logdog: Add bundler library.

client/internal/logdog/butler/bundler/timeoutCond.go

Index: client/internal/logdog/butler/bundler/timeoutCond.go
diff --git a/client/internal/logdog/butler/bundler/timeoutCond.go b/client/internal/logdog/butler/bundler/timeoutCond.go
new file mode 100644
index 0000000000000000000000000000000000000000..dfa7168660bc654d6b6ef87434aa960f6b9e182a
--- /dev/null
+++ b/client/internal/logdog/butler/bundler/timeoutCond.go
@@ -0,0 +1,73 @@
+// Copyright 2015 The Chromium 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 bundler
+
+import (
+	"sync"
+	"time"
+
+	"github.com/luci/luci-go/common/clock"
+)
+
+type timeoutCond struct {
+	*sync.Cond
+
+	clock clock.Clock
+}
+
+func newTimeoutCond(c clock.Clock, l sync.Locker) *timeoutCond {
+	return &timeoutCond{
+		Cond:  sync.NewCond(l),
+		clock: c,
+	}
+}
+
+func (c *timeoutCond) waitTimeout(d time.Duration) (timeout bool) {
+	if d <= 0 {
+		// We've already expired, so don't bother waiting.
+		return
+	}
+
+	// Kick off a timer to Broadcast when it has completed.
+	doneC := make(chan struct{})
+	finishedC := make(chan bool)
+	defer func() {
+		close(doneC)
+		timeout = <-finishedC
+	}()
+
+	go func() {
+		timerExpired := false
+		defer func() {
+			finishedC <- timerExpired
+		}()
+
+		t := c.clock.NewTimer()
+		defer t.Stop()
+		t.Reset(d)
+
+		// Quickly own our lock. This ensures that we have entered our Wait()
+		// method, which in turn ensures that our Broadcast will wake it if
+		// necessary.
+		func() {
+			c.L.Lock()
+			defer c.L.Unlock()
+		}()
+
+		select {
+		case <-doneC:
+			break
+
+		case <-t.GetC():
+			timerExpired = true
+			c.Broadcast()
+		}
+	}()
+
+	// Wait on our Cond. This will be released when either something else
+	// Broadcasts. That "something else" may be our timer expiring.
+	c.Wait()
+	return
+}