Merge pull request #74 from bozaro/safe-write-lib

Write library by temporary file creation to avoid in-place modification executed library

Author: Peefy

util.go

@@ -1,29 +1,41 @@
 package lib
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 )
 
 func writeLib(libDir, libFullName string, content []byte, versionMatched bool) error {
 	libFullPath := filepath.Join(libDir, libFullName)
 	_, err := os.Stat(libFullPath)
-	if os.IsNotExist(err) || !versionMatched {
-		err = os.MkdirAll(libDir, 0777)
+	if !os.IsNotExist(err) && versionMatched {
+		return err
+	}
+	if err := os.MkdirAll(libDir, 0777); err != nil {
+		return err
+	}
+	for pass := 0; ; pass++ {
+		tmpFullPath := fmt.Sprintf("%s~%d", libFullPath, pass)
+		tmpFile, err := os.OpenFile(tmpFullPath, os.O_CREATE|os.O_RDWR|os.O_EXCL, 0755)
 		if err != nil {
+			if os.IsExist(err) {
+				continue
+			}
 			return err
 		}
-		libFile, err := os.Create(libFullPath)
 		defer func() {
-			libFile.Close()
+			tmpFile.Close()
+			_ = os.Remove(tmpFullPath)
 		}()
-		if err != nil {
+
+		if _, err = tmpFile.Write(content); err != nil {
 			return err
 		}
-		_, err = libFile.Write(content)
-		if err != nil {
+		if err := os.Rename(tmpFullPath, libFullPath); err != nil {
 			return err
 		}
+		break
 	}
-	return err
+	return nil
 }