| // Copyright 2015 The Vanadium 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 discovery |
| |
| import "sync" |
| |
| // A Barrier is a simple incremental barrier that runs a done closure after |
| // all closures returned by Add() have been invoked. The done closure will |
| // run only once and run in a separate goroutine. |
| type Barrier struct { |
| mu sync.Mutex |
| n int // GUARDED_BY(mu) |
| |
| done func() |
| } |
| |
| // Add increments the barrier. Each closure returned by Add() should eventually |
| // be run once, otherwise 'done' will never be run. It returns no-op function |
| // if the done closure has been already called. |
| func (b *Barrier) Add() func() { |
| b.mu.Lock() |
| if b.done == nil { |
| b.mu.Unlock() |
| return func() {} |
| } |
| b.n++ |
| b.mu.Unlock() |
| return b.run |
| } |
| |
| func (b *Barrier) run() { |
| b.mu.Lock() |
| b.n-- |
| if b.n > 0 { |
| b.mu.Unlock() |
| return |
| } |
| done := b.done |
| b.done = nil |
| b.mu.Unlock() |
| if done != nil { |
| go done() |
| } |
| } |
| |
| func NewBarrier(done func()) *Barrier { |
| return &Barrier{done: done} |
| } |