listeners).await.unwrap();
 ///
 ///    // Allow the chain monitor to watch any channels.
-///    let monitor = monitor_listener.0.into_inner();
+///    let monitor = monitor_listener.0;
 ///    chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor);
 ///
 ///    // Create an SPV client to notify the chain monitor and channel manager of block events.
@@ -111,10 +125,7 @@ pub async fn synchronize_listeners<B: BlockSource, C: Cache>(
        header_cache: &mut C,
        mut chain_listeners: Vec<(BlockHash, &mut dyn chain::Listen)>,
 ) -> BlockSourceResult<ValidatedBlockHeader> {
-       let (best_block_hash, best_block_height) = block_source.get_best_block().await?;
-       let best_header = block_source
-               .get_header(&best_block_hash, best_block_height).await?
-               .validate(best_block_hash)?;
+       let best_header = validate_best_block_header(block_source).await?;
 
        // Fetch the header for the block hash paired with each listener.
        let mut chain_listeners_with_old_headers = Vec::new();