[feat] only one systray can be in execution

Create a systray.pid file to check if another systray is in execution
and only one systray is allowed to be running.

- Resolves: #17

1 files changed, 87 insertions, 0 deletions

diff --git a/pid.go b/pid.go
new file mode 100644
index 0000000..0636110
--- /dev/null
+++ b/pid.go
@@ -0,0 +1,87 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"syscall"
+
+	"0xacab.org/leap/bitmask-systray/bitmask"
+)
+
+var pidFile = filepath.Join(bitmask.ConfigPath, "systray.pid")
+
+func acquirePID() error {
+	pid := syscall.Getpid()
+	current, err := getPID()
+	if err != nil {
+		return err
+	}
+
+	if current != 0 && current != pid {
+		proc, err := os.FindProcess(current)
+		if err != nil {
+			return err
+		}
+		err = proc.Signal(syscall.Signal(0))
+		if err == nil {
+			return fmt.Errorf("Another systray is running with pid: %d", current)
+		}
+	}
+
+	return setPID(pid)
+}
+
+func releasePID() error {
+	pid := syscall.Getpid()
+	current, err := getPID()
+	if err != nil {
+		return err
+	}
+	if current != 0 && current != pid {
+		return fmt.Errorf("Can't release pid file, is not own by this process")
+	}
+
+	if current == pid {
+		return os.Remove(pidFile)
+	}
+	return nil
+}
+
+func getPID() (int, error) {
+	_, err := os.Stat(pidFile)
+	if os.IsNotExist(err) {
+		return 0, nil
+	}
+	if err != nil {
+		return 0, err
+	}
+
+	file, err := os.Open(pidFile)
+	if err != nil {
+		return 0, err
+	}
+	defer file.Close()
+
+	b, err := ioutil.ReadAll(file)
+	if err != nil {
+		return 0, err
+	}
+	if len(b) == 0 {
+		return 0, nil
+	}
+	return strconv.Atoi(string(b))
+}
+
+func setPID(pid int) error {
+	file, err := os.Create(pidFile)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	_, err = file.WriteString(fmt.Sprintf("%d", pid))
+	return err
+}