Optimize check_spend_remote HTLC a tad by avoiding indirections

Instead of hopping a pointer, we're only ever going to return one
Transaction at max, so skip the Vec. Also avoid
re-pubkey-converting the revocation key.

diff --git a/src/ln/channelmonitor.rs b/src/ln/channelmonitor.rs
index 6de0a63609ac6a4c8333796ad6da639f0c0760fe..f037c673079b2b0071697c012bbbac3d4d4d850d 100644 (file)
--- a/src/ln/channelmonitor.rs
+++ b/src/ln/channelmonitor.rs
@@ -1210,35 +1210,32 @@ impl ChannelMonitor {
        }
 
        /// Attempst to claim a remote HTLC-Success/HTLC-Timeout s outputs using the revocation key
-       fn check_spend_remote_htlc(&self, tx: &Transaction, commitment_number: u64) -> Vec<Transaction> {
-               let mut txn_to_broadcast = Vec::new();
-
+       fn check_spend_remote_htlc(&self, tx: &Transaction, commitment_number: u64) -> Option<Transaction> {
                let htlc_txid = tx.txid(); //TODO: This is gonna be a performance bottleneck for watchtowers!
 
                macro_rules! ignore_error {
                        ( $thing : expr ) => {
                                match $thing {
                                        Ok(a) => a,
-                                       Err(_) => return txn_to_broadcast
+                                       Err(_) => return None
                                }
                        };
                }
 
                let secret = self.get_secret(commitment_number).unwrap();
                let per_commitment_key = ignore_error!(SecretKey::from_slice(&self.secp_ctx, &secret));
+               let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);
                let revocation_pubkey = match self.key_storage {
                        KeyStorage::PrivMode { ref revocation_base_key, .. } => {
-                               let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);
                                ignore_error!(chan_utils::derive_public_revocation_key(&self.secp_ctx, &per_commitment_point, &PublicKey::from_secret_key(&self.secp_ctx, &revocation_base_key)))
                        },
                        KeyStorage::SigsMode { ref revocation_base_key, .. } => {
-                               let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);
                                ignore_error!(chan_utils::derive_public_revocation_key(&self.secp_ctx, &per_commitment_point, &revocation_base_key))
                        },
                };
                let delayed_key = match self.their_delayed_payment_base_key {
-                       None => return txn_to_broadcast,
-                       Some(their_delayed_payment_base_key) => ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key), &their_delayed_payment_base_key)),
+                       None => return None,
+                       Some(their_delayed_payment_base_key) => ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &per_commitment_point, &their_delayed_payment_base_key)),
                };
                let redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.their_to_self_delay.unwrap(), &delayed_key);
                let revokeable_p2wsh = redeemscript.to_v0_p2wsh();
@@ -1290,9 +1287,8 @@ impl ChannelMonitor {
                        spend_tx.input[0].witness.push(vec!(1));
                        spend_tx.input[0].witness.push(redeemscript.into_bytes());
 
-                       txn_to_broadcast.push(spend_tx);
-               }
-               txn_to_broadcast
+                       Some(spend_tx)
+               } else { None }
        }
 
        fn broadcast_by_local_state(&self, local_tx: &LocalSignedTx) -> Vec<Transaction> {
@@ -1369,8 +1365,10 @@ impl ChannelMonitor {
                                        }
                                } else {
                                        let remote_commitment_txn_on_chain = self.remote_commitment_txn_on_chain.lock().unwrap();
-                                       for commitment_number in remote_commitment_txn_on_chain.get(&txin.previous_output.txid) {
-                                               txn =  self.check_spend_remote_htlc(tx, *commitment_number);
+                                       if let Some(commitment_number) = remote_commitment_txn_on_chain.get(&prevout.txid) {
+                                               if let Some(tx) = self.check_spend_remote_htlc(tx, *commitment_number) {
+                                                       txn.push(tx);
+                                               }
                                        }
                                }
                                for tx in txn.iter() {