Smartcontract (#39)

* deleted transfer_output added asset type and transaction result to core

* removed writing 0x00 when buffer length is 0

* Refactored emit into VM package + moved tx to own package.

* implemented transaction along with claimTransaction.

* refactored naming of transaction + added decode address for uint160 types

* removed unnecessary folder and files.

* transaction/smartcontract logic

* bumped version 0.24.0

pkg/core/transaction/attribute.go

@@ -0,0 +1,79 @@
+package transaction
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+
+	"github.com/CityOfZion/neo-go/pkg/util"
+)
+
+// Attribute represents a Transaction attribute.
+type Attribute struct {
+	Usage AttrUsage
+	Data  []byte
+}
+
+// DecodeBinary implements the Payloader interface.
+func (attr *Attribute) DecodeBinary(r io.Reader) error {
+	if err := binary.Read(r, binary.LittleEndian, &attr.Usage); err != nil {
+		return err
+	}
+	if attr.Usage == ContractHash ||
+		attr.Usage == Vote ||
+		(attr.Usage >= Hash1 && attr.Usage <= Hash15) {
+		attr.Data = make([]byte, 32)
+		return binary.Read(r, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == ECDH02 || attr.Usage == ECDH03 {
+		attr.Data = make([]byte, 33)
+		attr.Data[0] = byte(attr.Usage)
+		return binary.Read(r, binary.LittleEndian, attr.Data[1:])
+	}
+	if attr.Usage == Script {
+		attr.Data = make([]byte, 20)
+		return binary.Read(r, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == DescriptionUrl {
+		attr.Data = make([]byte, 1)
+		return binary.Read(r, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == Description || attr.Usage >= Remark {
+		lenData := util.ReadVarUint(r)
+		attr.Data = make([]byte, lenData)
+		return binary.Read(r, binary.LittleEndian, attr.Data)
+	}
+	return errors.New("format error in decoding transaction attribute")
+}
+
+// EncodeBinary implements the Payload interface.
+func (attr *Attribute) EncodeBinary(w io.Writer) error {
+	if err := binary.Write(w, binary.LittleEndian, &attr.Usage); err != nil {
+		return err
+	}
+	if attr.Usage == ContractHash ||
+		attr.Usage == Vote ||
+		(attr.Usage >= Hash1 && attr.Usage <= Hash15) {
+		return binary.Write(w, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == ECDH02 || attr.Usage == ECDH03 {
+		attr.Data[0] = byte(attr.Usage)
+		return binary.Write(w, binary.LittleEndian, attr.Data[1:33])
+	}
+	if attr.Usage == Script {
+		return binary.Write(w, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == DescriptionUrl {
+		if err := util.WriteVarUint(w, uint64(len(attr.Data))); err != nil {
+			return err
+		}
+		return binary.Write(w, binary.LittleEndian, attr.Data)
+	}
+	if attr.Usage == Description || attr.Usage >= Remark {
+		if err := util.WriteVarUint(w, uint64(len(attr.Data))); err != nil {
+			return err
+		}
+		return binary.Write(w, binary.LittleEndian, attr.Data)
+	}
+	return errors.New("format error in encoding transaction attribute")
+}