// prepare a signed transaction
func make_signed_tx() {
// Make an empty transaction
tx := new(btc.Tx)
tx.Version = 1
tx.Lock_time = 0
// Select as many inputs as we need to pay the full amount (with the fee)
var btcsofar uint64
for inpcnt := 0; inpcnt < len(unspentOuts); inpcnt++ {
uo := UO(unspentOuts[inpcnt])
// add the input to our transaction:
tin := new(btc.TxIn)
tin.Input = *unspentOuts[inpcnt]
tin.Sequence = 0xffffffff
tx.TxIn = append(tx.TxIn, tin)
btcsofar += uo.Value
if !*useallinputs && (btcsofar >= spendBtc+feeBtc) {
break
}
}
changeBtc = btcsofar - (spendBtc + feeBtc)
if *verbose {
fmt.Printf("Spending %d out of %d outputs...\n", len(tx.TxIn), len(unspentOuts))
}
// Build transaction outputs:
tx.TxOut = make([]*btc.TxOut, len(sendTo))
for o := range sendTo {
tx.TxOut[o] = &btc.TxOut{Value: sendTo[o].amount, Pk_script: sendTo[o].addr.OutScript()}
}
if changeBtc > 0 {
// Add one more output (with the change)
chad := get_change_addr()
if *verbose {
fmt.Println("Sending change", changeBtc, "to", chad.String())
}
tx.TxOut = append(tx.TxOut, &btc.TxOut{Value: changeBtc, Pk_script: chad.OutScript()})
}
if *hashes {
dump_hashes_to_sign(tx)
} else {
sign_tx(tx)
write_tx_file(tx)
if *apply2bal {
apply_to_balance(tx)
}
}
}
func GetTx(txid *btc.Uint256, vout int) bool {
r, er := http.Get("http://blockexplorer.com/rawtx/" + txid.String())
if er == nil && r.StatusCode == 200 {
defer r.Body.Close()
c, _ := ioutil.ReadAll(r.Body)
var txx onetx
er = json.Unmarshal(c[:], &txx)
if er == nil {
tx := new(btc.Tx)
tx.Version = txx.Ver
tx.TxIn = make([]*btc.TxIn, len(txx.In))
for i := range txx.In {
tx.TxIn[i] = new(btc.TxIn)
tx.TxIn[i].Input.Hash = btc.NewUint256FromString(txx.In[i].Prev_out.Hash).Hash
tx.TxIn[i].Input.Vout = txx.In[i].Prev_out.N
tx.TxIn[i].ScriptSig, _ = btc.DecodeScript(txx.In[i].ScriptSig)
tx.TxIn[i].Sequence = 0xffffffff
}
tx.TxOut = make([]*btc.TxOut, len(txx.Out))
for i := range txx.Out {
tx.TxOut[i] = new(btc.TxOut)
tx.TxOut[i].Value = btc.ParseValue(txx.Out[i].Value)
tx.TxOut[i].Pk_script, _ = btc.DecodeScript(txx.Out[i].ScriptPubKey)
}
tx.Lock_time = txx.Lock_time
rawtx := tx.Serialize()
curid := btc.NewSha2Hash(rawtx)
if !curid.Equal(txid) {
fmt.Println("The downloaded transaction does not match its ID.")
return false
}
ioutil.WriteFile("balance/"+curid.String()+".tx", rawtx, 0666)
return true
} else {
fmt.Println("json.Unmarshal:", er.Error())
}
} else {
if er != nil {
fmt.Println("http.Get:", er.Error())
} else {
fmt.Println("StatusCode=", r.StatusCode)
}
}
return false
}
// Download (and re-assemble) raw transaction from blockexplorer.com
func GetTxFromExplorer(txid *btc.Uint256) ([]byte, []byte) {
url := "http://blockexplorer.com/rawtx/" + txid.String()
r, er := http.Get(url)
if er == nil && r.StatusCode == 200 {
defer r.Body.Close()
c, _ := ioutil.ReadAll(r.Body)
var txx onetx
er = json.Unmarshal(c[:], &txx)
if er == nil {
// This part looks weird, but this is how I solved seq=FFFFFFFF, if the field not present:
for i := range txx.In {
txx.In[i].Sequence = 0xffffffff
}
json.Unmarshal(c[:], &txx)
// ... end of the weird solution
tx := new(btc.Tx)
tx.Version = txx.Ver
tx.TxIn = make([]*btc.TxIn, len(txx.In))
for i := range txx.In {
tx.TxIn[i] = new(btc.TxIn)
tx.TxIn[i].Input.Hash = btc.NewUint256FromString(txx.In[i].Prev_out.Hash).Hash
tx.TxIn[i].Input.Vout = txx.In[i].Prev_out.N
if txx.In[i].Prev_out.N == 0xffffffff &&
txx.In[i].Prev_out.Hash == "0000000000000000000000000000000000000000000000000000000000000000" {
tx.TxIn[i].ScriptSig, _ = hex.DecodeString(txx.In[i].Coinbase)
} else {
tx.TxIn[i].ScriptSig, _ = btc.DecodeScript(txx.In[i].ScriptSig)
}
tx.TxIn[i].Sequence = txx.In[i].Sequence
}
tx.TxOut = make([]*btc.TxOut, len(txx.Out))
for i := range txx.Out {
am, er := btc.StringToSatoshis(txx.Out[i].Value)
if er != nil {
fmt.Println("Incorrect BTC amount", txx.Out[i].Value, er.Error())
return nil, nil
}
tx.TxOut[i] = new(btc.TxOut)
tx.TxOut[i].Value = am
tx.TxOut[i].Pk_script, _ = btc.DecodeScript(txx.Out[i].ScriptPubKey)
}
tx.Lock_time = txx.Lock_time
rawtx := tx.Serialize()
if txx.Size != uint(len(rawtx)) {
fmt.Printf("Transaction size mismatch: %d expexted, %d decoded\n", txx.Size, len(rawtx))
return nil, rawtx
}
curid := btc.NewSha2Hash(rawtx)
if !curid.Equal(txid) {
fmt.Println("The downloaded transaction does not match its ID.", txid.String())
return nil, rawtx
}
return rawtx, rawtx
} else {
fmt.Println("json.Unmarshal:", er.Error())
}
} else {
if er != nil {
fmt.Println("http.Get:", er.Error())
} else {
fmt.Println("StatusCode=", r.StatusCode)
}
}
return nil, nil
}
// prepare a signed transaction
func make_signed_tx() {
// Make an empty transaction
tx := new(btc.Tx)
tx.Version = 1
tx.Lock_time = 0
// Select as many inputs as we need to pay the full amount (with the fee)
var btcsofar uint64
var inpcnt uint
for inpcnt = 0; inpcnt < uint(len(unspentOuts)); inpcnt++ {
uo := UO(unspentOuts[inpcnt])
// add the input to our transaction:
tin := new(btc.TxIn)
tin.Input = *unspentOuts[inpcnt]
tin.Sequence = 0xffffffff
tx.TxIn = append(tx.TxIn, tin)
btcsofar += uo.Value
if btcsofar >= spendBtc+feeBtc {
break
}
}
changeBtc = btcsofar - (spendBtc + feeBtc)
fmt.Printf("Spending %d out of %d outputs...\n", inpcnt+1, len(unspentOuts))
// Build transaction outputs:
tx.TxOut = make([]*btc.TxOut, len(sendTo))
for o := range sendTo {
tx.TxOut[o] = &btc.TxOut{Value: sendTo[o].amount, Pk_script: sendTo[o].addr.OutScript()}
}
if changeBtc > 0 {
// Add one more output (with the change)
tx.TxOut = append(tx.TxOut, &btc.TxOut{Value: changeBtc, Pk_script: get_change_addr().OutScript()})
}
//fmt.Println("Unsigned:", hex.EncodeToString(tx.Serialize()))
for in := range tx.TxIn {
uo := UO(unspentOuts[in])
var found bool
for j := range publ_addrs {
if publ_addrs[j].Owns(uo.Pk_script) {
pub_key, e := btc.NewPublicKey(publ_addrs[j].Pubkey)
if e != nil {
println("NewPublicKey:", e.Error(), "\007")
os.Exit(1)
}
// Load the key (private and public)
var key ecdsa.PrivateKey
key.D = new(big.Int).SetBytes(priv_keys[j][:])
key.PublicKey = pub_key.PublicKey
//Calculate proper transaction hash
h := tx.SignatureHash(uo.Pk_script, in, btc.SIGHASH_ALL)
//fmt.Println("SignatureHash:", btc.NewUint256(h).String())
// Sign
r, s, err := ecdsa.Sign(rand.Reader, &key, h)
if err != nil {
println("Sign:", err.Error(), "\007")
os.Exit(1)
}
rb := r.Bytes()
sb := s.Bytes()
if rb[0] >= 0x80 { // I thinnk this is needed, thought I am not quite sure... :P
rb = append([]byte{0x00}, rb...)
}
if sb[0] >= 0x80 { // I thinnk this is needed, thought I am not quite sure... :P
sb = append([]byte{0x00}, sb...)
}
// Output the signing result into a buffer, in format expected by bitcoin protocol
busig := new(bytes.Buffer)
busig.WriteByte(0x30)
busig.WriteByte(byte(4 + len(rb) + len(sb)))
busig.WriteByte(0x02)
busig.WriteByte(byte(len(rb)))
busig.Write(rb)
busig.WriteByte(0x02)
busig.WriteByte(byte(len(sb)))
busig.Write(sb)
busig.WriteByte(0x01) // hash type
// Output the signature and the public key into tx.ScriptSig
buscr := new(bytes.Buffer)
buscr.WriteByte(byte(busig.Len()))
buscr.Write(busig.Bytes())
buscr.WriteByte(byte(len(publ_addrs[j].Pubkey)))
buscr.Write(publ_addrs[j].Pubkey)
// assign:
tx.TxIn[in].ScriptSig = buscr.Bytes()
found = true
break
}
}
if !found {
fmt.Println("You do not have private key for input number", hex.EncodeToString(uo.Pk_script), "\007")
os.Exit(1)
}
}
rawtx := tx.Serialize()
tx.Hash = btc.NewSha2Hash(rawtx)
hs := tx.Hash.String()
fmt.Println(hs)
f, _ := os.Create(hs[:8] + ".txt")
if f != nil {
f.Write([]byte(hex.EncodeToString(rawtx)))
f.Close()
fmt.Println("Transaction data stored in", hs[:8]+".txt")
}
f, _ = os.Create("balance/unspent.txt")
if f != nil {
for j := uint(0); j < uint(len(unspentOuts)); j++ {
if j > inpcnt {
fmt.Fprintln(f, unspentOuts[j], unspentOutsLabel[j])
}
}
fmt.Println(inpcnt, "spent output(s) removed from 'balance/unspent.txt'")
var addback int
for out := range tx.TxOut {
for j := range publ_addrs {
if publ_addrs[j].Owns(tx.TxOut[out].Pk_script) {
fmt.Fprintf(f, "%s-%03d # %.8f / %s\n", tx.Hash.String(), out,
float64(tx.TxOut[out].Value)/1e8, publ_addrs[j].String())
addback++
}
}
}
f.Close()
if addback > 0 {
f, _ = os.Create("balance/" + hs + ".tx")
if f != nil {
f.Write(rawtx)
f.Close()
}
fmt.Println(addback, "new output(s) appended to 'balance/unspent.txt'")
}
}
}
// prepare a signed transaction
func make_signed_tx() {
// Make an empty transaction
tx := new(btc.Tx)
tx.Version = 1
tx.Lock_time = 0
// Select as many inputs as we need to pay the full amount (with the fee)
var btcsofar uint64
for inpcnt := 0; inpcnt < len(unspentOuts); inpcnt++ {
uo := UO(unspentOuts[inpcnt])
// add the input to our transaction:
tin := new(btc.TxIn)
tin.Input = *unspentOuts[inpcnt]
tin.Sequence = 0xffffffff
tx.TxIn = append(tx.TxIn, tin)
btcsofar += uo.Value
if !*useallinputs && (btcsofar >= spendBtc+feeBtc) {
break
}
}
changeBtc = btcsofar - (spendBtc + feeBtc)
if *verbose {
fmt.Printf("Spending %d out of %d outputs...\n", len(tx.TxIn), len(unspentOuts))
}
// Build transaction outputs:
for o := range sendTo {
if sendTo[o].addr.StealthAddr != nil {
tx.TxOut = append(tx.TxOut, stealth_txout(sendTo[o].addr.StealthAddr, sendTo[o].amount)...)
} else {
tx.TxOut = append(tx.TxOut, &btc.TxOut{Value: sendTo[o].amount,
Pk_script: sendTo[o].addr.OutScript()})
}
}
if changeBtc > 0 {
// Add one more output (with the change)
chad := get_change_addr()
if *verbose {
fmt.Println("Sending change", changeBtc, "to", chad.String())
}
tx.TxOut = append(tx.TxOut, &btc.TxOut{Value: changeBtc, Pk_script: chad.OutScript()})
}
if *message != "" {
// Add NULL output with an arbitrary message
scr := new(bytes.Buffer)
scr.WriteByte(0x6a) // OP_RETURN
btc.WritePutLen(scr, uint32(len(*message)))
scr.Write([]byte(*message))
tx.TxOut = append(tx.TxOut, &btc.TxOut{Value: 0, Pk_script: scr.Bytes()})
}
if *hashes {
dump_hashes_to_sign(tx)
} else {
sign_tx(tx)
write_tx_file(tx)
if *apply2bal {
apply_to_balance(tx)
}
}
}
func dl_payment(w http.ResponseWriter, r *http.Request) {
if !ipchecker(r) {
return
}
var err string
r.ParseForm()
if len(r.Form["outcnt"]) == 1 {
var thisbal btc.AllUnspentTx
var pay_cmd string
var totalinput, spentsofar uint64
var change_addr *btc.BtcAddr
tx := new(btc.Tx)
tx.Version = 1
tx.Lock_time = 0
outcnt, _ := strconv.ParseUint(r.Form["outcnt"][0], 10, 32)
wallet.LockBal()
for i := 1; i <= int(outcnt); i++ {
is := fmt.Sprint(i)
if len(r.Form["txout"+is]) == 1 && r.Form["txout"+is][0] == "on" {
hash := btc.NewUint256FromString(r.Form["txid"+is][0])
if hash != nil {
vout, er := strconv.ParseUint(r.Form["txvout"+is][0], 10, 32)
if er == nil {
var po = btc.TxPrevOut{Hash: hash.Hash, Vout: uint32(vout)}
for j := range wallet.MyBalance {
if wallet.MyBalance[j].TxPrevOut == po {
thisbal = append(thisbal, wallet.MyBalance[j])
// Add the input to our tx
tin := new(btc.TxIn)
tin.Input = wallet.MyBalance[j].TxPrevOut
tin.Sequence = 0xffffffff
tx.TxIn = append(tx.TxIn, tin)
totalinput += wallet.MyBalance[j].Value
if change_addr == nil {
change_addr = wallet.MyBalance[j].BtcAddr
}
}
}
}
}
}
}
wallet.UnlockBal()
for i := 1; ; i++ {
adridx := fmt.Sprint("adr", i)
btcidx := fmt.Sprint("btc", i)
if len(r.Form[adridx]) != 1 || len(r.Form[btcidx]) != 1 {
break
}
if len(r.Form[adridx][0]) > 1 {
addr, er := btc.NewAddrFromString(r.Form[adridx][0])
if er == nil {
am, er := btc.StringToSatoshis(r.Form[btcidx][0])
if er == nil && am > 0 {
if pay_cmd == "" {
pay_cmd = "wallet -useallinputs -send "
} else {
pay_cmd += ","
}
pay_cmd += addr.Enc58str + "=" + btc.UintToBtc(am)
tout := new(btc.TxOut)
tout.Value = am
tout.Pk_script = addr.OutScript()
tx.TxOut = append(tx.TxOut, tout)
spentsofar += am
} else {
err = "Incorrect amount (" + r.Form[btcidx][0] + ") for Output #" + fmt.Sprint(i)
goto error
}
} else {
err = "Incorrect address (" + r.Form[adridx][0] + ") for Output #" + fmt.Sprint(i)
goto error
}
}
}
if pay_cmd == "" {
err = "No inputs selected"
goto error
}
am, er := btc.StringToSatoshis(r.Form["txfee"][0])
if er != nil {
err = "Incorrect fee value: " + r.Form["txfee"][0]
goto error
}
pay_cmd += " -fee " + r.Form["txfee"][0]
spentsofar += am
if len(r.Form["change"][0]) > 1 {
addr, er := btc.NewAddrFromString(r.Form["change"][0])
if er != nil {
err = "Incorrect change address: " + r.Form["change"][0]
goto error
}
change_addr = addr
}
pay_cmd += " -change " + change_addr.String()
if totalinput > spentsofar {
// Add change output
tout := new(btc.TxOut)
tout.Value = totalinput - spentsofar
tout.Pk_script = change_addr.OutScript()
tx.TxOut = append(tx.TxOut, tout)
}
buf := new(bytes.Buffer)
zi := zip.NewWriter(buf)
was_tx := make(map[[32]byte]bool, len(thisbal))
for i := range thisbal {
if was_tx[thisbal[i].TxPrevOut.Hash] {
continue
}
was_tx[thisbal[i].TxPrevOut.Hash] = true
txid := btc.NewUint256(thisbal[i].TxPrevOut.Hash[:])
fz, _ := zi.Create("balance/" + txid.String() + ".tx")
wallet.GetRawTransaction(thisbal[i].MinedAt, txid, fz)
}
fz, _ := zi.Create("balance/unspent.txt")
for i := range thisbal {
fmt.Fprintf(fz, "%s # %.8f BTC @ %s, %d confs\n", thisbal[i].TxPrevOut.String(),
float64(thisbal[i].Value)/1e8, thisbal[i].BtcAddr.StringLab(),
1+common.Last.Block.Height-thisbal[i].MinedAt)
}
// pay_cmd.bat
if pay_cmd != "" {
fz, _ = zi.Create(common.CFG.PayCommandName)
fz.Write([]byte(pay_cmd))
}
// Raw transaction
fz, _ = zi.Create("tx2sign.txt")
fz.Write([]byte(hex.EncodeToString(tx.Serialize())))
zi.Close()
w.Header()["Content-Type"] = []string{"application/zip"}
w.Write(buf.Bytes())
return
} else {
err = "Bad request"
}
error:
s := load_template("send_error.html")
write_html_head(w, r)
s = strings.Replace(s, "<!--ERROR_MSG-->", err, 1)
w.Write([]byte(s))
write_html_tail(w)
}
func dl_payment(w http.ResponseWriter, r *http.Request) {
if !ipchecker(r) {
return
}
var err string
if len(r.Form["outcnt"]) == 1 {
var thisbal btc.AllUnspentTx
var pay_cmd string
var totalinput, spentsofar uint64
var change_addr *btc.BtcAddr
var multisig_input []*wallet.MultisigAddr
var invalid_tx bool
addrs_to_msign := make(map[string]bool)
tx := new(btc.Tx)
tx.Version = 1
tx.Lock_time = 0
outcnt, _ := strconv.ParseUint(r.Form["outcnt"][0], 10, 32)
wallet.LockBal()
for i := 1; i <= int(outcnt); i++ {
is := fmt.Sprint(i)
if len(r.Form["txout"+is]) == 1 && r.Form["txout"+is][0] == "on" {
hash := btc.NewUint256FromString(r.Form["txid"+is][0])
if hash != nil {
vout, er := strconv.ParseUint(r.Form["txvout"+is][0], 10, 32)
if er == nil {
var po = btc.TxPrevOut{Hash: hash.Hash, Vout: uint32(vout)}
for j := range wallet.MyBalance {
if wallet.MyBalance[j].TxPrevOut == po {
thisbal = append(thisbal, wallet.MyBalance[j])
// Add the input to our tx
tin := new(btc.TxIn)
tin.Input = wallet.MyBalance[j].TxPrevOut
tin.Sequence = 0xffffffff
tx.TxIn = append(tx.TxIn, tin)
// Add new multisig address description
_, msi := wallet.IsMultisig(wallet.MyBalance[j].BtcAddr)
multisig_input = append(multisig_input, msi)
if msi != nil {
for ai := range msi.ListOfAddres {
addrs_to_msign[msi.ListOfAddres[ai]] = true
}
}
// Add the value to total input value
totalinput += wallet.MyBalance[j].Value
// If no change specified, use the first input addr as it
if change_addr == nil {
change_addr = wallet.MyBalance[j].BtcAddr
}
}
}
}
}
}
}
wallet.UnlockBal()
for i := 1; ; i++ {
adridx := fmt.Sprint("adr", i)
btcidx := fmt.Sprint("btc", i)
if len(r.Form[adridx]) != 1 || len(r.Form[btcidx]) != 1 {
break
}
if len(r.Form[adridx][0]) > 1 {
addr, er := btc.NewAddrFromString(r.Form[adridx][0])
if er == nil {
am, er := btc.StringToSatoshis(r.Form[btcidx][0])
if er == nil && am > 0 {
if pay_cmd == "" {
pay_cmd = "wallet -useallinputs -send "
} else {
pay_cmd += ","
}
pay_cmd += addr.Enc58str + "=" + btc.UintToBtc(am)
tout := new(btc.TxOut)
tout.Value = am
tout.Pk_script = addr.OutScript()
if tout.Pk_script != nil {
tx.TxOut = append(tx.TxOut, tout)
} else {
invalid_tx = true
}
spentsofar += am
} else {
err = "Incorrect amount (" + r.Form[btcidx][0] + ") for Output #" + fmt.Sprint(i)
goto error
}
} else {
err = "Incorrect address (" + r.Form[adridx][0] + ") for Output #" + fmt.Sprint(i)
goto error
}
}
}
if pay_cmd == "" {
err = "No inputs selected"
goto error
}
am, er := btc.StringToSatoshis(r.Form["txfee"][0])
if er != nil {
err = "Incorrect fee value: " + r.Form["txfee"][0]
goto error
}
pay_cmd += " -fee " + r.Form["txfee"][0]
spentsofar += am
if len(r.Form["change"][0]) > 1 {
addr, er := btc.NewAddrFromString(r.Form["change"][0])
if er != nil {
err = "Incorrect change address: " + r.Form["change"][0]
goto error
}
change_addr = addr
}
pay_cmd += " -change " + change_addr.String()
if totalinput > spentsofar {
// Add change output
tout := new(btc.TxOut)
tout.Value = totalinput - spentsofar
tout.Pk_script = change_addr.OutScript()
tx.TxOut = append(tx.TxOut, tout)
}
buf := new(bytes.Buffer)
zi := zip.NewWriter(buf)
was_tx := make(map[[32]byte]bool, len(thisbal))
for i := range thisbal {
if was_tx[thisbal[i].TxPrevOut.Hash] {
continue
}
was_tx[thisbal[i].TxPrevOut.Hash] = true
txid := btc.NewUint256(thisbal[i].TxPrevOut.Hash[:])
fz, _ := zi.Create("balance/" + txid.String() + ".tx")
wallet.GetRawTransaction(thisbal[i].MinedAt, txid, fz)
}
fz, _ := zi.Create("balance/unspent.txt")
for i := range thisbal {
fmt.Fprintf(fz, "%s # %.8f BTC @ %s, %d confs\n", thisbal[i].TxPrevOut.String(),
float64(thisbal[i].Value)/1e8, thisbal[i].BtcAddr.StringLab(),
1+common.Last.Block.Height-thisbal[i].MinedAt)
}
if len(addrs_to_msign) > 0 {
// Multisig (or mixed) transaction ...
for i := range multisig_input {
if multisig_input[i] == nil {
continue
}
d, er := hex.DecodeString(multisig_input[i].RedeemScript)
if er != nil {
println("ERROR parsing hex RedeemScript:", er.Error())
continue
}
ms, er := btc.NewMultiSigFromP2SH(d)
if er != nil {
println("ERROR parsing bin RedeemScript:", er.Error())
continue
}
tx.TxIn[i].ScriptSig = ms.Bytes()
}
fz, _ = zi.Create("multi2sign.txt")
fz.Write([]byte(hex.EncodeToString(tx.Serialize())))
fz, _ = zi.Create("multi_" + common.CFG.PayCommandName)
for k, _ := range addrs_to_msign {
fmt.Fprintln(fz, "wallet -msign", k, "-raw ...")
}
} else {
// Non-multisig transaction ...
if !invalid_tx {
fz, _ = zi.Create("tx2sign.txt")
fz.Write([]byte(hex.EncodeToString(tx.Serialize())))
}
if pay_cmd != "" {
fz, _ = zi.Create(common.CFG.PayCommandName)
fz.Write([]byte(pay_cmd))
}
}
zi.Close()
w.Header()["Content-Type"] = []string{"application/zip"}
w.Write(buf.Bytes())
return
} else {
err = "Bad request"
}
error:
s := load_template("send_error.html")
write_html_head(w, r)
s = strings.Replace(s, "<!--ERROR_MSG-->", err, 1)
w.Write([]byte(s))
write_html_tail(w)
}