+#[cfg(anchors)]
+/// Locates the output with an anchor script paying to `funding_pubkey` within `commitment_tx`.
+pub(crate) fn get_anchor_output<'a>(commitment_tx: &'a Transaction, funding_pubkey: &PublicKey) -> Option<(u32, &'a TxOut)> {
+ let anchor_script = chan_utils::get_anchor_redeemscript(funding_pubkey).to_v0_p2wsh();
+ commitment_tx.output.iter().enumerate()
+ .find(|(_, txout)| txout.script_pubkey == anchor_script)
+ .map(|(idx, txout)| (idx as u32, txout))
+}
+
+/// Returns the witness required to satisfy and spend an anchor input.
+pub fn build_anchor_input_witness(funding_key: &PublicKey, funding_sig: &Signature) -> Witness {
+ let anchor_redeem_script = chan_utils::get_anchor_redeemscript(funding_key);
+ let mut funding_sig = funding_sig.serialize_der().to_vec();
+ funding_sig.push(EcdsaSighashType::All as u8);
+ Witness::from_vec(vec![funding_sig, anchor_redeem_script.to_bytes()])
+}
+