bfs commit (exprimental)

internal/utils/bfs/errors.go

@@ -2,7 +2,10 @@
 
 package bfs
 
-import "errors"
+import (
+	"errors"
+	"os"
+)
 
 var ErrClosed = errors.New("the file closed")
 var ErrInvalidHash = errors.New("invalid hash")
@@ -11,3 +14,7 @@ var ErrFileIsWriting = errors.New("the file is writing")
 func IsWritingErr(err error) bool {
 	return err != nil && errors.Is(err, ErrFileIsWriting)
 }
+
+func IsNotExist(err error) bool {
+	return err != nil && os.IsNotExist(err)
+}