// EstimateSerializeSize returns a worst case serialize size estimate for a
// signed transaction that spends inputCount number of compressed P2PKH outputs
// and contains each transaction output from txOuts. The estimated size is
// incremented for an additional P2PKH change output if addChangeOutput is true.
func EstimateSerializeSize(inputCount int, txOuts []*wire.TxOut, addChangeOutput bool) int {
changeSize := 0
outputCount := len(txOuts)
if addChangeOutput {
changeSize = P2PKHOutputSize
outputCount++
}
// 8 additional bytes are for version and locktime
return 8 + wire.VarIntSerializeSize(uint64(inputCount)) +
wire.VarIntSerializeSize(uint64(outputCount)) +
inputCount*RedeemP2PKHInputSize +
h.SumOutputSerializeSizes(txOuts) +
changeSize
}
// TestVarIntWire tests the serialize size for variable length integers.
func TestVarIntSerializeSize(t *testing.T) {
tests := []struct {
val uint64 // Value to get the serialized size for
size int // Expected serialized size
}{
// Single byte
{0, 1},
// Max single byte
{0xfc, 1},
// Min 2-byte
{0xfd, 3},
// Max 2-byte
{0xffff, 3},
// Min 4-byte
{0x10000, 5},
// Max 4-byte
{0xffffffff, 5},
// Min 8-byte
{0x100000000, 9},
// Max 8-byte
{0xffffffffffffffff, 9},
}
t.Logf("Running %d tests", len(tests))
for i, test := range tests {
serializedSize := wire.VarIntSerializeSize(test.val)
if serializedSize != test.size {
t.Errorf("VarIntSerializeSize #%d got: %d, want: %d", i,
serializedSize, test.size)
continue
}
}
}
// calculateTxSize returns an estimate of the serialized size (in bytes) of the
// given transaction. It assumes all tx inputs are P2SH multi-sig.
func calculateTxSize(tx *withdrawalTx) int {
msgtx := tx.toMsgTx()
// Assume that there will always be a change output, for simplicity. We
// simulate that by simply copying the first output as all we care about is
// the size of its serialized form, which should be the same for all of them
// as they're either P2PKH or P2SH..
if !tx.hasChange() {
msgtx.AddTxOut(msgtx.TxOut[0])
}
// Craft a SignatureScript with dummy signatures for every input in this tx
// so that we can use msgtx.SerializeSize() to get its size and don't need
// to rely on estimations.
for i, txin := range msgtx.TxIn {
// 1 byte for the OP_FALSE opcode, then 73+1 bytes for each signature
// with their OP_DATA opcode and finally the redeem script + 1 byte
// for its OP_PUSHDATA opcode and N bytes for the redeem script's size.
// Notice that we use 73 as the signature length as that's the maximum
// length they may have:
// https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm
addr := tx.inputs[i].addr
redeemScriptLen := len(addr.redeemScript())
n := wire.VarIntSerializeSize(uint64(redeemScriptLen))
sigScriptLen := 1 + (74 * int(addr.series().reqSigs)) + redeemScriptLen + 1 + n
txin.SignatureScript = bytes.Repeat([]byte{1}, sigScriptLen)
}
return msgtx.SerializeSize()
}
// IsDustAmount determines whether a transaction output value and script length would
// cause the output to be considered dust. Transactions with dust outputs are
// not standard and are rejected by mempools with default policies.
func IsDustAmount(amount btcutil.Amount, scriptSize int, relayFeePerKb btcutil.Amount) bool {
// Calculate the total (estimated) cost to the network. This is
// calculated using the serialize size of the output plus the serial
// size of a transaction input which redeems it. The output is assumed
// to be compressed P2PKH as this is the most common script type. Use
// the average size of a compressed P2PKH redeem input (148) rather than
// the largest possible (txsizes.RedeemP2PKHInputSize).
totalSize := 8 + wire.VarIntSerializeSize(uint64(scriptSize)) +
scriptSize + 148
// Dust is defined as an output value where the total cost to the network
// (output size + input size) is greater than 1/3 of the relay fee.
return int64(amount)*1000/(3*int64(totalSize)) < int64(relayFeePerKb)
}
// NewBlockTemplate returns a new block template that is ready to be solved
// using the transactions from the passed transaction memory pool and a coinbase
// that either pays to the passed address if it is not nil, or a coinbase that
// is redeemable by anyone if the passed address is nil. The nil address
// functionality is useful since there are cases such as the getblocktemplate
// RPC where external mining software is responsible for creating their own
// coinbase which will replace the one generated for the block template. Thus
// the need to have configured address can be avoided.
//
// The transactions selected and included are prioritized according to several
// factors. First, each transaction has a priority calculated based on its
// value, age of inputs, and size. Transactions which consist of larger
// amounts, older inputs, and small sizes have the highest priority. Second, a
// fee per kilobyte is calculated for each transaction. Transactions with a
// higher fee per kilobyte are preferred. Finally, the block generation related
// configuration options are all taken into account.
//
// Transactions which only spend outputs from other transactions already in the
// block chain are immediately added to a priority queue which either
// prioritizes based on the priority (then fee per kilobyte) or the fee per
// kilobyte (then priority) depending on whether or not the BlockPrioritySize
// configuration option allots space for high-priority transactions.
// Transactions which spend outputs from other transactions in the memory pool
// are added to a dependency map so they can be added to the priority queue once
// the transactions they depend on have been included.
//
// Once the high-priority area (if configured) has been filled with transactions,
// or the priority falls below what is considered high-priority, the priority
// queue is updated to prioritize by fees per kilobyte (then priority).
//
// When the fees per kilobyte drop below the TxMinFreeFee configuration option,
// the transaction will be skipped unless there is a BlockMinSize set, in which
// case the block will be filled with the low-fee/free transactions until the
// block size reaches that minimum size.
//
// Any transactions which would cause the block to exceed the BlockMaxSize
// configuration option, exceed the maximum allowed signature operations per
// block, or otherwise cause the block to be invalid are skipped.
//
// Given the above, a block generated by this function is of the following form:
//
// ----------------------------------- -- --
// | Coinbase Transaction | | |
// |-----------------------------------| | |
// | | | | ----- cfg.BlockPrioritySize
// | High-priority Transactions | | |
// | | | |
// |-----------------------------------| | --
// | | |
// | | |
// | | |--- cfg.BlockMaxSize
// | Transactions prioritized by fee | |
// | until <= cfg.TxMinFreeFee | |
// | | |
// | | |
// | | |
// |-----------------------------------| |
// | Low-fee/Non high-priority (free) | |
// | transactions (while block size | |
// | <= cfg.BlockMinSize) | |
// ----------------------------------- --
func NewBlockTemplate(server *server, payToAddress btcutil.Address) (*BlockTemplate, error) {
blockManager := server.blockManager
timeSource := server.timeSource
chainState := &blockManager.chainState
// Extend the most recently known best block.
chainState.Lock()
prevHash := chainState.newestHash
nextBlockHeight := chainState.newestHeight + 1
chainState.Unlock()
// Create a standard coinbase transaction paying to the provided
// address. NOTE: The coinbase value will be updated to include the
// fees from the selected transactions later after they have actually
// been selected. It is created here to detect any errors early
// before potentially doing a lot of work below. The extra nonce helps
// ensure the transaction is not a duplicate transaction (paying the
// same value to the same public key address would otherwise be an
// identical transaction for block version 1).
extraNonce := uint64(0)
coinbaseScript, err := standardCoinbaseScript(nextBlockHeight, extraNonce)
if err != nil {
return nil, err
}
coinbaseTx, err := createCoinbaseTx(coinbaseScript, nextBlockHeight,
payToAddress)
if err != nil {
return nil, err
}
numCoinbaseSigOps := int64(blockchain.CountSigOps(coinbaseTx))
// Get the current memory pool transactions and create a priority queue
// to hold the transactions which are ready for inclusion into a block
// along with some priority related and fee metadata. Reserve the same
// number of items that are in the memory pool for the priority queue.
// Also, choose the initial sort order for the priority queue based on
// whether or not there is an area allocated for high-priority
// transactions.
mempoolTxns := server.txMemPool.TxDescs()
sortedByFee := cfg.BlockPrioritySize == 0
priorityQueue := newTxPriorityQueue(len(mempoolTxns), sortedByFee)
// Create a slice to hold the transactions to be included in the
// generated block with reserved space. Also create a transaction
// store to house all of the input transactions so multiple lookups
// can be avoided.
blockTxns := make([]*btcutil.Tx, 0, len(mempoolTxns))
blockTxns = append(blockTxns, coinbaseTx)
blockTxStore := make(blockchain.TxStore)
// dependers is used to track transactions which depend on another
// transaction in the memory pool. This, in conjunction with the
// dependsOn map kept with each dependent transaction helps quickly
// determine which dependent transactions are now eligible for inclusion
// in the block once each transaction has been included.
dependers := make(map[wire.ShaHash]*list.List)
// Create slices to hold the fees and number of signature operations
// for each of the selected transactions and add an entry for the
// coinbase. This allows the code below to simply append details about
// a transaction as it is selected for inclusion in the final block.
// However, since the total fees aren't known yet, use a dummy value for
// the coinbase fee which will be updated later.
txFees := make([]int64, 0, len(mempoolTxns))
txSigOpCounts := make([]int64, 0, len(mempoolTxns))
txFees = append(txFees, -1) // Updated once known
txSigOpCounts = append(txSigOpCounts, numCoinbaseSigOps)
minrLog.Debugf("Considering %d mempool transactions for inclusion to "+
"new block", len(mempoolTxns))
mempoolLoop:
for _, txDesc := range mempoolTxns {
// A block can't have more than one coinbase or contain
// non-finalized transactions.
tx := txDesc.Tx
if blockchain.IsCoinBase(tx) {
minrLog.Tracef("Skipping coinbase tx %s", tx.Sha())
continue
}
if !blockchain.IsFinalizedTransaction(tx, nextBlockHeight,
timeSource.AdjustedTime()) {
minrLog.Tracef("Skipping non-finalized tx %s", tx.Sha())
continue
}
// Fetch all of the transactions referenced by the inputs to
// this transaction. NOTE: This intentionally does not fetch
// inputs from the mempool since a transaction which depends on
// other transactions in the mempool must come after those
// dependencies in the final generated block.
txStore, err := blockManager.FetchTransactionStore(tx)
if err != nil {
minrLog.Warnf("Unable to fetch transaction store for "+
"tx %s: %v", tx.Sha(), err)
continue
}
// Setup dependencies for any transactions which reference
// other transactions in the mempool so they can be properly
// ordered below.
prioItem := &txPrioItem{tx: txDesc.Tx}
for _, txIn := range tx.MsgTx().TxIn {
originHash := &txIn.PreviousOutPoint.Hash
originIndex := txIn.PreviousOutPoint.Index
txData, exists := txStore[*originHash]
if !exists || txData.Err != nil || txData.Tx == nil {
if !server.txMemPool.HaveTransaction(originHash) {
minrLog.Tracef("Skipping tx %s because "+
"it references tx %s which is "+
"not available", tx.Sha,
originHash)
continue mempoolLoop
}
// The transaction is referencing another
// transaction in the memory pool, so setup an
// ordering dependency.
depList, exists := dependers[*originHash]
if !exists {
depList = list.New()
dependers[*originHash] = depList
}
depList.PushBack(prioItem)
if prioItem.dependsOn == nil {
prioItem.dependsOn = make(
map[wire.ShaHash]struct{})
}
prioItem.dependsOn[*originHash] = struct{}{}
// Skip the check below. We already know the
// referenced transaction is available.
continue
}
// Ensure the output index in the referenced transaction
// is available.
msgTx := txData.Tx.MsgTx()
if originIndex > uint32(len(msgTx.TxOut)) {
minrLog.Tracef("Skipping tx %s because "+
"it references output %d of tx %s "+
"which is out of bounds", tx.Sha,
originIndex, originHash)
continue mempoolLoop
}
}
// Calculate the final transaction priority using the input
// value age sum as well as the adjusted transaction size. The
// formula is: sum(inputValue * inputAge) / adjustedTxSize
prioItem.priority = txDesc.CurrentPriority(txStore, nextBlockHeight)
// Calculate the fee in Satoshi/KB.
// NOTE: This is a more precise value than the one calculated
// during calcMinRelayFee which rounds up to the nearest full
// kilobyte boundary. This is beneficial since it provides an
// incentive to create smaller transactions.
txSize := tx.MsgTx().SerializeSize()
prioItem.feePerKB = float64(txDesc.Fee) / (float64(txSize) / 1000)
prioItem.fee = txDesc.Fee
// Add the transaction to the priority queue to mark it ready
// for inclusion in the block unless it has dependencies.
if prioItem.dependsOn == nil {
heap.Push(priorityQueue, prioItem)
}
// Merge the store which contains all of the input transactions
// for this transaction into the input transaction store. This
// allows the code below to avoid a second lookup.
mergeTxStore(blockTxStore, txStore)
}
minrLog.Tracef("Priority queue len %d, dependers len %d",
priorityQueue.Len(), len(dependers))
// The starting block size is the size of the block header plus the max
// possible transaction count size, plus the size of the coinbase
// transaction.
blockSize := blockHeaderOverhead + uint32(coinbaseTx.MsgTx().SerializeSize())
blockSigOps := numCoinbaseSigOps
totalFees := int64(0)
// Choose which transactions make it into the block.
for priorityQueue.Len() > 0 {
// Grab the highest priority (or highest fee per kilobyte
// depending on the sort order) transaction.
prioItem := heap.Pop(priorityQueue).(*txPrioItem)
tx := prioItem.tx
// Grab the list of transactions which depend on this one (if
// any) and remove the entry for this transaction as it will
// either be included or skipped, but in either case the deps
// are no longer needed.
deps := dependers[*tx.Sha()]
delete(dependers, *tx.Sha())
// Enforce maximum block size. Also check for overflow.
txSize := uint32(tx.MsgTx().SerializeSize())
blockPlusTxSize := blockSize + txSize
if blockPlusTxSize < blockSize || blockPlusTxSize >= cfg.BlockMaxSize {
minrLog.Tracef("Skipping tx %s because it would exceed "+
"the max block size", tx.Sha())
logSkippedDeps(tx, deps)
continue
}
// Enforce maximum signature operations per block. Also check
// for overflow.
numSigOps := int64(blockchain.CountSigOps(tx))
if blockSigOps+numSigOps < blockSigOps ||
blockSigOps+numSigOps > blockchain.MaxSigOpsPerBlock {
minrLog.Tracef("Skipping tx %s because it would "+
"exceed the maximum sigops per block", tx.Sha())
logSkippedDeps(tx, deps)
continue
}
numP2SHSigOps, err := blockchain.CountP2SHSigOps(tx, false,
blockTxStore)
if err != nil {
minrLog.Tracef("Skipping tx %s due to error in "+
"CountP2SHSigOps: %v", tx.Sha(), err)
logSkippedDeps(tx, deps)
continue
}
numSigOps += int64(numP2SHSigOps)
if blockSigOps+numSigOps < blockSigOps ||
blockSigOps+numSigOps > blockchain.MaxSigOpsPerBlock {
minrLog.Tracef("Skipping tx %s because it would "+
"exceed the maximum sigops per block (p2sh)",
tx.Sha())
logSkippedDeps(tx, deps)
continue
}
// Skip free transactions once the block is larger than the
// minimum block size.
if sortedByFee &&
prioItem.feePerKB < float64(cfg.minRelayTxFee) &&
blockPlusTxSize >= cfg.BlockMinSize {
minrLog.Tracef("Skipping tx %s with feePerKB %.2f "+
"< minTxRelayFee %d and block size %d >= "+
"minBlockSize %d", tx.Sha(), prioItem.feePerKB,
cfg.minRelayTxFee, blockPlusTxSize,
cfg.BlockMinSize)
logSkippedDeps(tx, deps)
continue
}
// Prioritize by fee per kilobyte once the block is larger than
// the priority size or there are no more high-priority
// transactions.
if !sortedByFee && (blockPlusTxSize >= cfg.BlockPrioritySize ||
prioItem.priority <= minHighPriority) {
minrLog.Tracef("Switching to sort by fees per "+
"kilobyte blockSize %d >= BlockPrioritySize "+
"%d || priority %.2f <= minHighPriority %.2f",
blockPlusTxSize, cfg.BlockPrioritySize,
prioItem.priority, minHighPriority)
sortedByFee = true
priorityQueue.SetLessFunc(txPQByFee)
// Put the transaction back into the priority queue and
// skip it so it is re-priortized by fees if it won't
// fit into the high-priority section or the priority is
// too low. Otherwise this transaction will be the
// final one in the high-priority section, so just fall
// though to the code below so it is added now.
if blockPlusTxSize > cfg.BlockPrioritySize ||
prioItem.priority < minHighPriority {
heap.Push(priorityQueue, prioItem)
continue
}
}
// Ensure the transaction inputs pass all of the necessary
// preconditions before allowing it to be added to the block.
_, err = blockchain.CheckTransactionInputs(tx, nextBlockHeight,
blockTxStore)
if err != nil {
minrLog.Tracef("Skipping tx %s due to error in "+
"CheckTransactionInputs: %v", tx.Sha(), err)
logSkippedDeps(tx, deps)
continue
}
err = blockchain.ValidateTransactionScripts(tx, blockTxStore,
txscript.StandardVerifyFlags, server.sigCache)
if err != nil {
minrLog.Tracef("Skipping tx %s due to error in "+
"ValidateTransactionScripts: %v", tx.Sha(), err)
logSkippedDeps(tx, deps)
continue
}
// Spend the transaction inputs in the block transaction store
// and add an entry for it to ensure any transactions which
// reference this one have it available as an input and can
// ensure they aren't double spending.
spendTransaction(blockTxStore, tx, nextBlockHeight)
// Add the transaction to the block, increment counters, and
// save the fees and signature operation counts to the block
// template.
blockTxns = append(blockTxns, tx)
blockSize += txSize
blockSigOps += numSigOps
totalFees += prioItem.fee
txFees = append(txFees, prioItem.fee)
txSigOpCounts = append(txSigOpCounts, numSigOps)
minrLog.Tracef("Adding tx %s (priority %.2f, feePerKB %.2f)",
prioItem.tx.Sha(), prioItem.priority, prioItem.feePerKB)
// Add transactions which depend on this one (and also do not
// have any other unsatisified dependencies) to the priority
// queue.
if deps != nil {
for e := deps.Front(); e != nil; e = e.Next() {
// Add the transaction to the priority queue if
// there are no more dependencies after this
// one.
item := e.Value.(*txPrioItem)
delete(item.dependsOn, *tx.Sha())
if len(item.dependsOn) == 0 {
heap.Push(priorityQueue, item)
}
}
}
}
// Now that the actual transactions have been selected, update the
// block size for the real transaction count and coinbase value with
// the total fees accordingly.
blockSize -= wire.MaxVarIntPayload -
uint32(wire.VarIntSerializeSize(uint64(len(blockTxns))))
coinbaseTx.MsgTx().TxOut[0].Value += totalFees
txFees[0] = -totalFees
// Calculate the required difficulty for the block. The timestamp
// is potentially adjusted to ensure it comes after the median time of
// the last several blocks per the chain consensus rules.
ts, err := medianAdjustedTime(chainState, timeSource)
if err != nil {
return nil, err
}
requiredDifficulty, err := blockManager.CalcNextRequiredDifficulty(ts)
if err != nil {
return nil, err
}
// Create a new block ready to be solved.
merkles := blockchain.BuildMerkleTreeStore(blockTxns)
var msgBlock wire.MsgBlock
msgBlock.Header = wire.BlockHeader{
Version: generatedBlockVersion,
PrevBlock: *prevHash,
MerkleRoot: *merkles[len(merkles)-1],
Timestamp: ts,
Bits: requiredDifficulty,
}
for _, tx := range blockTxns {
if err := msgBlock.AddTransaction(tx.MsgTx()); err != nil {
return nil, err
}
}
// Finally, perform a full check on the created block against the chain
// consensus rules to ensure it properly connects to the current best
// chain with no issues.
block := btcutil.NewBlock(&msgBlock)
block.SetHeight(nextBlockHeight)
if err := blockManager.CheckConnectBlock(block); err != nil {
return nil, err
}
minrLog.Debugf("Created new block template (%d transactions, %d in "+
"fees, %d signature operations, %d bytes, target difficulty "+
"%064x)", len(msgBlock.Transactions), totalFees, blockSigOps,
blockSize, blockchain.CompactToBig(msgBlock.Header.Bits))
return &BlockTemplate{
block: &msgBlock,
fees: txFees,
sigOpCounts: txSigOpCounts,
height: nextBlockHeight,
validPayAddress: payToAddress != nil,
}, nil
}