141 lines
4.3 KiB
Go
141 lines
4.3 KiB
Go
package lnwallet
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import (
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"github.com/roasbeef/btcd/blockchain"
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)
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const (
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// The weight(weight), which is different from the !size! (see BIP-141),
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// is calculated as:
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// Weight = 4 * BaseSize + WitnessSize (weight).
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// BaseSize - size of the transaction without witness data (bytes).
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// WitnessSize - witness size (bytes).
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// Weight - the metric for determining the weight of the transaction.
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// P2WSHSize 34 bytes
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// - OP_0: 1 byte
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// - OP_DATA: 1 byte (WitnessScriptSHA256 length)
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// - WitnessScriptSHA256: 32 bytes
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P2WSHSize = 1 + 1 + 32
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// P2WPKHSize 22 bytes
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// - OP_0: 1 byte
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// - OP_DATA: 1 byte (PublicKeyHASH160 length)
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// - PublicKeyHASH160: 20 bytes
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P2WPKHSize = 1 + 1 + 20
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// MultiSigSize 71 bytes
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// - OP_2: 1 byte
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// - OP_DATA: 1 byte (pubKeyAlice length)
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// - pubKeyAlice: 33 bytes
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// - OP_DATA: 1 byte (pubKeyBob length)
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// - pubKeyBob: 33 bytes
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// - OP_2: 1 byte
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// - OP_CHECKMULTISIG: 1 byte
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MultiSigSize = 1 + 1 + 33 + 1 + 33 + 1 + 1
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// WitnessSize 222 bytes
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// - NumberOfWitnessElements: 1 byte
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// - NilLength: 1 byte
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// - sigAliceLength: 1 byte
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// - sigAlice: 73 bytes
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// - sigBobLength: 1 byte
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// - sigBob: 73 bytes
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// - WitnessScriptLength: 1 byte
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// - WitnessScript (MultiSig)
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WitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + MultiSigSize
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// FundingInputSize 41 bytes
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// - PreviousOutPoint:
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// - Hash: 32 bytes
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// - Index: 4 bytes
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// - OP_DATA: 1 byte (ScriptSigLength)
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// - ScriptSig: 0 bytes
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// - Witness <---- we use "Witness" instead of "ScriptSig" for
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// transaction validation, but "Witness" is stored
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// separately and weight for it size is smaller. So
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// we separate the calculation of ordinary data
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// from witness data.
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// - Sequence: 4 bytes
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FundingInputSize = 32 + 4 + 1 + 4
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// CommitmentDelayOutput 43 bytes
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// - Value: 8 bytes
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// - VarInt: 1 byte (PkScript length)
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// - PkScript (P2WSH)
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CommitmentDelayOutput = 8 + 1 + P2WSHSize
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// CommitmentKeyHashOutput 31 bytes
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// - Value: 8 bytes
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// - VarInt: 1 byte (PkScript length)
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// - PkScript (P2WPKH)
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CommitmentKeyHashOutput = 8 + 1 + P2WPKHSize
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// HTLCSize 43 bytes
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// - Value: 8 bytes
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// - VarInt: 1 byte (PkScript length)
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// - PkScript (PW2SH)
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HTLCSize = 8 + 1 + P2WSHSize
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// WitnessHeaderSize 2 bytes
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// - Flag: 1 byte
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// - Marker: 1 byte
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WitnessHeaderSize = 1 + 1
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// BaseCommitmentTxSize 125 43 * num-htlc-outputs bytes
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// - Version: 4 bytes
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// - WitnessHeader <---- part of the witness data
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// - CountTxIn: 1 byte
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// - TxIn: 41 bytes
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// FundingInput
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// - CountTxOut: 1 byte
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// - TxOut: 74 + 43 * num-htlc-outputs bytes
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// OutputPayingToThem,
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// OutputPayingToUs,
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// ....HTLCOutputs...
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// - LockTime: 4 bytes
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BaseCommitmentTxSize = 4 + 1 + FundingInputSize + 1 +
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CommitmentDelayOutput + CommitmentKeyHashOutput + 4
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// BaseCommitmentTxWeight 500 weight
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BaseCommitmentTxWeight = blockchain.WitnessScaleFactor * BaseCommitmentTxSize
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// WitnessCommitmentTxWeight 224 weight
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WitnessCommitmentTxWeight = WitnessHeaderSize + WitnessSize
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// HTLCWeight 172 weight
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HTLCWeight = blockchain.WitnessScaleFactor * HTLCSize
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// HtlcTimeoutWeight is the weight of the HTLC timeout transaction
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// which will transition an outgoing HTLC to the delay-and-claim state.
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HtlcTimeoutWeight = 663
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// HtlcSuccessWeight is the weight of the HTLC success transaction
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// which will transition an incoming HTLC to the delay-and-claim state.
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HtlcSuccessWeight = 703
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// MaxHTLCNumber is the maximum number HTLCs which can be included in a
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// commitment transaction. This limit was chosen such that, in the case
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// of a contract breach, the punishment transaction is able to sweep
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// all the HTLC's yet still remain below the widely used standard
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// weight limits.
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MaxHTLCNumber = 967
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)
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// estimateCommitTxWeight estimate commitment transaction weight depending on
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// the precalculated weight of base transaction, witness data, which is needed
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// for paying for funding tx, and htlc weight multiplied by their count.
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func estimateCommitTxWeight(count int, prediction bool) int64 {
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// Make prediction about the size of commitment transaction with
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// additional HTLC.
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if prediction {
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count++
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}
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htlcWeight := int64(count * HTLCWeight)
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baseWeight := int64(BaseCommitmentTxWeight)
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witnessWeight := int64(WitnessCommitmentTxWeight)
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return htlcWeight + baseWeight + witnessWeight
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}
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