Export performance optimization (#475)

* recreate metadata path if needed, before exporting data

vendor/github.com/modern-go/reflect2/unsafe_ptr.go

@@ -0,0 +1,46 @@
+package reflect2
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+type UnsafePtrType struct {
+	unsafeType
+}
+
+func newUnsafePtrType(cfg *frozenConfig, type1 reflect.Type) *UnsafePtrType {
+	return &UnsafePtrType{
+		unsafeType: *newUnsafeType(cfg, type1),
+	}
+}
+
+func (type2 *UnsafePtrType) IsNil(obj interface{}) bool {
+	if obj == nil {
+		return true
+	}
+	objEFace := unpackEFace(obj)
+	assertType("Type.IsNil argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIsNil(objEFace.data)
+}
+
+func (type2 *UnsafePtrType) UnsafeIsNil(ptr unsafe.Pointer) bool {
+	if ptr == nil {
+		return true
+	}
+	return *(*unsafe.Pointer)(ptr) == nil
+}
+
+func (type2 *UnsafePtrType) LikePtr() bool {
+	return true
+}
+
+func (type2 *UnsafePtrType) Indirect(obj interface{}) interface{} {
+	objEFace := unpackEFace(obj)
+	assertType("Type.Indirect argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIndirect(objEFace.data)
+}
+
+func (type2 *UnsafePtrType) UnsafeIndirect(ptr unsafe.Pointer) interface{} {
+	return packEFace(type2.rtype, *(*unsafe.Pointer)(ptr))
+}