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/lazy.go

@@ -0,0 +1,70 @@
+package graphson
+
+import (
+	"sync"
+	"unsafe"
+
+	"github.com/json-iterator/go"
+	"github.com/modern-go/reflect2"
+	"github.com/pkg/errors"
+)
+
+// LazyEncoderOf returns a lazy encoder for type.
+func (encodeExtension) LazyEncoderOf(typ reflect2.Type) jsoniter.ValEncoder {
+	return &lazyEncoder{resolve: func() jsoniter.ValEncoder {
+		return config.EncoderOf(typ)
+	}}
+}
+
+// LazyDecoderOf returns a lazy unique decoder for type.
+func (decodeExtension) LazyDecoderOf(typ reflect2.Type) jsoniter.ValDecoder {
+	return &lazyDecoder{resolve: func() jsoniter.ValDecoder {
+		dec := config.DecoderOf(reflect2.PtrTo(typ))
+		if td, ok := dec.(typeDecoder); ok {
+			td.typeChecker = &uniqueType{elemChecker: td.typeChecker}
+			dec = td
+		}
+		return dec
+	}}
+}
+
+type lazyEncoder struct {
+	jsoniter.ValEncoder
+	resolve func() jsoniter.ValEncoder
+	once    sync.Once
+}
+
+func (enc *lazyEncoder) Encode(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+	enc.once.Do(func() { enc.ValEncoder = enc.resolve() })
+	enc.ValEncoder.Encode(ptr, stream)
+}
+
+func (enc *lazyEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	enc.once.Do(func() { enc.ValEncoder = enc.resolve() })
+	return enc.ValEncoder.IsEmpty(ptr)
+}
+
+type lazyDecoder struct {
+	jsoniter.ValDecoder
+	resolve func() jsoniter.ValDecoder
+	once    sync.Once
+}
+
+func (dec *lazyDecoder) Decode(ptr unsafe.Pointer, iter *jsoniter.Iterator) {
+	dec.once.Do(func() { dec.ValDecoder = dec.resolve() })
+	dec.ValDecoder.Decode(ptr, iter)
+}
+
+type uniqueType struct {
+	typ         Type
+	once        sync.Once
+	elemChecker typeChecker
+}
+
+func (u *uniqueType) CheckType(other Type) error {
+	u.once.Do(func() { u.typ = other })
+	if u.typ != other {
+		return errors.Errorf("expect type %s, but found %s", u.typ, other)
+	}
+	return u.elemChecker.CheckType(u.typ)
+}