80 lines
1.9 KiB
Go
80 lines
1.9 KiB
Go
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// Copyright (C) 2015 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package syncutil
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import (
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"sync"
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"time"
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)
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// TimeoutCond is a variant on Cond. It has roughly the same semantics regarding 'L' - it must be held
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// both when broadcasting and when calling TimeoutCondWaiter.Wait()
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// Call Broadcast() to broadcast to all waiters on the TimeoutCond. Call SetupWait to create a
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// TimeoutCondWaiter configured with the given timeout, which can then be used to listen for
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// broadcasts.
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type TimeoutCond struct {
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L sync.Locker
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ch chan struct{}
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}
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// TimeoutCondWaiter is a type allowing a consumer to wait on a TimeoutCond with a timeout. Wait() may be called multiple times,
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// and will return true every time that the TimeoutCond is broadcast to. Once the configured timeout
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// expires, Wait() will return false.
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// Call Stop() to release resources once this TimeoutCondWaiter is no longer needed.
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type TimeoutCondWaiter struct {
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c *TimeoutCond
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timer *time.Timer
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}
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func NewTimeoutCond(l sync.Locker) *TimeoutCond {
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return &TimeoutCond{
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L: l,
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}
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}
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func (c *TimeoutCond) Broadcast() {
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// ch.L must be locked when calling this function
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if c.ch != nil {
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close(c.ch)
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c.ch = nil
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}
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}
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func (c *TimeoutCond) SetupWait(timeout time.Duration) *TimeoutCondWaiter {
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timer := time.NewTimer(timeout)
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return &TimeoutCondWaiter{
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c: c,
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timer: timer,
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}
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}
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func (w *TimeoutCondWaiter) Wait() bool {
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// ch.L must be locked when calling this function
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// Ensure that the channel exists, since we're going to be waiting on it
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if w.c.ch == nil {
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w.c.ch = make(chan struct{})
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}
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ch := w.c.ch
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w.c.L.Unlock()
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defer w.c.L.Lock()
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select {
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case <-w.timer.C:
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return false
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case <-ch:
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return true
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}
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}
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func (w *TimeoutCondWaiter) Stop() {
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w.timer.Stop()
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}
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