45 lines
1019 B
Go
45 lines
1019 B
Go
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package missinggo
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import (
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"sync"
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"time"
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)
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// Monotonic time represents time since an arbitrary point in the past, where
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// the concept of now is only ever moving in a positive direction.
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type MonotonicTime struct {
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skewedStdTime time.Time
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}
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func (me MonotonicTime) Sub(other MonotonicTime) time.Duration {
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return me.skewedStdTime.Sub(other.skewedStdTime)
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}
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var (
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stdNowFunc = time.Now
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monotonicMu sync.Mutex
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lastStdNow time.Time
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monotonicSkew time.Duration
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)
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func skewedStdNow() time.Time {
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monotonicMu.Lock()
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defer monotonicMu.Unlock()
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stdNow := stdNowFunc()
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if !lastStdNow.IsZero() && stdNow.Before(lastStdNow) {
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monotonicSkew += lastStdNow.Sub(stdNow)
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}
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lastStdNow = stdNow
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return stdNow.Add(monotonicSkew)
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}
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// Consecutive calls always produce the same or greater time than previous
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// calls.
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func MonotonicNow() MonotonicTime {
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return MonotonicTime{skewedStdNow()}
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}
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func MonotonicSince(since MonotonicTime) (ret time.Duration) {
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return skewedStdNow().Sub(since.skewedStdTime)
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}
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