// Returns the sha256^2 of serialized Tx
func (t *Tx) Hash() *klib.Hash256 {
return klib.Sha256Sha256(t.Bytes())
}
func (h *Header) Hash() *klib.Hash256 {
p := new(bytes.Buffer)
binary.Write(p, binary.LittleEndian, h)
return klib.Sha256Sha256(p.Bytes())
}
func (t *Tx) HashToSign(subScript []byte, ii int, hashType byte) (*klib.Hash256, error) {
if ii >= len(t.TxIns) {
return nil, errors.New("Tx.StringToSign invalid index")
}
anyoneCanPay := (hashType & SIGHASH_ANYONECANPAY) != 0
htype := hashType & numbers.HashTypeMask
p := new(bytes.Buffer)
// STEP0: version
binary.Write(p, binary.LittleEndian, t.Version)
// STEP1: inputs
if anyoneCanPay {
// If SIGHASH_ANYONECANPAY is set, only current input is written,
// and subScipt is used as SigScript
p.Write(klib.VarUint(1).Bytes()) // inputs count
binary.Write(p, binary.LittleEndian, t.TxIns[ii].PreviousOutput) // PreviousOutput
p.Write(((klib.VarString)(subScript)).Bytes()) // subScript
binary.Write(p, binary.LittleEndian, t.TxIns[ii].Sequence) // Sequence
} else {
// Else write all the inputs with modifications
p.Write(klib.VarUint(len(t.TxIns)).Bytes())
for i, txin := range t.TxIns {
binary.Write(p, binary.LittleEndian, txin.PreviousOutput)
if i == ii { // If this is current input, write subScript
p.Write(((klib.VarString)(subScript)).Bytes())
} else { // Else write an empty VarString
p.Write((klib.VarString{}).Bytes())
}
sequence := txin.Sequence
if i != ii && (htype == SIGHASH_NONE || htype == SIGHASH_SINGLE) {
// If not current input, and of type SIGHASH_NONE || SIGHASH_SINGLE,
// set sequence to 0
sequence = 0
}
binary.Write(p, binary.LittleEndian, sequence)
}
}
// STEP3: outputs
switch htype {
case SIGHASH_NONE:
p.Write((klib.VarString{}).Bytes())
case SIGHASH_SINGLE:
if ii >= len(t.TxOuts) {
// This is actually allowed due to a Satoshi Bug, right thing to do:
// panic("Tx.StringToSign invalid index with type SIGHASH_SINGLE")
return new(klib.Hash256).SetUint64(1), nil
}
p.Write(klib.VarUint(ii + 1).Bytes()) // output count
for i := 0; i < ii; i++ { // All outputs except the last one are written as blank
binary.Write(p, binary.LittleEndian, int64(-1)) // value
p.Write((klib.VarString{}).Bytes()) // script
}
txout := t.TxOuts[ii]
binary.Write(p, binary.LittleEndian, txout.Value)
p.Write(((klib.VarString)(txout.PKScript)).Bytes())
default:
// Another Satoshi Bug: any other hashtype are considered as SIGHASH_ALL
p.Write(klib.VarUint(len(t.TxOuts)).Bytes())
for _, txout := range t.TxOuts {
binary.Write(p, binary.LittleEndian, txout.Value)
p.Write(((klib.VarString)(txout.PKScript)).Bytes())
}
}
// STEP4: LockTime and HashType
binary.Write(p, binary.LittleEndian, t.LockTime)
// Notice hashTypes needs to take 4 bytes
binary.Write(p, binary.LittleEndian, uint32(hashType))
return klib.Sha256Sha256(p.Bytes()), nil
}
// checksum is the first 4 bytes of sha256(payload)
func getChecksumForPayload(payload []byte) uint32 {
hash := klib.Sha256Sha256(payload)
return binary.LittleEndian.Uint32(hash[:4])
}