transaction: fix invocation decoding for different versions

Quick fix similar to abc5833853 + uncomment the
test case for it.

Closes #173.

pkg/core/transaction/invocation.go

@@ -14,6 +14,7 @@ type InvocationTX struct {
 
 	// Gas cost of the smart contract.
 	Gas util.Fixed8
+	Version uint8
 }
 
 // NewInvocationTX returns a new invocation transaction.
@@ -35,7 +36,11 @@ func NewInvocationTX(script []byte) *Transaction {
 func (tx *InvocationTX) DecodeBinary(r io.Reader) error {
 	br := util.BinReader{R: r}
 	tx.Script = br.ReadBytes()
-	br.ReadLE(&tx.Gas)
+	if (tx.Version >= 1) {
+		br.ReadLE(&tx.Gas)
+	} else {
+		tx.Gas = util.Fixed8FromInt64(0)
+	}
 	return br.Err
 }
 
@@ -43,6 +48,8 @@ func (tx *InvocationTX) DecodeBinary(r io.Reader) error {
 func (tx *InvocationTX) EncodeBinary(w io.Writer) error {
 	bw := util.BinWriter{W: w}
 	bw.WriteBytes(tx.Script)
-	bw.WriteLE(tx.Gas)
+	if (tx.Version >= 1) {
+		bw.WriteLE(tx.Gas)
+	}
 	return bw.Err
 }

pkg/core/transaction/transaction.go

@@ -136,7 +136,7 @@ func (t *Transaction) DecodeBinary(r io.Reader) error {
 func (t *Transaction) decodeData(r io.Reader) error {
 	switch t.Type {
 	case InvocationType:
-		t.Data = &InvocationTX{}
+		t.Data = &InvocationTX{Version: t.Version}
 		return t.Data.(*InvocationTX).DecodeBinary(r)
 	case MinerType:
 		t.Data = &MinerTX{}

pkg/rpc/server_test.go

@@ -224,12 +224,11 @@ var testRpcCases = []tc{
 		expectedResult: `{"jsonrpc":"2.0","result":true,"id":1}`,
 	},
 
-	/* Good case: TODO: uncomment this test case once https://github.com/CityOfZion/neo-go/issues/173 is fixed!
 	{
 		rpcCall:        `{ "jsonrpc": "2.0", "id": 1, "method": "sendrawtransaction", "params": ["d1001b00046e616d6567d3d8602814a429a91afdbaa3914884a1c90c733101201cc9c05cefffe6cdd7b182816a9152ec218d2ec000000141403387ef7940a5764259621e655b3c621a6aafd869a611ad64adcc364d8dd1edf84e00a7f8b11b630a377eaef02791d1c289d711c08b7ad04ff0d6c9caca22cfe6232103cbb45da6072c14761c9da545749d9cfd863f860c351066d16df480602a2024c6ac"] }`,
 		method:         "sendrawtransaction_2",
 		expectedResult: `{"jsonrpc":"2.0","result":true,"id":1}`,
-	},*/
+	},
 
 	// Bad case, incorrect raw transaction
 	{