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515 lines
13 KiB
Go
515 lines
13 KiB
Go
package swap
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import (
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"bytes"
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"crypto/sha256"
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"errors"
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"fmt"
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"github.com/btcsuite/btcd/chaincfg"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/btcsuite/btcutil"
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"github.com/lightningnetwork/lnd/input"
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"github.com/lightningnetwork/lnd/lntypes"
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)
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// HtlcOutputType defines the output type of the htlc that is published.
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type HtlcOutputType uint8
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const (
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// HtlcP2WSH is a pay-to-witness-script-hash output (segwit only)
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HtlcP2WSH HtlcOutputType = iota
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// HtlcNP2WSH is a nested pay-to-witness-script-hash output that can be
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// paid to be legacy wallets.
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HtlcNP2WSH
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)
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// ScriptVersion defines the HTLC script version.
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type ScriptVersion uint8
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const (
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// HtlcV1 refers to the original version of the HTLC script.
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HtlcV1 ScriptVersion = iota
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// HtlcV2 refers to the improved version of the HTLC script.
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HtlcV2
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)
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// htlcScript defines an interface for the different HTLC implementations.
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type HtlcScript interface {
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// genSuccessWitness returns the success script to spend this htlc with
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// the preimage.
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genSuccessWitness(receiverSig []byte, preimage lntypes.Preimage) wire.TxWitness
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// GenTimeoutWitness returns the timeout script to spend this htlc after
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// timeout.
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GenTimeoutWitness(senderSig []byte) wire.TxWitness
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// IsSuccessWitness checks whether the given stack is valid for
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// redeeming the htlc.
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IsSuccessWitness(witness wire.TxWitness) bool
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// Script returns the htlc script.
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Script() []byte
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// MaxSuccessWitnessSize returns the maximum witness size for the
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// success case witness.
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MaxSuccessWitnessSize() int
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// MaxTimeoutWitnessSize returns the maximum witness size for the
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// timeout case witness.
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MaxTimeoutWitnessSize() int
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// SuccessSequence returns the sequence to spend this htlc in the
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// success case.
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SuccessSequence() uint32
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}
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// Htlc contains relevant htlc information from the receiver perspective.
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type Htlc struct {
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HtlcScript
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Version ScriptVersion
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PkScript []byte
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Hash lntypes.Hash
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OutputType HtlcOutputType
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ChainParams *chaincfg.Params
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Address btcutil.Address
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SigScript []byte
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}
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var (
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quoteKey [33]byte
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quoteHash lntypes.Hash
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// QuoteHtlc is a template script just used for fee estimation. It uses
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// the maximum value for cltv expiry to get the maximum (worst case)
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// script size.
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QuoteHtlc, _ = NewHtlc(
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HtlcV2,
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^int32(0), quoteKey, quoteKey, quoteHash, HtlcP2WSH,
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&chaincfg.MainNetParams,
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)
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ErrInvalidScriptVersion = fmt.Errorf("invalid script version")
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)
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// String returns the string value of HtlcOutputType.
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func (h HtlcOutputType) String() string {
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switch h {
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case HtlcP2WSH:
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return "P2WSH"
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case HtlcNP2WSH:
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return "NP2WSH"
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default:
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return "unknown"
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}
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}
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// NewHtlc returns a new instance.
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func NewHtlc(version ScriptVersion, cltvExpiry int32,
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senderKey, receiverKey [33]byte,
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hash lntypes.Hash, outputType HtlcOutputType,
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chainParams *chaincfg.Params) (*Htlc, error) {
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var (
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err error
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htlc HtlcScript
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)
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switch version {
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case HtlcV1:
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htlc, err = newHTLCScriptV1(
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cltvExpiry, senderKey, receiverKey, hash,
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)
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case HtlcV2:
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htlc, err = newHTLCScriptV2(
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cltvExpiry, senderKey, receiverKey, hash,
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)
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default:
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return nil, ErrInvalidScriptVersion
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}
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if err != nil {
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return nil, err
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}
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p2wshPkScript, err := input.WitnessScriptHash(htlc.Script())
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if err != nil {
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return nil, err
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}
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var pkScript, sigScript []byte
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var address btcutil.Address
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switch outputType {
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case HtlcNP2WSH:
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// Generate p2sh script for p2wsh (nested).
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p2wshPkScriptHash := sha256.Sum256(p2wshPkScript)
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hash160 := input.Ripemd160H(p2wshPkScriptHash[:])
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builder := txscript.NewScriptBuilder()
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builder.AddOp(txscript.OP_HASH160)
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builder.AddData(hash160)
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builder.AddOp(txscript.OP_EQUAL)
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pkScript, err = builder.Script()
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if err != nil {
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return nil, err
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}
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// Generate a valid sigScript that will allow us to spend the
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// p2sh output. The sigScript will contain only a single push of
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// the p2wsh witness program corresponding to the matching
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// public key of this address.
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sigScript, err = txscript.NewScriptBuilder().
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AddData(p2wshPkScript).
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Script()
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if err != nil {
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return nil, err
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}
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address, err = btcutil.NewAddressScriptHash(
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p2wshPkScript, chainParams,
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)
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if err != nil {
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return nil, err
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}
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case HtlcP2WSH:
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pkScript = p2wshPkScript
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address, err = btcutil.NewAddressWitnessScriptHash(
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p2wshPkScript[2:],
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chainParams,
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)
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if err != nil {
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return nil, err
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}
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default:
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return nil, errors.New("unknown output type")
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}
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return &Htlc{
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HtlcScript: htlc,
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Hash: hash,
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Version: version,
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PkScript: pkScript,
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OutputType: outputType,
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ChainParams: chainParams,
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Address: address,
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SigScript: sigScript,
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}, nil
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}
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// GenSuccessWitness returns the success script to spend this htlc with
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// the preimage.
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func (h *Htlc) GenSuccessWitness(receiverSig []byte,
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preimage lntypes.Preimage) (wire.TxWitness, error) {
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if h.Hash != preimage.Hash() {
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return nil, errors.New("preimage doesn't match hash")
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}
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return h.genSuccessWitness(receiverSig, preimage), nil
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}
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// AddSuccessToEstimator adds a successful spend to a weight estimator.
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func (h *Htlc) AddSuccessToEstimator(estimator *input.TxWeightEstimator) {
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maxSuccessWitnessSize := h.MaxSuccessWitnessSize()
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switch h.OutputType {
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case HtlcP2WSH:
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estimator.AddWitnessInput(maxSuccessWitnessSize)
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case HtlcNP2WSH:
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estimator.AddNestedP2WSHInput(maxSuccessWitnessSize)
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}
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}
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// AddTimeoutToEstimator adds a timeout spend to a weight estimator.
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func (h *Htlc) AddTimeoutToEstimator(estimator *input.TxWeightEstimator) {
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maxTimeoutWitnessSize := h.MaxTimeoutWitnessSize()
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switch h.OutputType {
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case HtlcP2WSH:
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estimator.AddWitnessInput(maxTimeoutWitnessSize)
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case HtlcNP2WSH:
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estimator.AddNestedP2WSHInput(maxTimeoutWitnessSize)
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}
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}
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// HtlcScriptV1 encapsulates the htlc v1 script.
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type HtlcScriptV1 struct {
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script []byte
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}
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// newHTLCScriptV1 constructs an HtlcScript with the HTLC V1 witness script.
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//
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// OP_SIZE 32 OP_EQUAL
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// OP_IF
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// OP_HASH160 <ripemd160(swapHash)> OP_EQUALVERIFY
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// <receiverHtlcKey>
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// OP_ELSE
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// OP_DROP
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// <cltv timeout> OP_CHECKLOCKTIMEVERIFY OP_DROP
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// <senderHtlcKey>
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// OP_ENDIF
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// OP_CHECKSIG
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func newHTLCScriptV1(cltvExpiry int32, senderHtlcKey,
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receiverHtlcKey [33]byte, swapHash lntypes.Hash) (*HtlcScriptV1, error) {
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builder := txscript.NewScriptBuilder()
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builder.AddOp(txscript.OP_SIZE)
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builder.AddInt64(32)
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builder.AddOp(txscript.OP_EQUAL)
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builder.AddOp(txscript.OP_IF)
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builder.AddOp(txscript.OP_HASH160)
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builder.AddData(input.Ripemd160H(swapHash[:]))
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builder.AddOp(txscript.OP_EQUALVERIFY)
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builder.AddData(receiverHtlcKey[:])
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builder.AddOp(txscript.OP_ELSE)
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builder.AddOp(txscript.OP_DROP)
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builder.AddInt64(int64(cltvExpiry))
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builder.AddOp(txscript.OP_CHECKLOCKTIMEVERIFY)
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builder.AddOp(txscript.OP_DROP)
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builder.AddData(senderHtlcKey[:])
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builder.AddOp(txscript.OP_ENDIF)
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builder.AddOp(txscript.OP_CHECKSIG)
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script, err := builder.Script()
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if err != nil {
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return nil, err
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}
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return &HtlcScriptV1{
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script: script,
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}, nil
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}
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// genSuccessWitness returns the success script to spend this htlc with
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// the preimage.
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func (h *HtlcScriptV1) genSuccessWitness(receiverSig []byte,
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preimage lntypes.Preimage) wire.TxWitness {
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witnessStack := make(wire.TxWitness, 3)
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witnessStack[0] = append(receiverSig, byte(txscript.SigHashAll))
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witnessStack[1] = preimage[:]
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witnessStack[2] = h.script
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return witnessStack
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}
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// GenTimeoutWitness returns the timeout script to spend this htlc after
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// timeout.
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func (h *HtlcScriptV1) GenTimeoutWitness(senderSig []byte) wire.TxWitness {
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witnessStack := make(wire.TxWitness, 3)
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witnessStack[0] = append(senderSig, byte(txscript.SigHashAll))
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witnessStack[1] = []byte{0}
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witnessStack[2] = h.script
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return witnessStack
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}
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// IsSuccessWitness checks whether the given stack is valid for redeeming the
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// htlc.
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func (h *HtlcScriptV1) IsSuccessWitness(witness wire.TxWitness) bool {
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if len(witness) != 3 {
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return false
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}
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isTimeoutTx := bytes.Equal([]byte{0}, witness[1])
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return !isTimeoutTx
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}
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// Script returns the htlc script.
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func (h *HtlcScriptV1) Script() []byte {
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return h.script
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}
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// MaxSuccessWitnessSize returns the maximum success witness size.
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func (h *HtlcScriptV1) MaxSuccessWitnessSize() int {
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// Calculate maximum success witness size
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//
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// - number_of_witness_elements: 1 byte
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// - receiver_sig_length: 1 byte
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// - receiver_sig: 73 bytes
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// - preimage_length: 1 byte
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// - preimage: 32 bytes
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// - witness_script_length: 1 byte
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// - witness_script: len(script) bytes
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return 1 + 1 + 73 + 1 + 32 + 1 + len(h.script)
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}
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// MaxTimeoutWitnessSize return the maximum timeout witness size.
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func (h *HtlcScriptV1) MaxTimeoutWitnessSize() int {
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// Calculate maximum timeout witness size
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//
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// - number_of_witness_elements: 1 byte
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// - sender_sig_length: 1 byte
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// - sender_sig: 73 bytes
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// - zero_length: 1 byte
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// - zero: 1 byte
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// - witness_script_length: 1 byte
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// - witness_script: len(script) bytes
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return 1 + 1 + 73 + 1 + 1 + 1 + len(h.script)
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}
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// SuccessSequence returns the sequence to spend this htlc in the success case.
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func (h *HtlcScriptV1) SuccessSequence() uint32 {
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return 0
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}
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// HtlcScriptV2 encapsulates the htlc v2 script.
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type HtlcScriptV2 struct {
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script []byte
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senderKey [33]byte
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}
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// newHTLCScriptV2 construct an HtlcScipt with the HTLC V2 witness script.
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//
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// <receiverHtlcKey> OP_CHECKSIG OP_NOTIF
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// OP_DUP OP_HASH160 <HASH160(senderHtlcKey)> OP_EQUALVERIFY OP_CHECKSIGVERIFY
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// <cltv timeout> OP_CHECKLOCKTIMEVERIFY
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// OP_ELSE
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// OP_SIZE <20> OP_EQUALVERIFY OP_HASH160 <ripemd(swapHash)> OP_EQUALVERIFY 1
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// OP_CHECKSEQUENCEVERIFY
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// OP_ENDIF
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func newHTLCScriptV2(cltvExpiry int32, senderHtlcKey,
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receiverHtlcKey [33]byte, swapHash lntypes.Hash) (*HtlcScriptV2, error) {
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builder := txscript.NewScriptBuilder()
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builder.AddData(receiverHtlcKey[:])
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builder.AddOp(txscript.OP_CHECKSIG)
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builder.AddOp(txscript.OP_NOTIF)
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builder.AddOp(txscript.OP_DUP)
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builder.AddOp(txscript.OP_HASH160)
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senderHtlcKeyHash := sha256.Sum256(senderHtlcKey[:])
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builder.AddData(input.Ripemd160H(senderHtlcKeyHash[:]))
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builder.AddOp(txscript.OP_EQUALVERIFY)
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builder.AddOp(txscript.OP_CHECKSIGVERIFY)
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builder.AddInt64(int64(cltvExpiry))
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builder.AddOp(txscript.OP_CHECKLOCKTIMEVERIFY)
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builder.AddOp(txscript.OP_ELSE)
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builder.AddOp(txscript.OP_SIZE)
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builder.AddInt64(0x20)
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builder.AddOp(txscript.OP_EQUALVERIFY)
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builder.AddOp(txscript.OP_HASH160)
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builder.AddData(input.Ripemd160H(swapHash[:]))
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builder.AddOp(txscript.OP_EQUALVERIFY)
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builder.AddOp(txscript.OP_1)
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builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
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builder.AddOp(txscript.OP_ENDIF)
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script, err := builder.Script()
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if err != nil {
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return nil, err
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}
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return &HtlcScriptV2{
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script: script,
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senderKey: senderHtlcKey,
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}, nil
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}
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// genSuccessWitness returns the success script to spend this htlc with
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// the preimage.
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func (h *HtlcScriptV2) genSuccessWitness(receiverSig []byte,
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preimage lntypes.Preimage) wire.TxWitness {
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witnessStack := make(wire.TxWitness, 3)
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witnessStack[0] = preimage[:]
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witnessStack[1] = append(receiverSig, byte(txscript.SigHashAll))
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witnessStack[2] = h.script
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return witnessStack
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}
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// IsSuccessWitness checks whether the given stack is valid for redeeming the
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// htlc.
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func (h *HtlcScriptV2) IsSuccessWitness(witness wire.TxWitness) bool {
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isTimeoutTx := len(witness) == 4
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return !isTimeoutTx
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}
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// GenTimeoutWitness returns the timeout script to spend this htlc after
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// timeout.
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func (h *HtlcScriptV2) GenTimeoutWitness(senderSig []byte) wire.TxWitness {
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witnessStack := make(wire.TxWitness, 4)
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witnessStack[0] = append(senderSig, byte(txscript.SigHashAll))
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witnessStack[1] = h.senderKey[:]
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witnessStack[2] = []byte{}
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witnessStack[3] = h.script
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return witnessStack
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}
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// Script returns the htlc script.
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func (h *HtlcScriptV2) Script() []byte {
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return h.script
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}
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// MaxSuccessWitnessSize returns maximum success witness size.
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func (h *HtlcScriptV2) MaxSuccessWitnessSize() int {
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// Calculate maximum success witness size
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//
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// - number_of_witness_elements: 1 byte
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// - receiver_sig_length: 1 byte
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// - receiver_sig: 73 bytes
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// - preimage_length: 1 byte
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// - preimage: 32 bytes
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// - witness_script_length: 1 byte
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// - witness_script: len(script) bytes
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return 1 + 1 + 73 + 1 + 32 + 1 + len(h.script)
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}
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// MaxTimeoutWitnessSize returns maximum timeout witness size.
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func (h *HtlcScriptV2) MaxTimeoutWitnessSize() int {
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// Calculate maximum timeout witness size
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//
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// - number_of_witness_elements: 1 byte
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// - sender_sig_length: 1 byte
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// - sender_sig: 73 bytes
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// - sender_key_length: 1 byte
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// - sender_key: 33 bytes
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// - zero: 1 byte
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// - witness_script_length: 1 byte
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// - witness_script: len(script) bytes
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return 1 + 1 + 73 + 1 + 33 + 1 + 1 + len(h.script)
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}
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// SuccessSequence returns the sequence to spend this htlc in the success case.
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func (h *HtlcScriptV2) SuccessSequence() uint32 {
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return 1
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}
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