| // Copyright 2015 The LUCI Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package clock |
| |
| import ( |
| "context" |
| "time" |
| ) |
| |
| type systemTimer struct { |
| // ctx is the underlying timer. It starts as nil, and is initialized on Reset. |
| ctx context.Context |
| |
| // timerC is the timer channel. |
| timerC chan TimerResult |
| |
| // timerStoppedC is a signal channel used by Stop to alert our monitor that |
| // this timer has been manually canceled. |
| timerStoppedC chan struct{} |
| // timerMonitorResultC returns true if the timer monitor was prematurely |
| // terminated, false if not. It is used by our timer monitor to indicate its |
| // status when stopped. |
| timerMonitorResultC chan bool |
| } |
| |
| var _ Timer = (*systemTimer)(nil) |
| |
| func newSystemTimer(ctx context.Context) Timer { |
| return &systemTimer{ |
| ctx: ctx, |
| timerC: make(chan TimerResult, 1), |
| } |
| } |
| |
| func (t *systemTimer) GetC() <-chan TimerResult { |
| return t.timerC |
| } |
| |
| func (t *systemTimer) Reset(d time.Duration) (running bool) { |
| running = t.Stop() |
| |
| // If our Context is already done, finish immediately. |
| if err := t.ctx.Err(); err != nil { |
| t.timerC <- TimerResult{Time: time.Now(), Err: err} |
| return |
| } |
| |
| // Start a monitor goroutine and our actual timer. Copy our channels, since |
| // future stop/reset will change the systemTimer's values and our goroutine |
| // should only operate on this round's values. |
| t.timerStoppedC = make(chan struct{}) |
| t.timerMonitorResultC = make(chan bool, 1) |
| |
| timerStoppedC, timerMonitorResultC := t.timerStoppedC, t.timerMonitorResultC |
| |
| realTimer := time.NewTimer(d) |
| go func() { |
| defer realTimer.Stop() |
| |
| interrupted := false |
| defer func() { |
| timerMonitorResultC <- interrupted |
| close(timerMonitorResultC) |
| }() |
| |
| select { |
| case <-timerStoppedC: |
| interrupted = true |
| |
| case <-t.ctx.Done(): |
| t.timerC <- TimerResult{Time: time.Now(), Err: t.ctx.Err()} |
| |
| case now := <-realTimer.C: |
| t.timerC <- TimerResult{Time: now, Err: nil} |
| } |
| }() |
| |
| return |
| } |
| |
| func (t *systemTimer) Stop() bool { |
| if t.timerStoppedC == nil { |
| return false |
| } |
| close(t.timerStoppedC) |
| t.timerStoppedC = nil |
| return <-t.timerMonitorResultC |
| } |