118 lines
4.3 KiB
Go
118 lines
4.3 KiB
Go
// Copyright (c) 2013-2017 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package blockchain
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import (
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"fmt"
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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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)
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const (
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// MaxBlockWeight defines the maximum block weight, where "block
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// weight" is interpreted as defined in BIP0141. A block's weight is
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// calculated as the sum of the of bytes in the existing transactions
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// and header, plus the weight of each byte within a transaction. The
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// weight of a "base" byte is 4, while the weight of a witness byte is
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// 1. As a result, for a block to be valid, the BlockWeight MUST be
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// less than, or equal to MaxBlockWeight.
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MaxBlockWeight = 4000000
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// MaxBlockBaseSize is the maximum number of bytes within a block
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// which can be allocated to non-witness data.
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MaxBlockBaseSize = 1000000
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// MaxBlockSigOpsCost is the maximum number of signature operations
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// allowed for a block. It is calculated via a weighted algorithm which
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// weights segregated witness sig ops lower than regular sig ops.
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MaxBlockSigOpsCost = 80000
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// WitnessScaleFactor determines the level of "discount" witness data
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// receives compared to "base" data. A scale factor of 4, denotes that
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// witness data is 1/4 as cheap as regular non-witness data.
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WitnessScaleFactor = 4
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// MinTxOutputWeight is the minimum possible weight for a transaction
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// output.
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MinTxOutputWeight = WitnessScaleFactor * wire.MinTxOutPayload
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// MaxOutputsPerBlock is the maximum number of transaction outputs there
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// can be in a block of max weight size.
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MaxOutputsPerBlock = MaxBlockWeight / MinTxOutputWeight
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)
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// GetBlockWeight computes the value of the weight metric for a given block.
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// Currently the weight metric is simply the sum of the block's serialized size
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// without any witness data scaled proportionally by the WitnessScaleFactor,
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// and the block's serialized size including any witness data.
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func GetBlockWeight(blk *btcutil.Block) int64 {
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msgBlock := blk.MsgBlock()
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baseSize := msgBlock.SerializeSizeStripped()
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totalSize := msgBlock.SerializeSize()
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// (baseSize * 3) + totalSize
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return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
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}
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// GetTransactionWeight computes the value of the weight metric for a given
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// transaction. Currently the weight metric is simply the sum of the
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// transactions's serialized size without any witness data scaled
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// proportionally by the WitnessScaleFactor, and the transaction's serialized
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// size including any witness data.
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func GetTransactionWeight(tx *btcutil.Tx) int64 {
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msgTx := tx.MsgTx()
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baseSize := msgTx.SerializeSizeStripped()
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totalSize := msgTx.SerializeSize()
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// (baseSize * 3) + totalSize
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return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
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}
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// GetSigOpCost returns the unified sig op cost for the passed transaction
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// respecting current active soft-forks which modified sig op cost counting.
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// The unified sig op cost for a transaction is computed as the sum of: the
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// legacy sig op count scaled according to the WitnessScaleFactor, the sig op
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// count for all p2sh inputs scaled by the WitnessScaleFactor, and finally the
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// unscaled sig op count for any inputs spending witness programs.
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func GetSigOpCost(tx *btcutil.Tx, isCoinBaseTx bool, utxoView *UtxoViewpoint, bip16, segWit bool) (int, error) {
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numSigOps := CountSigOps(tx) * WitnessScaleFactor
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if bip16 {
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numP2SHSigOps, err := CountP2SHSigOps(tx, isCoinBaseTx, utxoView)
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if err != nil {
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return 0, nil
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}
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numSigOps += (numP2SHSigOps * WitnessScaleFactor)
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}
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if segWit && !isCoinBaseTx {
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msgTx := tx.MsgTx()
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for txInIndex, txIn := range msgTx.TxIn {
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// Ensure the referenced output is available and hasn't
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// already been spent.
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utxo := utxoView.LookupEntry(txIn.PreviousOutPoint)
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if utxo == nil || utxo.IsSpent() {
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str := fmt.Sprintf("output %v referenced from "+
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"transaction %s:%d either does not "+
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"exist or has already been spent",
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txIn.PreviousOutPoint, tx.Hash(),
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txInIndex)
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return 0, ruleError(ErrMissingTxOut, str)
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}
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witness := txIn.Witness
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sigScript := txIn.SignatureScript
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pkScript := utxo.PkScript()
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numSigOps += txscript.GetWitnessSigOpCount(sigScript, pkScript, witness)
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}
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}
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return numSigOps, nil
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}
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