144 lines
3.7 KiB
Go
144 lines
3.7 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package tstime defines Tailscale-specific time utilities.
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package tstime
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import (
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"errors"
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"fmt"
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"sync"
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"time"
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"go4.org/mem"
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)
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var memZ = mem.S("Z")
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// zoneOf returns the RFC3339 zone suffix (either "Z" or like
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// "+08:30"), or the empty string if it's invalid or not something we
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// want to cache.
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func zoneOf(s mem.RO) mem.RO {
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if mem.HasSuffix(s, memZ) {
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return memZ
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}
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if s.Len() < len("2020-04-05T15:56:00+08:00") {
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// Too short, invalid? Let time.Parse fail on it.
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return mem.S("")
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}
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zone := s.SliceFrom(s.Len() - len("+08:00"))
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if c := zone.At(0); c == '+' || c == '-' {
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min := zone.SliceFrom(len("+08:"))
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if min.EqualString("00") || min.EqualString("15") || min.EqualString("30") {
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return zone
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}
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}
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return mem.S("")
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}
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// locCache maps from hash of zone offset suffix string ("+08:00") =>
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// {zone string, *time.Location (from FixedLocation)}.
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var locCache sync.Map
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type locCacheEntry struct {
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zone string
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loc *time.Location
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}
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func getLocation(zone, timeValue mem.RO) (*time.Location, error) {
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if zone.EqualString("Z") {
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return time.UTC, nil
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}
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key := zone.MapHash()
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if entry, ok := locCache.Load(key); ok {
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// We're keying only on a hash; double-check zone to ensure no spurious collisions.
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e := entry.(locCacheEntry)
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if zone.EqualString(e.zone) {
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return e.loc, nil
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}
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}
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// TODO(bradfitz): just parse it and call time.FixedLocation.
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// For now, just have time.Parse do it once:
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t, err := time.Parse(time.RFC3339Nano, timeValue.StringCopy())
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if err != nil {
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return nil, err
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}
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loc := t.Location()
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locCache.LoadOrStore(key, locCacheEntry{zone: zone.StringCopy(), loc: loc})
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return loc, nil
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}
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func parse3339m(s mem.RO) (time.Time, error) {
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zone := zoneOf(s)
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if zone.Len() == 0 {
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// Invalid or weird timezone offset. Use slow path,
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// which'll probably return an error.
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return time.Parse(time.RFC3339Nano, s.StringCopy())
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}
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loc, err := getLocation(zone, s)
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if err != nil {
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return time.Time{}, err
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}
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s = s.SliceTo(s.Len() - zone.Len()) // remove zone suffix
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var year, mon, day, hr, min, sec, nsec int
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const baseLen = len("2020-04-05T15:56:00")
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if s.Len() < baseLen ||
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!parseInt(s.SliceTo(4), &year) ||
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s.At(4) != '-' ||
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!parseInt(s.Slice(5, 7), &mon) ||
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s.At(7) != '-' ||
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!parseInt(s.Slice(8, 10), &day) ||
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s.At(10) != 'T' ||
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!parseInt(s.Slice(11, 13), &hr) ||
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s.At(13) != ':' ||
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!parseInt(s.Slice(14, 16), &min) ||
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s.At(16) != ':' ||
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!parseInt(s.Slice(17, 19), &sec) {
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return time.Time{}, errors.New("invalid time")
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}
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nsStr := s.SliceFrom(baseLen)
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if nsStr.Len() != 0 {
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if nsStr.At(0) != '.' {
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return time.Time{}, errors.New("invalid optional nanosecond prefix")
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}
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nsStr = nsStr.SliceFrom(1)
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if !parseInt(nsStr, &nsec) {
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return time.Time{}, fmt.Errorf("invalid optional nanosecond number %q", nsStr.StringCopy())
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}
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for i := 0; i < len("999999999")-nsStr.Len(); i++ {
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nsec *= 10
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}
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}
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return time.Date(year, time.Month(mon), day, hr, min, sec, nsec, loc), nil
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}
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func parseInt(s mem.RO, dst *int) bool {
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if s.Len() == 0 || s.Len() > len("999999999") {
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*dst = 0
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return false
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}
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n := 0
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for i := 0; i < s.Len(); i++ {
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d := s.At(i) - '0'
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if d > 9 {
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*dst = 0
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return false
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}
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n = n*10 + int(d)
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}
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*dst = n
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return true
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}
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// Parse3339 is a wrapper around time.Parse(time.RFC3339Nano, s) that caches
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// timezone Locations for future parses.
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func Parse3339(s string) (time.Time, error) {
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return parse3339m(mem.S(s))
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}
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// Parse3339B is Parse3339 but for byte slices.
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func Parse3339B(b []byte) (time.Time, error) {
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return parse3339m(mem.B(b))
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}
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