move lib/go/gremlin to ent/dialect (#1192)

Summary:
Pull Request resolved: https://github.com/facebookexternal/fbc/pull/1192

Pull Request resolved: https://github.com/facebookincubator/ent/pull/11

Reviewed By: alexsn

Differential Revision: D16377224

fbshipit-source-id: 07ca7436eb9b64fbe2299568560b91466b2417ba

dialect/gremlin/encoding/graphson/raw.go

@@ -0,0 +1,31 @@
+package graphson
+
+import (
+	"github.com/pkg/errors"
+)
+
+// RawMessage is a raw encoded graphson value.
+type RawMessage []byte
+
+// RawMessage must implement Marshaler/Unmarshaler interfaces.
+var (
+	_ Marshaler   = (*RawMessage)(nil)
+	_ Unmarshaler = (*RawMessage)(nil)
+)
+
+// MarshalGraphson returns m as the graphson encoding of m.
+func (m RawMessage) MarshalGraphson() ([]byte, error) {
+	if m == nil {
+		return []byte("null"), nil
+	}
+	return m, nil
+}
+
+// UnmarshalGraphson sets *m to a copy of data.
+func (m *RawMessage) UnmarshalGraphson(data []byte) error {
+	if m == nil {
+		return errors.New("graphson.RawMessage: UnmarshalGraphson on nil pointer")
+	}
+	*m = append((*m)[0:0], data...)
+	return nil
+}