ipld-eth-server/vendor/github.com/btcsuite/btcd/blockchain/weight.go

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// Copyright (c) 2013-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package blockchain
import (
"fmt"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcutil"
)
const (
// MaxBlockWeight defines the maximum block weight, where "block
// weight" is interpreted as defined in BIP0141. A block's weight is
// calculated as the sum of the of bytes in the existing transactions
// and header, plus the weight of each byte within a transaction. The
// weight of a "base" byte is 4, while the weight of a witness byte is
// 1. As a result, for a block to be valid, the BlockWeight MUST be
// less than, or equal to MaxBlockWeight.
MaxBlockWeight = 4000000
// MaxBlockBaseSize is the maximum number of bytes within a block
// which can be allocated to non-witness data.
MaxBlockBaseSize = 1000000
// MaxBlockSigOpsCost is the maximum number of signature operations
// allowed for a block. It is calculated via a weighted algorithm which
// weights segragated witness sig ops lower than regular sig ops.
MaxBlockSigOpsCost = 80000
// 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.
WitnessScaleFactor = 4
)
// GetBlockWeight computes the value of the weight metric for a given block.
// Currently the weight metric is simply the sum of the block's serialized size
// without any witness data scaled proportionally by the WitnessScaleFactor,
// and the block's serialized size including any witness data.
func GetBlockWeight(blk *btcutil.Block) int64 {
msgBlock := blk.MsgBlock()
baseSize := msgBlock.SerializeSizeStripped()
totalSize := msgBlock.SerializeSize()
// (baseSize * 3) + totalSize
return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
}
// GetTransactionWeight computes the value of the weight metric for a given
// transaction. Currently the weight metric is simply the sum of the
// transactions's serialized size without any witness data scaled
// proportionally by the WitnessScaleFactor, and the transaction's serialized
// size including any witness data.
func GetTransactionWeight(tx *btcutil.Tx) int64 {
msgTx := tx.MsgTx()
baseSize := msgTx.SerializeSizeStripped()
totalSize := msgTx.SerializeSize()
// (baseSize * 3) + totalSize
return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
}
// GetSigOpCost returns the unified sig op cost for the passed transaction
// respecting current active soft-forks which modified sig op cost counting.
// The unified sig op cost for a transaction is computed as the sum of: the
// legacy sig op count scaled according to the WitnessScaleFactor, the sig op
// count for all p2sh inputs scaled by the WitnessScaleFactor, and finally the
// unscaled sig op count for any inputs spending witness programs.
func GetSigOpCost(tx *btcutil.Tx, isCoinBaseTx bool, utxoView *UtxoViewpoint,
bip16, segWit bool) (int, error) {
numSigOps := CountSigOps(tx) * WitnessScaleFactor
if bip16 {
numP2SHSigOps, err := CountP2SHSigOps(tx, isCoinBaseTx, utxoView)
if err != nil {
return 0, nil
}
numSigOps += (numP2SHSigOps * WitnessScaleFactor)
}
if segWit && !isCoinBaseTx {
msgTx := tx.MsgTx()
for txInIndex, txIn := range msgTx.TxIn {
// Ensure the referenced input transaction is available.
originTxHash := &txIn.PreviousOutPoint.Hash
originTxIndex := txIn.PreviousOutPoint.Index
txEntry := utxoView.LookupEntry(originTxHash)
if txEntry == nil || txEntry.IsOutputSpent(originTxIndex) {
str := fmt.Sprintf("output %v referenced from "+
"transaction %s:%d either does not "+
"exist or has already been spent",
txIn.PreviousOutPoint, tx.Hash(),
txInIndex)
return 0, ruleError(ErrMissingTxOut, str)
}
witness := txIn.Witness
sigScript := txIn.SignatureScript
pkScript := txEntry.PkScriptByIndex(originTxIndex)
numSigOps += txscript.GetWitnessSigOpCount(sigScript, pkScript, witness)
}
}
return numSigOps, nil
}