From 7a4656b37c808f7d7eaf4efe42b32b465d310b4c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6ren=20Tempel?= <soeren+git@soeren-tempel.net>
Date: Wed, 26 Dec 2018 14:21:28 +0100
Subject: [PATCH] openFifo: remove helper function

Instead use os.OpenFile (which doesn't check the file type though). This
approach has the advantage that we can handle an mkfifo error in
createListener (where it is possible to terminate the program).

The worst case problem resulting of the fact that the file type is no
longer checked is if the file is removed between the syscall.Mkfifo in
createListener() and the os.Open() in recvInput(). In this case
recvInpu() would constantly require CPU time as os.Open() no longer
blocks. But this is (a) very unlikely and (b) requires the user to
manually remove the file.
---
 hii.go | 36 ++++++++++--------------------------
 1 file changed, 10 insertions(+), 26 deletions(-)

diff --git a/hii.go b/hii.go
index 324d16f..9e9ea4b 100644
--- a/hii.go
+++ b/hii.go
@@ -193,29 +193,6 @@ func normalize(name string) string {
 	return strings.Map(mfunc, name)
 }
 
-// Like os.OpenFile but for FIFOs.
-func openFifo(name string, flag int, perm os.FileMode) (*os.File, error) {
-	fi, err := os.Lstat(name)
-	if flag&os.O_CREATE != 0 && os.IsNotExist(err) {
-		err = syscall.Mkfifo(name, syscall.S_IFIFO|uint32(perm))
-		if err != nil {
-			return nil, err
-		}
-	} else if err != nil {
-		return nil, err
-	} else if fi.Mode()&os.ModeNamedPipe == 0 {
-		return nil, fmt.Errorf("%q is not a named pipe", name)
-	}
-
-	flag &^= os.O_CREATE // remove os.O_CREATE flag used above
-	fifo, err := os.OpenFile(name, flag, perm)
-	if err != nil {
-		return nil, err
-	}
-
-	return fifo, err
-}
-
 // Like ioutil.Write but doesn't truncate and appends instead.
 func appendFile(filename string, data []byte, perm os.FileMode) error {
 	file, err := os.OpenFile(filename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, perm)
@@ -342,10 +319,17 @@ func createListener(client *girc.Client, name string) (*ircDir, error) {
 		return nil, err
 	}
 
+	infp := filepath.Join(dir, infn)
+	err = syscall.Mkfifo(infp, syscall.S_IFIFO|0600)
+	if err != nil {
+		return nil, err
+	}
+
 	idir := &ircDir{name, make(chan bool, 1), dir, nil}
 	if name != masterChan {
 		err = storeName(idir)
 		if err != nil {
+			os.Remove(infp)
 			return nil, err
 		}
 	}
@@ -375,7 +359,7 @@ func removeListener(name string) error {
 	// hack to gracefully terminate the recvInput goroutine.
 	// assertion: If infp exists recvInput must be running.
 	dir.done <- true
-	fifo, err := openFifo(infp, os.O_WRONLY, 0600)
+	fifo, err := os.OpenFile(infp, os.O_WRONLY, 0600)
 	if err != nil && !os.IsNotExist(err) {
 		return err
 	}
@@ -433,11 +417,11 @@ func handleInput(client *girc.Client, name, input string) error {
 
 func recvInput(client *girc.Client, name string, dir *ircDir) {
 	// This goroutine must not terminate, otherwise the
-	// openFifo call in removeListener may cause a deadlock.
+	// OpenFile() call in removeListener may cause a deadlock.
 
 	infp := filepath.Join(dir.fp, infn)
 	for {
-		fifo, err := openFifo(infp, os.O_CREATE|os.O_RDONLY, 0600)
+		fifo, err := os.Open(infp)
 		select {
 		case <-dir.done:
 			return