From 3f0761af9288ecbadcaa9f646b864991b9819792 Mon Sep 17 00:00:00 2001
From: Will Scott <will@cypherpunk.email>
Date: Sat, 27 Feb 2021 09:57:58 -0800
Subject: [PATCH] open file for write when truncating

fix #19
---
 file.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/file.go b/file.go
index 0f0a232..9d22651 100644
--- a/file.go
+++ b/file.go
@@ -3,6 +3,7 @@ package nfs
 import (
 	"io"
 	"log"
+	"math"
 	"os"
 	"time"
 
@@ -234,10 +235,13 @@ func (s *SetFileAttributes) Apply(changer billy.Change, fs billy.Filesystem, fil
 		if curr.Mode()&os.ModeSymlink != 0 {
 			return &NFSStatusError{NFSStatusNotSupp, os.ErrInvalid}
 		}
-		fp, err := fs.Open(file)
+		fp, err := fs.OpenFile(file, os.O_WRONLY|os.O_EXCL, 0)
 		if err != nil {
 			return err
 		}
+		if *s.SetSize > math.MaxInt64 {
+			return &NFSStatusError{NFSStatusInval, os.ErrInvalid}
+		}
 		if err := fp.Truncate(int64(*s.SetSize)); err != nil {
 			return err
 		}