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size.go
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size.go
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package lnwallet
import (
"github.com/btcsuite/btcd/blockchain"
"github.com/btcsuite/btcd/wire"
)
const (
// CommitWeight is the weight of the base commitment transaction which
// includes: one p2wsh input, out p2wkh output, and one p2wsh output.
CommitWeight int64 = 724
// HtlcWeight is the weight of an HTLC output.
HtlcWeight int64 = 172
)
const (
// witnessScaleFactor determines the level of "discount" witness data
// receives compared to "base" data. A scale factor of 4, denotes that
// witness data is 1/4 as cheap as regular non-witness data. Value copied
// here for convenience.
witnessScaleFactor = blockchain.WitnessScaleFactor
// The weight(weight), which is different from the !size! (see BIP-141),
// is calculated as:
// Weight = 4 * BaseSize + WitnessSize (weight).
// BaseSize - size of the transaction without witness data (bytes).
// WitnessSize - witness size (bytes).
// Weight - the metric for determining the weight of the transaction.
// P2WPKHSize 22 bytes
// - OP_0: 1 byte
// - OP_DATA: 1 byte (PublicKeyHASH160 length)
// - PublicKeyHASH160: 20 bytes
P2WPKHSize = 1 + 1 + 20
// P2WSHSize 34 bytes
// - OP_0: 1 byte
// - OP_DATA: 1 byte (WitnessScriptSHA256 length)
// - WitnessScriptSHA256: 32 bytes
P2WSHSize = 1 + 1 + 32
// P2PKHOutputSize 34 bytes
// - value: 8 bytes
// - var_int: 1 byte (pkscript_length)
// - pkscript (p2pkh): 25 bytes
P2PKHOutputSize = 8 + 1 + 25
// P2WKHOutputSize 31 bytes
// - value: 8 bytes
// - var_int: 1 byte (pkscript_length)
// - pkscript (p2wpkh): 22 bytes
P2WKHOutputSize = 8 + 1 + P2WPKHSize
// P2WSHOutputSize 43 bytes
// - value: 8 bytes
// - var_int: 1 byte (pkscript_length)
// - pkscript (p2wsh): 34 bytes
P2WSHOutputSize = 8 + 1 + P2WSHSize
// P2SHOutputSize 32 bytes
// - value: 8 bytes
// - var_int: 1 byte (pkscript_length)
// - pkscript (p2sh): 23 bytes
P2SHOutputSize = 8 + 1 + 23
// P2PKHScriptSigSize 108 bytes
// - OP_DATA: 1 byte (signature length)
// - signature
// - OP_DATA: 1 byte (pubkey length)
// - pubkey
P2PKHScriptSigSize = 1 + 73 + 1 + 33
// P2WKHWitnessSize 109 bytes
// - number_of_witness_elements: 1 byte
// - signature_length: 1 byte
// - signature
// - pubkey_length: 1 byte
// - pubkey
P2WKHWitnessSize = 1 + 1 + 73 + 1 + 33
// MultiSigSize 71 bytes
// - OP_2: 1 byte
// - OP_DATA: 1 byte (pubKeyAlice length)
// - pubKeyAlice: 33 bytes
// - OP_DATA: 1 byte (pubKeyBob length)
// - pubKeyBob: 33 bytes
// - OP_2: 1 byte
// - OP_CHECKMULTISIG: 1 byte
MultiSigSize = 1 + 1 + 33 + 1 + 33 + 1 + 1
// WitnessSize 222 bytes
// - NumberOfWitnessElements: 1 byte
// - NilLength: 1 byte
// - sigAliceLength: 1 byte
// - sigAlice: 73 bytes
// - sigBobLength: 1 byte
// - sigBob: 73 bytes
// - WitnessScriptLength: 1 byte
// - WitnessScript (MultiSig)
WitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + MultiSigSize
// InputSize 41 bytes
// - PreviousOutPoint:
// - Hash: 32 bytes
// - Index: 4 bytes
// - OP_DATA: 1 byte (ScriptSigLength)
// - ScriptSig: 0 bytes
// - Witness <---- we use "Witness" instead of "ScriptSig" for
// transaction validation, but "Witness" is stored
// separately and weight for it size is smaller. So
// we separate the calculation of ordinary data
// from witness data.
// - Sequence: 4 bytes
InputSize = 32 + 4 + 1 + 4
// FundingInputSize represents the size of an input to a funding
// transaction, and is equivalent to the size of a standard segwit input
// as calculated above.
FundingInputSize = InputSize
// CommitmentDelayOutput 43 bytes
// - Value: 8 bytes
// - VarInt: 1 byte (PkScript length)
// - PkScript (P2WSH)
CommitmentDelayOutput = 8 + 1 + P2WSHSize
// CommitmentKeyHashOutput 31 bytes
// - Value: 8 bytes
// - VarInt: 1 byte (PkScript length)
// - PkScript (P2WPKH)
CommitmentKeyHashOutput = 8 + 1 + P2WPKHSize
// HTLCSize 43 bytes
// - Value: 8 bytes
// - VarInt: 1 byte (PkScript length)
// - PkScript (PW2SH)
HTLCSize = 8 + 1 + P2WSHSize
// WitnessHeaderSize 2 bytes
// - Flag: 1 byte
// - Marker: 1 byte
WitnessHeaderSize = 1 + 1
// BaseTxSize 8 bytes
// - Version: 4 bytes
// - LockTime: 4 bytes
BaseTxSize = 4 + 4
// BaseCommitmentTxSize 125 + 43 * num-htlc-outputs bytes
// - Version: 4 bytes
// - WitnessHeader <---- part of the witness data
// - CountTxIn: 1 byte
// - TxIn: 41 bytes
// FundingInput
// - CountTxOut: 1 byte
// - TxOut: 74 + 43 * num-htlc-outputs bytes
// OutputPayingToThem,
// OutputPayingToUs,
// ....HTLCOutputs...
// - LockTime: 4 bytes
BaseCommitmentTxSize = 4 + 1 + FundingInputSize + 1 +
CommitmentDelayOutput + CommitmentKeyHashOutput + 4
// BaseCommitmentTxWeight 500 weight
BaseCommitmentTxWeight = witnessScaleFactor * BaseCommitmentTxSize
// WitnessCommitmentTxWeight 224 weight
WitnessCommitmentTxWeight = WitnessHeaderSize + WitnessSize
// HTLCWeight 172 weight
HTLCWeight = witnessScaleFactor * HTLCSize
// HtlcTimeoutWeight is the weight of the HTLC timeout transaction
// which will transition an outgoing HTLC to the delay-and-claim state.
HtlcTimeoutWeight = 663
// HtlcSuccessWeight is the weight of the HTLC success transaction
// which will transition an incoming HTLC to the delay-and-claim state.
HtlcSuccessWeight = 703
// MaxHTLCNumber is the maximum number HTLCs which can be included in a
// commitment transaction. This limit was chosen such that, in the case
// of a contract breach, the punishment transaction is able to sweep
// all the HTLC's yet still remain below the widely used standard
// weight limits.
MaxHTLCNumber = 966
// ToLocalScriptSize 79 bytes
// - OP_IF: 1 byte
// - OP_DATA: 1 byte
// - revoke_key: 33 bytes
// - OP_ELSE: 1 byte
// - OP_DATA: 1 byte
// - csv_delay: 4 bytes
// - OP_CHECKSEQUENCEVERIFY: 1 byte
// - OP_DROP: 1 byte
// - OP_DATA: 1 byte
// - delay_key: 33 bytes
// - OP_ENDIF: 1 byte
// - OP_CHECKSIG: 1 byte
ToLocalScriptSize = 1 + 1 + 33 + 1 + 1 + 4 + 1 + 1 + 1 + 33 + 1 + 1
// ToLocalTimeoutWitnessSize 156 bytes
// - number_of_witness_elements: 1 byte
// - local_delay_sig_length: 1 byte
// - local_delay_sig: 73 bytes
// - zero_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
ToLocalTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize
// ToLocalPenaltyWitnessSize 156 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - OP_TRUE: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
ToLocalPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize
// AcceptedHtlcScriptSize 139 bytes
// - OP_DUP: 1 byte
// - OP_HASH160: 1 byte
// - OP_DATA: 1 byte (RIPEMD160(SHA256(revocationkey)) length)
// - RIPEMD160(SHA256(revocationkey)): 20 bytes
// - OP_EQUAL: 1 byte
// - OP_IF: 1 byte
// - OP_CHECKSIG: 1 byte
// - OP_ELSE: 1 byte
// - OP_DATA: 1 byte (remotekey length)
// - remotekey: 33 bytes
// - OP_SWAP: 1 byte
// - OP_SIZE: 1 byte
// - 32: 1 byte
// - OP_EQUAL: 1 byte
// - OP_IF: 1 byte
// - OP_HASH160: 1 byte
// - OP_DATA: 1 byte (RIPEMD160(payment_hash) length)
// - RIPEMD160(payment_hash): 20 bytes
// - OP_EQUALVERIFY: 1 byte
// - 2: 1 byte
// - OP_SWAP: 1 byte
// - OP_DATA: 1 byte (localkey length)
// - localkey: 33 bytes
// - 2: 1 byte
// - OP_CHECKMULTISIG: 1 byte
// - OP_ELSE: 1 byte
// - OP_DROP: 1 byte
// - OP_DATA: 1 byte (cltv_expiry length)
// - cltv_expiry: 4 bytes
// - OP_CHECKLOCKTIMEVERIFY: 1 byte
// - OP_DROP: 1 byte
// - OP_CHECKSIG: 1 byte
// - OP_ENDIF: 1 byte
// - OP_ENDIF: 1 byte
AcceptedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 7*1 + 20 + 4*1 +
33 + 5*1 + 4 + 5*1
// AcceptedHtlcTimeoutWitnessSize 216
// - number_of_witness_elements: 1 byte
// - sender_sig_length: 1 byte
// - sender_sig: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script: (accepted_htlc_script)
AcceptedHtlcTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + AcceptedHtlcScriptSize
// AcceptedHtlcSuccessWitnessSize 322 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - preimage_length: 1 byte
// - preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
AcceptedHtlcSuccessWitnessSize = 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + AcceptedHtlcScriptSize
// AcceptedHtlcPenaltyWitnessSize 249 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - revocation_key_length: 1 byte
// - revocation_key: 33 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
AcceptedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + AcceptedHtlcScriptSize
// OfferedHtlcScriptSize 133 bytes
// - OP_DUP: 1 byte
// - OP_HASH160: 1 byte
// - OP_DATA: 1 byte (RIPEMD160(SHA256(revocationkey)) length)
// - RIPEMD160(SHA256(revocationkey)): 20 bytes
// - OP_EQUAL: 1 byte
// - OP_IF: 1 byte
// - OP_CHECKSIG: 1 byte
// - OP_ELSE: 1 byte
// - OP_DATA: 1 byte (remotekey length)
// - remotekey: 33 bytes
// - OP_SWAP: 1 byte
// - OP_SIZE: 1 byte
// - OP_DATA: 1 byte (32 length)
// - 32: 1 byte
// - OP_EQUAL: 1 byte
// - OP_NOTIF: 1 byte
// - OP_DROP: 1 byte
// - 2: 1 byte
// - OP_SWAP: 1 byte
// - OP_DATA: 1 byte (localkey length)
// - localkey: 33 bytes
// - 2: 1 byte
// - OP_CHECKMULTISIG: 1 byte
// - OP_ELSE: 1 byte
// - OP_HASH160: 1 byte
// - OP_DATA: 1 byte (RIPEMD160(payment_hash) length)
// - RIPEMD160(payment_hash): 20 bytes
// - OP_EQUALVERIFY: 1 byte
// - OP_CHECKSIG: 1 byte
// - OP_ENDIF: 1 byte
// - OP_ENDIF: 1 byte
OfferedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 10*1 + 33 + 5*1 + 20 + 4*1
// OfferedHtlcTimeoutWitnessSize 285 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcTimeoutWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 1 + OfferedHtlcScriptSize
// OfferedHtlcSuccessWitnessSize 317 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - receiver_sig_length: 1 byte
// - receiver_sig: 73 bytes
// - sender_sig_length: 1 byte
// - sender_sig: 73 bytes
// - payment_preimage_length: 1 byte
// - payment_preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcSuccessWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + OfferedHtlcScriptSize
// OfferedHtlcPenaltyWitnessSize 243 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - revocation_key_length: 1 byte
// - revocation_key: 33 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + OfferedHtlcScriptSize
)
// estimateCommitTxWeight estimate commitment transaction weight depending on
// the precalculated weight of base transaction, witness data, which is needed
// for paying for funding tx, and htlc weight multiplied by their count.
func estimateCommitTxWeight(count int, prediction bool) int64 {
// Make prediction about the size of commitment transaction with
// additional HTLC.
if prediction {
count++
}
htlcWeight := int64(count * HTLCWeight)
baseWeight := int64(BaseCommitmentTxWeight)
witnessWeight := int64(WitnessCommitmentTxWeight)
return htlcWeight + baseWeight + witnessWeight
}
// TxWeightEstimator is able to calculate weight estimates for transactions
// based on the input and output types. For purposes of estimation, all
// signatures are assumed to be of the maximum possible size, 73 bytes. Each
// method of the estimator returns an instance with the estimate applied. This
// allows callers to chain each of the methods
type TxWeightEstimator struct {
hasWitness bool
inputCount uint32
outputCount uint32
inputSize int
inputWitnessSize int
outputSize int
}
// AddP2PKHInput updates the weight estimate to account for an additional input
// spending a P2PKH output.
func (twe *TxWeightEstimator) AddP2PKHInput() *TxWeightEstimator {
twe.inputSize += InputSize + P2PKHScriptSigSize
twe.inputWitnessSize++
twe.inputCount++
return twe
}
// AddP2WKHInput updates the weight estimate to account for an additional input
// spending a native P2PWKH output.
func (twe *TxWeightEstimator) AddP2WKHInput() *TxWeightEstimator {
twe.AddWitnessInput(P2WKHWitnessSize)
return twe
}
// AddWitnessInput updates the weight estimate to account for an additional
// input spending a native pay-to-witness output. This accepts the total size
// of the witness as a parameter.
func (twe *TxWeightEstimator) AddWitnessInput(witnessSize int) *TxWeightEstimator {
twe.inputSize += InputSize
twe.inputWitnessSize += witnessSize
twe.inputCount++
twe.hasWitness = true
return twe
}
// AddNestedP2WKHInput updates the weight estimate to account for an additional
// input spending a P2SH output with a nested P2WKH redeem script.
func (twe *TxWeightEstimator) AddNestedP2WKHInput() *TxWeightEstimator {
twe.inputSize += InputSize + P2WPKHSize
twe.inputWitnessSize += P2WKHWitnessSize
twe.inputSize++
twe.hasWitness = true
return twe
}
// AddNestedP2WSHInput updates the weight estimate to account for an additional
// input spending a P2SH output with a nested P2WSH redeem script.
func (twe *TxWeightEstimator) AddNestedP2WSHInput(witnessSize int) *TxWeightEstimator {
twe.inputSize += InputSize + P2WSHSize
twe.inputWitnessSize += witnessSize
twe.inputSize++
twe.hasWitness = true
return twe
}
// AddP2PKHOutput updates the weight estimate to account for an additional P2PKH
// output.
func (twe *TxWeightEstimator) AddP2PKHOutput() *TxWeightEstimator {
twe.outputSize += P2PKHOutputSize
twe.outputCount++
return twe
}
// AddP2WKHOutput updates the weight estimate to account for an additional
// native P2WKH output.
func (twe *TxWeightEstimator) AddP2WKHOutput() *TxWeightEstimator {
twe.outputSize += P2WKHOutputSize
twe.outputCount++
return twe
}
// AddP2WSHOutput updates the weight estimate to account for an additional
// native P2WSH output.
func (twe *TxWeightEstimator) AddP2WSHOutput() *TxWeightEstimator {
twe.outputSize += P2WSHOutputSize
twe.outputCount++
return twe
}
// AddP2SHOutput updates the weight estimate to account for an additional P2SH
// output.
func (twe *TxWeightEstimator) AddP2SHOutput() *TxWeightEstimator {
twe.outputSize += P2SHOutputSize
twe.outputCount++
return twe
}
// Weight gets the estimated weight of the transaction.
func (twe *TxWeightEstimator) Weight() int {
txSizeStripped := BaseTxSize +
wire.VarIntSerializeSize(uint64(twe.inputCount)) + twe.inputSize +
wire.VarIntSerializeSize(uint64(twe.outputCount)) + twe.outputSize
weight := txSizeStripped * witnessScaleFactor
if twe.hasWitness {
weight += WitnessHeaderSize + twe.inputWitnessSize
}
return weight
}
// VSize gets the estimated virtual size of the transactions, in vbytes.
func (twe *TxWeightEstimator) VSize() int {
// A tx's vsize is 1/4 of the weight, rounded up.
return (twe.Weight() + witnessScaleFactor - 1) / witnessScaleFactor
}