Simplify txToPairs function signature.

This moves the non-error return values for txToPairs into a new
struct, createdTx, and adds an additional value for the payment
address string.

cmdmgr.go

@@ -360,7 +360,7 @@ func SendFrom(reply chan []byte, msg *btcjson.Message) {
 	pairs := map[string]uint64{
 		toaddr58: uint64(amt),
 	}
-	rawtx, inputs, changeUtxo, err := w.txToPairs(pairs, uint64(fee), int(minconf))
+	createdTx, err := w.txToPairs(pairs, uint64(fee), int(minconf))
 	if err != nil {
 		e := btcjson.ErrInternal
 		e.Message = err.Error()
@@ -372,7 +372,7 @@ func SendFrom(reply chan []byte, msg *btcjson.Message) {
 	n := <-NewJSONID
 	var id interface{} = fmt.Sprintf("btcwallet(%v)", n)
 	m, err := btcjson.CreateMessageWithId("sendrawtransaction", id,
-		hex.EncodeToString(rawtx))
+		hex.EncodeToString(createdTx.rawTx))
 	if err != nil {
 		e := btcjson.ErrInternal
 		e.Message = err.Error()
@@ -394,12 +394,12 @@ func SendFrom(reply chan []byte, msg *btcjson.Message) {
 
 		// Remove previous unspent outputs now spent by the tx.
 		w.UtxoStore.Lock()
-		modified := w.UtxoStore.s.Remove(inputs)
+		modified := w.UtxoStore.s.Remove(createdTx.inputs)
 
 		// Add unconfirmed change utxo (if any) to UtxoStore.
-		if changeUtxo != nil {
+		if createdTx.changeUtxo != nil {
-			w.UtxoStore.s = append(w.UtxoStore.s, changeUtxo)
+			w.UtxoStore.s = append(w.UtxoStore.s, createdTx.changeUtxo)
-			w.ReqSpentUtxoNtfn(changeUtxo)
+			w.ReqSpentUtxoNtfn(createdTx.changeUtxo)
 			modified = true
 		}
 
@@ -515,7 +515,7 @@ func SendMany(reply chan []byte, msg *btcjson.Message) {
 	TxFee.Lock()
 	fee := TxFee.i
 	TxFee.Unlock()
-	rawtx, inputs, changeUtxo, err := w.txToPairs(pairs, uint64(fee), int(minconf))
+	createdTx, err := w.txToPairs(pairs, uint64(fee), int(minconf))
 	if err != nil {
 		e := btcjson.ErrInternal
 		e.Message = err.Error()
@@ -527,7 +527,7 @@ func SendMany(reply chan []byte, msg *btcjson.Message) {
 	n := <-NewJSONID
 	var id interface{} = fmt.Sprintf("btcwallet(%v)", n)
 	m, err := btcjson.CreateMessageWithId("sendrawtransaction", id,
-		hex.EncodeToString(rawtx))
+		hex.EncodeToString(createdTx.rawTx))
 	if err != nil {
 		e := btcjson.ErrInternal
 		e.Message = err.Error()
@@ -549,12 +549,12 @@ func SendMany(reply chan []byte, msg *btcjson.Message) {
 
 		// Remove previous unspent outputs now spent by the tx.
 		w.UtxoStore.Lock()
-		modified := w.UtxoStore.s.Remove(inputs)
+		modified := w.UtxoStore.s.Remove(createdTx.inputs)
 
 		// Add unconfirmed change utxo (if any) to UtxoStore.
-		if changeUtxo != nil {
+		if createdTx.changeUtxo != nil {
-			w.UtxoStore.s = append(w.UtxoStore.s, changeUtxo)
+			w.UtxoStore.s = append(w.UtxoStore.s, createdTx.changeUtxo)
-			w.ReqSpentUtxoNtfn(changeUtxo)
+			w.ReqSpentUtxoNtfn(createdTx.changeUtxo)
 			modified = true
 		}
 
@@ -577,7 +577,7 @@ func SendMany(reply chan []byte, msg *btcjson.Message) {
 		// Add hex string of raw tx to sent tx pool.  If future blocks
 		// do not contain a tx, a resend is attempted.
 		UnminedTxs.Lock()
-		UnminedTxs.m[result.(string)] = hex.EncodeToString(rawtx)
+		UnminedTxs.m[result.(string)] = hex.EncodeToString(createdTx.rawTx)
 		UnminedTxs.Unlock()
 
 		ReplySuccess(reply, msg.Id, result)

createtx.go

@@ -108,6 +108,16 @@ func selectInputs(s tx.UtxoStore, amt uint64, minconf int) (inputs []*tx.Utxo, b
 	return inputs, btcout, nil
 }
 
+// createdTx is a type holding information regarding a newly-created
+// transaction, including the raw bytes, inputs, and a address and UTXO
+// for change.
+type createdTx struct {
+	rawTx      []byte
+	inputs     []*tx.Utxo
+	changeAddr string
+	changeUtxo *tx.Utxo
+}
+
 // txToPairs creates a raw transaction sending the amounts for each
 // address/amount pair and fee to each address and the miner.  minconf
 // specifies the minimum number of confirmations required before an
@@ -117,7 +127,7 @@ func selectInputs(s tx.UtxoStore, amt uint64, minconf int) (inputs []*tx.Utxo, b
 // address, changeUtxo will point to a unconfirmed (height = -1, zeroed
 // block hash) Utxo.  ErrInsufficientFunds is returned if there are not
 // enough eligible unspent outputs to create the transaction.
-func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int) (rawtx []byte, inputs []*tx.Utxo, changeUtxo *tx.Utxo, err error) {
+func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int) (*createdTx, error) {
 	// Recorded unspent transactions should not be modified until this
 	// finishes.
 	w.UtxoStore.RLock()
@@ -135,20 +145,20 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 	// Select unspent outputs to be used in transaction.
 	inputs, btcout, err := selectInputs(w.UtxoStore.s, amt+fee, minconf)
 	if err != nil {
-		return nil, nil, nil, err
+		return nil, err
 	}
 
 	// Add outputs to new tx.
 	for addr, amt := range pairs {
 		addr160, _, err := btcutil.DecodeAddress(addr)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot decode address: %s", err)
+			return nil, fmt.Errorf("cannot decode address: %s", err)
 		}
 
 		// Spend amt to addr160
 		pkScript, err := btcscript.PayToPubKeyHashScript(addr160)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot create txout script: %s", err)
+			return nil, fmt.Errorf("cannot create txout script: %s", err)
 		}
 		txout := btcwire.NewTxOut(int64(amt), pkScript)
 		msgtx.AddTxOut(txout)
@@ -156,23 +166,26 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 
 	// Check if there are leftover unspent outputs, and return coins back to
 	// a new address we own.
+	var changeUtxo *tx.Utxo
+	var changeAddr string
 	if btcout > amt+fee {
 		// Create a new address to spend leftover outputs to.
 		// TODO(jrick): use the next chained address, not the next unused.
-		newaddr, err := w.NextUnusedAddress()
+		var err error
+		changeAddr, err = w.NextUnusedAddress()
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("failed to get next unused address: %s", err)
+			return nil, fmt.Errorf("failed to get next unused address: %s", err)
 		}
 
 		// Spend change
 		change := btcout - (amt + fee)
-		newaddr160, _, err := btcutil.DecodeAddress(newaddr)
+		changeAddrHash, _, err := btcutil.DecodeAddress(changeAddr)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot decode new address: %s", err)
+			return nil, fmt.Errorf("cannot decode new address: %s", err)
 		}
-		pkScript, err := btcscript.PayToPubKeyHashScript(newaddr160)
+		pkScript, err := btcscript.PayToPubKeyHashScript(changeAddrHash)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot create txout script: %s", err)
+			return nil, fmt.Errorf("cannot create txout script: %s", err)
 		}
 		msgtx.AddTxOut(btcwire.NewTxOut(int64(change), pkScript))
 
@@ -187,7 +200,7 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 			Height:    -1,
 			Subscript: pkScript,
 		}
-		copy(changeUtxo.AddrHash[:], newaddr160)
+		copy(changeUtxo.AddrHash[:], changeAddrHash)
 	}
 
 	// Selected unspent outputs become new transaction's inputs.
@@ -197,11 +210,11 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 	for i, ip := range inputs {
 		addrstr, err := btcutil.EncodeAddress(ip.AddrHash[:], w.Wallet.Net())
 		if err != nil {
-			return nil, nil, nil, err
+			return nil, err
 		}
 		privkey, err := w.GetAddressKey(addrstr)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot get address key: %v", err)
+			return nil, fmt.Errorf("cannot get address key: %v", err)
 		}
 
 		// TODO(jrick): we want compressed pubkeys.  Switch wallet to
@@ -210,7 +223,7 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 		sigscript, err := btcscript.SignatureScript(msgtx, i,
 			ip.Subscript, btcscript.SigHashAll, privkey, false)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot create sigscript: %s", err)
+			return nil, fmt.Errorf("cannot create sigscript: %s", err)
 		}
 		msgtx.TxIn[i].SignatureScript = sigscript
 	}
@@ -225,10 +238,10 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 		engine, err := btcscript.NewScript(txin.SignatureScript, inputs[i].Subscript, i,
 			msgtx, flags)
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot create script engine: %s", err)
+			return nil, fmt.Errorf("cannot create script engine: %s", err)
 		}
 		if err = engine.Execute(); err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot validate transaction: %s", err)
+			return nil, fmt.Errorf("cannot validate transaction: %s", err)
 		}
 	}
 
@@ -236,12 +249,12 @@ func (w *BtcWallet) txToPairs(pairs map[string]uint64, fee uint64, minconf int)
 	if changeUtxo != nil {
 		txHash, err := msgtx.TxSha()
 		if err != nil {
-			return nil, nil, nil, fmt.Errorf("cannot create transaction hash: %s", err)
+			return nil, fmt.Errorf("cannot create transaction hash: %s", err)
 		}
 		copy(changeUtxo.Out.Hash[:], txHash[:])
 	}
 
 	buf := new(bytes.Buffer)
 	msgtx.BtcEncode(buf, btcwire.ProtocolVersion)
-	return buf.Bytes(), inputs, changeUtxo, nil
+	return &createdTx{buf.Bytes(), inputs, changeAddr, changeUtxo}, nil
 }

createtx_test.go

@@ -64,7 +64,7 @@ func TestFakeTxs(t *testing.T) {
 	pairs := map[string]uint64{
 		"17XhEvq9Nahdj7Xe1nv6oRe1tEmaHUuynH": 5000,
 	}
-	rawtx, _, _, err := btcw.txToPairs(pairs, 100, 0)
+	createdTx, err := btcw.txToPairs(pairs, 100, 0)
 	if err != nil {
 		t.Errorf("Tx creation failed: %s", err)
 		return
@@ -75,7 +75,7 @@ func TestFakeTxs(t *testing.T) {
 		Id:      "test",
 		Method:  "sendrawtransaction",
 		Params: []interface{}{
-			hex.EncodeToString(rawtx),
+			hex.EncodeToString(createdTx.rawTx),
 		},
 	}
 	m, _ := json.Marshal(msg)