data-cursor.go: added Reset() e Clean() functions

data-cursor.go

@@ -10,6 +10,8 @@ import (
 
 const (
 	initName    = "init"
+	cleanName   = "clean"
+	resetName   = "reset"
 	nextName    = "next"
 	currentName = "current"
 )
@@ -20,6 +22,8 @@ type dataCursor struct {
 	index       int
 	resource    any
 	nextFunc    Functor
+	cleanFunc   Functor
+	resetFunc   Functor
 	currentFunc Functor
 }
 
@@ -35,6 +39,26 @@ func (dc *dataCursor) String() string {
 	return "$(...)"
 }
 
+func (dc *dataCursor) Reset() (err error) {
+	if dc.resetFunc != nil {
+		ctx := cloneContext(dc.ctx)
+		if _, err = dc.resetFunc.Invoke(ctx, resetName, []any{}); err == nil {
+			dc.index = -1
+		}
+		exportObjects(dc.ctx, ctx)
+	}
+	return
+}
+
+func (dc *dataCursor) Clean() (err error) {
+	if dc.resetFunc != nil {
+		ctx := cloneContext(dc.ctx)
+		_, err = dc.cleanFunc.Invoke(ctx, cleanName, []any{})
+		exportObjects(dc.ctx, ctx)
+	}
+	return
+}
+
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
 	ctx := cloneContext(dc.ctx)
 	if item, err = dc.currentFunc.Invoke(ctx, currentName, []any{}); err == nil && item == nil {