| // 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" |
| "sync" |
| "time" |
| ) |
| |
| // ContextDeadlineTag is the tag that will be applied to timers used for Context |
| // deadine timeout. |
| const ContextDeadlineTag = "go.chromium.org/luci/common/clock.ContextDeadlineTag" |
| |
| // clockContext is a context.Context implementation that uses Clock library |
| // constructs. |
| type clockContext struct { |
| sync.Mutex |
| context.Context |
| |
| deadline time.Time |
| err error // The error to return, in place of the embedded Context's. |
| } |
| |
| func (c *clockContext) Deadline() (time.Time, bool) { |
| return c.deadline, true |
| } |
| |
| func (c *clockContext) Err() error { |
| c.Lock() |
| defer c.Unlock() |
| |
| // Prefer our error over our parent's, if set. |
| if err := c.err; err != nil { |
| return err |
| } |
| return c.Context.Err() |
| } |
| |
| func (c *clockContext) setError(err error) { |
| c.Lock() |
| defer c.Unlock() |
| |
| c.err = err |
| } |
| |
| var _ context.Context = (*clockContext)(nil) |
| |
| // WithDeadline is a clock library implementation of context.WithDeadline that |
| // uses the clock library's time features instead of the Go time library. |
| // |
| // For more information, see context.WithDeadline. |
| func WithDeadline(parent context.Context, deadline time.Time) (context.Context, context.CancelFunc) { |
| if cur, ok := parent.Deadline(); ok && cur.Before(deadline) { |
| // The current deadline is already sooner than the new one. |
| return context.WithCancel(parent) |
| } |
| |
| parent, cancelFunc := context.WithCancel(parent) |
| c := &clockContext{ |
| Context: parent, |
| deadline: deadline, |
| } |
| |
| d := deadline.Sub(Now(c)) |
| if d <= 0 { |
| // Deadline has already passed. |
| c.setError(context.DeadlineExceeded) |
| cancelFunc() |
| return c, cancelFunc |
| } |
| |
| // Invoke our cancelFunc after the specified time. Register the timer now, so |
| // it gets registered in the testclock heap right away (and not at some |
| // undetermined later time when the goroutine starts). |
| t := NewTimer(Tag(c, ContextDeadlineTag)) |
| t.Reset(d) |
| go func() { |
| defer t.Stop() |
| |
| select { |
| case ar := <-t.GetC(): |
| if !ar.Incomplete() { |
| // Timer expired naturally. |
| c.setError(context.DeadlineExceeded) |
| cancelFunc() |
| } |
| case <-c.Done(): |
| // Context was canceled, can stop the timer / goroutine. |
| break |
| } |
| }() |
| return c, cancelFunc |
| } |
| |
| // WithTimeout is a clock library implementation of context.WithTimeout that |
| // uses the clock library's time features instead of the Go time library. |
| // |
| // For more information, see context.WithTimeout. |
| func WithTimeout(parent context.Context, timeout time.Duration) (context.Context, context.CancelFunc) { |
| return WithDeadline(parent, Now(parent).Add(timeout)) |
| } |