go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/common/clock/external.go (about)

     1  // Copyright 2015 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package clock
    16  
    17  import (
    18  	"context"
    19  	"time"
    20  )
    21  
    22  // Unique value for clock key.
    23  var clockKey = "clock.Clock"
    24  
    25  // Factory is a generator function that produces a Clock instnace.
    26  type Factory func(context.Context) Clock
    27  
    28  // SetFactory creates a new Context using the supplied Clock factory.
    29  func SetFactory(ctx context.Context, f Factory) context.Context {
    30  	return context.WithValue(ctx, &clockKey, f)
    31  }
    32  
    33  // Set creates a new Context using the supplied Clock.
    34  func Set(ctx context.Context, c Clock) context.Context {
    35  	return SetFactory(ctx, func(context.Context) Clock { return c })
    36  }
    37  
    38  // Get returns the Clock set in the supplied Context, defaulting to
    39  // SystemClock() if none is set.
    40  func Get(ctx context.Context) (clock Clock) {
    41  	if v := ctx.Value(&clockKey); v != nil {
    42  		if f, ok := v.(Factory); ok {
    43  			clock = f(ctx)
    44  		}
    45  	}
    46  	if clock == nil {
    47  		clock = GetSystemClock()
    48  	}
    49  	return
    50  }
    51  
    52  // Now calls Clock.Now on the Clock instance stored in the supplied Context.
    53  func Now(ctx context.Context) time.Time {
    54  	return Get(ctx).Now()
    55  }
    56  
    57  // Sleep calls Clock.Sleep on the Clock instance stored in the supplied Context.
    58  func Sleep(ctx context.Context, d time.Duration) TimerResult {
    59  	return Get(ctx).Sleep(ctx, d)
    60  }
    61  
    62  // NewTimer calls Clock.NewTimer on the Clock instance stored in the supplied
    63  // Context.
    64  func NewTimer(ctx context.Context) Timer {
    65  	return Get(ctx).NewTimer(ctx)
    66  }
    67  
    68  // After waits a duration using the Clock instance stored in the supplied
    69  // Context. Then sends the current time over the returned channel.
    70  //
    71  // If the supplied Context is canceled, the timer will expire immediately.
    72  func After(ctx context.Context, d time.Duration) <-chan TimerResult {
    73  	return after(ctx, Get(ctx), d)
    74  }
    75  
    76  func after(ctx context.Context, c Clock, d time.Duration) <-chan TimerResult {
    77  	t := c.NewTimer(ctx)
    78  	t.Reset(d)
    79  	return t.GetC()
    80  }
    81  
    82  // Since is an equivalent of time.Since.
    83  func Since(ctx context.Context, t time.Time) time.Duration {
    84  	return Now(ctx).Sub(t)
    85  }
    86  
    87  // Until is an equivalent of time.Until.
    88  func Until(ctx context.Context, t time.Time) time.Duration {
    89  	return t.Sub(Now(ctx))
    90  }