mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-11 02:34:43 +00:00
0e62a7d1a2
Signed-off-by: Robert Fritzsche <r.fritzsche@gridx.de>
131 lines
3.8 KiB
Go
131 lines
3.8 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package mono provides fast monotonic time.
|
|
// On most platforms, mono.Now is about 2x faster than time.Now.
|
|
// However, time.Now is really fast, and nicer to use.
|
|
//
|
|
// For almost all purposes, you should use time.Now.
|
|
//
|
|
// Package mono exists because we get the current time multiple
|
|
// times per network packet, at which point it makes a
|
|
// measurable difference.
|
|
package mono
|
|
|
|
import (
|
|
"fmt"
|
|
"sync/atomic"
|
|
"time"
|
|
_ "unsafe" // for go:linkname
|
|
)
|
|
|
|
// Time is the number of nanoseconds elapsed since an unspecified reference start time.
|
|
type Time int64
|
|
|
|
// Now returns the current monotonic time.
|
|
func Now() Time {
|
|
// On a newly started machine, the monotonic clock might be very near zero.
|
|
// Thus mono.Time(0).Before(mono.Now.Add(-time.Minute)) might yield true.
|
|
// The corresponding package time expression never does, if the wall clock is correct.
|
|
// Preserve this correspondence by increasing the "base" monotonic clock by a fair amount.
|
|
const baseOffset int64 = 1 << 55 // approximately 10,000 hours in nanoseconds
|
|
return Time(now() + baseOffset)
|
|
}
|
|
|
|
// Since returns the time elapsed since t.
|
|
func Since(t Time) time.Duration {
|
|
return time.Duration(Now() - t)
|
|
}
|
|
|
|
// Sub returns t-n, the duration from n to t.
|
|
func (t Time) Sub(n Time) time.Duration {
|
|
return time.Duration(t - n)
|
|
}
|
|
|
|
// Add returns t+d.
|
|
func (t Time) Add(d time.Duration) Time {
|
|
return t + Time(d)
|
|
}
|
|
|
|
// After reports t > n, whether t is after n.
|
|
func (t Time) After(n Time) bool {
|
|
return t > n
|
|
}
|
|
|
|
// Before reports t < n, whether t is before n.
|
|
func (t Time) Before(n Time) bool {
|
|
return t < n
|
|
}
|
|
|
|
// IsZero reports whether t == 0.
|
|
func (t Time) IsZero() bool {
|
|
return t == 0
|
|
}
|
|
|
|
// StoreAtomic does an atomic store *t = new.
|
|
func (t *Time) StoreAtomic(new Time) {
|
|
atomic.StoreInt64((*int64)(t), int64(new))
|
|
}
|
|
|
|
// LoadAtomic does an atomic load *t.
|
|
func (t *Time) LoadAtomic() Time {
|
|
return Time(atomic.LoadInt64((*int64)(t)))
|
|
}
|
|
|
|
//go:linkname now runtime.nanotime1
|
|
func now() int64
|
|
|
|
// baseWall and baseMono are a pair of almost-identical times used to correlate a Time with a wall time.
|
|
var (
|
|
baseWall time.Time
|
|
baseMono Time
|
|
)
|
|
|
|
func init() {
|
|
baseWall = time.Now()
|
|
baseMono = Now()
|
|
}
|
|
|
|
// String prints t, including an estimated equivalent wall clock.
|
|
// This is best-effort only, for rough debugging purposes only.
|
|
// Since t is a monotonic time, it can vary from the actual wall clock by arbitrary amounts.
|
|
// Even in the best of circumstances, it may vary by a few milliseconds.
|
|
func (t Time) String() string {
|
|
return fmt.Sprintf("mono.Time(ns=%d, estimated wall=%v)", int64(t), baseWall.Add(t.Sub(baseMono)).Truncate(0))
|
|
}
|
|
|
|
// WallTime returns an approximate wall time that corresponded to t.
|
|
func (t Time) WallTime() time.Time {
|
|
if !t.IsZero() {
|
|
return baseWall.Add(t.Sub(baseMono)).Truncate(0)
|
|
}
|
|
return time.Time{}
|
|
}
|
|
|
|
// MarshalJSON formats t for JSON as if it were a time.Time.
|
|
// We format Time this way for backwards-compatibility.
|
|
// This is best-effort only. Time does not survive a MarshalJSON/UnmarshalJSON round trip unchanged.
|
|
// Since t is a monotonic time, it can vary from the actual wall clock by arbitrary amounts.
|
|
// Even in the best of circumstances, it may vary by a few milliseconds.
|
|
func (t Time) MarshalJSON() ([]byte, error) {
|
|
tt := t.WallTime()
|
|
return tt.MarshalJSON()
|
|
}
|
|
|
|
// UnmarshalJSON sets t according to data.
|
|
// This is best-effort only. Time does not survive a MarshalJSON/UnmarshalJSON round trip unchanged.
|
|
func (t *Time) UnmarshalJSON(data []byte) error {
|
|
var tt time.Time
|
|
err := tt.UnmarshalJSON(data)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if tt.IsZero() {
|
|
*t = 0
|
|
return nil
|
|
}
|
|
*t = Now().Add(-time.Since(tt))
|
|
return nil
|
|
}
|