Move Linux client & common packages into a public repo.

portlist/poller.go

@@ -0,0 +1,59 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package portlist
+
+import (
+	"time"
+)
+
+type Poller struct {
+	C      chan List     // new data when it arrives; closed when done
+	quitCh chan struct{} // close this to force exit
+	Err    error         // last returned error code, if any
+	prev   List          // most recent data
+}
+
+func NewPoller() (*Poller, error) {
+	p := &Poller{
+		C:      make(chan List),
+		quitCh: make(chan struct{}),
+	}
+	// Do one initial poll synchronously, so the caller can react
+	// to any obvious errors.
+	p.prev, p.Err = GetList(nil)
+	return p, p.Err
+}
+
+func (p *Poller) Close() {
+	close(p.quitCh)
+	<-p.C
+}
+
+// Poll periodically. Run this in a goroutine if you want.
+func (p *Poller) Run() error {
+	defer close(p.C)
+	tick := time.NewTicker(POLL_SECONDS * time.Second)
+	defer tick.Stop()
+
+	// Send out the pre-generated initial value
+	p.C <- p.prev
+
+	for {
+		select {
+		case <-tick.C:
+			pl, err := GetList(p.prev)
+			if err != nil {
+				p.Err = err
+				return p.Err
+			}
+			if !pl.SameInodes(p.prev) {
+				p.prev = pl
+				p.C <- pl
+			}
+		case <-p.quitCh:
+			return nil
+		}
+	}
+}