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d503dee6f1
Go's time.Parse always allocates a FixedZone for time strings not in UTC (ending in "Z"). This avoids that allocation, at the cost of adding a cache. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
59 lines
1.5 KiB
Go
59 lines
1.5 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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"strings"
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"sync"
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"time"
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)
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// zoneOf returns the RFC3339 zone suffix, or the empty string
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// if it's invalid or not something we want to cache.
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func zoneOf(s string) string {
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if strings.HasSuffix(s, "Z") {
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return ""
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}
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if len(s) < 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 ""
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}
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zone := s[len(s)-len("+08:00"):]
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if c := zone[0]; c == '+' || c == '-' {
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min := zone[len("+08:"):]
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switch min {
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case "00", "15", "30":
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return zone
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}
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}
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return ""
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}
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// locCache maps from zone offset suffix string ("+08:00") =>
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// *time.Location (from FixedLocation).
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var locCache sync.Map
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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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zone := zoneOf(s)
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if zone == "" {
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return time.Parse(time.RFC3339Nano, s)
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}
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loci, ok := locCache.Load(zone)
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if ok {
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// TODO(bradfitz): just rewrite this do the trivial parsing by hand
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// which will be faster than Go's format-driven one. RFC3339 is trivial.
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return time.ParseInLocation(time.RFC3339Nano, s, loci.(*time.Location))
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}
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t, err := time.Parse(time.RFC3339Nano, s)
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if err != nil {
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return time.Time{}, err
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}
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locCache.LoadOrStore(zone, t.Location())
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return t, nil
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}
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