1 files changed, 114 insertions, 0 deletions
diff --git a/sd_login/monitor.go b/sd_login/monitor.go
new file mode 100644
index 0000000..2422f06
--- /dev/null
+++ b/sd_login/monitor.go
@@ -0,0 +1,114 @@
+// Copyright (C) 2016-2017 Luke Shumaker <lukeshu@sbcglobal.net>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sd_login
+
+import (
+	"git.lukeshu.com/go/libgnulinux/inotify"
+	"golang.org/x/sys/unix"
+)
+
+// A Monitor monitors several types of events, so you don't have to do
+// busy-polling.
+//
+// However, Monitor won't actually give you the event that happened,
+// you'll need to read it yourself.
+type Monitor struct {
+	in *inotify.Inotify
+}
+
+type MonitorCategory uint
+
+const (
+	MonitorSeats MonitorCategory = 1 << iota
+	MonitorSessions
+	MonitorUsers
+	MonitorMachines
+
+	MonitorAll = MonitorSeats | MonitorSessions | MonitorUsers | MonitorMachines
+)
+
+func NewMonitor(categories MonitorCategory) (*Monitor, error) {
+	if categories == 0 {
+		return nil, unix.EINVAL
+	}
+
+	in, err := inotify.InotifyInit1(inotify.IN_CLOEXEC)
+	if err != nil {
+		return nil, err
+	}
+
+	if categories&MonitorSeats != 0 {
+		_, err := in.AddWatch("/run/systemd/seats/", inotify.IN_MOVED_TO|inotify.IN_DELETE)
+		if err != nil {
+			in.Close()
+			return nil, err
+		}
+	}
+
+	if categories&MonitorSessions != 0 {
+		_, err := in.AddWatch("/run/systemd/sessions/", inotify.IN_MOVED_TO|inotify.IN_DELETE)
+		if err != nil {
+			in.Close()
+			return nil, err
+		}
+	}
+
+	if categories&MonitorUsers != 0 {
+		_, err := in.AddWatch("/run/systemd/users/", inotify.IN_MOVED_TO|inotify.IN_DELETE)
+		if err != nil {
+			in.Close()
+			return nil, err
+		}
+	}
+
+	if categories&MonitorMachines != 0 {
+		_, err := in.AddWatch("/run/systemd/machines/", inotify.IN_MOVED_TO|inotify.IN_DELETE)
+		if err != nil {
+			in.Close()
+			return nil, err
+		}
+	}
+
+	return &Monitor{in: in}, nil
+}
+
+// Close closes the monitor.  After calling Close, further calls to
+// the monitor will fail.
+func (m *Monitor) Close() error {
+	return m.in.Close()
+}
+
+// Flush discards any events that have happened since the last Flush
+// or Wait call.
+func (m *Monitor) Flush() error {
+	for {
+		ev, err := m.in.ReadNonblock()
+		if err != nil {
+			return err
+		}
+		if ev.Wd < 0 {
+			return nil
+		}
+	}
+}
+
+// Wait blocks until a watched for event has happened.  A single call
+// to Wait discards only discards first event; if multiple events
+// happen at once, multiple calls to Wait will immediately return
+// unless Flush is called.
+func (m *Monitor) Wait() error {
+	_, err := m.in.ReadBlock()
+	return err
+}