[#822] moprh/event: Add parsers from Op struct

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/morph/event/opcodes.go

@@ -1,6 +1,11 @@
 package event
 
-import "github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+import (
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+)
 
 // Op is wrapper over Neo VM's opcode
 // and its parameter.
@@ -19,3 +24,27 @@ func (o Op) Code() opcode.Opcode {
 func (o Op) Param() []byte {
 	return o.param
 }
+
+// BytesFromOpcode tries to retrieve bytes from Op.
+func BytesFromOpcode(op Op) ([]byte, error) {
+	switch code := op.Code(); code {
+	case opcode.PUSHDATA1, opcode.PUSHDATA2, opcode.PUSHDATA4:
+		return op.Param(), nil
+	default:
+		return nil, fmt.Errorf("unexpected ByteArray opcode %s", code)
+	}
+}
+
+// IntFromOpcode tries to retrieve bytes from Op.
+func IntFromOpcode(op Op) (int64, error) {
+	switch code := op.Code(); {
+	case code == opcode.PUSHM1:
+		return -1, nil
+	case code >= opcode.PUSH0 && code <= opcode.PUSH16:
+		return int64(code - opcode.PUSH0), nil
+	case code <= opcode.PUSHINT256:
+		return bigint.FromBytes(op.Param()).Int64(), nil
+	default:
+		return 0, fmt.Errorf("unexpected INT opcode %s", code)
+	}
+}

pkg/morph/event/opcodes_test.go

@@ -0,0 +1,82 @@
+package event
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBytesFromOpcode(t *testing.T) {
+	tests := [...][]byte{
+		[]byte("test"),
+		[]byte("test test"),
+		[]byte(""),
+		[]byte("1"),
+	}
+
+	bw := io.NewBufBinWriter()
+
+	for _, test := range tests {
+		emit.Bytes(bw.BinWriter, test)
+	}
+
+	var (
+		ctx = vm.NewContext(bw.Bytes())
+
+		op Op
+
+		gotBytes []byte
+		err      error
+	)
+
+	for _, test := range tests {
+		op = getNextOp(ctx)
+
+		gotBytes, err = BytesFromOpcode(op)
+
+		require.NoError(t, err)
+		require.Equal(t, test, gotBytes)
+	}
+}
+
+func TestIntFromOpcode(t *testing.T) {
+	tests := [...]int64{
+		-1,
+		-5,
+		15,
+		16,
+		1_000_000,
+	}
+
+	bw := io.NewBufBinWriter()
+
+	for _, test := range tests {
+		emit.Int(bw.BinWriter, test)
+	}
+
+	var (
+		ctx = vm.NewContext(bw.Bytes())
+
+		op Op
+
+		gotInt int64
+		err    error
+	)
+
+	for _, test := range tests {
+		op = getNextOp(ctx)
+
+		gotInt, err = IntFromOpcode(op)
+
+		require.NoError(t, err)
+		require.Equal(t, test, gotInt)
+	}
+}
+
+func getNextOp(ctx *vm.Context) (op Op) {
+	op.code, op.param, _ = ctx.Next()
+	return
+}