Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/json-iterator/go/reflect_optional.go

@@ -0,0 +1,133 @@
+package jsoniter
+
+import (
+	"github.com/modern-go/reflect2"
+	"reflect"
+	"unsafe"
+)
+
+func decoderOfOptional(ctx *ctx, typ reflect2.Type) ValDecoder {
+	ptrType := typ.(*reflect2.UnsafePtrType)
+	elemType := ptrType.Elem()
+	decoder := decoderOfType(ctx, elemType)
+	if ctx.prefix == "" && elemType.Kind() == reflect.Ptr {
+		return &dereferenceDecoder{elemType, decoder}
+	}
+	return &OptionalDecoder{elemType, decoder}
+}
+
+func encoderOfOptional(ctx *ctx, typ reflect2.Type) ValEncoder {
+	ptrType := typ.(*reflect2.UnsafePtrType)
+	elemType := ptrType.Elem()
+	elemEncoder := encoderOfType(ctx, elemType)
+	encoder := &OptionalEncoder{elemEncoder}
+	return encoder
+}
+
+type OptionalDecoder struct {
+	ValueType    reflect2.Type
+	ValueDecoder ValDecoder
+}
+
+func (decoder *OptionalDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	if iter.ReadNil() {
+		*((*unsafe.Pointer)(ptr)) = nil
+	} else {
+		if *((*unsafe.Pointer)(ptr)) == nil {
+			//pointer to null, we have to allocate memory to hold the value
+			newPtr := decoder.ValueType.UnsafeNew()
+			decoder.ValueDecoder.Decode(newPtr, iter)
+			*((*unsafe.Pointer)(ptr)) = newPtr
+		} else {
+			//reuse existing instance
+			decoder.ValueDecoder.Decode(*((*unsafe.Pointer)(ptr)), iter)
+		}
+	}
+}
+
+type dereferenceDecoder struct {
+	// only to deference a pointer
+	valueType    reflect2.Type
+	valueDecoder ValDecoder
+}
+
+func (decoder *dereferenceDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		//pointer to null, we have to allocate memory to hold the value
+		newPtr := decoder.valueType.UnsafeNew()
+		decoder.valueDecoder.Decode(newPtr, iter)
+		*((*unsafe.Pointer)(ptr)) = newPtr
+	} else {
+		//reuse existing instance
+		decoder.valueDecoder.Decode(*((*unsafe.Pointer)(ptr)), iter)
+	}
+}
+
+type OptionalEncoder struct {
+	ValueEncoder ValEncoder
+}
+
+func (encoder *OptionalEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		stream.WriteNil()
+	} else {
+		encoder.ValueEncoder.Encode(*((*unsafe.Pointer)(ptr)), stream)
+	}
+}
+
+func (encoder *OptionalEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	return *((*unsafe.Pointer)(ptr)) == nil
+}
+
+type dereferenceEncoder struct {
+	ValueEncoder ValEncoder
+}
+
+func (encoder *dereferenceEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		stream.WriteNil()
+	} else {
+		encoder.ValueEncoder.Encode(*((*unsafe.Pointer)(ptr)), stream)
+	}
+}
+
+func (encoder *dereferenceEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	dePtr := *((*unsafe.Pointer)(ptr))
+	if dePtr == nil {
+		return true
+	}
+	return encoder.ValueEncoder.IsEmpty(dePtr)
+}
+
+func (encoder *dereferenceEncoder) IsEmbeddedPtrNil(ptr unsafe.Pointer) bool {
+	deReferenced := *((*unsafe.Pointer)(ptr))
+	if deReferenced == nil {
+		return true
+	}
+	isEmbeddedPtrNil, converted := encoder.ValueEncoder.(IsEmbeddedPtrNil)
+	if !converted {
+		return false
+	}
+	fieldPtr := unsafe.Pointer(deReferenced)
+	return isEmbeddedPtrNil.IsEmbeddedPtrNil(fieldPtr)
+}
+
+type referenceEncoder struct {
+	encoder ValEncoder
+}
+
+func (encoder *referenceEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	encoder.encoder.Encode(unsafe.Pointer(&ptr), stream)
+}
+
+func (encoder *referenceEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	return encoder.encoder.IsEmpty(unsafe.Pointer(&ptr))
+}
+
+type referenceDecoder struct {
+	decoder ValDecoder
+}
+
+func (decoder *referenceDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	decoder.decoder.Decode(unsafe.Pointer(&ptr), iter)
+}