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/decode.go

@@ -0,0 +1,105 @@
+package graphson
+
+import (
+	"io"
+	"reflect"
+
+	"github.com/json-iterator/go"
+	"github.com/modern-go/reflect2"
+)
+
+type decodeExtension struct {
+	jsoniter.DummyExtension
+}
+
+// Unmarshal parses the graphson encoded data and stores the result
+// in the value pointed to by v.
+func Unmarshal(data []byte, v interface{}) error {
+	return config.Unmarshal(data, v)
+}
+
+// UnmarshalFromString parses the graphson encoded str and stores the result
+// in the value pointed to by v.
+func UnmarshalFromString(str string, v interface{}) error {
+	return config.UnmarshalFromString(str, v)
+}
+
+// Decoder defines a graphson decoder.
+type Decoder interface {
+	Decode(interface{}) error
+}
+
+// NewDecoder create a graphson decoder.
+func NewDecoder(r io.Reader) Decoder {
+	return config.NewDecoder(r)
+}
+
+// Unmarshaler is the interface implemented by types
+// that can unmarshal a graphson description of themselves.
+type Unmarshaler interface {
+	UnmarshalGraphson([]byte) error
+}
+
+// UpdateStructDescriptor decorates struct field encoders for graphson tags.
+func (ext decodeExtension) UpdateStructDescriptor(desc *jsoniter.StructDescriptor) {
+	for _, binding := range desc.Fields {
+		if tag, ok := binding.Field.Tag().Lookup("graphson"); ok && tag != "-" {
+			if dec := ext.DecoratorOfStructField(binding.Decoder, tag); dec != nil {
+				binding.Decoder = dec
+			}
+		}
+	}
+}
+
+// CreateDecoder returns a value decoder for type.
+func (ext decodeExtension) CreateDecoder(typ reflect2.Type) jsoniter.ValDecoder {
+	if dec := ext.DecoderOfRegistered(typ); dec != nil {
+		return dec
+	}
+	if dec := ext.DecoderOfUnmarshaler(typ); dec != nil {
+		return dec
+	}
+	if dec := ext.DecoderOfNative(typ); dec != nil {
+		return dec
+	}
+	switch typ.Kind() {
+	case reflect.Array:
+		return ext.DecoderOfArray(typ)
+	case reflect.Slice:
+		return ext.DecoderOfSlice(typ)
+	case reflect.Map:
+		return ext.DecoderOfMap(typ)
+	default:
+		return nil
+	}
+}
+
+// DecorateDecoder decorates an passed in value decoder for type.
+func (ext decodeExtension) DecorateDecoder(typ reflect2.Type, dec jsoniter.ValDecoder) jsoniter.ValDecoder {
+	if dec := ext.DecoratorOfRegistered(dec); dec != nil {
+		return dec
+	}
+	if dec := ext.DecoratorOfUnmarshaler(typ, dec); dec != nil {
+		return dec
+	}
+	if dec := ext.DecoratorOfTyper(typ, dec); dec != nil {
+		return dec
+	}
+	if dec := ext.DecoratorOfNative(typ, dec); dec != nil {
+		return dec
+	}
+	switch typ.Kind() {
+	case reflect.Ptr, reflect.Struct:
+		return dec
+	case reflect.Interface:
+		return ext.DecoratorOfInterface(typ, dec)
+	case reflect.Slice:
+		return ext.DecoratorOfSlice(typ, dec)
+	case reflect.Array:
+		return ext.DecoratorOfArray(dec)
+	case reflect.Map:
+		return ext.DecoratorOfMap(dec)
+	default:
+		return ext.DecoderOfError("graphson: unsupported type: " + typ.String())
+	}
+}