Add daemon support

experimental/daemon/instance.go

@@ -0,0 +1,58 @@
+package daemon
+
+import (
+	"context"
+	"os"
+	"sync"
+
+	"github.com/sagernet/sing-box"
+	"github.com/sagernet/sing-box/option"
+)
+
+type Instance struct {
+	access      sync.Mutex
+	boxInstance *box.Box
+	boxCancel   context.CancelFunc
+}
+
+func (i *Instance) Running() bool {
+	i.access.Lock()
+	defer i.access.Unlock()
+	return i.boxInstance != nil
+}
+
+func (i *Instance) Start(options option.Options) error {
+	i.access.Lock()
+	defer i.access.Unlock()
+	if i.boxInstance != nil {
+		i.boxCancel()
+		i.boxInstance.Close()
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	instance, err := box.New(ctx, options)
+	if err != nil {
+		cancel()
+		return err
+	}
+	err = instance.Start()
+	if err != nil {
+		cancel()
+		return err
+	}
+	i.boxInstance = instance
+	i.boxCancel = cancel
+	return nil
+}
+
+func (i *Instance) Close() error {
+	i.access.Lock()
+	defer i.access.Unlock()
+	if i.boxInstance == nil {
+		return os.ErrClosed
+	}
+	i.boxCancel()
+	err := i.boxInstance.Close()
+	i.boxInstance = nil
+	i.boxCancel = nil
+	return err
+}