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Clean up docs on public chan_utils methods to be more useful #940

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Jun 8, 2021
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Clean up docs on public chan_utils methods to be more useful #940

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19 changes: 15 additions & 4 deletions lightning/src/ln/chan_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -525,12 +525,18 @@ pub fn make_funding_redeemscript(broadcaster: &PublicKey, countersignatory: &Pub
}.push_opcode(opcodes::all::OP_PUSHNUM_2).push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script()
}

/// panics if htlc.transaction_output_index.is_none()!
pub fn build_htlc_transaction(prev_hash: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
/// Builds an unsigned HTLC-Success or HTLC-Timeout transaction from the given channel and HTLC
/// parameters. This is used by [`TrustedCommitmentTransaction::get_htlc_sigs`] to fetch the
/// transaction which needs signing, and can be used to construct an HTLC transaction which is
/// broadcastable given a counterparty HTLC signature.
///
/// Panics if htlc.transaction_output_index.is_none() (as such HTLCs do not appear in the
/// commitment transaction).
pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
let mut txins: Vec<TxIn> = Vec::new();
txins.push(TxIn {
previous_output: OutPoint {
txid: prev_hash.clone(),
txid: commitment_txid.clone(),
vout: htlc.transaction_output_index.expect("Can't build an HTLC transaction for a dust output"),
},
script_sig: Script::new(),
Expand Down Expand Up @@ -1177,7 +1183,12 @@ impl<'a> TrustedCommitmentTransaction<'a> {
}
}

/// Get the transaction number obscure factor
/// Commitment transaction numbers which appear in the transactions themselves are XOR'd with a
/// shared secret first. This prevents on-chain observers from discovering how many commitment
/// transactions occurred in a channel before it was closed.
///
/// This function gets the shared secret from relevant channel public keys and can be used to
/// "decrypt" the commitment transaction number given a commitment transaction on-chain.
pub fn get_commitment_transaction_number_obscure_factor(
broadcaster_payment_basepoint: &PublicKey,
countersignatory_payment_basepoint: &PublicKey,
Expand Down