time: provide timezone abbreviations on windows

Use http://unicode.org/cldr/data/common/supplemental/windowsZones.xml
to generate the map.

Fixes #4838.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/9997043

src/pkg/time/Makefile

+# Copyright 2013 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+genzabbrs: genzabbrs.go
+	go build genzabbrs.go
+
+windows: genzabbrs
+	./genzabbrs | gofmt >zoneinfo_abbrs_windows.go

src/pkg/time/export_windows_test.go

+// Copyright 2013 The Go 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 time
+
+func ForceAusForTesting() {
+	ResetLocalOnceForTest()
+	localOnce.Do(initAusTestingZone)
+}

src/pkg/time/genzabbrs.go

+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+//
+// usage:
+//
+// go run genzabbrs.go | gofmt > $GOROOT/src/pkg/time/zoneinfo_abbrs_windows.go
+//
+
+package main
+
+import (
+	"encoding/xml"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"sort"
+	"text/template"
+	"time"
+)
+
+// getAbbrs finds timezone abbreviations (standard and daylight saving time)
+// for location l.
+func getAbbrs(l *time.Location) (st, dt string) {
+	t := time.Date(time.Now().Year(), 0, 0, 0, 0, 0, 0, l)
+	abbr1, off1 := t.Zone()
+	for i := 0; i < 12; i++ {
+		t = t.AddDate(0, 1, 0)
+		abbr2, off2 := t.Zone()
+		if abbr1 != abbr2 {
+			if off2-off1 < 0 { // southern hemisphere
+				abbr1, abbr2 = abbr2, abbr1
+			}
+			return abbr1, abbr2
+		}
+	}
+	return abbr1, abbr1
+}
+
+type zone struct {
+	WinName  string
+	UnixName string
+	StTime   string
+	DSTime   string
+}
+
+type zones []*zone
+
+func (zs zones) Len() int           { return len(zs) }
+func (zs zones) Swap(i, j int)      { zs[i], zs[j] = zs[j], zs[i] }
+func (zs zones) Less(i, j int) bool { return zs[i].UnixName < zs[j].UnixName }
+
+const wzURL = "http://unicode.org/cldr/data/common/supplemental/windowsZones.xml"
+
+type MapZone struct {
+	Other     string `xml:"other,attr"`
+	Territory string `xml:"territory,attr"`
+	Type      string `xml:"type,attr"`
+}
+
+type SupplementalData struct {
+	Zones []MapZone `xml:"windowsZones>mapTimezones>mapZone"`
+}
+
+func readWindowsZones() (zones, error) {
+	r, err := http.Get(wzURL)
+	if err != nil {
+		return nil, err
+	}
+	defer r.Body.Close()
+
+	data, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var sd SupplementalData
+	err = xml.Unmarshal(data, &sd)
+	if err != nil {
+		return nil, err
+	}
+	zs := make(zones, 0)
+	for _, z := range sd.Zones {
+		if z.Territory != "001" {
+			// to avoid dups. I don't know why.
+			continue
+		}
+		l, err := time.LoadLocation(z.Type)
+		if err != nil {
+			return nil, err
+		}
+		st, dt := getAbbrs(l)
+		zs = append(zs, &zone{
+			WinName:  z.Other,
+			UnixName: z.Type,
+			StTime:   st,
+			DSTime:   dt,
+		})
+	}
+	return zs, nil
+}
+
+func main() {
+	zs, err := readWindowsZones()
+	if err != nil {
+		log.Fatal(err)
+	}
+	sort.Sort(zs)
+	var v = struct {
+		URL string
+		Zs  zones
+	}{
+		wzURL,
+		zs,
+	}
+	err = template.Must(template.New("prog").Parse(prog)).Execute(os.Stdout, v)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+const prog = `
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// generated by genzabbrs.go from
+// {{.URL}}
+
+package time
+
+type abbr struct {
+	std string
+	dst string
+}
+
+var abbrs = map[string]abbr{
+{{range .Zs}}	"{{.WinName}}": {"{{.StTime}}", "{{.DSTime}}"}, // {{.UnixName}}
+{{end}}}
+
+`

src/pkg/time/zoneinfo_abbrs_windows.go

+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// generated by genzabbrs.go from
+// http://unicode.org/cldr/data/common/supplemental/windowsZones.xml
+
+package time
+
+type abbr struct {
+	std string
+	dst string
+}
+
+var abbrs = map[string]abbr{
+	"Egypt Standard Time":             {"EET", "EET"},    // Africa/Cairo
+	"Morocco Standard Time":           {"WET", "WEST"},   // Africa/Casablanca
+	"South Africa Standard Time":      {"SAST", "SAST"},  // Africa/Johannesburg
+	"W. Central Africa Standard Time": {"WAT", "WAT"},    // Africa/Lagos
+	"E. Africa Standard Time":         {"EAT", "EAT"},    // Africa/Nairobi
+	"Namibia Standard Time":           {"WAT", "WAST"},   // Africa/Windhoek
+	"Alaskan Standard Time":           {"AKST", "AKDT"},  // America/Anchorage
+	"Paraguay Standard Time":          {"PYT", "PYST"},   // America/Asuncion
+	"Bahia Standard Time":             {"BRT", "BRST"},   // America/Bahia
+	"SA Pacific Standard Time":        {"COT", "COT"},    // America/Bogota
+	"Argentina Standard Time":         {"ART", "ART"},    // America/Buenos_Aires
+	"Venezuela Standard Time":         {"VET", "VET"},    // America/Caracas
+	"SA Eastern Standard Time":        {"GFT", "GFT"},    // America/Cayenne
+	"Central Standard Time":           {"CST", "CDT"},    // America/Chicago
+	"Mountain Standard Time (Mexico)": {"MST", "MDT"},    // America/Chihuahua
+	"Central Brazilian Standard Time": {"AMT", "AMST"},   // America/Cuiaba
+	"Mountain Standard Time":          {"MST", "MDT"},    // America/Denver
+	"Greenland Standard Time":         {"WGT", "WGST"},   // America/Godthab
+	"Central America Standard Time":   {"CST", "CST"},    // America/Guatemala
+	"Atlantic Standard Time":          {"AST", "ADT"},    // America/Halifax
+	"US Eastern Standard Time":        {"EST", "EDT"},    // America/Indianapolis
+	"SA Western Standard Time":        {"BOT", "BOT"},    // America/La_Paz
+	"Pacific Standard Time":           {"PST", "PDT"},    // America/Los_Angeles
+	"Central Standard Time (Mexico)":  {"CST", "CDT"},    // America/Mexico_City
+	"Montevideo Standard Time":        {"UYT", "UYST"},   // America/Montevideo
+	"Eastern Standard Time":           {"EST", "EDT"},    // America/New_York
+	"US Mountain Standard Time":       {"MST", "MST"},    // America/Phoenix
+	"Canada Central Standard Time":    {"CST", "CST"},    // America/Regina
+	"Pacific Standard Time (Mexico)":  {"PST", "PDT"},    // America/Santa_Isabel
+	"Pacific SA Standard Time":        {"CLT", "CLST"},   // America/Santiago
+	"E. South America Standard Time":  {"BRT", "BRST"},   // America/Sao_Paulo
+	"Newfoundland Standard Time":      {"NST", "NDT"},    // America/St_Johns
+	"Central Asia Standard Time":      {"ALMT", "ALMT"},  // Asia/Almaty
+	"Jordan Standard Time":            {"EET", "EEST"},   // Asia/Amman
+	"Arabic Standard Time":            {"AST", "AST"},    // Asia/Baghdad
+	"Azerbaijan Standard Time":        {"AZT", "AZST"},   // Asia/Baku
+	"SE Asia Standard Time":           {"ICT", "ICT"},    // Asia/Bangkok
+	"Middle East Standard Time":       {"EET", "EEST"},   // Asia/Beirut
+	"India Standard Time":             {"IST", "IST"},    // Asia/Calcutta
+	"Sri Lanka Standard Time":         {"IST", "IST"},    // Asia/Colombo
+	"Syria Standard Time":             {"EET", "EEST"},   // Asia/Damascus
+	"Bangladesh Standard Time":        {"BDT", "BDT"},    // Asia/Dhaka
+	"Arabian Standard Time":           {"GST", "GST"},    // Asia/Dubai
+	"North Asia East Standard Time":   {"IRKT", "IRKT"},  // Asia/Irkutsk
+	"Israel Standard Time":            {"IST", "IDT"},    // Asia/Jerusalem
+	"Afghanistan Standard Time":       {"AFT", "AFT"},    // Asia/Kabul
+	"Pakistan Standard Time":          {"PKT", "PKT"},    // Asia/Karachi
+	"Nepal Standard Time":             {"NPT", "NPT"},    // Asia/Katmandu
+	"North Asia Standard Time":        {"KRAT", "KRAT"},  // Asia/Krasnoyarsk
+	"Magadan Standard Time":           {"MAGT", "MAGT"},  // Asia/Magadan
+	"E. Europe Standard Time":         {"EET", "EEST"},   // Asia/Nicosia
+	"N. Central Asia Standard Time":   {"NOVT", "NOVT"},  // Asia/Novosibirsk
+	"Myanmar Standard Time":           {"MMT", "MMT"},    // Asia/Rangoon
+	"Arab Standard Time":              {"AST", "AST"},    // Asia/Riyadh
+	"Korea Standard Time":             {"KST", "KST"},    // Asia/Seoul
+	"China Standard Time":             {"CST", "CST"},    // Asia/Shanghai
+	"Singapore Standard Time":         {"SGT", "SGT"},    // Asia/Singapore
+	"Taipei Standard Time":            {"CST", "CST"},    // Asia/Taipei
+	"West Asia Standard Time":         {"UZT", "UZT"},    // Asia/Tashkent
+	"Georgian Standard Time":          {"GET", "GET"},    // Asia/Tbilisi
+	"Iran Standard Time":              {"IRST", "IRDT"},  // Asia/Tehran
+	"Tokyo Standard Time":             {"JST", "JST"},    // Asia/Tokyo
+	"Ulaanbaatar Standard Time":       {"ULAT", "ULAT"},  // Asia/Ulaanbaatar
+	"Vladivostok Standard Time":       {"VLAT", "VLAT"},  // Asia/Vladivostok
+	"Yakutsk Standard Time":           {"YAKT", "YAKT"},  // Asia/Yakutsk
+	"Ekaterinburg Standard Time":      {"YEKT", "YEKT"},  // Asia/Yekaterinburg
+	"Caucasus Standard Time":          {"AMT", "AMT"},    // Asia/Yerevan
+	"Azores Standard Time":            {"AZOT", "AZOST"}, // Atlantic/Azores
+	"Cape Verde Standard Time":        {"CVT", "CVT"},    // Atlantic/Cape_Verde
+	"Greenwich Standard Time":         {"GMT", "GMT"},    // Atlantic/Reykjavik
+	"Cen. Australia Standard Time":    {"CST", "CST"},    // Australia/Adelaide
+	"E. Australia Standard Time":      {"EST", "EST"},    // Australia/Brisbane
+	"AUS Central Standard Time":       {"CST", "CST"},    // Australia/Darwin
+	"Tasmania Standard Time":          {"EST", "EST"},    // Australia/Hobart
+	"W. Australia Standard Time":      {"WST", "WST"},    // Australia/Perth
+	"AUS Eastern Standard Time":       {"EST", "EST"},    // Australia/Sydney
+	"UTC":                            {"GMT", "GMT"},       // Etc/GMT
+	"UTC-11":                         {"GMT+11", "GMT+11"}, // Etc/GMT+11
+	"Dateline Standard Time":         {"GMT+12", "GMT+12"}, // Etc/GMT+12
+	"UTC-02":                         {"GMT+2", "GMT+2"},   // Etc/GMT+2
+	"UTC+12":                         {"GMT-12", "GMT-12"}, // Etc/GMT-12
+	"W. Europe Standard Time":        {"CET", "CEST"},      // Europe/Berlin
+	"GTB Standard Time":              {"EET", "EEST"},      // Europe/Bucharest
+	"Central Europe Standard Time":   {"CET", "CEST"},      // Europe/Budapest
+	"Turkey Standard Time":           {"EET", "EEST"},      // Europe/Istanbul
+	"Kaliningrad Standard Time":      {"FET", "FET"},       // Europe/Kaliningrad
+	"FLE Standard Time":              {"EET", "EEST"},      // Europe/Kiev
+	"GMT Standard Time":              {"GMT", "BST"},       // Europe/London
+	"Russian Standard Time":          {"MSK", "MSK"},       // Europe/Moscow
+	"Romance Standard Time":          {"CET", "CEST"},      // Europe/Paris
+	"Central European Standard Time": {"CET", "CEST"},      // Europe/Warsaw
+	"Mauritius Standard Time":        {"MUT", "MUT"},       // Indian/Mauritius
+	"Samoa Standard Time":            {"WST", "WST"},       // Pacific/Apia
+	"New Zealand Standard Time":      {"NZST", "NZDT"},     // Pacific/Auckland
+	"Fiji Standard Time":             {"FJT", "FJT"},       // Pacific/Fiji
+	"Central Pacific Standard Time":  {"SBT", "SBT"},       // Pacific/Guadalcanal
+	"Hawaiian Standard Time":         {"HST", "HST"},       // Pacific/Honolulu
+	"West Pacific Standard Time":     {"PGT", "PGT"},       // Pacific/Port_Moresby
+	"Tonga Standard Time":            {"TOT", "TOT"},       // Pacific/Tongatapu
+}

src/pkg/time/zoneinfo_windows.go

@@ -16,21 +16,11 @@ import (
 // time zone information.
 // The implementation assumes that this year's rules for daylight savings
 // time apply to all previous and future years as well.
-// Also, time zone abbreviations are unavailable.  The implementation constructs
-// them using the capital letters from a longer time zone description.
-
-// abbrev returns the abbreviation to use for the given zone name.
-func abbrev(name []uint16) string {
-	// name is 'Pacific Standard Time' but we want 'PST'.
-	// Extract just capital letters.  It's not perfect but the
-	// information we need is not available from the kernel.
-	// Because time zone abbreviations are not unique,
-	// Windows refuses to expose them.
-	//
-	// http://social.msdn.microsoft.com/Forums/eu/vclanguage/thread/a87e1d25-fb71-4fe0-ae9c-a9578c9753eb
-	// http://stackoverflow.com/questions/4195948/windows-time-zone-abbreviations-in-asp-net
+
+// extractCAPS exracts capital letters from description desc.
+func extractCAPS(desc string) string {
 	var short []rune
-	for _, c := range name {
+	for _, c := range desc {
 		if 'A' <= c && c <= 'Z' {
 			short = append(short, rune(c))
 		}
@@ -38,6 +28,18 @@ func abbrev(name []uint16) string {
 	return string(short)
 }
 
+// abbrev returns the abbreviations to use for the given zone z.
+func abbrev(z *syscall.Timezoneinformation) (std, dst string) {
+	stdName := syscall.UTF16ToString(z.StandardName[:])
+	a, ok := abbrs[stdName]
+	if !ok {
+		// fallback to using capital letters
+		dstName := syscall.UTF16ToString(z.DaylightName[:])
+		return extractCAPS(stdName), extractCAPS(dstName)
+	}
+	return a.std, a.dst
+}
+
 // pseudoUnix returns the pseudo-Unix time (seconds since Jan 1 1970 *LOCAL TIME*)
 // denoted by the system date+time d in the given year.
 // It is up to the caller to convert this local time into a UTC-based time.
@@ -75,8 +77,10 @@ func initLocalFromTZI(i *syscall.Timezoneinformation) {
 	}
 	l.zone = make([]zone, nzone)
 
+	stdname, dstname := abbrev(i)
+
 	std := &l.zone[0]
-	std.name = abbrev(i.StandardName[0:])
+	std.name = stdname
 	if nzone == 1 {
 		// No daylight savings.
 		std.offset = -int(i.Bias) * 60
@@ -95,7 +99,7 @@ func initLocalFromTZI(i *syscall.Timezoneinformation) {
 	std.offset = -int(i.Bias+i.StandardBias) * 60
 
 	dst := &l.zone[1]
-	dst.name = abbrev(i.DaylightName[0:])
+	dst.name = dstname
 	dst.offset = -int(i.Bias+i.DaylightBias) * 60
 	dst.isDST = true
 
@@ -142,10 +146,27 @@ var usPacific = syscall.Timezoneinformation{
 	DaylightBias: -60,
 }
 
+var aus = syscall.Timezoneinformation{
+	Bias: -10 * 60,
+	StandardName: [32]uint16{
+		'A', 'U', 'S', ' ', 'E', 'a', 's', 't', 'e', 'r', 'n', ' ', 'S', 't', 'a', 'n', 'd', 'a', 'r', 'd', ' ', 'T', 'i', 'm', 'e',
+	},
+	StandardDate: syscall.Systemtime{Month: 4, Day: 1, Hour: 3},
+	DaylightName: [32]uint16{
+		'A', 'U', 'S', ' ', 'E', 'a', 's', 't', 'e', 'r', 'n', ' ', 'D', 'a', 'y', 'l', 'i', 'g', 'h', 't', ' ', 'T', 'i', 'm', 'e',
+	},
+	DaylightDate: syscall.Systemtime{Month: 10, Day: 1, Hour: 2},
+	DaylightBias: -60,
+}
+
 func initTestingZone() {
 	initLocalFromTZI(&usPacific)
 }
 
+func initAusTestingZone() {
+	initLocalFromTZI(&aus)
+}
+
 func initLocal() {
 	var i syscall.Timezoneinformation
 	if _, err := syscall.GetTimeZoneInformation(&i); err != nil {

src/pkg/time/zoneinfo_windows_test.go

+// Copyright 2013 The Go 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 time_test
+
+import (
+	"testing"
+	. "time"
+)
+
+func testZoneAbbr(t *testing.T) {
+	t1 := Now()
+	// discard nsec
+	t1 = Date(t1.Year(), t1.Month(), t1.Day(), t1.Hour(), t1.Minute(), t1.Second(), 0, t1.Location())
+	t2, err := Parse(RFC1123, t1.Format(RFC1123))
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+	if t1 != t2 {
+		t.Fatalf("t1 (%v) is not equal to t2 (%v)", t1, t2)
+	}
+}
+
+func TestLocalZoneAbbr(t *testing.T) {
+	ResetLocalOnceForTest() // reset the Once to trigger the race
+	defer ForceUSPacificForTesting()
+	testZoneAbbr(t)
+}
+
+func TestAusZoneAbbr(t *testing.T) {
+	ForceAusForTesting()
+	defer ForceUSPacificForTesting()
+	testZoneAbbr(t)
+}