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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 wire
import (
"bytes"
"fmt"
"io"
"strconv"
"github.com/btcsuite/btcd/chaincfg/chainhash"
)
const (
// TxVersion is the current latest supported transaction version.
TxVersion = 1
// MaxTxInSequenceNum is the maximum sequence number the sequence field
// of a transaction input can be.
MaxTxInSequenceNum uint32 = 0xffffffff
// MaxPrevOutIndex is the maximum index the index field of a previous
// outpoint can be.
MaxPrevOutIndex uint32 = 0xffffffff
// SequenceLockTimeDisabled is a flag that if set on a transaction
// input's sequence number, the sequence number will not be interpreted
// as a relative locktime.
SequenceLockTimeDisabled = 1 << 31
// SequenceLockTimeIsSeconds is a flag that if set on a transaction
// input's sequence number, the relative locktime has units of 512
// seconds.
SequenceLockTimeIsSeconds = 1 << 22
// SequenceLockTimeMask is a mask that extracts the relative locktime
// when masked against the transaction input sequence number.
SequenceLockTimeMask = 0x0000ffff
// SequenceLockTimeGranularity is the defined time based granularity
// for seconds-based relative time locks. When converting from seconds
// to a sequence number, the value is right shifted by this amount,
// therefore the granularity of relative time locks in 512 or 2^9
// seconds. Enforced relative lock times are multiples of 512 seconds.
SequenceLockTimeGranularity = 9
// defaultTxInOutAlloc is the default size used for the backing array for
// transaction inputs and outputs. The array will dynamically grow as needed,
// but this figure is intended to provide enough space for the number of
// inputs and outputs in a typical transaction without needing to grow the
// backing array multiple times.
defaultTxInOutAlloc = 15
// minTxInPayload is the minimum payload size for a transaction input.
// PreviousOutPoint.Hash + PreviousOutPoint.Index 4 bytes + Varint for
// SignatureScript length 1 byte + Sequence 4 bytes.
minTxInPayload = 9 + chainhash.HashSize
// maxTxInPerMessage is the maximum number of transactions inputs that
// a transaction which fits into a message could possibly have.
maxTxInPerMessage = (MaxMessagePayload / minTxInPayload) + 1
// MinTxOutPayload is the minimum payload size for a transaction output.
// Value 8 bytes + Varint for PkScript length 1 byte.
MinTxOutPayload = 9
// maxTxOutPerMessage is the maximum number of transactions outputs that
// a transaction which fits into a message could possibly have.
maxTxOutPerMessage = (MaxMessagePayload / MinTxOutPayload) + 1
// minTxPayload is the minimum payload size for a transaction. Note
// that any realistically usable transaction must have at least one
// input or output, but that is a rule enforced at a higher layer, so
// it is intentionally not included here.
// Version 4 bytes + Varint number of transaction inputs 1 byte + Varint
// number of transaction outputs 1 byte + LockTime 4 bytes + min input
// payload + min output payload.
minTxPayload = 10
// freeListMaxScriptSize is the size of each buffer in the free list
// that is used for deserializing scripts from the wire before they are
// concatenated into a single contiguous buffers. This value was chosen
// because it is slightly more than twice the size of the vast majority
// of all "standard" scripts. Larger scripts are still deserialized
// properly as the free list will simply be bypassed for them.
freeListMaxScriptSize = 512
// freeListMaxItems is the number of buffers to keep in the free list
// to use for script deserialization. This value allows up to 100
// scripts per transaction being simultaneously deserialized by 125
// peers. Thus, the peak usage of the free list is 12,500 * 512 =
// 6,400,000 bytes.
freeListMaxItems = 12500
// maxWitnessItemsPerInput is the maximum number of witness items to
// be read for the witness data for a single TxIn. This number is
// derived using a possble lower bound for the encoding of a witness
// item: 1 byte for length + 1 byte for the witness item itself, or two
// bytes. This value is then divided by the currently allowed maximum
// "cost" for a transaction.
maxWitnessItemsPerInput = 500000
// maxWitnessItemSize is the maximum allowed size for an item within
// an input's witness data. This number is derived from the fact that
// for script validation, each pushed item onto the stack must be less
// than 10k bytes.
maxWitnessItemSize = 11000
)
// witnessMarkerBytes are a pair of bytes specific to the witness encoding. If
// this sequence is encoutered, then it indicates a transaction has iwtness
// data. The first byte is an always 0x00 marker byte, which allows decoders to
// distinguish a serialized transaction with witnesses from a regular (legacy)
// one. The second byte is the Flag field, which at the moment is always 0x01,
// but may be extended in the future to accommodate auxiliary non-committed
// fields.
var witessMarkerBytes = []byte{0x00, 0x01}
// scriptFreeList defines a free list of byte slices (up to the maximum number
// defined by the freeListMaxItems constant) that have a cap according to the
// freeListMaxScriptSize constant. It is used to provide temporary buffers for
// deserializing scripts in order to greatly reduce the number of allocations
// required.
//
// The caller can obtain a buffer from the free list by calling the Borrow
// function and should return it via the Return function when done using it.
type scriptFreeList chan []byte
// Borrow returns a byte slice from the free list with a length according the
// provided size. A new buffer is allocated if there are any items available.
//
// When the size is larger than the max size allowed for items on the free list
// a new buffer of the appropriate size is allocated and returned. It is safe
// to attempt to return said buffer via the Return function as it will be
// ignored and allowed to go the garbage collector.
func (c scriptFreeList) Borrow(size uint64) []byte {
if size > freeListMaxScriptSize {
return make([]byte, size)
}
var buf []byte
select {
case buf = <-c:
default:
buf = make([]byte, freeListMaxScriptSize)
}
return buf[:size]
}
// Return puts the provided byte slice back on the free list when it has a cap
// of the expected length. The buffer is expected to have been obtained via
// the Borrow function. Any slices that are not of the appropriate size, such
// as those whose size is greater than the largest allowed free list item size
// are simply ignored so they can go to the garbage collector.
func (c scriptFreeList) Return(buf []byte) {
// Ignore any buffers returned that aren't the expected size for the
// free list.
if cap(buf) != freeListMaxScriptSize {
return
}
// Return the buffer to the free list when it's not full. Otherwise let
// it be garbage collected.
select {
case c <- buf:
default:
// Let it go to the garbage collector.
}
}
// Create the concurrent safe free list to use for script deserialization. As
// previously described, this free list is maintained to significantly reduce
// the number of allocations.
var scriptPool scriptFreeList = make(chan []byte, freeListMaxItems)
// OutPoint defines a bitcoin data type that is used to track previous
// transaction outputs.
type OutPoint struct {
Hash chainhash.Hash
Index uint32
}
// NewOutPoint returns a new bitcoin transaction outpoint point with the
// provided hash and index.
func NewOutPoint(hash *chainhash.Hash, index uint32) *OutPoint {
return &OutPoint{
Hash: *hash,
Index: index,
}
}
// String returns the OutPoint in the human-readable form "hash:index".
func (o OutPoint) String() string {
// Allocate enough for hash string, colon, and 10 digits. Although
// at the time of writing, the number of digits can be no greater than
// the length of the decimal representation of maxTxOutPerMessage, the
// maximum message payload may increase in the future and this
// optimization may go unnoticed, so allocate space for 10 decimal
// digits, which will fit any uint32.
buf := make([]byte, 2*chainhash.HashSize+1, 2*chainhash.HashSize+1+10)
copy(buf, o.Hash.String())
buf[2*chainhash.HashSize] = ':'
buf = strconv.AppendUint(buf, uint64(o.Index), 10)
return string(buf)
}
// TxIn defines a bitcoin transaction input.
type TxIn struct {
PreviousOutPoint OutPoint
SignatureScript []byte
Witness TxWitness
Sequence uint32
}
// SerializeSize returns the number of bytes it would take to serialize the
// the transaction input.
func (t *TxIn) SerializeSize() int {
// Outpoint Hash 32 bytes + Outpoint Index 4 bytes + Sequence 4 bytes +
// serialized varint size for the length of SignatureScript +
// SignatureScript bytes.
return 40 + VarIntSerializeSize(uint64(len(t.SignatureScript))) +
len(t.SignatureScript)
}
// NewTxIn returns a new bitcoin transaction input with the provided
// previous outpoint point and signature script with a default sequence of
// MaxTxInSequenceNum.
func NewTxIn(prevOut *OutPoint, signatureScript []byte, witness [][]byte) *TxIn {
return &TxIn{
PreviousOutPoint: *prevOut,
SignatureScript: signatureScript,
Witness: witness,
Sequence: MaxTxInSequenceNum,
}
}
// TxWitness defines the witness for a TxIn. A witness is to be interpreted as
// a slice of byte slices, or a stack with one or many elements.
type TxWitness [][]byte
// SerializeSize returns the number of bytes it would take to serialize the the
// transaction input's witness.
func (t TxWitness) SerializeSize() int {
// A varint to signal the number of elements the witness has.
n := VarIntSerializeSize(uint64(len(t)))
// For each element in the witness, we'll need a varint to signal the
// size of the element, then finally the number of bytes the element
// itself comprises.
for _, witItem := range t {
n += VarIntSerializeSize(uint64(len(witItem)))
n += len(witItem)
}
return n
}
// TxOut defines a bitcoin transaction output.
type TxOut struct {
Value int64
PkScript []byte
}
// SerializeSize returns the number of bytes it would take to serialize the
// the transaction output.
func (t *TxOut) SerializeSize() int {
// Value 8 bytes + serialized varint size for the length of PkScript +
// PkScript bytes.
return 8 + VarIntSerializeSize(uint64(len(t.PkScript))) + len(t.PkScript)
}
// NewTxOut returns a new bitcoin transaction output with the provided
// transaction value and public key script.
func NewTxOut(value int64, pkScript []byte) *TxOut {
return &TxOut{
Value: value,
PkScript: pkScript,
}
}
// MsgTx implements the Message interface and represents a bitcoin tx message.
// It is used to deliver transaction information in response to a getdata
// message (MsgGetData) for a given transaction.
//
// Use the AddTxIn and AddTxOut functions to build up the list of transaction
// inputs and outputs.
type MsgTx struct {
Version int32
TxIn []*TxIn
TxOut []*TxOut
LockTime uint32
}
// AddTxIn adds a transaction input to the message.
func (msg *MsgTx) AddTxIn(ti *TxIn) {
msg.TxIn = append(msg.TxIn, ti)
}
// AddTxOut adds a transaction output to the message.
func (msg *MsgTx) AddTxOut(to *TxOut) {
msg.TxOut = append(msg.TxOut, to)
}
// TxHash generates the Hash for the transaction.
func (msg *MsgTx) TxHash() chainhash.Hash {
// Encode the transaction and calculate double sha256 on the result.
// Ignore the error returns since the only way the encode could fail
// is being out of memory or due to nil pointers, both of which would
// cause a run-time panic.
buf := bytes.NewBuffer(make([]byte, 0, msg.SerializeSizeStripped()))
_ = msg.SerializeNoWitness(buf)
return chainhash.DoubleHashH(buf.Bytes())
}
// WitnessHash generates the hash of the transaction serialized according to
// the new witness serialization defined in BIP0141 and BIP0144. The final
// output is used within the Segregated Witness commitment of all the witnesses
// within a block. If a transaction has no witness data, then the witness hash,
// is the same as its txid.
func (msg *MsgTx) WitnessHash() chainhash.Hash {
if msg.HasWitness() {
buf := bytes.NewBuffer(make([]byte, 0, msg.SerializeSize()))
_ = msg.Serialize(buf)
return chainhash.DoubleHashH(buf.Bytes())
}
return msg.TxHash()
}
// Copy creates a deep copy of a transaction so that the original does not get
// modified when the copy is manipulated.
func (msg *MsgTx) Copy() *MsgTx {
// Create new tx and start by copying primitive values and making space
// for the transaction inputs and outputs.
newTx := MsgTx{
Version: msg.Version,
TxIn: make([]*TxIn, 0, len(msg.TxIn)),
TxOut: make([]*TxOut, 0, len(msg.TxOut)),
LockTime: msg.LockTime,
}
// Deep copy the old TxIn data.
for _, oldTxIn := range msg.TxIn {
// Deep copy the old previous outpoint.
oldOutPoint := oldTxIn.PreviousOutPoint
newOutPoint := OutPoint{}
newOutPoint.Hash.SetBytes(oldOutPoint.Hash[:])
newOutPoint.Index = oldOutPoint.Index
// Deep copy the old signature script.
var newScript []byte
oldScript := oldTxIn.SignatureScript
oldScriptLen := len(oldScript)
if oldScriptLen > 0 {
newScript = make([]byte, oldScriptLen)
copy(newScript, oldScript[:oldScriptLen])
}
// Create new txIn with the deep copied data.
newTxIn := TxIn{
PreviousOutPoint: newOutPoint,
SignatureScript: newScript,
Sequence: oldTxIn.Sequence,
}
// If the transaction is witnessy, then also copy the
// witnesses.
if len(oldTxIn.Witness) != 0 {
// Deep copy the old witness data.
newTxIn.Witness = make([][]byte, len(oldTxIn.Witness))
for i, oldItem := range oldTxIn.Witness {
newItem := make([]byte, len(oldItem))
copy(newItem, oldItem)
newTxIn.Witness[i] = newItem
}
}
// Finally, append this fully copied txin.
newTx.TxIn = append(newTx.TxIn, &newTxIn)
}
// Deep copy the old TxOut data.
for _, oldTxOut := range msg.TxOut {
// Deep copy the old PkScript
var newScript []byte
oldScript := oldTxOut.PkScript
oldScriptLen := len(oldScript)
if oldScriptLen > 0 {
newScript = make([]byte, oldScriptLen)
copy(newScript, oldScript[:oldScriptLen])
}
// Create new txOut with the deep copied data and append it to
// new Tx.
newTxOut := TxOut{
Value: oldTxOut.Value,
PkScript: newScript,
}
newTx.TxOut = append(newTx.TxOut, &newTxOut)
}
return &newTx
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
// See Deserialize for decoding transactions stored to disk, such as in a
// database, as opposed to decoding transactions from the wire.
func (msg *MsgTx) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) error {
version, err := binarySerializer.Uint32(r, littleEndian)
if err != nil {
return err
}
msg.Version = int32(version)
count, err := ReadVarInt(r, pver)
if err != nil {
return err
}
// A count of zero (meaning no TxIn's to the uninitiated) indicates
// this is a transaction with witness data.
var flag [1]byte
if count == 0 && enc == WitnessEncoding {
// Next, we need to read the flag, which is a single byte.
if _, err = io.ReadFull(r, flag[:]); err != nil {
return err
}
// At the moment, the flag MUST be 0x01. In the future other
// flag types may be supported.
if flag[0] != 0x01 {
str := fmt.Sprintf("witness tx but flag byte is %x", flag)
return messageError("MsgTx.BtcDecode", str)
}
// With the Segregated Witness specific fields decoded, we can
// now read in the actual txin count.
count, err = ReadVarInt(r, pver)
if err != nil {
return err
}
}
// Prevent more input transactions than could possibly fit into a
// message. It would be possible to cause memory exhaustion and panics
// without a sane upper bound on this count.
if count > uint64(maxTxInPerMessage) {
str := fmt.Sprintf("too many input transactions to fit into "+
"max message size [count %d, max %d]", count,
maxTxInPerMessage)
return messageError("MsgTx.BtcDecode", str)
}
// returnScriptBuffers is a closure that returns any script buffers that
// were borrowed from the pool when there are any deserialization
// errors. This is only valid to call before the final step which
// replaces the scripts with the location in a contiguous buffer and
// returns them.
returnScriptBuffers := func() {
for _, txIn := range msg.TxIn {
if txIn == nil {
continue
}
if txIn.SignatureScript != nil {
scriptPool.Return(txIn.SignatureScript)
}
for _, witnessElem := range txIn.Witness {
if witnessElem != nil {
scriptPool.Return(witnessElem)
}
}
}
for _, txOut := range msg.TxOut {
if txOut == nil || txOut.PkScript == nil {
continue
}
scriptPool.Return(txOut.PkScript)
}
}
// Deserialize the inputs.
var totalScriptSize uint64
txIns := make([]TxIn, count)
msg.TxIn = make([]*TxIn, count)
for i := uint64(0); i < count; i++ {
// The pointer is set now in case a script buffer is borrowed
// and needs to be returned to the pool on error.
ti := &txIns[i]
msg.TxIn[i] = ti
err = readTxIn(r, pver, msg.Version, ti)
if err != nil {
returnScriptBuffers()
return err
}
totalScriptSize += uint64(len(ti.SignatureScript))
}
count, err = ReadVarInt(r, pver)
if err != nil {
returnScriptBuffers()
return err
}
// Prevent more output transactions than could possibly fit into a
// message. It would be possible to cause memory exhaustion and panics
// without a sane upper bound on this count.
if count > uint64(maxTxOutPerMessage) {
returnScriptBuffers()
str := fmt.Sprintf("too many output transactions to fit into "+
"max message size [count %d, max %d]", count,
maxTxOutPerMessage)
return messageError("MsgTx.BtcDecode", str)
}
// Deserialize the outputs.
txOuts := make([]TxOut, count)
msg.TxOut = make([]*TxOut, count)
for i := uint64(0); i < count; i++ {
// The pointer is set now in case a script buffer is borrowed
// and needs to be returned to the pool on error.
to := &txOuts[i]
msg.TxOut[i] = to
err = readTxOut(r, pver, msg.Version, to)
if err != nil {
returnScriptBuffers()
return err
}
totalScriptSize += uint64(len(to.PkScript))
}
// If the transaction's flag byte isn't 0x00 at this point, then one or
// more of its inputs has accompanying witness data.
if flag[0] != 0 && enc == WitnessEncoding {
for _, txin := range msg.TxIn {
// For each input, the witness is encoded as a stack
// with one or more items. Therefore, we first read a
// varint which encodes the number of stack items.
witCount, err := ReadVarInt(r, pver)
if err != nil {
returnScriptBuffers()
return err
}
// Prevent a possible memory exhaustion attack by
// limiting the witCount value to a sane upper bound.
if witCount > maxWitnessItemsPerInput {
returnScriptBuffers()
str := fmt.Sprintf("too many witness items to fit "+
"into max message size [count %d, max %d]",
witCount, maxWitnessItemsPerInput)
return messageError("MsgTx.BtcDecode", str)
}
// Then for witCount number of stack items, each item
// has a varint length prefix, followed by the witness
// item itself.
txin.Witness = make([][]byte, witCount)
for j := uint64(0); j < witCount; j++ {
txin.Witness[j], err = readScript(r, pver,
maxWitnessItemSize, "script witness item")
if err != nil {
returnScriptBuffers()
return err
}
totalScriptSize += uint64(len(txin.Witness[j]))
}
}
}
msg.LockTime, err = binarySerializer.Uint32(r, littleEndian)
if err != nil {
returnScriptBuffers()
return err
}
// Create a single allocation to house all of the scripts and set each
// input signature script and output public key script to the
// appropriate subslice of the overall contiguous buffer. Then, return
// each individual script buffer back to the pool so they can be reused
// for future deserializations. This is done because it significantly
// reduces the number of allocations the garbage collector needs to
// track, which in turn improves performance and drastically reduces the
// amount of runtime overhead that would otherwise be needed to keep
// track of millions of small allocations.
//
// NOTE: It is no longer valid to call the returnScriptBuffers closure
// after these blocks of code run because it is already done and the
// scripts in the transaction inputs and outputs no longer point to the
// buffers.
var offset uint64
scripts := make([]byte, totalScriptSize)
for i := 0; i < len(msg.TxIn); i++ {
// Copy the signature script into the contiguous buffer at the
// appropriate offset.
signatureScript := msg.TxIn[i].SignatureScript
copy(scripts[offset:], signatureScript)
// Reset the signature script of the transaction input to the
// slice of the contiguous buffer where the script lives.
scriptSize := uint64(len(signatureScript))
end := offset + scriptSize
msg.TxIn[i].SignatureScript = scripts[offset:end:end]
offset += scriptSize
// Return the temporary script buffer to the pool.
scriptPool.Return(signatureScript)
for j := 0; j < len(msg.TxIn[i].Witness); j++ {
// Copy each item within the witness stack for this
// input into the contiguous buffer at the appropriate
// offset.
witnessElem := msg.TxIn[i].Witness[j]
copy(scripts[offset:], witnessElem)
// Reset the witness item within the stack to the slice
// of the contiguous buffer where the witness lives.
witnessElemSize := uint64(len(witnessElem))
end := offset + witnessElemSize
msg.TxIn[i].Witness[j] = scripts[offset:end:end]
offset += witnessElemSize
// Return the temporary buffer used for the witness stack
// item to the pool.
scriptPool.Return(witnessElem)
}
}
for i := 0; i < len(msg.TxOut); i++ {
// Copy the public key script into the contiguous buffer at the
// appropriate offset.
pkScript := msg.TxOut[i].PkScript
copy(scripts[offset:], pkScript)
// Reset the public key script of the transaction output to the
// slice of the contiguous buffer where the script lives.
scriptSize := uint64(len(pkScript))
end := offset + scriptSize
msg.TxOut[i].PkScript = scripts[offset:end:end]
offset += scriptSize
// Return the temporary script buffer to the pool.
scriptPool.Return(pkScript)
}
return nil
}
// Deserialize decodes a transaction from r into the receiver using a format
// that is suitable for long-term storage such as a database while respecting
// the Version field in the transaction. This function differs from BtcDecode
// in that BtcDecode decodes from the bitcoin wire protocol as it was sent
// across the network. The wire encoding can technically differ depending on
// the protocol version and doesn't even really need to match the format of a
// stored transaction at all. As of the time this comment was written, the
// encoded transaction is the same in both instances, but there is a distinct
// difference and separating the two allows the API to be flexible enough to
// deal with changes.
func (msg *MsgTx) Deserialize(r io.Reader) error {
// At the current time, there is no difference between the wire encoding
// at protocol version 0 and the stable long-term storage format. As
// a result, make use of BtcDecode.
return msg.BtcDecode(r, 0, WitnessEncoding)
}
// DeserializeNoWitness decodes a transaction from r into the receiver, where
// the transaction encoding format within r MUST NOT utilize the new
// serialization format created to encode transaction bearing witness data
// within inputs.
func (msg *MsgTx) DeserializeNoWitness(r io.Reader) error {
return msg.BtcDecode(r, 0, BaseEncoding)
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
// See Serialize for encoding transactions to be stored to disk, such as in a
// database, as opposed to encoding transactions for the wire.
func (msg *MsgTx) BtcEncode(w io.Writer, pver uint32, enc MessageEncoding) error {
err := binarySerializer.PutUint32(w, littleEndian, uint32(msg.Version))
if err != nil {
return err
}
// If the encoding version is set to WitnessEncoding, and the Flags
// field for the MsgTx aren't 0x00, then this indicates the transaction
// is to be encoded using the new witness inclusionary structure
// defined in BIP0144.
doWitness := enc == WitnessEncoding && msg.HasWitness()
if doWitness {
// After the txn's Version field, we include two additional
// bytes specific to the witness encoding. The first byte is an
// always 0x00 marker byte, which allows decoders to
// distinguish a serialized transaction with witnesses from a
// regular (legacy) one. The second byte is the Flag field,
// which at the moment is always 0x01, but may be extended in
// the future to accommodate auxiliary non-committed fields.
if _, err := w.Write(witessMarkerBytes); err != nil {
return err
}
}
count := uint64(len(msg.TxIn))
err = WriteVarInt(w, pver, count)
if err != nil {
return err
}
for _, ti := range msg.TxIn {
err = writeTxIn(w, pver, msg.Version, ti)
if err != nil {
return err
}
}
count = uint64(len(msg.TxOut))
err = WriteVarInt(w, pver, count)
if err != nil {
return err
}
for _, to := range msg.TxOut {
err = WriteTxOut(w, pver, msg.Version, to)
if err != nil {
return err
}
}
// If this transaction is a witness transaction, and the witness
// encoded is desired, then encode the witness for each of the inputs
// within the transaction.
if doWitness {
for _, ti := range msg.TxIn {
err = writeTxWitness(w, pver, msg.Version, ti.Witness)
if err != nil {
return err
}
}
}
return binarySerializer.PutUint32(w, littleEndian, msg.LockTime)
}
// HasWitness returns false if none of the inputs within the transaction
// contain witness data, true false otherwise.
func (msg *MsgTx) HasWitness() bool {
for _, txIn := range msg.TxIn {
if len(txIn.Witness) != 0 {
return true
}
}
return false
}
// Serialize encodes the transaction to w using a format that suitable for
// long-term storage such as a database while respecting the Version field in
// the transaction. This function differs from BtcEncode in that BtcEncode
// encodes the transaction to the bitcoin wire protocol in order to be sent
// across the network. The wire encoding can technically differ depending on
// the protocol version and doesn't even really need to match the format of a
// stored transaction at all. As of the time this comment was written, the
// encoded transaction is the same in both instances, but there is a distinct
// difference and separating the two allows the API to be flexible enough to
// deal with changes.
func (msg *MsgTx) Serialize(w io.Writer) error {
// At the current time, there is no difference between the wire encoding
// at protocol version 0 and the stable long-term storage format. As
// a result, make use of BtcEncode.
//
// Passing a encoding type of WitnessEncoding to BtcEncode for MsgTx
// indicates that the transaction's witnesses (if any) should be
// serialized according to the new serialization structure defined in
// BIP0144.
return msg.BtcEncode(w, 0, WitnessEncoding)
}
// SerializeNoWitness encodes the transaction to w in an identical manner to
// Serialize, however even if the source transaction has inputs with witness
// data, the old serialization format will still be used.
func (msg *MsgTx) SerializeNoWitness(w io.Writer) error {
return msg.BtcEncode(w, 0, BaseEncoding)
}
// baseSize returns the serialized size of the transaction without accounting
// for any witness data.
func (msg *MsgTx) baseSize() int {
// Version 4 bytes + LockTime 4 bytes + Serialized varint size for the
// number of transaction inputs and outputs.
n := 8 + VarIntSerializeSize(uint64(len(msg.TxIn))) +
VarIntSerializeSize(uint64(len(msg.TxOut)))
for _, txIn := range msg.TxIn {
n += txIn.SerializeSize()
}
for _, txOut := range msg.TxOut {
n += txOut.SerializeSize()
}
return n
}
// SerializeSize returns the number of bytes it would take to serialize the
// the transaction.
func (msg *MsgTx) SerializeSize() int {
n := msg.baseSize()
if msg.HasWitness() {
// The marker, and flag fields take up two additional bytes.
n += 2
// Additionally, factor in the serialized size of each of the
// witnesses for each txin.
for _, txin := range msg.TxIn {
n += txin.Witness.SerializeSize()
}
}
return n
}
// SerializeSizeStripped returns the number of bytes it would take to serialize
// the transaction, excluding any included witness data.
func (msg *MsgTx) SerializeSizeStripped() int {
return msg.baseSize()
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgTx) Command() string {
return CmdTx
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgTx) MaxPayloadLength(pver uint32) uint32 {
return MaxBlockPayload
}
// PkScriptLocs returns a slice containing the start of each public key script
// within the raw serialized transaction. The caller can easily obtain the
// length of each script by using len on the script available via the
// appropriate transaction output entry.
func (msg *MsgTx) PkScriptLocs() []int {
numTxOut := len(msg.TxOut)
if numTxOut == 0 {
return nil
}
// The starting offset in the serialized transaction of the first
// transaction output is:
//
// Version 4 bytes + serialized varint size for the number of
// transaction inputs and outputs + serialized size of each transaction
// input.
n := 4 + VarIntSerializeSize(uint64(len(msg.TxIn))) +
VarIntSerializeSize(uint64(numTxOut))
// If this transaction has a witness input, the an additional two bytes
// for the marker, and flag byte need to be taken into account.
if len(msg.TxIn) > 0 && msg.TxIn[0].Witness != nil {
n += 2
}
for _, txIn := range msg.TxIn {
n += txIn.SerializeSize()
}
// Calculate and set the appropriate offset for each public key script.
pkScriptLocs := make([]int, numTxOut)
for i, txOut := range msg.TxOut {
// The offset of the script in the transaction output is:
//
// Value 8 bytes + serialized varint size for the length of
// PkScript.
n += 8 + VarIntSerializeSize(uint64(len(txOut.PkScript)))
pkScriptLocs[i] = n
n += len(txOut.PkScript)
}
return pkScriptLocs
}
// NewMsgTx returns a new bitcoin tx message that conforms to the Message
// interface. The return instance has a default version of TxVersion and there
// are no transaction inputs or outputs. Also, the lock time is set to zero
// to indicate the transaction is valid immediately as opposed to some time in
// future.
func NewMsgTx(version int32) *MsgTx {
return &MsgTx{
Version: version,
TxIn: make([]*TxIn, 0, defaultTxInOutAlloc),
TxOut: make([]*TxOut, 0, defaultTxInOutAlloc),
}
}
// readOutPoint reads the next sequence of bytes from r as an OutPoint.
func readOutPoint(r io.Reader, pver uint32, version int32, op *OutPoint) error {
_, err := io.ReadFull(r, op.Hash[:])
if err != nil {
return err
}
op.Index, err = binarySerializer.Uint32(r, littleEndian)
return err
}
// writeOutPoint encodes op to the bitcoin protocol encoding for an OutPoint
// to w.
func writeOutPoint(w io.Writer, pver uint32, version int32, op *OutPoint) error {
_, err := w.Write(op.Hash[:])
if err != nil {
return err
}
return binarySerializer.PutUint32(w, littleEndian, op.Index)
}
// readScript reads a variable length byte array that represents a transaction
// script. It is encoded as a varInt containing the length of the array
// followed by the bytes themselves. An error is returned if the length is
// greater than the passed maxAllowed parameter which helps protect against
// memory exhaustion attacks and forced panics through malformed messages. The
// fieldName parameter is only used for the error message so it provides more
// context in the error.
func readScript(r io.Reader, pver uint32, maxAllowed uint32, fieldName string) ([]byte, error) {
count, err := ReadVarInt(r, pver)
if err != nil {
return nil, err
}
// Prevent byte array larger than the max message size. It would
// be possible to cause memory exhaustion and panics without a sane
// upper bound on this count.
if count > uint64(maxAllowed) {
str := fmt.Sprintf("%s is larger than the max allowed size "+
"[count %d, max %d]", fieldName, count, maxAllowed)
return nil, messageError("readScript", str)
}
b := scriptPool.Borrow(count)
_, err = io.ReadFull(r, b)
if err != nil {
scriptPool.Return(b)
return nil, err
}
return b, nil
}
// readTxIn reads the next sequence of bytes from r as a transaction input
// (TxIn).
func readTxIn(r io.Reader, pver uint32, version int32, ti *TxIn) error {
err := readOutPoint(r, pver, version, &ti.PreviousOutPoint)
if err != nil {
return err
}
ti.SignatureScript, err = readScript(r, pver, MaxMessagePayload,
"transaction input signature script")
if err != nil {
return err
}
return readElement(r, &ti.Sequence)
}
// writeTxIn encodes ti to the bitcoin protocol encoding for a transaction
// input (TxIn) to w.
func writeTxIn(w io.Writer, pver uint32, version int32, ti *TxIn) error {
err := writeOutPoint(w, pver, version, &ti.PreviousOutPoint)
if err != nil {
return err
}
err = WriteVarBytes(w, pver, ti.SignatureScript)
if err != nil {
return err
}
return binarySerializer.PutUint32(w, littleEndian, ti.Sequence)
}
// readTxOut reads the next sequence of bytes from r as a transaction output
// (TxOut).
func readTxOut(r io.Reader, pver uint32, version int32, to *TxOut) error {
err := readElement(r, &to.Value)
if err != nil {
return err
}
to.PkScript, err = readScript(r, pver, MaxMessagePayload,
"transaction output public key script")
return err
}
// WriteTxOut encodes to into the bitcoin protocol encoding for a transaction
// output (TxOut) to w.
//
// NOTE: This function is exported in order to allow txscript to compute the
// new sighashes for witness transactions (BIP0143).
func WriteTxOut(w io.Writer, pver uint32, version int32, to *TxOut) error {
err := binarySerializer.PutUint64(w, littleEndian, uint64(to.Value))
if err != nil {
return err
}
return WriteVarBytes(w, pver, to.PkScript)
}
// writeTxWitness encodes the bitcoin protocol encoding for a transaction
// input's witness into to w.
func writeTxWitness(w io.Writer, pver uint32, version int32, wit [][]byte) error {
err := WriteVarInt(w, pver, uint64(len(wit)))
if err != nil {
return err
}
for _, item := range wit {
err = WriteVarBytes(w, pver, item)
if err != nil {
return err
}
}
return nil
}