Fix #1383: "Save with Sudo" rewrite (#1424)

* Rewrite save with sudo (Fixes #1383)

* Combine overrideFile & overrideFileAsRoot into 1 function

internal/buffer/backup.go

@@ -71,7 +71,7 @@ func (b *Buffer) Backup(checkTime bool) error {
 			}
 		}
 		return
-	})
+	}, false)
 
 	return err
 }

internal/buffer/save.go

@@ -27,76 +27,42 @@ const LargeFileThreshold = 50000
 // overwriteFile opens the given file for writing, truncating if one exists, and then calls
 // the supplied function with the file as io.Writer object, also making sure the file is
 // closed afterwards.
-func overwriteFile(name string, enc encoding.Encoding, fn func(io.Writer) error) (err error) {
-	var file *os.File
+func overwriteFile(name string, enc encoding.Encoding, fn func(io.Writer) error, withSudo bool) (err error) {
+    var writeCloser io.WriteCloser
 
-	if file, err = os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
-		return
-	}
+    if withSudo {
+        cmd := exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "bs=4k", "of="+name)
 
-	defer func() {
-		if e := file.Close(); e != nil && err == nil {
-			err = e
-		}
-	}()
+        if writeCloser, err = cmd.StdinPipe(); err != nil {
+            return
+        }
 
-	w := transform.NewWriter(file, enc.NewEncoder())
-	// w := bufio.NewWriter(file)
+        c := make(chan os.Signal, 1)
+        signal.Notify(c, os.Interrupt)
+        go func() {
+            <-c
+            cmd.Process.Kill()
+        }()
 
-	if err = fn(w); err != nil {
-		return
-	}
+        defer func() {
+            screenb := screen.TempFini()
+            if e := cmd.Run(); e != nil && err == nil {
+                err = e
+            }
+            screen.TempStart(screenb)
+        }()
+    } else if writeCloser, err = os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+        return
+    }
 
-	// err = w.Flush()
-	return
-}
+    w := transform.NewWriter(writeCloser, enc.NewEncoder())
+    err = fn(w)
 
-// overwriteFileAsRoot executes dd as root and then calls the supplied function
-// with dd's standard input as an io.Writer object. Dd opens the given file for writing,
-// truncating it if it exists, and writes what it receives on its standard input to the file.
-func overwriteFileAsRoot(name string, enc encoding.Encoding, fn func(io.Writer) error) (err error) {
-	var cmd *exec.Cmd
-	if runtime.GOOS == "windows" {
-		return errors.New("Save with sudo not supported on Windows")
-	} else if runtime.GOOS == "darwin" {
-		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "bs=4k", "of="+name)
-	} else {
-		cmd = exec.Command(config.GlobalSettings["sucmd"].(string), "dd", "status=none", "bs=4K", "of="+name)
-	}
-	var stdin io.WriteCloser
+    if e := writeCloser.Close(); e != nil && err == nil {
+        err = e
+    }
 
-	screenb := screen.TempFini()
-	defer screen.TempStart(screenb)
-
-	// This is a trap for Ctrl-C so that it doesn't kill micro
-	// Instead we trap Ctrl-C to kill the program we're running
-	c := make(chan os.Signal, 1)
-	signal.Notify(c, os.Interrupt)
-	go func() {
-		for range c {
-			cmd.Process.Kill()
-		}
-	}()
-
-	if stdin, err = cmd.StdinPipe(); err != nil {
-		return
-	}
-
-	if err = cmd.Start(); err != nil {
-		return
-	}
-
-	e := fn(stdin)
-
-	if err = stdin.Close(); err != nil {
-		return
-	}
-
-	if err = cmd.Wait(); err != nil {
-		return
-	}
-
-	return e
+    return
 }
 
 // Save saves the buffer to its default path
@@ -125,6 +91,9 @@ func (b *Buffer) saveToFile(filename string, withSudo bool) error {
 	if b.Type.Scratch {
 		return errors.New("Cannot save scratch buffer")
 	}
+	if withSudo && runtime.GOOS == "windows" {
+	    return errors.New("Save with sudo not supported on Windows")
+	}
 
 	b.UpdateRules()
 	if b.Settings["rmtrailingws"].(bool) {
@@ -208,14 +177,8 @@ func (b *Buffer) saveToFile(filename string, withSudo bool) error {
 		return
 	}
 
-	if withSudo {
-		err = overwriteFileAsRoot(absFilename, enc, fwriter)
-	} else {
-		err = overwriteFile(absFilename, enc, fwriter)
-	}
-
-	if err != nil {
-		return err
+	if err = overwriteFile(absFilename, enc, fwriter, withSudo); err != nil {
+	    return err
 	}
 
 	if !b.Settings["fastdirty"].(bool) {

internal/buffer/serialize.go

@@ -39,7 +39,7 @@ func (b *Buffer) Serialize() error {
 			b.ModTime,
 		})
 		return err
-	})
+	}, false)
 }
 
 func (b *Buffer) Unserialize() error {