// CalcPriority returns a transaction priority given a transaction and the sum
// of each of its input values multiplied by their age (# of confirmations).
// Thus, the final formula for the priority is:
// sum(inputValue * inputAge) / adjustedTxSize
func CalcPriority(tx *wire.MsgTx, utxoView *blockchain.UtxoViewpoint, nextBlockHeight int32) float64 {
// In order to encourage spending multiple old unspent transaction
// outputs thereby reducing the total set, don't count the constant
// overhead for each input as well as enough bytes of the signature
// script to cover a pay-to-script-hash redemption with a compressed
// pubkey. This makes additional inputs free by boosting the priority
// of the transaction accordingly. No more incentive is given to avoid
// encouraging gaming future transactions through the use of junk
// outputs. This is the same logic used in the reference
// implementation.
//
// The constant overhead for a txin is 41 bytes since the previous
// outpoint is 36 bytes + 4 bytes for the sequence + 1 byte the
// signature script length.
//
// A compressed pubkey pay-to-script-hash redemption with a maximum len
// signature is of the form:
// [OP_DATA_73 <73-byte sig> + OP_DATA_35 + {OP_DATA_33
// <33 byte compresed pubkey> + OP_CHECKSIG}]
//
// Thus 1 + 73 + 1 + 1 + 33 + 1 = 110
overhead := 0
for _, txIn := range tx.TxIn {
// Max inputs + size can't possibly overflow here.
overhead += 41 + minInt(110, len(txIn.SignatureScript))
}
serializedTxSize := tx.SerializeSize()
if overhead >= serializedTxSize {
return 0.0
}
inputValueAge := calcInputValueAge(tx, utxoView, nextBlockHeight)
return inputValueAge / float64(serializedTxSize-overhead)
}
// NewTxRecordFromMsgTx creates a new transaction record that may be inserted
// into the store.
func NewTxRecordFromMsgTx(msgTx *wire.MsgTx, received time.Time) (*TxRecord, error) {
buf := bytes.NewBuffer(make([]byte, 0, msgTx.SerializeSize()))
err := msgTx.Serialize(buf)
if err != nil {
str := "failed to serialize transaction"
return nil, storeError(ErrInput, str, err)
}
rec := &TxRecord{
MsgTx: *msgTx,
Received: received,
SerializedTx: buf.Bytes(),
Hash: msgTx.TxSha(),
}
return rec, nil
}
// BUGS:
// - InputIndexes request field is ignored.
func (s *walletServer) SignTransaction(ctx context.Context, req *pb.SignTransactionRequest) (
*pb.SignTransactionResponse, error) {
defer zero.Bytes(req.Passphrase)
var tx wire.MsgTx
err := tx.Deserialize(bytes.NewReader(req.SerializedTransaction))
if err != nil {
return nil, grpc.Errorf(codes.InvalidArgument,
"Bytes do not represent a valid raw transaction: %v", err)
}
lock := make(chan time.Time, 1)
defer func() {
lock <- time.Time{} // send matters, not the value
}()
err = s.wallet.Unlock(req.Passphrase, lock)
if err != nil {
return nil, translateError(err)
}
invalidSigs, err := s.wallet.SignTransaction(&tx, txscript.SigHashAll, nil, nil, nil)
if err != nil {
return nil, translateError(err)
}
invalidInputIndexes := make([]uint32, len(invalidSigs))
for i, e := range invalidSigs {
invalidInputIndexes[i] = e.InputIndex
}
var serializedTransaction bytes.Buffer
serializedTransaction.Grow(tx.SerializeSize())
err = tx.Serialize(&serializedTransaction)
if err != nil {
return nil, translateError(err)
}
resp := &pb.SignTransactionResponse{
Transaction: serializedTransaction.Bytes(),
UnsignedInputIndexes: invalidInputIndexes,
}
return resp, nil
}
// TxToString prints out some info about a transaction. for testing / debugging
func TxToString(tx *wire.MsgTx) string {
str := fmt.Sprintf("size %d vsize %d wsize %d locktime %d txid %s\n",
tx.SerializeSize(), blockchain.GetTxVirtualSize(btcutil.NewTx(tx)),
tx.SerializeSize(), tx.LockTime, tx.TxSha().String())
for i, in := range tx.TxIn {
str += fmt.Sprintf("Input %d spends %s\n", i, in.PreviousOutPoint.String())
str += fmt.Sprintf("\tSigScript: %x\n", in.SignatureScript)
for j, wit := range in.Witness {
str += fmt.Sprintf("\twitness %d: %x\n", j, wit)
}
}
for i, out := range tx.TxOut {
if out != nil {
str += fmt.Sprintf("output %d script: %x amt: %d\n",
i, out.PkScript, out.Value)
} else {
str += fmt.Sprintf("output %d nil (WARNING)\n", i)
}
}
return str
}
// fundTx attempts to fund a transaction sending amt bitcoin. The coins are
// selected such that the final amount spent pays enough fees as dictated by
// the passed fee rate. The passed fee rate should be expressed in
// satoshis-per-byte.
//
// NOTE: The memWallet's mutex must be held when this function is called.
func (m *memWallet) fundTx(tx *wire.MsgTx, amt btcutil.Amount, feeRate btcutil.Amount) error {
const (
// spendSize is the largest number of bytes of a sigScript
// which spends a p2pkh output: OP_DATA_73 <sig> OP_DATA_33 <pubkey>
spendSize = 1 + 73 + 1 + 33
)
var (
amtSelected btcutil.Amount
txSize int
)
for outPoint, utxo := range m.utxos {
// Skip any outputs that are still currently immature or are
// currently locked.
if !utxo.isMature(m.currentHeight) || utxo.isLocked {
continue
}
amtSelected += utxo.value
// Add the selected output to the transaction, updating the
// current tx size while accounting for the size of the future
// sigScript.
tx.AddTxIn(wire.NewTxIn(&outPoint, nil, nil))
txSize = tx.SerializeSize() + spendSize*len(tx.TxIn)
// Calculate the fee required for the txn at this point
// observing the specified fee rate. If we don't have enough
// coins from he current amount selected to pay the fee, then
// continue to grab more coins.
reqFee := btcutil.Amount(txSize * int(feeRate))
if amtSelected-reqFee < amt {
continue
}
// If we have any change left over, then add an additional
// output to the transaction reserved for change.
changeVal := amtSelected - amt - reqFee
if changeVal > 0 {
addr, err := m.newAddress()
if err != nil {
return err
}
pkScript, err := txscript.PayToAddrScript(addr)
if err != nil {
return err
}
changeOutput := &wire.TxOut{
Value: int64(changeVal),
PkScript: pkScript,
}
tx.AddTxOut(changeOutput)
}
return nil
}
// If we've reached this point, then coin selection failed due to an
// insufficient amount of coins.
return fmt.Errorf("not enough funds for coin selection")
}
