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// Copyright (C) 2022 Andrew Ayer
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
// Except as contained in this notice, the name(s) of the above copyright
// holders shall not be used in advertising or otherwise to promote the
// sale, use or other dealings in this Software without prior written
// authorization.
// Package unix implements a net.Listener for UNIX domain sockets.
package unix // import "src.agwa.name/go-listener/unix"
import (
"fmt"
"net"
"os"
"path/filepath"
"time"
)
type watchedListener struct {
listener *net.UnixListener
closed chan struct{}
}
func newWatchedListener(listener *net.UnixListener) *watchedListener {
return &watchedListener{
listener: listener,
closed: make(chan struct{}),
}
}
func (wl *watchedListener) Accept() (net.Conn, error) {
return wl.listener.Accept()
}
func (wl *watchedListener) Close() error {
close(wl.closed)
return wl.listener.Close()
}
func (wl *watchedListener) Addr() net.Addr {
return wl.listener.Addr()
}
func (wl *watchedListener) watch(path string, info os.FileInfo) {
ticker := time.NewTicker(5 * time.Second)
defer ticker.Stop()
for {
select {
case <-wl.closed:
return
case <-ticker.C:
latestInfo, err := os.Lstat(path)
if !(err == nil && os.SameFile(info, latestInfo)) {
wl.listener.Close()
return
}
}
}
}
// Create a listening UNIX domain socket with the given path and filesystem
// permissions. If a file already exists at the path, it is replaced. If
// the UNIX domain socket file is removed or changed, then within 5 seconds
// the net.Listener will be closed, and Accept will return an error.
func Listen(path string, mode os.FileMode) (net.Listener, error) {
tempDir, err := os.MkdirTemp(filepath.Dir(path), ".tmp")
if err != nil {
return nil, fmt.Errorf("error creating temporary directory to hold Unix socket: %w", err)
}
defer os.Remove(tempDir)
tempPath := filepath.Join(tempDir, "socket")
tempListener, err := net.ListenUnix("unix", &net.UnixAddr{Net: "unix", Name: tempPath})
if err != nil {
return nil, err
}
tempListener.SetUnlinkOnClose(false)
defer os.Remove(tempPath)
defer func() {
if tempListener != nil {
tempListener.Close()
}
}()
if err := os.Chmod(tempPath, mode); err != nil {
return nil, err
}
fileInfo, err := os.Lstat(tempPath)
if err != nil {
return nil, err
}
if err := os.Rename(tempPath, path); err != nil {
return nil, err
}
listener := newWatchedListener(tempListener)
tempListener = nil
go listener.watch(path, fileInfo)
return listener, nil
}
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