logdog: Add bundler library.

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

+// 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
+}